t02_1 hitachi

SECTION 2

SYSTEM —CONTENTS— Group 1 Control System Outline ................................................... .....................................................T2-1-1 ..T2-1-1 Engine Control .........................................T2-1-2 .........................................T2-1-2 Pump Control .........................................T2-1-23 .........................................T2-1-23 Valve Control................................... Control..........................................T2-1-32 .......T2-1-32 Other Controls........................................T2-1-46

Group 2 Hydraulic System Outline ................................................... .....................................................T2-2-1 ..T2-2-1 Pilot Circuit.......................... Circuit...............................................T2-2-2 .....................T2-2-2 Main Circuit ............................................T2-2-12 ............................................T2-2-12

Group 3 Electrical System Outline ................................................... .....................................................T2-3-1 ..T2-3-1 Main Circuit ..............................................T2-3-2 ..............................................T2-3-2 Electric Power Power Circuit ...............................T2-3-3 ...............................T2-3-3 Indicator Light Check Circuit.....................T2-3-4 Accesso Acc esso ry Circu Ci rcuit it ..... .. ....... .... .... .... ....... ... .... .... .... .... .T 2-3- 5 Preheat Circuit .........................................T2-3-6 .........................................T2-3-6 Starting Circuit .........................................T2-3-8 .........................................T2-3-8 Charging Circuit .....................................T2-3-10 Serge Voltage Voltage Prevention Circuit ............T2-3-14 Engine Stop Circuit.................................T2-3-16 Circuit.................................T2-3-16

178T-2-1

(Blank)

178T-2-2

(Blank)

178T-2-2

SYSTEM / Control System OUTLINE The main controller (MC) is used to control machine operations. Electronic signals from the engine control dial, various sensors and switches are sent to the MC.

After processing the received signals in the logic logic circuit, the MC sends out control signals to the EC motor, solenoid valve units, torque control solenoid valve, and other control circuits to regulate the engine, pumps, motors and valves.

I np ut S ig na ls •

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EC Sensor Engine Control Dial Pump 1 Control Pressure Sensor Pump 2 Control Pressure Sensor Pump 1 Delivery Pressure Sensor Pump 2 Delivery Pressure Sensor Pump 3 Delivery Pressure Sensor (Oprtional) N sensor Pressure Switch (Travel) Pressure Switch (Front Attachment) Pressure Switch (Swing) Pressure Switch (Boom Raise) Pressure Switch (Arm Roll-In) Pressure Switch (Auxiliary) Pressure Switch (Arm Roll-Out) (Optional) Hydraulic Oil Temperature Sensor

Auto -Idle/A -Id le/Acce ccelera lera tion Selecto Sele ctor r

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Power Digging Switch Power Mode Switch (HP/E/P) Travel Mode Switch (Fast/Slow) Work Mode Switch (Digging/Attachment) Learning Switch Key Switch

O ut p ut S ig na ls Engine Control (EC Motor) Engine Control Dial HP Mode Control E mode Control Auto -Idle -Id le Contr C ontr ol Auto -Accele -Ac cele rati on Contr C ontr ol Auto -Warm -W arm ing Up Contr C ontr ol Idle Speed-Up Control Engine Speed Automatic Travel(Oniy ZAXIS270)

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 

Increase

Control

at

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Atta chm ent Oper atio n Sp eed Incr ease Control Cont rol

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Atta chm ent Oper atio n Sp eed Lim it Contr C ontr ol

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Engine Learning Control

   

MC

Pump Control (Torque Control Solenoid Valve) S p ee d S e n s in g Co nt r o l Slow Speed Torque Increase Control ∗

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Pump 1 Flow Rate Limit Control Pump 2 Flow Rate Limit Control Pump 3 Torque Decrease Control

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Valve Control (Solenoid Valve Unit) Power Digging Control Arm Flow Flo w Rate Rat e Co ntro l Arm Rege nera tive Control Cont rol Travel Motor Swash Angle Control Auto -Power -Po wer Lift Lif t Contr Co ntrol ol

 

  

∗

Boom Angle Sensor (Only ZAXIS225US) Auxiliar Aux iliar y Mode Switc h (Opti ( Optional onal )

Auxi liar y Flow Flo w Rat e Contro Co ntro l

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Other Controls Boom Electronic ZAXIS225US) Work Mode Control ∗

Travel Alarm Control

∗

NOTE: Only on the machines equipped with the corresponding optional parts.

T2-1-1

Cushion

Control

(Only

SYSTEM / Control System ENGINE CONTROL The engine control system is grouped as follows: •

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Engine Control Dial Control HP Mode Control E Mode Control Auto-Idle Control Auto-Acceleration Control Auto-Warming Up Control

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Idle Speed-Up Control Engine Speed Automatic Increase Control at Travel (Only ZAXIS270) Attachment Operation Speed Increase Control Attachment Operation Speed Limit Control Engine Learning Control ∗ ∗

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NOTE: Only on the machines corresponding optional parts.

with

the

Engine Control System Layout

Learning Switch

Pressure Sensor Travel Front Attachment Swing Boom Raise Arm Roll- In

Key Switch

Pump 2 Delivery Pressure Sensor


Auxili ary ( Opti onal ) Engine Control Dial

EC Sensor

Aut o-Id le / Acc elera tion Selector Aut o-Id le EC Motor Aut o-Ac cele rati on

Power Mode Switch HP Mode E Mode P Mode

Work Mode Switch Digging Mode

Pump 2 Control Pressure Sensor Auxil iary Mod e Hydraulic Oil Temperature Switch Sensor (Optional)

Att achm ent Mode

T2-1-2

Pump 1 Control Pressure Sensor

T178-02-01-027

SYSTEM / Control System (Blank)

T2-1-3

SYSTEM / Control System Engine Control Dial Control Function: Controls the engine speed in response to the rotation angle of the engine control dial -1 and reduces the engine speed by 100 m in to reduce fuel consumption and noise level when all control levers are in neutral.

Engine Speed

Engine speed is reduced by 100 -1 min when the control levers are in neutral.

Control Range

Operation: The MC drives the governor lever in response to the rotation angle of the engine control dial to regulate the engine speed. NOTE: Even if the control dial is rotated to the full speed position, the governor lever doesn’t come in contact with the full speed stopper. (Refer to the HP mode control.) Approx. 1 second after all control levers are in neutral (the travel and front attachment sensors are OFF), the MC drives the EC motor so that the engine speed is -1 reduced from the maximum speed by 100 min . NOTE: The engine speed is reduced from the -1 maximum speed by 100 min . Therefore, when the engine speed set by the engine control dial is already slower than the -1 maximum speed by 100 min , the engine speed remains unchanged. This engine speed reduction control is activated regardless of whether the auto-idle and/or auto-acceleration control is activated or not.

T2-1-4

Minimum Speed

Maximum Speed

Engine Control Dial Position

ANIMATION

SYSTEM / Control System

Pressure Sensor Travel Front Attachment

Engine Control Dial

EC Motor

T178-02-01-004

T2-1-5

SYSTEM / Control System HP Mode Control Function: Slightly increases digging power such as arm roll-in operation while excavating deeply.

