Valve train of an internal combustion engine

Abstract

A valve train may include a camshaft, a cam sleeve adjustable in an axial direction between first and second positions and non-rotatably arranged on the camshaft, a first cam and at least one second cam, a pin and at least one cam follower mounted thereon, a guide contour arranged on the cam sleeve and having first and second guide tracks, and a control pin optionally engaging in the first or second guide track to adjust the cam sleeve between the first and second positions. The at least one cam follower in the first and second positions may interact respectively with the first and second cams. On the camshaft or an internal surface of the cam sleeve, first and second snap-in recesses and a third snap-in recess therebetween may be arranged. A snap-in device having a snap-in element preloaded into the snap-in recesses may be provided, the snap-in recess fixing the cam sleeve in the first or second position. The first and second guide tracks may intersect in an intersection region. Between the first and third snap-in recesses and between the second and third snap-in recesses, first and second snap-in humps may respectively be arranged. The snap-in element may engage in the third snap-in recess when the control pin is in the intersection region.

Claims

1. A valve train of an internal combustion engine, the valve train comprising: a camshaft; a cam sleeve non-rotatably arranged on the camshaft, the cam sleeve configured to be axially adjusted between at least a first position and a second position with respect to the camshaft, the cam sleeve including: a first cam and a second cam arranged adjacent to the first cam; and a guide contour including a first guide track and a second guide track; and a rocker lever assembly including a pin extending parallel to the camshaft, the pin including: at least one cam follower; and a control pin extending perpendicularly through the pin, the control pin configured to alternately engage the first guide track and the second guide track so as to adjust the cam sleeve between the first and second positions; wherein the at least one cam follower engages the first cam when the cam sleeve is in the first position, and the at least one cam follower engages the second cam when the cam sleeve is in the second position; wherein a first snap-in recess, a second snap-in recess, and a third snap-in recess are axially aligned on an outer surface of the camshaft; wherein the third snap-in recess is axially arranged between the first and second snap-in recesses; wherein a first snap-in hump is arranged between the first snap-in recess and the third snap-in recess, and a second snap-in hump is arranged between the second snap-in recess and the third snap-in recess; wherein the cam sleeve further includes a snap-in device arranged in an internal surface of the cam sleeve, the snap-in device configured to alternately bias a snap-in element into engagement with the first and second snap-in recesses so as to hold the cam sleeve in the first position and the second position, respectively; wherein the first and second guide tracks intersect each other in an intersection region of the guide contour; and wherein the snap-in element engages the third snap-in recess when the control pin is in the intersection region.

2. The valve train according to claim 1, wherein at least one of the first snap-in hump and the second snap-in hump has a rounded or a pointed dome.

3. The valve train according to claim 1, wherein: a first flank of the first snap-in hump falling towards the third snap-in recess has a steeper slope than a second flank of the first snap-in hump falling towards the first snap-in recess; and/or a first flank of the second snap-in hump falling towards the third snap-in recess has a steeper slope than a second flank of the second snap-in hump falling towards the second snap-in recess.

4. The valve train according to claim 1, wherein: an axial length of the third snap-in recess is greater than an axial length of the first snap-in recess and an axial length of the second snap-in recess; and/or a radial height of at least one of the first snap-in hump and the second snap-in hump is less than a radius of the camshaft.

5. The valve train according to claim 1, wherein at least one of the first snap-in hump and the second snap-in hump is at least one of hardened, heat-treated, and coated.

6. The valve train according to claim 1, wherein: the cam sleeve is non-rotatably arranged on the camshaft via an anti-rotation device; and/or the camshaft is a splined shaft configured to interact with internal teeth arranged on an internal surface of the cam sleeve.

7. A camshaft for a valve train, the camshaft comprising: a first snap-in recess, a second snap-in recess, and a third snap-in recess axially aligned on an outer surface of the camshaft, wherein the third snap-in recess is axially arranged between the first snap-in recess and the second snap-in recess, and wherein a first snap-in hump is arranged between the first snap-in recess and the third snap-in recess, and a second snap-in hump is arranged between the second snap-in recess and the third snap-in recess.

