DE102011087524A1 - Belt drive with switchable planetary gear - Google Patents

Abstract

The invention relates to a belt drive of a drive train of a motor vehicle with a planetary gear shifting a gear ratio between a starter generator and an internal combustion engine with a ring gear that can be connected to the housing by means of a disc brake, a web connected to a crankshaft of the internal combustion engine of the drive train with planetary gears arranged around the circumference and one with a The rotor of the starter generator and at least one auxiliary unit rotationally connected sun gear and two freewheels that can be switched against one another in order to control a torque direction between the rotor and the crankshaft. In order to be able to switch both the freewheels and the disc brake together and to prevent them from being switched at the same time, the disc brake is actuated alternately by a first actuation unit and the freewheels by a second actuation unit and the actuation units by means of a self-locking linear actuator.

Description

The invention relates to a belt drive of a drive train of a motor vehicle with a planetary gear that can be connected to a gearbox by means of a disc brake, a ring gear connected to a crankshaft of the engine of the drive train with planet gears arranged around the circumference and one with a planetary gear Rotor of the starter generator and at least one accessory rotatably connected sun gear and two mutually switchable freewheels to control a torque direction between the rotor and the crankshaft.

Generic belt drives are, for example, from the German patent applications DE 199 417 705 A1 . DE 10 2004 060 991 A1 and DE 10 2007 021 233 A1 known. This is the object of a starter generator, which should ensure the generator function, the starting function of the engine, a torque assist the engine (Boost function) and a stationary air conditioning by driving an enclosed in the belt drive air compressor with a stationary engine, as effectively and with low power and to design a small space. Here, a transmission, preferably a planetary gear is provided which provides two gear ratios, so that the required by the starter generator range of action is covered by a variation of the operating speeds of the starter generator. On the one hand, the ratio of the planetary gear and, on the other hand, the direction of the moment flux between the rotor of the starter generator and the crankshaft of the internal combustion engine are to be controlled. The control of the planetary gear is based on an optionally freely rotating or fixed to the housing by means of a disc brake ring gear and the control of the torque flow, a switching device in the form of two switchable freewheels.

The object of the invention is the formation of an efficient and error-free operation of the clutches and the disc brake.

The object is achieved by a belt drive of a drive train of a motor vehicle having a planetary gear that can be connected to a transmission by means of a disc brake, a ring gear connected to a crankshaft of the drive train of the internal gear with a planetary gear arranged around the circumference, and a planet gear a rotor of the starter generator and at least one accessory rotatably connected sun gear and two mutually switchable freewheels to control a torque direction between the rotor and crankshaft, solved, the disc brake by a first actuator and the freewheels are operated by a second actuator and the actuator units by means of a self-locking linear actuator are operated alternately. By determining the alternate operation of the freewheels and the disc brake is a misoperation of a simultaneous or overlapping circuit of this, which may be associated with damage or destruction of the planetary gear due damaging torque input excluded.

Furthermore, freewheels and disc brake can be actuated by means of a single, arranged directly radially outside the disc brake actuator such as linear actuator and thus costs and space can be saved. Linear actuators in the form of electric motors with a spindle drive have proved to be particularly advantageous. Due to the self-holding design, the linear actuator can be held in any position without further supply of energy such as electrical energy. Thus, for example, the preferably opened in the normal state and forcibly closed disc brake can be kept closed without supply of energy or switched preferably connected with open disc brake freewheel without further power supply. As a result, the efficiency of the belt drive and thus the equipped with this motor vehicle is improved.

The disc brake is preferably formed of a brake disc and two brake pads arranged on both sides thereof, axially biased against one another by means of an energy accumulator, and braked against the action of the energy accumulator by the linear actuator against the brake disc. The energy storage can be formed for example from one or more coil springs.

The freewheels may be formed from distributed over the circumference, for example, arranged between an inner star and an outer ring clamping bodies, both freewheels may contain the same foreign body and the inner star starting from a neutral position opposite clamping ramps may have, so that by mutual displacement of the clamping body two against each other , in each one of the two circumferential directions blocking and in the other circumferential direction rolling freewheels are formed. The displacement of the clamping body along the clamping ramps takes place by means of a clamping body receiving sprag cage, which is displaced accordingly by a cable, wherein the cable the distance between the arranged in the region of the sun gear freewheels and the linear actuator balances and is actuated by the second actuator unit and thus by the linear actuator.

