MAN_GN_PDF_6

 BASIC PRINCIPLES PRINCIPLES

6

 FUNCTION 

Drive train main assemblies  The drive train has has the task of providing the necessary pulling and pushing forces for the movement of a vehicle in accordance with the effective road resistance. It can be divided into main assemblies ( ➜ Fig.). As it is a very complex component, the engine is described in detail in this manual in chapter 5.

Driveaway element In most cases, the driveaway element is a clutch. It temporarily interrupts the connection between the engine and gearbox, bringing the vehicle to a standstill with a gear engaged and initiating t he driveaway. On driveaway, the clutch "slips", bridging the rotational speed difference between the engine and gearbox ( ➜ page 6.14 ).

In order to ensure the drive of the commercial vehicle from a standstill through the desired partial speeds all the way to the maximum speed, the drive train must perform the following functions:

Standard gearbox In the standard gearbox with front-mounted or rear-mounted group, engine torque and engine speed are converted according to the currently required tractive force. Here, the power output, i.e. the product of the torque and engine speed, should remain as constant as possible.  The standard standard gearbox gearbox is controlled via acactuators and shifting elements operated directly or electropneumatically by the driver (➜ page 6.22 ).

 Driveaway  Conversion (adaptation) of torque and

engine speed  Balancing different engine speeds of

inner and outer wheel on cornering  Operation forwards and backwards  Operation of the engine in the opti-

mised range for consumption and exhaust gas of the characteristic map (➜ page 5.70 ).  Drive for secondary consumers

Propshafts So-called propshafts are required to transfer the engine output from the gearbox to the transfer cases and/or final drives (depending on the number of driven axles). These have shifting section toothing in order to be able to balance out the vertical movement of the axles (length compensation).

With longer wheelbases, rubber-cushioned intermediate propshaft bearings are used. Middle drive  The middle drive, also also called the final drive, consists of the axle drive with the axledrive ratio and t he differential gear.  The axle drive (➜ page 6.32 ) transforms the rotational movement of the drive shaft into a rotational movement of the axle shafts of the wheels. The gear ratio in the axle drive serves to reduce the rotational speed and increase the torque of the drive shaft.  The differential gear enables balancing balancing of the rotational speed difference between the wheels of an axle on cornering ( ➜ page 6.33 ). Planetary drive gear In the case of planetary drive axles, the torque and rotational speed of the axle shafts are transferred to the drive wheels and reinforced or reduced there in a planetary gear set, as the case may be ( ➜ page 6.26 ).

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LEGEND

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1

2

3

4

5

6

6

Drive train with planetary drive axle 6.1

1 2 3 4 5 6

Engine Clutch Standard gearbox Propshafts Middle drive Planetary drive gear

  x

6

 BASIC PRINCIPLES PRINCIPLES

 FUNCTION 

 EXAMPLE 

Drive train operating principle  The manual gearbox and and final drive have have the main task of transferring the right amount of engine torque and rotational speed to the wheels depending on the driving situation.

Tractive force  The torque of the engine is gradually gradually converted by the standard gearbox. For each engaged gear, certain torque characteristics with the corresponding rotational speeds are provided.

 The crankshaft of a commercial commercial vehicle vehicle engine ( ➜ page 5.14 ) rotates many many times faster than the wheels during driving. The same rotational speed of the crankshaft and wheels would result in very high speeds depending on the tyres and power output. As the engine speed cannot be reduced (this is only to provide adequate power output from the engine), various gear ratios have to be engaged in the standard gearbox. This enables the effective torque and tractive force to be adapted to the specific driving needs.

 The torque is boosted once again again in the final drive. Diving the effective torque at the wheels by the radius of the wheels results in the tractive force effective at the wheels.

 The 4x2 vehicle TGA 18.480 with the D2876LF12 engine with 480 hp and the ZF 16 S 221 OD Comfort Shift gearbox can be equipped with eight different drive axles for the different areas of application (required climbing capacity as well as achievable speeds in each gear).

If the tractive force characteristics for the individual gear steps are applied over the speed in a diagram and the points of the maximum power output are connected, the result is the torque or tractive force hyperbola ( ➜ Fig. page 6.3 ). This is also referred to as a tractive force chart or driving chart. It shows the tractive force characteristics depending on the speed of the vehicle.

Depending on the area of application of a commercial vehicle, various axle-drive ratios are also fitted. They determine the maximum speed and tractive force. The tractive force is a measure of the climbing capacity of a commercial vehicle.

 Axle-drive ratio  The axle-drive ratio ratio in the final drive drive influences the final speed and climbing capacity of the vehicle.

 The configuration to a theoretical maximaximum speed of more than 120 km/h is necessary so that the engine can be operated in the economical speed range at the speed of 85 to 90 km/h that is usual in traffic.  Two characteristic characteristic axles for a driveaway driveaway climbing capability of 18 % (skid limit) with 40 t total weight serve as an example:  The HY 1350 hypoid axle with i = 3.36 is a typical axle for long-distance transport. It enables a theoretical maximum speed of up to 130.6 km/h ( ➜ Fig.).  The AP 1352 planetary drive drive axle with i = 3.63 3.63 is used used abov above e all all in cons constru tructi ction on site vehicles. The theoretically achievable maximum speed is 120.9 km/h ( ➜ Fig.).

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LEGEND

v max [km/h]

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a b

Columns: a Plan Planet etar aryy driv drive e axl axle e AP 1352 1352 with gear ratio 3.63 b Hypoi poid axle HY 1350 with gear ratio 3.36 Formula symbols: G Gear step vmax Maximum speed

130 120 110 100 90 80 70 60 50 40 30 20 10 0 1 2

3 4

Speed and axle-drive ratio 6.2

5 6

7

8 9 10 11 11 12 13 14 1 4 15 16 G

  x

 EXAMPLE 

6

Formula symbols: α Climbing capability G Gear step R Slip limit (18 %) Columns: a Axle-dr -drive ratio 3.7 b Axle-dr -drive ratio 3.4 c Theoretical values Note:  This diagram serves serves only as an example for visualisation, i.e. the values do not represent a current vehicle.

α

[%] 50

40

30

20

R

10 a b

0

1 2

c

3 4

5 6

7

8 9 10 11 11 12 13 14 1 4 15 16 G

Climbing capacity and axle-drive ratio

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Formula symbols: FZ  Tractive  Tractive force force M Torque v Speed α Climbing capability at maximum torques Note:  This diagram serves serves only as an example for visualisation, i.e. the values do not represent a current vehicle. Curves: a Torqu orque e cha chara ract cter eris isti tics cs in the the ind indiividual gears b Tract ractiv ive e for force hype hyperb rbol ola a

FZ [kN] 140

M

α

41,7%

a   x

33.9%

120

b 27.6%

100 22.7%

80

19% 15.7%

60

12.5% 10.3%

40

7.9% 6.5%

20

0

FZ

6.3

4.3%

3.5%

2.8% 2.0% 1.5% 0.0%

10 20 30 40 50 60 70 80 90 100 110 120 v [km/h] M

Tractive force hyperbola

5.3%

 BASIC PRINCIPLES PRINCIPLES

6

Drive concept Depending on the arrangement of the engine and drive axles, fundamental distinctions are made between the following drive concepts:  Rear-wheel drive (standard drive)  Front-wheel drive (usually passenger

cars)  Multiple-axle drive   All-wheel drive

 As four or more axles axles are used on commercial vehicles as opposed to passenger cars, there are a large number of drive concepts. These are described by the wheel formulas ( ➜ page 2.2 ). Depending on the drive concept, a number of axles are configured as drive and/or steer axles ( ➜ page 3.3 ).  Almost all modern commercial commercial vehicles vehicles are conceived as cab-over-engine vehicles (➜ page 2.1 ). Underfloor vehicles vehicles are no longer built. Rear engines are used exclusively in buses ( ➜ page 15.14 ).  Alternative drive systems systems such as the nanatural gas engine, hydrogen engine, fuel cell and hybrid drive system (diesel-electric) are described in the chapter entitled "Buses". These have been developed above all for buses in public short-distance passenger transport.

 FUNCTION  Two-axle commercial vehicles  The standard versions versions of two-axle commercial vehicles have a driven rear axle.  These are suitable suitable mainly for road road use. For construction site deployment, twoaxle vehicles are equipped with an additional driven front axle. High driveaway torques and climbing capacity are required and can b e achieved using all-wheel drive. Three-axle commercial vehicles Commercial vehicles with rear-axle drive and a leading or trailing axle ( ➜ page 3.6 ) are used in freight road transport. Commercial vehicles with two driven rear axles or with all-wheel drive, i.e. three driven axles, are suitable for construction site deployment. The latter are regarded as classical off-road and construction site commercial vehicles. Four-axle commercial vehicles Four-axle commercial vehicles are often used above all in the area of construction sites with two driven rear axles and two steered front axles, and with high permitted total weights ( ➜ Fig.).  The four-axle vehicle with all-wheel drive is used for heavy-duty construction site deployment when a high level of off-road mobility is required.

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Heavy construction site vehicle with four axles 6.4

With more than four axles, special drive concepts are applied, usually with special steering systems. These are used in special vehicles.

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 BASIC PRINCIPLES PRINCIPLES

6

Clutch designs In motor vehicle engineering, the clutch is generally defined as a disengageable connection between the engine and drive element. It serves as the driveaway element element in the drive train.

 FUNCTION 

 EXAMPLE 

Friction clutch  The clutch in a commercial commercial vehicles vehicles must perform the following main tasks:

 All of the clutches used used in MAN commercial vehicles have asbestos-free linings and are configured for a clutch service life of more than 600,000 km.

 Speed balancing between drive and

output   Transferring the engine torque

 A fundamental distinction distinction is made between two clutch designs:

 Separating the power flow between

the engine and multi-ratio gearbox

  Adherent clutch

 The large friction surfaces mean that despite low operating forces and small operating paths adequately high torques can be transferred.