8. The camshaft according to claim 7, wherein at least one of the first snap-in hump and the second snap-in hump has a rounded or a pointed dome.

9. The camshaft according to claim 7, wherein: a first flank of the first snap-in hump falling towards the third snap-in recess has a steeper slope than a second flank of the first snap-in hump falling towards the first snap-in recess; and/or a first flank of the second snap-in hump falling towards the third snap-in recess has a steeper slope than a second flank of the second snap-in hump falling towards the second snap-in recess.

10. The camshaft according to claim 7, wherein: an axial length of the third snap-in recess is greater than an axial length of the first snap-in recess and an axial length of the second snap-in recess; and/or a radial height of at least one of the first snap-in hump and the second snap-in hump is less than a radius of the camshaft.

11. The camshaft according to claim 7, wherein at least one of the first snap-in hump and the second snap-in hump is hardened, heat-treated, and coated.

12. The valve train according to claim 7, wherein the camshaft is configured to engage a cam sleeve in an axially adjustable manner; and wherein: the camshaft is further configured to non-rotatably engage the cam sleeve via an anti-rotation device; and/or the camshaft is a splined shaft configured to interact with internal teeth arranged on an internal surface of the cam sleeve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) There it shows, in each case schematically

(2) FIG. 1 shows a view of a valve train according to the invention,

(3) FIG. 2 shows a view of a camshaft according to the invention,

(4) FIG. 3 shows a detail representation A from FIG. 2,

(5) FIG. 4 shows a detail view of the camshaft according to the invention with cam sleeve arranged thereon,

(6) FIG. 5 shows a sectional representation through a cam sleeve according to the invention,

(7) FIG. 6 shows a sectional representation through a cam sleeve according to the invention on a camshaft,

(8) FIG. 7 shows a representation as in FIG. 6 with additional detail representation,

(9) FIG. 8 shows an alternative representation to FIG. 1 with separately arranged control pin,

(10) FIG. 9 shows a similar representation as in FIG. 1,

(11) FIG. 10 shows a sectional representation through a first embodiment of the camshaft.

DETAILED DESCRIPTION

(12) According to the FIGS. 1, 6 and 7 to 9, a valve train 1 of an internal combustion engine 2 which is not shown in more detail according to the invention comprises a camshaft 3 having a first cam 4 and a second cam 6 that is axially adjacent thereto in the axial direction 5. The first cam 4 and the second cam 6 are shiftably arranged on a cam sleeve 26 (see also FIGS. 5 and 10) that is adjustable between at least two positions on the camshaft 3, wherein on the cam sleeve 26 additionally a guide contour 11 with two guide tracks 12, 13 intersecting one another x-like are arranged. Here, the cam sleeve 26 can be formed in one piece together with the cams 4, 6 and the guide contour 11, in particular in monobloc form.

(13) Likewise provided can be a rocker lever assembly 7 having a pin 8 (see FIG. 1) that is fixed in the axial direction 5, on which at least one cam follower 9, here two cam rollers 9, are axially fixed and rotatably mounted. The cam follower 9 can also be formed as a sliding element. Here, the pin 8 is mounted in associated bearing eyes 10 of the rocker lever assembly 7. In the pin 8, a control pin 14 is arranged according to FIG. 1 and FIG. 9, which optionally engages in the first or the second guide track 12, 13 (according to FIG. 1 in the second guide track 13) and thereby adjusts the cam sleeve 26 between its two positions. Obviously, the control pin 14 can also be arranged separately as is shown in FIG. 8. Here, the cam follower 9 or the cam rollers 9 interact in a first position of the cam sleeve 26 with the first cam 4 (see FIG. 1) and in a second position of the cam sleeve 26 with the second cam 6 (see FIGS. 8 and 9). Because of this, different valve opening times or a cylinder cut-off can also be realised for example.