The freewheels are preferably arranged between the sun gear and the web and set a desired torque flow between the rotor of the starter and the crankshaft of the internal combustion engine depending on the set by the switching state of the planetary gear torque flow. As a result, the various operating conditions of the belt drive are made possible. For example, the freewheel, which is preferably switched without the action of the linear actuator, overruns the crankshaft when the crankshaft is stationary and the disc brake is open, and drives the air conditioning compressor via a belt of the belt drive in order to achieve stationary air conditioning. In the same switching state, the rotating crankshaft can transmit torque without translation to the rotor, thus enabling generator operation. In a circuit of the freewheels can be transmitted from the rotor to the crankshaft with open disc brake without switched ratio, so turned on the stationary crankshaft and the internal combustion engine are started or provided with the internal combustion engine, a boost operation. When the disc brake is closed occurs due to the torque flow via web and planet gears to the sun gear, a momentum reversal, so that the preferred without intervention of the linear actuator freewheel with a reduction of, for example 1: 3, the rotor can crank the crankshaft to start the engine or at low speeds rotating crankshaft can drive the rotor with a translation of 3: 1 in a speed range with good efficiency.

The linearly displaced ram such as spindle of a spindle drive has according to the inventive idea neutral position, in which neither of the two actuating units is displaced therefrom and from which the plunger is axially displaceable in two directions of movement, wherein in each case one of these directions of movement an actuating unit independent of the other operating unit is actuated. Here, in the neutral position in a preferred manner, the disc brake is opened and a preferred, for example, the overrunning of the crankshaft by the starter generator enabling freewheeling connected.

Seen from another point of view, the plunger can travel through an entire travel path, wherein the actuating units are taken along by the plunger via a partial path of the entire stroke of the plunger and a partial path of an actuating unit is limited in each case for the other actuator unit by means of a stop, so that by appropriate arrangement of the stops it is excluded that both operating units are operated overlapping or simultaneously.

According to an advantageous embodiment, the first actuating unit is provided with a brake lever displacing the rotary lever, which is guided in a longitudinal slot of the plunger and taken over a partial path of a boundary of the longitudinal slot. The second actuating unit may include a housing fixed rotatably arranged lever which is axially acted upon by the axially displaced ram and thereby undergoes a rotational movement, by means of which the cable attached to the lever of the cable is zugverlagert by a corresponding amount and at the other end the sprag cage and thus the Relocated clamping body on the opposite clamping ramps of the inner star, so that is switched from the currently switched freewheel to the other freewheel.

In a preferred embodiment, it is provided to limit the rotary lever in the neutral position of the plunger and the lever upon contact of the rotary lever at the boundary of the longitudinal slot by means of one stop.

The invention is based on the in the 1 to 9 illustrated embodiment illustrated. Showing:

1 a belt drive shown schematically,

2 the belt drive the 1 in schematically represented view,

3 a schematic diagram of the linear actuator in neutral position

4 a schematic diagram of the linear actuator of the 3 with switched disc brake,

5 a schematic diagram of the linear actuator of the 3 and 4 when switching the freewheels,

6 a section through a structurally elaborated transmission / actuator unit of 2 .

7 a view of the transmission actuator unit of 6 .

8th a highlighting the switching of the freewheeling detail of the transmission / actuator unit of 6 and 7 and

9 a highlighting the circuit of the disc brake detail of the transmission / actuator unit of 6 and 7 ,

The 1 shows a schematic representation of the drive train 1 a motor vehicle with the internal combustion engine 2 , the belt drive 3 , the friction clutch 4 , the transmission 5 and the drive wheel 6 ,

The internal combustion engine 2 drives with its crankshaft 8th both the transmission 5 , which can be designed as a manual transmission, automated manual transmission, dual clutch transmission and the like, as well as the belt drive 3 at. The belt drive 3 contains the starter generator 7 its rotor 9 rotationally locked, for example coaxially or by means - not shown - pulleys and belts with the crankshaft 8th the internal combustion engine by means of the opposite effective and switched by means of the lever actuator, not shown, switching device according to the invention in the form of freewheels 10 . 11 is provided connectable. The first freewheel 10 Switches the torque flow from the crankshaft 8th to the rotor 9 and locks in the reverse direction, while the second freewheel 11 the torque flow from the rotor 9 to the crankshaft 8th unlocks and locks in the opposite direction. The freewheels 10 . 11 are switched alternatively. Between the rotor 9 and the crankshaft 8th is below the planetary gear 12 switched, whose ring gear 13 by means of the disc brake 14 fixed to the housing, for example with the motor housing 21 the internal combustion engine 2 can be connected. The sun wheel 15 is rotationally locked with the rotor 9 connected. The between ring gear 13 and sun gear 15 meshing planet gears 16 are at the jetty 17 added. The jetty 17 is rotationally locked with the crankshaft 8th connected.

