330C_Hyd_Sys-Op

RENR5434 November 2001

Systems Operation 330C Excavator Hydraulic System CYA1-Up (Machine) HAA1-Up (Machine) MCA1-Up (Machine) JAB1-Up (Machine) KDD1-Up (Machine) GAG1-Up (Machine) RBH1-Up (Machine) BTM1-Up (Machine) CAP1-Up (Machine) GKX1-Up (Machine) DKY1-Up (Machine) CGZ1-Up (Machine)

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Important Safety Information Most accidents that involve product operation, maintenance and repair are caused by failure to observe basic safety rules or precautions. An accident can often be avoided by recognizing potentially hazardous situations before an accident occurs. A person must be alert to potential hazards. This person should also have the necessary training, skills and tools to perform these functions properly. Improper operation, lubrication, maintenance or repair of this product can be dangerous and could result in injury or death. Do not operate or perform any lubrication, maintenance or repair on this product, until you have read and understood the operation, lubrication, maintenance and repair information. Safety precautions and warnings are provided in this manual and on the product. If these hazard warnings are not heeded, bodily injury or death could occur to you or to other persons. The hazards are identified by the “Safety Alert Symbol” and followed by a “Signal Word” such as “DANGER”, “WARNING” or “CAUTION”. The Safety Alert “WARNING” label is shown below.

The meaning of this safety alert symbol is as follows: Attention! Become Alert! Your Safety is Involved. The message that appears under the warning explains the hazard and can be either written or pictorially presented. Operations that may cause product damage are identified by “NOTICE” labels on the product and in this publication. Caterpillar cannot anticipate every possible circumstance that might involve a potential hazard. The warnings in this publication and on the product are, therefore, not all inclusive. If a tool, procedure, work method or operating technique that is not specifically recommended by Caterpillar is used, you must satisfy yourself that it is safe for you and for others. You should also ensure that the product will not be damaged or be made unsafe by the operation, lubrication, maintenance or repair procedures that you choose. The information, specifications, and illustrations in this publication are on the basis of information that was available at the time that the publication was written. The specifications, torques, pressures, measurements, adjustments, illustrations, and other items can change at any time. These changes can affect the service that is given to the product. Obtain the complete and most current information before you start any job. Caterpillar dealers have the most current information available. For a list of the most current publication form numbers available, see the Service Manual Contents Microfiche, REG1139F.

When replacement parts are required for this product Caterpillar recommends using Caterpillar replacement parts or parts with equivalent specifications including, but not limited to, physical dimensions, type, strength and material. Failure to heed this warning can lead to premature failures, product damage, personal injury or death.

3 Hydraulic System Table of Contents

Table of Contents

Oil Makeup (Swing System) ............................... 140 Relief Valve (Cushion Crossover) (Anti-Reaction Valves) .............................................................. 141 Swing Drive ........................................................ 148

Systems Operation Section General Information General Information ................................................ 4 Main Hydraulic System ........................................... 4 Electronic Control System ..................................... 9 Pilot System Pilot Hydraulic System .......................................... 10 Gear Pump (Pilot) ................................................. 17 Hydraulic Filter (Pilot) ........................................... 17 Relief Valve (Pilot) ................................................. 18 Accumulator (Pilot) ............................................... 19 Solenoid Valve (Hydraulic Activation) ................... 21 Pilot Valve (Joystick) ............................................. 23 Solenoid Valve (Proportional Reducing) (Power Shift System) ............................................................... 26 Pump System Main Hydraulic Pump ........................................... 28 Pump Control (Main Hydraulic) ............................. 31 Main Control Valve Main Control Valve ............................................... Relief Valve (Main) ................................................ Relief Valve (Line) ................................................. Check Valve (Load) ............................................... Negative Flow Control System ..............................

38 48 50 53 55

Boom System Boom Hydraulic System ....................................... 63 Boom Drift Reduction Valve .................................. 73 Stick System Stick Hydraulic System ......................................... 75 Stick Drift Reduction Valve .................................... 84 Bucket System Bucket Hydraulic System ...................................... 86 Cylinders Cylinders (Boom, Stick and Bucket) ..................... 90 Travel System Travel Hydraulic System ....................................... 91 Pilot Valve (Travel and Steering) ........................... 98 Travel Motor ....................................................... 100 Travel Parking Brake ........................................... 103 Displacement Change Valve .............................. 106 Travel Counterbalance Valve .............................. 109 Oil Makeup (Travel System) ................................ 116 Final Drive .......................................................... 117 Swivel ................................................................ 120 Swing System Swing Hydraulic System ..................................... Swing Motor ....................................................... Pilot Valve (Swing Parking Brake) ....................... Relief Valve (Swing) ............................................

122 132 134 137

Return System Return Hydraulic System .................................... 151 Check Valve (Return Makeup) (Slow Return Check Valve) ................................................................ 152 Bypass Valve (Return) (Bypass Check Valve) .... 153 Hydraulic Tank and Filter ................................... 155 Oil Filter (Return) (Case Drain Filter) .................. 156 Hydraulic Oil Cooler ........................................... 156 Gear Pump (Fan Motor) ...................................... 156 Reference Graphic Color Codes .......................................... 157

Index Section Index ................................................................... 160

4 Hydraulic System Systems Operation Section

Systems Operation Section General Information i01584866

General Information SMCS Code: 4000; 4250; 4265; 4284; 4300; 4801; 5050 Reference: For testing and adjusting of the hydraulic system, refer to Testing and Adjusting, “Excavator Hydraulic System” for your machine. Reference: For systems operation of the electronic control unit and electronic system, refer to Systems Operation/Testing and Adjusting, “Excavator Engine and Pump Control” for your machine. Reference: For more information on specifications with illustrations, refer to Specifications, “Excavator Machine System Specifications” for your machine. Reference: For more information on the hydraulic schematics, refer to Schematic, “Excavator Hydraulic System” for your machine. Reference: For more information on electrical schematics, refer to Schematic, “Excavator Electrical System” for your machine. i01630597

Main Hydraulic System SMCS Code: 5050; 5051; 5069; 5117; 5472

Main Hydraulic Schematic



Illustration 1

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7 Hydraulic System Systems Operation Section (1) Swing motor (2) Left travel motor (3) Right travel motor (4) Stick cylinder (5) Travel brake valve (left) (6) Travel brake valve (right) (7) Bucket cylinder (8) Boom cylinder (9) Swivel (10) Pilot control valve (travel) (11) Stick drift reduction valve (12) Main control valve (13) Boom drift reduction valve (14) Pressure switch (15) Pressure switch (16) Pilot control valve (swing and stick) (17) Pilot control valve (boom and bucket) (18) Main relief valve (19) Pressure switch (20) Accumulator (21) Reducing valve (boom priority mode or swing priority mode) (22) Pressure sensor (drive pump) (23) Swing parking brake solenoid valve (24) Valve (25) Solenoid valve (hydraulic activation) (26) Drive pump (view from shaft end) (27) Travel speed solenoid valve (28) Pilot oil manifold (29) Drain filter (30) Pilot relief valve (31) Pilot filter (32) Idler pump (view from shaft end) (33) Pilot pump (34) Slow return check valve (35) Bypass check valve (36) Pressure sensor (idler pump) (37) Proportional reducing valve (power shift pressure) (38) Oil cooler (39) Return filter (40) Hydraulic tank (41) Gear pump (fan motor) (42) Relief valve (fan pump) (43) Fan motor (hydraulic oil cooler)

Hydraulic Pump Flow and Pressure Control System

This machine is driven and controlled by the following systems.

• The main hydraulic system controls the cylinders, the travel motors and the swing motor.

• The pilot hydraulic system supplies oil to the main pumps, the main control valve, the swing brake and the travel motors.

• The electronic control system controls the outputs of the engine and pump.

• The hydraulic oil cooling system provides oil to the fan motor in order to cool the hydraulic oil. The main hydraulic system delivers oil flow from idler pump (32) and drive pump (26) in order to control the following components: bucket cylinder (7), stick cylinder (4), boom cylinders (8), right travel motor (3), left travel motor (2), and swing motor (1).

Illustration 3

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Main control valve (18) Main relief valve (45) Right control valve body (46) Left control valve body

Idler pump (32) and drive pump (26) are bent axial piston type pumps. The performance of both pumps is equal.

Illustration 2 Pump compartment (26) Drive pump (32) Idler pump (37) Proportional reducing valve (power shift pressure) (44) Delivery line (idler pump) (45) Delivery line (drive pump)

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Drive pump (26) is directly connected to the engine by a flexible coupling. The drive pump delivers oil to the left control valve body (46) of the main control valve. Idler pump (32) is mechanically connected to the drive pump through gears. The idler pump delivers oil to the right control valve body (45) of the main control valve. Gear type pilot pump (33) supplies oil to the pilot hydraulic system. Gear type pilot pump (33) is mechanically connected to idler pump (32) through gears. Gear type fan pump (41) supplies oil to the oil cooling system. Gear pump (41) is mechanically connected to the engine through gears. All engine output is used to drive these three pumps.

8 Hydraulic System Systems Operation Section As the load pressure increases during working conditions, the main pumps increase the delivery pressure and the pumps decrease the flow rate. The hydraulic horsepower remains constant even though the delivery pressure and the flow rates change. The hydraulic horsepower is approximately identical to the engine horsepower. When no work is being performed, pump oil flows through main control valve (12) and into hydraulic tank (40). The main control valve sends a negative flow control signal to each main pump regulator in order to destroke the pump to the minimum output flow. If an operation is being performed, main control valve (12) directs pump oil to the respective cylinders (boom, bucket, and stick) and/or motors (swing and travel). Main control valve (12) contains numerous valve stems, passages, check valves, and orifices in order to carry out a single operation or a combined operation. The working pressure of the main hydraulic system is regulated by main relief valve (18).

Illustration 4

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Cab (47) Monitor panel (48) Joystick (stick and swing) (49) Joystick (boom and bucket) (50) Left travel lever/pedal (51) Right travel lever/pedal (52) Engine speed dial

When joystick (48), joystick (49), left travel lever/pedal (50) and/or right travel lever/pedal (51) are moved from the NEUTRAL position, the pilot oil flows through the pilot control valves to the corresponding spools at the main control valve (12). The pilot pressure oil at that end of the valve spool forces the valve spool to shift. The pilot oil on the other end of the valve spool drains to the hydraulic tank. When the valve spool shifts, oil is then delivered from idler pump (32) or drive pump (26) to the cylinders and motors. Thus, pilot oil drives each system of the main control valve. 2. The pilot hydraulic system controls the output flow of the main pumps. During machine operation, pilot pressure is sent to the main pump regulators as a signal pressure. This signal pressure is called power shift pressure. The engine and pump controller receives input signals from various components on the machine. The engine and pump controller processes the input signals. The engine and pump controller then sends an electrical signal to proportional reducing valve (37) at the idler pump regulator in order to regulate the power shift pressure. The power shift pressure controls the output flow of idler pump (32) and drive pump (26). Power shift pressure adjusts the output flow of the main pumps in accordance with the engine speed. For more information concerning power shift pressure, refer to Systems Operation, “Pilot Hydraulic System”. 3. The pilot hydraulic system generates signal pressure in order to perform the following operations. a. Pilot signal pressure activates the Automatic Engine Speed Control (AEC) system. This causes functions to automatically reduce the engine speed when no hydraulic operation is called for.

The pilot hydraulic system receives oil flow from pilot pump (33). The pilot hydraulic system controls the following functions.

b. Pilot signal pressure releases the swing parking brake.

1. The pilot hydraulic system controls the operation of the implement control valves.

c. Pilot signal pressure will automatically change the travel speed to either HIGH or LOW in accordance with the hydraulic system load.

Pilot oil flows from pilot pump (33) through pilot manifold (28). The pilot oil then flows to the pilot control valves for machine operation (implement operations, swing operations and travel operation). These pilot control valves are activated by the joysticks and the travel levers/pedals.

d. Pilot signal pressure operates the straight travel control valve. This maintains straight travel during the operation of an implement.

9 Hydraulic System Systems Operation Section e. Pilot signal pressure controls the operation of the valves that can be used during a loading operation or a trenching operation. For more information concerning the pilot hydraulic system, refer to Systems Operation, “Pilot Hydraulic System”. i01638098

Electronic Control System SMCS Code: 1900

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Illustration 5 (1) Engine and pump controller (2) Fuse panel (3) Engine (4) Engine speed sensor (5) Main pumps (6) Governor lever (7) Engine start switch (8) Battery (9) Backup switch (10) Governor actuator (11) Feedback sensor (12) Monitor (13) Action alarm (14) Engine speed dial (15) Switch panel

(16) Engine coolant temperature sensor (17) Hydraulic oil temperature sensor (18) Alternator (19) Fuel level sensor (20) Engine oil pressure sensor (21) Manual low idle switch (22) Engine oil level switch (23) Hydraulic oil level switch (24) Water separator (25) Implement/swing pressure switch (26) Right travel pressure switch (27) Left travel pressure switch (28) Straight travel pressure switch (29) Pressure sensor (idler pump) (30) Pressure sensor (drive pump)

(31) Power shift solenoid (32) Straight travel solenoid (33) Travel speed solenoid (34) Swing parking brake solenoid valve (35) Travel alarm (36) Restricted air filter switch (37) Restricted hydraulic return filter indicator (38) Air heater indicator (39) Engine coolant level switch (40) Pressure switch (attachment pump) (41) Attachment pedal pressure switch (1) (42) Attachment pedal pressure switch (2) (43) Proportional reducing valve for auxiliary hydraulics


• The electronic control system controls the output

flow rate of the main pumps. The engine and pump controller sends an electrical signal to the power shift solenoid that is based on engine speed and the position of the engine speed dial. This allows the main pumps to supply the optimum output that matches the hydraulic load to the machine and the engine speed. When a large load is placed on the machine, the system allows the pumps to destroke. The system utilizes the available maximum engine horsepower.

• The electronic control system controls the engine Illustration 6

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(1) Engine and pump controller

speed. This is called Automatic Engine Speed Control (AEC). When there is a very small load condition or no load condition, the system automatically decreases the engine speed. The AEC system is designed to reduce fuel consumption and noise.

• The electronic control system controls various components of the machine hydraulic systems. The engine and pump controller sends output signals to the swing parking brake solenoid valve, the travel speed solenoid valve and the straight travel solenoid.

Illustration 7

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Note: If a problem occurs in the electronic control system, temporary operation of the machine is possible by use of the backup switches that are located in the cab. For more information concerning the backup system, refer to Operation and Maintenance Manual, “Backup Controls”.

(12) Monitor

The electronic control system consists of monitor (12) in the cab and the engine and pump controller (1) that is located in the compartment behind the cab. The electronic control system controls the engine speed and the pumps through the engine and pump controller. Engine and pump controller (1) receives input signals from various components on the machine. The engine and pump controller continuously monitors the input signals in order to control the output flow rate of the main pumps, engine speed and various components of the machine hydraulic systems. The electronic control system has the following three major functions.

Reference: For more information concerning the operation of the electronic control system, refer to Systems Operation/Testing and Adjusting, “Engine and Pump Electronic Control System”.

Pilot System i01630521

Pilot Hydraulic System SMCS Code: 5050-PS



Illustration 8

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13 Hydraulic System Systems Operation Section (1) Swing parking brake (2) Displacement change valve (left travel motor) (3) Displacement change valve (right travel motor) (4) Line (pilot oil from swing parking brake solenoid valve) (5) Travel pilot control valve (6) Pilot line (BOOM LOWER) (7) Pilot line (boom drift reduction valve) (8) Pilot line (STICK IN) (9) Pilot line (stick drift reduction valve) (10) Stick drift reduction valve (11) Main control valve (12) Boom drift reduction valve (13) Solenoid valve (straight travel) (14) Pilot line (pilot pressure to left travel pressure switch) (15) Pilot line (pilot oil to travel pilot control valve) (16) Right travel control valve (17) Boom I control valve (18) Straight travel control valve (19) Travel pressure switch (left) (20) Pilot line (pilot pressure to right travel pressure switch) (21) Travel pressure switch (right) (22) Pilot line (pilot oil to pilot control valve for stick and swing) (23) Pilot line (pilot oil to pilot control valve for boom and bucket) (24) Left travel control valve (25) Pilot control valve for stick and swing (26) Pilot control valve for boom and bucket (27) Variable swing priority valve (28) Pilot line (STICK OUT) (29) Pilot line (STICK IN) (30) Pilot line (SWING RIGHT) (31) Pilot line (SWING LEFT) (32) Pilot line (BUCKET CLOSE) (33) Pilot line (BOOM RAISE) (34) Pilot line (BOOM LOWER) (35) Pilot line (BUCKET OPEN) (36) Pilot line (pilot oil from boom pilot control valve) (37) Pilot line (BOOM RAISE) (38) Pilot line (pilot oil to the pressure reducing valve for boom priority) (39) Pilot line (pilot pressure to implement/swing pressure switch) (40) Implement/swing pressure switch (41) Pilot line (pilot pressure to displacement change valves) (42) Pilot line (pilot oil to pressure reducing valve for swing priority) (43) Pilot line (pilot oil to pilot control valves) (44) Pilot line (pilot oil to straight travel control valve) (45) Swing parking brake solenoid valve (46) Valve (hydraulic activation) (47) Pressure reducing valve for swing priority (48) Pressure reducing valve for boom priority (49) Drive pump (50) Passage (power shift pressure) (51) Pilot manifold (52) Travel speed solenoid valve (53) Passage (54) Hydraulic activation solenoid valve (55) Passage (56) Passage (57) Passage (58) Idler pump (59) Pilot pump (60) Pilot line (pilot oil flow to pilot oil manifold) (61) Pilot filter (62) Passage (power shift pressure) (63) Proportional reducing valve (power shift pressure) (64) Pilot relief valve (65) Passage (66) Pilot line (pilot oil flow from pilot pump to pilot oil filter) (67) Pilot line (pilot oil flow to pump regulators)


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Illustration 9 Ports and solenoids at pilot manifold (45) Swing parking brake solenoid valve (46) Valve (hydraulic activation)

(52) Travel speed solenoid valve (54) Hydraulic activation solenoid valve

Pilot Oil Circuit

• Straight travel valve circuit

The pilot circuit pressure is limited by pilot relief valve (64).

• Swing parking brake • Boom priority

The oil delivery from pilot pump (59) performs the following main functions.

• Swing priority

• Create pilot oil pressure in order to control the

• Automatic travel speed change

output flows of the main pumps.

• Provide pilot oil pressure to the pilot control valves for implements, swing and travel in order to perform machine operations.

• Create pilot oil pressure in order to automatically operate the control devices.

The pilot circuit is classified into the following circuits and each circuit performs one of the above functions.

• Power shift pressure system • Pilot control valve circuit • Pressure switch circuits


Power Shift Pressure System

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Illustration 10 (49) Drive pump (58) Idler pump (63) Proportional reducing valve (PS pressure) (59) Pilot pump

(68) Engine and pump controller (69) Monitor (70) Engine speed dial (71) Idler pump pressure sensor (72) Drive pump pressure sensor

During machine operation, engine and pump controller (68) receives input signals from the following components:

• Engine speed dial (70) • Engine speed sensor (75) that is located on the flywheel housing

• Idler pump pressure sensor (71) • Drive pump pressure sensor (72) • Monitor in the cab (69) • Feedback sensor (73) at governor actuator (74) The engine and pump controller (68) continually monitors all of the input signals. The input signals are processed by the engine and pump controller and an output signal is sent to proportional reducing valve (63) at the pump regulator. The proportional reducing valve assists in controlling the output flow of idler pump (58) and drive pump (49).

(73) Feedback sensor (74) Governor actuator (75) Engine speed sensor (flywheel housing)

The oil delivery from pilot pump (59) flows through the pilot filter to proportional reducing valve (63) at the pump regulator. The electrical signal that is sent from engine and pump controller (68) causes proportional reducing valve (63) to regulate the pilot pressure to a reduced pressure. This reduced pressure is called power shift pressure (PS). The proportional reducing valve sends the reduced pilot oil pressure through the idler pump regulator and through the drive pump regulator. The output flow of idler pump (58) and drive pump (49) is controlled in accordance with the power shift pressure. The power shift pressure is used to regulate the maximum allowable hydraulic pump output. The output signal that is sent from the engine and pump controller to the proportional reducing valve will change when the engine and pump controller detects a change in any of the input signals. The power shift pressure that is sent to the regulators at the idler pump and the drive pump will change in order to regulate the maximum allowable hydraulic pump output. The desired engine speed is maintained.

16 Hydraulic System Systems Operation Section A decrease in engine speed increases the power shift pressure. An increase in power shift pressure causes destroke condition of the idler pump and the drive pump. The maximum allowable hydraulic power output is decreased. An increase in engine speed decreases the power shift pressure. A decrease in power shift pressure causes an upstroke condition of the idler pump and the drive pump. The maximum allowable hydraulic power output is increased. Note: For more information concerning the operation of the engine and pump controller, refer to Systems Operation/Testing and Adjusting, “Engine and Pump Electronic Control System”.

Pilot Control Valve Circuits Oil from pilot pump (59) flows through pilot line (66), pilot filter (61) and pilot line (60) to pilot manifold (51). When the hydraulic activation control lever is shifted to the UNLOCKED position, the engine and pump controller energizes the hydraulic activation solenoid valve (54). The pilot oil then shifts valve (46). The pilot oil now flows through valve (46) and pilot line (43). The pilot oil now flows to pilot control valves (5), (25) and (26) for implements, swing and travel in order to perform machine operations. When the joysticks and/or travel levers/pedals are moved, the pilot oil flows to main control valve (11) in order to control the machine functions. The following example is given for the BOOM LOWER operation and the BOOM RAISE operation. Machine operations for a stick operation, bucket operation, travel operation and swing operation are accomplished in the same manner as the boom operation. When the joystick for the boom is moved to the BOOM RAISE position, pilot oil from pilot control valve (26) flows through pilot line (37) to boom I control valve (17). The pilot pressure shifts the boom I control valve. The oil delivery from the idler pump flows to the head end of the boom cylinders in order to perform the BOOM RAISE operation. When the joystick for the boom is moved to the BOOM LOWER position, pilot oil from pilot control valve (26) flows through pilot line (6) to boom I control valve (17). The pilot pressure shifts the boom I control valve. The pilot oil also flows through pilot line (7) in order to open boom drift reduction valve (12). The return oil from the head end of the boom cylinders flows through the boom drift reduction valve and the boom I control valve to the hydraulic tank. The BOOM LOWER operation is now performed.

Pressure Switch Circuits Pressure switches (19) and (21) are connected to travel pilot control valve (5). Pressure switch (40) is connected to pilot control valve (25) and pilot control valve (26). When all of the joysticks and/or travel levers/pedals are in the NEUTRAL position, the pilot oil pressure to the pressure switches is low. Pressure switches (19), (21) and (40) are OFF. The engine and pump controller recognizes the OFF condition of all of the pressure switches. The AEC system is activated in order to lower the engine rpm. If any of the joysticks and/or travel levers/pedals are moved from the NEUTRAL position, the increased pilot oil pressure is sent to the pressure switches. If pressure switch (19), (21) and/or (40) is ON, the engine and pump controller activates the AEC system in order to increase the engine rpm.

Straight Travel Valve Circuit When a swing operation and/or implement operation is performed during a travel operation, the increase of pilot pressure in pilot line (39) activates implement/swing pressure switch (40). The implement/swing pressure switch sends an electrical signal to the engine and pump controller. The engine and pump controller energizes straight travel solenoid (13). Pilot pressure now activates straight travel control valve (18). The straight travel control valve maintains straight travel even though there is a swing operation or an implement operation during travel. For more information concerning the operation of the straight travel control valve, refer to Systems Operation, “Control Valve (Straight Travel)”.

Swing Parking Brake When the hydraulic activation control lever is placed in the UNLOCKED position, pilot oil in passage (57) flows through valve (46) and passage (53) to swing parking brake solenoid valve (45). When any of the joysticks are moved from the NEUTRAL position, the increase of pilot pressure in pilot line (39) activates implement/swing pressure switch (40). The implement/swing pressure switch sends an electrical signal to the engine and pump controller. An electrical signal from the engine and pump controller energizes the swing parking brake solenoid valve (45). Pilot oil in line (4) flows to swing parking brake (1). This oil releases the swing parking brakes. For more information concerning the operation of the swing parking brake, refer to Systems Operation, “Pilot Valve (Swing Parking Brake)”.


Boom Priority During combined operations of BOOM RAISE and STICK IN, the pilot oil pressure in pilot line (36) and pilot line (38) activates the pressure reducing valve for boom priority. The pressure reducing valve for boom priority allows priority flow to the head end of the boom cylinders during these combined hydraulic operations by disabling the stick II control valve. For more information concerning the pressure reducing valve for boom priority, refer to Systems Operation, “Boom Hydraulic System”.

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Gear Pump (Pilot) SMCS Code: 5073; 5085

Swing Priority During a swing operation, pilot oil flows from pilot control valve (25) to the pressure reducing valve for swing priority (47). The pressure reducing valve for swing priority shifts. The pilot oil flow in pilot line (42) from pilot oil manifold (51) is blocked by the pressure reducing valve for swing priority. Most of the drive pump delivery flow goes to the swing motor. For more information concerning the pressure reducing valve for swing priority, refer to Systems Operation, “Swing Hydraulic System”.