Engine Speed 1650 min

Operation: The MC drives the EC motor to slightly increase the engine speed set by the engine control dial when all the following conditions exist with the power mode switch is in the HP position. •

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1500 min

Maximum speed increases by -1 200 min except ZAXIS230 and 270 (by 100 1 min ).

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−

-1

Engine Control Dial: Set at 1500 min or faster. Boom Raise and/or Arm Roll-In Control: In Operation Average Delivery Pressure of Pumps 1 and 2: High

NOTE: The engine governor stopper position is adjusted in the HP mode. Accordingly, the governor lever doesn’t come in contact with the stopper in the normal mode.

T2-1-6

Minimum Speed

Maximum Speed


ANIMATION


Pressure Sensor

Boom Raise



Arm Roll -In Engine Control Dial

EC Motor

Power Mode Switch HP Mode

T178-02-01-005

T2-1-7

ANIMATION

SYSTEM / Control System E Mode Control Function: Reduce the engine speed by the constant specified ratio.

Engine Speed

Engine speed is reduced at the constant specified ratio.

Operation: The MC drives the EC motor to reduce the engine speed set by the engine control dial when the power mode switch is in the E mode position. The engine speed is reduced in proportion to the rotation angle of the engine control dial. Minimum Speed

Maxim um Speed


Engine Control Dial

EC Motor

Power Mode Switch

E Mode

T178-02-01-006

T2-1-8


T2-1-9

SYSTEM / Control System Auto-Idle Control Function: Reduces the engine speed when all control levers are in neutral to reduce fuel consumption and noise level. Operation: Approx. 3.5 seconds after all control levers are return to neutral, the MC drives the EC motor so that the engine speed is reduced to the auto-idle speed. As soon as a control lever is operated (the travel and/or front attachment pressure sensor is turned ON), the MC drives the EC motor so that the engine speed is increased to the original engine speed (set by the engine control dial). Auto-Idle System Deactivation Requirements: Control Levers: Being operated (either travel or front attachment control levers with pilot sensor ON) Power Mode Switch: When the E mode is changed to P mode or the P mode is changed to the E mode. Engine Control Dial: When engine speed is changed. •

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T2-1-10

Engine Speed Engine speed is reduced to the auto-idle speed 3.5 seconds later.

Minimum Speed Aut o-Id le Speed

Maximum Speed


ANIMATION


Pressure Sensor Travel Front Attachment

Engine Control Dial Aut o-Id le/ Acc elera tion Selector Auto -Idl e EC Motor

Power Mode Switch

E Mode

T178-02-01-007

T2-1-11

SYSTEM / Control System Auto-Acceleration Control Function: Automatically regulates the engine speed to meet the machine operating conditions. When all the control levers are in neutral, the engine speed is reduced to reduce fuel consumption and noise level. Operation: When a control lever is operated with the auto-idle / acceleration selector in auto acceleration position, the MC calculates the most proper engine operating speed corresponding to the signals from pressure sensors (travel, swing, boom raise, and arm roll-in), the pump control pressure sensors, and the pump delivery pressure sensors. Then, the MC drives the EC motor so that the engine speed is set to the rotation speed calculated by the MC. When all control levers are returned to neutral, the engine speed is reduced by 400 -1 min from the maximum speed first. Then, 3.5 seconds later, the engine speed is further reduced to the auto-idle speed.

Lever Stroke VS. Engine Speed Change Engine Speed

Engine speed is automatically controlled in response to the control lever operations.

Engine speed is reduced to the auto-idle speed 3.5 seconds later. Engine speed is reduced from the maximum speed by -1 400 min .

Minimum Speed

Auto -Idl e Speed

Maximum Speed


Operating Time Progress VS. Engine Speed Change Control Lever Stroke Full Stroke

NOTE: When all control levers are returned to neutral, the engine speed is reduced by -1 400 min from the maximum speed. In case the engine speed is set by the engine control dial and is running at a speed slower than the maximum speed by 100 -1 min , the engine speed will be reduced by -1 300 min .

Neutral Position

Time

Engine Speed Max. Engine Speed (P Mode)

In response to the control lever stroke and the pump delivery pressure, the optimum engine speed is selected. Aut o Acc elera tion Control

Auto -Idle Engine Speed Time

T2-1-12

ANIMATION


Pressure Sensor Travel Swing Boom Raise Arm Roll- In



Engine Control Dial Aut o-Idl e/ Acce lerat ion Selector

Auto Acce lera tion

EC Motor



T178-02-01-008

T2-1-13

ANIMATION

SYSTEM / Control System Auto-Warming Up Control Function: Automatically warms up the hydraulic system (similar to the auto choke on automobiles). Operation: When the hydraulic oil temperature is below 0 °C (32 °F), the MC drives the EC motor in response to signals from the key switch and the hydraulic oil temperature sensor to run the engine at the auto warm up speed for 15 minutes after starting the engine.

Engine Speed

Increasing Speed

Minimum Speed

IMPORTANT: When adjusting the auto-idle speed deactivate the auto warming up control function using Dr. EX, or wait to adjust until 15 minutes after starting the engine.

Auto Warm Up Speed

Maximum Speed


Key Switch

Engine Control Dial

EC Motor

Hydraulic Oil Temperature Sensor T178-02-01-009

T2-1-14

ANIMATION

SYSTEM / Control System Idle Speed-Up Control Function: Prevents the engine from hunting when running the engine at slow speed. Operation: When the travel or front attachment function is operated while the engine is running at a speed between the minimum speed and the Idle Speed-Up Speed, the MC drives the EC motor so that the engine speed is increased to the Idle Speed-Up Speed.

Engine Speed

Increasing Speed

Maximum Speed

Minimum Speed


Idle Speed-Up Speed Pressure Sensor Travel Front Attachment

Engine Control Dial

EC Motor

T178-02-01-010

T2-1-15

ANIMATION

SYSTEM / Control System Engine Speed Automatic Increase Control at Travel (Only ZAXIS270) Function: Increases the engine speed at travel single operation to increase the travel speed. Operation: MC drives EC motor to increase the engine 1 speed by 100 min (rpm) when the power mode switch is turned to P or HP and the following conditions exist. Consequently, the pump delivery flow rate increases, so that the travel speed increases. −

Condition: Engine Control Dial: The speed is set to maximum. Travel Operation: Operated Front Attachment Operation: Not operated

Pressure Sensor Travel Front Att achm ent

Engine Control Dial

EC Motor

T1HG-02-01-001

T2-1-16


T2-1-17

SYSTEM / Control System Attachment Operation Speed Increase Control (Only on the machines equipped with the auxiliary mode switch (Optional).)

When all conditions exist, the maximum engine speed is increased to the speed set by Dr. EX.

Engine Speed

Function: Increases the maximum engine speed to the attachment (hydraulic breaker, secondary crusher, primary crusher or vibrating hammer) operating engine speed set by Dr. EX when the attachment is operated. Operation: When the following conditions exist, the MC drives the EC motor so that the engine maximum speed is increased to the attachment operating speed set by Dr. EX when the attachment is operated. Operating Conditions: Dr. EX: Resets the maximum engine speed to a faster (+) attachment (hydraulic breaker, secondary crusher, primary crusher, or vibrating hammer) operating speed in the service mode. Engine Control Dial: Maximum Speed Position Power Mode Switch: HP Mode Auxiliary: In Operation Work Mode Switch: Attachment Mode Auxiliary Mode Switch (Optional): Attachment position (hydraulic breaker, secondary crusher, primar y crusher, or vibrating hammer) reset by Dr. EX. NOTE: When the P mode engine speed is preset to a slower speed in the Dr. EX service mode, the maximum engine speed won’t be increased when operating the attachment.

