DE102008036056A1 - Cam follower e.g. rocker arm, for valve train of internal-combustion engine, has outer ring and inner ring that are in sliding contact with each other, and rolling body set arranged between inner ring and bolt - Google Patents

Abstract

The follower (1) has a cam roller (5) arranged between side walls (7) of a housing (4) and supported on a bolt (8) overtensioning the side walls. An outer ring, a rolling body set and the cam roller comprising an inner ring are designed as a combined sliding-roller bearing. The outer ring and the inner ring are in sliding contact with each other, and the rolling body set is arranged between the inner ring and the bolt. The rolling body set is designed a needle ring that comprises a cage and a needle guided into the cage.

Description

Field of the invention

The The invention relates to a cam follower for a valve train an internal combustion engine. The cam follower comprises a housing and one disposed between side walls of the housing Cam roller, which spans on one of the sidewalls Bolt mounted and with an outer ring, a rolling element set and an inner ring formed as a combined sliding-rolling bearing is.

Background of the invention

Such a cam follower is considered from the considered generic DE 10 2004 002 290 A1 out. The cam roller of the cam follower embodied therein as a drag lever is - when viewed in the radially inward direction - composed of an outer ring, a needle set and an inner ring. The outer circumferential surface of the outer ring is in contact with a cam of a camshaft to transmit the stroke of the cam to a gas exchange valve. The inner circumferential surface of the outer ring and the outer circumferential surface of the inner ring serve as raceways for the needle set, while the inner circumferential surface of the inner ring is slidably mounted on a spanning the side walls of the finger lever bolt.

One significant advantage of a sliding rolling bearing thus formed is that the diameter of the bolt in accordance with small height of the side walls of the housing can be chosen comparatively small, without the permissible surface pressures on the rolling elements and on the bolt thanks to the in between arranged and the diameter of the rolling element inner raceway to exceed increasing inner ring.

adversely However, in such a sliding rolling bearing is on the one hand the correspondingly small slide bearing diameter between inner ring and bolts, so that due to lower sliding speeds the Danger of insufficient or unstable lubricating film structure in the plain bearing. On the other hand, the high precision requires to be produced inner surface of the small diameter Inner ring a tool-related costly grinding process.

Object of the invention

Of the The present invention is therefore based on the object, a To further develop cam followers of the type mentioned above, on the one hand a stable and sustainable lubricating film structure is guaranteed in the sliding bearing and that on the other hand the Inner ring as part of the sliding bearing inexpensive to produce is.

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. Accordingly, the outer ring and the inner ring in Sliding contact with each other and the Wälzkörpersatz be arranged between the inner ring and the bolt.

By those compared to the cited prior art as it were radially reversed arrangement of sliding and rolling bearings can due to the now comparatively large slide bearing diameter a favorable lubricating film structure in plain bearings at the same time cost-effective manufacturability of the combined sliding rolling bearing be ensured.

In Further development of the invention, it is provided that the rolling element set as out of a cage and needles in it existing needle ring is formed. By using a such pinion can the internal friction of the cam roller compared to the usual with conventional cam rollers Cageless needle bearing with circumferentially immediately consecutive needles continue to be reduced.

Furthermore the outer ring should have a smaller wall thickness than having the inner ring. For a given outside diameter the cam roller allows this embodiment an additional Increase of the slide bearing diameter in favor of an even higher Sliding speed and a further simplified manufacturability the sliding bearing surfaces. In addition, opened a lot of room for maneuver the diameter dimensioning of the inner ring and the Wälzkörpersatzes. So can, for example, given external diameters the cam roller, the bolt and the rolling elements a thick-walled and therefore particularly stiff inner ring in favor an increased life of the rolling element be used. Furthermore, given external diameters the cam roller and the bolt one for the life the Wälzkörpersatzes suitable diameter adjustment the outer race of the rolling element set running on the inner ring and the rolling elements are made. One in this particularly preferred wall thickness ratio s from outer ring to inner ring is 0.5 ≤ s <1.