Automatic Travel Speed Change Valve Pilot oil in passage (56) flows to travel speed solenoid valve (52). When the travel speed switch on the right console is set at the HIGH SPEED position, the travel speed solenoid valve opens. This allows pilot oil to flow through travel speed solenoid valve (52) and through line (41). The oil then flows to the displacement change valve for the left travel motor (2) and the displacement change valve for the right travel motor (3). As the displacement change valve operates, the travel speed is maintained at the HIGH SPEED position.

Illustration 11

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Pilot pump

The pilot pump is a gear type pump that supplies oil flow to the pilot system. The pilot pump is located inside the main pump housing. The pilot pump is mechanically connected to the drive pump. The pump delivery rate with load is approximately 34 L/min (9.0 US gpm). i01630709

Hydraulic Filter (Pilot) SMCS Code: 5068; 5092

When the travel speed switch on the right console is set at the HIGH SPEED position, the pressure sensors for the pump delivery pressure control the travel speed in accordance with the travel load. For example, low speed during a high load condition and high speed during a low load condition. For more information concerning the operation of the displacement change valves, refer to Systems Operation, “Displacement Change Valve”.

Illustration 12

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(1) Pilot oil filter

The oil delivery from the pilot pump flows through pilot oil filter (1) and into the components in the pilot system.

18 Hydraulic System Systems Operation Section i01630729

Relief Valve (Pilot) SMCS Code: 5072

Illustration 14 (1) (2) (3) (4)

Illustration 13

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(1) Pilot oil filter (2) Filter element (3) Bypass relief valve

Filter element (2) in pilot oil filter (1) removes contaminants from the pilot oil. If the pilot oil is extremely cold or if the flow of pilot oil through filter element (2) becomes restricted by contaminants, the oil bypasses filter element (2) through bypass relief valve (3). Bypass relief valve (3) is built into the base for the pilot oil filter.

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Inlet port (oil flow from pilot pump) Pilot relief valve Port (oil flow to hydraulic tank) Outlet lines (regulated pilot oil pressure)

Pilot relief valve (2) is located on the mounting base for the pilot oil filter. The pilot relief valve limits the pressure in the pilot system. The pilot relief valve setting is adjustable. The pilot oil flows from the pilot pump to inlet port (1). When the pressure in the pilot oil system reaches the pressure setting of pilot relief valve (2), part of the pilot oil flow is returned to the hydraulic tank through port (3). The pressure of the pilot system oil in outlet lines (4) is equal to the pressure setting of the pilot relief valve. Reference: For more information concerning the pilot relief valve setting, refer to Testing and Adjusting, “Relief Valve (Pilot) - Test and Adjust”.


Accumulator (Pilot) SMCS Code: 5077

Illustration 15

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(5) Accumulator (16) Line (pilot oil from pilot oil manifold) (17) Mounting block

The accumulator stores pilot pressure oil for use at the main control valves. During some operations, the pilot system needs more oil because there is insufficient flow from the pilot pump. Accumulator (5) will provide pilot pressure oil to the pilot system when the pilot pump flow is inadequate. Insufficient supply of pilot oil flow to the pilot system may be caused by the following two reasons:

• Implements are lowered while the engine is stopped and oil supply to the main control valves is stopped.

• Combined operations


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Illustration 16 Accumulator (5) Accumulator (16) Line (pilot oil flow from pilot oil manifold to the mounting block for the accumulator) (17) Mounting block (18) Passage

(19) Inlet port (20) Pressure oil chamber (21) Vessel (22) Bladder (23) Gas chamber (24) Passage

Pilot oil from the pilot filter enters inlet port (27) of the pilot oil manifold. Pilot oil flows through passage (28) and opens check valve (29). Pilot oil now flows through passages (24) and (26) to the pilot control valves (joysticks and travel levers/pedals). The pilot oil also flows through passage (25) and line (16) to the mounting block for the accumulator. The pilot oil now flows through passage (18) and inlet port (19) into pressure oil chamber (20). The pilot oil acts against bladder (22) and the nitrogen gas in gas chamber (23) is compressed. Check valve (29) prevents a backflow of the stored oil in the accumulator. The stored oil is used for solely operating the stems of the main control valve.

(25) Passage (26) Passage (27) Inlet port (pilot oil manifold) (28) Passage (29) Check valve


Solenoid Valve (Hydraulic Activation) SMCS Code: 5479

Illustration 20 (3) (4) (5) (6)

Illustration 17

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Hydraulic activation control lever Limit switch Plunger Box

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Pilot oil manifold (1) Pilot oil manifold (2) Hydraulic activation solenoid valve

Illustration 21

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Cab (bottom view) (6) Box

Illustration 18

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Cab

Limit switch (4) and plunger (5) are contained in box (6). The limit switch is activated by hydraulic activation control lever (3). When hydraulic activation control lever (3) is shifted to the LOCKED position, solenoid valve (2) of pilot oil manifold (1) is not energized. Pilot oil is not supplied to the pilot control valves. Thus when the joysticks and/or the travel levers/pedals are operated, the cylinders or the motors are not activated.

(3) Hydraulic activation control lever (LOCKED position)

The engine will not start unless hydraulic activation control lever (3) is in the LOCKED position. If some one unexpectedly operates the machine, the machine will not operate.

Illustration 19

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Cab (3) Hydraulic activation control lever (UNLOCKED position)

When hydraulic activation control lever (3) is placed in the UNLOCKED position, solenoid valve (2) is energized and pilot oil passes through the solenoid valve. Pilot oil now flows to the pilot control valves.


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Illustration 22 Partial diagram of solenoid valve (hydraulic activation) (UNLOCKED circuit) (2) Hydraulic activation solenoid valve (7) Solenoid (8) Spring (9) Spool (10) Control valve (11) Passage

(12) Passage (13) Passage (14) Passage (return oil) (15) Passage (pilot oil to swing parking brake solenoid valve) (16) Swing parking brake solenoid valve

When hydraulic activation control lever (3) is placed in the UNLOCKED position, plunger (5) of limit switch (4) is depressed by control lever (3). Limit switch (4) is in the ON state.

(17) Pilot oil flow to pilot valves (joysticks) (18) Valve (hydraulic activation) (19) Passage

The hydraulic activation solenoid valve (2) consists of solenoid (7) and control valve (10). When hydraulic activation control lever (3) is in the UNLOCKED position, solenoid (7) controls valve (10). When solenoid (7) is energized, spool (9) moves in a downward direction against the force of spring (8). Passage (12) opens. Pilot pressure oil from passage (13) flows through passage (11) to valve (18). The spool in valve (18) moves in a downward direction. Pilot pressure oil in passage (19) flows through valve (18). Pilot oil is now delivered through passage (15) to swing parking brake solenoid valve (16). Pilot pressure oil in passage (19) is also delivered to the pilot control valves (joysticks and travel levers/pedals) through line (17).


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Illustration 23 Partial drawing of solenoid valve (hydraulic activation) (LOCKED position) (1) Hydraulic activation solenoid valve (7) Solenoid (8) Spring

(9) Spool (11) Passage (12) Passage

When hydraulic activation control lever (3) is moved to the LOCKED position, plunger (5) of limit switch (4) is not depressed by control lever (3). Limit switch (4) is in the OFF state.

(13) Passage (14) Passage (return oil) (20) Passage i01579519

Pilot Valve (Joystick) SMCS Code: 5705-V4

When hydraulic activation control lever (3) is in the LOCKED position, solenoid (7) is not energized. Spool (9) is forced upward by spring (8). Passage (20) opens and passage (12) closes. Passage (13) is not open to passage (11). Pilot oil supply to line (17) is stopped. Pilot oil supply to the pilot control valves (joysticks and travel levers/pedals) is blocked. The cylinders and the motors can not be activated.

Illustration 24 Cab (1) Joystick (stick and swing) (2) Joystick (boom and bucket)

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Illustration 25 Pilot lines at the main control valve (top view)

When joystick (1) and/or joystick (2) are operated, the pilot control valves send pilot pump oil through the pilot lines to pilot ports at the main control valve in order to shift the spools in the main control valve. Refer to Illustration 25 and Table 1 for the location of the pilot lines and machine operations. Table 1

Machine Operation

Pilot line

Control Valve

(3)

Boom I control valve

BOOM LOWER

(4)

Bucket control valve

BUCKET CLOSE

(5)

Swing control valve

SWING LEFT

(6)

Boom II control valve

BOOM RAISE

(7)

Stick II control valve

STICK IN

(8)

Right travel control valve

REVERSE RIGHT TRAVEL

(9)

Left travel control valve

REVERSE LEFT TRAVEL

(10)

Stick I control valve

STICK IN

Pilot oil from the pilot control valves flows through pilot lines to the ports on the bottom of the main control valve in order to perform the opposite operation.


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Illustration 26 Pilot control valve (stick and swing) (1) (2) (3) (4) (5) (6) (7)

Joystick Rod Return passage Passage Spool Plate Rod

(8) Spring (9) Seat (10) Seat (11) Spring (12) Spring (13) Return chamber (14) Return passage

When joystick (1) is moved to the right, plate (6) tilts to the right. Plate (6) pushes down on rod (7). Seat (10) moves down against the force of metering spring (11) and spring (12). The force of metering spring (11) shifts spool (16) downward. Passage (15) opens. The pilot oil flows through passage (20), passage (18), passage (15) and port (19) to the main control valve. The pilot oil pressure shifts the spool of the main control valve. This enables the implement operation or swing operation. The return pilot oil at the opposite end of the spool in the main control valve returns to the pilot control valve through port (17). Since rod (2) is not pushed down by plate (6), return passage (3) is open and passage (4) is closed. The return pilot oil flows through return passage (3), return chamber (13) and port (21) to the hydraulic tank.

(15) Passage (16) Spool (17) Port (return pressure to valve) (18) Passage (pilot supply pressure) (19) Port (reduced pressure to valve) (20) Port (pilot supply) (21) Port (tank)

The force of metering spring (11) varies with the position of the joystick. Since spool (16) is moved by the force of metering spring (11), the pilot oil pressure that flows through passage (15) to the main control valve directly corresponds with the position of the joystick. Spool modulation in the main control valve directly corresponds with the amount of movement of the joystick.

26 Hydraulic System Systems Operation Section When the joystick is moved slightly from the NEUTRAL position, metering spring (11) moves spool (16) slightly. Low pilot oil pressure is sent to the spool of the main control valve. The main control valve spool shifts a slight amount. The volume of oil delivery to the cylinders and/or motors is small. The speed of the cylinders and/or motors is slow. As the joystick is moved farther from the NEUTRAL position, the force of metering spring (11) on spool (16) increases. The pilot oil pressure that is sent to the main control valve increases. The spool in the main control valve shifts farther and the speed of the cylinders and/or motors increases. Thus, cylinder speed and motor speed is controlled by the amount of movement and the position of the joystick. When the joystick is moved slightly from the NEUTRAL position, only metering spring (11) acts on spool (16). Fine control of the cylinders and/or motors is accomplished since the pilot oil pressure that is sent to the main control valve is decreased. As the joystick is moved farther from the NEUTRAL position, the bottom of rod (7) comes in contact with spring (8). Now, the combined force of metering spring (11) and spring (8) act on spool (16). The pilot oil pressure increases rapidly. The cylinders and/or motors respond more rapidly.

The proportional reducing valve for the power shift pressure is located on the main pump housing. The proportional reducing valve is a solenoid operated control valve. The proportional reducing valve receives supply oil from the pilot pump. The solenoid receives a pulse width modulated signal (PWM signal) from the engine and pump controller. The PWM signal that is sent from the engine and pump controller causes the proportional reducing valve to regulate the pilot pressure to a reduced pressure. This reduced pressure is called power shift pressure (PS). The proportional reducing valve sends the reduced pilot oil pressure to the regulators at the idler pump and the drive pump. The output flow of the idler pump and the drive pump is controlled in accordance with the power shift pressure. The power shift pressure is used to control the maximum allowable hydraulic pump output.

When the joystick is released, the joystick will return to the NEUTRAL position due to the force of spring (12). i01630751

Solenoid Valve (Proportional Reducing) (Power Shift System) SMCS Code: 5479

Illustration 28

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Proportional reducing valve (increase in PWM signal)

Illustration 27 Proportional reducing valve (power shift solenoid) (1) Solenoid (3) Body (main pump) (9) Line (pilot oil flow)

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(1) Solenoid (2) Spring (3) Valve body (4) Spool (5) Passage (return oil flow) (6) Passage (power shift pressure to pump regulators) (7) Spool chamber (8) Passage (pilot oil flow)

A decrease in engine speed causes an increase in power shift pressure and a decrease in pump flow.

27 Hydraulic System Systems Operation Section While the engine is operating, the engine and pump controller senses a decrease in engine speed. A decrease in engine speed causes the engine and pump controller to increase the PWM signal that is sent to solenoid (1). The magnetic force of the solenoid increases. As the magnetic force of the solenoid becomes greater than the force of spring (2), spool (3) moves in a downward direction against the force of the spring. The downward movement of spool (3) blocks the flow of oil from passage (6) to passage (5). Pilot oil in line (9) now flows through passage (8), into spool chamber (7) and into passage (6) at a reduced pressure (power shift pressure). The increased power shift pressure in passage (6) acts on the idler pump regulator and the drive pump regulator. The idler pump and the drive pump destroke as a result of an increase in power shift pressure.

While the engine is operating, the engine and pump controller senses an increase in engine speed. An increase in engine speed causes the engine and pump controller to decrease the PWM signal that is sent to solenoid (1). The magnetic force of the solenoid decreases. As the force of spring (2) becomes greater than the magnetic force of the solenoid, spool (3) moves in an upward direction. The upward movement of spool (3) blocks the flow of pilot oil from passage (8). Power shift pressure oil in passage (6) now drains into spool chamber (7) and into passage (5). The decreased power shift pressure in passage (6) that is acting on the idler pump regulator and the drive pump regulator causes the idler pump and the drive pump to move to an upstroke position. The idler pump and the drive pump upstroke as a result of a decrease in power shift pressure. Reference: For more information concerning power shift pressure (PS), refer to Systems Operation, “Pilot Hydraulic System”.

Illustration 29

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Proportional reducing valve (decrease in PWM signal) (1) Solenoid (2) Spring (3) Valve body (4) Spool (5) Passage (return oil flow) (6) Passage (power shift pressure to pump regulators) (7) Spool chamber (8) Passage (pilot oil flow)

An increase in engine speed causes a decrease in power shift pressure and an increase in pump flow.


Pump System i01638366

Main Hydraulic Pump SMCS Code: 5070-MV

Construction

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Illustration 30 Main pumps (1) Port (negative flow control pressure) (2) Outlet port (pilot pump) (3) Idler pump (4) Outlet port (idler pump)

(5) Inlet port (6) Port (power shift pressure) (7) Port (negative flow control pressure) (8) Drive pump

The main pumps consist of idler pump (3) and drive pump (8). The main pumps and the port block are bolted together in order to form one assembly. The idler pump and the drive pump are identical in construction and identical in operation. The pumps have identical control systems.

(9) Outlet port (drive pump) (10) Housing (11) Pilot pump

Oil from the hydraulic tank flows into inlet port (5) of the port block. Idler pump (3) delivers oil through outlet port (4). Drive pump (8) delivers oil through outlet port (9). Pilot pump (11) draws oil through inlet port (5). Pilot pump (11) delivers oil through outlet port (2).

29 Hydraulic System Systems Operation Section The power shift pressure is determined by the electronic controller. The power shift pressure flows into the main pumps through port (6). The negative flow control (NFC) pressure from the main control valve flows into idler pump (3) through port (1). The NFC pressure from the main control valve flows into drive pump (8) through port (7).

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Illustration 31 Main pumps (sectional views) (4) Outlet port (idler pump) (5) Inlet port (9) Outlet port (drive pump) (10) Housing (11) Pilot pump (12) Gear (pilot pump) (13) Plate (14) Pin (17) Regulator (18) Drive shaft (drive pump)

(19) Center line (20) Trunnion (21) Housing (22) Center line (23) Gear (drive pump) (24) Piston (25) Cylinder (26) Valve plate (27) Piston (28) Gear (idler pump)

Idler pump (3) and drive pump (8) are bent axial piston type pumps. The term “bent axial” describes the angular movement of the piston pump assembly. This movement is around the point of intersection of center lines (19) and (22). The output of the pumps changes depending on the angle of cylinder (25). Drive shaft (18) of the drive pump is coupled with the engine flywheel. Gear (23) of drive shaft (18) engages with gear (28) of shaft (29). When shaft (18) is driven by the engine flywheel, shaft (29) is driven through a mechanical linkage between gear (23) and gear (28). Gear (23) has the same number of teeth as gear (28). Therefore, both pumps rotate at the same speed as the engine.

(29) Shaft (idler pump) (30) Cylinder passage (31) Inlet passage (32) Inlet passage (33) Center hole (34) Outlet passage (35) Outlet passage (C) Radial direction (D) Radial direction

Because gear (23) engages with gear (12) of the pilot pump, pilot pump (11) rotates with the main pumps.

Main Pump Operation The idler pump (3) and drive pump (8) are identical in operation. The drive pump is described below.

30 Hydraulic System Systems Operation Section Drive shaft (18) is driven by the engine. Drive shaft (18) turns seven pistons (24). Therefore, angle cylinder (25) rotates. Angle cylinder (25) is in contact with valve plate (26). Angle cylinder (25) rotates on valve plate (26). Angle cylinder (25) pivots on pin (14). Gear (23) has plate (13) that retains the heads of pistons (24). Therefore, pistons (24) swivel in the sockets.

Illustration 33

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(26) Valve plate (drive pump) (37) Valve plate (idler pump)

Illustration 32

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(4) Outlet port (idler pump) (5) Inlet port (9) Outlet port (drive pump) (20) Trunnion (21) Housing (26) Valve plate (31) Inlet passage (33) Center hole (35) Outlet passage (36) Grooves

Oil from the hydraulic tank goes into pump housing (21) through inlet port (5). The oil goes through inlet passages (32) and (31) in plate (26). The oil then enters cylinder passage (30) of angle cylinder (25). Cylinder passage (30) is positioned over inlet passage (31). Angle cylinder (25) turns. The openings of passage (30) in angle cylinder (25) rotate. The openings line up with the position of passage (31). The displacement of pistons (24) changes depending on the position of angle cylinder (25). The piston draws oil by moving out of the bore of angle cylinder (25). Oil is pushed ahead of the piston as the piston moves through the bore. The oil that is pushed ahead of the piston goes through passage (30) and then through outlet passage (35) in valve plate (26). The oil passes through the drive pump through outlet port (9). The oil flows to the hydraulic circuit.

Valve plate (26) moves on machined grooves (36) of housing (21). Housing (21) has a circular contour. Center hole (33) of valve plate (26) holds one end of trunnion (20). The other end of the trunnion is held to piston (27) of regulator (17). Piston (27) moves in and out during regulator operation. Trunnion (20) is connected to valve plate (26). Therefore, the angle cylinder will move to a new position. Valve plate (26) moves in radial direction (C), and the angle cylinder decreases the angle of position. The stroke of pistons (24) decreases, and the pump output will decrease. When valve plate (26) moves in radial direction (D), pump output will increase. Inlet oil is sealed from outlet oil by a metal seal. The seal is formed between the face of valve plate (26) and the face of angle cylinder (25). On the opposite side of valve plate (26), a seal is made with the face of grooves (36). The sealing faces are made with precision in order to protect the faces from damage during disassembly and assembly. Valve plate (26) in the drive pump is not similar to valve plate (37) in the idler pump. Use extra care to install valve plates (26) and (37) in the correct position. i01638292

Pump Control (Main Hydraulic) SMCS Code: 3222; 5070; 5086


Main Pump Regulator

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Illustration 34 Regulator (Idler Pump) (5) Passage (7) Passage (8) Housing (9) Outlet port (idler pump) (10) Outlet passage (11) Negative flow control line (idler pump) (12) Port (13) Piston (14) Control piston (15) Passage (17) Passage (18) Spring

(19) Bushing (20) Passage (21) Pin (22) Spring (23) Line (power shift pressure) (24) Control piston (25) Passage (26) Spring chamber (27) Spring (28) Spring (29) Spring spacer (30) Spring

(31) Trunnion (32) Piston (33) Bolt (34) Ring (35) Passage (37) Piston chamber (38) Bolt (57) Idler pump delivery pressure (58) Drive pump delivery pressure (59) Negative flow control pressure (60) Power shift pressure

32 Hydraulic System Systems Operation Section During the horsepower control characteristic, both idler pump delivery pressure (57) and drive pump delivery pressure (58) act against the rings of control piston (14) while power shift pressure (60) is acting against the top end face of control piston (14). Control piston (14), pin (21), and control piston (24) shift in order to control the pump output. During negative flow control, negative flow control pressure (59) from line (11) acts against the top surface of piston (13). Control piston (14) shifts in order to move control piston (24) for pump flow control. Illustration 35

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Pump Compartment (11) Negative flow control line (idler pump) (23) Line (power shift pressure) (39) Regulator (idler pump) (41) Regulator (drive pump) (42) Negative flow control line (drive pump)

See the following list for the pump regulator operation.

• The pump regulator receives power shift pressure (60) from the electronic control system. The pump regulator controls the pump flow.

• The pump regulator maintains a constant

horsepower between the engine and the pump. The pump regulator receives a summation of idler pump delivery pressure (57) and drive pump delivery pressure (58). This operation is called the horsepower control characteristic.

• When the control levers are in NEUTRAL position or in PARTIAL position, the pump regulator receives the negative flow control pressure (59). Negative flow control pressure (59) controls the pump output flow. This is called the negative flow control. The pump regulator of the idler pump and drive pump are identical in construction and in operation. The following description identifies the idler pump regulator. Oil from the idler pump flows to pump regulator (39). Oil from the idler pump goes through passages (10) and (7) in housing (8) to passages (15) and (17). Oil through passage (15) controls piston (14). Oil through passage (17) goes to passage (25). Also, oil goes to piston chamber (37) through passage (35). Oil from the drive pump goes through passage (5) to control piston (14). Power shift pressure (60) goes through line (23) to a port on the pump regulator. The port is common to idler pump regulator (39) and drive pump regulator (41).

Note: For further information on the horsepower control characteristic and negative flow control, refer to the “Regulator Operation” section in this module.


Regulator Operation Horsepower Control Characteristic (Period Before Decreased Pump Stroke)

(45) Idler pump (57) Idler pump delivery pressure (58) Drive pump delivery pressure (60) Power shift pressure

Illustration 37 Regulator Operation (Partial View)

Illustration 36 Regulator Operation (5) Passage (14) Control piston (15) Passage (17) Passage (21) Pin (22) Spring (24) Control piston (25) Passage (26) Spring chamber (27) Spring (30) Spring (31) Trunnion (32) Piston (33) Bolt (34) Ring (35) Passage (37) Piston chamber (38) Bolt

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(5) Passage (14) Control piston (15) Passage (17) Passage (20) Passage (21) Pin (22) Spring (24) Control piston (25) Passage (26) Spring chamber (27) Spring (47) Top surface (48) Passage (49) Passage (57) Idler pump delivery pressure (58) Drive pump delivery pressure (60) Power shift pressure

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34 Hydraulic System Systems Operation Section When the machine operates with a low load, pump pressure acts on control piston (14). Idler pump delivery pressure (57) from passage (15) and drive pump delivery pressure (58) from passage (5) act on the ring grooves of control piston (14). Control piston (14) pushes down against pin (21). The force tries to move control piston (24) in the downward direction. Control piston (24) does not move down because the total forces of idler pump delivery pressure (57), drive pump delivery pressure (58) and power shift pressure (60) are less than the combined forces of springs (22), (27) and (30). The force of spring (30) is less than spring (27). Spring (30) is compressed before spring (27) is compressed. Passage (48) closes and passage (49) opens making an open connection between passage (25) and spring chamber (26). Tank pressure in spring chamber (26) acts on the bottom surface of ring (34). Idler pump delivery pressure (57) in piston chamber (37) pushes down piston (32) and ring (34). When bolt (33) comes in contact with bolt (38) movement stops. The mechanical linkage of piston (32) and the cylinder through trunnion (31) hold the cylinder at the maximum angle position. This allows the pump to maintain the maximum output flow.

Horsepower Control Characteristic (Period Before Destroke)

Illustration 38 Regulator Operation

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35 Hydraulic System Systems Operation Section (5) Passage (14) Control piston (15) Passage (17) Passage (20) Passage (21) Pin (22) Spring (24) Control piston (25) Passage (26) Spring chamber (27) Spring (28) Spring (30) Spring (31) Trunnion (32) Piston (34) Ring (35) Passage (37) Piston chamber (45) Idler pump (50) Set screw (57) Idler pump delivery pressure (58) Drive pump delivery pressure (60) Power shift pressure

Illustration 39

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Regulator Operation (Partial View) (5) Passage (14) Control piston (15) Passage (17) Passage (20) Passage (21) Pin (22) Spring (24) Control piston (25) Passage (26) Spring chamber (27) Spring (47) Top surface (48) Passage (49) Passage (50) Set screw (57) Idler pump delivery pressure (58) Drive pump delivery pressure (60) Power shift pressure

An increased load on the main pump increases idler pump delivery pressure (57) from passage (15) and increases drive pump delivery pressure (58) from passage (5). The force acts on ring grooves of piston (14). The combined forces of increased power shift pressure (60) through passage (20) acts on top surface (47) of control piston (14) to overcome the total forces of springs (22) and (30). Control piston (14) pushes down on control piston (24) through pin (21). Passage (49) closes and passage (48) opens. Therefore, idler pump delivery pressure (57) from passage (17) goes through passage (25) to the bottom surface of ring (34).

