Valve train of an internal combustion engine

Abstract

A valve train of an internal combustion engine may include a camshaft, first and second cams, a rocker arm assembly having a displacement bolt, which may be adjustable between at least first and second positions in the axial direction and on which at least one cam roller, may be mounted in an axially fixed and rotatable manner, wherein the displacement bolt may be mounted in associated bearing lugs of the rocker arm assembly, a guide contour arranged on the camshaft and having first and second guide tracks, a switching pin, which may be arranged in the displacement bolt and which may optionally engage with the first or second guide track to adjust the displacement bolt between the first and second positions. In the first and second positions, the cam roller may cooperate with the first and second cams, respectively. First and second catch recesses may be provided on the displacement bolt. A catch device may engage with a catch element, which may be biased into the first or second catch recess and which may secure the displacement bolt in the first or second position. The first and second guide tracks may cross one another in a crossing region. A third catch recess may be provided between the first and second catch recesses, wherein a first catch protuberance may be arranged between the first and the third catch recesses, and a second catch protuberance may be arranged between the second and the third catch recesses, wherein the catch element may engage with the third catch recess in the crossing region.

Claims

1. A valve train of an internal combustion engine, the valve train comprising: a camshaft including a first cam and a second cam arranged axially adjacent to the first cam; a rocker arm assembly including: a displacement bolt extending parallel to the camshaft and configured to be axially adjusted between at least a first position and a second position with respect to the rocker arm assembly; and at least one cam roller rotatably mounted on the displacement bolt; a guide contour arranged on the camshaft, the guide contour including a first guide track and a second guide track; and a switching pin extending perpendicularly through the displacement bolt, the switching pin configured to alternately engage the first and second guide tracks so as to adjust the displacement bolt between the first and second positions; wherein the at least one cam roller cooperates engages the first cam when the displacement bolt is in the first position, and the at least one cam roller engages the second cam when the displacement bolt is in the second position; wherein the displacement bolt comprises a catch unit including a first catch recess and a second catch recess arranged axially adjacent to the first catch recess; wherein the rocker arm assembly further includes a catch device configured to alternately bias a catch element into engagement with the first and second catch recesses so as to secure the displacement bolt in the first and second positions, respectively; wherein the first and second guide tracks intersect each other in a crossing region of the guide contour; wherein the catch unit further includes a third catch recess arranged between the first catch recess and the second catch recess, a first catch protuberance arranged between the first and third catch recesses, and a second catch protuberance arranged between the second and third catch recesses; and wherein the catch element engages the third catch recess when the switching pin is in the crossing region.

2. The valve train according to claim 1, wherein at least one of the first catch protuberance and the second catch protuberance has a rounded or pointed tip.

3. The valve train according to claim 1, wherein: a first edge of the first catch protuberance, sloping towards the third catch recess, has a greater down-grade than a second edge of the first catch protuberance, sloping towards the first catch recess; and/or a first edge of the second catch protuberance, sloping towards the third catch recess, has a greater down-grade than a second edge of the second catch protuberance, sloping towards the second catch recess.

4. The valve train according to claim 1, wherein the catch element is formed as a ball.

5. The valve train according to claim 1, wherein: an axial length of the third catch recess is greater than an axial length of the first catch recess and an axial length of the second catch recess; and/or a radial height of at least one of the first catch protuberance and the second catch protuberance is less than a radius of the displacement bolt.

6. The valve train according to claim 1, wherein at least one of the first catch protuberance and the second catch protuberance is at least one of cured, heat-treated, and coated.

7. A displacement bolt for a valve train, the displacement bolt comprising: a catch unit including: a first catch recess and a second catch recess arranged axially adjacent to the first catch recess; a third catch recess arranged between the first catch recess and the second catch recess; a first catch protuberance arranged between the first and third catch recesses; and a second catch protuberance arranged between the second and third catch recesses.

8. The displacement bolt according to claim 7, wherein at least one of the first catch protuberance and the second catch protuberance has a rounded or a pointed tip.

9. The displacement bolt according to claim 7, wherein: a first edge of the first catch protuberance, sloping towards the third catch recess, has a greater down-grade than a second edge of the first catch protuberance, sloping towards the first catch recess; and/or a first edge of the second catch protuberance, sloping towards the third catch recess, has a greater down-grade than a second edge of the second catch protuberance, sloping towards the second catch recess.

