The invention provides also a resilient bush, such as a resilient bush having hydraulic damping, which is suitable for use in a vehicle suspension.

Hydraulically damped resilient bushes are well known for use in vehicle suspensions but their use often is limited by cost considerations, particularly for lower cost, high volume production vehicles.

One object of the present invention is to provide a resilient bush, which may be of the hydraulically damped type, which is relatively low in cost.

In accordance with one aspect of the present invention a resilient bush comprises an inner rigid member, a substantially cylindrical outwardly facing surface defined by said inner rigid member, an outer support member which extends around and is spaced from the inner rigid member to define an annular space therebetween, a substantially cylindrical inwardly facing surface defined by said outer support member, an inner support member which extends around and is in substantially direct contact with the outwardly facing surface defined by the inner rigid member, and an annular bonded element of resilient elastomeric material located between and bonded to confronting surfaces of said inner and said outer support members.

The inner support member may be swageable whereby, on assembly, the elastomeric element becomes loaded in compression, or loaded with additional compression, as the inner support member is force-fitted axially over the cylindrical surface of an inner rigid member of greater diameter than the initial internal diameter of the inner support member.

Additionally or alternatively the outer support member may be axially locatable in an outer rigid member, such as a bush housing defined by a vehicle suspension component, and may be swageable to reduce in diameter and apply (additional) compression to the elastomeric element during axial movement upon assembly.

An auxiliary, second elastoiieric element may be provided in the resilient bush and at least in part miy lie axially spaced from said annular bonded element of elastomeric material. The second element may be bonded to an auxiliary inner support member, which may extend around and be in substantially direct contact with the inner rigid member. It may be bonded to an auxiliary outer support member, or it may be otherwise fluid- tightly secured directly or indirectly to an outer support member. It may be clamped in fluid tight manner against or relative to an axial extension of that outer support member to which the annular bonded element is bonded.

The auxiliary elastomeric element may be axially spaced from at least a part of said annular bonded elastomeric element to define therebetween an annular fluid chamber which may contain hydraulic fluid for providing a damping effect.

One of the inner rigid member and an outer support member or other non- elastomeric member surrounding and spaced from the inner rigid member may be provided with a radially extending flange which extends radially inwardly or outwardly from one of the (substantially) rigid members to the other.

Preferably the flange extends radially outwardly from the inner rigid member at a position between the axial ends of the inner rigid member.

The flange may form at least in part a boundary between two separate zones of the annular fluid chamber. Said zones may be interconnected by a fluid passage formed in and/or defined at least in part by the flange. The fluid passage may comprise an axially extending portion and a circumferentially or likewise (e. g. spirally) extending portion. The circumferentially extending portion may be defined at least in part by material of the flange or by a separate annular cover that defines at least in part a passage in communication with the axially extending portion and in fluid communication with one of said zones of the annular fluid chamber.

An end of the inner support member to which the annular bonded element is bonded, or an end of the auxiliary inner support member, may extend radially outwardly and be disposed in proximity to an axially facing surface of the flange to contact an annular cover and thereby hold said cover in substantially fluid tight contact with the flange face and/or axial flow passage extendir through the flange.

At least the auxiliary, second elastomeric element may comprise an embedded reinforcement, such as a pressed metal member, or a plastics insert.

A suitable material for the support members is pressed steel. A suitable material for the inner rigid member is steel, or aluminium or relatively rigid plastics.

The inner rigid member may be substantially tubular.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:- Figure 1 is a longitudinal cross-section of a resilient hydraulic bush of a first embodiment of the invention, and Figure 2 is a view corresponding to that of Figure 1 of a bush in accordance with another embodiment.

Figure 3 is a view of a modified form of the bush of Figure 2, and Figures 4 and 5 are each views in longitudinal cross-section of other embodiments of resilient hydraulic bushes in accordance with the invention.

The bushes of Figures 1 to 5 are each substantially circular in cross- section as viewed in a plane perpendicular to the axis X-X, the major axis of the bush.

In Figure 1 the bush 10 comprises a tubular inner rigid member 11 of a forged steel and having, between its end regions, an integral radially outwardly extending flange 21.

As viewed in Figure 1, the cylindrical outer surface of the member 11, lying to the right of the flange 21, carries a pressed steel inner sleeve 19 to which an annular bonded element 20 of rubber is bonded. Radially outwardly the element 20 is bonded to part of the axial length of an outer support member 15 of pressed steel and having a stepped outer diameter.

