GB2033533A

GB2033533A - Asymmetric rubber bushing

Info

Publication number: GB2033533A
Application number: GB7930487A
Authority: GB
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 1978-09-02
Filing date: 1979-09-03
Publication date: 1980-05-21
Also published as: DE2838391C2; GB2033533B; DE2838391A1; FR2434965B3; FR2434965A1

Abstract

In a resilient bushing of the type in which a rubber member 3 is arranged between and bonded to outer and inner metal sleeves 1, 2, the rubber/metal interfaces are oblique to the axis, so that axial forces F1 applied to the bushing produce radial displacement F* of the metal sleeves. Although the rubber member may provide a circumferentially continuous connection between the metal sleeves, such connection may be restricted to 180 DEG or less where radial displacement is to be confined to a preferred direction. In Figure 4 the bushing has a first region in which the rubber-facing surfaces of the metal sleeves are straight, concentrically arranged cylindrical surfaces and a second region axially adjacent thereto in which said surfaces are frusto- conical, an axial extension of the rubber member extending between the two frustrums only on a circumferential region of less than 180 DEG . <IMAGE>

Description

SPECIFICATION Rubber-metal bearing, particularly for articulating a wheel control arm or an axle assembly to the body of a motor vehicle This invention relates to a rubber-metal bearing of the type having a resilient rubber member arranged between and vulcanized to inner and outer metal sleeves.

Rubber-metal bearings of this type are used in a wide variety of technical fields where a first component is to be pivotally secured to a second component, at the same time avoiding transmission of troublesome load impacts or sounds caused thereby. Rubber-metal bearings are used in a wide variety of embodiments, particularly for articulating wheel control members of motor vehicles. On the one hand, they must be able to accommodate the pivoting movements of the wheel control members, that is to say, the wheel control arms or the like, which occur during deflections of the wheel suspensions, the rubber member being subjected to shear forces and, on the other hand, they must be able to absorb the vibrations caused by micro-acceleration and micro-retardation even on relatively flat roads and even when the speed of travel appears to be constant.

Special constructions of rubber-metal bearings are also sometimes used in order additionally to influence the intrinsic steering behaviour of a motor vehicle both when cornering and when there is a change in load. It is common knowledge that, as a result of elasticities in the wheel suspension, particularly in the rear axle, the lateral forces acting upon the wheels cause an undesirable tendency to oversteer in most vehicles when cornering.In order to counter this tendency to oversteer, it is known to use rubber-metal bearings of differing resilience for articulating, for example, a transverse swinging arm to the body, that is a wheel control arm whose swivel axis extends substantially parallel to the longitudinal axis of the vehicle, and to dimension the rubbermetal bearings such that, when cornering, the wheel carrier is pivotable about a substantially vertical axis which lies behind the axis of rotation of the wheel when viewed in the direction of travel (for example, German Offenlegungsshrift 23 36 787). By way of example, rubber-metal bearings are usedforthis purpose which, as a result of cutaway portions disposed in the resilient material, are particularly resilient in specific directions under the action of radial loads (for example German Utility Model 71 41 159).In the case of wheels articulated to the vehicle body by way of triangulated control arms, that is to say, by way of wheel control arms whose swivel axes extend somewhat obliquely to the longitudinal axis of the vehicle, it is known to articulate the triangulated control arms to the body by means of rubber-metal bearings which are resilient particularly in an axial direction, so that the triangulated control arm is pivoted in the toe-in direction under the action of the centrifugal or lateral forces occurring when cornering.

The object of the invention is to provide a rubber-metal bearing of the type described which reduces or eliminates the tendency to over-steer occurring during cornering, even in the case of those wheel control members in which the swivel axis extends transversely of the longitudinal axis of the vehicle, that is to say, at an angle of at least approximately 90 . The wheel confrol members under consideration are, in particular, so-called compound or coupling rear guide axles or even rear longitudinal control arms or trailing links having two bearings on the body.

According to the present invention, a rubber-metal bearing of the type described is characterised in that the surfaces of the inner and outer metal sleeves which face the rubber member extend at least partially obliquely to the axis of the bearing, such that the inner and the outer metal sleeves are displaced radially in a predetermined direction relative to one another in a controlled manner upon the introduction of axial forces into the bearing.