T2-1-18

Minimum Speed

Maximum Speed


ANIMATION


Pressure Sensor

Auxil iary(O ptio nal) Engine Control Dial

EC Motor

Power Mode Switch HP Mode Work Mode Switch Auxil iary Mode Switch (Optional)

Att achm ent Mode

T178-02-01-011

T2-1-19

ANIMATION

SYSTEM / Control System Attachment Operation Speed Limit Control (Only on the machines equipped with the auxiliary mode switch (Optional).)

Engine Speed

When all conditions exist, the maximum engine speed is reduced to the speed set by Dr. EX.

Function: Decreases the maximum engine speed to the attachment (hydraulic breaker, secondary crusher, primary crusher or vibrating hammer) operating engine speed set by Dr. EX when the attachment mode is selected. Operation: When the following conditions exists, the MC drives the EC motor so that the engine maximum speed is reduced to the attachment operating speed set by Dr. EX when the attachment mode is selected.

Minimum Speed

Maximum Speed


Operating Conditions: Dr. EX: Resets the maximum engine speed to a slower (−) attachment (hydraulic breaker, secondary crusher, primary crusher, or vibrator) operating speed in the service mode. Work Mode Switch: Attachment Mode Auxiliary Mode Switch (Optional): Attachment position (hydraulic breaker, secondary crusher, primar y crusher, or vibrating hammer) set by Dr. EX.

EC Motor

Work Mode Switch Auxil iary Mode Switch (Optional)

Att achm ent Mode

T178-02-01-012

T2-1-20

SYSTEM / Control System Engine Learning Control Function: Inputs the governor lever stopper positions on both the STOP and FULL sides as the standard data to control the engine. Operation:When the learning switch in the rear console is turned to the engine learning position, the EC motor is driven by the signals from the MC. The EC motor moves the governor lever from the IDLE to FULL and to STOP positions in this order. The EC sensor detects the stopper positions of the governor lever on both the FULL and STOP sides and sends each stopper position signal to the MC. The MC stores these signals in its memory.

IMPORTANT: Be sure to perform the engine learning if the following repair work is done. (Refer to the Troubleshooting Section in T/M.) After performing the engine learning, check that the engine learning has been performed correctly using Dr. EX. • After the engine, engine control cable, or EC motor has been removed or replaced. • After the MC has been replaced. NOTE: The engine learning is not required when the batteries are replaced.

Learning Switch

Key Switch

EC Sensor

EC Motor

T178-02-01-014

T2-1-21


T2-1-22

SYSTEM / Control System PUMP CONTROL The pump control system has the following functions: •

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Speed Sensing Control Slow Speed Torque Increase Control Pump 1 Flow Rate Limit Control Pump 2 Flow Rate Limit Control Pump 3 Flow Torque Decrease Control ∗ ∗ ∗

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Pump Control System Layout Pressure Sensor Travel

N Sensor Pump 2 Delivery Pressure Sensor

Engine Control Dial


Pump 3 Delivery Pressure Sensor (Optional)

Auxili ary(Op tion al)

Torque Control Solenoid Valve Max. Pump 2 Flow Rate Limit Solenoid Valve

Max. Pump 1 Flow Rate Limit Solenoid Valve (Optional)

T178-02-01-002

T2-1-23

SYSTEM / Control System Speed Sensing Control Function: Controls the pump flow rate in response to engine speed changes due to variations in load so that the engine output can be utilized more efficiently. (Engine stall is prevented when the machine operates under adverse conditions such as operating at high altitude.) Q

Operation: 1. The target engine operating speed is set by controlling the engine control dial. 2. The MC calculates the difference in speed between the target operating speed and the actual operating speed monitored by the N sensor. Then, the MC sends signals to the torque control solenoid valve. 3. The torque control solenoid valve delivers pilot pressure oil in response to the signals received from the MC to the pump regulator, controlling the pump flow rate. 4. If the engine load increases and the actual engine operating speed becomes slower than the target operating speed, the pump swash angle is reduced so that pump flow rate will be reduced. Therefore, the engine load is reduced, preventing engine stall. 5. If the actual engine operating speed becomes faster than the target operating speed, the pump swash angle is increased so that the pump flow rate will increase, by which the engine output can be utilized more efficiently.

Flow Rate

T2-1-24

Pump P-Q Curve

Pressure

P

ANIMATION


N Sensor Engine Control Dial

Torque Control Solenoid Valve

T178-02-01-015

T2-1-25

SYSTEM / Control System Slow Speed Torque Increase Control Q

Function: Allows the machine to travel at the maximum pump flow rate when the engine is running at slow speed. When travel operation is made with the engine running at slow speed, normally, the hydraulic pump delivers pressure oil at the flow rate corresponding to point A on the P-Q curve illustrated to the right. Therefore, if any difference exists between pump 1 and pump 2 flow rate, the machine will mistrack. To prevent mistracking, the pump P-Q curve is raised so that, when traveling the machine with the engine running at slow speed, the pump delivers pressure oil at the flow rate corresponding to point B (maximum flow rate).

Flow Rate

Operation: 1. When the engine speed set by the engine control dial is slow, the MC processes signals from the travel pressure sensor, and pump 1 and 2 delivery pressure sensors and sends control signals to the torque control solenoid valve. 2. The torque control solenoid valve delivers the pilot pressure oil corresponding to the signals received from the MC to the regulator, increasing the pump flow rate. NOTE: If the MC stops the slow speed torque increase control when the front attachment is operated while traveling, the pump flow rate will be reduced quickly, developing a shock load to the machine. Therefore, the MC maintains the slow speed torque increase control even if the front attachment is simultaneously operated while traveling.

T2-1-26

B

A

Increased Torque P-Q Curve

Normal P-Q Curve

Pressure

P

ANIMATION

SYSTEM / Control System Pressure Sensor Travel



Engine Control Dial


T178-02-01-016

T2-1-27

SYSTEM / Control System Pump 1 Flow Rate Limit Control (Only on the machines with the auxiliary sensor (Optional).)

Pump 2 Flow Rate Limit Control (Only on the machines with the auxiliary sensor (Optional).)

Function: Limits the maximum pump 1 flow rate when a front attachment (mainly a vibrating hammer) is used.

Function: Limits the maximum pump 2 flow rate when a front attachment (mainly a hydraulic breaker) is used.

Operation: 1. When a front attachment is used, the MC receives signals from the pressure sensor (auxiliary). 2. In response to the signals arriving from the pressure sensor, the MC drives the maximum pump 1 flow rate limit solenoid valve (optional) to reduce the maximum pump flow rate.

Operation: 1. When a front attachment is used, the MC receives signals from the pressure sensor (auxiliary). 2. In response to the signals arriving from the pressure sensor, the MC drives the maximum pump 2 flow rate limit solenoid valve (optional) to reduce the maximum pump flow rate.