(14) According to a first alternative of the valve train 1 according to the invention, a first snap-in recess 15 and a second snap-in recess 16 (see FIGS. 2 and 3 and 10) arranged adjacent thereto in the axial direction 5 is now provided on the camshaft 3. Provided, furthermore, is a snap-in device 17 having a snap-in element 19 that is spring-preloaded into the first, the second or a third snap-in recess 18, which fixes the cam sleeve 26 and thereby the cams 4, 6 in the first position or the second position, provided the snap-in element 19 engages in the first or second snap-in recess 15, 16. Here, the snap-in device 17 can be arranged in the region of the guide contour 11 or in the region of the cams 4, 6 (see detail representation in FIGS. 1 and 10).

(15) Viewing FIGS. 1, 8 and 9 further it is evident that the guide tracks 12, 13 intersect one another x-like in an intersection region 20. Between the first snap-in recess 15 and the second snap-in recess 16 arranged axially adjacent thereto, the previously mentioned third snap-in recess 18 is provided on the camshaft 3 according to the FIGS. 2, 3 and 10, wherein between the first and the third snap-in recess 15, 18 a first snap-in hump 21 and between the second and the third snap-in recess 16, 18 a second snap-in hump 22 are arranged, as a result of which the snap-in element 19 in the intersection region 20 engages in the third snap-in recess 18 and is guided in the same and because of this reliably guides the control pin 14 over the intersection region 20 without the same colliding with a land 23 separating the two guide tracks 12, 13 or threading into the wrong guide track 12, 13 and because of this a changeover is not possible. With the third snap-in recess 18 according to the invention it is thus possible to employ an installation space-optimised guide contour 11 with two guide tracks 12, 13 intersecting one another and because of this create not only an installation space-optimised but also an assembly-friendly and cost-effective valve train 1.

(16) Viewing the FIGS. 2, 3 and 10 it is evident that the first snap-in hump 21 and/or the second snap-in hump 22 have a rounded dome 24. Because of this, a smooth transition between the individual snap-in recesses 15, 18, 16 is possible. Alternatively, it can obviously also be provided that the domes 24 are designed pointed, as a result of which a quick overcoming of the dome 24 is made possible and an axial force support for shifting the cam sleeve 26 in the axial direction 5 can be provided, provided the dome 24 is overcome.

(17) The flank of the first snap-in hump 21 falling towards the third snap-in recess 18 has a steeper slope according to the FIGS. 2 and 3 than a flank falling towards the first snap-in recess 15, as a result of which a higher support force acting in the axial direction 5 for shifting the cam sleeve 26 in the axial direction 5 can be provided. In the same way, the flank of the second snap-in hump 22 falling towards the third snap-in recess 18 also has a steeper slope than the flank falling towards the second snap-in recess 16. Viewing the individual snap-in recesses 15, 18, 16 according to the FIGS. 2 and 3 further it is evident that the third snap-in recess 18 has a greater axial length L than the first snap-in recess 15 and the second snap-in recess 16, as a result of which a smoother adjusting of the cam sleeve 26 in the intersection region 13 and at the same time a reliable guiding of the control pin 14 in the intersection region 20 is made possible. Through the significantly shorter axial length of the first and second snap-in recess 16, a tight axial guidance of the snap-in element 19 and thus a reliable guidance of the cam follower on the respective cam profile of the first or the second cam 4, 6 is thereby enforced. A radial height H of the first and/or second snap-in hump 21, 22 is smaller than a radius R of the cam sleeve 26, as a result of which the switching operation and the shifting of the cam sleeve 26 can be facilitated. The flanks falling towards the third snap-in recess 18 on the first or second snap-in hump 21, 22 can, as drawn in, be formed linearly or concavely and thus merge without a bend into a bottom 25 of the third snap-in recess 18.

