WO2011157499A1

WO2011157499A1 - Drag lever for a valve operating mecahnism of an internal combustion engine

Info

Publication number: WO2011157499A1
Application number: PCT/EP2011/057847
Authority: WO
Inventors: Stephan Möck
Original assignee: Schaeffler Technologies Gmbh & Co. Kg
Priority date: 2010-06-17
Filing date: 2011-05-16
Publication date: 2011-12-22
Also published as: CN102947552A; DE102010024196A1; CN102947552B

Abstract

A drag lever (1) has a cam roller (3) which is mounted on an axle pin (24) by means of a needle ring (10). Here, the axle pin (23) is arranged in holes of side walls (5 and 6) of the lever (2) which are spaced apart from one another, and, in order to reduce the Hertzian stress, an axial dimension of the needle ring (10) is greater than the width of the cam roller (3) on its cam run-on surface (19) which faces the cam. Here, a first end (10a) of the needle ring (10) is to protrude on one side beyond a first end side (12) of the cam roller (3) and is to end immediately adjacently to the corresponding side wall (5) of the lever (2) or is to bear against said side wall (5). Moreover, the needle ring (10) is to terminate at its second end (10b) substantially with a second end side (14) of the cam roller (3). A spacer sleeve (15) is to be arranged between said second end (10b) of the needle ring (10) and the side wall (5) which faces it.

Description

Name of the invention

Drag lever for a valve train of an internal combustion engine Description

The invention relates to a drag lever for a valve train of an internal combustion engine, which serves to actuate a gas exchange valve and having a pivotally supported at one end lever, at the otherem end a valve stem support for the valve stem end of the gas exchange valve is formed, and with a cam roller on during operation of the internal combustion engine, a cam of a camshaft starts and which is mounted by means of a needle bearing having a needle bearing on a pivot pin, wherein the axle pin is arranged in bores of spaced apart side walls of the lever and wherein the axial dimension of the needle ring is greater than the width the cam roller on its cam-facing cam contact surface.

Field of the invention

Drag levers are arranged in internal combustion engines with overhead camshaft within the valve train as transmission elements between the cams and the gas exchange valves to be actuated. They consist of a one-armed lever, which is supported by means of its one end on a mostly hydraulically adjustable support member and engages with its other end via a valve stem support on the gas exchange valve to be opened. In the central portion of the lever either a sliding surface or a cam roller are arranged, to which the respective cam starts and causes the pivoting movement of the finger lever. By using this cam roller, which rolls on the circumference of the respective cam, the friction in the valve train can be significantly reduced, so that it is possible to achieve a significant reduction in fuel consumption during operation of the internal combustion engine. As an alternative to these valve trains with cam followers, which have a cam roller are Types of internal combustion engines with overhead camshaft known in which are used as cam follower rocker or bucket tappets. These cam followers can also be provided with a cam roller. A drag lever of the type described in the preamble of claim 1 is known from DE 101 21 798 A1. This drag lever has a cam roller which fills the entire space between the spaced side walls of the lever. As a result, the raceways for a bearing for the cam roller on a spindle serving Nellellager should be made wider to reduce the surface pressure (Hertzian pressure) on the corresponding raceways of an inner ring and an outer ring. The drag lever is provided for a variable-stroke valve drive, in which at least two cams with a different outer contour and a uniform cam base circle are provided for each gas exchange valve to be actuated. The different cam contour also includes differences in cam lobe, that is, there is a cam with a large cam lobe and a cam with a small cam lobe, wherein the cam lobe is slidably mounted on the camshaft so as to selectively engage one of the two lobes on the outer circumference of the cam roller. On its outer circumference, the cam roller is provided in each case in the edge region with circumferential recesses, whereby a free space is provided in which the cam can move freely with large cam lobe when the adjacent cam with small cam lobe actuates the cam follower on the cam roller. In this embodiment, the cam roller whose provided for the radial contact with the needle ring inner raceway and outer race are therefore wider than its provided on the outer circumference cam contact surface.