NOTE: In proportion to the attachment control pedal stroke, the maximum pump flow rated is reduced. The minimum pump swash setangle for a front attachment (hydraulic breaker, secondary crusher, primary crusher or vibrating hammer) can be set in the service mode of Dr. EX.

NOTE: In proportion to the attachment control pedal stroke, the maximum pump flow rated is reduced. The minimum pump swash setangle for a front attachment (hydraulic breaker, secondary crusher, primary crusher or vibrating hammer) can be set in the service mode of Dr. EX.

Q Flow Rate

Maximum flow rate is reduced.

Pump P-Q Curve

Pressure

T2-1-28

P

ANIMATION

SYSTEM / Control System Pressure Sensor

Auxili ary(Op tion al)

Maximum Pump 2 Flow Rate Limit Solenoid Valve(Optional) Maximum Pump 1 Flow Rate Limit Solenoid Valve

T178-02-01-017

T2-1-29

ANIMATION

SYSTEM / Control System Pump 3 Torque Decrease Control (Only on the machines equipped with pump 3 (Optional).) Function: Reduces pump 1 and pump 2 driving torque to prevent the engine from stalling, utilizing the engine output efficiently when the pump 3 driving torque increases.

Q

Flow Rate

Operation: When the MC receives signals from pump 3 delivery pressure sensor (optional), the MC drives the torque control s olenoid valve so that pump 1 and pump 2 flow rates are reduced. Thereby, the total pump 1, 2, and 3 driving torque is maintained not to exceed the engine output, utilizing the engine output efficiently.

P-Q curve is controlled in proportion to pump 3 delivery pressure.

Normal P-Q Curve

Pressure

P



T178-02-01-018

T2-1-30


T2-1-31

SYSTEM / Control System VALVE CONTROL The valve control system functions as follows: •

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Power Digging Control Auto-Power Lift Control Arm Flow Rate Control Arm Regenerative Control Travel Motor Swash Angle Control Auxiliary Flow Rate Control ∗

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T2-1-32

ANIMATION

SYSTEM / Control System Valve Control System Layout Pressure Sensor Learning Switch Swing Boom Raise Arm Roll- In Auxili ary(Op tion al)

Key Switch



Engine Control Dial

Power Digging Switch

Hydraulic Oil Temperature Sensor

Fast Pump 2 Control Pressure Sensor

Slow

Travel Mode Switch

Pump 1 Control Pressure Sensor Solenoid Valve Unit SG SC SE SI

Main Relief Valve

Auxil iary Flow Rate Control Solenoid Valve (Optional)

Auxil iary Flow Rate Control Valve

Travel Motor

Swash Angle Control Valve

Arm Regen erati ve Valve

Arm Flow Rate Contr ol Valve

T2-1-33

T178-02-01-003

SYSTEM / Control System Power Digging Control Functi Function: on: Increa Increases ses diggi digging ng force force by temporari temporarily ly increasing relief pressure. Operation: Operation: For maximum 8 seconds seconds after the power power digging switch is turned ON, the MC continuously activates solenoid valve unit(SG). Solenoid valve unit (SG) delivers the pilot oil pressure to the relief valve, increasing the relief set-pressure. (Refer to the COMPONENT OPERATION / Control Valve group.)

T2-1-34

ANIMATION


Power Digging Switch

Main Relief Valve

Solenoid Valve Unit SG

T178-02-01-019

T2-1-35

SYSTEM / Control System Auto-Power Lift Control Function: Increases oil pressure when raising the boom. Operation: The MC activates solenoid valve unit (SG) when signals from pressure sensor (boom raise) and pump 1 delivery pressure sensor meet the following conditions. Solenoid valve (SG) delivers the pilot pressure oil to the relief valve, increasing the relief setpressure. (Refer to the COMPONENT OPERATION / Control Valve group.) Operating Conditions: Boom Raise Pressure Sensor: Outputting signals. (The boom must be raised to a certain extent.) Pump 1 delivery Pressure Sensor: High pressure. Arm Roll-In Pressure Sensor: Output zero. (The control lever is in neutral.) NOTE: This control system is activated during combined operations (except for the arm roll-in combined operation).

T2-1-36

ANIMATION


Boom Raise Arm Roll- In


Main Relief Valve Solenoid Valve Unit SG

T178-02-01-020

T2-1-37

SYSTEM / Control System Arm Flow Rate Control Function: Gives pressure oil from pump 2 priority to flow to the swing motor spool over the arm 1 spool to ensure swing power. Operation: The MC activates solenoid valve unit (SE) when signals from the pump 2 delivery pressure sensor and pressure sensors (swing and arm roll-in) meet the following conditions. Solenoid valve unit (SE) delivers the pilot pressure oil to the arm flow rate control so that the parallel oil passage to the arm 1 spool is restricted. Thereby, the swing spool has priority, ensuring swing motor power, preventing the upperstructure from being rotated by the arm reaction force when the arm is rolled in. (Refer to the COMPONENT OPERATION/Control Valve group.) Operating Conditions: Pump 2 Delivery Pressure Sensor: High pressure. Swing Pressure Sensor: Must have some output. (The swing control lever is stroked to a certain extent.) Arm Pressure Sensor: Outputting signals.

T2-1-38

ANIMATION


Pressure Sensor

Swing Arm Roll- In


Solenoid Valve Unit

SE

Arm Flow Rate Contr ol Valv e

T2-1-39

T178-02-01-021

SYSTEM / Control System Arm Regenerative Control Function: Accelerates the arm roll-in speed to prevent arm hesitation during arm roll-in operation. Operation: The MC activates the solenoid valve unit (SC) so that solenoid valve delivers the pilot pressure oil to shift the arm regenerative valve when signals from the pump 2 delivery pressure sensor, swing pressure sensor, arm roll-in pressure sensor, and boom raise pressure sensor meet the following conditions. When the arm regenerative valve is shifted, the return circuit from the arm cylinder rod side to the hydraulic oil tank is closed. Then, the return oil from the cylinder rod side is combined with the pressure oil from the pump and is routed to the cylinder bottom, accelerating the arm roll-in speed and preventing arm hesitation. (Refer to the COMPONENT OPERATION / Control Valve group.) Operating Conditions: Pump 2 Delivery Pressure Sensor: Low pressure. (The arm doesn’t need much power.) Arm Roll-In Pressure Sensor: High output. (The arm control lever stroke is large.) Swing or Boom raise Sensor: Outputting signal. NOTE: To improve arm leveling performance, the MC gradually activates solenoid valve unit (SC) when the hydraulic oil temperature is at 0 to 10 C (32 to 50 F). °

°

T2-1-40

ANIMATION


Swing Boom Raise Arm Roll- In


Hydraulic Oil Temperature Sensor

Solenoid Valve Unit SC

Arm Regen erat ive Valve

T2-1-41

T178-02-01-022

SYSTEM / Control System Travel Motor Swash Angle Control Function: Controls the travel mode. Operation: When the travel mode switch is in the SLOW position, the travel motor swash angle is kept in the maximum angle so that the travel speed is slow. When the MC receives the signals from the travel pressure sensor, pump 1 and 2 delivery pressure sensors, pump 1 and 2 control pressure sensors under the following conditions with the travel mode switch in the FAST position, the MC activates the solenoid valve unit (SI). Then, the solenoid valve (SI) delivers the pilot pressure oil to the travel motor swash angle control valve, reducing the swash angle to the minimum so that the travel speed increases. ZAXIS200,225USR,225US,230 Operating Conditions: Travel Pressure Sensor: ON Front Attachment Pressure Sensor: OFF Pump 1 and 2 Delivery Pressure Sensor: Either pump delivery pressures are low. Pump 1 and 2 Control Pressure Sensor: Either pump control pressures are high. •