36 Hydraulic System Systems Operation Section Idler pump delivery pressure (57) acts on the top surface of ring (34). Therefore, oil is supplied to piston chamber (37) through passage (35). Idler pump delivery pressure (57) is common to both top and bottom surfaces of ring (34). The bottom surface area of ring (34) is larger than the top surface area. Therefore, ring (34) pushes up piston (32) against the forces of springs (30) and (28). The mechanical linkage of piston (32) and the cylinder through trunnion (31) cause the cylinder to move in a smaller angular direction. Therefore, the pump stroke decreases.

Negative Flow Control

As piston (32) moves up, spring (30) compresses. Spring (30) pushes up on control piston (24). Passage (48) closes and passage (49) partially opens. Therefore, oil flows from passage (25) to spring chamber (26). Because spring chamber (26) is open to tank pressure, the pressure on the bottom surface of ring (34) becomes less than idler pump delivery pressure (57). Piston (32) starts to stop upward movement. When the force of idler pump delivery pressure (57) on the top surface of ring (34) becomes more than the force on the bottom surface, piston (32) starts to move down. Because of the decreased compression force of spring (30), control piston (24) also starts to move down. Passage (49) now closes and passage (48) partially opens. Piston (32) now starts to move up again because of idler pump delivery pressure (57) through passage (25) to the bottom surface of the ring. When the idler pump delivery pressure (57) compresses spring (27), pistons (24) and (32) operate. Idler pump delivery pressure (57) is equal to the combined force of springs (28), (30), and (27). Piston (32) is in a balanced position and the angle of the cylinder is held at this point. Control piston (24) is held at a balanced position by keeping the openings slightly opened at passages (48) and (49). Turning set screw (50) changes the compression force of spring (22) which changes the pump output flow. Increased compression force of the spring increases the pump output flow.

Illustration 40 Negative Flow Control Operation (Partial View)

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37 Hydraulic System Systems Operation Section (11) Negative flow control line (idler pump) (12) Port (13) Piston (14) Control piston (17) Passage (19) Bushing (21) Pin (24) Control piston (27) Spring (28) Spring (30) Spring (32) Piston (45) Idler pump (47) Top surface (48) Passage (49) Passage (51) Passage (52) Center bypass passage (53) Negative flow control orifice (54) Main control valve (55) Spring spacer (56) Spring spacer (57) Idler pump delivery pressure (58) Drive pump delivery pressure (59) Negative flow control pressure (60) Power shift pressure

The rate of oil flow through center bypass passage (52) in main control valve (54) is maximum when all control levers are in NEUTRAL position. When the control levers are partially moved for a leveling operation, part of idler pump oil flows to passage (51) in order to decrease the rate of oil flow in passage (52). The oil flow in center bypass passage (52) is then restricted at negative flow control orifice (53). Negative flow control pressure (59) now develops in line (11). Negative flow control pressure (59) is dependent on the rate of oil flow through center bypass passage (52). Negative flow control pressure (59) is maximum when all control levers are in NEUTRAL position. The pump output flow is minimum. Note: For more information on negative flow control pressure (59), see Systems Operation, “Main Control Valve”. Negative flow control pressure (59) in line (11) enters the regulator through port (12). The force acts on the top surface of piston (13). Piston (13) tries to move down. Power shift pressure (60) acts on top surface (47) of control piston (14). Idler pump delivery pressure (57) and drive pump delivery pressure (58) act on the body of control piston (14). The combination acts on the inner surface of bushing (19). Bushing (19) tries to push up on piston (13).

Negative flow control pressure (59) acts on piston (13). The force which acts on piston (13) becomes greater than the force which acts on bushing (19). Piston (13) moves down allowing the negative flow control to function. When piston (13) moves down, bushing (19) is pushed down. Bushing (19) pushes down control piston (14). The cylinder decreases the angle of the cam which destrokes the pump. This operation is similar to the horsepower control characteristic. All control levers are in NEUTRAL position because negative flow control pressure (59) is maximum. Control piston (14) pushes down against pin (21). Pin (21) moves control piston (24) down opening passage (48). Idler pump delivery pressure (57) or drive pump delivery pressure (58) from passage (17) pushes piston (32) upward. The movement of piston (32) compresses springs (27), (28) and (30). When the top surface of spring spacer (56) comes in contact with spring spacer (55), control piston (24) and piston (32) are pushed up by the force of idler pump delivery pressure (57) or drive pump delivery pressure (58). A pressure balance is attained. Control piston (24) remains in the balance position in order to keep the openings of passages (48) and (49) slightly open. This operation is similar to the horsepower control characteristic. The cylinder is now held at the minimum angle position for minimum pump output flow. When the control levers are partially moved, negative flow control pressure (59) gradually decreases force on piston (13). The forces of compressed springs (27) and (30) overcome the force of the decreased negative flow control pressure (59). Therefore, control piston (24) moves up before spring spacer (56) comes in contact with spring spacer (55). During a leveling operation, the pump output flow is controlled between a minimum and a maximum. The flow depends on negative flow control pressure (59). When piston (13) moves up due to a lower negative flow control pressure (59), the total horsepower control functions.


Pressure/Flow Characteristic Curves

Illustration 41

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P-Q Characteristic Curves (1) Destroked position (2) Horsepower characteristics

The output characteristics of each pump depends on the following four pressures.

• Pump output circuit pressure of top pump • Pump output circuit pressure of bottom pump • Power shift pressure • Negative flow control pressure After a pump starts to operate, each pump has a set of pressure/flow characteristic curves. The pressure/flow characteristic curve represents a set of flow rates for distinct pump circuit pressures. Each point on horsepower characteristic (2) represents the respective flow rate and the respective pressure in order to maintain a constant output from the pump.

Main Control Valve i01630775

Main Control Valve SMCS Code: 5051



Illustration 42

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41 Hydraulic System Systems Operation Section Hydraulic schematic (1) Stick drift reduction valve (2) Line relief valve (stick cylinder rod end) (3) Boom drift reduction valve (4) Line relief valve (boom cylinder head end) (5) Return port (6) Main control valve (7) Stick regeneration valve (8) Load check valve (9) Parallel feeder passage (10) Straight travel solenoid valve (11) Right travel control valve (12) Attachment control valve (13) Bucket control valve (14) Center bypass passage (15) Boom I control valve (16) Stick II control valve (17) Relief valve (negative flow) (18) Straight travel control valve (19) Relief valve (negative flow) (20) Negative flow control orifice (21) Boom II control valve (22) Stick I control valve (23) Center bypass passage (24) Swing control valve (25) Left travel control valve (26) Load check valve (27) Boom regeneration valve (28) Line relief valve (boom cylinder rod end) (29) Negative flow control orifice (30) Line relief valve (stick cylinder head end) (31) Variable swing priority valve (32) Main relief valve (33) Stick unloading valve (34) Line relief valve (bucket cylinder rod end) (35) Line relief valve (bucket cylinder head end) (36) Parallel feeder passage (37) Inlet port (drive pump) (38) Negative flow control line (drive pump) (39) Inlet port (Idler pump) (40) Negative flow control line (idler pump) (41) Drive pump (42) Pilot pump (43) Idler pump (44) Hydraulic tank


Illustration 43 Main control valve ports

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43 Hydraulic System Systems Operation Section (AR1) Right travel control valve (REVERSE TRAVEL) (AR2) Attachment control valve (port) (AR3) Bucket control valve (BUCKET CLOSE) (AR4) Boom I control valve (BOOM LOWER) (AR5) Stick II control valve (STICK IN) (BR1) Right travel control valve (FORWARD TRAVEL) (BR2) Attachment control valve (port) (BR3) Bucket control valve (BUCKET OPEN) (BR4) Boom I control valve (BOOM RAISE) (BR5) Stick II control valve (STICK OUT) (AL1) Left travel control (REVERSE TRAVEL) (AL2) Swing control valve (SWING LEFT) (AL3) Stick I control valve (STICK IN) (AL4) Boom II control valve (BOOM RAISE) (BL1) Left travel control valve (FORWARD TRAVEL) (BL2) Swing control valve (SWING RIGHT) (BL3) Stick I control valve (STICK OUT) (aR1) Pilot port at right travel control valve (REVERSE TRAVEL)

(aR2) Pilot port at attachment control valve (aR3) Pilot port at bucket control valve (BUCKET CLOSE) (aR4) Pilot port at boom I control valve (BOOM LOWER) (aR5) Pilot port at stick II control valve (STICK IN) (aL1) Pilot port at left travel control valve (REVERSE TRAVEL) (aL2) Pilot port at swing control valve (SWING LEFT) (aL3) Pilot port at stick I control valve (STICK IN) (aL4) Pilot port at boom II control valve (BOOM RAISE) (bR1) Pilot port at right travel control valve (FORWARD TRAVEL) (bR2) Pilot port at attachment control valve (bR3) Pilot port at bucket control valve (BUCKET OPEN) (bR4) Pilot port at boom I control valve (BOOM RAISE) (bR5) Pilot port at stick II control valve (STICK OUT)

(bL1) Pilot port at left travel control valve (FORWARD TRAVEL) (bL2) Pilot port at swing control valve (SWING RIGHT) (bL3) Pilot port at stick I control valve (STICK OUT) (bL4) Pilot port at boom II control valve (STICK IN) (DST) Drain port (straight travel control valve) (HL) Negative flow signal pressure port (drive pump) (HR) Negative flow signal pressure port (idler pump) (Pi1) Pilot port (boom regeneration valve) (Pi2) Pilot port (stick regeneration valve) (Pi3) Pilot port (variable swing priority valve) (Pi4) Pilot port (straight travel solenoid valve) (R2) Return port (R3) Return port

Introduction

Illustration 45 Illustration 44 (10) Straight travel solenoid valve (11) Right travel control valve (12) Attachment control valve (13) Bucket control valve (15) Boom I control valve (16) Stick II control valve (18) Straight travel control valve (21) Boom II control valve (22) Stick I control valve (24) Swing control valve (25) Left travel control valve (28) Line relief valve (boom cylinder rod end) (30) Line relief valve (stick cylinder head end) (32) Main relief valve (34) Line relief valve (bucket cylinder rod end) (45) Right body (46) Left body

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Main control valve (bottom view) (3) Boom drift reduction valve (4) Line relief valve (boom cylinder head end)

Illustration 46 Bottom view of main control valve (1) Stick drift reduction valve (2) Line relief valve (stick cylinder rod end)

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44 Hydraulic System Systems Operation Section Main control valve (6) is located in the hydraulic system between the main pumps and actuators (cylinders and motors). Depending on the machine operation, the oil flow from idler pump (43), drive pump (41) and pilot pump (42) to the hydraulic circuits are controlled by the operation of each component in the main control valve. By this control, the speed and direction of the cylinders and the motors can be controlled and adjusted. The pump delivery pressure can be controlled and adjusted. The main control valve includes right body (46) and left body (45). The main control valve is coupled together with bolts in order to make one assembly. 1. The right travel control valve (11), attachment control valve (12), bucket control valve (13), boom I control valve (15) and stick II control valve (16) are located in right body (46). Hydraulic oil from the idler pump is delivered through inlet port (39), center bypass passage (14) and return port (5) to hydraulic tank (44). In addition, the following components are located in right body (46).

1. Straight travel control valve (18), left travel control valve (25), swing control valve (24), stick I control valve (22) and boom II control valve (21) are located in left body (45). Hydraulic oil from the drive pump is delivered through inlet port (37), center bypass passage (23) and return port (5) to hydraulic tank (44). In addition, the following components are located in left body (45). a. Stick drift reduction valve (1) prevents stick drift when the joystick for the stick is in the NEUTRAL position. The line relief valve (stick cylinder rod end) (2) is mounted on the stick drift reduction valve. The line relief valve (stick cylinder head end) (30) is also located on the left body. b. When the joysticks and/or travel levers/pedals are in the NEUTRAL position, or when the joysticks and/or travel levers/pedals are partially moved from the NEUTRAL position, negative flow control relief valve (17) and the negative flow control orifice (20) decrease the pump flow.

a. The line relief valve (bucket cylinder rod end) (34) and the line relief valve (bucket cylinder head end) (35) limit the pressure in the bucket circuit due to external forces.

c. Stick regeneration valve (7) supplies return oil from the rod end of the stick cylinder to the head end of the stick cylinder during the stick in function.

b. When the joysticks and/or travel levers/pedals are in the NEUTRAL position, or when the joysticks and/or travel levers/pedals are partially moved from the NEUTRAL position, negative flow control relief valve (19) and the negative flow control orifice (29) decrease the pump flow.

d. Stick unloading valve (33) reduces the back pressure in the rod end of the stick cylinder during the stick in function.

c. Boom drift reduction valve (3) prevents boom drift when the joystick for the boom is in the NEUTRAL position. The line relief valve (boom cylinder head end) (4) is mounted on the boom drift reduction valve. The line relief valve (boom cylinder rod end) (28) is also located on the right body.

f. Main relief valve (32) limits the main hydraulic system pressure.

• When the main control valve is in the NEUTRAL

d. Boom regeneration valve (27) supplies return oil from the head end of the boom cylinders to the rod end of the boom cylinders when the boom is lowered.

• The main control valve controls the negative

e. Load check valves (26) are part of the following control valves: attachment control valve (12), bucket control valve (13), boom I control valve (15), and stick II control valve (16).

e. Load check valves (8) are part of the following control valves: swing control valve (24) and stick I control valve (22).

position, no pump oil flows to the cylinders and the motors. Main control valve operation in the NEUTRAL position is described later in this section. flow control signal. For more information on the negative flow control operation, refer to Systems Operation, “Negative Flow Control”.

• The main control valve prevents cylinder drift with the load check valves. For more information on the load check valves, refer to Systems Operation, “Check Valve (Load)”.


• The main control valve limits the circuit pressure with relief valve operation. For more information on the limitation of circuit pressure, refer to Systems Operation, “Relief Valve (Main)” and Systems Operation, “Relief Valve (Line)”.

The description of other components that are installed on the main control valve or in the main control valve will be listed separately. Refer to the appropriate sections that are in this manual for further information on the components.

Main Control Valve Operation in NEUTRAL Position

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Illustration 47 Main control valve (neutral position) (1) Stick II control valve (2) Boom I control valve (3) Bucket control valve (4) Attachment control valve (5) Right travel control valve (6) Parallel feeder passage (7) Inlet port (8) Straight travel control valve

(9) Left travel control valve (10) Parallel feeder passage (11) Swing control valve (12) Stick I control valve (13) Boom II control valve (14) Right body (15) Left body (16) Negative flow control orifice

The idler pump supplies oil to right body (14) through inlet port (7). The oil then flows through center bypass passage (20) and parallel feeder passage (6). The drive pump supplies oil to left body (15) through inlet port (21). The oil then flows through center bypass passage (22) and parallel feeder passage (10).

(17) Return port (18) Negative flow control orifice (19) Return passage (20) Center bypass passage (21) Inlet port (22) Center bypass passage (23) Return passage

46 Hydraulic System Systems Operation Section When all of the joysticks and/or travel levers/pedals are in the NEUTRAL position, hydraulic oil from the idler pump flows through center bypass passage (20), negative flow control orifice (18), return passage (19), return passage (23) and return port (17) back to the hydraulic tank. Hydraulic oil from the drive pump from inlet port (21) flows through center bypass passage (22), negative flow control orifice (16) and return port (17) back to the hydraulic tank. Oil in parallel feeder passages (6) and (10) remains blocked by each control valve spool.

Individual Valve Operation

Activation of any joystick and/or travel levers/pedals provides two paths for hydraulic oil from the idler pump. One path flows through center bypass passage (20) to right travel control valve (5). The other path flows through parallel feeder passage (6), attachment control valve (4), bucket control valve (3) and boom I control valve (2). Activation of any joystick and/or travel levers/pedals also provides two paths for hydraulic oil from the drive pump. One path flows through center bypass passage (22) to left travel control valve (9) and stick I control valve (12). The other path flows through parallel feeder passage (10) to swing control valve (11).

Illustration 48

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Bucket control valve (NEUTRAL position) (1) Line relief valve (bucket cylinder rod end) (2) Port (3) Parallel feeder passage (4) Load check valve (5) Passage (6) Port (7) Line relief valve (bucket cylinder head end) (8) Pilot port (9) Pilot port (10) Return passage (11) Spool (12) Center bypass passage (13) Spring

The bucket control valve is used as a typical example for describing the operation of individual control valves. When the joysticks and/or travel levers/pedals are in the NEUTRAL position, pilot oil does not flow to port (8) and port (9). Spool (11) is centered in the NEUTRAL position by the force of spring (13). The hydraulic oil from the idler pump flows through center bypass passage (12) to the hydraulic tank.


Illustration 49

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Bucket control valve BUCKET CLOSE (2) Port (3) Parallel feeder passage (4) Load check valve (5) Passage (6) Port (8) Pilot port (10) Return passage (11) Spool (12) Center bypass passage (14) Passage (15) Passage

When the joystick for the bucket is moved to the BUCKET CLOSE position, pilot oil is supplied to pilot port (8). Spool (11) moves to the left. Center bypass passage (12) is closed and passage (15) becomes opened. Port (14) is now connected to return passage (10). Oil that is in parallel feeder passage (3) flows through load check valve (4), passage (5) and passage (15). The oil then flows to port (6). The bucket cylinder rod extends. When the bucket cylinder rod extends, the displaced oil in the rod end flows to port (2). Oil flows through port (2) to return passage (14) and back to the hydraulic tank.


Relief Valve (Main) SMCS Code: 5069

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Illustration 50 Cross section of straight travel control valve and main relief valve (1) Straight travel control valve (2) Main control valve (3) Right travel control valve (4) Check valve

(5) Check valve (6) Main relief valve (7) Delivery line (drive pump) (8) Delivery line (idler pump)

Main relief valve (6) is located in the left side of the main control valve. The main relief valve limits the maximum operating pressure of the travel hydraulic circuit and the implement hydraulic circuits when the machine is at a load condition.

(9) Drive pump (10) Idler pump (11) Internal passage

49 Hydraulic System Systems Operation Section The oil delivery from idler pump (10) enters main control valve (2) through delivery line (8). The oil delivery from drive pump (9) enters main control valve (2) through delivery line (7). Oil from the idler pump and the drive pump flow through check valves (4) and (5) to passage (11). Check valves (4) and (5) ensure that only the higher oil pressure from the idler pump or the drive pump flows through passage (11) to main relief valve (6).

Closed Position

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Illustration 51 Main relief valve (closed position) (11) (12) (13) (14)

Passage Seat Valve Spring

(15) Spring chamber (16) Seat (17) Poppet (18) Spring

Poppet (17) is positioned to the left against seat (16) by the force of spring (18). Valve (13) is positioned to the left against seat (12) by the force of spring (14).

(19) Passage (20) Orifice (21) Return passage

System pressure oil in passage (11) flows through orifice (20) into spring chamber (15). The force of the system pressure oil acts on poppet (17). When the force of system pressure oil in passage (11) is less than the force of spring (18), poppet (17) remains against seat (16). The pressure in passage (11) and the pressure in spring chamber (15) are now equal. System pressure oil in spring chamber (15) and the force of spring (14) maintain valve (13) against seat (12). There is no oil flow from passage (11) to return passage (21). When main pump oil pressure in passage (11) is less than the main relief pressure setting, main relief valve (6) remains in the closed position.


Open Position

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Illustration 52 Main relief valve (open position) (11) Passage (12) Seat (13) Valve (14) Spring (15) Spring chamber

(16) (17) (18) (19) (20)

Seat Poppet Spring Passage Orifice

System oil pressure in passage (11) and spring chamber (15) nears the main relief valve pressure setting. The force of the system oil pressure in spring chamber (15) becomes greater than the force of spring (18). Poppet (17) away from seat (16). System oil pressure now flows through seat (16) into valve chamber (23). The oil in valve chamber (23) now flows through passage (22) into return passage (21). This low pressure oil now returns to the hydraulic tank. At the same time as the oil in spring chamber (15) flows through seat (16), the system pressure oil in passage (11) flows through orifice (20). As the system oil pressure flows through orifice (20) into spring chamber (15) the pressure of the oil in spring chamber (15) decreases. The reduced pressure oil in spring chamber (15) allows the high pressure oil in passage (11) to force valve (13) away from seat (12). The high pressure oil in passage (11) now flows into passage (19) and return passage (21) to the hydraulic tank.

(21) Return passage (22) Passage (23) Valve chamber (24) Locknut (25) Adjustment screw

The amount of spring force of spring (18) that acts on poppet (17) determines the main relief valve pressure setting. Adjustments to the main relief valve pressure setting are made by changing the spring force of spring (18). The position of adjustment screw (25) determines the spring force of spring (18). Reference: Refer to Testing and Adjusting, “Relief Valve (Main) - Test and Adjust” for adjustment procedures. i01423093

Relief Valve (Line) SMCS Code: 5117 Each line relief valve contains a makeup valve. The line relief valves are located between each cylinder and the respective control valve.

51 Hydraulic System Systems Operation Section When the control valves for the cylinders are in the NEUTRAL position and an external force acts on one end of the cylinder, the oil pressure increases on the opposite end of the cylinder. The oil pressure also increases in the passage of the line relief valve that is connected to the cylinder. The line relief valve relieves the high pressure. The line relief valves limit the circuit pressure to the specified pressure settings. Reference: Refer to Testing and Adjusting, “Pressure Specifications” for the line relief valve pressure settings.

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Illustration 53 Line relief valve (CLOSED position) (1) Passage (2) Valve (3) Valve

(4) Spring chamber (5) Valve (6) Spring

The high pressure between the cylinder and the control valve is transmitted to passage (1). This pressurizes the line relief valve. The pressure oil flows from passage (1) through passage (9) of piston (7). The oil then flows into spring chamber (4). When the oil pressure is lower than the line relief valve pressure setting, valve (5) remains in the CLOSED position by the force of spring (6). The oil pressure in passage (1) and the oil pressure in spring chamber (4) are equal. The surface area of the right side of valves (2) and (3) is larger than the surface area of the left side. The force on the right side of valves (2) and (3) is greater than the force on the left side. Valves (2) and (3) are forced to the left. The pressure oil does not flow from passage (1) to passage (8).

(7) Piston (8) Return passage (9) Passage


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Illustration 54 Line relief valve (OPEN position) (1) (3) (4) (5)

Passage Valve Spring chamber Valve

(6) (7) (8) (9)

Spring Piston Return passage Passage

When the high pressure oil in passage (1) reaches the line relief valve pressure setting, valve (5) overcomes the force of spring (6) and opens. The high pressure oil flows from valve chamber (10) through passage (12) to return passage (8). The pressure now becomes low pressure. The pressure in passage (1) pushes piston (7) to the right until the piston comes in contact with the left end of valve (5). The oil in passage (1) flows around the end of piston (7) and the oil enters spring chamber (4). Since the flow around the outside of piston (7) is restricted, the oil in spring chamber (4) becomes low pressure oil. As a result, valve (3) is pushed to the right. Passage (11) opens. the oil flows from passage (1) to passage (8).

(10) Valve chamber (11) Passage (12) Passage


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Illustration 55 Line relief valve (makeup operation) (1) Passage (2) Valve (3) Valve

(4) Spring chamber (8) Return passage (9) Passage

The line relief valve functions as a makeup valve in the following manner. When oil from one end of the cylinder is discharged through the line relief valve, a vacuum condition is created on the opposite end of the cylinder. Makeup oil is needed to prevent the vacuum condition in the cylinder. When the vacuum condition occurs on the end of the cylinder that is connected to passage (1), a vacuum condition also occurs in spring chamber (4). The pressure of the oil in passage (8) acts on shoulder (13) of valve (2). Since a vacuum condition is present in spring chamber (4), the pressure in spring chamber (4) is lower than the pressure of the return oil in passage (8). Valves (2) and (3) are pushed to the right by the pressure of the return oil in passage (8). Return oil flows from passage (8) to passage (1) as makeup oil in order to remove the vacuum condition in the cylinder. i01638151

Check Valve (Load) SMCS Code: 5472 The load check valve performs the following two functions.

• The load check valve prevents unexpected

movement of an implement when a joystick is initially activated at a low pump delivery pressure.

(13) Shoulder

• The load check valve prevents oil loss from a high pressure circuit to a lower pressure circuit.


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Illustration 56 Boom I control valve (partial shift) (1) Port (boom cylinder head end) (2) Passage (3) Spring (4) Load check valve

(5) Port (boom cylinder rod end) (6) Return passage (7) Parallel feeder passage (8) Spring

When the joystick for the boom is in the NEUTRAL position, spring (8) positions spool (10) in the center position. The idler pump is at a destroked position. The idler pump is delivering standby pressure to the boom I control valve. The pump delivery pressure in center bypass passage (11) and parallel feeder passage (7) is lower than the pressure in the boom cylinder head end at port (1). Load check valve (4) is in the CLOSED position.

(9) Pilot port (10) Spool (11) Center bypass passage

Slight movement of the joystick for the boom toward the BOOM RAISE position causes low pilot oil pressure to enter port (9). Spool (10) shifts slightly to the right. The idler pump begins to move to an upstroke position. A passage partially opens allowing the oil from the rod end of the boom cylinders in port (5) to flow to return passage (6). A passage partially opens allowing the oil from the head end of the boom cylinders in port (1) to flow through passage (2). The work load pressure from the head end of the boom cylinders and the force of spring (3) now acts on load check valve (4). Since the pump delivery pressure is lower than the work load pressure in passage (2), load check valve (4) remains in the closed position. The oil in the boom cylinder head end is blocked.


