GB2249153A

GB2249153A - Shock absorbing apparatus

Info

Publication number: GB2249153A
Application number: GB9119994A
Authority: GB
Inventors: Klaus Reisdorf
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 1990-09-20
Filing date: 1991-09-19
Publication date: 1992-04-29
Anticipated expiration: 2011-09-19
Also published as: GB2249153B; GB9119994D0; FR2667019B1; DE4130112A1; FR2667019A1

Abstract

A shock absorbing apparatus (1) for motor vehicle axles has a rubber-metal bearing (4) on the wheel end comprising a first bearing sleeve (5), a second bearing sleeve (6) and a middle, third bearing sleeve (7) which is connected by way of an inner annular rubber element (8) to the first bearing sleeve (5) and by way of an outer annular rubber element (9) to the second bearing sleeve (6). A spring plate (10) for supporting the helical spring (3) of the apparatus is secured to the middle, third bearing sleeve (7). <IMAGE>

Description

1 2249153

-IDESCRIPTION SHOCK ABSORBING APPARATUS

The invention relates to shock absorbing apparatus. More particularly it relates to shock absorbing apparatus for motor vehicle axles, comprising a telescopic shock absorber and a helical spring or the like surrounding the telescopic shock absorber.

Shock absorbing apparatus of this type are disclosed in DE-OS-3826301 and in DE-OS-3928134.

Shock-absorber legs of a motor vehicle are subjected to forces acting on the wheels of the motor vehicle which induce bending stress. Hence at the sliding components of their telescopic shock absorber, (that is on the damper piston and on the piston rod bearing) transverse forces occur causing friction, in particular static friction, to be greatly increased. This leads to reduced performance of the telescopic shock absorber. In particular on good roads with only comparatively little surface unevenness, the damping action of a telescopic shock absorber may be prevented completely, so that oscillations induced by impacts between a wheel and the road surface are transmitted, at least temporarily, in a seemingly uncushioned or undamped manner to the vehicle body. This can cause the steering and the driver comfort of the vehicle to 1 -2be noticeably impaired. The increased static friction does not generally induce into the lower sliding friction until a certain (breakaway) force is exceeded. This poor response behaviour is generally described using the term ',slip and stick" effect.

It is known (e.g. Hoesch Journal entitled 11Berichte aus Forschung und Entwicklung unserer Werke", Issue 1/67, pages 17 to 22) that undesirably high friction in a shock-absorber leg can in principle be reduced for example by selecting a large min' distance (base length) between the sliding locations of its telescopic shock absorber. However, such a measure requires correspondingly long shock-absorber legs, which cannot be used universally for reasons of space.

It is also known (e.g. from the above Journal and from DE-OS- 14 30 586, DE-OS- 15 05 615, DE-OS15 05 616 and DE-OS- 15 80 480) to reduce friction at the sliding locations and thus to increase response sensitivity of the shock-absorber leg by offsetting either the central axis of the helical screw or the like serving the vehicle suspension with respect to the longitudinal axis of the telescopic shock absorber, in particular eccentrically thereto. Alternatively, the helical spring can, when in use, be prestressed transversely to the longitudinal direction 1 -3of the vehicle. In a further alternative, exterior to the shock absorber, an additional spring device can be provided, which is supported at one end by the vehicle body and at the other end by the cylinder of the telescopic shock absorber. This arrangement generates an external transverse force component.

The inclination or offset of the helical spring or even the arrangement of an additional spring device generating a transverse force component, are, because of generally restricted installation conditions, not always possible.

Shock-absorber leg arrangements are also known from EP-OS 0 064 594. in which the rubber-elastic shock-absorber leg bearings on the body side are formed in such a way that, during oscillationf a rotary movement, which is superimposed on the axial piston rod movement, is forced"upon the piston rod of the telescopic shock absorber. This is intended to reduce the friction forces, in particular in the socalled "dead centres" of the piston rod stroke movement, by avoiding static friction and enforcing sliding friction (piston rod rotation). The outlay on production technology for such rubber-elastic bearings is comparatively high. Moreover, the rubber members of the bearings are very highly stressed. Furthermore, it is difficult to dimension these bearings to a tolerable construction volume so that they can cause a sufficiently large relative rotation even in the case of short, rapid impacts caused by the roadway of good roadways in order to avoid the "slip and stick" effect.