NOTE: When one side track is raise off the ground using the front attachment and is rotated, the one side pump control pressure increases, allowing the raised track to rotate at fast speed. When the machine is traveling in the fast mode, even if the front attachment is operated (the front attachment pressure sensor is turned ON), the travel mode is kept unchanged in the fast mode. • ZAXIS270 Operating Conditions: Travel Pressure Sensor: ON Front Attachment Pressure Sensor: OFF Pump 1 and 2 Delivery Pressure sensor: Both of pump 1 and 2 delivery pressure are low. Pump 1 and 2 Control Pressure Sensor: Both of pump 1 and 2 control pressures are high.

NOTE: When one side track is raise off the ground using the front attachment and is rotated, the one side pump displacement target angle remains small so that the travel motor speed does not increase.

T2-1-42

ANIMATION

SYSTEM / Control System Pressure Sensor Travel Pump 2 Delivery Pressure Sensor


Travel Mode Switch Fast Mode Pump 2 Control Pressure Sensor Pump 1 Control Pressure Sensor Solenoid Valve Unit

SI

Travel Motor

Swash Angle Control Valve T178-02-01-023

T2-1-43

SYSTEM / Control System Auxiliary Flow Rate Control (Only on the machines equipped with the auxiliary pressure sensor and auxiliary flow rate control solenoid valve) Function: Restricts the oil flow to the auxiliary spool when the combined operation of the swing, boom raise, and arm roll-in is made while operating a front attachment using the auxiliary spool to maintain controllability of the combined operation. Operation: The MC activates the auxiliary flow rate control solenoid valve (optional) so that the oil flow to the auxiliary spool is restricted under the following conditions. Operating Conditions: Auxiliary Pressure Sensor: ON Swing, Boom Raise, Arm Roll-In Pressure Sensors: ON

T2-1-44

ANIMATION


Swing Boom Raise Arm Roll- In Auxil iary( Opti onal )

Auxil iary Flow Rate Control Solenoid Valve (Optional)


T178-02-01-024

T2-1-45

SYSTEM / Control System OTHER CONTROLS Boom Electronic Cushion Control (ZAXIS225US) Function: Reduces the shock which may occur when the boom reaches to its full stroke position at boom raise operation by functioning the electronic cushion in the speed reduction area. Operation:The signal from the boom angle sensor comes into MC at boom raise operation. MC calculates the boom angle by this signal. When the boom angle reaches to the speed reduction area, MC controls the boom electronic cushion solenoid valve to decrease the boom raise pilot pressure.

Speed Reduction Area

Position where speed reduction begins

Boom Full Stroke Position

T1GF-02-01-001

T2-1-46

ANIMATION


Boom Angle Sensor

Boom Raise

Boom Electronic Cushion Solenoid Valve

Signal Control Valve

1 Control Valve

Boom 2 1

Boom 1 1

T1GF-02-01-002

T2-1-47

SYSTEM / Control System Work Mode Control Two work modes, digging and front attachment, are available by operating the work mode switch. •

•

Digging Mode: Normal control is performed. Front Attachment Mode: Functions only when a front attachment in the optional kit is operated. The engine speed (see T2-1-18 and 20) and pump flow rate (see T2-128) are controlled so as to match the installed front attachment operation in response to the movement of the auxiliary valve spool. The engine speed and pump flow rate control settings are made by using Dr. EX.

T2-1-48

ANIMATION

SYSTEM / Control System Travel Alarm Control (Only on the machines equipped with the travel alarm device) Function: Sounds the buzzer while traveling. Operation: As long as the MC receives signals from the travel pressure sensor when travel operation is made, the MC sends out signals to the travel alarm device to sound the buzzer. NOTE: After traveling continuously for more than 13 seconds, the buzzer can be stopped with the buzzer deactivation switch.

Pressure Switch Travel

Travel Alarm Device (Optional)

Buzzer Deactivation Switch (Optional)

Buzzer (Optional) T178-02-01-025

T2-1-49


T2-1-50

SYSTEM / Hydraulic System OUTLINE The hydraulic system is broadly divided into two circuits, the main circuit and the pilot circuit. Main Circuit: Power Source Main Pumps

Controller →

Actuator

Control Valves

→

Motors Cylinders Front Attachmens (Optional)

Pilot Circuit: Power Source Pilot Pumps

Controller →

Pilot Circuit

Pilot Valves

→

Operation Control Circuit

Pump Regulator

Pump Control Circuit

Solenoid Valve Unit

Valve Control Circuit


Swing Parking Brake Release Circuit

Boom Electronic Cushion

Travel Motor Swash Angle Control Circuit

Solenoid Valve

Hydraulic Oil Heat Circuit

(Only ZAXIS225US)

T2-2-1

SYSTEM / Hydraulic System PILOT CIRCUIT Outline: Pressure oil from the pilot pump is used to operate the operation control circuit, pump control circuit, valve control circuit, swing parking brake release circuit, travel motor swash angle control circuit, and hydraulic oil heat circuit. •

T2-2-2

ANIMATION

SYSTEM / Hydraulic System Operation Control Circuit

Travel Pilot Valve

Left Pilot Valve

Swing Parking Brake Release Circuit

Right Pilot Valve

Auxiliar y Pilo t Valve


Swing Motor



Pump Control Circuit Maximum Pump 2 Flow Rate Control Solenoid Valve

Pilot ShutOff Valve




Hydraulic Oil Heat Circuit






Maximum Pump 1 Flow Rate Control Solenoid Valve (Optional)

To Contr ol Valve Spools Auxil iary Flow Comb inin g Solenoid Valve (When the auxiliary spool is used.)



Flow Combiner Valve

Bucket Flow Rate Control Valve



Regulator

Boom Anti-Drift Valve

Auxil iary Flow Rate Contr ol Solenoid Valve (When the auxiliary spool is used.)

Arm Ant i-Drif t Valve Auxil iary Flow Comb iner Valve Bypass Cut Valve Auxil iary Flow Contr ol Valv e



Valve Control Circuit





Main Relief Valve Arm Regen erat ive Valve Arm Flow Rate Contr ol Valv e



VC Solenoid Valve Unit Travel Motor

Hydraulic Oil Tank

Control Valve

Suction Filter

Travel Motor Swash Angl e Contro l Circuit Travel Motor

NOTE: *Boom Electronic Cushion Solenoid Valve is ZAXIS225US Only.

T2-2-3

Relief Valve

Pilot Filter

Pilot Pump

SYSTEM / Hydraulic System Operation Control Circuit The pilot valves control the pressure oil from the pilot pump to operate the control valve spools. •

•

The signal control valve is provided between the pilot valves and the control valve. The shockless valve (in the boom lower circuit) built in the signal control valve dampens quick spool movement in the control valve. (Refer to the COMPONENT OPERATION / Signal Control Valve group.)

