The invention relates also to a vehicle subframe and suspension assembly adapted to be secured substantially directly to the vehicle body and wherein the suspension assembly comprises a resilient bush of the invention, and to a vehicle comprising said assembly secured substantially directly to the vehicle body.

Many different constructions of hydraulic type resilient bush are known for use in a vehicle suspension. One example, as described in EP-0 456 959A employs a substantially rigid moulded plastics element to cooperate with an outer housing and define a flow passage through which hydraulic fluid reciprocates between two chambers when the bush is subjected to repeated reversal of axial loading.

A problem arising in the use of a hydraulic bush of the aforedescribed type is that the reciprocating flow of fluid generates hydraulic noise.

Special measures are needed to prevent that noise being apparent to vehicle occupants.

The transmission of hydraulic noise to vehicle occupants can be suppressed by provision of a resilient mounting between a vehicle subframe and suspension assembly, but that is not possible if the subframe needs to be secured directly to the vehicle body for the purpose of achieving a required level of rigidity.

The present invention seeks to provide an improved resilient bush, for example of the hydraulic type, and which enables the aforedescribed difficulty to be mitigated or overcome.

According to one aspect of the present invention a resilient bush comprises an inner rigid member, an outer rigid member which extends around and is spaced from the inner rigid member to define an annular space therebetween, resilient elastomeric material which extends between said inner and outer rigid members at positions axially spaced by said annular space and with said elastomeric material being in fluid tight contact relative to said rigid members whereby said annular space may contain hydraulic fluid, a pair of axially spaced rigid support members which each extend radially in said annular space from one of the inner and outer rigid members towards but spaced from the other of said inner and outer rigid members, and a deformable boundary member which is supported by said axially spaced rigid support members and extends radially into contact with said other of said inner and outer rigid members.

The deformable boundary member may extend radially into the axial space between the pair of rigid support members thereby to be secured axially relative to said support members.

The deformable boundary member may be in fluid tight contact relative to said other of said inner and outer rigid members and/or with said pair of axially spaced rigid support members.

One or more of the pair of axially spaced support members and the boundary member may be adapted to define or cooperate with another member to define a fluid flow passage which communicates between two fluid chambers that lie axially spaced in said annular space at respective sides of the pair of support members. Said another member may be defined by elastomeric material which may be bonded to the support members, and may be integral with a thin layer of elastomeric material which extends over the support members from the elastomeric material which extends between the inner and outer rigid members at said positions which are axially spaced by the fluid chambers. Said another member may define an open sided Channel the open side of which is covered by the boundary member.

The fluid flow passage typically may extend circumferentially or helically through at least 180°, more preferably 330°.

The axial spacing of confronting surfaces of the rigid support members preferably is less than 70%, more preferably less than 50%, of the radial extent of said members as measured from said one of said inner and outer rigid members. In a preferred embodiment said axial spacing is approximately one third of said radial dimension.

Each of the axially spaced support members may be circumferentially continuous or one or each may comprise a series of circumferentially spaced formations. The support members may be shaped from a single piece of metal stamped to form two axially spaced series of petal-like formations.

A space between a successive pair of formations in each series may provide a fluid passage interconnection between a fluid chamber and a fluid flow passage provided between the support members for fluid flow between two fluid chambers. Said single piece of metal additionally may comprise an integral substantially cylindrical portion which comprises at least a part of the inner rigid member. That cylindrical portion may have an inwardly directed end flange adapted to locate against an end or shoulder of a rigid component over which the cylindrical portion may be fitted.

Alternatively the axially spaced support members may be comprised by two rigid members. Axially spaced radially extending portions of those members may be secured together by a spacer which may, for example, be welded to one or each of the rigid support members and which may be integral with one of the rigid support members.

The fluid chambers may contain hydraulic fluid and the boundary member may serve to provide a substantially fluid-tight seal between the pair of support members and said other of the inner and outer rigid members whereby relative axial movement of the inner and outer rigid members causes hydraulic fluid to flow through a fluid passage which interconnects the fluid chambers.

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 bush of a first embodiment of the invention ; Figure 2 is a perspective view of a part of the bush of Figure 1 ; Figure 3 is a longitudinal cross-section of a resilient bush of a second embodiment of the invention, and Figure 4 is a perspective view of parts of the bush of Figure 3 which correspond with the part shown in Figure 2.

The bushes of Figures 1 and 3 are substantially circular in cross-section as viewed in a plane perpendicular to the axis X-X, the major, longitudinal axis of the bush.

In Figure 1 a resilient hydraulic type bush 9 is fitted to a tubular steel component 10 of a vehicle suspension.

The bush 9 comprises an inner rigid member 11 of pressed steel and described in more detail below. Member 11 is surrounded by an outer rigid member 20 also of pressed steel. A one-piece rubber moulding 8 occupies part of an annular space between the rigid members. The moulding 8 is bonded to the inner rigid member 11 and comprises two annular portions 13, 15 axially spaced apart in part to define therebetween a pair of fluid chambers 17, 18. Portion 13 is bonded to a metal end pressing 12 around which the outer rigid member 20 extends with a thin layer of rubber lying between pressing 12 and member 20 to provide a fluid tight seal. Portion 15 is bonded to a metal pressing 14 around an end region of which the outer rigid member 20 also extends, with a thin layer of the rubber therebetween to provide a fluid-tight seal.

The pressing 11 comprises a pair of axially spaced rigid support members lla, llb, each of which is circumferentially discontinuous and comprised by a series of circumferentially spaced petal portions 21, 22 as more clearly seen in Figure 2. Portions 21, 22 are integral with a cylindrical body section 23 and an inwardly directed end flange 24. The bore of body section 23 fits closely over the tubular suspension component 10, with the flange 24 abutting the end of tubular component 10.

The axial space between the members lla, llb contains a section 26 of the rubber moulded to define an open sided fluid flow channel 16 which extends generally circumferentially through 340°. Ends of the channel 16 communicate with the chambers 17, 18 via openings between successive pairs of petals.

The open, outer side of channel 16 is covered and sealed by the radially inner surface of a boundary member 19 that acts as a fluid seal to extend between the support members lla, llb and the outer rigid member 20. The radially outer edge of boundary member 19 is held captive in an annular recess 25 in the outer rigid member. Seal 19 cooperates with the support members lla, llb to provide a barrier between the chambers 17, 18. In consequence, in the event of relative longitudinal movement of the inner and outer rigid members 11, 20 hydraulic fluid is forced to flow between the chambers 17, 18 via the flow channel 16.

In the construction of Figures 1 and 2 the fluid flow passage 16 is isolated from direct contact with the inner and outer rigid members. Selection of a suitably non-rigid material for the boundary seal 19 allows any transmission of hydraulic noise to the outer rigid member 20 to be contained within acceptable levels.

Figures 3 and 4 show a modification of the embodiment of Figures 1 and 2.

In this construction 29 the inner rigid member of pressed steel comprises a main section 30 having a tubular body portion 31, an inwardly directed end location flange 33, and an outwardly extending flange 32 which defines one of the pair of support members. An auxiliary section 35 provides another outwardly extending flange 36 to serve as the outer support member of the pair and an integral tubular spacer section 37. Section 37 has a length equal to the desired axial spacing of the support members. The free end of the section 37 may be spot welded to the radially inner region of the flange 32 for axial location. Alternatively the tubular suspension component 10 may be stepped to provide a shoulder against which the flanged end of the auxiliary section 35 may be axially located.