 Enabling soft and jolt-free driveaway

 Positive-engaged clutch

 Damping torsional vibrations

 Adherent clutches use use the friction to transfer the torque. They are thus also referred to as friction clutches.

 Protection against component over-

load In conjunction with a standard gearbox, dry single-disc clutches are normally used.

Positive-engaged clutches use the shapes of two clutch elements that fit into one another to transfer the torque.

Due to the high engine torques (at MAN up to 2500 Nm), heavy commercial commercial vehicles require dry double-disc clutches. Compared to single-disc clutches, they can transfer greater torque.

Only adherent clutches are used for the force transmission to drive vehicles.

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LEGEND

1 2 3

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1

2

Force transmission by means of a friction clutch 6.5

3

Engine Clutch Gearbox

 BASIC PRINCIPLES PRINCIPLES

6

 FUNCTION 

Standard clutch for commercial vehicles  The most important components components of a clutch are ( ➜ Fig. page 6.7 ):

Engaged state On both designs, the spring force applies a normal force in the pressure plate and this presses the friction linings of the clutch or driving plate against the flywheel. With the clutch closed, the engine torque is transferred without slip to the multi-ratio gearbox by the clutch disc, which is mounted on the gearbox input shaft in such a way that it cannot turn.

 Flywheel  Clutch or driving plate  Pressure plate  Release lever  Clutch operator   Torsional absorber

 The pressure plate is pressed pressed against the driving plate by 6 to 36 coil springs or a diaphragm spring. Diaphragm springs (disc springs) are more compact than coil springs. They require less disengagement force ( ➜ Fig.) and are also insensitive to high rotational speeds. Diaphragm-spring clutches are the standard clutches used nowadays in commercial vehicles and passenger cars.

Disengaged Disengaged state  The release lever lever presses against against the diaphragm-spring reeds and relieves the pressure plate to the extent that the clutch disc runs freely between the flywheel and pressure plate. In this state, a shift in the gearbox (gear change) is possible without difficulty.

Clutch disc Every combustion engine creates torsional vibrations that spread through the clutch into the gearbox. This leads to rattling noises and increased wear.  To prevent these effects effects or reduce them significantly, clutch discs are equipped with torsional absorbers. Torsional absorbers consist of tangentially arranged coil springs and axially loaded friction rings. In order to achieve soft engagement and prevent harsh driveaway, virtually all clutch discs nowadays are also equipped with lining springs. These axial springs between the clutch linings lead to even force transmission and minimise wear. MAN clutches have pre-absorbers that significantly reduce idling rattle in particular.

On MAN commercial vehicles of the Evolution series, L2000 model, the clutch operator presses against the diaphragmspring reeds; on the heavy M2000 models as well as the TGA model series, it pulls the diaphragm springs and thus releases the clutch disc.  The total of the distances distances between the clutch lining surfaces and the flywheel surface and the pressure plate surface is referred to as the air gap. The tot al air gap should be 0.6 to 1.0 mm.

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LEGEND

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F [N] 225 a

200

175

b

150 0

1

Clutch disengagement force 6.6

2

3

4

5

6

s [mm]

Curves: a Coil-spring cl clutch b Diap Diaphr hra agm-s gm-spr priing clut clutch ch Formula symbols: F Disengagement fo force s Path Path of the the cl clutc utch ope opera rato torr

 FUNCTION 

6 1

2

3

4

5

8

1 2 3 4

Powe Powerr flo flow w (fr (from om engi engine ne to gear gear-box) Flywheel Clutch disc Pressure plate

Dry single-disc clutch

6.7

7

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9

   N    I    A    R    T    E    V    I    R    D

6

5 6 7 8 9

Diaphragm spring Clutch op operator Release lever Axial springs Torsional absorber

 BASIC PRINCIPLES PRINCIPLES

6

 FUNCTION 

Hydrodynamic force transmission On the hydrodynamic clutch, the torque is transferred by means of the hydrodynamic forces of a fluid. A hydrodynamic clutch cannot change the initiated torque; it can only transfer it (output and input torque always remain the same).

Hydrodynamic clutch  The hydrodynamic clutch consists of a housing, a pump gear (primary gear) and a turbine (secondary gear). The vanes of the pump gear are firmly attached to the housing. The fluid used for force transmission is hydraulic fluid ( ➜ page 17.9 ).

 The hydrodynamic hydrodynamic converter converter can vary vary the output moment in relation to the torsion or work as a pure hydrodynamic clutch without torque conversion.

 The pump gear is connected connected to the crankshaft. The turbine is seated on the gearbox input shaft in such a way that it cannot turn. When the pump gear turns, the hydraulic fluid in the chambers of the pump gear is pressed outwards by the centrifugal force and from there into the turbine chambers. The turbine also starts to turn. It conveys kinetic energy to the downstream gearbox.

Hydrodynamic clutches and converters in commercial vehicles bridge the rotational speed difference between the engine and drive train. They are thus very good as driveaway elements. However, to shift gears, the hydrodynamic clutch must have a downstream friction clutch with downstream standard gearbox or automatic gearbox ( ➜ page 6.28 ).

On account of the force transmission using fluid, the hydrodynamic clutch absorbs vibrations and is non-wearing. Hydrodynamic torque converter In contrast to the hydrodynamic clutch, a housing, pump gear and turbine and an additional guidance system (deflection or reaction gear) is used on the hydrodynamic torque converter. Converters used in commercial vehicles vehicles are usually built according to the so-called "Trilok" design. With this design, the guidance system is located between the turbine and pump gear and is equipped with a one-way overrun. The stator deflects the flow of flu-

id from the turbine back to the pump gear.  This deflection increases increases the torque. torque. Depending on the layout of the converter, the stator achieves 1.9 to 2.5 t imes the torque increase on driveaway ( ➜ Fig.). With increasing equalisation of the turbine speed to the pump speed, the rotational speed difference between the pump gear and turbine falls. With the same rotational speed, fluid flows onto the guide vanes of the stator from the rear. The stator also turns; torque conversion is no longer possible. Converter lockup clutch Once the highest rotational speed match has been reached, a converter lockup clutch connects the turbine with the pump gear by means of frictional engagement.  This prevents the slip caused by the fluid on force transmission, which is normally so unfavourable for the efficiency. efficiency.  The converter lockup lockup clutch is usually activated automatically.

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LEGEND

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1 2 3

1

3

Hydrodynamics Hydrodynamics in the torque converter on driveaway  6.8

2

Pump gear Stator Turbine

 FUNCTION 

6

1

2

3

4

5

6

7

8

  x

Converter lockup clutch opened

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6.9

1 2 3 4 5 6 7 8

Flow Flow of forc force e (fr (from om engi engine ne to gear gearbo box) x) Drive Turbine Stator Pump gear Overrun Output Conv onverte erterr loc lockup kup clu clutc tch h

Force characteristics in the hydrodynamic converter with lockup clutch

Converter lockup clutch closed

6

 BASIC PRINCIPLES PRINCIPLES

 FUNCTION 

Special forms of clutch  The wide range of tasks tasks to be performed by clutches leads to special forms of disengageable connections in the drive train that are exactly geared to the tasks.

Dog clutch  A dog clutch clutch is a positive-engaged positive-engaged clutch clutch that is used on commercial vehicles for manual shifting of longitudinal and transverse differential locks as well as for engageable all-wheel drive ( ➜ Fig.).

Positive-engaged clutch

 A dog clutch can only only be shifted when when the vehicle is at a standstill.

 Dog clutch

 Adherent clutches  Multi-disc clutch  Centrifugal clutch  Dual clutch

with lockup clutch   Torque converter with

Dual clutch In the dual clutch, two clutches are grouped into one unit. One clutch serves to transfer the engine torque to the multi-ratio gearbox; the second clutch transfers the engine torque, for example, to a power take-off ( ➜ page 6.29 ).

Multi-disc clutch Multi-disc clutches have a number of discs. Depending on the area of application, the discs run in an oil bath or dry. Multi-disc clutches require less space, as the large number of friction pairings means that they can transfer relatively high torques despite their small dimensions. When engaged, intermediate discs located between the discs are connected adherently by spring force. Multi-disc clutches are used most frequently for motorcycles, automatic gearboxes and automatic differential locks ( ➜ page 6.34 ). Centrifugal clutch  A centrifugal clutch clutch consists of a clutch clutch drum connected to the gearbox and the engine. Articulated clutch elements are pressed against the clutch drum, by an increasing centrifugal force, as the engine speed rises, thus enabling the transfer of the engine torque.

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LEGEND 1 2

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3 4

4

Dog clutch in a differential lock  6.10

1 2

3

Clutch dogs Gear Gearsh shif iftt slee sleeve ve of of the the diff differ eren enti tial al lock (can be shifted on the axle shaft toothing) Pneu Pneuma mati tic c gear gearsh shif iftt ele eleme ment nt Control fork  

 FUNCTION 

6

 EXAMPLE 

Converter shift clutch WSK   The converter shift shift clutch WSK is a system combination especially developed for heavy-duty operation consisting of a hydraulic torque converter and a dry clutch. Essentially, a converter shift clutch consists of the following components ( ➜ Fig.):  Hydrodynamic torque converter with

overrun  Lockup clutch (bridges the converter

at high engine speed)  Overrun one-way clutch (bridges the

converter in the overrun condition)  Retarder (optional boosting of the bra-

king torque in the overrun condition)  Shift clutch

 To shift the gears, the shift shift clutch interrupts the power flow. After the gear step has been engaged, the torque converter ensures a smooth build-up of the torque transfer.

