EP3421741B1 - Variable valve drive - Google Patents

Description

The invention relates to a variable valve train for an internal combustion engine.

Valve-controlled internal combustion engines have one or more controllable intake and exhaust valves per cylinder. Variable valve drives enable flexible control of the valves to change the opening time, closing time and / or the valve lift. As a result, engine operation can be adapted to a specific load situation, for example. For example, a variable valve train can be implemented by a so-called sliding cam system.

From the DE 196 11 641 C1 and from the JP 5793070 B2 An example of such a sliding cam system is known, with which the actuation of a gas exchange valve with several different stroke curves is made possible. For this purpose, a sliding cam with at least one cam section having a plurality of cam tracks is rotatably but axially displaceably mounted on the camshaft and has a stroke contour into which an actuator in the form of a pin is inserted from the outside radially to produce an axial displacement of the sliding cam. Due to the axial displacement of the slide cam, a different valve lift is set for the respective gas exchange valve. After its axial displacement relative to the camshafts, the sliding cam is locked in its axial relative position on the camshaft in that, depending on the axial relative position, at least one spring-loaded locking ball, which is received and supported in the camshaft, engages in at least one locking groove.

The sliding cam system can take up a considerable amount of space. In particular, arranging the actuators to move a cam carrier (sliding cam) can be a challenge in tight spaces. Typically, the actuators are attached to a frame connected to the cylinder head or cylinder head cover. From the DE 10 2011 050 484 A1 an internal combustion engine with several cylinders, a cylinder head and a cylinder head cover is known. To actuate gas exchange valves, at least one rotatably mounted camshaft is provided with at least one sliding cam that is axially displaceable on the respective camshaft. The respective sliding cam has at least one link section with at least one groove. To effect one An actuator is provided for axial displacement of the respective sliding cam. The actuator is mounted in the cylinder head or in the cylinder head cover.

The invention is based on the object of providing an improved or alternative variable valve train with a sliding cam system which has an installation space-optimized structure.

The object is achieved by a variable valve train according to the independent claim. Advantageous further developments are specified in the dependent claims and the description.

The variable valve train for an internal combustion engine has a camshaft, a gas exchange valve and a cam carrier (sliding cam). The cam carrier is arranged on the camshaft in a rotationally fixed and axially displaceable manner and has a first cam and a second cam. The variable valve train has a power transmission device with a power transmission element, in particular a rocker arm or rocker arm, which, depending on an axial position of the cam carrier, optionally creates an operative connection between the first cam and the gas exchange valve or between the second cam and the gas exchange valve. The variable valve train has a first actuator for axially displacing the cam carrier, the first actuator being at least partially accommodated in the power transmission device.

By accommodating the first actuator in the power transmission device which is present anyway, less or no additional installation space is required for the first actuator. In addition, a control for actuating the first actuator can be provided in the power transmission device.

In particular, the first cam and the second cam can be arranged adjacent to one another and / or have different cam contours.

For example, the different cam contours of the first cam and the second cam can be used to reduce consumption, for thermal management or to implement an engine brake.

The cam carrier and the first actuator can preferably form a sliding cam system.

In a particularly preferred exemplary embodiment, the force transmission device has a lever axis, in particular a rocker arm axis or a rocker arm axis. The first actuator is at least partially received in the lever axis.

In particular, the rocker arm axis can pivotally support the power transmission element.

In a further exemplary embodiment, the force transmission device has a lever axle bearing block and the first actuator is at least partially received in the lever axle bearing block.

Preferably, the lever axis bearing block can support a lever axis of the force transmission device that pivotably supports the force transmission element.

In a further exemplary embodiment, the first actuator is at least partially accommodated in the force transmission element.

In one embodiment variant, the first actuator is actuated electromagnetically, pneumatically and / or hydraulically. Alternatively or additionally, a control line (for example an electrical, pneumatic and / or hydraulic control line) for actuating the first actuator is at least partially accommodated in the power transmission device (for example the power transmission element, the lever axle and / or the lever axle bearing block).

In a further development, the first actuator has a retractable and extendable pin which can be brought into engagement with a first engagement track, which preferably extends spirally around the longitudinal axis of the camshaft, for axially displacing the camshaft. In engagement with the engagement track, the pin that is stationary with respect to an axial direction of the camshaft can axially shift the cam carrier.