A shock-absorber leg wheel suspension is also known (e.g. DE-OS 39 38 773), in which, in order to reduce the known "slip and stick" effect, on the free end of the piston rod of the telescopic shock absorber of the shock-absorber leg arrangement on the body side, a rigid lever extending transversely to the longitudinal axis of the motor vehicle is rigidly secured. The free end of this lever carries a rubbermetal bearing, whose inner sleeve is readily rotatably mounted on a bearing bolt, which is fixed to the body and is aligned approximately horizontally and in the longitudinal direction of the vehicle. The inner sleeve and outer sleeve and the rubber members of the rubber-metal bearing located therebetween are dimensioned in such a way that a certain cardanic movement is obtained between the inner and outer sleeves. Conventionally, the end of a shock-absorber leg or spring-type shock absorber on the body side is in the form of a pin joint. For the above-mentioned known shock-absorber leg wheel suspension having a lever which is rigidly secured to the piston rod end, -5however, the body would have to be completely differently designed in this region for securing th required horizontal bearing pin.

Even in the case of spring-type shock absorbers comprising a telescopic shock absorber and a helical spring or the like surrounding it, which on the wheel side can be articulated by means of a rubber-metal bearing on the wheel guide member of the rear axle (such as are preferred in the field of non-steered rear axles, comparable difficulties, even though less severe, can occur. These difficulties occur with respect to the response behaviour of the telescopic shock absorber, although spring-type shock absorbers, in contrast to shock-absorber legs, do not take on any actual wheel guide functions.

Against this background,-it is the object of the invention to design a spring-type shock absorber with a minimum amount of outlay in which the response behaviour is improved.

According to the present invention, there is provided a shock-absorbing apparatus for motor vehicle axles, comprising a telescopic shock absorber having a rubber-metal bearing at at least one end and a helical spring surrounding the telescopic shock absorber; wherein the rubber-metal bearing comprises a first bearing sleeve and a second bearing sleeve which is 1 k -6located radially inwardly of the first bearing sleeve and which is connected thereto by way of an annular rubber element, and a third bearing sleeve; wherein the third bearing sleeve is disposed between the first and the second bearing sleeves and is connected by way of an annular rubber element to the first bearing sleeve and by way of an outer annular rubber element to the second bearing sleeve, and a spring plate for supporting the helical spring is secured to the third bearing sleeve.

The two annular rubber elements preferably have different characteristics. Preferably, the outer annular rubber element is substantially softer than the inner annular rubber element.

The invention will now be described by way of example only with reference to the accompanying drawing.

The drawing is a basic representation of a partially sectioned view of a shock absorbing apparatus according to the present invention when installed in a motor vehicle.

A portion of the rear axle of the motor vehicle is shown. For ease of representation only those parts are shown which are essential to an understanding of the present invention, such as the lower part (that is the part on the wheel end) of the shock-absorbing k -7apparatus, 1.

Shock absorbing apparatus 1 comprises a telescopic shock absorber 2, of which only the damper tube can be seen, as well as a helical spring 3, which surrounds the telescopic shock absorber, which serves the spring suspension of the vehicle and which is supported at one end by the vehicle body, (not shown), and at the other end by the wheel carrier 13 or a wheel guide member connected thereto.

The articulation of the shock absorbing apparatus 1 on the wheel side is effected by means of a rubbermetal bearing 4, which has a. first bearing sleeve 5 for securing to the wheel carrier 13 or the wheel guide member, and a second bearing sleeve 6 which is located radially outwardly of the first bearing sleeve 5, and which is connected thereto in a rubberelastic manner. The second bearing sleeve 6 is rigidly secured, for example welded, to the lower end of the damper tube of the telescopic shock absorber 2.

The first bearing sleeve 5 is firmly screwed by means of afastening screw 11 to bearing side walls 12, which can be part either of the wheel carrier 13 or of one of the wheel guide members. In the embodiment shown they are secured to the free end of a longitudinal link, which in turn may, of course, also be part of a known composite guide axle or coupling guide axle.

In such a configuration, the rubber-metal bearing 4 is aligned so that the longitudinal axis of the first bearinq sleeve 5 is approximately parallel to the axes of rotation or pivoting of the associated axle guide, i.e. approximately along a transverse axis through the vehicle.