If the drive and output speeds approach one another up to a certain speed gap, the lockup clutch bridges the converter and thus achieves a rigid drive-through.  The overrun one-way one-way clutch bridges bridges the converter in the overrun condition, which means that the engine braking torque can be exploited. As an option, the converter shift clutch is given a retarder to boost the braking torque in the overrun condition ( ➜ Fig.).  The converter converter shift shift clutch clutch permits jolt-free driveaway and manoeuvering with centimetre precision, even under difficult circumstances. The driveaway and shifting operations are virtually wear-free, even with high road-train weights, as the shift clutch (dry clutch) can close without frictional slip. The converter completely assumes the necessary conversion of the torque.

On driveaway, the shift clutch opens while the first gear is being engaged. On closing the clutch, there is no need to press the accelerator, as the converter only transfers very low torque on idling. Only when the shift clutch has closed is the engine speed increased by pressing the accelerator. In this phase, t he converter ensures a peak in the output torque up to 2.5 times the input torque.

MAN TipMatic gearshift system with WSK   An innovation is the use of the converter shift clutch on the MAN TipMatic gearshift system (➜ page 6.24 ). A converter shift shift clutch (instead of the electropneumatically operated, mechanical clutch) in combination with an automatic standard gearbox enables easy driveaway operations. This includes automatic gearshifts; the clutch pedal can be eliminated.  The MAN TipMatic gearshift gearshift system with the converter shift clutch WSK 440 has been specially developed by MAN for transporting heavy loads. It was fitted for the first time on the four-axle heavy-duty semitrailer tractors of the Trucknology Generation (TGA). Here, the converter shift clutch means that the huge torque of the  V10 engine can be used for driveaway and manoeuvering virtually without clutch wear. From a technical point of view, this powerful drive train permits total roadtrain weights of up to 250 t.

  x

LEGEND

1

3

4

4

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B 5

1

8 3

7

B

1

8 6

C

6

7

8

Converter shift clutch (WSK 440) 6.11

 A

7

 A 

1

2

7

5

Power flow schema in the WSK 440

8

C

1 2 3 4 5 6 7 8

Driveaway or manoeuvering in the converter range Driv Drivin ing g with with clo close sed d conv conver erte terr lock lockup up clutch Over Overru run n ope opera rati tion on (brak (brakin ing g with with engine via overrun one-way clutch and with retarder) Drive from engine One-way cl clutch Con Conver verter ter loc lockup kup cl clutc utch Hydr Hydrod odyn ynam amic ic tor torque que con conve vert rter er Con Conver verter ter one one-w -wa ay cl clutc utch Retarder Shift clutch Output to gearbox

 BASIC PRINCIPLES PRINCIPLES

6

 FUNCTION 

Clutch control via pedal  Two types of clutch control control are distinguished:  Mechanical clutch control  Hydraulic clutch control

 The cable pull versions versions of mechanical mechanical clutch control is used nowadays almost exclusively on passenger cars. Hydraulic clutch control is self-adjusting and is standard equipment for commercial vehicles and upper class passenger cars on account of the high effective forces . On commercial vehicles with high power output, clutches with strong diaphragm springs are necessary to ensure adherent connection in all situations. To reduce the operating forces, clutch boosters (servo clutches) are used.

Hydraulic clutch control When the clutch pedal is operated, the piston movement builds up pressure in the master cylinder; this is routed through the hydraulic line to the slave cylinder, where it is converted back into a longitudinal movement. The master and slave cylinders are connected to one another via pipe and hose lines ( ➜ Fig.).

cylinder. The pedal forces are reduced to one fifth.  The clutch booster provides provides relief for the driver on conventional clutches, as lower pedal forces and paths are required. If the compressed air fails, the clutch remains operable but with greater pedal forces.

 The enhancement enhancement of hydraulic hydraulic clutch control has led to the clutch operator with integrated slave cylinder. Here, the clutch operator and slave cylinder form a unit that encloses the gearbox input shaft, whereby a release fork is not required. For operation of the diaphragm-spring clutch, a distinction is made between clutches that are operated by "pulling" or "pushing" (➜ page 6.6 ). Due to the more favourable lever relationships, the efficiency is better with a pulled clutch. The clutches used in heavy commercial vehicles have pulled clutch control.  The routing of hydraulic hydraulic lines can be protected in the vehicle and they permit long transfer paths without difficulty, e.g. on buses with rear engines.    l   a    d   e   p

Clutch booster  The clutch clutch booster is a hydraulic slave cylinder combined with a compressed air

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  n   o   h   c   c    h   t   u   c   l    t   u   C    l    1  .    C   5    5  .  .    4    4  .  .    6   6   x

LEGEND

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1

3

4

2

Hydraulic clutch control with pedal  6.12

1 2 3 4

Clutch Slave cylinder Master cy cylinder Clutch pedal

 BASIC PRINCIPLES PRINCIPLES

6

 FUNCTION 

Electropneumatic clutch control  The use of compressed air air cylinders for clutch boosting or clutch control forms the technical basis for electronic clutch control on commercial vehicles. Depending on the gearbox version, MAN offers the following systems for electropneumatic clutch control:

MAN ComfortShift On the MAN ComfortShift gearshift system with ZF-Ecosplit gearbox ( ➜ page 6.23 ), there is an optional button on the gearshift lever for clutch control in addition to the conventional hydraulic actuation with compressed-air support controlled via the clutch pedal.

 MAN ComfortShift with button on the

When the button is pressed, the vehicle management computer synchronises the engine and gearbox rotational speeds on shifting gear steps. Only then is the clutch closed. The driving pedal can remain in an unchanged position during this operation.

gearshift lever (alternative to clutch pedal)  MAN TipMatic fully automatic (without

clutch pedal)  The electronic electronic lining wear monitor with auautomatic clutch readjustment is of decisive significance for exact functioning of the electropneumatic clutch control. A travel sensor monitors the disengagement travel of the clutch and transfers the measured value via the vehicle management computer to the central on-board computer, which then determines the wear. If the lining thickness reaches 10 % of its original value, a warning is displayed in the driver display.

MAN TipMatic On the MAN TipMatic gearshift system with automatic ZF gearbox ( ➜ page 6.24 ), all of the clutching operations required for shifting gears are automated. The electropneumatically operated clutch – the clutch pedal is eliminated – completely frees the driver of clutch control.  The MAN TipMatic control control unit processes all the influencing variables and transfers the corresponding signals to the shift module and to various solenoid valves for pneumatic clutch control.

actuation travel is redefined accordingly for the clutching operation. Electronic clutch protection Frequent excessive engine speeds lead to wear on clutches of up to 95 % on driveaway and manoeuvering. On gearshifts, however, the clutch is subjected to less stress. The electronic clutch protection on MAN commercial vehicles reduces the lining wear and increases the clutch service life by means of the following functions:  Limitation of the driveaway engine

speed to 1400 rpm with the clutch protection function of MAN ComfortShift  Lower clutch wear by means of

engine management and optimised clutch control via vehicle management computer on MAN ComfortShift  Comfortable driveaway by means of

sensitive clutch control and the highest economy on MAN TipMatic by means of computerised influence on various variables on the clutching operation  Forced closure of the clutch if there is

danger of overheating (MAN TipMatic)

 The travel sensor sensor integrated in the clutch clutch actuator monitors the disengagement travel. The lining wear is re-established for each clutch engagement operation. The

   l   o   r    t   n   o   c    h   c    t   u    l   c   c    i    t   a   m   u   e   n   p   o   r    t   c   e    l    E    2  .    5  .    4  .    6   x

LEGEND

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1 2 3 4

   N    I    A    R    T    E    V    I    R    D 4

3

2

Clutch actuator on the MAN TipMatic gearbox  6.13

Shift module Clut Clutch ch actu actuat ator or with with trav travel el sens sensor or Release fork   Sing Single le-d -dis isc c fric fricti tion on clut clutch ch

 BASIC PRINCIPLES PRINCIPLES

6

 FUNCTION 

Types of gearbox  A gearbox serves to transfer, route, distribute and convert torques and rotational speeds. A gearbox can thus also be referred to as a torque or rotational speed converter. The relationship between the input and output rotational speed is referred to as the gear ratio or reduction ratio ( ➜ page 1.11 ).  A gearbox on which a number number of gear ratios can be engaged and disengaged is referred to as a multi-ratio gearbox ( ➜ page 6.15 ). These are usually gear-driven.  This applies both to automatic automatic and manumanual gearboxes.  The a wide variety variety of requirements in vevehicle construction for gearboxes has led to the development of a large number of variants.  The force transmission transmission on gearbox in gear-driven and chain-driven gearboxes is positive-engaged; in belt-wrap gearboxes it is adherent. Belt-wrap gearboxes are used as continuously variable gearboxes on vehicles with low power output.

Spur gears Spur gears are used above all in standard gearboxes. The torque transfer is via spur gears. The axles of driven and driving wheels are parallel ( ➜ Fig.).

Either rubber belts reinforced with Kevlar or link chains are used.

Bevel gears Bevel gears are used as axle drives ( ➜ page 6.32 ). Besides the gear gear ratio, they also enable deflection of the transferred torque by 90°. The axles of the gear wheels are arranged crosswise (intersecting ➜ Fig.). Worm gears Worm gears are used as axle drives in special vehicles, but also e.g. for the drives of windscreen wipers or as steering gears. With worm gears, the axles are also arranged crosswise ( ➜ Fig.). Planetary gear set Planetary gear sets ( ➜ page 6.26 ) are used on planetary drive axles, range-shift gearboxes, as rear-mounted groups and in automatic gearboxes. Chain drives Chain drives are used above all as the primary drive system on motorcycles. Belt-wrap gearboxes Belt-wrap (or chain-wrap) gearboxes are intended for use as continuously variable gearboxes and they only differ with regard to the structure and material of the belt.

  x   o    b   r   e   a   w   e    i  r  v   e   v    G   O    5  .    1 . .    6   x    6   5

LEGEND

1 2 3

1

   N    I    A    R    T    E    V    I    R    D

2

Types of gearbox  6.14

3

Spur gears Bevel gears Worm gears

 BASIC PRINCIPLES PRINCIPLES

6

 FUNCTION 

Multi-ratio gearbox  A multi-ratio gearbox enables enables the setting of a number of different gear ratios and thus the torque and rotational speed conversion:  Converting and transferring the engine

torque to provide the required tractive force  Stepping up the engine speed to

achieve different speeds  Interrupting the power flow when the

vehicle is stationary  Reversing the direction of rotation for

reversing

Shift dog gearboxes are used above all in motorcycles. Gearshift sleeve synchromesh gearboxes are the gearboxes currently used in passenger cars and commercial vehicles. In commercial vehicles, they are frequently used with front-mounted groups ( ➜ page 6.20 ) as range-change gearboxes. gearboxes. Nowadays, sliding-gear countershaft gearboxes are no longer used in motor vehicles. However, the simple structure clearly illustrates the power flow as well as the general function of multi-ratio gearbox and will be used as an example here.

