VALVE TRAIN FOR AN INTERNAL COMBUSTION ENGINE

Abstract

A valve train for an internal combustion engine may include a camshaft and a cam follower. The valve train may also include two first cams arranged on the camshaft in a torque-proof manner and at an axial distance from one another. Each of the two first cams may include an identical first cam contour. The valve train may also include two second cams arranged on the camshaft in a torque-proof manner and at an axial distance from one another. Each of the two second cams may also include an identical second cam contour. The two first cams and the two second cams may alternate in an axial direction on the camshaft. The cam follower may be axially adjustable between a first and second position, and may be drivingly connected to the two first cams in the first position and drivingly connected to the two second cams in the second position.

Claims

1. A valve train for an internal combustion engine, comprising: a camshaft and a cam follower; two first cams arranged on the camshaft in a torque-proof manner and at an axial distance from one another, each of the two first cams including an identical first cam contour; and two second cams arranged on the camshaft in a torque-proof manner and at an axial distance from one another, each of the two second cams including an identical second cam contour; wherein the two first cams and the two second cams alternate in an axial direction on the camshaft; wherein the cam follower is axially adjustable between a first position and a second position, the cam follower being drivingly connected to the two first cams in the first position, and drivingly connected to the two second cams in the second position; and wherein the cam follower includes a mechanical adjustment device configured to interact with the camshaft to axially adjust the cam follower between the first position and the second position.

2. The valve train according to claim 1, wherein: the cam follower includes a first cam follower roller and a second cam follower roller arranged at an axial distance from one another; and wherein the cam follower rollers are coupled to the two first cams in the first position and coupled to the two second cams in the second position.

3. The valve train according to claim 2, wherein: one of the cam follower rollers is drivingly connected to one of the two first cams when the cam follower is in the first position; and one of the cam follower rollers is drivingly connected to one of the two second cams when the cam follower is in the second position.

4. The valve train according to claim 2, wherein the axial distance between the two cam follower rollers, the axial distance between the two first cams and the axial distance between the two second cams are the same.

5. The valve train according to claim 2, further comprising at least two third cams arranged on the camshaft in a torque-proof manner and at an axial distance from one another, each of the at least two third cams including an identical third cam contour, wherein the cam follower includes a third cam follower roller.

6. The valve train according to claim 1, wherein: the camshaft includes a first slide guide and a second slide guide; the mechanical adjustment device includes an adjustable first mechanical engagement element configured to interact with the first slide guide when axially adjusting the cam follower from the first position to the second position; and the mechanical adjustment device includes an adjustable second mechanical engagement element configured to interact with the second slide guide when axially adjusting the cam follower from the second position to the first position.

7. The valve train according to claim 6, wherein the first slide guide and the second slide guide are axially adjustable relative to the camshaft, and are coupled mechanically to the cam follower via a coupling, and wherein an axial movement of the first slide guide and the second slide guide is accompanied by an axial movement of the cam follower.

8. The valve train according to claim 6, wherein the first slide guide and the second slide guide are outer circumferential grooves arranged on a sleeve, the sleeve arranged on the camshaft in an axially displaceable manner.

9. The valve train according to claim 8, wherein the coupling engages a recess provided on the sleeve.

10. The valve train according to claim 7, wherein the coupling is constructed in a bolt-like or pin-like manner and projects radially outwards from the cam follower.

11. The valve train according to claim 8, further comprising a projection extending radially outwards from an outer circumferential side of the sleeve and configured to engage a recess.

12. The valve train according to claim 11, wherein the projection is a bead extending around the sleeve in a circumferential direction.

13. The valve train according to claim 6, wherein at least one of: the mechanical adjustment device includes a first actuator configured to adjust the first mechanical engagement element between a first position and a second position, the first mechanical engagement element configured to engage the first slide guide when in the first position and not engage the first slide guide when in the second position; and the mechanical adjustment device includes a second actuator, the second actuator configured to adjust the second mechanical engagement element between a first position and a second position, the second mechanical engagement element configured to engage the second slide guide when in the first position and not engage the second slide guide when in the second position.

14. The valve train according to claim 13, wherein the first actuator and the second actuator are linearly adjustable, electrically driven actuators controlled by an electronic control device.

15. The valve train according to claim 13, wherein: the first actuator includes a linearly adjustable first positioning element, the first positioning element including a face side configured to contact a face side of the first mechanical engagement element lying opposite the first positioning element when the first mechanical engagement element is in the first position; and the second actuator includes a linearly adjustable second positioning element, the second positioning element including a face side configured to contact a face side of the second mechanical engagement element lying opposite the second positioning element when the second mechanical engagement element is in the first position.

