DE102008022601A1 - Lever-type cam follower i.e. rocker arm, for operating gas exchange valve of internal-combustion engine, has base part and side walls formed concave at its connection points in elevation direction of joint-socket - Google Patents

Abstract

The cam follower (1) has a longitudinal lever body (4) made of sheet metal, and a base part (13) for connecting side walls (12). The base part has a dome-shaped joint-socket (14) that is elevated between the side walls, where the joint-socket serves for pivotable support of the cam follower on a joint head (7) that is mounted in an internal-combustion engine (3). The base part and the side walls are formed concave at its connection points in an elevation direction of the joint-socket, where the points run within a region of a transverse centre plane of the joint-socket.

Description

Field of the invention

The The invention relates to a lever-type cam follower for actuation a gas exchange valve of an internal combustion engine, with an elongated, formed from sheet metal lever body, the side walls and a connecting this bottom part with a between the Sidewalls elevating dome-shaped socket has, which for the pivotable support of the cam follower on serves a resting in the internal combustion engine rod end.

Background of the invention

Such cam followers are in particular as end-mounted rocker arms for a long time in large series use and are in the patent literature, for example in the DE 198 10 462 A1 , of the US 5,535,641 and the EP 1 157 193 B1 described. A cam follower in the form of a rocker arm, which is supported centrally on a pivotally mounted in the engine hinge head, goes out of the EP 1 119 689 B1 out.

The width of the aforementioned cam followers is determined in each case by the size of the joint socket and its wall thickness and the wall thickness of the side walls extending with more or less spacing. The size of the socket again results from the diameter of the generally spherical condyle and is referred to below as the nominal diameter of the socket. Compared to that in the DE 198 10 462 A1 disclosed drag lever whose lever body in the region of the socket has a significant broadening, which is in the US 5,535,641 proposed drag lever already formed considerably narrower. However, in order to be able to reshape the socket with the required dimensional accuracy, it is proposed in this document to locally reduce the wall thickness of the side walls in the region of the socket. Despite relatively narrow-built lever body allows such a design around the socket pan around the bottom part, which is essential according to this document to achieve the required deformation accuracy of the socket.

The Indian EP 1 157 193 B1 disclosed drag lever is - based on the nominal diameter of the socket - extremely narrow design formed. This is from the 3 . 4 and 7 this document in which the socket and the side walls seem to be fused together. However, this document no specific information about a forming process can be removed, which allows such a configuration of the lever body in the region of the socket.

investigations the applicant to narrow-built rocker arms with the joint socket closely spaced sidewalls have been shown to do so the deformation of the lever body at the joints the bottom part and the side walls to material tapers The joint socket can come, which occasionally associated with cracks and wrinkles. This, in the manufacture of the lever body in the rule not obvious and only with elaborate, non-destructive Quality controls safely detectable component failure the fatigue strength of the cam follower can be significant impaired. As is known, premature failure the cam follower due to breakage in the worst case to a complete Destruction of the internal combustion engine lead.

Object of the invention

Of the The present invention is therefore based on the object, a cam follower of the aforementioned type so that this - based on the nominal diameter of the socket - if possible narrow construction is executed. At the same time, the lever body reliable, d. H. free of material defects, and with the required Form accuracy be largely cost-neutral formable.

Summary of the invention

The Solution to this problem arises from the characterizing Features of claim 1, while advantageous developments and embodiments of the invention, the dependent claims are. According to the bottom part and the side walls at their joints, in the area of a transverse median plane run the socket, in elevation direction of the socket be formed concave. A major difference to those in the cam followers described in the introduction mentioned Consequently, in that the opening of the socket delimiting the peripheral edge not in a plane, but because of the concave recesses locally recessed in the area of the side walls. This geometric structure the lever body leads to a considerable improvement the material flow during forming, so that the aforementioned Materialverjüngungen the joint socket with the associated risk of cracks and Creases can be effectively prevented.

In addition, it should also be mentioned that the inner circumferential surface of the joint socket available for contact with the condyle is locally reduced on account of the concave indentations, but in this way the function of the joint contact, including the sealing function, is reduced Lubricant leading rod ends is not or at most negligible. This results from the kinematics of the lever-type cam follower, which is loaded only comparatively small in the transverse direction.

In Further development of the invention, it is provided that the depth of concave indentations 8% to 16% of the nominal diameter of the socket is. Accordingly, for example, in a condyle with a nominal diameter of 8.5 mm the depth of the indentations 0.68 to 1.36 mm. A particularly preferred depth gauge is in this condyle in the range between 1 and 1.2 mm.

in the With regard to the lowest possible notch effect as well as on a long service life of the forming tool should also the concave indentations rounded edge-free and in viewing direction the transverse center plane be formed in a circular arc.

One especially slim-fitting cam follower is also present when in the area of the transverse median plane of the socket the inside distance the side walls smaller than the sum of the nominal diameter and two wall thicknesses of the socket.

In A preferred application of the invention is the cam follower Finally, be designed as a drag lever, wherein the Lever body actuates the gas exchange valve with its first end section, is supported at its second end portion on the condyle, and in its central portion with a preferably formed as a role Cam contact surface is provided. Nevertheless, the cam follower Alternatively, be designed as a rocker arm, with its first End section actuates the gas exchange valve, at its second End portion is provided with a cam contact surface and is supported in its middle section on the condyle.

Provided it is possible and appropriate the aforementioned features and embodiments of the invention also be combined with each other as desired.