Finally, the cam follower should be a drag lever or a rocker arm. Such levers are those skilled in the art as pivotally mounted transmission elements between cam and gas exchange valve known. These differ in kinematic terms by the location of their storage: in contrast to centrally mounted rocker levers cam followers are mounted at their end portions. Nevertheless, the invention can also be applied to linearly guided roller tappets.

Brief description of the drawings

Further Features of the invention will become apparent from the following description and from the drawings, in which an embodiment of the Invention is shown. Show it:

1 a drag lever with cam roller in longitudinal section and

2 a sectional view of the cam roller according to 1 ,

Detailed description the drawings

In 1 is an inventive cam follower 1 disclosed for a valve train of an internal combustion engine. The cam follower 1 is designed as a drag lever, which in a known per se at its first end portion 2 is mounted on a stationary support arranged in the internal combustion engine ball joint and with its second end portion 3 a gas exchange valve actuated. The rocker arm 1 has a housing made of sheet material in a cold forming process 4 and a cam roller 5 for low-friction picking up a cam of a camshaft. The one in a middle section 6 between side walls 7 of the housing 4 arranged cam roller 5 is on one of the side walls 7 spanning bolts 8th stored, in mutually aligned receiving bores of the side walls 7 is held by caulking its bolt ends.

As it incorporates 2 with the cam roller shown in section 5 becomes clear, this is designed as a combined sliding-rolling bearing and comprises in radially inward order an outer ring 9 , an inner ring 10 and a rolling element set 11 , The rolling element set 11 is here as out of a cage 12 and needles guided in it 13 existing needle ring formed whose outer raceway in the inner ring and its inner race on the bolt 8th runs.

The radial wall thickness of the on the inner ring 10 slidably mounted outer ring 9 is in favor of high sliding speeds and a rigid inner ring 10 significantly smaller than that of the inner ring 10 , In the embodiment shown here with an outer diameter of the cam roller 5 of 17 mm are the wall thickness of the outer ring 9 1.0 mm and the wall thickness of the inner ring 10 2.0 mm. An indicated with s wall thickness ratio of outer ring 9 to inner ring 10 is therefore s = 0.5, ie at the boundary of a preferred range with 0.5 ≦ s <1.

1

cam follower

2

first end

3

second end

4

casing

5

cam roller

6

midsection

7

Side wall

8th

bolt

9

outer ring

10

inner ring

11

rolling element

12

Cage

13

needle

s

Wall thickness ratio

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 102004002290 A1 [0002]

Claims (5)

Cam follower ( 1 ) for a valve train of an internal combustion engine, with a housing ( 4 ) and one between side walls ( 7 ) of the housing ( 4 ) arranged cam roller ( 5 ), which on one the side walls ( 7 ) spanning bolts ( 8th ), wherein the one outer ring ( 9 ), a rolling element set ( 11 ) and an inner ring ( 10 ) comprehensive cam roller ( 5 ) is designed as a combined sliding-rolling bearing, characterized in that the outer ring ( 9 ) and the inner ring ( 10 ) are in sliding contact with each other and that the rolling element set ( 11 ) between the inner ring ( 10 ) and the bolt ( 8th ) is arranged. Cam follower ( 1 ) according to claim 1, characterized in that the rolling element set ( 11 ) than from a cage ( 12 ) and needles guided therein ( 13 ) existing needle ring is formed. Cam follower ( 1 ) according to claim 1, characterized in that the outer ring ( 9 ) has a smaller wall thickness than the inner ring ( 10 ) having. Cam follower ( 1 ) according to claim 3, characterized in that for a wall thickness ratio s of outer ring ( 9 ) to inner ring ( 10 ): 0.5 ≤ s <1. Cam follower ( 1 ) according to claim 1, characterized in that it is in the cam follower ( 1 ) is a towing or rocker arm.