EP3421741A1 - Variable valve drive - Google Patents

Abstract

The invention relates to a variable valve train (10) for an internal combustion engine, comprising a camshaft (12), a gas exchange valve (18, 20) and a cam carrier (22). The cam carrier (22) is rotatably and axially displaceably arranged on the camshaft (12) and has a first cam (28) and a second cam (30). The variable valve train (10) has a power transmission device (16) with a force transmission element (40), in particular a drag lever or a rocker arm, which depending on an axial position of the cam carrier (22) optionally 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) produces. The variable valve train (10) has a first actuator (24) for axially displacing the cam carrier (22), wherein the first actuator (24) is at least partially received in the power transmission device (16).

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 trains allow flexible control of the valves to change the opening time, closing time and / or valve lift. As a result, the engine operation can be adapted, for example, to a specific load situation. For example, a variable valve train can be realized by a so-called sliding cam system.

From the DE 196 11 641 C1 is an example of such a sliding cam system is known, with which the operation of a gas exchange valve is made possible with several different lifting curves. For this purpose, a sliding cam with at least one, several cam tracks having cam portion rotatably but axially displaceably mounted on the camshaft having a Hubkontur, in which an actuator is introduced in the form of a pin from radially outside to produce an axial displacement of the sliding cam. Due to the axial displacement of the sliding cam, a different valve lift is set in the respective gas exchange valve. The sliding cam is characterized by the axial displacement thereof relative to the camshaft characterized in its axial relative position on the camshaft rastiert that depending on the axial relative position at least one spring-loaded detent ball which is received and stored in the camshaft engages in at least one locking groove.

The sliding cam system can take up a considerable amount of space. In particular, an arrangement of the actuators for moving 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 For example, an internal combustion engine having a plurality of cylinders, a cylinder head, and a cylinder head cover is known. For the actuation of gas exchange valves at least one rotatably mounted camshaft with at least one axially displaceable on the respective camshaft sliding cam is provided. The respective sliding cam has at least one slotted section with at least one groove. To effect a axial displacement of the respective sliding cam, an actuator is provided. The actuator is mounted in the cylinder head or in the cylinder head cover.

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

The object is achieved by a variable valve train according to the independent claim. Advantageous 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 rotatably and axially displaceably arranged on the camshaft 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 drag lever or rocker arm, which selectively produces an operative connection between the first cam and the gas exchange valve or between the second cam and the gas exchange valve depending on an axial position of the cam carrier. The variable valve train has a first actuator for axially displacing the cam carrier, wherein the first actuator is at least partially received in the power transmission device.

By receiving the first actuator in the already existing power transmission device less or no additional space is required for the first actuator. In addition, a drive for actuating the first actuator may be provided in the power transmission device.

In particular, the first cam and the second cam may be arranged adjacent to each other and / or have different cam contours.

For example, the different cam contours of the first cam and the second cam for consumption reduction, for thermal management or for the realization of an engine brake serve.

Preferably, the cam carrier and the first actuator may form a sliding cam system.

In a particularly preferred embodiment, the power 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 shaft pivotally support the power transmission element.

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

Preferably, the lever axle bearing block may support a lever shaft of the power transmission device pivotally supporting the power transmission element.

In a further embodiment, the first actuator is at least partially received in the power transmission element.

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

In one development, the first actuator has a retractable and retractable pin, which can be brought into engagement with a first, preferably helically extending about the longitudinal axis of the camshaft, engaging track for axial displacement of the camshaft. In engagement with the engagement track, the pin fixed relative to an axial direction of the camshaft can displace the cam carrier axially.

Preferably, the pin can be retracted and extended in a direction radial 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 via the control piston.

In one embodiment, the lifting device is arranged displaceably in a second cylinder of the first actuator. Thus, the lifting device can be displaced in a direction opposite to the cam carrier in particular in order to bring the pin of the actuator out of engagement with the engagement track.

In a preferred embodiment, an ejection ramp is arranged at one end of the first engagement track, which displaces 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, biases the lifting device in a direction to the first position. Thus, a movement of the lifting device takes place from the first position to the second position against the biasing force of the first elastic element.

In a further embodiment, the first actuator further includes a control fluid supply passage that is in fluid communication with a control fluid space of the lift device in the first position of the lift device. Alternatively or additionally, the first actuator has a Steuerfluidablasskanal which is in the second position of the lifting device in fluid communication with a control fluid space of the lifting device on. Thus, depending on the position (position) of the lifting device, a supply or a discharge of control fluid can be made.