16. The valve train according to claim 13, wherein: the cam follower includes at least one engagement element fixing device configured to detachably fix at least one of the first mechanical engagement element and the second mechanical engagement element in the respective first position and the respective second position; and wherein the engagement element fixing device includes a spring-loaded fixing element corresponding to one of the first mechanical engagement element and the second mechanical engagement element, the spring-loaded fixing element received by a first mount provided on the corresponding engagement element when the corresponding engagement element is in the respective first position, and received by a second mount provided on the cam follower when the corresponding engagement element is in the respective second position.

17. The valve train according to claim 16, wherein: at least one of the first mechanical engagement element and the second mechanical engagement element includes a base body constructed in one of a bolt-like manner and a pin-like manner; the first mount is a circumferential groove arranged on a circumferential side of the base body; and the second mount is circumferential groove arranged at an axial distance from the first mount.

18. The valve train according to claim 1, wherein the mechanical adjustment device does not include at least one of hydraulic components and pneumatic components.

19. An internal combustion engine, comprising a valve train, the valve train including: a camshaft and a cam follower; two first cams arranged on the camshaft in a torque-proof manner and at an axial distance from one another, each of the two first cams including an identical first cam contour; and two second cams arranged on the camshaft in a torque-proof manner and at an axial distance from one another, each of the two second cams including an identical second cam contour; wherein the two first cams and the two second cams alternate in an axial direction on the camshaft; wherein the cam follower is axially adjustable between a first position and a second position, the cam follower being drivingly connected to the two first cams in the first position, and drivingly connected to the two second cams in the second position; and wherein the cam follower includes a mechanical adjustment device configured to interact with the camshaft, the mechanical adjustment device facilitating the axial adjustment of the cam follower between the first position and the second position.

20. An internal combustion engine according to claim 19, wherein the mechanical adjustment device does not include at least one of hydraulic components and pneumatic components.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] There are shown, respectively diagrammatically:

[0036] FIG. 1 an example of a valve train according to the invention, with a camshaft,

[0037] FIG. 2 a variant of the example of FIG. 1, slide guides adjustable axially relative to the camshaft.

[0038] FIG. 3 an alternative variant of the example of FIG. 2.

DETAILED DESCRIPTION

[0039] FIG. 1 illustrates in a diagrammatic illustration an example of a valve train 1 according to the invention. The valve train 1 comprises a camshaft 2 and a cam follower. On the camshaft 2, two first cams 4a are arranged, in a torque-proof manner and axially at a distance from one another, which have an identical first cam contour 17a. On the camshaft 2 furthermore, two second cams 4b are arranged, in a torque-proof manner and axially at a distance from one another, which have an identical first cam contour 17b. As FIG. 1 clearly shows, the two first cams 4a and the two second cams 4b alternate along the axial direction A of the camshaft 2.

[0040] The cam follower 3 is adjustable along an axial direction A between a first position, in which it is drivingly connected to the two first cams 4a, and a second position, in which it is drivingly connected to the two second cams 4b. FIG. 1 shows the cam follower 3 here in the first position.

[0041] The cam follower 3 can have a cylindrically constructed cam follower base body 5, on the circumferential side 34 of which at a distance from one another a first and a second cam follower roller 6, respectively constructed in a hollow-cylindrical manner, are rotatably mounted. The two cam follower rollers 6 are arranged at the same axial distance from one another as the two first cams 4a with respect to one another and as the two second cams 4b with respect to one another.

[0042] The cam follower base body 5 is also known to the relevant specialist in the art under the designation “bolt” or “displacement axis”. Via the cam follower rollers 6, the drive connection or respectively mechanical coupling of the two first cams 4a with the two cam follower rollers 6 of the cam follower 3 takes place when the latter is connected in the first position. In the second position, the two cam follower rollers 6 are drivingly connected or respectively mechanically coupled with the two second cams 4b. In both cases, the rotational movement of the camshaft 2 is converted by means of the first or respectively second cams 4a, 4b into a linear movement of the cam follower 3.

[0043] In the first position of the cam follower 3, shown in FIG. 1, the two cam follower rollers 6 are therefore coupled to the first cam 4a, but not to the second cam 4b. The cam follower rollers 6 actuate via a suitably constructed mechanical coupling device (not illustrated in further detail in FIG. 1), in particular in the manner of an actuator, a valve for adjusting between an open and a closed state.

[0044] The cam follower 3 of FIG. 1 has a mechanical adjustment device 7, interacting with the camshaft 2, for the axial adjustment of the cam follower 3 between the first and the second position. The mechanical adjustment device 7 comprises, for this, a first adjustable mechanical engagement element 8a. The first mechanical engagement element 8a interacts, for the axial adjustment of the cam follower 3 from the first position shown in FIG. 1 into the second position, with a first slide guide 9a present on the camshaft 3. In an analogous manner, the mechanical adjustment device 7 has an adjustable second mechanical engagement element 8b. The second engagement element 8b interacts, for the axial adjustment of the cam follower 3 from its second position into the first position, with a second slide guide 9b present on the camshaft 3.