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Illustration 57 Boom I control valve (full shift) (1) Port (boom cylinder head end) (2) Passage (3) Spring (4) Load check valve

(5) Port (boom cylinder rod end) (6) Return passage (7) Parallel feeder passage (8) Spring

As the joystick for the boom is moved farther from the NEUTRAL position, the pilot oil pressure at pilot port (9) increases. Spool (10) shifts farther to the right. The idler pump upstrokes farther. The pump delivery pressure in center bypass passage (11) and parallel feeder passage (7) increases. Load check valve (4) will not open until the pump delivery pressure becomes greater than the combined force of the work load pressure in passage (2) and the force of spring (8). Unexpected downward movement of the boom during a BOOM RAISE operation is prevented. Load check valve (4) also prevents oil loss from a high pressure circuit to a lower pressure circuit. For example, the bucket cylinder is moved under a light load, and the boom cylinders are raised at the same time. The high pressure oil of the boom cylinders wants to flow toward the low pressure side of the bucket cylinder. The load check valve prevents the boom from lowering.

(9) Pilot port (10) Spool (11) Center bypass passage

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Negative Flow Control System SMCS Code: 5050-NE; 5455

Introduction The idler pump and the drive pump receive signal oil pressure from the center bypass passages of the main control valve. This signal oil pressure that is created in the center bypass passages of the main control valve is called negative flow control pressure. Negative flow control pressure flows to the regulators at the idler pump and the drive pump in order to control the output flow of the pumps. Negative flow control pressure is created during the following machine operating conditions.

• All of the joysticks and travel levers/pedals are in the NEUTRAL position.


• Any of the joysticks and/or travel levers/pedals

are partially moved from the NEUTRAL position in order to perform a fine control operation.

• A boom lower operation is performed alone.

Illustration 58

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Main control valve (top view) (12) Negative flow control line to drive pump (13) Negative flow control line to idler pump

The right body of the control valve receives supply oil from the idler pump. Negative flow control pressure from the right body of the main control valve flows through negative flow control line (13) to the idler pump. The left body of the control valve receives supply oil from the drive pump. Negative flow control pressure from the left body of the main control valve flows through negative flow control line (12) to the drive pump. The negative flow control operation of the idler pump and the drive pump is identical.



Illustration 59

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59 Hydraulic System Systems Operation Section Negative flow control operation (control valves in the NEUTRAL position) (1) Center bypass passage (2) Return line (3) Center bypass passage (4) Passage (5) Relief valve (negative flow control) (6) Relief valve (negative flow control) (7) Negative flow control orifice (8) Port (9) Negative flow control orifice (10) Passage (11) Return passage (12) Negative flow control line (13) Negative flow control line (14) Drive pump (15) Idler pump (16) Pilot pump

Illustration 60

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Bucket control valve (NEUTRAL position) (3) Center bypass passage

Illustration 59 shows the negative flow control operation at the main control valve when all of the control valves are in the NEUTRAL position. When all of the joysticks and the travel levers/pedals are in the NEUTRAL position, the spools of the individual control valves are in the NEUTRAL position. Oil flow to the cylinders and motors is blocked. Center bypass passages (1) and (3) are open. All of the oil delivery from idler pump (15) flows through center bypass passage (3), passage (4) and negative flow control orifice (9) to return line (2). Negative flow control orifice (9) restricts the oil flow. The pressure in passage (4) increases. Increased negative flow control pressure now flows through passage (10) and negative flow control line (13) to the pump regulator. The negative flow control operation of the idler pump regulator causes the swashplate of the idler pump to move to the minimum angle position. The output flow of the idler pump is decreased due to the increased negative flow control pressure that is created in center bypass passage (3). Since center bypass passage (1) is also open, the negative flow control operation of the drive pump regulator is identical to the negative flow control operation of the idler pump regulator.

Reference: For more information concerning the negative flow control operation of the main pump regulators, refer to Systems Operation, “Pump Control (Main Hydraulic)”.


Illustration 61

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61 Hydraulic System Systems Operation Section Negative flow control operation (bucket control valve in the BUCKET CLOSE position) (1) Center bypass passage (2) Return line (3) Center bypass passage (4) Passage (5) relief valve (negative flow control) (6) relief valve (negative flow control) (7) Negative flow control orifice (8) Port (9) Negative flow control orifice (10) Passage (11) Return passage (12) Negative flow control line (13) Negative flow control line (14) Drive pump (15) Idler pump (16) Pilot pump

The joystick for the bucket has been moved fully to the BUCKET CLOSE position. Pilot oil has fully shifted the bucket control valve. The oil delivery from idler pump (15) flows into the right body of the main control valve. The oil delivery flows through center bypass passage (3) to the bucket control valve. Since the spool in the bucket control valve is fully shifted, center bypass passage (3) is blocked. All of the oil delivery from the idler pump flows to the head end of the bucket cylinder. No oil flows to negative flow control orifice (9) and no negative flow control pressure is created in center bypass passage (3). Since no negative flow control pressure is sent to the idler pump regulator, the idler pump regulator moves the swashplate of the idler pump toward the maximum angle position. The output flow of the idler pump is increased since no negative flow control pressure is created in center bypass passage (3).

Fine Control Operation

Illustration 62

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Bucket control valve (BUCKET CLOSE position) (3) Center bypass passage

Illustration 61 shows the negative flow control operation at the main control valve when only the bucket control valve is in the BUCKET CLOSE position. All of the control valves in the left body of the main control valve are in the NEUTRAL position. Center bypass passage (1) is open. All of the oil delivery from the drive pump flows through center bypass passage (1) to negative flow control orifice (7). Since all of the oil delivery from drive pump (14) is restricted by negative flow control orifice (7), negative flow control pressure (PN) in center bypass passage (1) is at maximum pressure. The negative flow control pressure flows through negative flow control line (12) to the drive pump regulator. The negative flow control operation of the drive pump regulator causes the swashplate of the drive pump to move to the minimum angle position. The output flow of the drive pump is decreased due to the increased negative flow control pressure that is created in center bypass passage (1).

Illustration 63

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Bucket control valve (fine control) (3) Center bypass passage (21) Parallel feeder passage (22) Port (23) Spool (24) Passage (P) Pilot pressure

When the joystick for the bucket is in the NEUTRAL position, spool (23) is in the NEUTRAL position. The oil delivery from the idler pump flows through center bypass passage (3) to negative flow control orifice (9). When the joystick for the bucket is partially moved from the NEUTRAL position in order to perform a fine control operation, pilot pressure (P) enters the control valve at the pilot port. Pilot pressure shifts spool (23) slightly to the left. The movement of spool (23) partially opens passage (24). Center bypass passage (3) is partially blocked.

62 Hydraulic System Systems Operation Section The oil delivery from the idler pump is now divided into two flow paths. A portion of the oil delivery from the idler pump flows through center bypass passage (3) to negative flow control orifice (9). The remainder of the oil delivery from the idler pump flows through parallel feeder passage (21) and passage (24) to port (22). The oil flow from center bypass passage (3) to negative flow control orifice (9) decreases. The flow resistance through the negative flow control orifice decreases and the negative flow control pressure (PN) in passage (4) decreases. The negative flow control pressure that is sent to the regulator at the idler pump decreases. The pump regulator causes the swashplate of the idler pump to move toward the maximum angle position. The output flow of the pump is increased due to the decrease in negative flow control pressure (PN). When the joystick for the bucket is moved to the full stroke position, spool (23) shifts fully to the left. Center bypass passage (3) is now blocked by spool (23). Since there is no oil flow through center bypass passage (24), no negative flow control pressure is created. The swashplate of the idler pump is moved to the maximum angle position. The output flow of the idler pump is maximum. The output flow of the idler pump is now controlled by the constant horsepower flow control. The ability to modulate the negative flow control pressure by partial movement of the joystick enables fine control of the implements.


Relief Valve (Negative Flow Control)

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Illustration 64 Relief valve (negative flow control) (2) Return line (3) Center bypass passage (4) Passage (5)

(9) Negative flow control orifice (11) Return passage (17) Plug (18) Spring

The following description is given for the operation of the relief valve that is located in the right body of the main control valve. The operation of the relief valve for the negative flow control that is located in the left body of the main control valve is identical. Relief valve (5) for the negative flow control consists of plug (17), spring (18), relief valve body (19) and valve (20). When any one of the joysticks and/or travel levers/pedals is at the full stroke position, the oil flow through center bypass passage (3) is blocked. No oil flows to the relief valve for the negative flow control. When all of the joysticks and/or travel levers/pedals are suddenly returned to the NEUTRAL position, all of the output flow from the idler pump flows through center bypass passage (3). The negative flow control pressure in center bypass passage (3) and passage (4) suddenly increases. When the negative flow control pressure becomes higher than the pressure setting of relief valve (5) for the negative flow control, valve (20) shifts to the left against the force of spring (18). Oil in center bypass passage (3) is now allowed to flow past valve (20) into return passage (11) to the hydraulic tank. This prevents the hydraulic shock that occurs due to sudden changes in negative flow control pressure.

(19) Relief valve body (20) Valve (PN) Negative flow control pressure

After the hydraulic shock is relieved by the relief valve for the negative flow control, the force of spring (18) shifts valve (20) to the right. All of the output flow from the idler pump flows through center bypass passage (3), negative flow control orifice (9) and return line (2) to the hydraulic tank. Negative flow control pressure (PN), that is created in center bypass passage (3), reaches maximum pressure since all of the oil flow is restricted by negative flow control orifice (9). The negative flow control pressure flows to the idler pump regulator. The regulator at the idler pump causes the swashplate of the idler pump to move to the minimum angle position. The output flow of the idler pump is decreased due to the increase in negative flow control pressure (PN).

Boom System i01630795

Boom Hydraulic System SMCS Code: 5050-BM

Boom Raise (High Speed)


Illustration 65

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65 Hydraulic System Systems Operation Section Hydraulic schematic for BOOM RAISE (high speed) (1) Boom cylinders (2) Line (oil flow from boom cylinder rod end) (3) Line (oil flow to boom cylinder head end) (4) Valve (5) Boom drift reduction valve (6) Return line (7) Port (8) Parallel feeder passage (9) Return passage (10) Line (11) Main control valve (12) Passage (13) Check valve (14) Load check valve (15) Port (16) Boom II control valve (17) Parallel feeder passage (18) Return passage (19) Boom I control valve (20) Port (21) Pilot line (22) Pilot control valve (boom and bucket) (23) Pilot line (24) Pilot line (25) Pilot line (26) Pressure reducing valve for boom priority (27) Drive pump (28) Idler pump (29) Pilot pump (33) Spring (37) Spring

Illustration 67 Boom drift reduction valve (bottom view) (5) Boom drift reduction valve

The oil delivery from idler pump (28) flows through parallel feeder passage (17) in main control valve (11) to boom I control valve (19). The oil delivery from drive pump (27) flows through parallel feeder passage (8) in main control valve (11) to boom II control valve (16).

A BOOM RAISE operation at high speed is accomplished when the oil delivery from both drive pump (27) and idler pump (28) is supplied to the head end of boom cylinders (1). Boom I control valve (19) and boom II control valve (16) operate during the high speed operation. A BOOM RAISE operation at low speed is accomplished when the oil delivery from only idler pump (28) is supplied to the head end of boom cylinders (1). During the low speed operation, boom I control valve (19) operates alone.

Illustration 66 Main control valve compartment (16) Boom II control valve (19) Boom I control valve

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When the joystick for the boom is moved to the full BOOM RAISE position, the pilot oil flows from pilot control valve (22) through pilot line (24). The pilot oil flow then divides into two flow paths. Part of the pilot oil flows through pilot line (21) to port (7) of main control valve (11). The remainder of the pilot oil flows through pilot line (23) to port (20) of the main control valve. A portion of the oil in pilot line (23) also flows through pilot line (25) to the pressure reducing valve for boom priority (26). During a combined operation of BOOM RAISE and STICK IN, the pilot oil flow to the pressure reducing valve for boom priority (26) causes the boom circuit to receive oil flow priority. This allows the boom to raise at a high speed.


Illustration 68

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Illustration 69

Boom I control valve (BOOM RAISE position)

Boom II control valve (BOOM RAISE position)

(14) Load check valve (17) Parallel feeder passage (18) Return passage (20) Port (30) Port (31) Passage (32) Passage (33) Spring (34) Passage (35) Spool

(7) Port (8) Parallel feeder passage (13) Check valve (15) Port (36) Passage (37) Spring (38) Spool (39) Passage

The pilot oil flow from port (20) shifts spool (35) of boom I control valve (19) against the force of spring (33). The oil delivery from the idler pump in parallel feeder passage (17) flows through load check valve (14), passage (31), passage (34) and port (30) to boom drift reduction valve (5). The oil delivery from the idler pump shifts valve (4) in boom drift reduction valve (5) to the right. The oil delivery from the idler pump then flows through line (3) to the head end of boom cylinders (1). Note: For more information on the boom drift reduction valve, refer to Systems Operation, “Boom Drift Reduction Valve”.

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The pilot oil flow in port (7) of boom II control valve (16) shifts spool (38) against the force of spring (37). The oil delivery from the drive pump in parallel feeder passage (8) now flows through passage (36), passage (39), check valve (13) and flows out of port (15) to line (10). The oil delivery from the drive pump combines with the oil delivery from the idler pump at boom drift reduction valve (5). The combined pump oil flows through passage (12) and line (3) to the head end of boom cylinders (1). Note: The swing priority valve does not affect the boom II control valve. Return oil from the rod end of boom cylinders (1) flows through line (2) to boom I control valve (19). The oil then flows through passage (32), return passage (18), return passage (9) and return line (6) to the hydraulic tank.

Boom Raise (Low Speed) When the joystick for the boom is moved less than half of the travel distance for BOOM RAISE, low pilot oil pressure is supplied to boom I control valve (19) and boom II control valve (16).

67 Hydraulic System Systems Operation Section When the boom is raised at a low speed, boom I control valve (19) opens and boom II control valve (16) remains closed. The force of spring (33) in boom I control valve (19) is less than the force of spring (37) in boom II control valve (16). Because of the low pilot oil pressure, boom I control valve (19) will open and boom II control valve (16) will remain closed. The oil delivery from idler pump (28) now flows to the head end of boom cylinders (1). Without the oil delivery from drive pump (27), the cylinder rod movement slows down when the boom is raised. The low speed operation of the boom is performed.

Boom Priority


Illustration 70

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69 Hydraulic System Systems Operation Section Hydraulic schematic for BOOM RAISE and STICK IN (1) Boom cylinders (22) Pilot control valve (boom and bucket) (26) Pressure reducing valve for boom priority (40) Stick II control valve (41) Pilot control valve (stick and swing)

During combined operations of BOOM RAISE and STICK IN, the pilot oil pressure from the pilot control valve for the boom (22) activates the pressure reducing valve for boom priority (26). The pressure reducing valve for boom priority (26) causes oil flow priority to the head end of the boom cylinders (1) during this combined hydraulic operation. When the joystick for the stick is moved to the STICK IN position, a portion of the pilot oil from the pilot control valve for the stick (41) flows through the pressure reducing valve for the boom priority (26) to the stick II control valve (40). As the joystick for the boom is moved farther from the NEUTRAL position during a BOOM RAISE operation, pilot oil pressure from the pilot control valve for the boom (22) increases. This gradual increase in pilot oil pressure causes the spool in the pressure reducing valve for the boom priority (26) to gradually shift. A portion of the pilot oil that flows to stick II control valve (40) from the pilot control valve for the stick (41) is routed to the hydraulic tank. The pilot oil pressure that acts on stick II control valve (40) decreases. Stick II control valve (40) shifts toward the NEUTRAL position. The amount of oil flow from the main pumps to the stick hydraulic circuit decreases. This causes a greater portion of the oil flow from the main pumps to flow to the head end of the boom cylinders (1). Since the pilot oil pressure from the pilot control valve for the boom (22) directly corresponds to the amount of movement or position of the joystick a gradual change to boom priority occurs. Thus, boom priority is controlled by the position of the joystick for the boom and boom priority automatically activates when the joystick reaches a certain position during a BOOM RAISE operation.

Boom Lower


Illustration 71

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71 Hydraulic System Systems Operation Section Hydraulic schematic for BOOM LOWER (1) Boom cylinders (2) Line (oil flow to boom cylinder rod end) (3) Line (oil flow from boom cylinder head end) (4) Valve (5) Boom drift reduction valve (14) Load check valve (16) Boom II control valve (17) Parallel feeder passage (18) Return passage (19) Boom I control valve (22) Pilot control valve (boom and bucket) (27) Drive pump (28) Idler pump (29) Pilot pump (33) Spring (42) Orifice (43) Boom regeneration valve (44) Port (45) Orifice (46) Negative flow control line (47) Center bypass passage (48) Port (50) Valve (51) Passage (52) Drain line (53) Passage (54) Pilot line (55) Pilot line

Reference: For more information concerning the negative flow control operation, refer to Systems Operation, “Negative Flow Control”.

During a BOOM LOWER operation, the oil delivery from only idler pump (28) is supplied to boom cylinders (1) through boom I control valve (19). Boom I control valve (19) operates alone. Boom II control valve (16) is not operational in the BOOM LOWER operation. Illustration 72

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The BOOM LOWER operation contains a regeneration circuit. When the joystick for the boom is moved to the BOOM LOWER position, orifice (42) in boom I control valve (19) and boom regeneration valve (43) are operational in the boom hydraulic circuit. The return oil flow from the head end of boom cylinders (1) flows through boom regeneration valve (43) to the rod end of the boom cylinders. The boom regeneration valve is described later in this section.

Boom I control valve (BOOM LOWER position)

When the joystick for the boom is moved to the BOOM LOWER position, pilot oil from pilot control valve (22) flows through pilot line (54). The pilot oil flow then divides into three flow paths. Part of the pilot oil flows through port (48) to boom I control valve (19). Part of the pilot oil flows through port (44) to boom regeneration valve (43). The remainder of the pilot oil flows through pilot line (45) of boom drift reduction valve (5).

The pilot oil flow from port (48) shifts spool (35) in boom I control valve (19) against the force of spring (33). The oil delivery from the idler pump in parallel feeder passage (17) flows through load check valve (14), passage (49) and port (32). The oil delivery from the idler pump then flows through line (2) to the rod end of boom cylinders (1).

Since the pilot oil pressure has caused the spool in boom I control valve (19) to shift against the force of spring (33), the oil delivery from the idler pump that flows through center bypass passage (47) is restricted by orifice (45). The negative flow control pressure in negative flow control line (46) decreases. The idler pump upstrokes because of the negative flow control operation.

(14) Load check valve (17) Parallel feeder passage (18) Return passage (30) Port (32) Port (33) Spring (35) Spool (42) Orifice (45) Orifice (48) Port (49) Passage

The return oil from the head end of boom cylinders (1) flows through line (3) into boom drift reduction valve (5). Since valve (50) is shifted by the pilot pressure from pilot line (45), passage (51) is open to drain line (52). The return oil pressure shifts valve (4) to the right. The return oil in line (3) enters passage (53).

72 Hydraulic System Systems Operation Section A portion of the return oil flows into port (30) of boom I control valve (19). The return oil flow is restricted by orifice (40). The return oil pressure in passage (53) increases. Most of the return oil flows through boom regeneration valve (43). The return oil is now supplied to the head end of the boom cylinders through line (2).

Boom Regeneration Valve

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Illustration 73 Boom regeneration valve (slow boom down) (11) Main control valve (43) Spool (boom regeneration valve)

(45) Pilot port (53) Passage

(56) Passage (57) Check valve


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Illustration 74 Boom regeneration valve (fast boom down) (11) Main control valve (43) Spool (boom regeneration valve)

(45) Pilot port (53) Passage

The boom hydraulic circuit contains a regeneration circuit. This regeneration circuit allows the return oil from the head end of the boom cylinders to be supplied to the rod end of the boom cylinders during the BOOM LOWER operation. When the joystick for the boom is moved to the BOOM LOWER position, pilot oil flow from the pilot control valve (boom and bucket) enters pilot port (44). Spool (43) in the boom regeneration valve shifts downward. The return oil from the head end of the boom cylinders flows through passage (53) and through the throttling slots on the spool for the boom regeneration valve to check valve (57). Check valve (57) opens and the return oil flows through passage (56). The return oil from the head end of the boom cylinders in passage (56) combines with the oil delivery from the idler pump. This combined oil now flows to the rod end of the boom cylinders. The oil delivery from only the idler pump is used for the BOOM LOWER operation. Since the boom regeneration valve supplies return oil from the head end to the rod end of the boom cylinders, more efficient use of the oil delivery from the idler pump is achieved during a BOOM LOWER operation.

(56) Passage (57) Check valve i01426779

Boom Drift Reduction Valve SMCS Code: 5143-BM The boom drift reduction valve is placed in the boom circuit between the main control valve and the boom cylinders. When the joystick for the boom is in the NEUTRAL position, the boom drift reduction valve stops oil leakage from the head end of the boom cylinders . Stopping oil leakage prevents boom drift.


Boom Raise

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Illustration 75 Boom drift reduction valve (BOOM RAISE) (1) (2) (3) (4)

Passage Valve Spring Spring chamber

(5) (6) (7) (8)

Passage Port Port Port

When the joystick is moved to perform a BOOM RAISE operation, pilot oil is not sent from the pilot control valve to port (15) of boom drift reduction valve (16). Spool (11) does not shift. The oil flow from the boom II control valve enters port (6) of the boom drift reduction valve. The oil flow from the boom I control valve enters port (7) of the boom drift reduction valve. The combined oil flow from ports (6) and (7) flows into passage (1). As the oil pressure in passage (1) increases, valve (2) shifts against the force of spring (3). The oil in spring chamber (4) flows through passages (5) and (9) to port (8). The oil delivery in passage (1) now flows through port (8) to the head end of the boom cylinders.

(9) Passage (11) Spool (15) Port (16) Boom drift reduction valve


Boom Lower

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Illustration 76 Boom drift reduction valve (BOOM LOWER) (1) (2) (3) (4) (5)

Passage Valve Spring Spring chamber Passage

(6) Passage (7) Port (8) Port (11) Spool (13) Drain line

(15) Port (16) Boom drift reduction valve (18) Port (20) Spring chamber (21) Plug

When the joystick is moved to perform a BOOM LOWER operation, pilot oil is sent from the pilot control valve to port (15) of boom drift reduction valve (16). Spool (11) shifts downward until the spool contacts plug (21). The oil in spring chamber (4) flows through passage (5), the passage in spool (11), spring chamber (20), passage (6), port (18) and drain line (13) to the hydraulic tank.

Stick System

The return oil from the boom cylinder head end enters port (8). Since the pressure in spring chamber (4) is low, the oil in port (8) shifts valve (2) against the force of spring (3). The oil from the head end of the boom cylinders flows through port (8), passage (1) and passage (7) to the boom I control valve.

Stick Out

i01631101

Stick Hydraulic System SMCS Code: 5050


Illustration 77

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77 Hydraulic System Systems Operation Section When the stick hydraulic circuit is operated independently of other hydraulic circuits, stick I control valve (21) and stick II control valve (13) are operational for both the STICK IN operation and the STICK OUT operation. When the stick I control valve and the stick II control valve are operated, the oil delivery from idler pump (29) and drive pump (28 ) is combined. The oil delivery from both pumps flows to stick cylinder (1) in order to perform a stick operation.

Hydraulic schematic for STICK OUT (1) Stick cylinder (2) Line (oil flow from stick cylinder rod end) (3) Line (oil flow to stick cylinder head end) (4) Valve (5) Stick drift reduction valve (6) Main control valve (7) Line (8) Passage (9) Return passage (10) Return passage (11) Return passage (12) Center bypass passage (13) Stick II control valve (14) Center bypass passage (15) Load check valve (16) Check valve (17) Passage (18) Center bypass passage (19) Check valve (20) Boom II control valve (21) Stick I control valve (22) Parallel feeder passage (23) Return line (24) Pilot line (25) Pilot line (26) Pilot line (27) Pilot control valve (stick and swing) (28) Drive pump (29) Idler pump (30) Pilot pump

The oil delivery from idler pump (29) flows through parallel feeder passage (22) in main control valve (6) to stick II control valve (13). The oil delivery from drive pump (28) flows through center bypass passage (18) in main control valve (6) to stick II control valve (21). When the joystick for the stick is moved to the STICK OUT position, the pilot oil flows from pilot control valve (27) through pilot line (26). The pilot oil flow then divides into two flow paths. Part of the pilot oil flows through pilot line (24) to stick I control valve (21) in main control valve (6). The remainder of the pilot oil flows through pilot line (25) to stick II control valve (13) in the main control valve. The pilot oil in pilot line (24) shifts the spool of stick I control valve (21). The oil delivery from drive pump (28) that is in center bypass passage (18) flows through load check valve (15), passage (17) and passage (8). The oil delivery from the drive pump then enters stick drift reduction valve (5). Valve (4) shifts to the left and the oil delivery flows through line (3) to the rod end of stick cylinder (1).

Illustration 78

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Main control valve (13) Stick II control valve (21) Stick I control valve

The pilot oil in pilot line (25) shifts the spool of stick II control valve (13). The oil delivery from idler pump (29) in center bypass passage (12) cannot flow through the stick II control valve to center bypass passage (14) and return passage (11). Part of the oil delivery from the idler pump now flows through check valve (16) and the stick II control valve to line (7). The remainder of the oil delivery from the idler pump flows through parallel feeder passage (22), check valve (19) and the stick II control valve to line (7). All of the oil delivery from the idler pump in line (7) flows to stick drift reduction valve (5) and combines with the oil delivery from the drive pump. The combined pump oil flows to the rod end of stick cylinder (1). This combined pump oil causes the cylinder to retract at an increased rate of speed. Return oil from the head end of the stick cylinder flows through line (2) and return passage (9) to stick I control valve (21). The return oil then flows through return passage (10) and return line (23) to the hydraulic tank.