Furthermore, with the rotor 9 at least one accessory 18 rotationally connected, for example by means of a pulley in the belt of the belt drive 3 involved. In the embodiment shown, the accessory is 18 through the air conditioning compressor 19 formed, with or without fixed translation with the rotor 9 is rotationally connected.

The crankshaft 8th is the pulley damper 20 associated rotationally, which can be designed as a damper and / or damper.

By appropriate operation of the freewheels 10 . 11 and the disc brake 14 By means of the actuator, not shown, all actuating functions controlling actuator in the form of operating units are corresponding operating states of the drive train 1 controlled. This is controlled by the disc brake 14 the translation of the planetary gear 12 and the freewheels the torque fluxes between rotor 9 and crankshaft 8th , Depending on the operating condition of the internal combustion engine 2 and the starter generator 7 result in several advantageous operating states of the drive train 1 , in the following 5 to 7 will be discussed in detail. When setting the operating conditions comes the disc brake 14 to the load-switching function of the planetary gear 12 a crucial function too.

The 2 schematically shows the belt drive 3 in view with the crankshaft 8th , the starter generator 7 with the rotor rotating in the direction of the arrow 9 and the tension rollers 22 , The belt 23 connects the components of the belt drive 3 rotationally locked, being next to the air conditioning compressor 19 optionally further - not shown - ancillaries in the belt drive 3 can be driven by a separate pulley or integrated in one of the listed components. At the crankshaft 8th sits the not explicitly shown gear / actuator unit 24 with the planetary gear, the operating units and a Doppelhubmagneten.

The 3 shows a schematic diagram of the housing fixedly arranged linear actuator 25 with the axially displaceable, self-locking ram 26 , This alternately actuates the actuators 27 . 28 , The first operating unit 27 is used to operate the disc brake 14 with the rotation with the ring gear 13 ( 1 ) connected brake disc 29 and the non-rotatable and axially gegeneiner against the action of a non-visible energy storage against the brake disc 29 clamped brake pads 30 , Due to the spaced bias of the brake pads 30 is the disc brake 14 open (normally open) in the absence of loading and by means of the linear actuator 25 closed. For this purpose accesses the brake pads 30 the rotary lever 31 to that in the longitudinal slot 32 of the plunger 26 is guided and by means of a thread-like connection 33 caused by a rotation by the plunger axial displacement of the brake pads against each other.

The second operating unit 28 serves the switching of freewheels 10 . 11 ( 1 ). For this purpose, the housing is fixed and rotatable lever 34 from the loading area 35 of the plunger 26 during its displacement in the direction of the lever 34 charged and around the camp 36 twisted and the one with the lever 34 Connected cable 37 loaded in tension.

3 shows the neutral position 38 of the plunger 26 in which neither of the two actuators 27 . 28 is charged. The rotary lever 31 the first operating unit 27 is located in non-loaded contact with the boundary 39 of the longitudinal slot 32 and on the housing-fixed stop 40 , The loading area 35 of the plunger 26 and the lever 34 have a game 41 on. The lever 34 is thereby represented by a, not shown, for example in the field of Springs cage energy storage arranged on the cable 37 held under tension and its deflection by the stop 45 limited.

The 4 shows the linear actuator 25 with in the direction of the arrow 42 from the neutral position 38 displaced ram 26 , This takes the limit 39 of the longitudinal slot 32 the rotary lever 31 with and twist this at the thread-like connection, so that the brake pads 30 with the brake disc 29 be braced and therefore the disc brake is closed and the ring gear 13 ( 1 ) through the brake pads 30 is fixed to the housing and thus the over the planetary gears 16 ( 1 ) connected translation of the planetary gear 12 ( 1 ) is activated. The second operating unit 28 stays with the displacement of the ram 26 in the direction of movement shown in relation to the neutral position of 3 unchanged. The lever 34 remains at the stop 45 created.