 To shift gears, the two connecting connecting gearbox elements (gear wheels) must be brought to the same rotational speed.  This operation is referred referred to as synchronisynchronisation (➜ page 6.18 ).

Sliding-gear countershaft gearbox Sliding-gear countershaft gearboxes have a main shaft and a countershaft. The sliding gears are seated on the main shaft.  They can be shifted shifted with the help of gearshift rods and control forks. Depending on the engagement, different rotational speeds and moments affect the output shaft (➜ Fig.):  1st gear: the gearwheel pair z 1.2 and

z5.6 boosts the input torque and reduces the input rotational speed.  2nd gear: the gearwheel pairs z 1.2 and

z3,. also boost the to rque and reduce the rotational speed.  3rd gear: gear wheel z 3 shifts like a

sleeve over the smaller interlacing on gear wheel z 1. In this way, the lefthand and right-hand section of the main shaft are adherently connected.  There is no torque and and rotational speed conversion (direct gear).

Designs of multi-ratio gearboxes  The following designs of multi-ratio gearboxes are distinguished:

 Reverse gear: gearwheel pair z 1.2

engages. The reverse gear wheel z R reverses the direction of rotation once again between the gear wheels z 7 and z8. The torque is boosted, the rotational speed is reduced.

 Sliding-gear countershaft gearbox  Shift dog gearbox  Gearshift-sleeve Gearshift-sleeve or gearshift sleeve

synchromesh gearbox (coaxial and deaxial ➜ page 6.16 ),

  x   o    b   r   a   e   g   s   o   n    i    t   g   a   i   r   -   s    i    t   e    l    D   u   1  .    M    2  .  .    2    5  .  .    5    6   6   x

 Front-mounted and rear-mounted

range-change gearbox ( ➜ page 6.20 ).

LEGEND

1

   N    I    A    R    T    E    V    I    R    D

z1

z5

 A

3 z1

 A B C D 1 2 3

z3

B

z6

z2 z1 C

2

z2 z3

z4 z8

z1 D zR z7 z2

Gear steps on the three-speed sliding-gear countershaft gearbox  6.15

1st gear 2nd gear 3rd gear Reverse gear Slid Slidin ing g gea gears rs with with cont contrrol fork forks s Main shaft Countershaft

 FUNCTION 

6

 EXAMPLE 

Gearshift sleeve gearbox Gearshift sleeve gearboxes are equipped with a main shaft, a countershaft, a reverse shaft with reverse gear wheel and a gearwheel pair per driving position.  All gearwheel pairs pairs of the forward gears gears are continuously engaged. The gear wheels of the main shaft rotate freely. The gear wheels of the countershaft are firmly attached to it ( ➜ Fig. page 6.17 ).

Deaxial gearbox In deaxial gearboxes, the torsion is routed via an externally toothed gearwheel pair for each driving position from the drive shaft to a parallel output shaft. The drive and output shafts are not aligned.

Toothing of multi-ratio gearboxes Depending on the type, different toothings are used. In the case of unsynchronised multi-ratio gearboxes, e.g. the EATONFuller gearbox, straight-toothed spur gears are normally used, which means that no axial forces take effect in the gearbox.  The disadvantage of straight-toothed straight-toothed (spur-cut) gearboxes, however, is the high level of noise development, which is clearly noticeable when driving fast in reverse with modern synchromesh gearboxes (the reverse gear is usually straight-toothed).

 The gearshift sleeves sleeves are mounted in keykeyways on the main shaft and can b e shifted axially on the shaft. Shifting the gearshift sleeves attaches the corresponding gear to the main shaft in such a way that it cannot turn; the desired gear ratio is created.

For this reason, helical-toothed gearwheel pairs are normally used on modern synchronised gearboxes. The engagement length of the teeth is greater. A number of teeth are always engaged. With the same width, helical-toothed gear wheels can thus transfer higher torques compared to straight-toothed gear wheels.

Distinctions are made between:  Coaxial gearboxes  Deaxial gearboxes

Coaxial gearbox In coaxial gearboxes, the torque is transferred via two externally toothed spur gear pairs on two parallel shafts (except for the direct gear). The drive and output shafts are aligned.

  x   o    b   r   a   e   g   e   v   e   e    l   s    t    f    i    h   s   r   a   e    G    2  .    2  .    5  .    6   x

LEGEND

1

2

   N    I    A    R    T    E    V    I    R    D

2 3

3

Coaxial synchronised gearshift sleeve gearbox made by EATON  6.16

1

Driv Drive e shaf shaftt (fr (fron ontt sec secti tion on of main main shaft) Outp Output ut sha shaft ft (re (rear ar sect sectio ion n of of the the main shaft) Countershaft

 FUNCTION 

6

1

2

3

4

5

6

  x   o    b   r   a   e   g   e   v   e   e    l   s    t    f    i    h   s   r   a   e    G  x

8

   N    I    A    R    T    E    V    I    R    D

6.17

1 2 3 4 5

Driv Drive e sha shaft ft (fro (from m eng engin ine e via via clut clutch ch)) = main shaft (split into item 1 and 6) Countershaft Roller Roller bearin bearings gs betwe between en drive drive and output output shaft shaft Slid Slidin ing g sle sleev eve e on on syn synch chro roni nise serr bod bodyy Gear Gearsh shif iftt rail rail with with cont contro roll fork forks s

Coaxial synchronised gearshift sleeve gearbox made by ZF 

6 7 8

7

Outp Output ut shaf shaftt (to (to axl axle e or or tra trans nsfe ferr cas case) e) = Main shaft (split into item 1 and 6) Stra Straig ight ht-t -too ooth thed ed spur spur gear gears s (first gear and reverse gear) Heli Helica call-to toot othe hed d spur spur gear gears s

 BASIC PRINCIPLES PRINCIPLES

6

 FUNCTION 

Gearbox with synchromesh mechanism In order to be able to shift gear on an unsynchronised gearshift sleeve gearbox, the gearshift sleeve and gear must rotate at the same speed (only then is it possible for the toothing of the corresponding spur gears to engage). Without a synchromesh mechanism, this is only possible with "double-clutching" for upward shifts and "double-declutching" for downward shifts. In synchronised gearboxes, the gearshift sleeve and gear are synchronised by friction. They enable:  Fast, silent and low-wear shifts in dri-

ving position  Balancing of the speed difference bet-

ween gearshift sleeve and gear  Locking of the gearshift sleeve in the

Synchromesh mechanism  All one-sided synchromesh synchromesh mechanisms mechanisms are based on the same principle of friction.  They only differ differ with regards to the form form and actuation of the locking element.  Alongside the common systems systems for commercial vehicles made by ZF and EATON, systems such as "Borg-Warner" and "Porsche" are used above all in passenger cars. Locking synchronisation system "ZF"  Also on the synchronised synchronised gearbox, the gear wheels of the countershaft and main shaft are continuously engaged. The gearshift sleeve is fixed in the circumferential direction and connected longitudinally with the main shaft in such a way that it can be shifted. This means it always has the same rotational speed as the main shaft (➜ Fig. page 6.17 ).

against the toothed synchroniser ring (item 2). This presses it against the friction cone of the clutch body (item 1).  The friction and the existing rotational speed difference mean that the synchroniser ring runs a rotational movement that is limited by the synchroniser body (item 6). The result of this is that the helical tooth end face of the synchroniser ring press against the sliding sleeve. Only when the conical friction faces have set up the synchronisation does the persistent pressure of the sliding sleeve lead to the synchroniser ring being turned back. This releases the lock and the sleeve can be inserted in the toothing of the clutch body.

Each gearshift sleeve is fitted with a synchroniser ring ( ➜ Fig., item 2). The gear wheels (items 4+8) have a conical friction surface.

event of unmatched rotational speeds However, synchromesh mechanisms will disappear in future to an increasing extent, above all for cost reasons, and will be replaced by more intelligent control systems and better engine management (automated standard gearbox ➜ page 6.24 ).