The pin can preferably be retracted and extended in a direction radially to a longitudinal axis of the camshaft.

In a further embodiment variant, the first actuator has a, preferably hydraulic, lifting device with a first cylinder and a control piston which is arranged displaceably in the first cylinder. The control piston is operatively connected or integrally formed with the pin. This allows the pin to be extended over the control piston.

In one embodiment, the lifting device is arranged displaceably in a second cylinder of the first actuator. The lifting device can thus be displaced in a direction opposite to the cam carrier, in particular, in order to disengage the pin of the actuator from the engagement track.

In a preferred embodiment, a push-out ramp is arranged at one end of the first engagement track, which pushes the lifting device in the second cylinder in a direction opposite to the cam carrier from a first position to a second position when the pin is removed.

In a further embodiment, a first elastic element, in particular a spring, prestresses the lifting device in a direction to the first position. The lifting device thus moves from the first position to the second position counter to the pretensioning force of the first elastic element.

In a further exemplary embodiment, the first actuator also has a control fluid supply channel which, in the first position of the lifting device, is in fluid communication with a control fluid chamber of the lifting device. Alternatively or additionally, the first actuator has a control fluid drainage channel, which in the second position of the lifting device is in fluid communication with a control fluid chamber of the lifting device. In this way, depending on the position (position) of the lifting device, control fluid can be supplied or drained.

In a further embodiment variant, the first actuator has a second elastic element, in particular a spring, which prestresses the control piston in a direction opposite to the cam carrier.

In a preferred embodiment variant, the variable valve train also has a second actuator for axially displacing the cam carrier. The second actuator is at least partially accommodated in the power transmission device, in particular a lever axle of the power transmission device, a lever axle bearing block of the power transmission device and / or the power transmission element of the power transmission device. In this way, the same installation space advantages as with the first actuator can be achieved with the second actuator.

In particular, the second actuator can be designed like the first actuator.

The first actuator and the second actuator are preferably formed separately from one another. However, it is also possible for the first actuator and the second actuator to form an integral actuator device in a common housing.

The first actuator can preferably move the cam carrier from a first axial position to a second axial position and the second actuator can move the cam carrier from the second axial position to the first axial position.

In a further embodiment, the variable valve train has a control fluid supply device for the first actuator and / or the second actuator. The control fluid supply device has a bearing block that rotatably supports the camshaft. The bearing block has a first control fluid supply channel and a second control fluid supply channel, which is arranged downstream of the first control fluid supply channel. The first control fluid supply channel and the second control fluid supply channel can be brought into fluid communication selectively depending on an angle of rotation of the camshaft, in particular via a channel, preferably a transverse channel, of the camshaft.

In particular, the first control fluid supply channel can be arranged downstream of a high-pressure space.

The second control fluid supply channel can preferably be arranged upstream of the control fluid space.

The invention further relates to a motor vehicle, in particular a commercial vehicle (for example a bus or lorry), with a variable valve train as disclosed herein.

According to a further aspect of the present application, the configuration of the first actuator and / or of the second actuator disclosed herein is disclosed independently of the arrangement thereof in the power transmission device. That is, the first actuator and / or the second actuator can also not be arranged within the power transmission device. The first actuator and / or the second actuator can be embodied as disclosed herein. According to this aspect, the application solves, among other things, the task of providing an alternative and / or improved hydraulic actuator for a sliding cam system.

Figur 1

eine perspektivische Ansicht eines variablen Ventiltriebs;

Figur 2

eine Schnittansicht durch den variablen Ventiltrieb; und

Figur 3

eine schematische Schnittansicht durch eine Nockenwelle und einen Lagerbock.

The preferred embodiments and features of the invention described above can be combined with one another as desired. Further details and advantages of the invention are described below with reference to the accompanying drawings. Show it:

Figure 1

a perspective view of a variable valve train;

Figure 2

a sectional view through the variable valve train; and

Figure 3

is a schematic sectional view through a camshaft and a bearing block.