The 5 shows a displacement of the plunger 26 of the linear actuator 25 in the direction of the lever 34 starting from the neutral position 38 in the direction of the arrow 43 while consuming the game 41 of the 3 and lift off the stop 45 with subsequent twisting of the lever 34 through the loading area 35 of the plunger 26 , The rotation of the lever 34 in the direction of the arrow 44 sets the cable 37 under train, which implements a switching of the freewheels by tensile load on the sprag cage. The first operating unit 27 remains unactuated by the movement of the rotary lever 31 at the stop 40 is limited. This leaves the disc brake 14 in their predetermined open position.

6 shows a section through a structurally executed embodiment of the transmission / actuator unit 24 with the on the motor housing 21 fixed linear actuator 25 and the planetary gear 12 That's out of the pulley 46 connected sun gear 15 on the jetty 17 attached planet wheels 16 and with the disc brake disc 14 rotatably connected ring gear 13 is formed. Between the sun wheel 15 and the jetty 17 are the opposite freewheels 10 . 11 arranged effectively. These are from the with the shaft part 58 one-piece connected inner star 48 with distributed in the circumferential direction to a neutral position respectively counter-rotating clamping ramps 49 . 50 between these and the one with the sun gear 15 one-piece outer ring 51 arranged clamping bodies 52 and the switching mechanism 53 educated. The switching mechanism 53 consists of the the clamping body 52 axially and circumferentially leading sprag cage 54 that opposes the effect of the energy store 47 from the cable 37 is axially displaceable. Between the rope 56 of the cable 37 connected train basket 55 and the sprag cage is the torsionally coupled threaded connection 57 effective at an axial displacement of the train cage 55 through the rope 56 of the cable 37 the means of energy storage 47 preset freewheel 10 by circumferential displacement of the sprag cage 54 disabled and the freewheel 11 switches, in which the clamping body 52 from the clamping ramps 49 on the clamping ramps 50 be relocated.

The inactive state of the second actuator unit 28 of the 4 preset freewheel 10 locks with the disc brake open 14 and thus inactivated planetary gear 12 the rotational movement of the shaft part 58 coupled crankshaft 8th ( 1 ) opposite the sun wheel 15 , The sun wheel 15 can by means of the freewheel 10 roll over the shaft part. As a result, the crankshaft can turn the pulley 46 and this with the starter generator 7 ( 1 ) connecting belt over the sun gear 15 in generator mode. When the crankshaft is stationary, the rotor of the starter generator can roll over the crankshaft and drive an air conditioning compressor for stationary air conditioning via the belt.

The corresponding to the 5 switched freewheel 11 locks with open disc brake 14 the sun wheel 15 against the shaft part 58 and thus against the crankshaft, so that over the pulley 46 from the starter generator to the start of the internal combustion engine and in a boost operation torque can be transmitted to the crankshaft.

In the switched state of the disc brake 14 according to 4 Only the preset freewheel can be switched. This overruns over the pulley 46 sun gear driven by the starter generator 15 the shaft part 58 and drives the planet wheels 16 and with it the jetty 17 on, due to its rotationally fixed connection with the shaft part 58 the crankshaft drives. Here, the translation of the planetary gear acts 12 decreasing for the speed of the starter generator, so that the stationary crankshaft driven at a higher speed of the starter generator and the internal combustion engine can be started or at low speeds of the crankshaft, a boost operation can be made. When driving the crankshaft drives the shaft part 58 the jetty 17 and the planet wheels 16 in turn, the sun gear 15 drive that freewheel 10 rolled over and the translated speed through the pulley 46 transfers to the belt and the starter generator. Here, at low speeds of the crankshaft of the starter generator can be operated at higher speeds and improved efficiency.

7 shows the trimmed, arranged on the crankshaft axis gear / actuator unit 24 of the 6 in view with implied, in 2 described belt drive 3 , On the motor housing 21 is the linear actuator 25 in the form of the electric motor 59 with the spindle gear 60 added. Into that the housing 61 of the spindle gear 60 are the non-visible operating units 27 . 28 ( 3 ). At this are the support parts 62 for the brake pads for acting on the brake disc 29 the disc brake 14 arranged. The pulley 46 at the same time forms a housing 64 for the planetary gear 12 with the ring gear 13 at the footbridge 17 recorded planet wheels 16 and the sun wheel 15 , Radially inside are the freewheels 10 . 11 ( 6 ) forming clamping body 52 arranged. In the area of the axis of rotation of the gear / actuator unit 24 is the opening 63 for carrying out the cable, which is only partially shown 37 intended.