[0045] The mechanical adjustment device 7 further comprises a first actuator 10a, by means of which the first engagement element 8a is adjustable between a first position, shown in FIG. 1, in which it engages into the first slide guide 9a, and a second position, not shown in the figures, in which it does not engage into the first slide guide 9a. The mechanical adjustment device 7 also comprises a second actuator 10b, by means of which the second engagement element 8b is adjustable between a first position, in which it engages into the second slide guide 9b, and a second position, in which it does not engage into said second slide guide 9b. The mechanical adjustment device 7 does not comprise any hydraulic or pneumatic components.

[0046] The first actuator 10a is adjustable between an inactive position and an active position. For this purpose, the two actuators 10a, 10b can be constructed as linearly adjustable, electrically driven actuators. The mechanical adjustment device 7 is realized in this case as an electromechanical adjustment device. In other words, electrically driven actuators 10a, 10b are included here by the term “mechanical adjustment device” 7.

[0047] The two actuators 10a, 10b are controllable by a control device 11 of the valve train 1 for adjusting between their active position and their inactive position. This adjustability is realized in such a way that the first actuator 10a in the inactive position is out of contact with the first engagement element 8a. During an adjusting from its inactive position into its active position, the first actuator 10a adjusts the first engagement element 8a through mechanical contact form its second position into its first position.

[0048] The adjustment of the first engagement element 8a from the first into the second position can preferably be brought about by means of the stroke movement of the cam follower 3, in particular by means of the cam follower base body 5. Here, the cam follower 3 is moved by the stroke movement, brought about by the first or second cam 4a, 4b, in the direction of the first actuator 10a. If the latter is situated in its active position, then through the stroke movement of the cam follower 3 and therefore of the first engagement element 8a, the latter is pressed against the first actuator 10a and is adjusted by the latter into its second position. In this state, the first engagement element 8a engages into the first slide guide 9a, so that the cam follower 3, owing to the rotational movement of the camshaft 2, is moved by means of the first slide guide 9a, arranged thereon, axially from its first position into the second position. The second actuator 10b is also adjustable between an inactive position and an active position. This adjustability is realized in such a way that the second actuator 10b in the inactive position is out of contact with the second engagement element 8b. During an adjustment from its inactive position into its active position, the second actuator 10b adjusts the second engagement element 8b, through mechanical contact, from its second position into its first position.

[0049] The adjustment of the second engagement element 8b from the first position into the second position is preferably also brought about by means of the stroke movement of the cam follower 3, in particular by means of the cam follower base body 5. Here, the cam follower 3 is moved by the stroke movement, brought about by the first or second cam 4a, 4b, in the direction of the second actuator 8b. When the latter is situated in its active position, then through the stroke movement of the cam follower 3 and therefore of the second engagement element 8b, the latter is pressed against the second actuator 10b and is therefore adjusted by the latter into its second position.

[0050] In this state, the second engagement element 8b engages into the second slide guide 9b, so that the cam follower 3, owing to the rotational movement of the camshaft 2, is moved by means of the second slide guide 9a, arranged thereon, axially from its second position into the first position.

[0051] The first actuator 10a has a linearly adjustable (cf. arrow 15a) first positioning element 12a. The latter can project partially from a first housing 16a of the first actuator 10a and be arranged in a linearly adjustable manner relative thereto. A face side 13a of the first positioning element 12a, facing the first engagement element 8a, which first positioning element can be contrusted in a pin- or bolt-like manner, presses on moving of the first engagement element 8a into the first slide guide 9a against a face side 14a of the first engagement element 8a lying opposite the first positioning element 12a. The second actuator 10b has a linearly adjustable (cf. arrow 15b) second positioning element 12b. The latter can project partially from a second housing 16b of the second actuator 10b and be arranged in a linearly adjustable manner relative thereto. A face side 13b of the second positioning element 12b, facing the second engagement element 8b, which second positioning element can be constructed in a pin- or bolt-like manner, presses on moving of the second engagement element 8b into the second slide guide 9b against a face side 14b of the second engagement element 8b lying opposite the second positioning element 12b.

[0052] As FIG. 1 clearly shows, the cam follower 3 has for the two engagement elements 8a, 8b, preferably for both engagement elements 8a, 8b, respectively a first or respectively second engagement element fixing device 22a, 22b for the detachable fixing of the first or respectively second engagement element 8a, 8b in the first or second position. As can be seen, the two engagement element fixing devices 22a, 22b have respectively a spring-loaded fixing element 23a, 23b which in the first position of the respective engagement element 8a, 8b is received in a first mount 24a, 24b provided on the respective engagement element 8a, 8b. In the second position of the cam follower, the fixing element 23a, 23b is received in a second mount 25a, 25b provided on the cam follower. The first and the second engagement element 8a, 8b have respectively a base body 29a, 29b constructed in a bolt-like or pin-like manner. On a circumferential side of the base body 29a, 29b the first mount 24a, 24b is constructed as first circumferential groove 27a, 27b and the second mount 25a, 25b as second circumferential groove 28a, 28b arranged axially at a distance on the circumferential side.