The embodiments shown in the figures correspond at least partially, so that similar or identical parts are provided with the same reference numerals and for their explanation reference is also made to the description of the other embodiments or figures in order to avoid repetitions.

The Figure 1 shows a variable valve train 10. The variable valve train 10 has a camshaft 12, a sliding cam system 14, a power transmission device 16, a first gas exchange valve 18 and a second gas exchange valve 20. The gas exchange valves 18, 20 can be intake valves or exhaust valves.

The variable valve train 10 can be used to adjust the valve control curves of the first and second gas exchange valves 18, 20. The variable valve train 10 is assigned to an internal combustion engine (not shown). The internal combustion engine can be included, for example, in a commercial vehicle, for example a bus or a truck.

The camshaft 12 is arranged as an overhead camshaft (OHC). The camshaft 12 can be part of a double overhead camshaft system (DOHC) or can be provided as a single overhead camshaft (SOHC).

The sliding cam system 14 has a cam carrier 22, a first actuator 24 and a second actuator 26.

The cam carrier 22 is arranged on the camshaft 12 in a rotationally fixed and axially displaceable manner. The cam carrier 22 has a first cam 28, a second cam 30, a first engagement track (shift gate) 32 and a second engagement track (shift gate) 34.

The first cam 28 and the second cam 30 have different cam contours for generating different valve control curves. The different cam contours can be used, for example, to reduce consumption, for thermal management or to implement an engine brake.

The first cam 28 and the second cam 30 are arranged offset to one another along the longitudinal axis of the camshaft 12. Specifically, the first cam 28 and the second cam 30 are arranged adjacent to one another in a central section of the cam carrier 22. In other embodiments, additional cams and / or alternative arrangements of the cams can be provided. For example, a rocker arm can be assigned to each gas exchange valve, to which at least two cams of the cam carrier are assigned. It is also possible for a cam carrier to carry the cams for gas exchange valves from two adjacent cylinders.

The first engagement track 32 is provided in a first end region of the cam carrier 22. The second engagement track 34 is provided in an opposite second end region of the cam carrier 22. The first and second engagement tracks 32, 34 extend spirally as depressions (grooves) in the cam carrier 22 about a longitudinal axis of the camshaft 12. In other embodiments, at least one of the engagement tracks cannot be arranged on an axial end region of the cam carrier. For example. an engagement track can be arranged between two cams of the cam carrier.

For the axial displacement of the cam carrier 22, radially displaceable pins 36, 38 of the actuators 24, 26 can selectively engage (engage) in the engagement tracks 32, 34. Specifically, the pin 36 of the first actuator 24 can selectively engage the first engagement track 32 to move the cam carrier 22 from a first axial position to a second axial position. The pin 36 is moved radially with respect to a longitudinal axis of the camshaft 12. In the Figure 1 cam carrier 22 is shown in the first axial position. The pin 38 of the second actuator 26 can in turn selectively engage the second engagement track 34. Then the cam carrier 22 is shifted from the second axial position to the first axial position.

The axial displacement of the cam carrier 22 is triggered in that the extended pin 36, 38 of the respective actuator 24, 26 is stationary with respect to an axial direction of the camshaft 12. As a result, the displaceable cam carrier 22 is displaced in a longitudinal direction of the camshaft 12 due to the spiral shape of the engagement tracks 32, 34 when one of the extended pins 36 or 38 engages in the respective engagement track 32, 34. At the end of the axial displacement process, the extended pin 36 or 38 of the respective actuator 24, 26 is guided from the respective engagement track 32, 34 via a push-out ramp 32A, 34A opposite to the extension direction and thus retracted. The pin 36, 38 of the respective actuator 24, 26 comes out of engagement with the respective engagement track 32, 34.

The actuators 24, 26 can be actuated electromagnetically, pneumatically and / or hydraulically. A particularly preferred exemplary embodiment of the actuators 24, 26 with hydraulic actuation is described herein with reference to FIG Figures 2 and 3 described later.

The sliding cam system 14 can additionally have a locking device (not shown). The locking device can be designed such that it axially secures the cam carrier 22 in the first axial position and the second axial position. For this purpose, the locking device can have, for example, an elastically prestressed locking body. The locking body can engage in the first axial position of the cam carrier 22 in a first recess of the cam carrier and in the second axial position of the cam carrier 22 engage in a second recess of the cam carrier 22. The locking device can be provided, for example, in the camshaft 12.