In addition to the planetary gear 12 is inside the case 64 continue the pulley damper 20 housed, the distributed over the circumference coil springs 65 has, in the circumferential direction effectively between mutually relatively limited rotatable components preferably of the web 17 are arranged.

8th shows a detail of the gear / actuator unit 24 of the 6 and 7 in the area of the switching mechanism 53 for the freewheels 10 . 11 , In the opening 63 is opposite the case 64 rotatable the cable 37 introduced, whose rope 56 from the second operating unit 28 ( 3 ) and the actuating this linear actuator 25 ( 3 ) is moved as needed and in the train basket 55 is mounted axially fixed. This is by means of the rolling bearing 66 rotatably coupled to the threaded connection 57 axially fixed. The threaded connection 57 is by means of the thread 67 with the inner star 48 rotatable and by means of the longitudinal toothing 68 rotatably and axially with the sprag cage 54 connected.

Pulls the operating unit 28 ( 3 ) on the rope 56 against the effect of the energy storage 47 , the train basket shifts 55 the threaded connection 57 axially, whereby a relative rotation of this at the thread 67 is enforced, over the spline 68 on the sprag cage 54 is transmitted. By the rotation of the sprag cage 54 become the clamp body 52 relatively in the circumferential direction with respect to the opposing clamping ramps 49 . 50 twisted. This will change the clamping properties between the inner star 48 and the sun wheel 15 belonging outer ring 51 so that the torsional ratios between the sun gear 15 and to the shaft part 58 , which in turn is rotatably connected to the crankshaft, set and the freewheels 10 . 11 be determined.

The 9 shows a detail of the gear / actuator unit 24 of the 6 and 7 in the area of the operating unit 27 , The rotary lever 31 is in the longitudinal slot 32 of the spindle 69 of the electric motor 59 driven spindle gear 60 axially displaced ram 26 taken up and in the thread-like connection 33 stored. This consists of the non-rotatable and axially relative to the housing 61 taken and against each other against the action of the energy store 70 axially displaceable supporting parts 62 . 62a at which the brake pads 30 are included. The brake pads 30 close the brake disc between them 29 the disc brake 14 one.

The rotary lever 31 has embossed ramps in the circumferential direction 72 on, by means of the rolling elements 71 in complementary ramps 73 the ramp parts 74 . 75 , the ramp device 76 form, take effect. The ramp part 75 is here by the rotary lever 31 performed axially and takes this rotatable. At the end of the ramp section 75 this is against the ramp part 74 and the support part 62a axially by means of the energy store 77 axially braced. The support part 62a overlaps the support part 62 so that it floats in the support part 62 under the effect of energy storage 70 . 77 is tense.

In an axial displacement of the plunger 26 from the position shown, the rotary lever twists 31 on the ramp part 75 and displaced by the ramp means 76 the support parts 62 . 62a so against each other and against the effect of energy storage 70 . 77 that the brake pads 30 be shifted against each other and finally a frictional engagement with the brake disc 29 form. The disc brake 14 is closed and the planetary gear 12 ( 6 ).

LIST OF REFERENCE NUMBERS

1

powertrain

2

Internal combustion engine

3

belt drive

4

friction clutch

5

transmission

6

drive wheel

7

starter generator

8th

crankshaft

9

rotor

10

freewheel

11

freewheel

12

planetary gear

13

ring gear

14

disc brake

15

sun

16

planet

17

web

18

accessory

19

air compressor

20

Pulley damper

21

motor housing

22

idler

23

belt

24

Gearbox / actuator unit

25

Linear Actuator

26

tappet

27

operating unit

28

operating unit

29

brake disc

30

brake pad

31

lever

32

longitudinal slot

33

thread-like connection

34

lever

35

actuating area

36

camp

37

cable

38

neutral position

39

limit

40

attack

41

game

42

arrow

43

arrow

44

arrow

45

attack

46

pulley

47

energy storage

48

inside star

49

clamping ramp

50

clamping ramp

51

outer ring

52

clamping bodies

53

switching mechanism

54

Clamping body cage

55

Zugkorb

56

rope

57

threaded connection

58

shaft part

59

electric motor

60

spindle gear

61

casing

62

supporting part

62a

supporting part

63

opening

64

casing

65

coil spring

66

roller bearing

67

thread

68

spline

69

spindle

70

energy storage

71

rolling elements

72

ramp

73

ramp

74

ramp portion

75

ramp portion

76

ramp means

77

energy storage

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 199417705 A1 [0002]
• DE 102004060991 A1 [0002]
• DE 102007021233 A1 [0002]