10. The displacement bolt according to claim 7, wherein: an axial length of the third catch recess is greater than an axial length of the first catch recess and an axial length of the second catch recess; and a radial height of at least one of the first catch protuberance and the second catch protuberance is less than a radius of the displacement bolt.

11. The displacement bolt according to claim 7, wherein at least one of the first catch protuberance and the second catch protuberance is at least one of cured, heat-treated, and coated.

12. The displacement bolt according to claim 7, wherein the catch unit is formed separately from the displacement bolt and consists of a different material than the rest of the displacement bolt.

13. The displacement bolt according to claim 12, wherein the catch unit consists of a ceramic material or a metal matrix composite material.

14. The displacement bolt according to claim 12, wherein the catch unit is sintered.

15. The displacement bolt according to claim 13, wherein the catch unit is connected to the displacement bolt via a substance-to-substance bond.

16. The valve train according to claim 1, wherein the catch unit is formed separately from the displacement bolt and consists of a different material than the displacement bolt.

17. The valve train according to claim 16, wherein the catch unit consists of a ceramic material or a metal matrix composite material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In each case schematically,

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

(3) FIG. 2 shows a view onto a displacement bolt according to the invention,

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

(5) FIG. 4 shows a detail illustration of the displacement bolt according to the invention comprising a separately produced catch device.

DETAILED DESCRIPTION

(6) According to FIG. 1, a valve train 1 according to the invention of an internal combustion engine 2, which is not illustrated in more detail, has a camshaft 3 comprising a first cam 4 and a second cam 6 adjacent thereto in the axial direction 5. Also provided is a rocker arm assembly 7 comprising a displacement bolt 8 (also see FIGS. 2 and 3), which can be adjusted between at least two positions in the axial direction 5 and on which at least one cam roller 9, here two cam rollers 9, are mounted in an axially fixed and rotatable manner. The displacement bolt 8 is thereby mounted in associated bearing lugs 10 of the rocker arm assembly 7. A guide contour 11 comprising a first guide track 12 and a second guide track 13 is arranged on the camshaft 3. A switching pin 14, which optionally engages with the first or the second guide track 12, 13 (according to FIG. 1 with the second guide track 13) and thus adjusts the displacement bolt 8 between its two positions, is additionally arranged in the displacement bolt 8. In a first position of the displacement bolt 8, the cam roller 9 or the cam rollers 9, respectively, thereby cooperate with the first cam 4 (see FIG. 1), and in a second position of the displacement bolt 8 cooperates with the second cam 6. Different valve opening times or also a cylinder turn-off, for example, can be realized thereby.

(7) A first catch recess 15 as well as a second catch recess 16, which is arranged axially adjacent thereto in the axial direction 5, is now arranged on the displacement bolt 8 (see FIGS. 2 and 3). A catch device 17 is furthermore provided comprising a catch element 19, which is spring-biased into the first, the second or a third catch recess 18 and which secures the displacement bolt 8 and via the latter the at least one cam roller 9 in the first position or the second position, provided that the catch element 19 engages with the first or second catch recess 15, 16.

(8) When further looking at FIG. 1, it can be seen that the guide tracks 12, 13 cross one another in an x-shaped manner in a crossing region 20. According to FIGS. 2 and 3, the above-mentioned third catch recess 18 is provided between the first catch recess 15 and the second catch recess 16, which is arranged axially adjacent thereto, on the displacement bolt 8, wherein a first catch protuberance 21 is arranged between the first and the third catch recess 15, 18, and a second catch protuberance 22 is arranged between the second and the third catch recess 16, 18, whereby the catch element 19 engages with the third catch recess 18 in the crossing region 20 and is guided therein and thus reliably guides the switching pin 14 over the crossing region 20, without said switching pin colliding with a web 23 separating the two guide tracks 12, 13 or threading into the wrong guide track 12, 13 and a switch-over is thus not possible. With the third catch recess 18 according to the invention it is thus possible to use an installation space-optimized guide contour 11 comprising to guide tracks 12, 13, which cross one another, and to thus not only create an installation space-optimized, but also an assembly-friendly and cost-efficient valve train 1.