The force transmission device 16 has a force transmission element 40, a lever axis 42 and a plurality of lever axis bearing blocks 43 (only one lever axis bearing block schematically in FIG Fig. 1 shown) for mounting the lever axis 42. The power transmission element 40 is rotatably arranged on the lever axis 42.

In the embodiment shown, the force transmission element 40 is designed as a rocker arm and the lever axis 42 is thus designed as a rocker arm axis. However, it is also possible for the force transmission element 40 to be designed, for example, as a rocker arm.

The power transmission element 40 has a cam follower 44, for example in the form of a rotatably mounted roller. Depending on an axial position of the cam carrier 22, the cam follower 44 follows a cam contour of the first cam 28 or the second cam 30.

In the first axial position of the cam carrier 22, the force transmission element 40 is operatively connected via the cam follower 44 between the first cam 28 and the gas exchange valves 18 and 20. The gas exchange valves 18 and 20 are actuated in accordance with the cam contour of the first cam 28. This situation is in Figure 1 shown. In the second axial position of the cam carrier 22, the force transmission element 40 is operatively connected via the cam follower 44 between the second cam 30 and the gas exchange valves 18 and 20. The gas exchange valves 18 and 20 are actuated in accordance with the cam contour of the second cam 30.

The first actuator 24 and the second actuator 26 are partially received (integrated) in the lever axis 42. This is particularly advantageous from the point of view of an optimal use of space, since the actuators 24 and 26 thus require little or no separate space. To achieve the same advantage, it is also possible to integrate the first actuator 24 and the second actuator 26 in the lever axle bearing blocks of the lever axle 42. As a further example, there is also the possibility of integrating the actuators 24 and 26 directly into the force transmission element 40 if the force transmission element 40 is of correspondingly large dimensions.

The Figure 2 shows a section through the first actuator 24. The second actuator 26 can be designed like the first actuator 24. The first actuator 24 has the pin 36, a hydraulic lifting device 46 and a first elastic element 48.

The hydraulic lifting device 46 has a first cylinder 50, a control piston 52, a second elastic element 54 and a ventilation duct 56.

The control piston 52 is arranged in a longitudinally displaceable manner in a control fluid chamber 58 of the first cylinder 50. The control piston 52 is formed integrally with the pin 36. However, it is also possible, for example, for the pin to be operatively connected to the control piston of the lifting device.

The control fluid chamber 58 can be filled with a control fluid via a control fluid channel 60. Is a displacement of the cam carrier 22 (see Figure 1 ) from the first axial position to the second axial position, the control fluid chamber 58 is filled with additional control fluid. In detail, the control fluid arrives from a supply channel 62 via the control fluid channel 60 into the control fluid space 58. The supply channel 62 is at least partially received in the lever axis 42 as part of a control line for actuating the first actuator 24. The pressure in the control fluid chamber 58 increases due to the supply of control fluid. The control piston 52 and thus the pin 36 move in the first cylinder 50 in a direction towards the camshaft 12 for engagement (engagement) in the first engagement track 32, as in FIG Figure 2 is shown. The control piston 52 moves against a biasing force (restoring force) of the second elastic element 54. The second elastic element 54 can be a spiral spring, for example. Leakage fluid coming from the control fluid space 58 has penetrated into the annular space of the second elastic element 54, can be discharged via the ventilation duct 56.

At the end of the axial displacement of the cam carrier 22 (see Figure 1 ) pin 36 reaches push-out ramp 32A. The push-out ramp 32A pushes the pin 36 in a direction towards the control fluid space 58. The high pressure in the control fluid space 58 prevents the pin 36 from entering the control fluid space 58 together with the control piston 52. The pin 36 and the control piston 52 do not enter the first cylinder 50. Instead, the lifting device 46 is moved (retracted) as a whole against a biasing force (restoring force) of the first elastic element 48 within a second cylinder 64 of the actuator 24.