Illustration 79 Main control valve (bottom view) (5) Stick drift reduction valve

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Stick In


Illustration 80

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79 Hydraulic System Systems Operation Section Hydraulic schematic for STICK IN (fast with regeneration) (1) Stick cylinder (2) Line (oil flow to stick cylinder rod end) (3) Line (oil flow from stick cylinder head end) (4) Valve (5) Stick drift reduction valve (6) Main control valve (9) Passage (10) Return passage (11) Return passage (12) Center bypass passage (13) Stick II control valve (15) Load check valve (16) Check valve (18) Center bypass passage (19) Check valve (21) Stick I control valve (22) Parallel feeder passage (23) Return line (27) Pilot control valve (stick and swing) (28) Drive pump (29) Idler pump (30) Pilot pump (31) Stick regeneration valve (32) Stick unloading valve (33) Pilot line (34) Pilot line (35) Pilot line (36) Pilot line (37) Passage (38) Pilot line (39) Pilot line (40) Pressure reducing valve for boom priority (41) Pilot line (42) Line (43) Passage (44) Passage (45) Passage (46) Passage (47) Passage (48) Check valve

The STICK IN operation contains a regeneration circuit. When the joystick for the stick is moved to the STICK IN position, stick regeneration valve (31) and stick unloading valve (32) are operational in the stick hydraulic circuit. The return oil from the rod end of stick cylinder (1) is supplied to the head end of the stick cylinder. The regeneration circuit makes more effective use of the return oil from the stick cylinder. This allows the oil delivery from the idler pump and the drive pump to perform other implement functions during a STICK IN operation. When the joystick for the stick is moved to the STICK IN position, pilot oil from pilot control valve (27) flows through pilot line (33). The pilot oil flow then divides into several flow paths. Part of the pilot oil flows through pilot line (34), pilot line (35) and pilot line (36) to stick I control valve (21). The pilot oil in pilot line (36) also flows through passage (37) in stick drift reduction valve (5). Part of the pilot oil flows through pilot line (38) to stick regeneration valve (31). The remainder of the pilot oil flows through pilot line (39), the pressure reducing valve for boom priority (40) and pilot line (41) to stick II control valve (13).

Since the pilot oil pressure has caused the spool in stick I control valve (21) to shift downward, the oil delivery from the drive pump flows through center bypass passage (18), load check valve (15), stick I control valve (21) and passage (9) to line (2). The pilot oil pressure in pilot line (41) has caused the spool in stick II control valve (13) to shift downward. Part of the oil delivery from the idler pump that is in center bypass passage (12) flows through check valve (16) and stick II control valve (13) to line (42). The remainder of the oil delivery from the idler pump flows through parallel feeder passage (22), check valve (19) and stick II control valve (13) to line (42). All of the oil delivery from the idler pump in line (42) flows to line (2) and combines with the oil delivery from the drive pump. The combined pump oil flows to the head end of stick cylinder (1). The return oil from the rod end of the stick cylinder flows through line (3) to stick drift reduction valve (5). Valve (4) in the stick drift reduction valve shifts to the left and the return oil enters passage (43). Part of the return oil in passage (43) flows through stick I control valve (21), return passage (10) and return line (23) to the hydraulic tank. The remainder of the return oil flows through the regeneration circuit to the head end of the stick cylinders.


Illustration 81

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81 Hydraulic System Systems Operation Section Hydraulic schematic for STICK IN (slow without regeneration) (1) Stick cylinder (2) Line (oil flow to stick cylinder rod end) (3) Line (oil flow from stick cylinder head end) (4) Valve (5) Stick drift reduction valve (6) Main control valve (9) Passage (10) Return passage (11) Return passage (12) Center bypass passage (13) Stick II control valve (15) Load check valve (16) Check valve (18) Center bypass passage (19) Check valve (21) Stick I control valve (22) Parallel feeder passage (23) Return line (27) Pilot control valve (stick and swing) (28) Drive pump (29) Idler pump (30) Pilot pump (31) Stick regeneration valve (32) Stick unloading valve (33) Pilot line (34) Pilot line (35) Pilot line (36) Pilot line (37) Passage (38) Pilot line (39) Pilot line (40) Pressure reducing valve for boom priority (41) Pilot line (42) Line (43) Passage (44) Passage (45) Passage (46) Passage (47) Passage (48) Check valve

When the stick is slowly moved in, the pilot pressure does not shift stick II control valve (13) and the pilot pressure does not shift stick regeneration valve (31).


Stick Regeneration Valve

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Illustration 82 Stick regeneration valve (6) Main control valve (9) Passage

(31) Stick regeneration valve (38) Pilot line

The stick hydraulic circuit contains a regeneration circuit. This regeneration circuit allows the return oil from the rod end of the stick cylinder to be supplied to the head end of the stick cylinder during the STICK IN operation. When the joystick for the stick is moved to the STICK IN position, pilot oil flow from the pilot control valve (stick and swing) flows through pilot line (38). Stick regeneration valve (31) shifts downward. The return oil from the rod end of the stick cylinder flows through passage (43) and through the throttling slots on valve (31) to check valve (48). Check valve (48) opens and the return oil flows through passage (9). The return oil from the rod end of the stick cylinder in passage (9) combines with the oil delivery from the idler pump and the drive pump. This combined oil flow now flows into the head end of the stick cylinder.

(43) Passage (48) Check valve


Stick Unloading Valve

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Illustration 83 Stick unloading valve (6) Main control valve (9) Passage (31) Stick regeneration valve (32) Stick unloading valve

(38) (43) (44) (46)

Pilot line Passage Passage Passage

Stick unloading valve (32) works in conjunction with stick regeneration valve (31) in order to relieve high pressure in the head end of the stick cylinder during a STICK IN operation. When the joystick for the stick is moved to the STICK IN position, pilot oil flow from the pilot control valve (stick and swing) flows through pilot line (38). Stick regeneration valve (31) shifts downward. The return oil from the rod end of the stick cylinder flows through passage (43) and through the throttling slots on valve (31) to check valve (48). Check valve (48) opens and the return oil flows through passage (9). The return oil from the rod end of the stick cylinder in passage (9) combines with the oil delivery from the idler pump and the drive pump. This combined oil flow now flows into the head end of the stick cylinder.

(47) Passage (49) Passage (50) Spring

Because of the volume of oil that is forced into the head end of the stick cylinder during the regeneration cycle of the STICK IN operation, the pressure of the oil in the head end of the stick cylinder increases. The high pressure oil flows through passage (9) and passage (44). The high pressure oil now acts on the end of stick unloading valve (32). When the force of the high pressure oil becomes greater than the force of spring (50), the stick unloading valve shifts downward. The return oil from the rod end of the stick cylinder in passage (43) flows past the throttling slots on stick regeneration valve (31), through passage (49), through stick unloading valve (32) and passage (47) and into the return circuit to the hydraulic tank. The return oil from the rod end of the stick cylinder is quickly unloaded. At this time, the regeneration circuit for the stick cylinder is inoperable.

84 Hydraulic System Systems Operation Section When the oil pressure at the head end of the stick cylinder decreases, the oil pressure that acts on the end of stick unloading valve (32) also decreases. The force of spring (50) shifts the stick unloading valve upward. The return oil from the rod end of the stick cylinder is supplied to the head end of the stick cylinder. The regeneration circuit is again operable. i01310189

Stick Drift Reduction Valve SMCS Code: 5143-JJ The stick drift reduction valve is placed in the stick circuit between the main control valve and the stick cylinder. When the joystick for the stick is in the NEUTRAL position, the stick drift reduction valve stops oil leakage from the rod end of the stick cylinder. Stopping oil leakage prevents stick drift.


Stick Out

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Illustration 84 Stick drift reduction valve (STICK OUT) (1) (2) (3) (4)

Passage Valve Spring Spring chamber

(5) (6) (7) (8)

Passage Port Port Port

When the joystick is moved to perform a STICK OUT operation, pilot oil is not sent from the pilot control valve to port (15) of stick drift reduction valve (16). Spool (11) does not shift. The oil flow from the stick II control valve enters port (6) of the stick drift reduction valve. The oil flow from the stick I control valve enters port (7) of the stick drift reduction valve. The combined oil flow from ports (6) and (7) flows into passage (1). As the oil pressure in passage (1) increases, valve (2) shifts against the force of spring (3). The oil in spring chamber (4) flows through passages (5) and (9) to port (8). The oil delivery in passage (1) now flows through port (8) to the rod end of the stick cylinder.

(9) Passage (11) Spool (15) Port (16) Stick drift reduction valve


Stick In

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Illustration 85 Stick drift reduction valve (STICK IN) (1) (2) (3) (4) (5) (6) (7) (8)

Passage Valve Spring Spring chamber Passage Port Port Port

(11) Spool (13) Drain line (15) Port (16) Stick drift reduction valve (18) Port (20) Spring chamber (21) Passage (22) Plug

When the joystick is moved to perform a STICK IN operation, pilot oil is sent from the pilot control valve to port (15) of stick drift reduction valve (16). Spool (11) shifts downward until the spool contacts plug (22). The oil in spring chamber (4) flows through passage (5), the orifice in spool (11), spring chamber (20), passage (21), port (18) and drain line (13) to the hydraulic tank. The return oil from the stick cylinder rod end enters port (8). Since the pressure in spring chamber (4) is low, the oil in port (8) shifts valve (2) against the force of spring (3). The oil from the rod end of the stick cylinder flows through port (8), passage (1) and passage (7) to the stick I control valve.

Bucket System i01631102

Bucket Hydraulic System SMCS Code: 5050-YB



Illustration 86

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89 Hydraulic System Systems Operation Section Since the spool in the bucket control valve is fully shifted, center bypass passage (8) is blocked. None of the oil delivery from the idler pump flows to negative flow control orifice (14) and no negative flow control pressure is created in center bypass passage (8). Since no negative flow control pressure is sent through negative flow control line (19) to the idler pump regulator, the idler pump regulator moves the swashplate of the idler pump toward the maximum angle position. The output flow rate of the idler pump is increased and flows through parallel feeder passage (16), load check valve (12), bucket control valve (9) and line (3) to the head end of bucket cylinder (4).

(1) Pilot line (2) Line (3) Line (4) Bucket cylinder (5) Main control valve (6) Return line (7) Center bypass passage (8) Center bypass passage (9) Bucket control valve (10) Spring (11) Orifice (12) Load check valve (13) Spring (14) Negative flow control orifice (15) Pilot control valve (boom and bucket) (16) Parallel feeder passage (17) Return passage (18) Pilot line (19) Negative flow control line (20) Pilot oil manifold (21) Drive pump (22) Idler pump (23) Pilot pump

Since the oil delivery for the bucket hydraulic circuit is supplied by the idler pump only, the negative control pressure in center bypass passage (7) is high. Drive pump (21) remains at the destroked position.

The oil delivery for the bucket hydraulic circuit is supplied by idler pump (22) only.

Reference: For more information concerning the negative flow control operation, refer to Systems Operation, “Negative Flow Control”. The return oil from the rod end of the bucket cylinder flows through line (2), orifice (11) in bucket control valve (9), return passage (17) and return line (6) to the hydraulic tank. Orifice (11) restricts the return oil from the rod end of the bucket cylinder. The BUCKET OPEN operation is similar to the BUCKET CLOSE operation.

Illustration 87

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(9) Bucket control valve

The oil delivery from idler pump (22) flows through center bypass passage (8) in main control valve (5) to bucket control valve (9). The oil delivery from drive pump (21) flows through center bypass passage (7) in main control valve (5). Illustration 86 shows the main control valve when only the bucket hydraulic circuit is activated. When the hydraulic activation control lever is in the UNLOCKED position, the oil delivery from pilot pump (23) flows through pilot oil manifold (20) to pilot control valve (15). When the joystick for the bucket is moved to the BUCKET CLOSE position, pilot oil flows through pilot control valve (15) and pilot line (1) to bucket control valve (9). The pilot oil pressure shifts the spool in the bucket control valve against spring (13). The pilot oil on the other end of the spool in the bucket control valve flows through pilot line (18) and pilot control valve (15) to the hydraulic tank.

When the joystick for the bucket is moved to the BUCKET OPEN position, pilot oil flow from pilot control valve (15) flows through pilot line (18) to the bucket control valve. The spool in the bucket control valve shifts against the force of spring (10). The oil delivery from the idler pump now flows to the rod end of the bucket cylinder. When the joystick for the bucket is in the NEUTRAL position, springs (10) and (13) maintain the spool in the bucket control valve in the NEUTRAL position. The oil flow from the head end and the rod end of the bucket cylinder is blocked.


Cylinders i01468748

Cylinders (Boom, Stick and Bucket) SMCS Code: 7562

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Illustration 88 (1) (2) (3) (4) (5)

Rod end port Head end port Boom cylinder Tube Rod

(6) Snubber (7) Piston (8) Stick cylinder (9) Snubber (10) Bucket cylinder


Travel System i01645775

Travel Hydraulic System SMCS Code: 5050

Travel Control

Illustration 89

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Snubber operation (6) Snubber (11) Passage

When boom cylinders (3) or stick cylinder (8) moves close to the end of the extension stroke, passage (11) is restricted by snubber (6). The movement of the piston rod slows down before the piston rod stops. Illustration 91

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(1) Left travel motor (52) Travel brake valve

Illustration 90

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Snubber operation (retracting rod) (9) Snubber (12) Passage

Illustration 92

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Final drive

When stick cylinder (8) moves close to the end of the retraction stroke, passage (12) is restricted by snubber (9). The movement of the piston rod slows down before the piston rod stops. The shock load is absorbed when the piston is slowed down.

(53) Track (54) Sprocket (55) Final drive

The output flow from the idler pump flows through the swivel to the right travel motor. The output flow from the drive pump flows through the swivel to the left travel motor. The pump delivery flow causes rotation of the travel motors. The torque of the travel motors is transmitted to the final drives. The rotational speed of the travel motors is reduced by gear reduction in the final drive. Final drive (55) increases the torque and the rotational force drives track (53) via sprocket (54).


Illustration 93

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Keypad (right console) (56) Travel speed control switch

The travel speed can be adjusted by the slight operation of the travel levers/pedals. The travel speed can also be controlled by travel speed control switch (56). This changes the travel speed when the travel levers/pedals are moved to the maximum position. The travel speed control switch can be set at the LOW SPEED position or the HIGH SPEED position. When the travel speed control switch is set at the LOW SPEED position, the tortoise appears on the default message display of the monitor. When the travel speed control switch is set at the HIGH SPEED position, the rabbit appears on the default message display of the monitor. During travel on a flat surface or during gradual downhill travel, the travel speed is set at the HIGH SPEED position in order to realize increased mobility. When travel speed control switch (56) is set at the HIGH SPEED position, the pressure sensors for pump delivery pressure detect the change in pump load. If the pressure sensors detect a high load, the travel speed is automatically adjusted to LOW SPEED. If the pressure sensors detect a small load, the travel speed is automatically adjusted to HIGH SPEED.


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Illustration 94 Operation of travel (1) Left travel motor (15) Right travel motor (57) Forward travel

(58) Left travel lever/pedal (59) Idler (60) Right travel lever/pedal

The direction of travel is relative to the position of the lower structure. For normal travel, idler (59) is positioned in front of cab (61) and travel motors (1) and (15) to the rear of the cab. With the machine in the normal position of travel, move the travel levers/pedals (58) and (60) forward. The machine will travel in forward direction (57). This movement is called forward travel. When the travel levers/pedals (58) and (60) are moved toward the operator, the machine travels in reverse direction (62). This direction is called reverse travel. When cab (61) is rotated by 180 degrees, travel motors (1) and (15) are positioned in front of the cab. The direction of travel and the operation of the travel levers/pedals (58) and (60) are reversed from the normal travel direction. When the machine is in the normal position of travel and when one of the travel levers/pedals (58) or (60) is moved forward, the respective track travels forward. The machine turns because the stationary track acts as the pivot point. This is called a pivot turn. This machine will spot turn in order to change the travel direction of the machine in a narrow space. To complete a spot turn operation, move one travel lever/pedal to the rear and move the other travel lever/pedal forward at the same time. One track will travel to the rear and the other track will travel forward. The machine will spot turn around the center axis of the machine.

Forward Travel

(61) Cab (62) Reverse travel


Illustration 95

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95 Hydraulic System Systems Operation Section When both of the travel levers/pedals are operated, pilot system oil pressure flows from travel pilot control valve (44) through pilot lines (42) and (43) to left travel control valve (38) and right travel control valve (41). The pilot system oil pressure shifts the spools in both of the travel control valves in an upward direction. The travel control valves allow the oil delivery from the idler pump and the drive pump to flow to swivel (30). The swivel transfers the oil delivery from the rotating upper structure to the lines in the lower structure. The oil delivery flows to left travel motor (1) and right travel motor (15).

Hydraulic schematic for FORWARD TRAVEL (1) Left travel motor (2) Swashplate (3) Motor rotary group (4) Swashplate control piston (5) Passage (supply oil) (6) Brake pilot valve (7) Passage (8) Counterbalance valve (10) Parking brake (11) Passage (return oil) (12) Displacement change valve (13) Passage (14) Line (pilot system oil pressure) (15) Right travel motor (16) Swashplate (18) Passage (return oil) (20) Displacement change valve (21) Passage (supply oil) (22) Swashplate control piston (23) Passage (24) Passage (25) Passage (26) Passage (27) Line (pilot system oil pressure) (28) Line (return oil) (29) Line (supply oil) (30) Swivel (31) Line (supply oil) (32) Line (return oil) (33) Line (supply oil) (34) Line (return oil) (35) Passage (supply oil) (36) Passage (return oil) (37) Return passage (38) Left travel control valve (39) Passage (40) Center bypass passage (41) Right travel control valve (42) Pilot line (forward left travel) (43) Pilot line (forward right travel) (44) Travel pilot control valve (45) Return line (46) Pressure sensor for idler pump delivery (47) Pressure sensor for drive pump delivery (48) Travel speed solenoid valve (49) Drive pump (50) Idler pump (51) Pilot pump

Illustration 96 Main control valve (38) Left travel control valve (41) Right travel control valve

Note: The right and left travel controls function in the same manner. The explanation for the left travel control will be used to explain both the right and left travel controls. When the left travel lever/pedal is moved to the FORWARD TRAVEL position, pilot system oil pressure from travel pilot control valve (44) flows through pilot line (42) to left travel control valve (38). The spool in the left travel control valve shifts in an upward direction. The oil delivery from the drive pump in center bypass passage (40) flows through passage (39), left travel control valve (38), passage (35), line (33), swivel (30) and line (29) to left travel motor (1). The oil delivery from the drive pump enters left travel motor (1) and flows through counterbalance valve (8) and passage (5) to motor rotary group (3). At the same time, a portion of the oil delivery from the drive pump flows through passage (7) and brake pilot valve (6) to parking brake (10). The parking brake is released and the oil delivery from the drive pump causes the motor to rotate.

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LOW SPEED

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Illustration 97 Left travel motor (LOW SPEED) (1) Left travel motor (2) Swashplate (3) Motor rotary group (4) Swashplate control piston (5) Passage (supply oil) (8) Counterbalance valve (11) Passage (return oil)

(12) Displacement change valve (13) Passage (27) Pilot line (46) Pressure sensor (drive pump) (48) Travel speed solenoid valve (49) Drive pump (51) Pilot pump

When travel speed control switch (56) is set at the LOW SPEED position, an electrical signal is sent to engine and pump controller (C). The engine and pump controller does not energize travel speed solenoid valve (48) and pilot system oil pressure does not flow through pilot line (27) to displacement change valve (12). The spool in the displacement change valve does not shift. As a result, swashplate (2) is at the maximum displacement position. One rotation of motor rotary group (3) displaces a larger amount of oil flow. The rotational speed of the left travel motor decreases. The left track moves slowly and better traction is achieved.

(56) Travel speed control switch (58) Left travel lever/pedal (A) Indicator for HIGH SPEED (B) Indicator for LOW SPEED (C) Engine and pump controller

The return oil from motor rotary group (3) flows through passage (11), counterbalance valve (8), line (28) and swivel (30). The return oil then flows through line (34), passage (36), left travel control valve (38), return passage (37) and return line (45) to the hydraulic tank. Right travel motor (15) receives the oil delivery from the idler pump. The right travel motor functions in the same manner as the left travel motor in the LOW SPEED position.


HIGH SPEED

Illustration 98

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Illustration 99 Left travel motor (HIGH SPEED) (1) Left travel motor (2) Swashplate (3) Motor rotary group (4) Swashplate control piston (5) Passage (supply oil) (8) Counterbalance valve (11) Passage (return oil)

(12) Displacement change valve (13) Passage (27) Pilot line (46) Pressure sensor (drive pump) (48) Travel speed solenoid valve (49) Drive pump (51) Pilot pump

(56) Travel speed control switch (58) Left travel lever/pedal (A) Indicator for HIGH SPEED (B) Indicator for LOW SPEED (C) Engine and pump controller

98 Hydraulic System Systems Operation Section When travel speed control switch (56) is set at the HIGH SPEED position, an electrical signal is sent to engine and pump controller (C). Pressure sensors (46) and (47) also send an electrical signal to the engine and pump controller. If the travel load is light and when the pump delivery pressure is below a certain pressure, the engine and pump controller energizes travel speed solenoid valve (48). Pilot system oil pressure flows through travel speed solenoid valve (48) and line (27) to displacement change valve (12). The spool in the displacement change valve shifts. A portion of the oil delivery from the drive pump flows through the displacement change valve to swashplate control piston (4). Swashplate control piston (4) moves swashplate (2) to the minimum displacement position. One rotation of motor rotary group (3) displaces a smaller amount of oil flow. The rotational speed of the left travel motor increases. The left track moves at a faster speed. The return oil from motor rotary group (3) flows through passage (11), counterbalance valve (8), line (28) and swivel (30). The return oil then flows through line (34), passage (36), left travel control valve (38), return passage (37) and return line (45) to the hydraulic tank. Right travel motor (15) receives the oil delivery from the idler pump. The right travel motor functions in the same manner as the left travel motor in HIGH SPEED position.

Automatic Travel Speed Change

Pressure sensor (46) monitors the delivery pressure of the idler pump. Pressure sensor (47) monitors the delivery pressure of the drive pump. The motor displacement is low when the travel speed control switch is set at the HIGH SPEED position and the travel load is light. As the pump load increases, the delivery pressure of the pumps increases. When the delivery pressure of the pumps reaches a certain pressure, the pressure sensor sends an electrical signal to the engine and pump controller. The engine and pump controller de-energizes travel speed solenoid valve (48). Travel speed solenoid valve (48) blocks the flow of pilot system supply oil to displacement change valves (12) and (20). The oil in swashplate control pistons (4) and (22) now flows into the case drain of the travel motors. Swashplates (2) and (16) move to the maximum displacement position. One rotation of the motor rotary groups in the travel motors displaces a larger amount of oil flow. The rotational speed of the travel motors decreases. The travel speed is automatically changed to LOW SPEED. When the pump load decreases and the travel speed control switch is set at the HIGH SPEED position, pressure sensors (46) and (47) will now cause the engine and pump controller to energize travel speed solenoid valve (48). Displacement change valves (12) and (20) will be shifted by pilot pressure so that the motor rotary groups will change to the minimum displacement position. One rotation of the motor rotary groups displaces a small amount of oil flow. The travel speed will automatically change to HIGH SPEED. The ability of the machine to automatically change the travel speed allows good performance at high speed and better traction control. i01323204

Pilot Valve (Travel and Steering) SMCS Code: 5462

Illustration 100 Main pump compartment (46) Pressure sensor for idler pump delivery (47) Pressure sensor for drive pump delivery

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Illustration 101 Travel pilot control valve (1) Travel lever/pedal (2) Pedal (3) Rod (4) Seat (5) Spring (6) Spring (7) Spool (8) Passage (9) Passage (10) Spring (11) Spool (12) Return port

(13) Return chamber (14) Passage (15) Passage (16) Pilot port (17) Passage (18) Port (19) Passage (20) Passage (21) Passage (22) Port (23) Piston chamber (24) Orifice

When travel lever/pedal (1) is moved to the FORWARD TRAVEL position, rod (3) moves downward. As rod (3) moves downward, seat (4) moves downward against the force of springs (5) and (6). Passage (19) opens.

(25) Piston (26) Spring (27) Spring (28) Spring chamber (29) Ball (30) Rod (31) Spring (32) Spring (33) Spring chamber (34) Ball

As passage (19) opens, the pilot oil from pilot port (16) flows through passages (21), (19), (20), and (9) to port (18). The pilot oil flows through port (18) to the travel control valve. The pilot oil pressure shifts the spool of travel control valve. The oil delivery from the pump now flows through the travel control valve to the travel motor. The travel motor rotates. The machine travels forward.

