Cam follower for a valve train of an internal combustion engine

Abstract

A cam follower for a valve train of an internal combustion engine, the cam follower being formed as a lever, which is U-shaped in cross-section, and produced from steel sheet without machining, and which has a floor wall (3) and lateral walls (4 and 5) extending therefrom, wherein a valve stem support (10) is disposed as a groove (11) at one end of the lever in a surface of the floor wall (3) facing away from the lateral walls (4 and 5). Lateral guide walls (12 and 13) of the valve stem support (10) are formed by chipless shaping so as to extend from and counter to the lateral walls (4 and 5) and are connected to a support wall (14) that forms a valve stem support surface (10a). The valve stem support surface (10a) extends in a first plane (10b), which is spaced from a second plane (16a), which extends through an internal transition (15, 16) between the lateral walls (4 and 5) and the adjacent guide walls (12 and 13), in the direction of ends (19, 20) of the lateral walls (4 and 5). In order to reduce stress and resulting cracks, an inner radius R is provided at the transition (15 and 16), by which radius a free space (17, 18) is created between the lateral wall (4, 5) and the guide wall (12, 13), which free space narrows towards the end (19, 20) of the respective lateral wall (4, 5).

Claims

1. A cam follower for a valve train of an internal combustion engine, comprising viewed in cross section, a U-shaped lever made from sheet steel in a non-cutting process including a base wall and side walls extending from said base wall, wherein a valve stem support formed as a groove is provided on one end of the lever in a surface of the base wall facing away from the side walls, the valve stem support includes side guide walls formed by a non-cutting shaping process extending from and counter to the side walls and are connected to a support wall forming a valve stem support surface, the valve stem support surface extends in a first plane that is spaced apart from a second plane extending through an inner transition between the side walls and the adjacent guide walls in a direction of free ends of the side walls, at the transition, an inner radius R is provided by which a free space is created between each of the side walls, and the guide walls and said free space narrows in the direction of the free end of the respective side wall, wherein the inner radius R and the free space are formed as a common indentation in the inner transition, in the side wall, and in the guide wall.

2. The cam follower according to claim 1, wherein the respective free space narrows up to a contact of the respective guide wall on the respective side wall.

3. The cam follower according to claim 1, wherein the free space has, in an area in which the inner radius R connects, a width B of 0.6 mm and the inner radius R0.3 mm.

4. The cam follower according to claim 1, wherein the free space has a droplet-shaped contour.

5. The cam follower according to claim 1, wherein the lever is constructed as a rocker arm or finger lever provided with a roller pocket for a cam roller.

6. A cam follower for a valve train of an internal combustion engine, comprising viewed in cross section, a U-shaped lever made from sheet steel in a non-cutting process including a base wall and side walls extending from said base wall, wherein a valve stem support formed as a groove is provided on one end of the lever in a surface of the base wall facing away from the side walls, the valve stem support includes side guide walls formed by a non-cutting shaping process extending from and counter to the side walls and are connected to a support wall forming a valve stem support surface, the valve stem support surface extends in a first plane that is spaced apart from a second plane extending through an inner transition between the side walls and the adjacent guide walls in a direction of free ends of the side walls, at the transition, an inner radius R is provided by which a free space is created between each of the side walls, and the guide walls and said free space narrows in the direction of the free end of the respective side wall, wherein the respective free space opens into a gap between the side wall and the guide wall, and the free space has, in an area in which the inner radius R connects, a maximum width that is at least 5 times a width of the gap.

7. A method for the non-cutting production of a cam follower comprising a lever formed from sheet steel, said lever is provided for a valve train of an internal combustion engine and being formed with an essentially a U-shaped cross section with a base wall and side walls extending essentially perpendicular to the base wall, and a valve stem support provided on one end of the lever is formed as a groove in the base wall, having side guiding walls formed by a non-cutting shaping process, starting from the side walls, extending opposite to said walls, and are connected to a support wall forming a valve stem support surface, the valve stem support surface extending in a first plane that is spaced apart to a second plane extending through an inner transition between the side walls and the adjacent guiding walls in the direction of free ends of the side walls the method comprising in a first processing step, punching a blank out from the sheet steel, in a second processing step, embossing two grooves with a blank radius R.sub.R in a longitudinal direction of the blank in a surface of the blank, shaping the blank in a third processing step for the production of said U-shape, and in a fourth processing step, embossing the groove in the base wall, creating a transition from each of the side walls to the base wall at the two grooves, wherein, due to the embossed blank radius R.sub.R, said transition is formed with an inner radius R and a free space that has a drop-shaped contour, viewed in a cross section of the lever.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For further explanation of the invention, reference is made to the drawing in which an embodiment is shown simplified. Shown are:

(2) FIG. 1 a perspective view of a rocker arm according to the invention with a cam roller arranged in this arm,

(3) FIG. 2 a section through the rocker arm according to FIG. 1 along line II-II,

(4) FIG. 3 a perspective representation of a blank punched out from sheet steel for producing a rocker arm according to FIGS. 1 and 2,

(5) FIG. 4 a cross section through the blank after the embossing of grooves in its surface,

(6) FIG. 5 a perspective view of the rocker arm unfinished part, after which the blank provided with the grooves has been shaped into the U-shape of the rocker arm, and

(7) FIG. 6 as a cross section through a rocker arm that shows an enlarged view in the area of a side wall, a guiding wall, and a free space.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(8) In FIG. 1, a rocker arm is designated with 1 that holds a cam roller 2 in the region of its center. Here, the rocker arm 1 has a U-shape design and has a base wall 3 and side walls 4 and 5. In each of the side walls 4 and 5 there is a hole 6, wherein, in these holes 6, of which only one is visible in the figure, a bearing pin 7 is fixed on which the cam roller 2 is supported so that it can rotate by means of a needle bearing not shown in more detail. On a first end 8, the rocker arm 1 has a dome that is not shown in more detail and by which the rocker arm 1 can be guided so that it can pivot on a support element, wherein this not-shown support element that is advantageously provided with a hydraulic valve lash compensation device is mounted on a cylinder head of the internal combustion engine.