(9) When looking at FIGS. 2 to 4, it can be seen that the first catch protuberance 21 and/or the second catch protuberance 22 have a rounded tip 24. A smooth transition between the individual catch recesses 15, 18, 16 is possible thereby. It goes without saying that it can alternatively also be provided that the tips 24 are formed to be pointy, whereby a quick overcoming of the tip 24 is made possible and an axial force support for displacement of the displacement bolt 8 in the axial direction 5 can be provided, provided that the tip 24 is overcome.

(10) According to FIGS. 2 and 3, the edge of the first catch protuberance 21, which slopes to the third catch recess 18, thereby has a larger down-grade than an edge, which slopes to the first catch recess 15, whereby a higher supporting force acting in the axial direction 5 for displacing the displacement bolt 8 in the axial direction 5 can be provided. The edge of the second catch protuberance 22, which slopes to the third catch recess 18, likewise also has a larger down-grade than the edge, which slopes to the second catch recess 16. When further looking at the individual catch recesses 15, 18, 16 according to FIGS. 2 and 3, it can be seen that the third catch recess 18 has a larger axial length L than the first catch recess 15 and the second catch recess 16, whereby a smooth adjustment of the adjustment bolt 8 in the crossing region 20 and simultaneously a reliable guidance of the switching pin 14 in the crossing region 20 is made possible. Due to the significantly smaller axial length of the first and second catch recess 16, a narrow axial guidance of the catch element 19 and thus a reliable guidance of the cam rollers 9 is forced here on the respective cam profile of the first or second cam 4, 6 A radial height H of the first and/or second catch protuberance 21, 22 is thereby smaller than a radius R of the displacement bolt 8, whereby the switching process and the displacement of the displacement bolt 8 can be facilitated. The edges on the first or second catch protuberance 21, 22, which fall to the third catch recess 18, can thereby be formed linearly, as indicated, or can transition concavely and thus without a kink into a bottom 25 of the third catch recess 18.

(11) In addition to the entire valve train 1, the displacement bolt 8 according to the invention for a valve train 1 of this type is to also be protected, wherein, according to FIG. 2, said displacement bolt has the above-described first catch recess 15 as well as the second catch recess 16, which is arranged axially adjacent thereto, and a third catch recess 18, which is arranged therebetween in the axial direction 5. A first catch protuberance 21 is thereby arranged between the first and the third catch recess 15, 18, while a second catch protuberance 22 is arranged between the second and the third catch recess 16, 18. The first, second, and third catch recess 15, 16, 18 is formed as relief in this case. The catch device 17 is thus formed in one piece with the displacement bolt 8.

(12) In the alternative, it is also conceivable that the catch recesses 15, 16, 18 and the first and second catch protuberances 21, 22 are part of a separate catch element 26, which consists of a different material than the remaining displacement bolt 8. In this case, the catch element 26 can thus be formed as insert, which engages with a corresponding recess on the displacement bolt 8. The catch element 26 can thereby be connected to the displacement bolt 8 in a non-positive manner, in a non-positive manner, in a positive manner, and/or in particular by means of a substance-to-substance bond, for example by means of soldering, adhering or welding.

(13) The catch element 26 can also consist of or can have a ceramic material or a metal matrix composite material, preferably hard metal, whereby the wear resistance thereof can be significantly improved. The catch element 26 can also be produced without finishing to end contour by means of sintering, whereby a wear resistant component can likewise be created.

(14) With the displacement bolt 8 according to the invention it is possible for the first time to use an installation space-optimized guide contour 11 comprising two guide tracks 12, 13, which cross one another in a crossing region 20, without having to fear thereby that, in response to the adjustment of the adjustment bolt 8 from its first into its second position and thus from a tapping change of the at least one cam roller 9 from the first to the second cam 4, 6 or vice versa, a threading into the wrong guide tack 12, 13 or a collision with a web separating the two guide tracks 12, 13 having to be feared.

(15) In the case of the displacement bolt 8 according to the invention, the first catch protuberance 21 and/or the second catch protuberance 22 have a rounded tip 24, whereby a smooth transition is made possible between the individual catch recesses 15, 18, 16. The first and/or second catch protuberance 21, 22 can furthermore be cured, heat-treated and/or coated. By means of a curing, in particular the wear resistance can be increased, as well as by means of a coating, for example a DLC coating.