(18) Viewing FIGS. 1 to 10 it is evident that the camshaft 3 on its outer surface at least in the region of the cam sleeve 26 comprises axial grooves 27 which interact with internal teeth 28 (see FIGS. 4 and 5) arranged on an internal surface of the cam sleeve 26 and thereby make possible a guided axial shifting of the cam sleeve 26 on the camshaft 3. The axial grooves 27 on the camshaft 3 can form an external gearwheel profile which interacts with an internal gearwheel profile on the cam sleeve 26 formed complementarily thereto in such a manner that the cam sleeve 26 is shiftably arranged on the camshaft 3 in the axial direction 5 but non-rotatably on the same, i.e. is rotatable only together with the same. Generally, an anti-rotation device can also be provided which prevents a rotation of the cam sleeve 26 relative to the camshaft 3, but makes possible an axial shifting of the cam sleeve 26 on the camshaft 3. Such an anti-rotation device can also comprise a feather keyway, a polygon profile and the like.

(19) Besides the entire valve train 1, the camshaft 3 according to the invention for such a valve train 1 is to be protected as well, wherein the same according to FIGS. 2 and 3 comprises the previously described first snap-in recess 15 and the second snap-in recess 16 arranged axially adjacent thereto and a third snap-in recess 18 arranged in between in the axial direction 5. Between the first and the third snap-in recess 15, 18 a first snap-in hump 21 is arranged, while between the second and the third snap-in recess 16, 18 a second snap-in hump 22 is arranged. The first, second and third snap-in recess 15, 16, 18 in this case are formed as a relief cut. The first snap-in recess 15, the third snap-in recess 18 and the second snap-in recess 16 are arranged one behind the other in the axial direction 5 and only separated by the relevant snap-in humps 21, 22. With the camshaft 3 according to the invention it is possible for the first time to use an installation space-optimised guide contour 11 with two guide tracks 12, 13 intersecting one another in an intersection region 20 without it having to be feared that in the process, during an adjusting of the cam sleeve 26 from its first into its second position and thus from a change of following of the at least one cam follower 9 from the first to the second cam 4, 6 or vice versa, a threading into the wrong guide track 12, 13 or a collision with a land separating the two guide tracks 12, 13 has to be feared.

(20) With the camshaft 3 according to the invention the first snap-in hump 21 and/or the second snap-in hump 22 have a rounded dome 24, by way of which a smooth transition between the individual snap-in recesses 15, 18, 16 is made possible. In addition, the first and/or second snap-in hump 21, 22 can be hardened, heat-treated and/or coated. By way of hardening, the wear resistance can be increased in particular, as also by means of a coating, for example a DLC coating.

(21) According to the second alternative of the valve train 1 according to the invention or of the cam sleeve 26 according to the invention, the same has a first snap-in recess 15 and a second snap-in recess 16 arranged axially adjacent thereto, wherein between the first snap-in recess 15 and the second snap-in recess 16 a third snap-in recess 18 is provided, wherein between the first and the third snap-in recess 15, 18 a first snap-in hump 21 and between the second and the third snap-in recess 16, 18 a second snap-in hump 22 are arranged (see FIGS. 5 to 7).

(22) Here, the first snap-in recess 15, the second snap-in recess 16 and the third snap-in recess 18 can be formed as annular grooves on the internal surface of the cam sleeve 26 which are open towards the inside, as is shown in FIG. 5, wherein the snap-in device 17 is arranged in an opening crossing the camshaft 3 and comprises a coil spring 29 as well as two spheres 90 as snap-in elements 19. By way of this, both the snap-in recesses 15, 16, 18 and also the snap-in device 17 can be produced in a technically simple and cost-effective manner.

(23) Viewing FIG. 7 it is evident that the first snap-in hump 21 and/or the second snap-in hump 22 has/have a rounded dome 24. By way of this, a smooth transition between the individual snap-in recesses 15, 18, 16 is possible. Alternatively, it can also be obviously provided that the domes 24 are formed pointed as a result of which a quick overcoming of the dome 24 is made possible and an axial force support for shifting the cam sleeve 24 in the axial direction 5 can be provided, provided the dome 24 is overcome. With the cam sleeve 26 according to the invention, the first and/or second snap-in hump 21, 22 can also be additionally hardened, heat-treated and/or coated.

(24) Purely theoretically, a shiftability of the cam sleeve 26 and an additional shifting of the pin 8 is also conceivable, which makes possible further configurations in terms for example of being able to switch between three cam contours, wherein one contour can be utilised for a cylinder cut-off.