In conjunction with inclined or even diagonal links, the rubber-metal bearing 4 would have to be aligned correspondingly differently.

In contrast with known spring-type shock absorber arrangements, in the apparatus of the present invention there is disposed between the first and the second bearing sleeves 5 and 6 of the rubber-metal bearing 4, a middle, third bearing sleeve 7. This is connected radially inwardly by way of an inner annular rubber element 8 to the first bearing sleeve 5 and radially outwardly by way of a second annular rubber element 9 to the outer bearing sleeve 6. Preferably, these rubber elements are moulded to the sleeves.

On the middle, third bearing sleeve 7 there is secured, by welding, a spring plate 10, on which the lower end (that is the end on the wheel side) of the helical spring 3 is supported. In contrast with known springtype shock absorber arrangements, the ends of the helical spring 3 and the telescopic shock absorber I X 2 on the wheel side are thus no longer jointly rigidly articulated to the wheel carrier 13 or the corresponding wheel guide member, but are largely decoupled from one another.

The helical spring 3 is supported by its spring plate 10 by way of inner annular rubber element 8 torsionally, radially and cardanically resiliently on the first bearing sleeve 5 and thus on the bearing side walls 12 or the wheel carrier 13. The telescopic shock absorber 2, which is rigidly connected to the second bearing sleeve 6, is resiliently supported in turn by way of the outer annular rubber element 9 which acts correspondingly resiliently on the middle, third bearing sleeve.

Finally, two rubber-metal bearings are provided in cylindrical form, which are inserted into one another coaxially. By virtue of suitable dimensioning of the two annular rubber elements.8,9, it can advantageously be ensured that mutual -influencing or superimposition of induced forces and moments are reduced to a minimum.

Preferably, the inner rubber element 8, by way of which the helical spring 3 is supported by its spring plate 10, is comparatively hard, and the radially outer, second rubber element 9, by way of which the telescopic shock absorber 2 is supported, is f k -10comparatively very soft.

In the spring-type shock absorber according to the present invention, the spring plate 10 is thus relatively pivotable with respect to the damper tube of the telescopic shock absorber. In this way, during oscillation of the wheel due to an uneven road surface, moments introduced by way of the rubber-metal bearing 4 into the shock absorbing apparatus 1 are substantially transmitted by way of the helical spring 3 into the vehicle body (not shown) whereby the helical spring is deformed. Therefore only a very small proportion of these bending moments act upon the damper tube and thus on the piston rod of the telescopic shock absorber. Such small introductions of moment result in correspondingly small transverse forces acting on the damper piston and on the piston rod guide. Thus a desired particularly good response behaviour of the telescopic shock absorber 2 is achieved.

On the body side, the helical spring 3 and the piston rod of the telescopic shock absorber 2 are, in a manner known for example from DE-OS 39 28 134r supported or articulated on the vehicle body completely separately from one another.

By virtue of the present invention it is also A -11possible to make the piston rod of the telescopic shock absorber weaker than was previously the case, since the piston rod is subjected to relatively little bending stress.

Furthermore, the proposed bearing of the present invention is structurally very simple and can be made without special outlay in terms of production technology.

A A

Claims

-12CLAIMS

1. A shock-absorbing apparatus for motor vehicle axles, comprising a telescopic shock absorber having a rubber-metal bearing at at least one end and a helical spring surrounding the telescopic shock absorber; wherein the rubber-metal bearing comprises a first bearing sleeve and a second bearing sleeve which is located radially inwardly of thefirst bearing sleeve and which is connected thereto by way of an annular rubber element, and a third bearing sleeve; wherein the third bearing sleeve is disposed between the first and the second bearing sleeves and is connected by way of an annular rubber element to the first bearing sleeve and by way of an outer annular rubber element to the second bearing sleeve, and a spring plate for supporting the helical spring is secured to the third bearing sleeve.-

2. Shock absorbing apparatus as claimed in claim 1, wherein the inner and outer annular elements have different characteristics.

3. Shock absorbing apparatus as claimed in claim 1 or claim 2, wherein the second annular rubber element is substantially softer than-the first annular rubber element.

4. Shock absorbing apparatus substantially as described herein with reference to the drawing.