Object of the invention

The invention has the object of providing a drag lever of the type mentioned in such a way that the weight of this lever and its manufacturing costs are reduced. Summary of the invention

This object is achieved according to the characterizing part of claim 1, characterized in that a first end of the needle ring projects axially beyond a first end side of the cam roller and extends to a side wall of the lever that the needle ring at its second end substantially with a second end face of Cam roller closes and that between the second end of the needle ring and the side wall facing this a dance is arranged dance. Consequently, in contrast to the generic state of the art, the needle ring, which can be cage-fully full cage or caged, unilaterally protrude beyond the axial extent of the needle roller. The reason for this configuration according to the invention of supporting the cam roller is that the Hertzian pressure is significantly greater on the inner race, which has a small radius of curvature, than on the outer race, which has a large radius of curvature. Therefore, the needles that protrude beyond the outer race, roll over its entire length on the inner race. As a result, the surface pressure on the inner race is effectively reduced.

On the side of the cam roller on which the needle ring protrudes axially beyond this, a space necessary for this is created by the fact that provided on this side of the cam roller side wall extends to the first end side of the cam roller spaced. Since the other side wall is also spaced from the cushions roll, u.zw. to the second end face, a spacer sleeve is used in this space, which rests on the one hand to the needle ends and on a possibly existing inner ring and the other on the side wall. In a further embodiment of the invention, the lever, based on its longitudinal center plane to be formed symmetrically. Thus, the lever may have a relatively simple geometric shape and can therefore be produced using a low-cost manufacturing process. An advantage is terhin, if the spacer sleeve has special sliding properties, that is, that it is slidably guided both at the ends of the needle ring than on the lateral surface of the side wall. Furthermore, an inner race for the needles of the needle ring can be formed directly on the axle. The axially above the cam roller protruding needles roll over its entire length on the axle from. The spacer then supports only at the end of the needle ring and on the side wall. Alternatively, however, it is also possible to arrange a separate inner ring on the axle, which forms an inner race corresponding to the width of the needle ring. This inner ring may be rotatably mounted on the axle.

In a further embodiment of the invention it is provided that the lever, seen in cross section, U-shaped, wherein the side walls are interconnected by a transverse wall, in which a serving for receiving the cam roller recess is arranged. This lever profile has a sufficient rigidity and can be produced in an advantageous manner by a non-cutting shaping process, in particular by cold deformation, from a punched sheet metal blank. The outer ring of the cam roller can be guided on the front side at the edges of the recess. In addition, the appropriately trained roller cam follower should be arranged in the valve train such that the open U-shaped profile is remote from the support element and the gas exchange valve. On an outer lateral surface of the transverse wall, consequently, the cap and the support, which acts directly on the end of a valve stem, are formed.

The transverse wall can have a course, radially to the protruding end of the needle ring, so that sufficient clearance for this created and the rigidity of the lever is not affected. Alternatively, it is possible to provide in addition to the recess for the role of a rectangular release for the above needles, which up to the Side wall extends and whose extension in the longitudinal direction of the lever is greater than an inner diameter of the outer ring of the cam roller.

Furthermore, to be in the development of the teaching of the claim, the axial dimension of the needle bearing by 30% to 60% greater than the width of the cam roller. A corresponding relation of the width of the cam roller to the width of the needle ring results in that the Hertzian pressure is reduced sufficiently and that the structural dimensions of the finger lever still allow its space-saving arrangement in the valve train.

Finally, it is provided that the provided with a cam follower cam lever is provided for a switchable valve train, in which roll on the camshaft, at least two axially displaceable cam with different cam contours optionally on the outer circumference of the cam roller. A corresponding valve drive is explained in detail in DE 100 54 623 A1. A corresponding clearance of the large cam can be achieved in that the side wall lying in this area is provided at its upper edge with a flattening or recess.