100 Hydraulic System Systems Operation Section The return pilot oil at the opposite end of the spool in the travel control valve returns to the travel pilot control valve through port (22). Since spool (11) is pushed upward by the force of spring (10), the return pilot oil flows through passage (17), passage (15), passage (14), return chamber (13) and port (12) to the hydraulic tank. When travel lever/pedal (1) is moved slightly from the NEUTRAL position for fine travel, rod (3) moves downward and seat (4) moves downward. Spring (6) forces spool (7) downward. Passage (19) opens slightly and the pilot oil pressure increases in port (18). When this pilot oil pressure becomes higher than the force of spring (6), spool (7) moves upward opening passage (8). The pilot pressure oil from port (18) flows through passages (9), (20) and (8) into return chamber (13). The pilot oil pressure decreases slightly. Spool (7) is held in a pressure modulating position. Spool (7) establishes a balance between the pressure in port (18) and the force of spring (6). When travel lever/pedal (1) is released, spring (5) forces seat (4) and rod (3) in an upward direction. The force of spring (6) decreases. Spool (7) moves upward. The pilot oil pressure at port (18) flows through passage (9), passage (20), passage (8) and return chamber (13) to the hydraulic tank. A dampening function is built into the travel pilot control valve which allows the operational speed of the travel lever/pedal to correspond to the movement of the operator’s foot. The dampening function also prevents the vibration that occurs when the travel lever/pedal is released. When travel lever/pedal (1) is moved suddenly from the NEUTRAL position, rod (3) is pushed downward. Rod (3) moves piston (25), spring (26) and spring (27) downward. The hydraulic oil in spring chamber (28) is pressurized. Ball (29) closes the opening. Orifice (24) allows the confined hydraulic oil in spring chamber (28) to gradually flow into piston chamber (23). The gradual flow of oil through orifice (24) causes the dampening function. Rod (30) is forced upward by springs (31) and (32). The oil pressure in spring chamber (33) decreases. The return oil pressure in return chamber (13) forces ball (34) upward. The return oil in return chamber (13) now flows from return chamber (13) into spring chamber (33). As a result, rod (30) follows the movement of pedal (2). When travel lever/pedal (1) is moved slightly from the NEUTRAL position for fine control, rod (3) is pushed down slowly. As a result, the oil pressure in spring chamber (28) becomes equal to the oil pressure in piston chamber (23). At this point, the dampening function is weak.

Travel lever/pedal (1) operates the same way in the REVERSE TRAVEL position. i01631105

Travel Motor SMCS Code: 79PC-QP


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Illustration 102 Travel motor (1) Drive shaft (4) Swashplate (5) Slipper (6) Retainer (7) Barrel (8) Passage (9) Check valve (10) Check valve (11) Passage (12) Brake pilot valve (13) Port

(14) Valve plate (15) Head (16) Stopper (17) Piston (18) Guide (19) Spacer (20) Spring (21) Piston (22) Friction plate (23) Separator plate (24) Passage

(25) Passage (26) Brake spring (27) Brake piston (28) Pilot Port (29) Drain port (30) Port (31) Port (32) Spool (33) Spring (34) Displacement change valve


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Illustration 103 Travel motor (partial schematic) (4) Swashplate (9) Check valve (10) Check valve (12) Brake pilot valve (17) Piston

(28) Pilot Port (29) Drain port (30) Port (31) Port (34) Displacement change valve

The travel motor can be divided into the following three groups:

• The rotary group consists of the following components: drive shaft (1), slippers (5), retainer (6), barrel (7), guide (18), spacer (19), spring (20), and piston (21).

The flow of the oil delivery from the pump depends on the direction of travel. The oil delivery from the pump flows into the travel motor through port (30) or port (31). Pump oil is forced out of the travel motor through port (31) or (30). The case drain oil returns to the hydraulic tank through drain port (29) of head (15).

• The parking brake consists of the following components: brake pilot valve (12), friction plates (22), separator plates (23), brake spring (26), and brake piston (27).

• The displacement change valve consists of the

following components: check valve (9), check valve (10), piston (17), and displacement change valve (34).

The oil delivery from the drive pump flows into the left travel motor through port (30) during forward travel. The oil from port (30) flows through passage (11) in head (15) and through passage (25) in valve plate (14). The oil then flows through passage (24) of barrel (7) and the oil forces pistons (21) to move to the left.


Travel Parking Brake SMCS Code: 4267

Illustration 104

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Motor passage (side view from head) (A) Top center (B) Outlet side (low pressure) (C) Bottom center (D) Inlet side (high pressure) (24) Passage (barrel) (25) Passage (valve plate) (35) Passage (valve plate)

Slipper (5) is coupled to the piston. Slipper (5) and the piston slide on the surface of swashplate (4) from the top center to the bottom center. Slipper (5) and the piston rotate with barrel (7). Supply oil from the drive pump flows through passage (25) of valve plate (14) into pistons (21). The oil then flows through passage (35) of valve plate (14). Oil is discharged from piston (21) through passage (8). The oil then flows through port (31). The barrel turns counterclockwise. Drive shaft (1) is splined to barrel (7). The shaft and barrel of the left travel motor rotate counterclockwise for forward travel. In reverse travel, port (30) functions as an oil return port. Port (31) functions as a supply port. The left travel motor rotates clockwise. When the right travel motor receives the oil delivery from the idler pump through port (30), the right travel motor turns clockwise for forward travel. When the oil delivery from the idler pump flows through port (31), the right travel motor turns counterclockwise for reverse travel.

The travel parking brake is built into the travel motor. When the oil delivery from the pump flows to the travel motor, the parking brake releases and the travel motor starts rotating. When no oil delivery flows to the travel motor, the rotation of the travel motor stops and the travel parking brake engages. For more information concerning the operation of the travel motor, refer to Systems Operation, “Travel Motor ”.


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Illustration 105 Parking brake (parking brake engaged) (1) (2) (3) (4) (5) (6)

Brake pilot valve Port Drive shaft Head Passage Brake spring

(7) Housing (8) Barrel (9) Friction plate (10) Separator plate (12) Piston chamber (13) Brake piston

In the parking brake section of the travel motor, separator plates (10) are splined to housing (7). Friction plates (9) are splined to barrel (8).

(14) (15) (16) (17) (18)

Passage Spring Valve Retainer Orifice

When the travel lever/pedal is returned to the NEUTRAL position, the oil delivery from the pump is blocked at the travel control valve in the main control valve. Valve (16) moves to the right by the force of spring (15). The oil delivery from the pump does not flow through valve (16). The force of the oil pressure on the left side of brake piston (13) now becomes lower than the force of brake spring (6). The brake piston is pushed slowly to the left by the force of the brake spring. The oil in piston chamber (12) now flows through passage (14) and passage (5). The oil flows through orifice (18) and into the valve of the motor case drain line. Friction plates (9) and separator plates (10) are forced together by the force of brake spring (6). Friction plates (9) are splined to barrel (8). Separator plates (10) are splined to housing (7). When the separator plates and the friction plates are forced together, the rotation of drive shaft (3) in the travel motor gradually slows to a stop as the parking brake engages.

105 Hydraulic System Systems Operation Section Orifice (18) restricts return oil flow from piston chamber (12). The restriction of the return oil flow delays the application of the parking brake. The parking brake is delayed in order to give the machine time to stop. Earlier wear and/or damage to the machine could result if the machine stayed in motion.

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Illustration 106 Parking brake (brake released) (1) (2) (3) (4) (5) (6)

Brake pilot valve Port Drive shaft Head Passage Brake spring

(7) Housing (8) Barrel (9) Friction plate (10) Separator plate (12) Piston chamber (13) Brake piston

When a travel lever/pedal is moved from the NEUTRAL position, the oil delivery from the pump flows to the inlet port of the travel motor from the travel control valve in the main control valve. A portion of the oil delivery from the pump flows through port (2). Valve (16) moves to the left against the force of spring (15). The oil then flows through passages (5) and (14) to piston chamber (12). Brake piston (13) moves to the right against the force of brake spring (6). The spring force that is holding friction plates (9) and separator plates (10) together is released. Barrel (8) and drive shaft (3) start to rotate.

(14) (15) (16) (17) (18)

Passage Spring Valve Retainer Orifice


Displacement Change Valve SMCS Code: 3220

Small Displacement Change Operation

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Illustration 107 Travel motor (partial diagram) (1) Check valve (2) Check valve (3) Pilot port (4) Displacement change valve

(5) Passage (6) Piston chamber (7) Port (supply oil or return oil) (8) Piston

(9) Swashplate (10) Port (supply oil or return oil) (11) Drain port


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Illustration 108 Small displacement change operation (1) Check valve (2) Check valve (3) Pilot port (4) Displacement change valve (6) Piston chamber (7) Port (supply oil or return oil)

(8) Piston (9) Swashplate (10) Port (supply oil or return oil) (12) Passage (13) Passage (return) (14) Hydraulic tank

When the travel speed control switch on the control panel is pushed and the rabbit appears on the display, the machine is in HIGH SPEED MODE. In this condition, an input signal from the travel speed control switch is sent to the engine and pump controller. The pressure sensor for the pump delivery also provides an input signal to the engine and pump controller. When the travel load is light and when the pump delivery pressure is below a certain level, the output signal from the pressure sensor for the pump delivery is below a certain level. When the pump delivery pressure is below a certain level, the engine and pump controller energizes the travel speed solenoid. When the travel speed solenoid is energized, pilot system oil flows into pilot port (3) of displacement change valve (4). Spool (16) moves to the left against the force of spring (17) until the spool contacts body (18). Main pump oil flows from port (10) of the travel motor through check valve (2). The main pump oil then flows through spool chamber (15) and passage (12) to piston chamber (6). The oil in piston chamber (6) moves piston (8) against swashplate (9). As a result, the angle of swashplate (9) is decreased and the motor displacement is decreased. The travel speed is maximum in this condition.

(15) Spool chamber (16) Spool (17) Spring (18) Body


Large Displacement Change Operation

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Illustration 109 Large displacement change operation (1) Check valve (2) Check valve (3) Pilot port (4) Displacement change valve (6) Piston chamber (7) Port (supply oil or return oil) (8) Piston (9) Swashplate

(10) Port (supply oil or return oil) (12) Passage (13) Passage (return) (14) Hydraulic tank (15) Spool chamber (16) Spool (17) Spring (18) Body

When the angle of swashplate (9) in the travel motor increases, the displacement of the travel motor increases. The angle of swashplate (9) in the travel motor will increase and the travel speed will decrease during the following two conditions. 1. The angle of swashplate (9) in the travel motor will increase and the travel speed will decrease when an increase in pump pressure occurs.

When the machine is in HIGH SPEED MODE and the pump delivery pressure increases above a certain level, the engine and pump controller de-energizes the travel speed solenoid. When the travel speed solenoid is de-energized, pilot system oil stops flowing into pilot port (3) of displacement change valve (4). Spool (16) moves to the right by the force of spring (17) until the spool contacts the stopper. Oil from port (10) of the travel motor is blocked from passage (12). The oil is forced from piston chamber (6) through passage (12) and return passage (13) to hydraulic tank (14). As the angle of swashplate (9) increases, the displacement of the travel motor increases and the travel speed decreases. 2. The angle of swashplate (9) in the travel motor will increase and the travel speed will decrease when the travel speed control switch is pushed in order to obtain LOW SPEED MODE.

109 Hydraulic System Systems Operation Section When the travel speed control switch on the control panel is pushed and the tortoise appears on the display, the machine is in LOW SPEED MODE. In this condition, an input signal from the travel speed control switch is sent to the engine and pump controller. The engine and pump controller de-energizes the travel speed solenoid. The angle of swashplate (9) increases and the displacement of the travel motor increases. The travel speed decreases. i01638159

Travel Counterbalance Valve SMCS Code: 5051-KV

Illustration 110

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Left travel motor and travel counterbalance valve (1) Crossover relief valve (reverse travel) (16) Crossover relief valve (forward travel) (24) Port (supply port for forward travel) (27) Port (supply port for reverse travel) (33) Counterbalance valve (35) Travel counterbalance valve (36) Left travel motor

Travel counterbalance valve (35) consists of counterbalance valve (33), crossover relief valve (1) and crossover relief valve (16). The travel counterbalance valve is bolted to the travel motor. The travel counterbalance valve has the following four functions.

• The travel counterbalance valve prevents a shock load when travel is stopped.

• The travel counterbalance valve prevents

overspeed while the machine is travelling down a slope.

• The travel counterbalance valve prevents cavitation.

• The travel counterbalance valve routes a portion of the oil to the travel parking brake in order to release the brake.


Counterbalance Valve Operation During Level Travel

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Illustration 111 Travel counterbalance valve (level travel) (1) Crossover relief valve (reverse travel) (2) Passage (3) Valve (4) Passage (5) Passage (6) Passage (7) Passage (8) Valve (9) Spool (10) Spring (11) Passage

(12) Spring (13) Spring (14) Damper Spool (15) Ball (16) Crossover relief valve (forward travel) (17) Passage (18) Spring chamber (19) Passage (20) Damper Chamber (21) Orifice (22) Passage

(23) Check valve (24) Port (supply port for forward travel) (25) Passage (26) Passage (27) Port (supply port for reverse travel) (28) Check valve (29) Passage (30) Spring (32) Passage (33) Counterbalance valve (35) Travel counterbalance valve

111 Hydraulic System Systems Operation Section Counterbalance valve (33) consists of spool (9), check valve (23), check valve (28), spring (13) and spring (30). During forward travel on level ground, pump oil is supplied to port (24). The oil flows through port (24), passage (25), and check valve (23). The oil flow forces check valve (23) to open. This allows oil to flow through port (24), passage (25), check valve (23), passage (2), and the port to the rotary group of the travel motor. A portion of the oil delivery from the drive pump in port (24) flows through passage (22) and passage (17) against ball (15). Ball (15) moves to the right against the force of spring (12) in damper spool (14). The oil delivery then flows through passage (19) into spring chamber (18). The oil pressure in damper chamber (20) acts on the end of spool (9). Spool (9) shifts to the right against the force of spring (30). Passage (7) opens. As spool (9) shifts to the right, return oil from the travel motor flows through the port, passage (7), passage (26), and port (27) to the hydraulic tank. When the oil flow from port (24) is blocked, the pressure in damper chamber (20) decreases. The force of spring (30) shifts spool (9) to the left. Passage (7) closes. Return oil from the travel motor is blocked and the rotation of the travel motor stops. When the direction of travel is reversed, pump oil flows to spool (9) through port (27). Spool (9) shifts to the left. The return oil flows through port (24). During reverse travel, the travel counterbalance valve operates in the same manner as the forward travel operation.


Counterbalance Valve Operation During Slope Travel

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Illustration 112 Travel counterbalance valve (slope travel) (1) Crossover relief valve (reverse travel) (2) Passage (3) Valve (4) Passage (5) Passage (6) Passage (7) Passage (8) Valve (9) Spool (10) Spring (11) Passage



113 Hydraulic System Systems Operation Section When the machine travels down a slope, the travel motors rotate at a higher speed. The higher speed is due to the mass (weight and size) of the machine. When this condition occurs, the pumps cannot maintain the oil supply to the travel motors. The lack of oil supply will cause cavitation in the travel motor. A pressure decrease occurs at port (24). A pressure decrease occurs in spring chamber (18) as well. The force of spring (30) moves spool (9) to the left. Passage (7) begins to close. This blocks oil flow between passage (7) and passage (26). The return oil from the travel motor and the oil flow to the suction port of the travel motor are restricted. The rotation of the travel motor slows down. The pressure of the oil delivery from the drive pump at port (24) increases. Part of the oil flows through passage (17). Spool (9) shifts to the right. Passage (7) opens. Return oil from the travel motor flows through port (27). The modulation of spool (9) maintains the proper opening of passage (7) when the machine travels down a slope. The travel motor begins to rotate in accordance with the amount of pump oil supply. This prevents cavitation in the travel motors. When the machine is travelling down a slope, or the machine is suddenly stopped, spool (9) suddenly closes passage (7). This causes a hydraulic pressure spike to occur. A damper is provided at both ends of spool (9) in order to prevent hydraulic pressure spikes. As spool (9) shifts to the left, the oil in damper chamber (20) is pressurized. Ball (15) moves to the left. The oil in spring chamber (18) flows through orifice (21) and into passage (22). Spool (9) slowly moves to the left. Passage (7) slowly closes. The size and the position of orifice (21) maintains the proper shock damper.


Operation Of Travel Crossover Relief Valves During Machine Stop

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Illustration 113 Travel counterbalance valve (travel stop) (1) Crossover relief valve (reverse travel) (2) Passage (3) Valve (4) Passage (5) Passage (6) Passage (7) Passage (8) Valve (9) Spool (10) Spring (11) Passage



115 Hydraulic System Systems Operation Section If the travel levers/pedals are returned to the NEUTRAL position during machine movement, the oil delivery from the pumps is blocked from the travel motors. The pressure at port (24) of the travel counterbalance valve decreases. The force of spring (30) moves spool (9) to the left to the neutral position. The mass (weight and size) of the machine causes the travel motor to continue to rotate. Passage (7) is closed and the flow of return oil is blocked. A sudden pressure increase occurs in passage (11). The return oil in passage (11) flows through passage (6) to crossover relief valve (1). Valve (3) shifts to the left. The return oil in passage (6) flows past the open valve (3) into suction passage (2) of the travel motor.

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Illustration 114 Travel crossover relief valve (3) Valve (2) Passage (6) Passage (39) Body

(40) (41) (42) (43)

Orifice Orifice Orifice Stem

The return oil pressure in passage (6) flows through orifice (41) in valve (3). The oil then flows through orifices (40) and (42) in stem (43). The return oil now flows through passage (44). Shock reducing piston (45) shifts to the right. The travel crossover relief valve maintains the circuit pressure at a lower pressure until the right end of shock reducing piston (45) contacts stem (43). When the shock reducing piston is fully shifted to the right, the oil pressure in passage (6) increases to the pressure setting of the crossover relief valve. All of the oil flow in passage (6) now flows past valve (3) into return passage (2). The oil pressure gradually increases until the shock reducing piston shifts fully to the right. Pressure spikes in the travel circuit are eliminated. This is called a two-stage relief operation. The two-stage relief operation absorbs the shock load at the stop of a travel operation.

(44) Passage (45) Shock reducing piston

During forward travel of the left travel motor, oil flow opens crossover relief valve (1) when the machine is stopping. During reverse travel of the left travel motor, crossover relief valve (16) is activated when the machine is stopping. Crossover relief valves (1) and (16) protect the travel motor by releasing the high pressure oil. Crossover relief valves (1) and (16) also provide makeup oil from the outlet side of the travel motor to the inlet side of the travel motor. This makeup oil prevents a vacuum condition in the travel motor. In order to adjust the pressure setting of the crossover relief valves, refer to the crossover relief valves by the functions of the travel control levers. Refer to crossover relief valve (16) as left travel (forward). Refer to crossover relief valve (1) as left travel (reverse).

116 Hydraulic System Systems Operation Section Reference: For more information concerning the pressure settings of the travel crossover relief valves, refer to Testing and Adjusting, “Relief Valve (Crossover) - Test and Adjust”.

i01631110

Oil Makeup (Travel System) SMCS Code: 5080

Travel Parking Brake Operation When the oil delivery from the drive pump at port (24) of the travel counterbalance valve is blocked, spool (9) moves to the right. Passage (4) opens. A portion of the oil delivery in passage (25) flows through passage (4) and passage (32) in order to release the travel parking brake. Since passage (4) opens before passage (7), the rotation of the motor rotary group does not start until the travel parking brake is released. When the oil delivery to port (24) is blocked in order to stop the rotation of the travel motor, spool (9) returns to the NEUTRAL position. Passage (4) closes after passage (7) closes. This allows the movement of the machine to stop before the travel parking brake is engaged. Reference: For more information concerning the operation of the travel parking brake, refer toSystems Operation, “Travel Parking Brake”.

Illustration 115

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Oil makeup operation (1) Motor rotary group (2) Left travel motor (3) Passage (4) Check valve (5) Line (6) Swivel (7) Line (8) Passage (9) Left travel control valve (10) Passage (11) Return passage

In order to prevent cavitation in the travel motor during travel stop, makeup oil is supplied to the travel motor. The following description is given for travel stop of the left travel motor. The right travel motor functions in the same manner as the left travel motor.

117 Hydraulic System Systems Operation Section During travel stop, the travel levers/pedals are moved to the NEUTRAL position. The oil delivery from the drive pump through passage (8) is blocked at travel control valve (9). The oil delivery from the drive pump is not supplied to the left travel motor. Since no oil delivery is supplied to left travel motor (2), the travel motor will attempt to stop. However, the travel motor will continue to rotate because of the inertia (weight and size) of the machine. This causes a vacuum condition in passage (3) of the travel motor. When travel control valve (9) is in the NEUTRAL position, return oil flows from return passage (11) through passage (8). The return oil then flows through line (7), swivel (6), line (5), check valve (4) and passage (3) to motor rotary group (1) as makeup oil. This makeup oil prevents cavitation in the travel motor during travel stop. Makeup oil is supplied for forward travel in the same manner as reverse travel. i01631113

Final Drive SMCS Code: 4050


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Illustration 116 Final Drive (1) Roller bearing (2) Planetary shaft (second stage) (3) Bolt (4) Planetary gear (second stage) (5) Roller bearing (6) Planetary gear (third stage) (7) Roller bearing (8) Planetary shaft (third stage) (9) Drive sprocket housing

(10) Motor housing (11) Travel motor (12) Planetary gear (first stage) (13) Planetary shaft (first stage) (14) Cover (15) Sun gear (first stage) (16) Planetary carrier (first stage) (17) Ring gear (first stage) (18) Planetary carrier (second stage)

The final drive reduces the rotational speed of travel motor (11). Output shaft (23) of travel motor (11) is splined to sun gear (first stage) (15). The final drive consists of two groups. The first group consists of the three stages of the planetary gear reduction. The second group is the output group.

(19) Sun gear (second stage) (20) Ring gear (second stage and third stage) (21) Planetary carrier (third stage) (22) Sun gear (third stage) (23) Output shaft (travel motor) (26) Roller bearing

• The first stage reduction group consists of the following components: sun gear (15), planetary gear (12), planetary carrier (16), and ring gear (17). The group for second stage reduction consists of the following components: sun gear (19), planetary gear (4), planetary carrier (18), and ring gear (20). The third stage reduction group consists of the following components: sun gear (22), planetary gear (6), planetary carrier (21), and ring gear (20).


• The output group is described in the following

manner. The rotation of drive sprocket housing (9) drives the track. Drive sprocket housing (9), ring gear (20) and cover (14) are connected by bolts (3). The drive sprocket housing, the ring gear and the cover are supported by roller bearing (26). This planetary assembly rotates with ring gear (20).

The planetary gears reduce the travel speed. The travel speed is reduced by the ratio of teeth of the sun gear and the ring gear. The compact final drive offers a greater reduction ratio when the sun gear is incorporated inside the ring gear.

Operation Sun gear (15) is splined to the output shaft of travel motor (23). The rotation of the output shaft is transmitted to the sun gear. When sun gear rotates clockwise, the final drive operates in the following manner.

Illustration 118

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Engagement of splines (12) Planetary gear (first stage) (13) Planetary shaft (first stage) (16) Planetary carrier (first stage) (19) Sun gear (second stage) (28) Engagement of splines

The spline of planetary carrier (first stage) (16) meshes with sun gear (second stage) (19). The rotation of planetary carrier (16) is transmitted to sun gear (19). Sun gear (19) rotates clockwise. In the group for second stage reduction, sun gear (19) causes planetary gears (4) to rotate counterclockwise. Planetary gears (4) mesh with sun gear (19) and ring gear (20). Planetary gears (4) rotate around sun gear (9) and the internal teeth of ring gear (20). Each planetary gear (4) is mounted to planetary carrier (18) by shafts (2) and by roller bearings (5) in order to form a planetary assembly. Planetary carrier (18) rotates clockwise. Illustration 117

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First stage reduction group (1) Roller bearing (first stage) (12) Planetary gear (first stage) (13) Planetary shaft (first stage) (15) Sun gear (first stage) (16) Planetary carrier (first stage) (17) Ring gear (first stage) (27) Rotational direction (first stage reduction group)

In the first stage reduction group, sun gear (15) causes planetary gears (12) to rotate counterclockwise. Planetary gears (12) mesh with sun gear (15) and ring gear (17). Planetary gears (12) rotate around sun gear (15) and the internal teeth of ring gear (17). Each planetary gear (12) is mounted to planetary carrier (16) by shafts (13) and by roller bearings (1) in order to form a planetary assembly. Planetary carrier (16) rotates in a clockwise direction (27).

Illustration 119 Engagement of splines (18) Planetary carrier (second stage) (22) Sun gear (third stage) (27) Engagement of splines

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120 Hydraulic System Systems Operation Section The spline of planetary carrier (second stage) (18) meshes with sun gear (third stage) (22). The rotation of planetary carrier (18) is transmitted to sun gear (22). Sun gear (22) rotates clockwise. In the third stage reduction group, the spline teeth of planetary carrier (21) mesh with teeth on the outer circumference of motor housing (10). Since motor housing (10) is fixed to the track frame, planetary carrier (21) does not rotate. Planetary shaft (8) is stationary. The planetary gear (third stage) (6) rotates around planetary shaft (8). Since planetary carrier (21 ) is attached to the track frame and the planetary carrier does not move, ring gear (20) rotates counterclockwise. Since ring gear (20) and drive sprocket housing (9) are held together with bolts (3), drive sprocket housing (9) rotates counterclockwise. This causes the right track to move in a forward direction. i01331085

Swivel SMCS Code: 5060


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Illustration 120 Swivel (1) (2) (3) (4) (5) (6) (7) (8)

Retainer Cover Drain port Drain hole Port Seal Port Port

(9) Housing (10) Port (11) Port (12) Flange (13) Seal (14) Rotor (15) Plate (16) Port

(17) Port (18) Port (19) Port (20) Port (21) Port (22) Swivel (23) Support (24) Front direction

122 Hydraulic System Systems Operation Section Table 2

Identification Of Port And Circuit Ports (Housing)

Ports (Rotor)

Circuit

7

18

Right travel (reverse)

10

21

Right travel (forward)

8

20

Left travel (forward)

5

17

Left travel (reverse)

3

19

Drain

11

16

Change of Travel speed

Swivel (22) accomplishes two functions. Swivel (22) supplies pump oil from the upper structure to the travel motors of the lower structure. The upper structure swings. The lower structure does not swing. Swivel (22) returns oil from the travel motors to the hydraulic tank. Housing (9) is restrained to the upper structure through support (23). Support (23) is used as a torque arm in order to prevent housing (9) from rotating. Rotor (14) is bolted to the lower structure through plate (15). The ports of housing (9) are open to the ports of rotor (14). The passages in housing (9) and the passages in rotor (14) connect the ports. Seal (6) for high pressure and seal (13) for low pressure are provided between the sliding surfaces of housing (9) and rotor (14). Seals (6) and (13) prevent oil leakage between the passages.