Preferably, the metal sleeves are so constructed that, in conjunction with the rubber member, they form a kind of sliding ramp or platform, so that, upon the introduction of axial forces such as occur when cornering, controlled radial forces occur by which the inner metal sleeve and the outer metal sleeve are displaced radially in a predetermined direction relative to one another in a controlled manner, which leads to the desired pivoting of the wheel control member when the two points at which the wheel control members are articulated to the body are correspondingly matched.

Although the rubber member may interconnect the two metal sleeves over a circumferential region of 180 , in one preferred construction, the bearing has a first region in which the rubber-facing surfaces of the metal sleeves are straight, concentrically arranged cylindrical surfaces and a second region axially adjacent thereto in which said surfaces are frusto-conical, an axial extension of the rubber member extending, relative to the axis of the bearing, between the two frustrums only on a circumferential region of less than 180 .

Rubber-metal bearings have already been proposed (German Patent No. 2748 193.2) in which, upon the introduction of axial forces, controlled radial forces also occur by which the inner metal sleeve and the outer metal sleeve are displaced radially in a predetermined direction relative to one another in a controlled manner, although, in these bearings, the rubber member itself is of special design. In these bearings, if the dimensions of the bearings are not to be too large, the possible radial displacement is frequently not as great as would be desirable for technical reasons. Additional difficulties are thereby caused by the stresses in the rubber which, in places, are very high.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an axial end view of one rubber-metal bearing embodying the invention; Figure la is an axial section thereof; Figure 2 is an axial end view of another embodiment; Figure 2a is an axial section corresponding to Figure 2; Figures 3 and 4 are axial sections of further embodiments of the invention, and Figure 5 is an elevation, partly in section, of a vehicle reer wheel suspension arrangement including the bearing shown in Figure 4.

In the rubber-metal bearing shown in Figures 1 and la, the outer metal sleeve of the bearing is designated 1, and the inner metal sleeve is designated 2. The resilient rubber member which interconnects the two metal sleeves, and which is vulcanised to them is designated 3. The sleeve surfaces which face the rubber member 3 slope relative to the axis A of the rubber-metal bearing.

They constitute surfaces of sloping circular cylinders with respect to the bearing axis. A central axial bore 23 of the inner metal sleeve 2 can be used to connect the sleeve 2, for example, to a bearing pin (not shown) disposed on a body of a motor vehicle, whilst the corresponding surface of the outer metal sleeve 1 is concentric to the bore 23 and can be pressed into the bearing eye of a wheel control arm or of a compound axle. It will be seen that, as a result of the surfaces sloping relative to the bearing axis, the two metal sleeves 1 and 2 are displaced radially relative to one another upon the introduction of axial forces into the bearing.It has been assumed, in Figure 1, that an axial force F1 acts upon the outer metal sleeve 1 which is connected to, for example, a wheel control arm, thus resulting in a corresponding reaction force F'1 which acts upon the inner metal sleeve 2, the latter, as previously mentioned, being connected for example to a bearing pin. Taking into account the direction of slope chosen in the illustrated embodiment, of the surfaces abutting against the rubber member 3, the axial force F1 introduced results in a radial force F* which displaces the outer metal sleeve to the left in the plane of the drawing.

The magnitude of the radial force F and thus the magnitude of the relative radial displacement of the metal sleeves depends upon the selected slope of the metal sleeves, the thickness of the rubber and the hardness of the rubber. It will be seen that a radial force acting in the opposite direction is produced when the axial force F1 is introduced into the outer metal sleeve 1 from the other end face.

Thus, the rubber-metal bearing shown in Figure 1 is equally effective for both directions of force.