Brief description of the drawings

Further Features of the invention will become apparent from the following description and from the drawings, in which the invention with reference to a Drag lever trained cam follower compared to the state the technique is shown. Unless otherwise stated, are the same or functionally identical features or components provided with the same reference numbers. Show it:

1 a drag lever according to the invention in longitudinal section;

2 one according to 1 executed drag lever in cross-section through the joint socket as a grinding pattern;

3 a known cam follower valve train;

4 a microsection of a known finger lever in analogy to 2 and

5 the detail in 4 in greatly enlarged representation.

Detailed description the drawings

The starting point of the description is the in 3 illustrated section of a known cam follower valve train with a trained as a finger lever lever-like cam follower 1 for actuating a gas exchange valve 2 an internal combustion engine 3 , The rocker arm 1 has an elongated lever body 4 on that with its first end section 5 the gas exchange valve 2 pressed, at its second end section 6 on one in the internal combustion engine 3 resting rod end 7 a support element 8th supports and in its middle section 9 with a roller bearing roller 10 is provided, which serves as a contact surface for a cam 11 a camshaft is used. The formed from sheet metal lever body 4 has two spaced-apart side walls 12 and at its second end portion 6 one the side walls 12 connecting floor part 13 with one in between the side walls 12 uplifting dome-shaped socket 14 for pivotal support on the condyle 7 on.

In 4 and as an enlarged detail view in 5 is a cross section through the socket 14 on the basis of a micrograph of an executed, comparatively narrow lever body 4 displayed. Good to see is the material rejuvenation of the socket 14 in the area of the dash - dotted marked detail in 5 is shown greatly enlarged. As stated at the outset, this material taper can be accompanied by the formation of cracks as indicated by the arrow, which in individual cases leads to premature failure of the drag lever 1 due to a breakage of the lever body 4 leads.

This risk of failure is in a drag lever according to the invention 1 as he is in the 1 and 2 is reduced to a minimum. This is achieved by the fact that the bottom part 13 and the side walls 12 at their joints, in the area of with 15 designated transverse median plane of the socket 14 run, in survey direction of the socket 14 are formed concave. Compared to the known state of the art lead the indentations 16 to that the circumferential edge 17 at the opening of the socket 14 does not run in a plane, but locally in the area of the side walls 12 is reset by the depth designated T. In the present case, the depth T of the indentations 16 maximum 1.2 mm. In a joint socket 14 with a nominal diameter D of 8,5 mm, which corresponds to the diameter of the condyle (see 3 ), the maximum depth T is therefore about 14% of the nominal diameter D.

Out 1 also shows that the indentations 16 in favor of a low notch effect at the peripheral edge 17 free of angular transitions and, in the direction of the transverse median plane 15 considered, are circular arc.

In analogy to 4 shows 2 a microsection of the lever body 4 one according to 1 executed towing lever 1 , Clearly recognizable is the shape of the tapered material tapers and scratches free joint socket 14 thanks to the indentations 16 reliable in this form can be produced. Thus, the narrow construction of the in 4 illustrated lever body 4 at the least risk of failure of the finger lever 1 to be kept. In the present case, a narrow construction means that in the area of the transverse center plane 15 the joint socket 14 the designated L inner spacing of the side walls 12 smaller than the sum of the nominal diameter D and two wall thicknesses marked S of the joint socket 14 is.

1

lever-type Cam follower / rocker arm

2

Gas exchange valve

3

Internal combustion engine

4

lever body

5

first End portion of the lever body

6

second End portion of the lever body

7

joint head

8th

supporting

9

midsection of the lever body

10

Role / cam contacting surface

11

cam

12

Side wall

13

the bottom part

14

socket

15

Transverse center plane the joint socket

16

concave indentation

17

circumferential edge the joint socket

T

depth the indentation

D

Nominal diameter the joint socket

L

padding the side walls

S

Wall thickness the joint socket

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 19810462 A1 [0002, 0003]
• US 5535641 [0002, 0003]
• - EP 1157193 B1 [0002, 0004]
• - EP 1119689 B1 [0002]

Claims (5)

Lever-like cam follower ( 1 ) for actuating a gas exchange valve ( 2 ) an internal combustion engine ( 3 ), with an elongated, formed of sheet material lever body ( 4 ), the side walls ( 12 ) and the side walls ( 12 ) connecting floor part ( 13 ) with one between the side walls ( 12 ) elevating dome-shaped socket ( 14 ), which for pivotally supporting the cam follower ( 1 ) on one in the internal combustion engine ( 3 ) resting rod end ( 7 ), characterized in that the bottom part ( 13 ) and the side walls ( 12 ) at their joints, which are in the range of a transverse median plane ( 15 ) of the socket ( 14 ), in elevation direction of the socket ( 14 ) are concave molded. Cam follower ( 1 ) according to claim 1, characterized in that the depth (T) of the concave recesses 8% to 16% of the nominal diameter (D) of the socket ( 14 ) is. Cam follower ( 1 ) according to claim 1, characterized in that the concave recesses ( 16 rounded edge-free and in the viewing direction of the transverse median plane ( 15 ) are formed in a circular arc. Cam follower ( 1 ) according to claim 1, characterized in that in the region of the transverse median plane ( 15 ) of the socket ( 14 ) the inside distance (L) of the side walls ( 12 ) smaller than the sum of the nominal diameter (D) of the socket ( 14 ) and two wall thicknesses (S) of the socket ( 14 ). Cam follower ( 1 ) according to claim 1, characterized in that the cam follower ( 1 ) is designed as a drag lever, wherein the lever body ( 4 ) with its first end section ( 5 ) the gas exchange valve ( 2 ), at its second end portion ( 6 ) on the condyle ( 7 ), and in its middle section ( 9 ) with a preferably designed as a roller cam contact surface ( 10 ) is provided.