Swing System i01631116

Swing Hydraulic System SMCS Code: 5050



Illustration 121

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125 Hydraulic System Systems Operation Section Hydraulic schematic for SWING RIGHT (1) Pilot line (2) Passage (3) Swing parking brake (4) Swing motor (5) Motor rotary group (6) Relief valve (7) Anti-reaction valve (8) Return line (9) Line (10) Line (11) Passage (12) Load check valve (13) Parallel feeder passage (14) Main control valve (15) Parallel feeder passage (16) Passage (17) Passage (18) Swing control valve (19) Stick I control valve (20) Variable swing priority valve (21) Passage (22) Passage (23) Pilot control valve (swing and stick) (24) Pilot line (25) Implement/swing pressure switch (26) Line (27) Pressure reducing valve for swing priority (28) Drive pump (29) Idler pump (30) Pilot pump (31) Swing parking brake solenoid valve (32) Line (33) Slow return check valve (34) Hydraulic tank (35) Pilot oil manifold (36) Drain line (37) Pilot line (38) Pilot line (47) Line (48) Passage (49) Line (52) Center bypass passage (53) Center bypass passage (54) Negative flow control orifice (55) Negative flow control line

The oil delivery for the swing hydraulic circuit is supplied by drive pump (28) only. When either one of the joysticks (swing, stick, boom and/or bucket) is moved from the NEUTRAL position, swing parking brake (3) is released. Motor rotary group (5) starts to rotate. The swing motor is mounted on top of the swing drive. The swing drive is installed on the upper structure. The swing drive reduces the motor speed by two stages. The swing drive rotates the upper structure. Reference: For more information concerning the operation of the swing motor, refer to Systems Operation, “Swing Motor”. Reference: For more information concerning the operation of the swing drive, refer to Systems Operation, “Swing Drive”. Reference: For more information concerning the operation of the swing parking brake and the swing parking brake solenoid valve, refer to Systems Operation, “Pilot Valve (Swing Parking Brake)”.

Illustration 122

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Main control valve compartment (4) Swing motor (8) Return line (9) Line (10) Line (18) Swing control valve

Illustration 123

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(31) Swing parking brake solenoid valve (35) Pilot oil manifold

The oil delivery from drive pump (28) flows through center bypass passage (52) in main control valve (14) to swing control valve (18). The oil delivery from idler pump (29) flows through center bypass passage (53) in main control valve (14). Illustration 121 shows the main control valve when only the swing hydraulic circuit is activated. When the hydraulic activation control lever is in the UNLOCKED position, the oil delivery from pilot pump (30) flows to pilot oil manifold (35) and swing parking brake solenoid valve (31). The oil delivery from the pilot pump also flows to pilot control valve (23).

126 Hydraulic System Systems Operation Section When the swing joystick is moved to the SWING RIGHT position, the implement/swing pressure switch senses the increase in pilot oil pressure. The implement/swing pressure switch changes to the ON position. The implement/swing pressure switch sends an input signal to the engine and pump controller. The engine and pump controller then energizes swing parking brake solenoid valve (31). The swing parking brake solenoid valve shifts. Pilot oil flows through pilot line (1) to swing parking brake (3). The swing parking brake releases in order to enable a swing operation.

When the swing joystick is moved to the SWING LEFT position, pilot oil from pilot control valve (23) flows through pilot line (37) and into swing control valve (18). The spool in the swing control valve shifts downward. The oil delivery from the drive pump in parallel feeder passage (13) flows through passage (17) and line (10). The oil delivery enters motor rotary group (5). For a swing left operation, the supply ports and return ports are reverse of the swing right operation. This causes the upper structure to swing to the left (counterclockwise direction).

The oil delivery from pilot pump (30) flows from pilot control valve (23) through pilot line (26) and into swing control valve (18). The spool in swing control valve (18) shifts upward. The pilot oil on the other end of the spool in the swing control valve flows through pilot line (37) and pilot control valve (23) to hydraulic tank (34).

When the swing joystick is returned to the NEUTRAL position, the springs on each end of the swing control valve maintain the spool in the swing control valve in the NEUTRAL position. The oil flow to the swing motor and the oil flow from the swing motor is blocked by the swing control valve.

Since the spool in swing control valve (18) is fully shifted, center bypass passage (52) is blocked. None of the oil delivery from the drive pump flows to negative flow control orifice (54) and no negative flow control pressure is created in center bypass passage (52). Since no negative flow control pressure is sent through negative flow control line (55) to the drive pump regulator, the drive pump regulator moves the swashplate of the drive pump toward the maximum angle position. The output flow rate of the drive pump increases. The oil delivery from the drive pump flows through parallel feeder passage (13), load check valve (12), passage (17), swing control valve (18), passage (16) and line (9) to the swing motor. The oil enters the swing motor and flows to motor rotary group (5). The motor rotary group rotates. The oil delivery for the swing hydraulic circuit is supplied by the drive pump only. Since only a swing operation is being performed, the control valves that receive the oil delivery from idler pump (29) are in the NEUTRAL position. The negative flow control pressure in center bypass passage (53) is not blocked by any of the control valves. Idler pump (29) remains at the destroked position. Reference: For more information concerning the negative flow control operation, refer to Systems Operation, “Negative Flow Control”. Return oil from motor rotary group (5) flows through line (10) to the main control valve. The return oil flows through swing control valve (18), return passage (11), return line (8) and slow return check valve (33) to hydraulic tank (34). The upper structure swings to the right (clockwise direction). The SWING LEFT operation is similar to the SWING RIGHT operation.

Swing Priority The pilot oil pressure from the pilot control valve directly corresponds to the amount of movement or position of the joystick. The pilot oil pressure from the pilot control valve acts on the pressure reducing valve for swing priority and the variable swing priority valve. As the swing joystick is moved farther from the NEUTRAL position, the pilot oil pressure increases. This gradual increase in pilot oil pressure causes a gradual change to swing priority. Thus, swing priority is controlled by the position of the swing joystick and swing priority automatically activates when the joystick reaches a certain position. When swing priority is activated, the output flow from the drive pump supplies hydraulic oil to the swing hydraulic circuit. Since swing priority increases the swing acceleration, swing priority is useful for loading operations. Swing priority is also useful for leveling operations and trenching operations when higher swing force is required.


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Illustration 124 Stick I control valve (swing priority OFF) (15) Parallel feeder passage (20) Variable swing priority valve (22) Passage (24) Pilot line (swing pilot pressure) (27) Pressure reducing valve for swing priority (38) Pilot line (pilot system pressure)

(39) Pin hole (40) Spool (41) Spring (42) Passage (stick I) (43) Spool (44) Drain line (45) Check valve

(46) Orifice (47) Line (48) Passage (50) Spring (51) Passage (56) Drain Line


g00848162

Illustration 125 SWING RIGHT operation (swing priority OFF) (4) Swing motor (13) Parallel feeder passage (15) Parallel feeder passage (18) Swing control valve (19) Stick I control valve (20) Variable swing priority valve (21) Passage

(22) Passage (23) Pilot control valve (swing and stick) (24) Pilot line (26) Pilot line (27) Pressure reducing valve for swing priority (28) Drive pump

(29) Idler pump (30) Pilot pump (38) Pilot line (41) Spring (47) Line (48) Passage (50) Spring

129 Hydraulic System Systems Operation Section When the swing joystick is in the NEUTRAL position, no pilot oil pressure acts on spool (40) of pressure reducing valve for swing priority (27). Full pilot oil pressure flows through pilot line (38), the pressure reducing valve for swing priority (27), line (47) and passage (22) to variable swing priority valve (20). Spool (43) in the variable swing priority valve is shifted upward against the force of spring (41). The oil delivery from drive pump (28) in parallel feeder passage (13) flows through parallel feeder passage (15) and variable swing priority valve (20). The oil delivery enters stick I control valve (19). When the swing joystick is moved slightly from the NEUTRAL position in order to perform a SWING RIGHT operation, reduced pilot oil pressure from pilot control valve (23) flows through pilot line (26). The pilot oil then divides into two flow paths. Part of the pilot oil flows through passage (21) to swing control valve (18). The spool in the swing control valve shifts a slight amount that corresponds to the amount of movement of the swing joystick. The remainder of the pilot oil flows through pilot line (24) and passage (48). The pilot oil pressure acts on the shoulder of spool (40) in the pressure reducing valve for swing priority (27). Spool (40) shifts against the force of spring (50). Since the reduced pilot oil pressure in passage (22) is still higher than the force of spring (41), spool (43) in variable swing priority valve (20) remains shifted upward. The oil delivery from drive pump (28) to stick I control valve (19) is not restricted. Swing priority is not activated.


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Illustration 126 Stick I control valve (swing priority ON) (15) Parallel feeder passage (20) Variable swing priority valve (22) Passage (24) Pilot line (swing pilot pressure) (27) Pressure reducing valve for swing priority (38) Pilot line (pilot system pressure) (39) Pin hole (40) Spool (41) Spring

(42) Passage (stick I) (43) Spool (44) Drain line (45) Check valve (46) Orifice (47) Line (48) Passage (50) Spring (51) Passage (56) Drain line


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Illustration 127 SWING RIGHT operation (swing priority ON) (4) Swing motor (13) Parallel feeder passage (15) Parallel feeder passage (18) Swing control valve (19) Stick I control valve (20) Variable swing priority valve (21) Passage (22) Passage

(23) Pilot control valve (swing and stick) (24) Pilot line (26) Pilot line (27) Pressure reducing valve for swing priority (28) Drive pump (29) Idler pump (30) Pilot pump

As the swing joystick is moved to the FULL STROKE position during a SWING RIGHT operation, the pilot oil pressure in passage (21) increases. The spool in swing control valve (18) shifts fully upward. The pilot oil pressure in pilot line (24) and passage (48) also increases. Spool (40) in the pressure reducing valve for swing priority (27) shifts fully against the force of spring (50).

(38) Pilot line (41) Spring (45) Check valve (46) Orifice (47) Line (48) Passage (50) Spring

Passage (51) restricts the pilot oil flow from pilot line (38) through the pressure reducing valve for swing priority (27). The pilot oil pressure in line (47) and passage (22) also decreases. Spool (43) in variable swing priority valve (20) is pushed downward by the force of spring (41).

132 Hydraulic System Systems Operation Section The oil delivery from drive pump (28) in parallel feeder passage (15) is restricted by orifice (46) in check valve (45). A portion of the oil delivery from the drive pump flows into passage (42). Swing priority is now activated. Most of the oil delivery from the drive pump is dedicated to the swing system and flows through the swing control valve to the swing motor. As a result, swing priority and higher swing force can be achieved with the swing joystick. A portion of the pilot oil at passage (51) flows through passage (39) to spool (40). Pilot oil pressure that flows from passage (22) into variable swing priority valve (20) corresponds to the position of the swing joystick. i01638171

Swing Motor SMCS Code: 5058-ZW


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Illustration 128 Swing motor (1) (2) (3) (4) (5) (6) (7) (8) (9)

Relief valve Relief valve Motor head Port (pilot system oil) Separator plate Friction plate Plate Body Drive shaft

(10) Check valve (11) Makeup port (12) Drain port (13) Passage (supply oil or return oil) (14) Check valve (15) Passage (supply oil or return oil) (16) Port (supply oil or return oil) (17) Port (supply oil or return oil) (18) Passage (supply oil or return oil)

The swing motor may be divided into the following three groups :

(19) Valve plate (20) Passage (supply oil or return oil) (21) Brake spring (22) Brake piston (23) Piston (24) Cylinder barrel (25) Retainer plate (26) Shoe

• The relief valves and the makeup valves consists of the following components : relief valve (1), relief valve (2), check valve (10), and check valve (14).

• The rotary group consists of the following components : cylinder barrel (24), pistons (23), shoes (26), retainer plate (25), and drive shaft (9).

• The parking brake consists of the following components : brake spring (21), brake piston (22), separator plate (5), and friction plate (6).

Supply oil from the drive pump is delivered to port (16) or port (17). During a SWING RIGHT operation, the oil delivery enters motor head (3) at port (17) and flows through passage (18). The oil then flows through passage (13) in valve plate (19) and passes through passage (20) in cylinder barrel (24). This oil pressurizes piston (23) in motor head (3).

134 Hydraulic System Systems Operation Section The case drain oil from the swing motors returns through drain port (12) of motor head (3) to the hydraulic tank. Reference: For more information concerning the swing parking brake, refer to Systems Operation, “Pilot Valve (Swing Parking Brake)”. Reference: For more information concerning the swing relief valves , refer to Systems Operation, “Relief Valve (Swing)”. i01637490

Pilot Valve (Swing Parking Brake) SMCS Code: 5059; 5483

Illustration 129

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Motor passages (A) Bottom center position (B) Inlet side (high pressure) (C) Top center position (D) Outlet side (low pressure) (13) Passage (valve plate) (15) Return passage (16) Port (17) Port (18) Supply passage (20) Passage (cylinder barrel) (27) Passage (valve plate) (28) Direction of motor rotation (counterclockwise rotation)

Shoe (26) is pressed against the upper surface of plate (7) by the force of piston (23). The shoe and the piston slide along the slope of plate (7) in a counterclockwise direction. This sliding force causes cylinder barrel (24) to rotate in a counterclockwise direction (28). As each piston reaches the bottom center position (A), oil flows through passage (27) in valve plate (19). This oil then flows through passage (15) of motor head (3) to the hydraulic tank. As cylinder barrel (27) continues to rotate counterclockwise, the piston and the shoe continue to move up the inclined surface of plate (28). Since cylinder barrel (24) is splined to drive shaft (9), the drive shaft rotates in the same direction as the cylinder barrel. For a SWING LEFT operation, swing pump supply oil is delivered to port (16). The supply ports and the return ports are reversed. Cylinder barrel (24) turns clockwise.

Illustration 130

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(2) Swing parking brake solenoid valve

Swing parking brake solenoid valve (2) is located on the pilot oil manifold. When any one of the joysticks (swing, stick, boom and/or bucket) is moved from the NEUTRAL position, the swing parking brake solenoid valve is energized in order to release the swing parking brake. When the swing parking brake solenoid valve is energized, pilot oil flows to the swing motor in order to release the swing parking brake. Note: Operation of the travel levers/pedals will not release the swing parking brake.


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Illustration 131 Swing parking brake (disengaged position) (2) Swing parking brake solenoid valve (3) Spool (4) Spring (5) Passage (6) Passage (7) Port (pilot system oil)

(8) Pilot oil manifold (9) Spool chamber (10) Line (11) Body (swing motor) (12) Friction plate (13) Separator plate

The swing parking brake is located between motor head (19) of swing motor and body (11). The swing parking brake consists of the following components : brake spring (18), brake piston (17), separator plate (13), and friction plate (12). Friction plate (12) is splined to cylinder barrel (16). Separator plate (13) is splined to body (11). Separator plate (13) and friction plate (12) move in an axial direction. When the joysticks are moved from the NEUTRAL position, the implement/swing pressure switch senses the increase in pilot oil pressure at the pilot control valves. The implement/swing pressure switch changes to the ON position. The implement/swing pressure switch sends an input signal to the engine and pump controller. The engine and pump controller energizes swing parking brake solenoid valve (2).

(14) Piston chamber (15) Port (swing motor) (16) Cylinder barrel (17) Brake piston (18) Brake spring (19) Motor head

When swing parking brake solenoid valve (2) is energized, spool (3) moves in a downward direction against the force of spring (4). Pilot oil in passage (7) flows through spool chamber (6) and line (10) to port (15) of the swing motor. The pilot oil now enters piston chamber (14). The pilot pressure causes brake piston (17) to move upward against the force of brake spring (18). The force that holds separator plate (13) and friction plate (12) together is released. When the swing parking brake is released, the swing operation of the upper structure is enabled. Note: If the swing parking brake becomes inoperable due to failure of swing parking brake solenoid valve (2), the swing brake can be released by turning the temporary brake release screw in a clockwise direction until the temporary brake release screw stops.


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Illustration 132 Swing parking brake (engaged position) (2) Swing parking brake solenoid valve (3) Spool (4) Spring (5) Passage (6) Passage (7) Port (pilot system oil)

(8) Pilot oil manifold (9) Spool chamber (10) Line (11) Body (swing motor) (12) Friction plate (13) Separator plate

When the joysticks are returned to the NEUTRAL position, supply oil from the drive pump to the swing motor is stopped. The implement/swing pressure switch senses the decrease in pilot oil pressure at the pilot control valves. The implement/swing pressure switch changes to the OFF position. The engine and pump controller senses the change of signal at the implement/swing pressure switch. The engine and pump controller de-energizes swing parking brake solenoid valve (2).

(14) Piston chamber (15) Port (swing motor) (16) Cylinder barrel (17) Brake piston (18) Brake spring (19) Motor head

Spool (3) is moved upward by the force of spring (4). Spool (3) blocks pilot oil flow from port (7) to piston chamber (14). Brake spring (18) forces brake piston (17) downward. The oil in piston chamber (14) flows through port (15) and line (10) to pilot oil manifold (8). The oil then flows into spool chamber (6) and passage (9) of spool (3). The oil then flows through passage (5) to the hydraulic tank. As brake piston (17) moves downward, separator plate (13) and friction plate (12) are forced together. Since separator plates (13) are splined to body (11), the rotation of cylinder barrel (16) in the swing motor is stopped. Rotation of the upper structure is prevented. Since the engine and pump controller does not de-energize the swing parking brake solenoid valve until approximately 6.5 seconds after the swing joystick is returned to the NEUTRAL position, the rotation of the swing motors stops before the swing parking brake is engaged. If the solenoid is de-energized before the rotation of the swing motors stops, damage and wear to the swing parking brakes would result.


Relief Valve (Swing) SMCS Code: 5454

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Illustration 133 Pressure circuit for SWING RIGHT operation (partial schematic) (1) (2) (3) (4) (5) (6) (7)

Passage (supply oil) Makeup port Relief valve Passage Motor rotary group Swing motor Passage (return oil)

Illustration 134 Swing motor (2) Makeup port (3) Relief valve (6) Swing motor (8) Relief valve (10) Makeup line

(8) Relief valve (9) Passage (10) Makeup line (11) Check valve (12) Port (supply oil) (13) Port (return oil) (14) Check valve

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(15) Check valve (16) Return line (17) Swing control valve (18) Slow return check valve (19) Return line


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Illustration 135 Swing relief valve (4) Return passage (7) Passage (20) Orifice (21) Spring (22) Stem

(23) Piston chamber (24) Passage (25) Piston (26) Passage (27) Piston chamber

Relief valves (3) and (8) are located in the head of swing motor (6). These relief valves limit the pressure in the left and right swing circuits to the swing relief valve setting. This provides a cushion effect at a start or stop of the swing operation. When the swing joystick is returned to the NEUTRAL position during the swing right operation, the swing control valve shifts to the NEUTRAL position. Since the swing control valve is in the NEUTRAL position, the oil delivery through port (12) to the motor rotary group (5) is now blocked at the swing control valve. The return oil from the motor rotary group through port (13) is also blocked at the swing control valve. The mass (weight and size) of the upper structure causes the upper structure to attempt to continue to rotate after the swing joystick is returned to the NEUTRAL position. The motor rotary group is also attempting to continue to rotate. The motor rotary group attempts to draw oil through port (12) and attempts to displace the oil through port (13). The oil supply to motor rotary group (5) is insufficient. A vacuum condition occurs in passage (1). Return oil is supplied to the motor rotary group as makeup oil in order to prevent the vacuum condition. For more information concerning the makeup operation, refer to Systems Operation, “Oil Makeup (Swing System)”.

(28) Orifice (29) Passage (30) Adjustment plug

Since the flow of return oil from the motor rotary group through port (13) is blocked at the swing control valve, the pressure of the blocked oil in passage (7) increases. The increased oil pressure in passage (7) acts on swing relief valve (8). The increased pressure oil forces stem (22) of relief valve (8) to the right (open position) against the force of spring (21). When stem (22) shifts, oil flows through passage (9), check valve (11) and passage (1) to motor rotary group (5). The shock load is absorbed at the stop of a swing movement. At swing relief valve (8), the increased oil pressure in passage (7) flows through orifice (20) in stem (22) and passage (26) to piston chamber (27). The force of spring (21) is less than the relief valve pressure setting. This causes stem (22) to move to the right (open position) before the oil pressure in passage (7) reaches the relief valve pressure setting. At the same time, the pressure oil in piston chamber (27) flows through passages (24) and (29). Piston (25) moves to the left against the force of spring (21). The oil in piston chamber (23) flows through orifice (28) and into piston chamber (27). Orifice (28) restricts the oil flow into piston chamber (27).

139 Hydraulic System Systems Operation Section The swing relief valve maintains the operating pressure of the swing hydraulic circuit at a lower pressure than the swing relief valve setting until the pressure in the swing hydraulic circuit forces piston (25) to the right against adjustment plug (30). When piston (25) contacts adjustment plug (30), the pressure in piston chamber (27) increases. The oil pressure in passage (7) reaches the swing relief valve setting. The oil in passage (7) flows around stem (22) and into return passage (4). After stem (22) begins to open and before piston (25) completes the movement to the left, the pressure in the swing hydraulic circuit increases gradually. The pressure in the swing hydraulic circuit does not reach a peak pressure. This is called a two-stage relief operation. The two-stage relief operation absorbs the shock load at the stop of a swing operation. After the start of a swing right operation, the oil delivery from the drive pump flows through port (12) and passage (1) to motor rotary group (5). The mass (weight and size) of the upper structure causes an increase of oil pressure in passage (1). Stem (22) of swing relief valve (3) opens slightly. A portion of the high pressure oil in passage (1) flows through makeup port (2) to return line (19). This gives a smoother acceleration at the start of a swing operation.


Oil Makeup (Swing System) SMCS Code: 5080-ZW

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Illustration 136 Pressure circuit for SWING RIGHT (partial schematic) (1) (2) (3) (4) (5) (6) (7)

Passage (supply oil) Makeup port Relief valve Passage Motor rotary group Swing motor Passage (return oil)

(8) Relief valve (9) Passage (10) Makeup line (11) Check valve (12) Port (supply oil) (13) Port (return oil) (14) Check valve

When the swing joystick is moved to the NEUTRAL position during the swing right operation, the swing control valve shifts to the NEUTRAL position. Since the swing control valve is in the NEUTRAL position, the oil delivery through port (12) to motor rotary group (5) is blocked at the swing control valve. The return oil from the motor rotary group through port (13) is also blocked at the swing control valve. The upper structure will attempt to continue to rotate after the swing joystick is returned to the NEUTRAL position. This causes an internal leak of oil in the swing motor. As a result, a vacuum condition occurs at passage (1). In order to prevent this vacuum condition, makeup oil is delivered from the return hydraulic system to the swing motor.

(15) Check valve (16) Return line (17) Swing control valve (18) Slow return check valve (19) Return line

Illustration 137 (10) Makeup line (18) Slow return check valve (19) Return line

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141 Hydraulic System Systems Operation Section Makeup oil is supplied to motor rotary group (5) from return line (16). Return oil flows from return line (16) through makeup line (10), port (2), passage (9), check valve (11) and passage (1) to motor rotary group (5). The vacuum condition in passage (1) is eliminated by the makeup oil from the return hydraulic system. During a left swing operation, the return ports and the supply ports of the swing motor are reversed. Makeup oil flows through check valve (14) if a vacuum condition occurs in passage (7) during a swing left operation. Illustration 138

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Slow return check valve (10) Makeup line (16) Return line (18) Slow return check valve (19) Return line

When all of the control valves for implements, swing and travel are in the NEUTRAL position, the oil delivery from the idler pump and the drive pump flows through return line (16) to the hydraulic tank. Slow return check valve (18) is located between return line (16) and the hydraulic tank. Slow return check valve (18) maintains the return oil pressure at 290 kPa (42 psi) in return line (16). If a vacuum condition occurs at the swing motor during the stop of a swing operation, the slow return check valve causes return oil from return line (16) to flow to motor rotary group (5) as makeup oil. The slow return check valve eliminates the vacuum condition in the swing motor due to internal leakage. If the swing joystick is moved suddenly toward the NEUTRAL position from the FULL STROKE position, the swing control valve partially closes. Until the swing control valve reaches the NEUTRAL position, the return oil from the swing motor continues to flow through passage (7) and port (13) to return line (16). The return oil pressure in passage (7) increases but the return oil pressure in passage (7) remains lower than the pressure setting of swing relief valve (8). Swing relief valve (8) remains in the CLOSED position. A vacuum condition occurs at port (12) and passage (1) due to the insufficient oil delivery from the drive pump and due to the tendency of the motor rotary group to continue to rotate. Since relief valve (8) remains in the CLOSED position, makeup oil does not flow through relief valve (8), passage (9) and check valve (11) to passage (1) to motor rotary group (5).