Whilst the rubber member 3 of the rubber-metal bearing shown in Figure 1 interconnects the two metal sleeves along their entire circumferences, the two corresponding sleeves 1 and 2 and the rubber member 3 in the bearing shown in Figure 2 are constructed such that the rubber member interconnects the two metal sleeves only along a circumferential region of less than, or approximately, 180 , the metal sleeves 1 and 2 having surfaces comprising sloping circular cylinders only in this region. The two metal sleeves are not interconnected in the remaining circumferential region. The result of this is that, in contrast to Figure 1, the desired radial displacement occurs only in one direction.If it is desired or necessary that radial displacement should also occur in the other direction with a corresponding direction of force, two individual bearings can be axially and directly connected to one another to form a complete bearing, such that the outer surface regions sloping relative to the bearing axis A are offset through 1800 relative to one another, namely both with respect to the bearing axis A and with respect to the butt joint B between the two component bearings. A complete bearing composed of component bearings of this kind is shown in Figure 2a. The individual parts of the upper component bearing are provided with the reference numerals already used in Figure 1, and those of the bottom second component bearing are provided with corresponding reference numerals supplemented by an apostrophe.The mode of operation of this complete bearing is substantially the same as that of the rubber-metal bearing shown in Figure 1,the ratio between the axial force introduced and the radial displacement force achieved again being dependent upon the data chosen for the individual parts. Since, in the complete bearing illustrated in Figure 2a, the surfaces connected to the rubber member slope in the opposite direction to the slope shown in Figure 1, a radial force F* acting in the opposite direction to that of Figure 1 ensues with the axial force F1 introduced in the same direction.

In the embodiments of Figures 1 and 2, the sloping sleeve surfaces connected to the rubber member 3 are disposed within the actual bearing body. In the embodiments of Figures 3 and 4, the sloping surfaces effecting the radial displacement are arranged axially adjacent to the actual bearing body, the bearing shown in Figure 4 being composed of two component bearings. Each of these rubber-metal bearings has a first region in which the two metal sleeves 1 and 2 are concentrically disposed, straight cylinders 11 and 21 respectively. There is provided axially adjacent thereto a second bearing region in which the two metal sleeves take the form of respective frustrums 12 and 22 in respect of their rubber-facing surfaces.The rubber member 3 has an axial extension 31 which, relative to the bearing axis A, extends between the two frustrums only in a circumferential region of less than 1800. In the embodiment shown in Figure 3, the outer metal sleeve 1 is in the form of a circularly symmetrical body having a cylindrical first region and a frustoconically widening second region axially adjacent thereto, whilst the inner metal sleeve 2 constitutes only a partially circularly symmetrical body which comprises a cylindrical first region and, axially adjacent thereto, a second region which widens in a frusto-conical manner only in a circumferential region of less than 180 . It will be appreciated that it is also possible for the two metal sleeves to be in the form of circularly symmetrical bodies and only to limit the extension 31, extending into the frustoconical region, of the rubber member 3 to a circumferential region of less than 180 . Alternatively, as is shown in Figure 4, the two metal sleeves 1 and 2 can be in the form of only partially circularly symmetrical bodies each having a cylindrical first region 11 and 21 respectively and a second region, axially adjacent thereto, which widens frusto-conically only in a circumferential region of less than 180 . In the final analysis, the choice of these variants depends, in the individual case, upon the conditions with respect to manufacturing technology. The same dimensions being assumed, these bearings are identical with respect to their mode of operation. These rubbermetal bearings are, as individual bearings, also effective in only one direction in each case.If a corresponding radial displacement is also to be achieved for the axial forces introduced in the opposite direction, two individual bearings again have to be axially and directly joined together to form a complete bearing, as has already been shown and explained in Figure 2a and as is illustrated in Figure 4.

The maximum radial displacement in the case of the bearings shown in Figures 3 and 4 is obtained when the frusto-conical surface regions 12 and 22 of the two metal sleeves 1 and 2 slope to at least approximately equal extents relative to the bearing axis 1. However, with respect to stress, the most favourable conditions for the rubber element 3 exist when the frusto-conical surface region 12 of the outer metal sleeve 1 slopes to a greater extent, relative to the bearing axis A, than that of the inner metal sleeve 2, namely such that the imaginary apieces of these two frusto-conical regions come to lie at least approximately on the same point of the bearing axis A. Thus, the most favourable dimension for the slope of the frusto-conical surfaces depends upon the individual case of use.

Owing to their greatly sloping slide surfaces outside the actual bearing body, the embodiments shown in Figures 3 and 4 permit particularly satisfactory radial displacement and, moreover, they render it possible to accommodate the large thickness of the rubber layer necessary for satisfactory noise insulation.