Short description of the drawing

For further explanation of the invention reference is made to the drawing, in which an embodiment of a finger lever is shown in simplified form. Show it:

1 shows a plan view of a drag lever according to the invention,

FIG. 2 shows a perspective view of the finger lever according to FIG. 1,

Figure 3 shows a longitudinal section along the line III - III through the drag lever of Figure 1 and FIG. 4 shows a perspective view from below of the drag lever according to FIG. 1

Detailed description of the drawing

In the figures 1 to 4 1 denotes a drag lever, which consists essentially of a U-shaped lever 2 and a cam roller 3. The U-shaped lever 2 is formed as a chipless manufactured sheet metal part, wherein in the context of the forming process first a blank punched out of sheet metal and then cold-formed. Thus, the lever 2 has a transverse wall 4 and side walls 5 and 6 extending therefrom.

At one end of the lever 2, the transverse wall 4 is formed as a valve stem support 7, with which the lever 2 rests on one end of a valve stem, not shown, of a gas exchange valve. At the opposite end of the lever 2, as can be seen from the figures, a dome 8 is formed in the transverse wall 4, via which the lever 2 used in the valve drive is supported on a support element, also not shown. This support element is preferably formed hydraulically variable in length. As a result, the articulation point of the lever 2 is displaced in such a way that any valve clearance that may occur between the valve stem support 7 and the valve stem end can be compensated. In the region of the dome 8, the distance of the side walls 5 and 6 is increased to each other, so that a sufficient space for their arrangement is created.

As can be seen in particular from FIGS. 1, the cam roller 3 is arranged in the transverse wall 4 in a recess 9 designed substantially with a rectangular outer contour. In this case, according to FIG. 1, a first end 10 a of a needle ring 10, of which individual needles 1 1 can be seen in the illustration according to FIG. 1, protrudes on one side over a first end face 12 of the cam roller 3. The ends 10a of the needles 1 1 are up to an inner circumferential surface 13 of the side wall 6 reaching and guided on this sliding. On a second end face 14 of the cam roller 3, a spacer sleeve 15 is arranged between the side wall 5 of the lever 2 and the second ends 10b of the needle ring 10, whose axial dimension substantially corresponds to that of the projection of the needle ring 10 on the first end face 12. Furthermore, it can be seen from FIG. 1 that an injection opening 16 directed onto the cam roller 3 is provided on the dome 8, via which lubricating oil is applied to the cam roller 3. In the region of the projecting first end 10 a of the needle ring 10 and the spacer sleeve 15, as shown in FIG. 3, the transverse wall 4 is provided with a bulge 17 downwards, ie, the transverse wall 4 extends radially to the needle ring 10 and to the spacer sleeve and thus creates a sufficient space, in particular for the above needles 1 1.

It can be seen in the side view and in the sectional illustration of the roller cam follower 1 according to the invention according to FIGS. 2 and 4 that the cam roller 3 has an outer ring 8 with a cam contact surface 19 and an outer race 20 for the needle rim 10. Furthermore, the needles 1 1 of the needle bearing are guided on an inner race 21 formed on an inner ring 21, wherein this inner ring 21 and thus the entire cam roller 3 by means of an axle pin 23 relative to the side walls 5 and 6 is mounted. On this pivot pin 23 and the spacer sleeve 15 is arranged, wherein it rests both at the end of the inner ring 21 and at the second ends 10b of the needle bearing 10. The side walls are otherwise provided with flats 24, so that a switchable valve train with a longitudinally displaceable on a camshaft cam pair ensures sufficient clearance of the large cam. Furthermore, the side walls 5 and 6 in the region of the dome 8 grooves 25 and 26, in which a clip, not shown, on the side walls 5 and 6 can be fixed. This clamp serves to connect the drag lever 1 with the support element to a preassembled unit that can be delivered for assembly in the corresponding cylinder head. To guide the Rollenschlepphebels 1 at the valve stem end of the Gas exchange valve, the lever 2 is provided in the region of the support 7 with tabs 27 and 28, which extend from the side walls 5 and 6 and are bent to below the transverse wall 4. These bent tabs 27 and 28 are spaced apart from each other by a distance that corresponds approximately to the diameter of the valve creating end.