ZAXIS225US:

•

The boom electronic cushion solenoid valve is provided between the pilot valve (right) and the signal control valve on ZAXIS225US. This valve reduces the shock which may occur when the boom reaches to its full stroke position. (Refer to SYSTEM / Control System group.)

Pilot Valve (Right)



T2-2-4

T1GF-02-02-001

SYSTEM / Hydraulic System ZAXIS200,225USR,230,270 Travel Pilot Valve

Pilot Valve (Left)

Pilot Valve (Right)

Shockless Valve

9 10 11 12

4 3


9

2

1

10

7 6

5

11 12

7

2

1

8

1

4

3

5

8

3

6

Control Valve Pilot Pump

T178-02-02-005

1 - Boom Raise 2 - Boom Lower 3 - Arm Roll-Out

4 - Arm Roll-In 5 - Left Swing 6 - Right Swing

7 - Bucket Roll-In 8 - Bucket Roll-Out 9 - Left Travel Forward

T2-2-5

10 - Left Travel Reverse 11 - Right Travel Forward 12 - Right Travel Reverse

SYSTEM / Hydraulic System Pump Control Circuit (Refer to the COMPOMENT OPERATION / Pump Device group.) •

Pump Flow Rate Control by Flow Rate Control Pressure Pi Pressure oil from the pilot valve is selected by the shuttle valves in the signal control valve. Then, the selected pressure oil is routed further to either the pump 1 flow rate control valve or the pump 2 flow rate control valve in the same signal control valve, shifting either of the flow rate control valves. •

•

When either the pump 1 flow rate control valve or the pump 2 flow rate control valve is shifted, the pilot pressure oil from the pilot pump is routed to either main pump 1 or main pump 2 as flow rate control pressure Pi.

NOTE: When the boom (raise/lower), arm (rollin/out), bucket (roll-in/out), auxiliary, and/or travel (right) function is operated, flow rate control pressure Pi is routed to main pump 1. When the boom (raise/lower), arm (rollin/out), swing (right/left), and/or travel (left) function is operated, flow rate control pressure Pi is routed to main pump 2. •

Torque Control (Speed Sensing) by Torque Control Solenoid Valve After the pilot oil pressure from the pilot pump is regulated by the torque control solenoid valve, the regulated pilot oil pressure is routed to main pum p 1 and 2 as speed sensing pressure Ppc. •

T2-2-6

ANIMATION

SYSTEM / Hydraulic System

Travel (Left)

Swing

Travel (Right)

Arm

Boom

Bucket

Signal control Valve

Pump 1 Flow Rate Control Valve Pump 2 Flow Rate Control Valve

Control Valve

Torque Control Solenoid Valve Pilot Pump

Pump 2

Pump 1

T178-02-02-006

T2-2-7

SYSTEM / Hydraulic System Valve Control Circuit (Refer to the COMPONENT OPERATION / Control Valve and Travel Device groups.) • The following valves are controlled by pressure oil from the pilot valves, solenoid valve unit (SC, SE, and SG), the flow combiner valve control spool in the signal control valve, and the bucket flow rate control valve control spool. •

•

•

•

•

•

•

•

•

•

Boom Lower Pilot Pressure: Boom Anti-Drift Valve Arm Roll-In Pilot Pressure: Arm Anti-Drift Valve Auxiliary Pilot Pressure: Auxiliary Flow Combiner Valve, Bypass Shut-Out Valve (When the auxiliary spool is used.) Solenoid Valve SC: Arm Regenerative Valve Solenoid Valve SE: Arm Flow Rate Control Valve Solenoid Valve SG: Main Relief Valve (increasing the set-pressure) Auxiliary Flow Rate Control Solenoid Valve: Auxiliary Flow Rate Control Valve (When the auxiliary spool is used.) Auxiliary Flow Combining Solenoid Valve: Boom, Arm, and Bucket Pilot Pressure Flow Combiner Valve Control Spool: Flow Combiner Valve Bucket Flow Rate Control Valve Control Spool: Bucket Flow Rate Control Valve

T2-2-8


Travel (Right)

Arm Roll- In

Boom Lower

Auxil iary


4 2 Main Relief Valve


Auxil iary Flow Combining Solenoid Valve

Flow Combiner Valve Control Spool Bucket Flow Rate Control Valve Control Spool Auxil iary Flow Comb iner Valve Flow Combiner Valve

Auxil iary Flow Rate Control Solenoid Valve

Bucket Flow Rate Control Valve Arm Anti -Drif t Valve

2

Solenoid Valve Unit Boom Anti-Drift Valve 4

SG SC SE

Bypass Shut-Out Valve

Pilot Pump Arm Regenerative Valve

Arm F low Rate Control Valve T178-02-02-007

T2-2-9

SYSTEM / Hydraulic System Swing Parking Brake Release Circuit (Refer to the COMPONENTS OPERATION / Swing Device group.) When the front attachment and/or swing function is operated, the pilot oil pressure selected by the shuttle valves in the signal control valve shifts the swing parking brake release spool. •

•

Consequently, the release signal oil pressure is routed to the swing motor, releasing the swing parking brake.

Travel Motor Swash Angle Control Circuit (Refer to the COMPONENTS OPERATION / Travel Device group.) The pilot oil pressure from solenoid valve SI regulates the travel motor swash angle control valve. •

Hydraulic Oil Heat Circuit (Refer to the COMPONENTS OPERATION / Others (Upperstructure) group.) When the pilot shut-off valve is closed, the pilot oil pressure is routed to the signal control valve so that hydraulic oil is warmed while passing through the orifice in the signal control valve. •

•

The warmed pilot pressure oil flows to the signal control valve and pilot valves so that the pilot system components are warmed.

T2-2-10


Swing

Arm

Boom

Bucket

Orifice


Swing Parking Brake Release Spool

Solenoid Valve Unit

Swing Motor Control Valve

SI

Travel Motor

T178-02-02-008

Swash Angle Control Valve

T2-2-11

SYSTEM / Hydraulic System MAIN CIRCUIT Outline Main pumps (1 and 2) draw hydraulic oil from the hydraulic oil tank. Main pump 1 and main pump 2 deliver pressure oil to the 4-spool control valve and the 5-spool control valve respectively. •

•

•

•

Delivered pressure oil is routed to the motor(s) or cylinder(s) in response to operation(s) of the spool(s) in the control valve(s). The return oil from the motor(s) and/or cylinder(s) flows back to the hydraulic oil tank via the control valve and/or the oil cooler. When the oil temperature is low (high viscosity), the oil flow resistance increases in the oil cooler, which opens the bypass check valve, allowing hydraulic oil to return directly to the hydraulic oil tank without passing through the oil cooler.