[0053] With the aid of the illustration of FIG. 1 the adjustment of the cam follower 3 from the first into the second position is explained below. In the scenario of FIG. 1, the cam follower 3 is situated in the first position, in which its cam follower roller 6 is drivingly connected to the first cam 4a.

[0054] If an adjustment of the cam follower 2 from its first into its second axial position is to take place, then the first engagement element 8a of the mechanical adjustment device 7, as shown in FIG. 1, is brought into engagement with the first slide guide 9a. This takes place by means of the first electrical actuator 10a.

[0055] The first actuator 10a, as already explained, is adjustable between an inactive position, shown in FIG. 1, and an active position—indicated in dashed lines in FIG. 1. The first actuator 10a in the inactive position is mechanically out of contact with the first engagement element 8a. During an adjusting from its inactive position into its active position, the first actuator 10a adjusts the first engagement element 8a through mechanical contact from its second position into its first position. In the first position, the first engagement element 8a engages into the first slide guide 9a (cf. FIG. 1), so that the cam follower 3 is moved through the rotational movement of the camshaft 2 by means of the first slide guide 9a axially from its first position into its second position, which is illustrated in FIG. 2. After the bringing into engagement of the first engagement element 8a with the first slide guide 9a, the first actuator 10a can be moved back by the control device 11 into its inactive position again.

[0056] The first slide guide 9a can—just as the second slide guide 9b—have a ramp structure, which is not shown in the figures, such that the first engagement element 8a is brought out of engagement with the first slide guide as soon as the cam follower 3 has reached the second axial position. In this second position, the second cam 4b is in driving connection with the cam follower roller 6. The adjusting of the cam follower 3 from the second position back into the first position can take place by means of the second actuator 10b, of the second engagement element 8b and of the second slide guide 9b in an analogous manner to the previously explained transition from the first position into the second position of the cam follower 3.

[0057] In FIG. 2 a variant of the example of FIG. 1 is shown, wherein in FIG. 2 the camshaft 2 and the cam follower 3 of the valve train are shown only in an axial partial detail. In the variant according to FIG. 2, the two slide guides 9a, 9b are arranged relative to the camshaft 2 axially adjustably on the latter and are coupled to the cam follower 3 by means of a coupling element 18. Said mechanical coupling is realized here such that a movement of the slide guides 9a, 9b along the axial direction A—typically for adjustment of the cam follower 3 between the first and second position—is also accompanied by a movement of the cam follower 3 along the axial direction A. The coupling element 18, as shown in FIG. 2, is preferably constructed in a bolt-like or pin-like manner and can project radially outwards from the cam follower 3.

[0058] As FIG. 2 shows, the two slide guides 9a, 9b are formed as outer circumferential grooves 30a, 30b on a common sleeve 19. Said sleeve 19 is pushed here in an axially displaceable manner (cf. arrow 20) onto the camshaft 2. Therefore, the coupling element 18 can engage, for mechanical axial coupling, into a recess 20 provided on the sleeve 19, which recess is realized according to FIG. 2 preferably as a circumferential groove 21 formed on the outer circumference of the sleeve 19.

[0059] On a movement of the sleeve 19 relative to the camshaft 2 along the axial direction A, brought about by an engagement of the first positioning element 8a or of the second positioning element 8b into the respective slide guide 9a, 9b, the cam follower 3—owing to the present mechanical coupling of the sleeve 19 via the coupling element 18—is entrained with the cam follower 3 in the axial direction A. In this way, the desired axial adjustment of the cam follower 3 is brought about between its first and its second position.

[0060] FIG. 3 shows a variant of the example of FIG. 2. Also in the example of FIG. 3 the camshaft 2 and the cam follower 3 of the valve train are shown only in an axial partial detail. The example of FIG. 3 differs from that of FIG. 2 in that instead of the recess 20 provided on the sleeve 19, a projection 31 is provided, projecting radially outwards from the outer circumferential side 35 of the sleeve 19. The projection 31 can be constructed as a bead 32, running around in circumferential direction of the sleeve 19. The bead 32 or respectively the projection 31 engages into a recess 33 formed on the coupling element 18, which recess is preferably constructed in a groove-like manner. Said recess 33 can also be formed directly on the cam follower 3 or respectively on its cam follower base body (not shown in FIG. 3). The operating principle of projection 31 and recess 33 in the variant of FIG. 3 corresponds to the operating principle of the bolt-like coupling element 18 in connection with the recess 20 formed on the sleeve 19.