In orderto improve the sliding relationship or displacement ratio between the axial force and the radial force, it is possible to provide the rubber member 3 with preferably reniform recesses 32 in the cylindrical first region of the bearing, as is shown in Figures 3 and 4.

It will be seen from the illustrated embodiments that the direction of the radial displacement depends upon the position in which the rubber-metal bearing is fitted and upon the direction of the axial force introduced. When the bearing provided by the invention is used for articulating a wheel guide arm or an axle assembly (for example, a trailing arm beam axle assembly, or a coupling guide axle) to the body of a motor vehicle, the respective installation conditions then have to be taken into account to obtain the desired intrinsic steering behaviour. A part, namely the left hand part, of a so-called coupling guide axle is illustrated diagrammatically in Figure 5 and substantially comprises two longitudinal swinging arms which carry the rear wheels, and a bend-resistant, torsionally soft transverse member which interconnects the two longitudinal swinging arms.Only the left hand longitudinal swinging arm 6 with the left hand rear wheel 5 mounted thereon, and the transverse member 7, are illustrated. This coupling guide axle assembly is articulated to the vehicle body 4 (only diagrammatically indicated) by means of rubber-metal bearings of the type described previously. A bearing of the type illustrated in Figure 3 is indicated, the reniform recesses, usually provided, not being shown in order to simplify the illustration. The outer metal sleeve (not designated) is non-torsionally secured in a bearing eye of the longitudinal swinging arm 6, and the inner metal sleeve (also not designated) is non-torsionally connected to a bearing pin 8 secured to the vehicle :body 4. The right hand longitudinal swinging arm (not illustrated) is articulated in a corresponding manner, the rubber-metal bearing being fitted in mirror image fashion.The bearing axis A extends transversely of the longitudinal axis of the vehicle.

The direction of travel of the vehicle is indicated by an arrow (not provided with a reference numeral). In order to explain the mode of operation, it is assumed in Figure 5 that a lateral force F is acting upon the wheel 5, such as occurs when, for example, travelling on a right hand curve. Correspondingly, a force F1, acts upon the outer metal sleeve of the rubbermetal bearing, and the associated reaction force F1' acts upon the inner metal sleeve. In conformity with the explanations already given in conjunction with Figures 1 to 4, with this combination of forces, and with the direction in which the rubber-metal bearing is fitted in this instance, a displacement force F occurs which acts upon the outer metal sleeve and which is effective in the direction of travel.As will be seen, the entire axle assembly is thereby slightly pivoted, namely in the direction of toe-in, that is to say, in the illustrated embodiment, it is pivoted slightly in a clockwise direction. When travelling on a left hand curve, the corresponding conditions would prevail at the right hand longitudinal swinging arm (not further illustrated). When, in contrast to the embodiment illustrated in Figure 5, a bearing corresponding to Figure 4 or Figure 2, and composed of two component bearing, is used, not only is the longitudinal swinging arm at the wheel on the outside of the curve displaced in the direction of travel (as is shown in Figure 5), but the longitudinal swinging arm at the wheel on the inside of the curve is at the same time displaced in the opposite direction to the direction of travel.Therefore, has already been explained, the rubber-metal bearings ofthe kind illustrated in Figure 5 and Figure 3 can cause substantial radial displacement only in one direction, namely when the portion of the rubber member located between the sloping parts of the metal sleeves is subjected to pressure. No perceptible displacement takes place when this part is subjected to tensile stress. It will be seen that, in the case of load assumed in Figure 5, tensile stress does not occur in this part of the rubber member of the rubber-metal bearing (not shown) of the right hand swinging arm, so that the outer metal sleeve cannot be displaced. Corresponding conditions occur in the illustrated bearing when the vehicle is travelling on a left-hand curve, and the forces F, F1 and F1, would in each case act in the opposite direction.

In contrast to the use described with reference to Figure 5, it will be appreciated that the described rubber-metal bearings can also be used to obtain other defined deflections of wheel control members.