For each gearshift operation, the corresponding sliding sleeve must be prevented from engaging in the toothing of the clutch body until the existing rotational speed difference has been balanced out.   m   s    i   n   a    h   c   e   m    h   s   e   m   o   r    h   c   n   y    S    3  .    2  .    5  .    6   x

On the ZF-BK synchromesh mechanism, an axial movement of the sliding sleeve (item 3) presses the pressure pin (item 7)

LEGEND

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1

8

7

 ZF-BK synchromesh synchromesh mechanism 6.18

6

5

4

2

3

1 2 3 4 5 6 7 8

Clutch body Synchroniser ri ring Sliding sleeve Idler ge gear "gear y" Main shaft Synchroniser bo body Pres Pressu sure re pin pin wit with h pres pressu sure re spri spring ng Idler ge gear "g "gear x"

 FUNCTION 

1 2

6

3 1

2

3

Neutral position (legend ➜ page 6.18)

8

7

6

5

4

Synchronising

  m   s    i   n   a    h   c   e   m    h   s   e   m   o   r    h   c   n   y    S   x

   N    I    A    R    T    E    V    I    R    D

Shifting gears

Sequence of synchronisation

6.19

 FUNCTION 

6

Gearbox: ZF 16 S 222 Ecosplit  A Main gearbox 4-speed (3 gearwheel pair and direct drive-through) and reverse gear B Frontont-m moun ounted ted grou group p (splitter unit) Step I: slow Step II: fast C Rea Rear-mo -mounte unted d grou group p (range shift) (planetary gear set on/off) Components ➜ page 6.17 Power flow example: 3rd gear, slow B

1st gear, slow 1st gear, fast 2nd gear, slow 2nd gear, fast 3rd gear, slow 3rd gear, fast 4th gear, slow 4th gear, fast 5th gear, slow 5th gear, fast

   N    I    A    R    T    E    V    I    R    D

6th gear, slow 6th gear, fast 7th gear, slow 7th gear, fast 8th gear, slow 8th gear, fast Reverse gear, slow Reverse gear, fast

 A

B

1

I

1

II

2

I

2

II

3

I

3

II

4

I

4

II

5

I

5

II

6

I

6

II

7

I

7

II

8

I

8

II

R

I

R

II

Power flow in the 16-speed range-change gearbox (DD gearbox) gearbox)

6.21

A

C

  x   o    b   r   a   e   g   e   g   n   a    h   c     e   g   n   a    R  x

 BASIC PRINCIPLES PRINCIPLES

6

 FUNCTION 

Gearshift mechanism  After the introduction of power power steering and power clutch, the gearshift mechanism is regarded as the vehicle-driver interface with the greatest physical load. Purely mechanical shifting of non-synchronised gearboxes is no longer stateof-the-art with regard to today's requirements in the areas of ergonomics, safety and economy. Nowadays, in order to make the gearshift operation as fast and for the driver as comfortable as possible, pneumatic, hydraulic and electrical components or combinations are used. Current solutions are electropneumatic or hydrostatic gearshift mechanisms and even electronically controlled automated standard gearboxes ( ➜ page 6.24 ).  Above all due to the high costs, so-called converter powershift gearboxes (automatic gearboxes ➜ page 6.28 ), where where gegearshifts are completely eliminated, play a subordinate role in the field of commercial vehicles with exception of buses, municipal vehicles and in the area heavy-load transport.

Pneumatic gearshift power support Gears on multi-ratio gearboxes are shifted using the gearshift lever; this is connected to the gearbox by a mechanical transmission unit. In the gearbox, the corresponding gearshift sleeve is moved via gearshift rods and control forks. In the case of range-change gearboxes (➜ page 6.20 ), the front-mounted and rear-mounted group are usually controlled pneumatically. In the case of the ZF Ecosplit gearbox ( ➜ Fig.), a switching valve is controlled by the turning shaft of the four-speed section; it only releases the compressed air to a dual-action shift cylinder in the neutral position (➜ page 6.23 ).

veloped by Mercedes-Benz, there is no mechanical connection between the gearshift lever and the gearshift rods in the gearbox.  The gearshift gearshift lever is mounted on a pulsepulsegenerator device that sends pulses to t he electronics. Following a switch pulse, compressed air controlled by solenoid valves flows into the corresponding gear or group cylinder. The pistons move out and in turn move the gearshift rods with the corresponding control forks. The corresponding gears are shifted in the same way as on a conventional gearbox.

 The integrated, front-mounted splitter unit is also operated pneumatically by means of a pilot valve fitted on the gearshift lever.  The pilot valve is is used to preselect each each splitter unit I or II ( ➜ Fig. page 6.20 ) via a relay valve.  The clutch pedal is is fitted with a release release valve. The release valve only releases the compressed air to the shift cylinder when the clutch has completely disengaged; the splitter unit is switched over according to the preselection. EPS gearshift EPS stands for electropneumatic standard gearbox. On this gearbox control de-

  m   s    i   n   a    h   c   e   m    t    f    i    h   s   r   a   e    G    5  .    2  .    5  .    6   x

LEGEND

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   N    I    A    R    T    E    V    I    R    D

2 3

3 2

ServoShift  6.22

1

Hydr Hydrau aulilic c sla slave ve cyli cylind nder er for for shi shift ft gut gut-ter Hydr Hydrau aulilic c slav slave e cyli cylind nder er for for gea gearr position Pneu Pneuma mati tic c cyl cylin inde derr, gear gearsh shif iftt powe powerr support ServoShift

6

 FUNCTION 

 EXAMPLE 

Hydrostatic gearshift mechanism  The hydrostatic gearshift gearshift mechanism (HGS) MAN ServoShift is offered for all manual gearboxes of the Trucknology Generation. In the case of MAN ServoShift, force transmission from the gearshift lever to the gearbox is via hydraulic lines with a heated master cylinder at the gearshift lever and slave cylinder at the gearbox. The gearshift linkage is eliminated ( ➜ Fig.).

Gearshift mechanism with single-H  The hydrostatic gearshift gearshift mechanism MAN ServoShift also simplifies the gearshift operation. The 16 gears are shifted by means of a splitter unit and a range shift with only two shift gutters (single-H gearshift pattern). The shifting travels of the large and small range shift are overlaid (➜ Fig. page 6.20 ).

 This hydrostatic gearshift gearshift mechanism is additionally combined with pneumatic gearshift power support. The pneumatic gearshift power support ServoShift consists of a mechanical-pneumatic and dual-action compressed air cylinder. This is series standard equipment for all mechanical gearboxes.  The hydrostatic gearshift gearshift mechanism MAN ServoShift means an increase in comfort for the driver, as impacts and vibrations are no longer transferred from the drive train to the gearshift lever. There is also lower noise development in the driver's cab.

by the vehicle management computer aligning the speed and rotational speed. In conjunction with MAN ComfortShift, HGS provides a completely new gearshift experience with comfort similar to that in a passenger car .

Shifting from 4th gear to 1st gear within a group is prevented by a gutter lock. Furthermore, the vehicle management computer prevents incorrect gearshifts to the wrong range shift. MAN ComfortShift With the MAN ComfortShift gearshift system, switching operations can be run without using the clutch pedal and without changing the driving pedal position. Both the split operations and gear changes can be run in this way.  Activated by a button on the left-hand side of the gearshift knob, the driving clutch is operated electropneumatically during the gearshift operation ( ➜ Fig.). The button must remain pressed during the gearshift operation with ComfortShift.  The engine speed is automatically adapadapted via the vehicle management computer. The driving pedal can remain in an unchanged position during this operation.  The vehicle is is prevented from "jumping" "jumping"

  m   s    i   n   a    h   c   e   m    t    f    i    h   s   r   a   e    G  x

LEGEND

1

3

   N    I    A    R    T    E    V    I    R    D

2 2 1

1

4 5

4

6 10

9

6.23

3

Pneumatic gearshift power support 'ServoShift'

2

5 7

3

6 7 8 9 10

8

MAN ComfortShift 

Rock Rocker er swit switch ch for for shi shift ftin ing g the the grou group p (rear-mounted group) Slid Slidin ing g swi switc tch h for for shif shifti ting ng the the spl split it gears Butt Button on for for dis disen enga gagi ging ng the the clu clutc tch h (ComfortShift) Hydr Hydrau aulilic c mast master er cyli cylind nder er (hea (heate ted) d) Hydr Hydrau aulilic c sla slave ve cyli cylind nder er for for shi shift ft gut gut-ter Gearshift rod Control fork   Hydr Hydrau aulilic c slav slave e cyli cylind nder er for for gea gearr position Pneu Pneuma mati tic c cyli cylind nder er of of gear gearsh shif iftt power support ServoShift Gears Gearshif hiftt lever lever, turningturning-sha shaft ft shiftin shifting g

6

 BASIC PRINCIPLES PRINCIPLES

 FUNCTION 

 Automated standard standard gearbox gearbox Modern gearshift systems, e.g. MAN TipMatic, enable gear changes with one touch of the steering-column switch without the driver operating the clutch or taking his or her foot from the accelerator. On request, they are even fully automatic. MAN TipMatic works with an automated standard gearbox on which all of the operations required for shifting gears are automated.

MAN TipMatic gearshift system  The MAN TipMatic gearshift system combines an electropneumatic manually or automatically engaging and disengaging gearbox with an automated mechanical mechanical clutch. The electropneumatic clutch control (without clutch pedal) fully relieves the driver of the task of clutch control.

In conjunction with engine control EDC and the MAN BrakeMatic for brake control, the MAN TipMatic gearshift system is integrated via the CAN bus in t he MAN  Tronic. According to the wish of the driver (accelerator or brake pedal), the vehicle management computer (FFR) combines with the central on-board computer (ZBR) to provide the control units involved with the corresponding target values and handles all the required control functions (➜ page 11.8 ). Other automated gearshift systems that work in a similar manner are e.g. Telligent EAS (Mercedes), Opticruise (Scania), Geartronic (Volvo), EuroTronic (Iveco) or the Opti-Driver system from Renault.

 The automated standard standard gearbox used (ZF AS-Tronic ➜ Fig.) has 12 or 16 gears and is used without a synchromesh mechanism in the four-speed section; the splitter unit and range shift are synchronised. Despite the automated switching operations, both manual and automatic gear selection is possible depending on what the driver wants. With manual operation, the driver selects the gear step using a steering-column switch. The driveaway situation is preselected using a rotary switch in the centre console beside the driver's seat. In the automatic mode, the driver only operates the accelerator or brake pedal. Selection and execution of the shifting operations are handled by the MAN TipMatic system quickly and smoothly.