Claims (10)

Belt drive ( 3 ) of a drive train ( 1 ) of a motor vehicle with a transmission between a starter generator ( 7 ) and an internal combustion engine ( 2 ) switching planetary gear ( 12 ) with a housing fixed by means of a disc brake ( 14 ) connectable ring gear ( 13 ), one with a crankshaft ( 8th ) of the internal combustion engine ( 2 ) of the drive train ( 1 ) connected bridge ( 17 ) with circumferentially arranged planetary gears ( 16 ) and one with a rotor ( 9 ) of the starter generator ( 7 ) and at least one ancillary unit ( 18 ) rotatably connected sun gear ( 15 ) and two mutually switchable freewheels ( 10 . 11 ), a torque direction between rotor ( 9 ) and crankshaft ( 8th ), characterized in that the disc brake ( 14 ) from a first actuator unit ( 27 ) and the freewheels ( 10 . 11 ) from a second actuator unit ( 28 ) and the operating units ( 27 . 28 ) by means of a self-locking linear actuator ( 25 ) are operated alternately. Belt drive ( 3 ) according to claim 1, characterized in that the linear actuator ( 25 ) an electric motor ( 59 ) with spindle gear ( 60 ). Belt drive ( 3 ) according to claim 1 or 2, characterized in that the disc brake ( 14 ) from a brake disc ( 29 ) and two on both sides of this arranged, axially against each other by means of an energy store ( 70 ) biased by the linear actuator ( 25 ) against the brake disc ( 29 ) against the action of the energy store ( 70 ) bracing pads ( 30 ) is formed. Belt drive ( 3 ) according to one of claims 1 to 3, characterized in that the freewheels ( 10 . 11 ) by means of a cable ( 37 ) are switched by both freewheels ( 10 . 11 ) common clamping body ( 52 ) on opposite clamping ramps ( 49 . 50 ) by means of one of the cable ( 37 ), the clamping body ( 52 ) receiving sprag cage ( 54 ) are relocated. Belt drive ( 3 ) according to one of claims 1 to 4, characterized in that a plunger ( 26 ) of the linear actuator ( 25 ) against a neutral position ( 38 ) is axially displaceable in two directions of movement and in each one of the directions of movement an actuating unit ( 27 . 28 ) independently of the other actuator unit ( 28 . 27 ) is pressed. Belt drive ( 3 ) according to claim 5, characterized in that in the neutral position ( 38 ) the disc brake ( 14 ) and a preferred freewheel ( 10 ) is switched. Belt drive ( 3 ) according to claim 5 or 6, characterized in that the actuating units ( 27 . 28 ) from the ram ( 26 ) over in each case a partial path of the entire travel path of the plunger ( 26 ) and a partial path of an actuating unit ( 28 ) for the other actuator unit ( 27 ) by means of a stop ( 40 ) is limited. Belt drive ( 3 ) according to claim 7, characterized in that the brake pads ( 30 ) relocating rotary lever ( 31 ) of the first actuating unit ( 27 ) in a longitudinal slot ( 32 ) of the plunger ( 26 ) and over a partial path from a boundary ( 39 ) of the longitudinal slot ( 32 ) is taken. Belt drive ( 3 ) according to claim 7 or 8, characterized in that a housing fixed rotatably arranged lever ( 34 ) of the second actuator unit ( 28 ) of the plunger ( 26 ) is acted upon axially. Belt drive ( 3 ) according to claim 8 or 9, characterized in that the rotary lever ( 31 ) in the neutral position ( 38 ) of the plunger ( 26 ) and the lever ( 34 ) when the rotary lever ( 31 ) at the boundary ( 39 ) by means of one stop ( 40 . 45 ) are limited.

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