The first elastic element 48 can be a spiral spring, for example. A space in which the first elastic element 48 is accommodated can be substantially free of control fluid. If the lifting device 46 is retracted, a fluid connection is established between the control fluid channel 60 and an outlet channel 66. The still prevailing increased pressure in the control fluid chamber 58 decreases. The control piston 52 is moved into the first cylinder 50 by the force of the second elastic element 54. The pin 36 is no longer in contact with the first engagement track 32. The biasing force of the first elastic element 48 pushes the lifting device 46 back into the starting position.

In Figure 3 is shown schematically how a control fluid supply to the actuators 24, 26 can be designed as a function of an angle of rotation of the camshaft 12. The control fluid supply can be used, for example, to ensure that the cams 28, 30 are only switched between the cams 28, 30 within the base circle region (the cam carrier 22 is axially displaced).

A control fluid supply device 68 is integrated in a bearing block 70 and the camshaft 12. The bearing block 70 has a first supply channel 72 and a second supply channel 74. The camshaft 12 is supported in the bearing block 70 via a one-piece or multi-piece bearing shell 76. The bearing shell 76 has passages, so that ring segment channels 78, 80 are formed between the camshaft 12 and the bearing block 70. The camshaft 12 also has a transverse channel 82. The transverse channel 82 extends perpendicular to a longitudinal axis of the camshaft 12 and can be designed, for example, as a through channel.

The first supply channel 72 is arranged upstream of the second supply channel 74. The first supply channel 72 is arranged downstream of a high-pressure space. The second supply channel 74 is arranged upstream of the supply channel 62. Depending on a rotational position of the camshaft 12, a fluid connection is established between the first supply channel 72 and the second supply channel 74 via the ring segment channel 78, the transverse channel 82 and the ring segment channel 80. In other words, the transverse channel 82 selectively connects the supply channels 72 and 74 to one another depending on an angle of rotation of the camshaft 12. In the example shown, the camshaft 12 rotates, for example, 90 ° counterclockwise (from 12 noon to 9 am) the fluid connection between the supply channels 72 and 74 remains during this rotation. In contrast, during the subsequent 90 ° rotation of the camshaft counterclockwise (from 9 a.m. to 6 a.m.) there is no fluid connection between the supply channels 72 and 74. The supply channels 72 and 74 are not connected via the ring segment channels 78, 80 and the transverse channel 82.

In the Figure 3 The configuration of the control fluid supply device 68 shown is intended to show purely schematically how a cam fluid angle-dependent control fluid supply can be implemented. The practical implementation can of course differ in particular with respect to the angular ranges of the ring segment channels 78, 80 shown.

The invention is not restricted to the preferred exemplary embodiments described above. Rather, a large number of variants and modifications are possible which also make use of the inventive idea and therefore fall within the scope of protection. In particular, the invention also claims protection for the subject and the features of the subclaims independently of the claims referred to.

LIST OF REFERENCE NUMBERS

10

Variable valve train

12

camshaft

14

Sliding cam system

16

Power transmission device

18

First gas exchange valve

20

Second gas exchange valve

22

cam support

24

First actuator

26

Second actuator

28

First cam

30

Second cam

32

First engagement trace

32A

Ausschieberampe

34

Second engagement lane

34A

Ausschieberampe

36

Pin

38

Pin

40

Power transmission element (rocker arm)

42

lever axis

43

Lever shaft bearing block

44

cam follower

46

lifting device

48

First elastic element

50

First cylinder

52

spool

54

Second elastic element

56

vent channel

58

Control fluid space

60

Control fluid passage

62

feed channel

64

Second cylinder

66

drain channel

68

Control fluid supply device

70

bearing block

72

First supply channel

74

Second supply channel

76

bearing shell

78

First ring segment channel

80

Second ring segment channel

82

Querkanal

Claims (15)