In the manoeuvering positions DM and RM, upward gearshifts are prevented. The FFR also only provides reduced torque and thus prevents the vehicle from "jumping". Steering-column switch In manual operation, the gear step is selected using the steering-column switch.  After every operation, the steering-column switch moves back on a spring to its initial position. A button can be used to switch between manual and automatic operation. Displays in the driver display  During manual operation, the engaged gear is displayed. Arrows in front of the display pointing upwards and behind the display pointing downwards show the possibilities for upward and d ownward gearshifts. During automatic operation, the message "AUTO" and the engaged gear are displayed.

Rotary switch On the MAN TipMatic, the driver uses the rotary switch to select the gear step before moving off depending on the load ( ➜ Fig. page 6.25, 6.25, items D1 ... D5).

  x   o    b   r   a   e   g    d   r   a    d   n   a    t   s    d   e    t   a   m   o    t   u    A    6  .    2  .    5  .    6   x

LEGEND

1 2 3

1

   N    I    A    R    T    E    V    I    R    D

3

 Automated standard standard gearbox gearbox ZF AS-Tronic AS-Tronic 6.24

2

Gearshift module Base gearbox Elec Electr trop opne neum umat atic ic clut clutch ch actu actuat ator or

 EXAMPLE 

6

Function schema ZF 12 AS-Tronic 2601 Components:  A 3-speed main gearbox (2 gears via gearwheel pairs as well as 1 gear as direct drive) and reverse gear (R) B Fron Frontt-mo moun unte ted d grou group p (spl (split itte terr uni unit) t) Step I: slow Step II: fast C Rear Rear-m -mou ount nted ed grou group p (ra (rang nge e shi shift) ft) Planetary gear set on/off  Power flow: K1 Power Power output output split via front-mou front-mounted nted group group (Step (Step I or II) on both countershafts (in the direct gear, gear, drive-through without power output split) K2 Return Return of the power output split in the the 3-spee 3-speed d section to the main shaft in the corresponding gear K3 Output Output via the rear rear-moun -mounted ted group group (planetary (planetary gear set on) in the lower driving positions 1–6 and R (gears 1–3 and reverse gear each via slow and fast splitter unit) K4 Output Output directl directlyy to props propshaft haft (planetar (planetaryy gear gear set off) in the upper driving positions 7–12 (gears 1–3 each via slow and fast splitter unit)

B I II 3 3

2

2 1

1 R

C

R

 A  K1

K2

K3

K4

Rotary switch in the centre console DM Manoeuve Manoeuvering ring forwards forwards in in slowly slowly D1 Driving Driving forwards forwards with driveaway driveaway gear 1 D3 Driving Driving forwards forwards with driveaway driveaway gear 3 D5 Driving Driving forwards forwards with driveaway driveaway gear 5 N Neutra Neutrall (gear (gearbox box in neutra neutrall posit position ion,, drivi driving ng switch without function) R Reversing RM Manoe Manoeuve uverin ring g backwar backwards ds

   N    I    A    R    T    E    V    I    R    D

Steering-column switch + Shiftin ting up up on one step (lever upwards towards driver) ++ Shif Shifti ting ng up up seve severa rall steps steps (multiple touch) – Shifting do down on one ste step p (lever downwards way from driver) – – Shifti Shifting ng down down severa severall steps steps (multiple touch)

MAN TipMatic gearshift system

6.25

  x   o    b   r   a   e   g    d   r   a    d   n   a    t   s    d   e    t   a   m   o    t   u    A  x

+

+ + _  _ 

_ 

 BASIC PRINCIPLES PRINCIPLES

6

 FUNCTION 

Planetary gear set Planetary gearboxes consist of intermeshed gear wheels. The individual gear wheels or gear wheel groups each have a shaft.

Gear wheels of the planetary gearbox  All gear wheels are continuously engaged; the sun gear, internal gear and planet carrier can be driven or also fixed. They can be used either as drive or output.

 A single planetary gear gear set consists of:

 The various various gear ratios can can be created by fixing and/or connecting or separating the sun gear, internal gear or planet carrier.  They are connected connected or separated by mulmulti-disc clutches or gearshift sleeves and fixed by brake couplings or brake bands.

 Sun gear with carrier and shaft  Internal gear with carrier and shaft  Planet gears with carrier and shaft

Normally, three planet gears mounted on a planet carrier are used. They revolve around the centrally mounted sun gear; an internally toothed internal gear revolves around the planet gears. The shafts for the planet carrier and for the internal gear are hollow shafts ( ➜ Fig.). Planetary gearboxes are used in the following areas:  in automatic gearboxes ( ➜ page

6.28 ),  as rear-mounted groups on range-

change gearboxes ( ➜ page 6.20 ),  in transfer cases ( ➜ page 6.35 ),  in planetary drive axles ( ➜ page 3.4 ).

With the internal gear fixed, sun gear driven and output on the planet carrier, there is a step down towards slow. This corresponds to the 1st gear of a three-speed gearbox ( ➜ Fig. page 6.27 ). In the case case of a planetary gear set used as a rear-mounted group (➜ page 6.20 ), this position is referred to as the 'slow group'. group'. With the sun gear fixed, the internal gear driven and output at the planet carrier, there is a smaller step down towards slow (2nd gear).

site direction to that of the sun gear ( reverse gear   ). Single planetary gear sets are adequate for use in rear-mounted groups of rangechange gearboxes or in axle drives. For use in automatic gearboxes, a number of planetary gear sets are placed in succession or two planetary gear sets are coupled with shared components. A distinction is made between two designs: Ravigneaux gearbox With this design, two single planetary gear sets are coupled to a shared internal gear.  Three to five short and and three to five long planet gears connect the two sun gears.  The output is via the internal internal gear or the planet carrier. Simpson gearbox  The Simpson gearbox consists of two single planetary gear sets that have a shared sun gear. The output is via one of the two internal gears.

 A blocked blocked planetary planetary gear set results results in the direct gear ratio of 1:1. All three components rotate in the same direction with the same rotational speed (3rd gear). This gear shift on a rear-mounted group corresponds to the 'fast group'. group' . With a fixed planet carrier and driving sun gear, the internal gear rotates in the oppo-

   t   e   s   r   a   e   g   y   r   a    t   e   n   a    l    P    3  .    5  .    6

LEGEND

9 8

   N    I    A    R    T    E    V    I    R    D

7 6

b

11 5 4 a 3 2 1

Single planetary gear set  6.26

10

a b 1 2 3 4 5 6 7 8 9 10 11

Drive Output Planetary ge gears Planet carrier Driv Drive e sha shaft ft for for pla plane nett car carri rier er Driv Drive e sha shaft for for sun sun gear gear Sun gear Driv Drive e shaf shaftt for for inte intern rnal al gear gear Interna rnal ge gear ca carrier Internal gear Brake shoes Outp Output ut shaf shaftt for int inter erna nall gear gear Output Output shaft shaft for planet planet carri carrier er

  x

 FUNCTION 

5

6 b

b

a c

c

8

2

a

1st gear: internal gear fixed, sun gear driven, output on planet carrier

2nd gear: sun gear fixed, internal gear driven, output on planet carrier

c

b

a c b

a   x

   N    I    A    R    T    E    V    I    R    D

3rd gear: sun gear, internal gear and planet carrier blocked: direct gear a b c

Output Drive Inte Intern rnal al rotat otatio iona nall mov movem emen entt

Gear ratios with single planetary gear set 

6.27

2 5 8

Planet gear carrier Sun gear Internal gear

Reverse gear: planet carrier fixed, sun gear driven, output at internal gear with reverse direction

6

 BASIC PRINCIPLES PRINCIPLES

 FUNCTION 

 Automatic gearbox gearbox  Automatic gearboxes enable enable automatic changes of gears without intervention on the part of the driver. The clutch is eliminated; all driving operations, including driveaway and manoeuvering, are automatic. However, a selector lever or pushbuttons can be used to preset certain gearshift programs or step-up ranges.  Another possibility to influence influence gear changes is the "kickdown". Pressing the driving pedal as far as it will go leads to the earliest possible downward shift to the next-lowest gear.

Components of automatic gearboxes  The connection between between the drive shaft shaft and the actual gearbox is by means of a hydrodynamic torque converter, usually constructed according to the "Trilok" principle. This increases the engine torque and also ensures a soft, smooth driveaway. At higher rotational speeds, the converter is bridged to avoid slip inherent in the design principle (converter lockup clutch ➜ page 6.8 ).

Due to the torque converter, the efficiency of automatic gearboxes is poorer than that of manual gearboxes. Electronic control of automatic gearboxes, however, enables operation of the engine in ranges that favour the fuel consumption level.  This compensates for the poorer efficienefficiency. With the exception of buses and municipal vehicles, automatic gearboxes play a subordinate role in the area of commercial vehicles. The reason for this is the higher costs compared to those for manual gearboxes.

Upstream of the converter is a planetary gearbox with a number of planetary gear sets (➜ page 6.26 ). The number of sets results from the number of gear steps.  The planetary gear gear sets convert the torque and rotational speed and reverse the direction of rotation for reverse gear.

 Selector lever position  Driving speed  Engine load

With the purely hydraulic control system, an oil pump generates a working pressure. The selector lever (setting by the driver) and a hydraulic shifting block activate and engage the drive clutches depending on requirements. In the case of an electrohydraulic control system, activation of the drive clutch is hydraulic; the electronics distribute the pressures and thus the gear selection.

