GB2100832A

GB2100832A - Vibration absorber in motor vehicle transmission

Info

Publication number: GB2100832A
Application number: GB08207599A
Authority: GB
Inventors: Sivers Rolf Von; Ulrich Layher
Original assignee: Dr Ing HCF Porsche AG
Current assignee: Dr Ing HCF Porsche AG
Priority date: 1981-07-01
Filing date: 1982-03-16
Publication date: 1983-01-06
Also published as: NL8200609A; IT8219830A0; IT1190699B; GB2100832B; DE3125830C1; FR2509001A1; FR2509001B1

Abstract

A vibration absorber 7 is arranged in a support tube 1 of a transaxle unit. The mass 8 of the absorber 7 is held in springs 9, 10 which absorb shearing forces and determine the frequency range of the absorber 7. The springs are held between two concentric rings 11 and 12. <IMAGE>

Description

SPECIFICATION A drive assembly resiliently mounted in a motor vehicle The invention relates to a drive assembly resiliently mounted in a motor vehicle.

German Offenlegungsschrift No. 27 47 225 discloses a vibration absorber for a drive assembly which is held in a support tube by way of resilient support members in the form of rings of square cross-section. Support members of this type tend to harden under compressive stress, as a result of which sufficient energy is no longer withdrawn from the energizing arrangement. Furthermore, the absorber spring characteristic is affected by a deformation of the support members on account of variations in the internal diameter of the support tube to the extent that the absorber spring characteristic is altered by subsequent deformation.

The object of the invention is to provide an improved absorber spring for the arrangement described above, in which the dynamic properties of the fitted spring ensure a specified resonance frequency and a maximum energy reduction is possible.

The present invention consists in a drive assembly resiliently mounted in a motor vehicle, comprising an internal combustion engine positioned towards the front of the vehicle and rigidly connected to a gear unit positioned towards the rear by means of a support tube extending longitudinally of the vehicle, a drive shaft in said support tube and a vibration absorber for suppressing vibration in the assembly as a whole whose absorber mass is formed as a sleeve surrounding the drive shaft in a contact-free manner, said absorber mass being supported on the inner wall of the support tube by absorber springs in end-position seats in the absorber mass in the area of the support tube subject to vibration, the absorber and the absorber springs being pressed into the support tube in a self-supporting manner, each absorber spring comprising a support member held between two bearing rings arranged concentrically in the support tube, the resilience of each support member being such that it absorbs shearing forces in all radial and in longitudinal directions and determines the frequency range of the absorber.

The main advantages achieved by the invention lie in the fact that due to its construction the absorber spring is acted upon no longer by compression but mainly by shearing and it is released from tube and mass tolerances by the bearing rings provided. When the absorber spring is pressed into the tube and on to the absorber mass, hardening no longer occurs, and during the vibration of the absorber mass the annular part of the absorber spring is deformed, which allows the absorber to be set at a very low frequency.

Preferably the resiliently deformable area of the absorber spring is held between two bearing rings which are relatively rigid and provided with a ribbed elastomeric layer. These ribs are constructed in such a way that although on the one hand they take up tolerances of the support tube, on the other hand they are made so hard that the dynamic properties of the absorber are determined solely by the absorber spring. The rigid construction of the two bearing rings has the effect that there is no alteration in the distance between these bearing rings, i.e. compression of the spring, and so the dynamic properties of the spring are retained despite deviation of the internal diameter of the support tube or the mass from the actual dimension and the desired resonance frequency is attained.

The absorber is forced into the support tube by means of a ram. In order that the mass between the absorber springs should not be pressed into the springs and the position of the absorber springs should not be altered, the outer bearing ring is preferably provided with a stop on both its front faces.

In the accompanying drawings:- Fig. 1 is a side view of a drive assembly including an internal combustion engine connected to a gear unit by a support tube; Fig. 2 is a longitudinal section through the support tube with a vibration absorber disposed therein; Fig. 3 is a front view of the absorber spring with an outer and an inner bearing ring; Fig. 4 is a section taken along the line IV--IV of Fig. 3; Fig. 5 is a sectional side view of the absorber spring during a vibration movement, and Fig. 6 is a sectional view showing a further embodiment of an absorber spring.

