A McPherson-type suspension unit for motor vehicles

Abstract: A McPherson-type suspension unit for motor vehicles, in which the rod (6) is connected to the motor-vehicle body (S) by means of a resilient connection (8) formed so that the plane in which the rod (6) bears against the body is displaced below the free end (7) of the rod (6). The connection includes an annular block (13) of elastomeric material whose internal surface is joined to an inverted cup-shaped member (9) fixed to the free end (7) of the rod (6) and whose external surface is joined to a hollow body (14) which surrounds the cup-shaped member (9) and the upper end of which carries a member (16,17) for fixing the connection to the body at a level substantially corresponding to that of the free end (7) of the rod (6).

Description: The present invention relates to a McPherson-type suspension unit for motor vehicles, according to the preamble of claim 1. Suspension units of this type had a problem in that the transverse components of the forces transmitted from the wheel in use tended to cause the shock-absorber, and particularly its rod, to be deformed by bending since its connection to the body was conventionally formed in such a way that the point at which the transverse force were applied coincided with the region of its free end. The bending of the rod made it difficult for it to slide and caused it to jam in the tube. Document DE-A-2 820 585 represents an example of such prior art. In order to resolve this problem, it has been proposed to connect the rod to the vehicle body in an arrangement such that the plane in which the rod bears against the body is displaced below the free end of the rod so as to reduce the lever arm of the transverse loads applied thereto and thus to reduce the bending. Document EP-A-0 226 832 discloses a solution according to the preamble of claim 1, in which an annular block of elastomeric material is arranged substantially around the upper end of the tube of a shock-absorber. Other solutions of this type are described, for example, in FR-A-2301399 and DE-A-2 626 392. In all these cases, the connection for fixing the rod to the vehicle body includes a member substantially in the form of an inverted cup fixed at its upper end to the free end of the rod and at its lower end to an annular block of elastomeric material connected to the vehicle body. The block is situated at the level of the vehicle body and the cup-shaped member, together with the portion of the rod surrounded thereby, therefore extends above the region where the shock-absorber is connected to the body. This projection obviously involves greater transverse bulk of the suspension unit and consequent difficulties in adapting the bodywork of the vehicle to enable this installation. The object of the present invention is to avoid the aforesaid disadvantages and to provide a suspension unit of the type defined above which reduces the adverse effect of transverse loads applied to the rod without the need for the shock-absorber to project above the region where the suspension unit is connected to the body of the vehicle. According to the invention, this object is achieved by a McPherson-type suspension unit as claimed. The invention has the advantage that it can be applied to conventional McPherson-type suspension units without the need for structural modifications of the shock-absorber or of the body of the vehicle to which it is fitted. In the static installed condition of the shock-absorber, the block of elastomeric material is arranged around substantially the upper end of the tube. The "static installed condition" obviously means the axial configuration assumed by the shock-absorber under the load of the suspended mass of the vehicle to which the suspension unit is fitted; since the tube moves up to the rod under dynamic conditions, the arrangement according to the invention considerably reduces the length of the rod which is free to bend in operation. The invention will now be described in detail with reference to the appended drawing which is provided purely by way of non-limiting example and shows schematically, in partial axial section, a suspension unit according to the invention. With reference to the drawing, a McPherson-type suspension unit for motor vehicles is generally indicated 1 and supports the structure or body S of the vehicle on a wheel R which, in the example, is a front steering wheel. The suspension unit 1 comprises a conventional shock-absorber 2 with a tube 3 which carries a wheel mounting 4 at its lower end and has a rod 6 projecting from its upper end, indicated 5. The rod 6 is guided for axial sliding by means of a bush, not shown, inserted in the upper end region 5 of the tube 3 in known manner. The free end of the rod 6, indicated 7, is articulated to the body S of the vehicle by means of a resilient connection, generally indicated 8. The connection 8 includes an inverted cup-shaped member 9, the free end 7 of the rod 6 passing through the transverse wall 10 thereof and being fixed thereto by means of a nut 11. The axial dimension of the side wall of the cup-shaped member 10 is such that, when the suspension unit 1 is in the static installed configuration shown in the drawing, its lower end surrounds the upper end 5 of the tube 3. This lower end, indicated 12, is convex and is fixed to the internal surface of an annular block 13 of the elastomeric material whose external surface is fixed in turn to a hollow body, generally indicated 14, which surrounds the cup-shaped element 9. The hollow body 14 has a lower portion 15 which is convex like the lower end 12 of the cup-shaped element 9 and constitutes the element for joining to the elastomeric block 13, and an upper portion 16 whose axis B is inclined to the axis A of the shock-absorber 2. The upper portion 16 has a fixing member 17 of varying thickness associated thereto, and includes an annular bearing plate 18 fixed to the lower portion 15. An axial rolling bearing 19 is interposed between the upper portion 16 of the hollow body 14 and the fixing member 17, and has outer and inner races carried by the fixing member 17 and the plate 18 respectively. The fixing member 17 is connected to the body S by means of screws 20: as can clearly be seen in the drawing, it bears against the body S from below and the arrangement is such that the free end 7 of the rod 6 is situated at a level which corresponds substantially to that of the region of the body S in which the screws 20 are fitted. The vertical bulk of the shock-absorber 2 is thus kept within that of the said region of the body S. An annular element 21 of elastomeric material, against which the upper end of a helical compression spring 22 surrounding the upper region of the shock-absorber 2 bears, is fitted to the lower face of the plate 18. The lower end of the spring 22 reacts against a plate 23 fixed at 24 to the sleeve 3 and arranged parallel to the plate 18. The configuration of the suspension unit 1 shown in broken outline in the drawing corresponds to the telescoped condition (that is, the most contracted condition) of the shock-absorber 2 and the spring 22: in this condition, the plate 24 cooperates with a resilient stroke-limiting buffer 25 which surrounds the upper region of the tube 3 with clearance and is fixed at the top to an annular base wall 26 of the hollow body 14. The maximum dynamic travel of the free end of the rod 6 as a result of the resilient yielding of the block 13 is also shown in broken outline in the drawing: as can clearly be seen, its upward travel from the static condition in which it is level with the body 5 is small and is contained within a cover 27 fitted to the body S.