 The gears are shifted shifted without tractive tractive power interruption. Multi-disc clutches shift the planetary gear sets and connect the individual gears or gear carriers of the p lanetary gear sets, thus creating the different gear ratios. Multi-disc brakes provide the corresponding blocking of the planetary gear sets. Control of automatic gearboxes Control is either purely hydraulic or electrohydraulic. It has the task of effecting the automatic upshift and downshift of the individual gears at the right time. Control takes place depending on the following factors:

  x   o    b   r   a   e   g   c    i    t   a   m   o    t   u    A    4  .    5  .    6   x

LEGEND

   N    I    A    R    T    E    V    I    R    D

2

3

1

4

5

 Automatic gearbox  gearbox  6.28

1 2 3 4 5

Con Conver verter ter loc lockup kup cl clutc utch Torque co converter Mult Multii-di disc sc clut clutch ch or brak brakes es Planet ge gear sets Elec Electr troh ohyd ydra raul ulic ic con contr trol ol uni unitt

 BASIC PRINCIPLES PRINCIPLES

6

 FUNCTION 

Power take-offs Power take-offs are used to drive feed pumps, cranes, cement mixer pumps and other power units. Distinctions are made between:  Engine-dependent power take-offs  Clutch-dependent power take-offs

Depending on the intended use, they are connected to the engine, in the propshaft train or the transfer case ( ➜ page 6.35 ).  The operation of modern power power take-offs is often possible with the vehicle either stationary or moving. Above all cement mixers require the power take-off also while the vehicle is being driven. Clutch-dependent power take-offs are the classical power take-offs for external power units. Various connection options are integrated in each gearbox by the large gearbox manufacturers such as ZF and EATON.

Engine-dependent power take-offs Engine-dependent Engine-dependent power take-offs are mounted in front of the standard gearbox and clutch and are usually connected directly to the camshaft of the engine. They are integrated in the clutch bell and always run at engine speed. Force transmission is independent of the driving clutch.  The engine-dependent engine-dependent NMV 130 E ( ➜ Fig.) is can also be engaged while the vehicle is being driven or under load by means of a built-in hydraulic multi-disc clutch. It is used where extremely high power output is required:  Cement pumps

mixers   Transport cement mixers

box; the power take-off can be engaged.  The PTO must be engaged engaged and disengaged when the vehicle is stationary. Depending on the area of application, more or less powerful power take-offs are used. Depending on the type, they are suitable for short-term or continuous use:  Bulk transporters   Tankers

cranes   Truck-mounted cranes  Multibucket trucks  Fire engine turntable ladders  Dumpers   Articulated arms with with platforms

 High pressure cleansing and vacuum

trucks  Drill carriers   Airfield fire engines engines   Truck-mounted cranes cranes

Clutch-dependent power take-offs Clutch-dependent power take-offs are normally flanged onto the output end of the gearbox and driven by the countershaft of the gearbox ( ➜ page 6.17 ). The connection is by means of a dog sleeve. When the engine is running and the clutch engaged, the countershaft turns the gearbox. Operating the clutch interrupts the connection between the engine and gear-

  s    f    f   o     e    k   a    t   r   e   w   o    P    5  .    5  .    6

LEGEND

1 2

   N    I    A    R    T    E    V    I    R    D

(NMV 130 E)

1

(ZF 16 S 109)

2

Mounting options for power take-offs (example ZF) 6.29

Engi Engine ne-d -dep epen ende dent nt pow power er tak takee-of off  f  Clut Clutch ch-d -dep epen ende dent nt powe powerr taketake-of offs fs

  x

 BASIC PRINCIPLES PRINCIPLES

6

Propshafts  To transfer the power output from the gearbox to the transfer case and/or final drive (depending on the number of driven axles), shafts with universal joints (cardan  joints) are required, so-called propshafts.  At MAN, these are connected connected by crosstoothed mounting flanges ( ➜ Fig.).  A fundamental distinction distinction is made in the arrangement of propshafts: the Z arrangement and W arrangement. The Z arrangement or Z inflection is regarded as the usual application on commercial vehicles. It is also used in MAN commercial vehicles. On account of the vertical movement of the axles, the propshafts must be fitted with a length compensation (shifting section toothing). With wider wheelbases, MAN uses propshaft intermediate bearings muffled with rubber. These are very quiet, run smoothly and require little maintenance.

 FUNCTION  Gimbal error Inflected propshafts with only one universal joint are unable to transfer even rotational movements. The circular rotation of the drive shaft only leads to sinusoidal rotation of the driven shaft. This also reduces the angular velocity of the driven shaft when the joint forks of the drive shaft are horizontal (flattened range of the ellipse path of the driven shaft). This effect is all the stronger the greater the angle of inflection α of the propshaft. This is also referred to as "gimbal error".  These synchronisation fluctuations can be balanced out by fitting a second universal  joint. All the propshafts propshafts in the drive trains of commercial vehicles must therefore be fitted with at least two universal joints.

propshaft, the joint forks of shared shaft must lie on one level. The amount of the two angles of inflection must also be the same size ( ➜ Fig. page 6.31 ). W arrangement  Also in the case of the W arrangement, the universal joint forks must lie on one level and the angles of inflection must be the same size to balance out the gimbal error (➜ Fig. page 6.31 ). With the W arrangement, only the drive or output shaft can be arranged horizontally.  The W arrangement arrangement is not usual on commercial vehicles. It is only used for accessories of the superstructure.

 Angle of inflection inflection  The angle of inflection α refers to the angle by which the universal joint of a propshaft is set. It must not be too large, as otherwise uniform force transmission is no longer possible, resulting in excessive loads on the  joints and thus heavier heavier wear. wear. The angle of inflection is normally approximately α = 8°. However However,, angles angles of up up to 35° are are also technically possible. Z arrangement For complete synchronisation of the drive and output shafts connected by the

  s    t    f   a    h   s   p   o   r    P    6  .    6

LEGEND

1 2 3 4

   N    I    A    R    T    E    V    I    R    D

1

Universal joint  6.30

2

3

4

Cross-toothed Cross-toothed mounting flange

Articulated sh shaft Universal jo joint Cros Crosss-to toot othe hed d mou mount ntin ing g fla flang nge e Fina inal dr drive ive (h (hypoi ypoid d axl axle) e)

  x

 FUNCTION 

6

α2

 = α2

α1

α1

Z arrangement

α2

α1

  x

 = α2

α1

   N    I    A    R    T    E    V    I    R    D

6.31

W arrangement α

 Angle of inflection

Propshafts

6

 BASIC PRINCIPLES PRINCIPLES

 FUNCTION 

 Axle drive  The final drive, also also referred to as the middle drive, transfers the rotational movement of the propshaft to the drive shafts of the wheels. The middle drive includes the axle drive with the axle-drive ratio and the differential gear ( differential ➜ page 6.33 ).

Bevel gear axle drive  A simple bevel gear axle drive drive consists of a drive bevel gear (drive pinion) and a ring gear.

 The axle drive has has the following tasks: increase (ade  Torque transfer and increase

from the ratio of number of teeth on the drive bevel gear and ring gear.

 The drive bevel gear is mounted on the drive axle, which is connected to the propshaft by means of a universal joint. It drives the ring gear and thus the axle. Depending on the arrangement, a distinction is made between:  Hypoid drive (axle of drive and ring

quate for every driving state)

gear are offset),

 Stepping down the rotational speed of

 Drive without axle offset.

the drive propshaft to slow  Deflection of the power flow, normally

by 90° (when the engine is fitted towards the vehicle longitudinal axis) In order to be able to perform these tasks, axle drives are built as bevel gears or worm gears ( ➜ page 6.14 ). In commercial vehicle construction, bevel gear axle drive are normally used.

Toothing of hypoid drives  The toothing of hypoid drives drives is usually spiral toothing. In commercial vehicles, the following advantages mean that mainly hypoid drives are used: enables use of larger larger   The axle offset enables drive bevel gears with correspondingly larger and stronger teeth; the service life of the axle increases.   A greater number of teeth is engaged;

in conjunction with the spiral toothing, this means greater running smoothness.  With the same gear ratio, the ring gear

can be made smaller. The hypoid drive is smaller.   e

Normally, a single gear ratio is sufficient for the axle drive ( ➜ page 6.2 ). It results

  v   s    i   r   e    d    l   x   e   a    l   x   n    A   e   e   v   v   i   r    1    i    d  .   r    l   a    1   n    i  .    D   F    7  .  .    1 . .   7    6    6   x    6   7

LEGEND

2

   N    I    A    R    T    E    V    I    R    D

B

1 2

 Axle drive 6.32

 A B 1 2

1

 A 

Drive without axle axle offset Hypo Hypoid id dri drive ve (wi (with th axl axle e offs offset et)) Ring gear Bevel gear

 BASIC PRINCIPLES PRINCIPLES

6

 FUNCTION 

Differential gear On cornering, the wheel nearest to the curve and the wheel furthest from the curve cover different distances ( ➜ page 3.23 ). The outer wheel wheel must cover a greater distance than the inner wheel. This means it has to roll at higher speed; its rotational speed is greater than that of the inner wheel. Depending on the speed of a vehicles, the corner radius, the condition of the road surface and the weather conditions, different rotational speeds can occur on the wheels of one axle. In order to balance out these rotational speed differences, a differential gear (differential) must distribute the revolutions from the ring gear of the axle drive to the axle shafts of the wheels.  A general general distinction is made between bevel gear and spur gear differential gears. Bevel gear differential gears are normally used in commercial vehicles.