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Relief Valve (Cushion Crossover) (Anti-Reaction Valves) SMCS Code: 5111; 5454

Illustration 139

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Swing motor (1) (2) (3) (4)

Block Swing motor Anti-reaction valve (left swing) Anti-reaction valve (right swing)

At the stop of a swing operation, it is difficult to smoothly stop the upper structure and implements at the desired position. This is due to the mass (weight and size) of the upper structure. The outlet port of the swing motor is blocked. This causes an oscillation or a rocking motion in the swing motor. Anti-reaction valves (3) and (4) provide a more exact swing movement. The anti-reaction valves also prevent shock load at the stop of a swing operation. Anti-reaction valves (3) and (4) are located in block (1). Block (1) is mounted on swing motor (2).


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Illustration 140 Anti-reaction valve (neutral position) (1) Block (3) Anti-reaction valve (4) Anti-reaction valve (5) Motor rotary group (6) Passage (7) Port (8) Passage (9) Passage (10) Passage

(11) Port (12) Passage (13) Spring (14) Valve seat (15) Passage (16) Plunger (17) Passage (18) Spring (19) Piston chamber

(20) Passage (21) Spring chamber (22) Spring (23) Valve seat (24) Plunger (25) Spring (26) Piston (31) Passage

143 Hydraulic System Systems Operation Section During a swing operation of the upper structure, the oil delivery from the drive pump flows through passage (8) or passage (10) in block (1) to motor rotary group (5). When the swing joystick is in the NEUTRAL position, the swing control valve is in the NEUTRAL position. The oil delivery from the drive pump is blocked at the swing control valve. No oil delivery flows to the motor rotary group. The return oil from the swing motor is also blocked at the swing control valve. Plunger (24) in anti-reaction valve (3) shifts downward by the force of spring (25) until the plunger is stopped by piston (26). Valve seat (23) shifts downward by the force of spring (22) until the valve seat comes in contact with plunger (24). Plunger (16) and valve seat (14) in anti-reaction valve (4) are shifted downward in the same manner as anti-reaction valve (3).

Illustration 141 Anti-reaction valve (swing operation)

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144 Hydraulic System Systems Operation Section (1) Block (3) Anti-reaction valve (4) Anti-reaction valve (5) Motor rotary group (6) Passage (7) Port (8) Passage (9) Passage (10) Passage

(11) Port (12) Passage (13) Spring (14) Valve seat (15) Passage (16) Plunger (17) Passage (18) Spring (19) Piston chamber

When the swing joystick is moved from the NEUTRAL position in order to perform a swing operation, the swing control valve shifts. The oil delivery from the drive pump flows through the swing control valve and port (11) in block (1). The oil delivery then flows through passage (10), passage (12) and motor rotary group (5). Return oil from the motor rotary group flows through passage (6), passage (8), port (7) and the swing control valve to the hydraulic tank. The motor rotary group rotates. A portion of the pressure oil from the drive pump at port (11) also flows to anti-reaction valves (3) and (4). At anti-reaction valve (3), pressure oil from the drive pump and the force of spring (22) shifts valve seat (23) downward against plunger (24). Plunger (24) shifts downward against piston (26). Pressure oil from the drive pump also flows through passage (9). The pressure oil enters spring chamber (34) of anti-reaction valve (4). Plunger (16) shifts upward against the force of spring (18). Valve seat (14) is moved upward against the force of spring (13) by plunger (16).

(20) Passage (21) Spring chamber (22) Spring (23) Valve seat (24) Plunger (25) Spring (26) Piston (31) Passage (34) Spring chamber


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Illustration 142 Anti-reaction valve (swing stop) (3) Anti-reaction valve (4) Anti-reaction valve (5) Motor rotary group (7) Port (8) Passage (9) Passage (10) Passage (11) Port (13) Spring (14) Valve seat

(15) Passage (16) Plunger (17) Passage (18) Spring (19) Piston chamber (20) Passage (21) Spring chamber (22) Spring (23) Valve seat (24) Plunger

(25) Spring (27) Orifice (26) Piston (28) Valve chamber (29) Passage (30) Ball (31) Passage (32) Orifice (33) Ball (35) Valve chamber

146 Hydraulic System Systems Operation Section When the swing joystick is returned to the NEUTRAL position, the oil delivery from the drive pump to motor rotary group (5) is blocked at the swing control valve. The motor rotary group continues to rotate due to the mass (weight and size) of the upper structure. Since the return oil flow from the motor rotary group is also blocked at the swing control valve, the oil pressure in passage (8) increases. The oil pressure in passage (10) decreases. The increased oil pressure in passage (8) then enters anti-reaction valve (4). The oil flows through passage (15) and passage (17). The oil then enters piston chamber (19). The oil pressure in piston chamber (19) forces plunger (16) upward against the force of spring (18). Valve seat (14) shifts upward against the force of spring (13). A portion of the increased oil pressure in passage (8) flows through passage (31) and passage (20). The oil then enters spring chamber (21) in anti-reaction valve (3). The oil pressure in spring chamber (21) forces plunger (24) and valve seat (23) upward against the force of springs (22) and (25). As the motor rotary group of the swing motor continues to attempt to stop, the oil pressure in passage (8) gradually decreases. The oil pressure in piston chamber (19) decreases . The force of spring (18) causes plunger (16) to shift downward at a rapid rate. Valve seat (14) shifts downward by the force of spring (13). Since orifice (27) restricts the flow of oil from valve chamber (28), valve seat (14) moves in a downward direction more slowly than plunger (16). The contact between plunger (16) and valve seat (14) is no longer maintained. The oil pressure in passage (15) forces ball (30) against the top end of plunger (16). The oil in passage (8) now flows through passages (29) and (9) to passage (10). During the separation of plunger (16) and valve seat (14) in anti-reaction valve (4), anti-reaction valve (3) activates also. In anti-reaction valve (3), The pressure of the oil that flows from spring chamber (21) to passage (8) decreases. The force of spring (25) causes plunger (24) to shift downward. The force of spring (22) causes valve seat (23) to shift downward. Since orifice (32) restricts the flow of oil from valve chamber (35), valve seat (23) shifts more slowly than plunger (24). The contact between plunger (24) and valve seat (23) is no longer maintained. The oil pressure in passage (20) forces ball (33) against the valve seat (23). Now, the oil flow from passage (8) through passage (31) to passage (10) is blocked by ball (33).

Since passages (8) and (10) are connected by activation of anti-reaction valve (4), the swing movement of the upper structure stops with a minimal shock load at a desired position. A more exact swing movement is possible. A slight shock load may occur due to the gear backlash of the swing drive.


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Illustration 143 Anti-reaction valve (reverse rotation) (3) Anti-reaction valve (4) Anti-reaction valve (5) Motor rotary group (7) Port (8) Passage (9) Passage (10) Passage (11) Port (13) Spring (14) Valve seat

(15) Passage (16) Plunger (17) Passage (18) Spring (19) Piston chamber (20) Passage (21) Spring chamber (22) Spring (23) Valve seat (24) Plunger

When motor rotary group (5) is slightly rotated in the reverse direction due to the gear backlash, oil pressure in passage (10) increases and oil pressure in passage (8) decreases. Anti-reaction valves (3) and (4) function in order to stop the swing movement of the upper structure with a slight reversed motion. The increased oil pressure in passage (10) causes a shock load. The absorption of the shock load is described in the following manner.

(25) Spring (27) Orifice (26) Piston (28) Valve chamber (29) Passage (30) Ball (31) Passage (32) Orifice (33) Ball (35) Valve chamber

In anti-reaction valve (3), plunger (24) and valve seat (23) separate from each other. Ball (33) is forced against plunger (24) by the pressure oil in passage (10). Oil can now flow from passage (10) through passages (20) and (31) to passage (8).

148 Hydraulic System Systems Operation Section In anti-reaction valve (4), plunger (16) and valve seat (14) separate from each other. Ball (30) is forced against valve seat (14) by the pressure oil in passage (29). The flow of oil from passage (10) through passage (9) to passage (8) is blocked. The oil pressure in passage (10) decreases and the rotation of motor rotary group (5) is prevented. The swing movement is gradually stopped. i01638903

Swing Drive SMCS Code: 5459

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Illustration 144 Swing drive (1) First stage planetary carrier (2) First stage planetary gear (3) Second stage planetary carrier (4) Ring gear (5) Second stage planetary gear

(6) Roller bearing (7) Roller bearing (8) Pinion shaft (10) Shaft (swing motor) (11) First stage sun gear

The swing drive consists of a series of planetary gears. The planetary gears reduce the rotational speed of the swing motor. The swing motor is bolted to the top of the swing drive. The swing drive is bolted to the upper structure. The teeth of the swing drive output pinion shaft (8) engage with bearing gear (15) of the swing bearing. The pinion shaft (8) rotates around bearing gear (15). This causes the machine to swing. Bearing gear (15) is attached to the lower structure.

(12) Second stage sun gear (14) Housing (15) Bearing gear (swing gear)

The swing drive is divided into the following two groups :


• The first group is a double reducer of motor

speed. The components of the first stage reduction are first stage sun gear (11), first stage planetary gears (2), ring gear (4) and first stage planetary carrier (1). The components of the second stage reduction are second stage sun gear (12), second stage planetary gear (5), ring gear (4) and second stage planetary carrier (3).

• The second group is the group for reduced

output speed of the motor. The components of the second group are roller bearing (6), roller bearing (7) and pinion shaft (8). The roller bearings are installed in housing (14) and the roller bearings support pinion shaft (8).

The swing speed is reduced by a ratio of teeth on the sun gear to ring gear teeth by planetary reduction. Since the sun gear is inside of the ring gear, the swing drive is more compact than reduction units with external teeth.

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Illustration 145 Operation of the first stage planetary assembly (1) First stage planetary carrier (2) First stage planetary gear

(4) Ring gear (11) First stage sun gear

Swing motor output shaft (10) is splined to first stage sun gear (11). First stage planetary gears (2) of first stage planetary carrier (1) mesh with first stage sun gear (11). When first stage sun gear (11) rotates counterclockwise, first stage planetary gears (2) rotate in a clockwise direction on shafts (16). First stage planetary gears (2) move counterclockwise around ring gear (4). Ring gear (4) is bolted to housing (14). First stage planetary carrier (1) rotates counterclockwise.

(16) Shaft (first stage planetary gear)


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Illustration 146 Swing drive (1) First stage planetary carrier (2) First stage planetary gear (3) Second stage planetary carrier (4) Ring gear

(5) Second stage planetary gear (6) Roller bearing (7) Roller bearing (8) Pinion shaft

(11) First stage sun gear (12) Second stage sun gear (17) Inner circumference of carrier

Splines on inner circumference (17) of first stage planetary carrier (1) engage with the splines on second stage sun gear (12). This causes second stage sun gear (12) to rotate counterclockwise when the first stage planetary carrier rotates. Second stage planetary gears (5) turn clockwise on the shafts and second stage planetary gears (5) move in a counterclockwise direction around ring gear (4). Second stage planetary carrier (3) turns counterclockwise around ring gear (4). The splines on the inner circumference of second stage planetary carrier (3) engage with the splines of pinion shaft (8). When the second stage planetary carrier turns clockwise, pinion shaft (8) rotates counterclockwise.

Illustration 147 Rotation of pinion shaft (8) Pinion shaft (15) Bearing gear (swing bearing) (18) Position of moving pinion shaft

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151 Hydraulic System Systems Operation Section Pinion shaft (8) engages with bearing gear (15) on the inner circumference of the swing bearing. Bearing gear (15) is bolted to the lower structure. As pinion shaft (8) rotates counterclockwise, pinion shaft (8) moves in a clockwise direction around bearing gear (15). The upper structure also rotates in a clockwise direction around bearing gear (15). This causes the upper structure to swing to the right (clockwise rotation).

Return System i01631239

Return Hydraulic System SMCS Code: 5050-RJ

Illustration 148

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152 Hydraulic System Systems Operation Section (1) Swing motor (2) Travel motors (3) Case drain line (4) Case drain line (5) Makeup line (makeup oil to swing motor) (6) Return line (7) Return passage (8) Return line (9) Return passage (10) Main control valve

(11) Center bypass passage (12) Negative flow control orifice (13) Negative flow control orifice (14) Case drain line (15) Center bypass passage (16) Return line (17) Slow return check valve (18) Hydraulic oil cooler (19) Return filter (20) Drive pump

The oil delivery from idler pump (21) and drive pump (20) enters main control valve (10). The oil then flows to return passage (7) and return line (6) in one of the following manners. When all joysticks and/or travel levers/pedals are in the NEUTRAL position, pump low pressure standby oil from idler pump (21) flows through center bypass passage (11) and negative flow control orifice (12) to return line (6). Pump low pressure standby oil from drive pump (20) flows through center bypass passage (15) and negative flow control orifice (13) to return line (8).

(21) Idler pump (22) Pilot pump (23) Case drain filter (24) Bypass check valve (25) Hydraulic tank (26) Case drain line (27) Suction line (28) Fan pump

Makeup line (5) will route return oil to the inlet port of the swing motor if a vacuum condition occurs at the swing motor during swing stop. For more information concerning the makeup operation of the return hydraulic system at the swing motor, refer to the following sections in this manual.

• Systems Operation, “Check Valve (Return Makeup)”

• Systems Operation, “Oil Makeup (Swing System)” • Systems Operation, “Relief Valve (Swing)”

When any one of the joysticks and/or travel levers/pedals is shifted from the NEUTRAL position, center bypass passages (11) and (15) are blocked. The return oil from the cylinders and/or motors now flows through return passage (9) to return line (8). The return oil from return line (6) and return line (8) flows through return line (16) and slow return check valve (17).

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Check Valve (Return Makeup) (Slow Return Check Valve) SMCS Code: 5067; 5080

When the oil temperature is very low , most of the oil is returned through bypass check valve (24) to hydraulic tank (25). The remainder of the oil flows into oil cooler (18) and return filter (19) to hydraulic tank (25). When the oil temperature increases, the rate of oil flow through bypass check valve (24) decreases. This causes the rate of oil flow through oil cooler (18) to increase. Reference: For more information concerning the bypass check valve, refer to Systems Operation, “Bypass Valve (Return)”.

Illustration 149 Main control valve compartment (return circuit)

Case drain oil from idler pump (21), drive pump (20), pilot pump (22), and fan pump (28) flows into case drain line (26). Case drain oil from swing motor (1) and travel motors (2) flows into respective case drain lines (3) and (4). The case drain oil from the motors flows through case drain line (14) and combines with the case drain oil from the pumps at case drain line (26). All of the case drain oil from the pumps and the motors now flows through case drain filter (23) to hydraulic tank (25).

(5) Makeup line (makeup oil to swing motor) (10) Main control valve (17) Slow return check valve (29) Inlet line to oil cooler (18)

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Illustration 150 Slow return check valve and bypass check valve (5) Makeup line (makeup oil to swing motor) (16) Return line (17) Slow return check valve (24) Bypass check valve

(28) Check valve (29) Inlet line to oil cooler (18) (30) Return line to bypass check valve (33) Return line (return flow to return filter)

Slow return check valve (17) is contained in check valve (28). Slow return check valve (17) is located between the main control valves and the hydraulic tank in the return circuit. The slow return check valve restricts the return oil flow. This restriction causes a pressure increase in return line (16) and makeup line (5).

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Bypass Valve (Return) (Bypass Check Valve) SMCS Code: 5071

If cavitation occurs in the swing motor, oil from return line (16) flows into makeup line (5). This makeup oil is supplied to the inlet port of the swing motor in order to prevent cavitation in the swing motor. Note: For more information on the makeup operation, refer to System Operation, “Oil Makeup (Swing System)”. The return oil flow through slow return check valve (17) is divided into two flow paths. A portion of the oil flows through inlet line (29) to the hydraulic oil cooler. The cooled oil from the hydraulic oil cooler flows through return line (30) and the return filter to the hydraulic tank. The remainder of the oil flow from slow return check valve (17 ) flows through bypass check valve (24) and the return filter to the hydraulic tank. Bypass check valve (24) is contained in check valve (28).

Illustration 151 (19) Return filter (25) Hydraulic tank (33) Return line

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Illustration 152 Slow return check valve and bypass check valve (5) Makeup line (makeup oil to swing motor) (16) Return line (17) Slow return check valve (24) Bypass check valve

(28) Check valve (29) Inlet line to hydraulic oil cooler (18) (30) Return line to bypass check valve (33) Return line (return flow to return filter)

The return oil flow through slow return check valve (17) is divided into two flow paths. A portion of the oil flows through inlet line (29) to the hydraulic oil cooler and the remainder of the return oil flows through bypass check valve (24). When the temperature of the return oil in inlet line (29) is very low, the viscosity of the oil is high. The flow resistance of the return oil in inlet line (29) is high. Thus, the pressure of the return oil is high. As a result of the high pressure of the return oil, bypass check valve (24) opens. Most of the return oil flows through bypass check valve (24), return line (33) and return filter (19) to hydraulic tank (25). The remainder of the oil flows through inlet line (29) to the hydraulic oil cooler. Since a small amount of the return oil flows to the oil cooler, the temperature of the oil increases. As the oil temperature increases, the return oil pressure decreases. Bypass check valve (24) begins to close. A greater portion of the return oil flows to the hydraulic oil cooler. Bypass check valve (24) maintains the hydraulic oil at the optimum operating temperature.


Hydraulic Tank and Filter SMCS Code: 5056; 5068

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Illustration 153 (19) Return filter (25) Hydraulic tank (34) Element (35) Return chamber

(36) Tank chamber (37) Suction filter (38) Line (39) Suction line

(40) Port (41) Relief valve (42) Passage

The return oil from the hydraulic oil cooler flows through port (40) and passage (42) to return chamber (35). Return filter (19) consists of element (30) and relief valve (41). The return filter is mounted on the rear surface of the hydraulic tank. The return oil passes through element (34) of return filter (19). The return oil then flows through line (38) to hydraulic tank (25). Thereafter, the oil passes through suction filter (37) and the oil is delivered to the pumps through suction line (39). Illustration 154

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(43) Air breather

Air breather (43) is located on the upper surface of the hydraulic tank. The air breather prevents an increase or a decrease of air pressure in the hydraulic tank regardless of the following circumstances :


• Change of air pressure in the hydraulic tank due to cylinder movement.

i01644309

Hydraulic Oil Cooler

• Change of air pressure in the hydraulic tank capacity due to a temperature change.

SMCS Code: 1374

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Oil Filter (Return) (Case Drain Filter) SMCS Code: 5068-RJ

Illustration 156

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(18) Hydraulic oil cooler

Illustration 155

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Case drain filter

The hydraulic oil cooler is mounted in the compartment behind the cab. A portion of the return oil from the main control valves flows through the bypass check valve and flows through the inlet line to hydraulic oil cooler (18). The hydraulic oil that is cooled by the hydraulic oil cooler flows through the outlet line, the return line and the return filter to the hydraulic tank.

The case drain filter receives case drain oil from the following components.

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• Right travel motor

Gear Pump (Fan Motor)

• Left travel motor

SMCS Code: 506G

• Swing motor • Main hydraulic pump (idler pump and drive pump)

• Fan motor Case drain oil flow from the right travel motor, the left travel motor and the swing motor are combined at the swivel. The case drain oil flow from these components then flows to the case drain filter. The case drain oil from the main hydraulic pump and the fan motor also flows to the case drain filter. Return oil then flows from the case drain filter to the hydraulic tank.

Illustration 157 Engine compartment (rear) (34) Fan pump

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Illustration 158

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Hydraulic oil cooler compartment (28) (29) (30) (31)

Line (case drain) Line (inlet) Line (outlet) Fan motor

Illustration 159

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Pump compartment (25) Relief valve (fan pump)

The fan pump is a gear type pump that supplies oil flow to the hydraulic oil cooling system. The fan pump is mechanically connected to the engine. The pump delivery rate with load is approximately 26 L/min (6.9 US gpm). This machine uses a separate cooling pump and a separate fan motor for the hydraulic oil cooling system. The cooling system cools the hydraulic oil. Hydraulic oil is supplied by fan pump (34) to fan motor (31) through line (29). Delivery pressure from fan pump (34) is limited by relief valve (35).

Reference i01489530

Graphic Color Codes SMCS Code: 5050



Illustration 160

g00774089

160 Hydraulic System Index Section

Index A

H

Accumulator (Pilot) ................................................ 19

Hydraulic Filter (Pilot) ............................................ 17 Hydraulic Oil Cooler............................................. 156 Hydraulic Tank and Filter ..................................... 155

B Boom Drift Reduction Valve................................... 73 Boom Lower....................................................... 75 Boom Raise ....................................................... 74 Boom Hydraulic System ........................................ 63 Boom Lower....................................................... 69 Boom Priority ..................................................... 67 Boom Raise (High Speed) ................................. 63 Boom Raise (Low Speed) .................................. 66 Boom Regeneration Valve ................................. 72 Boom System ........................................................ 63 Bucket Hydraulic System....................................... 86 Bucket System....................................................... 86 Bypass Valve (Return) (Bypass Check Valve)..... 153 C Check Valve (Load) ............................................... 53 Check Valve (Return Makeup) (Slow Return Check Valve)................................................................. 152 Cylinders................................................................ 90 Cylinders (Boom, Stick and Bucket) ...................... 90 D Displacement Change Valve ............................... 106 Large Displacement Change Operation........... 108 Small Displacement Change Operation........... 106

I Important Safety Information ................................... 2 M Main Control Valve ................................................ 38 Individual Valve Operation ................................. 46 Introduction ........................................................ 43 Main Control Valve Operation in NEUTRAL Position ............................................................ 45 Main Hydraulic Pump ............................................ 28 Construction....................................................... 28 Main Pump Operation ........................................ 29 Main Hydraulic System............................................ 4 Hydraulic Pump Flow and Pressure Control System ............................................................... 7 Main Hydraulic Schematic ................................... 4 N Negative Flow Control System .............................. Fine Control Operation....................................... Introduction ........................................................ Relief Valve (Negative Flow Control) .................

55 61 55 63

O E Electronic Control System ....................................... 9

Oil Filter (Return) (Case Drain Filter) .................. 156 Oil Makeup (Swing System) ................................ 140 Oil Makeup (Travel System)................................. 116

F

P

Final Drive ........................................................... 117 Operation ......................................................... 119

Pilot Hydraulic System........................................... 10 Automatic Travel Speed Change Valve .............. 17 Boom Priority ..................................................... 17 Pilot Control Valve Circuits................................. 16 Pilot Oil Circuit ................................................... 14 Power Shift Pressure System ............................ 15 Pressure Switch Circuits .................................... 16 Straight Travel Valve Circuit ............................... 16 Swing Parking Brake.......................................... 16 Swing Priority..................................................... 17 Pilot System........................................................... 10 Pilot Valve (Joystick).............................................. 23 Pilot Valve (Swing Parking Brake) ....................... 134

G Gear Pump (Fan Motor) ...................................... 156 Gear Pump (Pilot).................................................. 17 General Information................................................. 4 Graphic Color Codes ........................................... 157

161 Hydraulic System Index Section Pilot Valve (Travel and Steering)............................ Pump Control (Main Hydraulic) ............................. Main Pump Regulator ........................................ Pressure/Flow Characteristic Curves................. Regulator Operation........................................... Pump System ........................................................

98 31 31 38 33 28

R Reference ............................................................ 157 Relief Valve (Cushion Crossover) (Anti-Reaction Valves) ............................................................... 141 Relief Valve (Line) ................................................. 50 Relief Valve (Main) ................................................ 48 Closed Position .................................................. 49 Open Position .................................................... 50 Relief Valve (Pilot) ................................................. 18 Relief Valve (Swing) ............................................ 137 Return Hydraulic System..................................... 151 Return System..................................................... 151 S Solenoid Valve (Hydraulic Activation) .................... 21 Solenoid Valve (Proportional Reducing) (Power Shift System)................................................................ 26 Stick Drift Reduction Valve .................................... 84 Stick In ............................................................... 86 Stick Out ............................................................ 85 Stick Hydraulic System.......................................... 75 Stick In ............................................................... 77 Stick Out ............................................................ 75 Stick Regeneration Valve ................................... 82 Stick Unloading Valve ........................................ 83 Stick System.......................................................... 75 Swing Drive ......................................................... 148 Swing Hydraulic System...................................... 122 Swing Priority................................................... 126 Swing Motor......................................................... 132 Swing System...................................................... 122 Swivel .................................................................. 120 Systems Operation Section ..................................... 4 T Table of Contents..................................................... 3 Travel Counterbalance Valve ............................... 109 Counterbalance Valve Operation During Level Travel.............................................................. 110 Counterbalance Valve Operation During Slope Travel.............................................................. 112 Operation Of Travel Crossover Relief Valves During Machine Stop ................................................. 114 Travel Parking Brake Operation ....................... 116 Travel Hydraulic System ........................................ 91 Automatic Travel Speed Change........................ 98 Forward Travel.................................................... 93 HIGH SPEED..................................................... 97 LOW SPEED...................................................... 96 Travel Control ..................................................... 91

Travel Motor ......................................................... 100 Travel Parking Brake............................................ 103 Travel System ........................................................ 91



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330C_Hyd_Sys-Op

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