As shown in Fig. 1, a support tube 1 provides a rigid connection between an internal combustion engine 2 positioned towards the front and a gear unit 3 positioned towards the rear of a vehicle. The unit 3 comprises a change gear and an axle gear.

The internal combustion engine 2 is connected to the rear gear unit 3 by way of a drive shaft 4 positioned in the support tube 1. This drive assembly, known as a "transaxle unit" 5, is mounted on the vehicle body by resilient bearings (not shown). The drive shaft 4 is arranged in the support tube 1 between bearings which are positioned in the assembly as a whole in such a way that bending resonances of the shaft 4 are avoided.

The support tube 1 is provided with one or more vibration absorbers 7 depending on areas of the drive assembly as a whole which are subject to vibration. In the embodiment illustrated there is only one area subject to vibration, so that only a single absorber 7 is provided for suppressing the vibrations.

As shown in greater detail in Fig. 2, the vibration absorber 7 comprises a mass 8 which is supported in the support tube 1 in a freely vibrating manner relative to the drive shaft 4 and to the support tube 1 by way of absorber springs 9 (Fig. 2) and 10 (Fig. 6). The absorber springs 9, 10 are preferably disposed at the same distance a in each instance from the centre of gravity S of the absorber mass 8. The mass 8 of the absorber 7 is in the form of a sleeve which surrounds the drive shaft 4 in a contact-free manner and is supported on the inner wall of the support tube 1 by way of the absorber springs 9, 10. The absorber 7 is pressed into the support tube in a self-supporting manner.

According to the first embodiment shown in Figs. 1 to 5 the absorber spring 9 comprises a resilient support member 1 3 held between two bearing rings 11, 1 2 arranged concentrically in the support tube 1. According to the further embodiment shown in Fig. 6, the two bearing rings 14 and 1 5 have the same length, in contrast to the bearing rings 11 and 12 of the first embodiment and the resilient support member 13 is constructed as shown in Fig. 2.

The resiliency of the support member 1 3 is such that its absorbs shearing forces in all radial and in longitudinal directions and determines the frequency range of the absorber 7. For this purpose it is provided with a kidney-shaped crosssection which comprises an outer rounded area 1 7 and an inner trough-shaped area 1 8. Its peripheral lateral surfaces 19 and 20 (Fig. 1) or 21 and 22 (Fig. 6) are flattened and secured to the outer bearing ring 11 or 14 respectively and the inner bearing 12 or 1 5 respectively by vulcanization or any other method of joining.

In the region of a plane x-x the support member 13 has an annular area which yields in such a way that when subjected to shear forces it is deformable in a defined manner in accordance with the desired frequency position of the absorber 7.

The rounded area 17 of the support member 13 extends approximately as far as an outer plane 23 formed by the two front faces of the bearing rings 11, 1 2 or 14, 1 5 respectively. On their outer peripheral surfaces 24 and 32 the bearing rings 11. 12 or 14, 1 5 respectively are provided in each case with an elastomeric layer in which are formed longitudinally extending ribs 25, 26. These ribs may have an angular shape or, on the other hand, a rounded shape. They are made dynamically rigid in such a way that the characteristic of the resilient support members 1 3 remains unaffected. At the same time the ribs take up tolerances of the tube.

The outer bearing ring 11 or 14 respectively and the inner bearing ring 12 or 1 5 respectively are made deformation-resistant in such a way that a predetermined distance d is maintained between the bearing rings despite inaccuracies in the diameter of the tube so that no alteration can occur in the spring characteristics and hence in the absorbing effect on account of the resilient support member 13 of the absorber spring 9, 10.

According to the first embodiment (Figs. 2 to 5) the support base 28 formed by the outer bearing ring towards the inner surface 29 of the support tube 1 is made longer than the holding base 30 of the inner bearing ring 12 on the absorber mass 8, the two bearing rings 11 and 12 terminating at the outer plane 23. The lateral surface 20 of the resilient support member 13 joined to the inner bearing ring 12 to offset towards the outer plane 23 relative to the lateral surface 1 9 of the support member 1 3 joined to the outer bearing ring 11.