Basic function of the differential  The differential differential gear consists of the differential housing and four differential bevel gears as well as two drive bevel gears (axle drive bevel gears).  The ring ring gear that is firmly attached attached to the differential housing is driven by the cardan shaft via the drive bevel gear.  The four differential bevel gears in the houhousing engage in the two drive bevel gears on the axle shafts (which is why they are also called axle drive bevel gears). Driving straight ahead When driven straight ahead, both axle drive bevel gears rotate at the same speed; the differential bevel gears do not turn, rather they revolve with the ring gear. They equally distribute the propelling force to the axle drive bevel gears. Cornering On cornering, the outer axle shaft rotates more quickly than the inner shaft. The differential bevel gears enable the different speeds of the two axle drive bevel gears.  The differential differential bevel gears rotate rotate around their axes and thus balance out the rotational speed difference between the axle drive bevel gears.

page 3.4 ), planetary planetary drive axles each have a planetary gear set on the wheel hubs ( ➜ Fig. page 3.5 ). The two sets of planetary planetary gears assume most of the torque conversion and gear stepping. This is why t he torque transfer in the middle drive is not very great. It is significantly smaller than the middle drive of a hypoid axle.  The smaller differential differential means that planeplanetary drive axles have greater ground clearance. This is why they are often used for construction site vehicles. The additional planetary gear set on the wheel hubs means they are recommended for the transport of heavy loads. Inter-axle differential differential  An inter-axle differential differential is included included as a differential gear in a drive-through axle ( ➜ page 3.4 ). In principle, it works in the the same way as the differential in the axle drive to balance different wheel speeds. However, the inter-axle differential is arranged in the drive-through axle, balancing the speed between the 1st and 2nd axles of the tandem-axle assembly.

Differential of planetary drive axles In contrast to hypoid axles, where the power flow and torque is only stepped up and distributed in the middle drive ( ➜

  r   a   e   g    l   a    i    t   n   e   r   e    f    f    i    D    2  .    1  .    7  .    6   x

LEGEND

a b

   N    I    A    R    T    E    V    I    R    D

a b c

1 2 3 4 5 6

c d 1 2 3 4 5 6 7

b d

d

c 7

6.33

5

4

 Axle drive with differential gear (differen(differential)

Speed balancing in the final drive on cornering

Drive (p (propshaft) Gear Gear rat ratio io (fo (forc rce e tran transm smis issi sion on)) Rota Rotati tion onal al spe speed ed dif diffe ferrence ence com com-pensation Output (axle shafts) Drive bevel gear Ring gear Dif Differ ferenti entia al hou housing sing Dif Differ ferenti ntial bev bevel el gea gears Axle dr drive be bevel ge gears Right-h t-hand ax axle sh shaft Left-ha -hand ax axle sh shaft

 BASIC PRINCIPLES PRINCIPLES

6

Differential lock With different traction of the two drive wheels (one-sided smooth road surface, mud, sand, gravel) or with an extreme inclination of the vehicle, the following effect can occur: One of the driven wheels spins due to the lack of propulsion power transfer; the other remains at a standstill due to the function of the differential (differential gear). The vehicle cannot be moved.

 FUNCTION 

 EXAMPLE 

Engaging and disengaging differential lock  The engaging and disengaging disengaging differential lock connects an axle shaft with the differential housing and ring gear. This means the differential bevel gears can no longer roll on the axle drive bevel gears. This creates a rigid connection of the two axle shafts in the d ifferential housing. The speed balancing is then locked.

In commercial vehicles, engaging and disengaging differential locks are preferred.  Automatic differential locks with multi-disc clutches ( ➜ page 6.10 ) are used above all in racing cars and high-quality passenger cars. Engaging and disengaging differential locks may only be switched on when the vehicle is stationary or at low speed.

Due to the high propelling force that fully affects the differential on driveaway, the differential may only be locked in the situations described and at lower speed (maximum of 15 to 20 km/h).

 A differential lock uses uses a mechanical mechanical or electropneumatic dog clutch to reconnect the axle shafts separated in the differential via housing and ring gear. Different rotational speeds of the two d rive wheels are then no longer possible.

 Automatic differential differential lock  Automatic differential differential locks feed more torque to the wheel with the better road grip, as determined per wheel sensors, even at higher speeds.

 Also in drive-through axles, which have an inter-axle differential for speed balancing between the 1st and 2nd axle of the tandem-axle assembly, there is usually an engageable differential lock. The inter-axle differential lock is engaged when all the wheels on one of the two driven axles spin.

   k   c   o    l    l   a    i    t   n   e   r   e    f    f    i    D    3  .    1  .    7  .    6   x

LEGEND

1 2

   N    I    A    R    T    E    V    I    R    D

1 2 6

3

9

8

7

6

Final drive of a hypoid axle with differential lock  6.34

5

4

3 4 5 6 7 8 9

Dif Differ ferenti ential al lock lock (dog (dog clut clutch ch)) Gear Gearsh shif iftt slee sleeve ve of of the the diff differ eren enti tial al lock (can be shifted on the axle shaft toothing) Axle shaft toothing Pneu Pneuma mati tic c gear gearsh shif iftt ele eleme ment nt Cont Contro roll for fork k of of the the diff differ eren enti tial al lock  lock  Axle dr drive be bevel ge gears Dif Differ ferenti ntial bev bevel el gea gears Diff Differ eren enti tial al hous housin ing g wit with h rin ring g gea gearr Drive bevel gear

 BASIC PRINCIPLES PRINCIPLES

6

 FUNCTION 

Transfer case Commercial vehicles that are deployed under difficult conditions (construction site, off-road, winter) usually have a number of driven axles. If all axles of a vehicle are driven, this is referred to as all-wheel drive. In order to implement all-wheel drive, torque distribution is necessary. As a rule, a transfer case is used for this purpose on commercial vehicles.  The transfer transfer case is connected connected to the mulmulti-ratio gearbox by means of a propshaft or is directly flanged on. The transfer case has one flange to secure a propshaft to the drive of the front axle and one flange to secure a propshaft to the drive of the rear axle ( ➜ Fig.). With a two-stage transfer case, the stepup range of the drive train can also be expanded.

Engageable front axle No differential gear is required on transfer cases with engageable front axles. The driving torque is transferred in equal parts to the front and rear axles. The difference in travel when the vehicle is being driven is not balanced out. For this reason, allwheel drive may only be switched on if there is poor traction, so as not to subject the components of the drive train to unnecessary loads and to keep the tyre wear as low as possible. Permanent all-wheel drive When the vehicle is being driven, there are differences in the travel between the d rive axles. In order to balance out the resulting rotational speed difference, vehicles with permanent all-wheel drive must be equipped with a differential gear in the transfer case.

case is also equipped with a lock. In the case of manual locks, a dog clutch ( ➜ page 6.10 ) is normally used. Drive-through axle In the case of the all-wheel drive concept with more than two driven axles (e.g. 6x6), so-called drive-through axles are used.  There is an output at the rear end, where where a propshaft to the drive of the second axle is flanged on ( ➜ Fig. page 6.36 ). On the drive-through axle, torque and rotational speed are picked up via a spur gear ratio ( ➜ page 3.4 ). The The drive-through also contains an inter-axle differential for speed balancing between the 1st and 2nd axles of the tandem-axle assembly, which as a rule is equipped with an engaging and disengaging differential lock (interaxle differential lock).

In addition, using a planetary gear set as a differential gear can adapt the torque distribution to the axle loads. This is done by changing the sun gear and internal gear diameters. The front axle, for example, can be supplied with 30 % of the torque and the rear axle, due to the greater axle load, with 70 % of the torque. To halve the torque, a bevel gear differential ( ➜ page 6.33 ) is used.

  e

  e   s   v   a    i   r   c    d   r   e    l   e   f   e   s    h   n   r   w  a      T    l    l    1  .    A   2    2  .  .    7  .  .    7    6   6   x

In order to be able to transfer the maximum engine torque even with poor traction, the differential gear in t he transfer LEGEND

1

   N    I    A    R    T    E    V    I    R    D

1 a

c

3

Transfer case (schema) 6.35

a

2

b

c

3

MAN transfer case

2

a b c 1 2 3

Pow Power flow flow from from gea gearbox rbox Pow Power flow flow to rear ear axle xle Pow Power flow flow to fron frontt axle xle Gearshift sleeve Gear ratio steps Shif Shiftt cyl cylin inde derr for for enga engagi ging ng the the fro front nt axle via dog clutch (all-wheel drive)

 FUNCTION 

6

4x2 hydrostatic drive  The hydrostatic hydrostatic drive is an engageable allwheel drive technique for vehicles with occasional off-road operation. On a conventional all-wheel drive ( ➜ Fig. 4x4 and 6x6), the transfer elements of the front axle drive are always moved. On commercial vehicles with hydrostatic drive, only the rear wheels are driven conventionally when the vehicle is driven on roads.

 EXAMPLE 

4x2 hydrostatic drive

In driving situations that require all-wheel drive, the hydrostatic drive can be engaged at any time. If the hydrostatic drive is engaged, a hydraulic pump ( ➜ Fig., item 2) supplies the hydrostatic wheel motors (4) directly with pressure up to 420 bar.  The front wheels are then driven up to a speed of 30 km/h.  The use of hydrostatic wheel motors elimieliminates the transfer case that is typical of allwheel drive. The advantages are:

4

3 2

1

4x4

 More favourable fuel consumption  Weight advantage of around 400 kg  No raising of the driver's cab and

frame is required (the visual appearance of the road vehicle is retained)

1 5

4x4 all-wheel drive With conventional all-wheel drive, the gearbox is connected to the transfer case ( ➜ Fig., item 5) via a propshaft (1), to which propshafts are flanged onto the drives of the front and rear axles. Depending on the version of the transfer case, the drive of the front axle is engageable or permanent (➜ page 6.35 ).

   N    I    A    R    T    E    V    I    R    D

6x6 all-wheel drive  The 6x6 all-wheel all-wheel drive is based on the 4x4 drive concept. However, the 1st rear axle is designed as a drive-through axle, which has an inter-axle differential for speed balancing between the 1st and 2nd axle of the tandem-axle assembly (as a rule with engageable differential lock). The drive-through to the 2nd rear axle is via a propshaft.

1

  s    t   p   e   c   n   o   c   e   v    i   r    D    2  .    2  .    7  .    6   x

1

6x6

1 5

LEGEND

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Propshaft Hydraulic pump High-pr -pressure line Hydr Hydros osta tati tic c wh wheel eel mot motor ors s Transfer ca case

1

1

Hydrostatic drive and conventional all-wheel drive 6.36

1