Figures 1 to 4 it can be seen that the relatively narrow formed cam roller 3 is provided with a considerably wider needle ring 10, which projects beyond the cam roller 3 on one side, so that the surface pressure of the trained as needles 1 1 rolling elements on the inner ring 22 are significantly reduced can. For this purpose, the lever 2 is formed symmetrically, ie, the axial clearance between the side wall 5 and the second end 10b of the needle bearing 10 is compensated by the spacer sleeve 15.

LIST OF REFERENCE NUMBERS

1 drag lever

2 levers

3 cam roller

4 transverse wall

5 sidewall

6 side wall

7 valve stem support

8 calotte

9 recess

10 needle ring

10a first end of 10

10b second end of 10

1 1 needles

12 first face of 3

13 inner lateral surface of 6

14 second front side of 3

15 spacer sleeve

16 spray opening

17 bulge of 4

18 outer ring

19 cam contact surface

20 outer raceway

21 inner ring

22 inner race

23 axle bolts

24 flattenings

25 groove

26 groove

27 tab

28 tab

Claims

claims

Drag lever (1) for a valve train of an internal combustion engine, which serves to actuate a gas exchange valve and a pivotally supported at one end lever (2), at the other end a Ventilschaftauflage (7) is designed for a valve stem end of the gas exchange valve, and with a Cam roller (3) on which a cam of a camshaft starts during operation of the internal combustion engine and which is mounted by means of a needle bearing (10) having needle bearing on a pivot pin (23), wherein the axle pin (23) in bores of spaced apart side walls ( 5 and 6) of the lever (2) is arranged and wherein the axial dimension of the needle roller (0) is greater than the width of the cam roller (3) on its cam-facing cam contact surface (19), characterized in that a first end (10a ) of the needle ring (10) protrudes axially over a first end face (12) of the cam roller (3) and up to the one side wall (6) of the lever (2) is sufficient that the needle ring (10) at its second end (10b) substantially with a second end face (14) of the cam roller (3) closes and that between the second end (10b) of the needle ring (10) and the side wall (5) facing this a spacer sleeve (15) is arranged.

Drag lever according to claim 1, characterized in that the lever (2), based on its longitudinal center plane is formed symmetrically.

3. drag lever according to claim 1, characterized in that the spacer sleeve (5) is made of a sliding bearing material.

Drag lever according to claim 1, characterized in that an inner race (22) for the needles (1 1) of the needle ring (10) on one on the axle pin (23) arranged inner ring (21) is formed which substantially with the length of the needle ring (0) protrudes on one side over the cam roller (3).

Drag lever according to claim 1, characterized in that the lever (2), seen in cross section, U-shaped, wherein the side walls (5 and 6) by a transverse wall (4) are interconnected, in one for receiving the cam roller (3) serving recess (9) is arranged.

Drag lever according to claim 5, characterized in that the transverse wall (4) in the region of the projecting first end (10a) of the needle ring (10) has a bulge (17) which extends to the side wall (6) and their on a longitudinal axis of the Achsbolzens (23) referred radius is greater than a radius of an outer raceway (20) on the outer ring (18) of the cam roller (3).

Drag lever according to claim 1, characterized in that the lever (2) is designed as a chipless manufactured sheet metal part.

Drag lever according to claim 5, characterized in that the transverse wall (4) of the U-shaped lever (2) facing away from the open profile of the lever (2) lateral surface with a cap (8) and the valve stem support (7) is provided.

9. drag lever according to claim, characterized in that the a- xiale dimension of the needle ring (10) by 30% to 60% greater than the width of the cam roller (3).

10. drag lever according to claim 1, characterized in that the drag lever is provided for a switchable valve train, in which on the camshaft at least two via an actuating element axially displaceable cams with different cam contours are arranged net, which optionally on an outer Nockenanlauffläche (19) of the

Roll off the cam roller (3).