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

In a preferred embodiment, the variable valve drive further comprises a second actuator for axially displacing the cam carrier. The second actuator is at least partially in the power transmission device, in particular a lever axis of the power transmission device, a lever axis bearing block of the power transmission device and / or the power transmission element of the power transmission device added. This can be achieved with the second actuator, the same space advantages as with the first actuator.

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

Preferably, the first actuator and the second actuator are formed separately from each other. However, it is also possible for the first actuator and the second actuator to form an integral actuator device in a common housing.

Preferably, the first actuator may displace the cam carrier from a first axial position to a second axial position, and the second actuator may displace the cam carrier from the second axial position to the first axial position.

In a further embodiment, the variable valve drive has a control fluid supply device for the first actuator and / or the second actuator. The control fluid supply means comprises a bearing block which rotatably supports the camshaft. The bearing block includes a first control fluid supply passage and a second control fluid supply passage disposed downstream of the first control fluid supply passage. The first control fluid supply channel and the second control fluid supply channel are selectively fluidly connectable in response to a rotational angle 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 chamber.

Preferably, the second control fluid supply channel may be located upstream of the control fluid space.

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

According to another aspect of the present application, the configuration of the first actuator and / or the second actuator disclosed herein is disclosed regardless of the arrangement thereof in the power transmission device. That is, the first actuator and / or the second actuator may not be disposed within the power transmission device. The first actuator and / or the second actuator may be embodied disclosed herein. Among other things, according to this aspect, the application solves the problem 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 will be described below with reference to the accompanying drawings. Show it:

FIG. 1

a perspective view of a variable valve train;

FIG. 2

a sectional view through the variable valve train; and

FIG. 3

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

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

The FIG. 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 may be intake valves or exhaust valves.

The variable valve train 10 may be used to adjust the valve timing curves of the first and second gas exchange valves 18, 20. The variable valve train 10 is associated with 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 lorry.

The camshaft 12 is arranged as overhead camshaft (OHC). The camshaft 12 may be part of a double overhead camshaft (DOHC) or may 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 rotatably and axially displaceably arranged on the camshaft 12. 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 timing curves. The different cam contours can be used, for example, to reduce consumption, for thermal management or for the realization of an engine brake.

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

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

For axially displacing the cam carrier 22, radially displaceable pins (pins) 36, 38 of the actuators 24, 26 can selectively engage (mesh in) the engagement tracks 32, 34. Specifically, the pin 36 of the first actuator 24 may selectively engage the first engagement track 32 for shifting 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 FIG. 1 the cam carrier 22 is shown in the first axial position. The pin 38 of the second actuator 26 in turn can selectively engage in the second engagement track 34. Then, the cam carrier 22 is displaced from the second axial position to the first axial position.

The axial displacement of the cam carrier 22 is triggered by the extended pin 36, 38 of the respective actuator 24, 26 with respect to an axial direction of the camshaft 12 is stationary. Consequently, due to the spiral shape of the engagement tracks 32, 34, the slidable cam carrier 22 is displaced in a longitudinal direction of the camshaft 12 when one of the extended pins 36 or 38 engages the respective engagement track 32, 34. At the end of the axial displacement operation, the extended pin 36 or 38 of the respective actuator 24, 26 is guided by the respective engagement track 32, 34 via an ejector 32A, 34A opposite to the extension direction and thus retracted. The pin 36, 38 of the respective actuator 24, 26 is disengaged from the respective engagement track 32, 34th

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

The sliding cam system 14 may additionally include a locking device (not shown). The locking device may be configured to axially secure the cam carrier 22 in the first axial position and the second axial position. For this purpose, the locking device, for example, have an elastically biased locking body. The blocking body can engage in a first recess of the cam carrier in the first axial position of the cam carrier 22 and engage in a second recess of the cam carrier 22 in the second axial position of the cam carrier 22. The locking device may be provided for example in the camshaft 12.

The power transmission device 16 includes a power transmission member 40, a lever shaft 42, and a plurality of lever axle bearing blocks 43 (only one lever axle bearing block shown schematically in FIG Fig. 1 shown) for supporting the lever axis 42. The power transmission element 40 is rotatably mounted on the lever axis 42.