According to the embodiment shown in Fig. 6, both bearing rings 14 and 1 5 are of equal length and overlap one another.

In order that the absorber spring 9, 10 may not occupy a position altering the spring characteristics after insertion into the support tube 1, the inner front face of the outer bearing ring 11 or 14 respectively projects and form an annular stop 31 for the absorber mass 8 corresponding to the external diameter of the bearing ring. In the same way the outer front face of the bearing ring may be provided with a stop, which acts as a stop for a tool, such as a ram, for insertion.

Fig. 5 shows the absorber spring 9 during a vibration movement in the direction of the arrow 33 (Fig. 2) with a vibration path c. The rounded area 17 of the support member 13 is deformed and the lower rounded area 1 7 of the support member 1 3 is extended. The deformed area is folded, so that the rounded portion extends as far as, or beyond, the plane 23. The spring characteristic of the support member is conjointly influenced by the length and position of the two opposite connection surfaces of the support member 13 on the inner surfaces of the bearing rings 11, 1 2 or 14, 1 5 respectively.

Claims

1. A drive assembly resiliently mounted in a motor vehicle, comprising an internal combustion engine positioned towards the front of the vehicle and rigidly connected to a gear unit positioned towards the rear by means of a support tube extending longitudinally of the vehicle, a drive shaft in said support tube and a vibration absorber for suppressing vibration in the assembly as a whole whose absorber mass is formed as a sleeve surrounding the drive shaft in a contact-free manner, said absorber mass being supported on the inner wall of the support tube by absorber springs in end-position seats in the absorber mass in the area of the support tube subject to vibration, the absorber and the absorber springs being pressed into the support tube in a self-supporting manner, each absorber spring comprising a support member held between two bearing rings arranged concentrically in the support tube, the resilience of each support member being such that it absorbs shearing forces in all radial and in longitudinal directions and determines the frequency range of the absorber.

2. A drive assembly as claimed in claim 1, wherein the support member comprises a resilient ring having at least one area which is resiliently deformable under shearing forces in the region of one plane (x-x).

3. A drive assembly as claimed in claim 1 or claim 2, wherein the resilient support members are equi-distant from the centre of gravity of the absorber mass.

4. A drive assembly as claimed in any of claims 1 to 3, wherein the support member is kidneyshaped in cross-section, and has an outer rounded area, an inner trough-shaped area and flattened lateral surfaces on the periphery, one lateral surface being connected to the outer bearing ring and the other lateral surface being connected to the inner bearing ring.

5. A drive assembly as claimed in claim 4, wherein the outer rounded area of the support member extends approximately to an outer plane formed by the two front faces of the bearing rings.

6. A drive assembly as claimed in claim 5, wherein a support base formed by the outer bearing ring is longer than a holding base of the inner bearing ring on the absorber mass and both bearing rings terminate at said outer plane.

7. A drive assembly as claimed in claim 5 or 6, wherein the lateral surface of the resilient support member connected to the inner bearing ring is offset towards said outer plane relative to the lateral surface of the support member connected to the outer bearing ring.

8. A drive assembly as claimed in any of claims 1 to 5, wherein the two bearing rings are of the same length and are arranged overlapping in the support tube.

9. A drive assembly as claimed in any of the preceding claims, wherein the outer peripheral surfaces of the bearing rings each have an elastomeric layer in which are formed longitudinally extending ribs and which are arranged to take up tolerance in their dynamic rigidity to obtain a defined spring characteristic of the resilient support member.

10. A drive assembly as claimed in claim 9, wherein order to obtain a constant distance between the bearing rings they are formed relatively resistant to deformation.

11. A drive assembly as claimed in any of the preceding claims, wherein the absorber mass has an external diameter which corresponds to, or is greater than the external diameter which corresponds to, or is greater than the external diameter of the outer bearing ring.

12. A drive assembly as claimed in claim 11, wherein the outer bearing ring is formed, at least on its inner front face, as a stop which is opposite one front face of the absorber mass.

13. A drive assembly resiliently mounted in a motor vehicle substantially as described with reference to, and as illustrated in, Figs. 1 to 5, or Fig. 6 of the accompanying drawings.