The outer support member 15 extends axially over, and spaced from, the radially outer edge of the flange 21. The bonded element 20 extends at 25 axially between the outer edge of the flange 21 and outer member 15 to provide a fluid tight seal therebetween.

An auxiliary, second annular element 13 is positioned around the inner rigid member 11, at the other side of the flange from the side facing the annular bonded element 20. The element 13 is bonded to an auxiliary inner support member 12, and at a radially outwards region contains an embedded pressed steel reinforcement 14. In the assembly the outer support member 15 is swaged inwards to compress against the reinforcement 14 that rubber material of the element 13 which lies outwards of the reinforcement 14.

The rubber elements 13,20 are each, in part, spaced axially from a respective axially facing surface of the flange 21 so as to define two fluid chamber zones 16a, 16b which contain hydraulic fluid.

The two zones are interconnected by a first fluid passage section 17 that extends axially through the flange and a second fluid passage section 24 which extends circumferentially about the axis X-X and communicates with zone 16b at a position diametrically opposite the passage section 17. The second fluid passage section 24 is formed as a channel in a face of a moulded nylon cover 18. Cover 18 is held substantially fluid tightly against a flange face by an outwardly extending lip 26 provided at one end of the inner sleeve 19. Axial location of the sleeve 19, and also auxiliary support member 12, on the inner rigid member 11 is achieved by a friction fit on assembly (which may be due to a swaging action) and/or by external components such as a nut or a bolt head associated with a location bolt (not shown) that extends through the bore of the member 11 to secure the bush to part of a suspension assembly.

In use of the bush, relative axial movement between the inner rigid member 11 and the support member 15 results in shear deformation of the elastomeric material and a damping effect caused by forced flow of hydraulic fluid through the fluid passage sections 17,24 between the chamber zones 16a, 16b. The damping characteristics may be modified readily by change of shape or size of the passage sections, and optionally annular fluid passage sections may be provided adjacent each face of the flange 21.

In the embodiment of Figure 2 an annular fluid passage section 24'is formed by an annular channel machined or cast in a face of the flange 21.

The channel is covered by plane faced plastics cover 18', similarly held in position by being axially interposed, at its radially inner edge region, between the flange and the lip section 26'of the inner sleeve 19.

Figure 3 shows a modification of Figure 2 in which an alternative sealing arrangement is employed to resist a direct flow of fluid from one chamber 16a to the other 16b via a path extending over the outer radial edge of the flange 21. The modification comprises forming the flange 21 with a pair of bevelled edges 41 close to the radially outer edge of the flange, and providing each elastomeric moulding 13,20 with a flexible lip 42,43 that seals on a respective bevel edge. An intermediate fluid separation chamber 44 is formed around the outer edge of the flange. The lip seals 42,43 act as one-way valves and during relative longitudinal movement of the inner and outer members 11,15 they allow pressurised fluid to enter the chamber 44 from one of the zones 16a, 16b. That pressurised fluid acts on the lip seals to maintain them firmly loaded against the flange and thereby firmly resist any tendency for fluid to flow between the zones 16a, 16b via the outer edge of the flange 21.

Figure 4 shows a construction in which the auxiliary second element 13 of Figure 1, which is bonded to inner member 12, is replaced by an unbonded resilient member in the form of an annular rubber diaphragm 4.

The inner edge of diaphragm 4 is sealingly clamped to inner member 1 by a pressed steel sleeve 2. The axially outer surface 12 of the diaphragm is supported at a radially outer region 13 by an annular steel pressing 3 which is held captive by tabs 14 which are bent inwards from the position of Figure 4. Pressing 3 thereby compresses an outer zone of the diaphragm to provide a fluid tight seal against the outer member 5.

The Figure 4 construction embodies lipseals and an intervening fluid chamber similar to the seals 42,43 and chamber 44 of Figure 3. The portion of the outer member 5 surrounding the inner sleeve 11 is of generally reduced diameter as also featured in Figure 3.

Figure 5 shows a construction having a moulded plastic outer body 12 with a substantially cylindrical outer surface 17 for location in a tubular outer sleeve 14 that fits into a housing member 16. The body 12 has an inner sleeve portion 18 supported relative to the outer part of the body by a series of circumferentially spaced and radially extending webs 19.

The auxiliary elastomeric member 4 of this embodiment is bonded to sleeve 3. It is held captive by annular ring 5 which is secured by bent tags 20 of outer sleeve 14.

The invention contemplates also a reversed configuration in which the inner rigid member lies radially outwards of the aforedescribed outer members with the flange thereof extending radially inwards towards a support member corresponding, for example, to the aforedescribed support member 15.