1. A variable valve drive (10) for an internal combustion engine, having:

   a camshaft (12);

   a gas exchange valve (18, 20);

   a cam carrier (22) which is arranged axially displaceably and fixedly on the camshaft (12) so as to rotate with it, and has a first cam (28) and a second cam (30) ;

   a force transmission apparatus (16) with a force transmission element (40), in particular a drag lever or a rocker arm, which selectively establishes an operative connection between the first cam (28) and the gas exchange valve (18, 20) or between the second cam (30) and the gas exchange valve (18, 20) in a manner which is dependent on an axial position of the cam carrier (22); characterized by

   a first actuator (24) for the axial displacement of the cam carrier (22), the first actuator (24) being received at least partially in the force transmission apparatus (16).
2. The variable valve drive (10) according to Claim 1:

   the force transmission apparatus (16) having a lever axle (42), in particular a rocker arm axle or a drag lever axle, and

   the first actuator (24) being received at least partially in the lever axle (42).
3. The variable valve drive (10) according to Claim 1 or Claim 2:

   the force transmission apparatus (16) having a lever axle bearing block (43), and

   the first actuator (24) being received at least partially in the lever axle bearing block (43).
4. The variable valve drive (10) according to one of Claims 1 to 3:
   the first actuator (24) being received at least partially in the force transmission element (40).
5. The variable valve drive (10) according to one of the preceding claims:

   the first actuator (24) being actuated electromagnetically, pneumatically and/or hydraulically; and

   an actuating line (62) for the actuation of the first actuator (24) being received at least partially in the force transmission apparatus (16), in particular the force transmission element (40), the lever axle (42) and/or the lever axle bearing block (43).
6. The variable valve drive (10) according to one of the preceding claims, the first actuator (24) having:
   a retractable and extendible pin (36) which can be brought into engagement with a first engagement track (32) which preferably extends spirally around the longitudinal axis of the camshaft (12) for the axial displacement of the camshaft (12).
7. The variable valve drive (10) according to one of the preceding claims, the first actuator (24) having a lifting device (46) which is preferably hydraulic with a first cylinder (50) and a control piston (52) which is arranged displaceably in the first cylinder (50), the control piston (52) being operatively connected to or configured integrally with the pin (36).
8. The variable valve drive (10) according to Claim 7:
   the lifting device (46) being arranged displaceably in a second cylinder (64) of the first actuator (24).
9. The variable valve drive (10) according to Claim 7 or Claim 8:
   a slide-out ramp (32A) being arranged at one end of the first engagement track (32), which slide-out ramp (32A), during the decoupling of the pin (36), displaces the lifting device (46) from a first position to a second position in the second cylinder (64) in a direction which is opposed to the cam carrier (22).
10. The variable valve drive (10) according to Claim 9, a first elastic element (48), in particular a spring, prestressing the lifting device (46) in a direction towards the first position.
11. The variable valve drive (10) according to Claim 9 or Claim 10, the first actuator (24) having, furthermore:

    a control fluid feed duct (62) which is connected fluidically to a control fluid space (58) of the lifting device (46) in the first position of the lifting device (46); and/or

    a control fluid discharge duct (66) which is connected fluidically to a control fluid space (58) of the lifting device (46) in the second position of the lifting device (46).
12. The variable valve drive (10) according to one of Claims 7 to 11, the first actuator (24) having, furthermore:
    a second elastic element (54), in particular a spring, which prestresses the control piston (52) in a direction opposed to the cam carrier (22).
13. The variable valve drive (10) according to one of the preceding claims, having, furthermore, a second actuator (26) for the axial displacement of the cam carrier (22):

    the second actuator (26) being received at least partially in the force transmission apparatus (16), in particular a lever axle (42) of the force transmission apparatus (16), a lever axle bearing block (43) of the force transmission apparatus (16) and/or the force transmission element (40) of the force transmission apparatus (16); and/or

    the second actuator (26) being configured like the first actuator (24).
14. The variable valve drive (10) according to one of the preceding claims, having, furthermore, a control fluid supply device (68) for the first actuator (24) and/or the second actuator (26), having:

    a bearing block (70) which mounts the camshaft (12) rotatably; and has a first control fluid supply duct (72) and a second control fluid supply duct (74) which is arranged downstream of the first control fluid supply duct (72),

    it being possible for the first control fluid supply duct (72) and the second control fluid supply duct (74) to be selectively connected fluidically in a manner which is dependent on a rotary angle of the camshaft (12), in particular via a duct, preferably a transverse duct, of the camshaft (12).
15. A motor vehicle, in particular a commercial vehicle, having a variable valve drive (10) according to one of the preceding claims.

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