In the embodiment shown, the power transmission element 40 is thus designed as a rocker arm and the lever axle 42 is thus designed as a rocker arm axle. However, it is also possible that the force transmission element 40 is formed for example as a drag lever.

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

In the first axial position of the cam carrier 22, the force transmission element 40 is operatively connected between the first cam 28 and the gas exchange valves 18 and 20 via the cam follower 44. The gas exchange valves 18 and 20 are operated according to the cam contour of the first cam 28. This situation is in FIG. 1 shown. In the second axial position of the cam carrier 22, the force transmission element 40 via the cam follower 44 in operative connection between the second cam 30 and the gas exchange valves 18 and 20. The gas exchange valves 18 and 20 are operated according to the cam contour of the second cam 30.

The first actuator 24 and the second actuator 26 are partially received in the lever shaft 42 (integrated). This is particularly advantageous from the point of view of optimal space utilization, since the actuators 24 and 26 thus require no or hardly any separate installation space. To achieve the same advantage, it is also possible to integrate the first actuator 24 and the second actuator 26 in the lever axis bearing blocks of the lever axis 42. As a further example, it is also possible to integrate the actuators 24 and 26 directly into the force transmission element 40 with a correspondingly large-sized power transmission element 40.

The FIG. 2 shows a section through the first actuator 24. The second actuator 26 may be formed as 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 channel 56.

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

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

At the end of the axial displacement of the cam carrier 22 (see FIG. 1 ), the pin 36 reaches the ejection lamp 32A. The ejection ramp 32A urges the pin 36 in a direction toward 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 along 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 as a whole against a biasing force (restoring force) of the first elastic member 48 within a second cylinder 64 of the actuator 24 is moved (retracted).

The first elastic element 48 may be for example a spiral spring. A space in which the first elastic member 48 is received may be substantially free of control fluid. When the lifting device 46 has retracted, a fluid connection between the control fluid channel 60 and a discharge channel 66 is established. The still prevailing increased pressure in the control fluid space 58 decreases. The control piston 52 is retracted by the force of the second elastic element 54 in the first cylinder 50. The pin 36 is no longer in contact with the first engagement track 32. The biasing force of the first elastic member 48 pushes the jack 46 back to the home position.

In FIG. 3 schematically shows how a control fluid supply to the actuators 24, 26 may be formed in response to a rotational angle of the camshaft 12. By means of the control fluid supply can be ensured, for example, that only within the base circle range of the cam 28, 30 is switched between the cam 28, 30 (an axial displacement of the cam carrier 22 is performed).

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 mounted in the bearing block 70 via a one-piece or multi-part bearing shell 76. The bearing shell 76 has passages, so that between the camshaft 12 and the bearing block 70 ring segment channels 78, 80 are formed. The camshaft 12 also has a transverse channel 82. The transverse channel 82 extends perpendicular to a longitudinal axis of the camshaft 12 and may be formed, for example, as a through-passage.

The first supply channel 72 is disposed upstream of the second supply channel 74. The first supply channel 72 is arranged downstream of a high-pressure chamber. The second supply channel 74 is disposed upstream of the supply channel 62. Depending on a rotational position of the camshaft 12, fluid communication is established between the first supply passage 72 and the second supply passage 74 via the ring segment passage 78, the cross passage 82 and the ring segment passage 80. In other words, the cross channel 82 selectively connects the supply passages 72 and 74 with each other depending on a rotational angle of the camshaft 12. In the example shown, the camshaft 12 rotates counterclockwise by 90 degrees (from 12 o'clock to 9 o'clock) in the example shown the fluid connection between the supply channels 72 and 74 remains during this rotation. On the other hand, during the subsequent 90 ° counterclockwise rotation of the camshaft (from 9 o'clock to 6 o'clock), there is no fluid communication between the supply passages 72 and 74. The supply passages 72 and 74 are not connected via the ring segment passages 78, 80 and the cross passage 82.

In the FIG. 3 shown configuration of the control fluid supply means 68 is purely schematically show how a camshaft angle-dependent control fluid supply can be realized. The practical implementation may, of course, differ in particular with regard to the illustrated angular ranges of the ring segment channels 78, 80.