(9) A second end 9 of the rocker arm 1 has a valve stem support 10 with a valve stem support surface 10a. This valve stem support 10 consists of a groove 11 that is slightly wider than a diameter of the not-shown gas exchange valve to be actuated by the rocker arm. As can be seen in FIG. 1, the groove 11 is produced by means of a non-cutting shaping process in the base wall 3, wherein guiding walls 12 and 13 extend from the base wall 3 and the side walls 4 and 5, respectively, and connect to a support wall 14. For the use of the rocker arm 1 within a valve train of an internal combustion engine, this support wall 14 contacts one end of the valve stem of the corresponding gas exchange valve.

(10) As can be seen in FIG. 1, the two guiding walls 12 and 13 extend essentially parallel to the adjacent side walls 4 and 5. Here, at least one guiding surface of each of the two guiding walls 12 and 13 are arranged essentially parallel to the outer surfaces of the side walls 4 and 5, as still to be explained in connection with FIG. 2. From FIG. 1 it was already described that, in the area of a transition 15 and 16 from each side wall 4 and 5 to the guiding walls 12 and 13, at which these are deformed by 180 relative to each other, free spaces 17 and 18 are provided that each have an inner radius R.

(11) For a more detailed description of the second end 9 of the rocker arm forming the valve stem support 10, refer to FIG. 2, in which a section through the lever 1 in this region is shown. In this figure, the same reference numbers are used as those for the description of FIG. 1. From FIG. 2, it can be seen, first, that between a plane 10b set through the valve stem support 10a, and a plane 16a set through the transition 16, a distance A is provided, so that the lever has a correspondingly large depth of the groove 11. From this figure according to FIG. 2 it is also clearly seen that, in the region of the transitions 15 and 16, between the side walls 4 and 5 and also the guiding walls 12 and 13, free spaces 17 and 18 are formed that, viewed in cross section, have a drop-shaped contour. Here, each free space 17 and 18 are formed in the lower region in which the non-cutting shaping process is performed, with a relatively large inner radius R. Each of these free spaces 17 and 18 extends to a point in the direction of ends 19 and 20 of the side walls 4 and 5, starting from the inner radius R. Here, each free space 17 and 18 transitions into a gap 21 and 22, respectively. Instead of these gaps 21 and 22, the rocker arm 1 can naturally also have a design such that the side walls 4 and 5 contact the guide walls 12 and 13.

(12) The other FIGS. 3, 4, and 5 show the formation of the blank used for the production of the rocker arm according to FIGS. 1 and 2 in the individual steps of the production process. Here, FIG. 3 shows a blank 23 punched out from sheet steel that already has a pocket 24 for the later holding of the cam roller 2 used according to FIG. 1. According to the invention, two grooves 25 and 26 are embossed with a blank radius R.sub.R in this blank 23 according to FIG. 4, wherein then the blank 23 is shaped into its U-shape. This formation of the blank is shown in FIG. 5 in which the U-shaped blank produced in this way is shown rotated by 180 relative to FIG. 4. In this U-shaped blank, the grooves 25 and 26 are visible, in turn.

(13) Then the valve stem support 10 is produced in this blank, which happens through an embossing process. Here, the shape of the rocker arm 1 shown according to FIGS. 1, 2, and 6 is produced, wherein this rocker arm is provided with free spaces 17 and 18 and an inner radius R bordering these spaces due to the grooves 25 and 26 provided in the blank. Here, from FIG. 6 it can be seen that the free space 17 has a width B. This should be greater than or equal to 0.6 mm according to the invention. FIG. 6 also shows, in agreement with FIG. 2, the inner radius R, under which the corresponding side wall 4 transitions into the guiding wall 12 and should be greater than or equal to 0.3 mm according to the invention. Finally, this enlarged illustration also shows the two planes 10b and 16a that should be spaced apart from each other by the dimension A. The plane 10b is here adjacent to the two ends 19 and 20 of the side walls 4 and 5, so that the rocker arm is provided with a relatively deep groove 11.

(14) The rocker arm 1 according to the present invention has a high durability, so that the crimped fold formations that occur in the prior art are not produced during the formation of the valve stem support 10 formed as a groove 11 in the region of the transitions 15 and 16 from the side walls 4 and 5 into the guiding walls 12 and 13. Thus, advantageously, the stresses that occur in this region can be minimized so that, according to the invention, the risk of a formation of cracks is significantly reduced.

LIST OF REFERENCE NUMBERS

(15) 1 Rocker arm 2 Cam roller 3 Base wall 4 Side wall 5 Side wall 6 Hole 7 Rearing pin 8 First end of 1 9 Second end of 1 10 Valve stem support 10a Valve stem support surface 10b Plane 11 Groove 12 Guide wall 13 Guide wall 11 Support wall 15 Transition 16 Transition 16a Plane 17 Free space 18 Free space 19 End of side wall 1 20 End of side wall 5 21 Gap 22 Gap 23 Blank 24 Roller pocket 25 Channel 26 Channel R Inner radius R.sub.R Unshaped part radius of 25 and 26 A Distance between 10b and 16a B Width of 17 and 18