T2-2-12

ANIMATION


Tra vel Mo tor (L ef t)

Tra vel Mot or (Rig ht ) Bucket Cylinder

Front Attachment (s)

Control Valve

Boom Cylinder 4-Spool Side

Arm Cylin der Travel (Left)

Travel (Right)

Auxil iary

Bucket

Boom 2

Boom 1

Arm 1

Arm 2

Swing 5-Spool Side

Bypass Check Valve Swing Motor Oil Cooler

Main Pump 2

Main Pump 1

Suction Filter

T2-2-13

Hydraulic Oil Tank

SYSTEM / Hydraulic System Neutral Circuit When the control lever is in neutral, pressure oil from the main pump passes through the control valve and returns to the hydraulic oil tank. •

Single Operation Circuit Pressure oil from main pump 1 is routed to the 4spool control valve and is further routed to each spool of the travel (right), bucket, boom 1, and arm 2. •

•

•

Pressure oil from main pump 2 is routed to the 5spool control valve and is further routed to each spool of the swing, arm 1, boom 2, and travel (left). The boom and arm are actuated by pressure oil from two main pumps. Pressure oil from each main pump is combined and supplied together.

T2-2-14

ANIMATION


Travel Motor (Left)

Travel Motor (Right)

Control Valve

Front Attachment

Travel (Left)

Travel (Right) Bucket Cylinder

Auxil iary

Bucket Arm Cylind er Boom 1

Boom Cylinder

Boom 2

Swing Motor Arm 1 Arm 2

Swing

5-Spool Side

4-Spool Side Pump 2

Pump 1

T178-02-02-001

T2-2-15

SYSTEM / Hydraulic System Combined Operation Circuit • Swing and Boom Raise Operation When the boom is raised while swinging, the pilot oil pressure shifts the swing, boom 1, and boom 2 spools. •

•

•

•

Pressure oil from pump 1 flows into the boom cylinders via the parallel circuit and the boom 1 spool, raising the boom. Pressure oil from pump 2 flows into the swing motor via the swing spool. At the sam e time, pressure oil from pump 2 flows through the parallel circuit and after being combined with pressure oil from pump 1, f lows into the boom cylinders, raising the boom together with pressure oil from pump 1.

T2-2-16

ANIMATION


Parallel Circuit

Boom 2

Boom 1

Boom Cylinder

Swing Motor

Swing Parallel Circuit

Pump 2

Pump 1

T178-02-02-002

T2-2-17

SYSTEM / Hydraulic System •

Travel and Arm Roll-In Operation When the arm is rolled in while traveling, the pilot oil pressure shifts the travel, arm 1 and 2 spools. •

•

•

•

•

•

At the same time, the right travel pilot oil pressure shifts the flow combiner valve control spool in the signal control valve. Pressure oil from the flow combiner valve control spool is routed to the flow combiner valve, shifting the flow combiner valve. Pressure oil from pump 1 drives the right travel motor via the right travel spool. At the same time, pressure oil from pump 1 passes through the flow combiner valve and the left travel spool and drives the left travel motor. Pressure oil from pump 2 flows into the arm cylinder via the arm 1 spool, moving the arm. Consequently, pressure oil from pump 2 is used only to operate the arm. Pressure oil pump 1 is equally routed to both the right and left travel motors, ensuring that the machine can travel straight.

T2-2-18

ANIMATION


Pilot Pressure Oil from Flow Combiner Valve Control Spool in Signal Control Valve

Travel Motor (Left)

Left Travel

Travel Motor (Right)

Right Travel

Arm Cylin der

Arm 1

5-Spool Side 4-Spool Side

Pump 2

Pump 1

T178-02-02-003

T2-2-19

SYSTEM / Hydraulic System Auxiliary Circuit When a front attachment such as a hydraulic breaker is operated, the pilot pressure oil from the hydraulic breaker pilot valve shifts the auxiliary flow combiner valve and bypass shut-out valve. •

•

Therefore, the neutral circuit in the 4-spool control valve is blocked so that pressure oil from pump1 is routed to the auxiliary spool via the auxiliary flow combiner valve.

T2-2-20

NOTE: During boom (raise or lower), arm (roll-in or roll–out), bucket (roll-in or roll–out), and/or right travel operation, pilot pressure oil is routed to port SN from the signal pilot pressure control valve so that the aux. flow combiner valve is not shifted. (Refer to the SYSTEM / Control System group.)

ANIMATION


Pilot Oil Pressure from Hydraulic Breaker Pilot Valve Auxil iary Flow Combining Solenoid Valve

Auxil iary Flow Combiner Valve

Pilot Pressure from Signal Control Valve SN

SM

Front Att achm ent Neutral Circuit

Auxil iary

Bypass Cut Valve

Pump 2

Pump 1

T178-02-02-004

T2-2-21

SYSTEM / Hydraulic System (Blank)

T2-2-22

SYSTEM / Electrical System OUTLINE The electrical circuit is broadly divided into the main circuit, monitor circuit, and control circuit.

• Main Circuit The engine and accessory operation related circuit. • Monitor Circuit The electrical circuit group consists of the monitors, sensors, and switches, and displays the machine operation status. • Control Circuit (Refer to the SYSTEM / Control System group.) The control circuit is categorized into the engine, pump, and valve control circuits. Each circuit consists of the actuators such as solenoid valves, MC (main controller), switch boxes, sensors and pressure switches.

T2-3-1

SYSTEM / Electrical System MAIN CIRCUIT The major functions and circuits in the main circuit are as follows. •

•

•

•

•

•

•

•

Electric Power Circuit: Supplies all electric power to all electrical systems on this machine. [Key Switch, Batteries, Fuses (Fuse Boxes, Fusible Links), Battery Relay] Indicator Light Check Circuit Checks all indicator bulbs for burning. Accessory Circuit Becomes operative when the key switch is turned to the ACC position. Preheat Circuit Assists the engine to start in cold weather. [Key Switch, QOS Controller, Coolant Switch, Glow Plug Relay, Glow Plugs ] Starting Circuit Starts the engine. [Key Switch, Starter, Starter Relay] Charging Circuit Charges the batteries. [ Alternator, Regulator ] Serge Voltage Prevention Circuit Prevents the occurrence of serge voltage developed when stopping the engine. [Load Damp Relay] Engine Stop Circuit Stops the engine using the EC motor. [MC, EC Motor ]

T2-3-2

ANIMATION

SYSTEM / Electrical System ELECTRIC POWER SWITCH: OFF)

CIRCUIT

(KEY

The battery ground terminal is connected to the vehicle frame. Current from the battery plus terminal flows as shown below when the key switch is OFF.

Battery ↓

Fusible Link

→ Glow Plug Relay Power 

→ Terminal #1: Radio (Backup Power)

Monitor (Backup Power)

→ Key Switch (B) → Load Damp Relay → Fuse Box

ICX Controller (Backup Power) → Terminal #2: MC (Power) → Terminal #3: MC (EC Motor Power) → Terminal #10: Optional

Key Switch

Battery

Load Damp Relay

Glow Plug Relay

Radio, Monitor, ICX Controller

Optional

MC MC

T178-02-03-001

T2-3-3

ANIMATION

SYSTEM / Electrical System INDICATOR LIGHT CHECK CIRCUIT (KEY SWITCH: ON) •

•

•

When the key switch is turned ON, terminal B is connected to terminals ACC and M in the key switch. Current from key switch terminal M excites the battery relay. Therefore, the battery current enters the monitor controller via the battery relay and fuse #6 and checks the indicator bulbs.