The invention is not limited to the preferred embodiments described above. Rather, a variety of variants and modifications is possible, which also make use of the inventive idea and therefore fall within the scope. In particular, the invention also claims protection of the subject matter 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 actor

26

Second actor

28

First cam

30

Second cam

32

First intervention lane

32A

Ausschieberampe

34

Second intervention 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)

Variable valve train (10) for an internal combustion engine, comprising: a camshaft (12); a gas exchange valve (18, 20); a cam carrier (22) rotatably and axially slidable on the camshaft (12) and having a first cam (28) and a second cam (30); a power transmission device (16) with a power transmission element (40), in particular a drag lever or a rocker arm, depending on an axial position of the cam carrier (22) optionally 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) produces; and a first actuator (24) for axially displacing the cam carrier (22), wherein the first actuator (24) is at least partially received in the power transmission device (16). A variable valve train (10) according to claim 1, wherein: the power transmission device (16) has a lever axis (42), in particular a rocker arm axis or a rocker arm axis, and the first actuator (24) is at least partially received in the lever axis (42). A variable valve train (10) according to claim 1 or claim 2, wherein: the power transmission device (16) has a lever axle bearing block (43), and the first actuator (24) is at least partially received in the lever axle bearing block (43). A variable valve train (10) according to any one of claims 1 to 3, wherein:
the first actuator (24) is at least partially accommodated in the force transmission element (40). Variable valve train (10) according to one of the preceding claims, wherein: the first actuator (24) is actuated electromagnetically, pneumatically and / or hydraulically; and a control line (62) for actuating the first actuator (24) at least partially in the power transmission device (16), in particular the power transmission element (40), the lever axis (42) and / or the lever axis bearing block (43) is received. Variable valve train (10) according to one of the preceding claims, wherein the first actuator (24) comprises:
a retractable and retractable pin (36) engageable with a first engagement track (32) for axially displacing the camshaft (12), preferably spirally around the longitudinal axis of the camshaft (12). Variable valve train (10) according to one of the preceding claims, wherein the first actuator (24) comprises a, preferably hydraulic, lifting device (46) with a first cylinder (50) and a control piston (52) which is displaceable in the first cylinder (50). is arranged, wherein the control piston (52) is in operative connection or integrally formed with the pin (36). A variable valve train (10) according to claim 7, wherein:
the lifting device (46) is displaceably arranged in a second cylinder (64) of the first actuator (24). A variable valve train (10) according to claim 7 or claim 8, wherein:
at one end of the first engagement track (32) there is arranged an ejection ramp (32A) which, when the pin (36) is unclipped, lifts the lifting means (46) in the second cylinder (64) in a direction opposite the cam carrier (22) from a first one Move position to a second position. A variable valve train (10) according to claim 9, wherein a first elastic element (48), in particular a spring, biases the lifting device (46) in a direction to the first position. The variable valve train (10) of claim 9 or claim 10, wherein the first actuator (24) further comprises: a control fluid supply passage (62) in fluid communication with a control fluid space (58) of the lift (46) in the first position of the lift (46); and or a pilot fluid discharge passage (66) in fluid communication with a control fluid space (58) of the lift (46) in the second position of the lift (46). The variable valve train (10) of any of claims 7 to 11, wherein the first actuator (24) further comprises:
a second elastic element (54), in particular a spring, which biases the control piston (52) in a direction opposite to the cam carrier (22). A variable valve train (10) according to any one of the preceding claims, further comprising a second actuator (26) for axially displacing the cam carrier (22), wherein: the second actuator (26) at least partially in the power transmission device (16), in particular a lever axis (42) of the power transmission device (16), a lever axle bearing block (43) of the power transmission device (16) and / or the power transmission element (40) of the power transmission device (16) , recorded; and or the second actuator (26) as the first actuator (24) is formed. The variable valve train (10) according to one of the preceding claims, further comprising a control fluid supply device (68) for the first actuator (24) and / or the second actuator (26), comprising: a bearing block (70) rotatably supporting the camshaft (12) and having a first control fluid supply passage (72) and a second control fluid supply passage (74) located downstream of the first control fluid supply passage (72); wherein the first control fluid supply passage (72) and the second control fluid supply passage (74) are selectively fluidly operable in response to a rotational angle of the camshaft (12), in particular via a passage, preferably a transverse passage, of the camshaft (12). Motor vehicle, in particular commercial vehicle, with a variable valve train (10) according to one of the preceding claims.

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