Claims: A McPherson-type suspension unit for motor vehicles, comprising a telescopic shock-absorber (2) including a tube (3) carrying a wheel mounting (4) at its lower end, a rod (6) slidable through the upper end (5) of the tube (3), a helical compression spring (22) surrounding the shock-absorber (2), a fixing member (17) for fixing the suspension unit to the body (S) of the vehicle, and a resilient connection (8) which includes a member substantially in the form of an inverted cup (9) fixed at its upper end to the free end (7) of the rod (6), an annular block (13) of elastomeric material interconnecting the fixing member (17) and the lower end of the cup-shaped member (9) and being arranged substantially around the upper end (5) of the tube (3) when the shock-absorber (2) is in the static installed condition, characterized in that the resilient connection (8) also includes a hollow body (14,15,16,18) which surrounds the cup-shaped member (9), the lower end (15) of the hollow body being joined to the cup-shaped member (9) by means of the annular block (13) of elastomeric material and the upper end (16,18) of the hollow body being connected to, but separate from, the fixing member (17), the resilient connection (8) being thereby fixed to the body (S) at a level which corresponds substantially to that of the free end (7) of the rod (6). A suspension unit according to Claim 1, characterized in that an axial rolling bearing (19) is interposed between the fixing member (17) and the hollow body (14,15,16,18). A suspension unit according to Claim 2, characterized in that, beneath the bearing (19), the upper portion (16,18) of the hollow body (14) includes an annular bearing plate (18) for the upper end of the helical spring (22). A suspension unit according to Claim 3, characterized in that the axis (B) of the bearing (19) and the bearing plate (18) are inclined to the axis (A) of the shock-absorber (2) at an angle other than 90°. A suspension unit according to Claim 3 or Claim 4, characterized in that an annular element (21) of elastomeric material is interposed between the spring (22) and the bearing plate (18). A suspension unit according to one or more of the preceding claims, characterised in that a resilient, annular stroke-limiting buffer (25) which surrounds the tube (3) of the shock-absorber (2) with clearance is fixed to the hollow body (14,15,16,18) of the resilient connection (8) beneath the annular block of elastomeric material (13) and cooperates with an annular plate (23) which is fixed to the tube (3) and against which the lower end of the helical spring (22) bears.

Inventors: EVANGELISTI RAFFAELE, EVANGELISTI, RAFFAELE
Applicants: FIAT AUTO SPA, FIAT AUTO S.P.A.
Application year: 1990
Main classification: B60G15
IPC codes: B60G15