Key Switch

Battery

Battery Relay Fuse Box

Monitor Controller

T178-02-03-002

T2-3-4

ANIMATION

SYSTEM / Electrical System ACCESSORY CIRCUIT •

•

When the key switch is turned to the ACC position, terminal B is connected to terminal ACC in the key switch. Current from key switch terminal ACC flows to horn (fuse #14), radio (fuse #15), lighter (fuse #16), cab light (fuse #17) and auxiliary (fuse #18) through the fuse box, making each accessory operable.

Fuse Box

Horn Radio Lighter Cab Light Auxil iary

T178-02-03-003

T2-3-5

SYSTEM / Electrical System PREHEAT CIRCUIT (KEY SWITCH: ON / START) •

•

•

•

When the key switch is turned ON or to the START position, terminal B is connected to terminal M in the key switch. Current from terminal M is routed to QOS controller terminal #1 through fuse #19. When the key switch is ON or in the START position with the coolant switch OFF (when the coolant temperature is 10 °C (50 °F) or below), QOS controller terminal #4 is connected to terminal #5 (ground). Accordingly, the glow plug relay is turned ON, routing current to the glow plugs so that preheating begins. When preheating begins, QOS controller terminal #6 is connected to terminal #5 for 8 seconds, turning the preheat indicator ON. (When preheating is not performed, the preheat indicator comes ON for 2 seconds for indicator light check.)

T2-3-6

NOTE: After preheating has been performed, heating will continue for approx. 30 seconds after the engine starts.

ANIMATION

SYSTEM / Electrical System

Monitor

Coolant Temperature Switch

Preheat Indicator QOS Controller

Key Switch

Fuse Box

Glow Plug Relay

Glow Plug T178-02-03-004

T2-3-7

ANIMATION

SYSTEM / Electrical System STARTING START) •

•

•

•

•

•

•

CIRCUIT

(KEY

SWITCH:

When the key switch is turned to the START position, terminal B is connected to terminals M and ST in the key switch.

Starter Relay Operation When the key switch is turned to the START position, key switch terminal B is connected to terminal ST so that current is routed to the base in transistor (Q2) through resistance R4 in the starter relay. Then, transistor (Q2) is turned ON, allowing current to flow to coil (L) in the starter relay. Therefore, starter terminal B is connected to terminal C, rotating the starter. •

As current from terminal M excites the battery relay, battery current is routed to starter terminal B and starter relay terminal B via the battery relay. Key switch terminal ST is connected to starter relay terminal S so that current flows through the starter relay coil.

•

Then, the starter relay is turned ON, allowing current to flow from starter relay terminal C to starter terminal C.

•

Consequently, the relay in the star ter is turned ON so that the starter begins rotating. On the other hand, current from key switch terminal M flows to the MC via fuse #6 as a signal indicating that the key switch is in the ON or START position.

After the engine starts, the alternator starts generating electricity, increasing voltage at starter relay terminal R. When this voltage increases up to 21 to 22 V, Zener diode (Z) is turned ON so that transistor (Q1) is turned ON. Then, current to the base of transistor (Q2) is not routed, turning transistor (Q2) OFF. At this moment, starter terminal B is disconnected from terminal C, stopping the starter.

Condenser C1 is used to stabilize the operating voltage and diode D4 protects the circuit in case the battery terminals are reversely connected.

As soon as the MC receives this signal, the MC drives the EC motor, moving the governor lever to the engine start position.

Starter Relay 

 





 

To Alternator Terminal L









 

 

 





 







Starter







Key Switch



Battery T107-04-04-003

T2-3-8

ANIMATION


Key Switch

Battery

Battery Relay Starter

Fuse Box

C C

Starter Relay

EC Motor MC

T178-02-03-005

T2-3-9

ANIMATION

SYSTEM / Electrical System CHARGING CIRCUIT (KEY SWITCH: ON) •

•

•

•

After the engine starts and the key switch is released, the key switch moves to the ON position. Then, key switch terminal B is connected to terminals ACC and M in the key switch. When the alternator starts generating electricity, current flows from alternator terminal B to the batteries via the battery relay, charging the batteries. Current from alternator terminal L flows to the monitor controller and the ICX controller, turning the alternator indicator OFF.

Key Switch

Battery

Monitor Controller ICX Controller

Battery Relay

Alte rnat or

T178-02-03-006

T2-3-10

SYSTEM / Electrical System (Blank)

T2-3-11

ANIMATION

SYSTEM / Electrical System Alternator Operation The alternator consists of field coil FC, stator coil SC, and diodes D. The regulator consists of transistors (T1 and T2), Zener diode ZD, and resistances (R1 and R2). •

•

•

•

Alternator terminal B is connected to base B of transistor T1 through the circuit [B → R → RF → ( R ) → (R1)].

•

When battery relay BS is ON, the battery voltage is applied to base B of transistor T1 so that collector C is connected to emitter E. Therefore, field coil FC is grounded via transistor T1.

At the beginning, no current is flowing through field coil FC. When the rotor starts turning, alternate current is generated in stator coil SC by the rotor remanent magnetism. When current starts to flow through field coil FC, the rotor is further magnetized so that the generating voltage increases. Thereby, current flowing through field coil FC increases and generating voltage is increased further, to charge the batteries.

Alt ernat or  

 

Regulator

 





 

  

Battery







 

 

 



 







T157-04-02-008

T2-3-12

ANIMATION

SYSTEM / Electrical System Regulator Operation When generating voltage increases more than the set-voltage of Zener diode ZD, current is routed to base B of transistor T2, connecting collector C to emitter E. •

•

•

•

Then, current which was routed to base B of transistor disappears, turning transistor T1 OFF.

•

Therefore, no current flows through filed coil FC, reducing generating voltage at stator coil SC.





When generating voltage decreases lower than the set-voltage of Zener diode ZD, transistor T2 is turned OFF, causing transistor T1 to turn ON again. Then, current flows through field coil FC, increasing generating voltage at the stator coil. The above operation is repeated so that the alternator generating voltage is kept constant.









 

Battery



 



 

 



  









T157-04-02-009

T2-3-13

SYSTEM / Electrical System SERGE VOLTAGE PREVENTION CIRCUIT •

•

•

When the engine is stopped (key switch: OFF), current from key switch terminal M is disconnected, turning the battery relay OFF. The engine continues to rotate due to inertia force just after the key switch is turned OFF so that the alternator continues to generate electricity. As the generating current cannot flow to the battery, surge voltage arises in the circuit, possibly causing failures of the electronic components, such as the controller. To prevent the occurrence of surge voltage, the surge voltage prevention circuit is provided.

T2-3-14

•

•

•

When the alternator is generating electricity, generating current from alternator terminal L flows to monitor controller terminal #A-2 so that the monitor controller connects terminal #C-3 to ground. Then, current flows through the load damp relay exciting circuit, turning the load damp relay ON. Accordingly, even if the key switch is turned OFF while the engine is rotating, the battery current continues to excite the battery relay via the load damp relay until the alternator stops generating. Therefore, the battery relay is kept ON, allowing the generating current to flow to the batteries.

ANIMATION


Key Switch

Battery

Battery Relay Load Damp Relay

Alt ernat or Monitor Controller

T178-02-03-007

T2-3-15

t02_1 hitachi

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