Thus, for example, by using a rubber-metal bearing of this kind, it is conceivable to construct the transverse swinging arm of a front axle such that, upon changes of velocity, the transverse swinging arm is displaced substantially only in the longitudinal direction of the vehicle as a result of the forces then acting upon the wheel, and only smaller undesirable changes in toe-in thereby occur.

Claims

1. A rubber-metal bearing having a resilient rubber member arranged between, and vulcanised to, an outer metal sleeve and an inner metal sleeve, characterised in that the surfaces of the inner and outer metal sleeves which face the rubber member extend at least partially obliquely to the axis of the bearing, such that the inner and the outer metal sleeves are displaced radially in a predetermined direction relative to one another in a controlled manner upon the introduction of axial forces into the bearing.

2. A rubber-metal bearing as claimed in claim 1, in which the metal sleeve surfaces comprise cylindrical surfaces or segments thereof which are oblique with respect to the axis of the bearing.

3. A rubber-metal bearing as claimed in claim 2, in which the rubber member interconnects the two metal sleeves only along a circumferential region of approximately 1800, the metal sleeves in this region having outer surfaces constituting sloping circular cylinders.

4. A rubber-metal bearing as claimed in claim 1, characterised by a first region of the bearing in which the rubber-facing surfaces of the metal sleeves are straight, concentrically arranged cylindrical surfaces and a second region axially adjacent thereto in which said surfaces are frusto-conical an axial extension of the rubber member extending relative to the axis of the bearing, between the two frustrums only on a circumferential region of less than 1800.

5. A rubber-metal bearing as claimed in claim 4, in which the two metal sleeves are in the form of circularly symmetrical members having a cylindrical first region and axially adjacent thereto a second region which widens in a frusto-conical manner.

6. A rubber-metal bearing as claimed in claim 4, in which the outer metal sleeve is in the form of a circularly symmetrical member having a cylindrical first region and axially adjacent thereto a second region which widens in a frusto-conical manner, and that the inner metal sleeve is in the form of a partially circularly symmetrical member having a cylindrical first region and axially adjacent thereto a second region which widens in a frusto-conical manner only in a circumferential region of less than 180 .

7. A rubber-metal bearing as claimed in claim 4, in which the two metal sleeves are in the form of partially circularly symmetrical members having a cylindrical first region and axially adjacent thereto a second region which widens in a frusto-conical manner only in a circumferential region of less than 1800.

8. A rubber-metal bearing as claimed in any one ot clalms 4 to 7, in which the trusto-conical surtace regions of the two metal sleeves slope at least approximately equally relative to the axis of the bearing.

9. A rubber-metal bearing as claimed in any one of claims 4 to 7, in which the frusto-conical surface region of the outer metal sleeve slopes to a greater extent relative to the axis of the bearing than that of the inner metal sleeve, such that their imaginary apieces lie at least approximately on the same point of the axis of the bearing.

10. A rubber-metal bearing as claimed in any one of claims 4 to 9, in which the cylindrical first region of the rubber member is provided with reniform recesses.

11. A rubber-metal bearing as claimed in claim 1, in which two individual bearings as claimed in one of claims 3 to 10 are axially and directly joined together to form a complete bearing, such that their surface regions sloping relative to the bearing axis are staggered through 1800 relative to one another with respect to said axis and with respect to the butt joint between said two individual bearings.

12. A vehicle wheel suspension assembly comprising a rubber-metal bearing as claimed in any one of claims 1 to 11, in which a wheel control arm or an axle assembly is arranged for articulation to the body of a motor vehicle by said bearing, with the bearing axis aligned transversely of the longitudinal axis of the vehicle and the bearing itself fitted such that the ensuing radial displacement of the metal sleeves takes place at least approximately horizontally.

13. A wheel suspension assembly as claimed in claim 12, in which the direction of radial displacement of the individual rubber-metal bearing is in each case matched to that of the other rubber metal bearings of the wheel control arm or of the axle assembly, such that the wheel control arm or the axle assembly is pivoted in the toe-in direction when the vehicle is cornering.

14. Rubber-metal bearings constructed, arranged and adapted to operate substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 4 inclusive of the accompanying drawings.

15. A vehicle wheel assembly constructed, arranged and adapted to operate substantially as hereinbefore described with reference to and as illustrated in Figure 5 of the accompanying drawings.