GB2158549A

GB2158549A - Suspension strut mounting for motor vehicles

Info

Publication number: GB2158549A
Application number: GB08509375A
Authority: GB
Inventors: Urban Agren; Sigvard Zetterstrom
Original assignee: Volvo AB
Current assignee: Volvo AB
Priority date: 1984-04-18
Filing date: 1985-04-12
Publication date: 1985-11-13
Also published as: DE3514067A1; SE441999B; IT8547970A1; JPS6118509A; IT8547970A0; FR2563302A1; SE8402173L; GB8509375D0; FR2563302B1; SE8402173D0; GB2158549B; IT1181641B

Abstract

A suspension strut mounting for motor vehicles comprises an inner sleeve (20), to which a surrounding rubber bushing (15) is vulcanized and in which the upper end of the suspension strut shock absorber piston rod (7) is held. The bushing is securely held in a surrounding sleeve element (13, 14), which is in turn mounted in the vehicle wheel housing. The underside of the bushing provides a seat (32) for a spring suspension. A washer (22) with a rubber bead (24) is held tightly against the upper edge of the inner sleeve, there being a small gap (s) between the bead and an abutment (25), so that minor spring movements and vibrations are absorbed solely by the bushing (15), while major spring movements result in the bead (24) being pressed against the abutment to increase the resistance to movement by the piston rod relative to the mounting. The bead (24) is of harder rubber than the bushing (15). <IMAGE>

Description

SPECIFICATION Suspension strut mounting for motor vehicles The present invention relates to a device for mounting a suspension strut for a steerable vehicle wheel, said strut comprising a tubular portion surrounded by a helical spring, said tubular portion being connected at its lower end to a wheel axle and containing a shock absorber cylinder with a piston and a piston rod extending through the upper end of the tubular portion, said mounting device comprising an inner sleeve which is securely fixed in a surrounding bushing of elastic material and is designed to hold the upper end of the piston rod, and a surrounding sleeve element in which the bushing is securely fixed.

In the most common type of suspension strut mounting of the above-mentioned type, a bearing is pressed into the inner sleeve and serves as a rotatable bearing for the piston rod and as an upper supporting plate for the helical spring. The bushing must in this case be dimensioned to absorb the considerable forces from the spring, which results in a poorer damping characteristic for the shock absorber mounting, since the expansion and compression forces of the shock absorber are small in relation to the spring forces.

It is easier to obtain a desirable damping characteristic for both the shock absorber and the spring if the mountings for the shock absorber and the spring are separated. In such a known design, the shock absorber is rigidly joined to the inner sleeve, and there is relative rotation between the piston and the cylinder when the suspension strut is turned. The upper supporting plate of the spring is in this case supported by a thrust bearing, which bears against the rubber bushing. This bushing can be made in the supporting area for the spring in such a manner that a stiffer mounting is obtained for the spring than for the shock absorber.Starting from this known design, the purpose of the present invention is to achieve a suspension strut mounting, which provides optimum damping characteristics for both the shock absorber and the spring, to thereby achieve still more effective damping of road sounds and vibrations than has been possible up to now.

This is achieved according to the invention in a device of the type described in the introduction by means of a damping element of an elastic material which is harder than the material in the bushing, said damping element, when the suspension strut is mounted in place, being so mounted relative to the inner sleeve that there is a small gap between the damping element and an abutment surface fixed relative to the sleeve element to permit limited axial movement of the inner sleeve before the damping element strikes the abutment surface.

In the embodiment according to the invention, minor movements and vibrations are absorbed solely by the softer bushing, and the damping element comes into use when there is hydraulic damping for larger spring movements. The design makes it possible to easily adapt the damping characteristic to different car models by using different damping elements and varying the gap.

The invention will be described in more detail with reference to an example shown in the accompanying drawing, which shows a longitudinal section through the upper portion of a suspension strut with the associated mounting.

In the Figure, 1 designates a suspension strut mounting for a suspension strut (generally designated 2) of a design which is known per se. The suspension strut 2 comprises a tubular portion 3, at the lower end of which (not shown) a wheel shaft is securely mounted. At the upper end of the tube 3 a seat 4 is welded for the lower end of a helical spring 5. The tube contains a shock absorber cylinder 6, the piston rod 7 of which projects through the tube 3 and is securely held in the mounting 1. The piston rod 7 is surrounded by a rubber buffer 8 and a protective cuff 9 in the form of a rubber bellows. The uppermost turn of the spring 5 is held in a seat 10, which lies in contact with an upper supporting plate 11, which is made with a seat 12 for a thrust bearing.

The suspension strut mounting 1 has a sheet metal member with a cylindrical portion 13 and an annular mounting flange 14 to be screwed onto the vehicle wheel housing. A rubber bushing 15 is fixed in the cylindrical portion 13 via a sheet metal sleeve 16, to which the bushing 15 is vulcanized.

Both the bushing 15 and the sleeve 16 have a radially extending flange portion 17, 18, respectively, which projects beyond the cylindrical portion 13 of the sheet metal element so that the flange 18 of the sleeve 16 is in contact with the underside of the mounting flange 14. The parts are held in place by virtue of the fact that the sleeve 16 has an upper edge portion 19 which is bent out over the upper edge of the cylindrical portion 13. During assembly, the sleeve 16 with the bushing 15 is inserted from below into the cylindrical portion 13, and the sleeve 16 is then "riveted" by bending out the upper edge 19.

The bushing 15 surrounds and is vulcanized to an inner sleeve 20 of metal into which the upper end of the piston rod 5 projects and is fixed by a nut 21, which also fixes a bowl-shaped washer 22 against the upper edge of the sleeve 20. The washer 22 has a conical edge portion 23, to which there is vulcanized an annular bead 24 of harder rubber than the rubber of the bushing. As can be seen in the Figure, there is a small gap "s" between the surface 25 of the bent-out portion 19 facing the bead and the opposing surface 26 of the bead when the components are static. The bead is made with evenly distributed grooves 27 in its surface 26.

Minor oscillations and vibrations within the gap "s" are thus taken up solely by the softer bushing 15, while larger oscillations result in the bead 24 striking the bent-out portion 19, which results in a stiffer damping.

On the underside of the bushing 15 there is a conical washer 28 held tightly between the lower edge of the sleeve 20 and a shoulder 29 on the piston rod. The washer 28 has a conical side surface, which in the static state is spaced from a correspondingly shaped surface 30 on the bushing 15.

After a certain amount of movement this conical lateral surface strikes the surface 30 of the bushing to increase the resistance to upward movement of the piston rod relative to the mounting.

An L-shaped ring 31 is vulcanized into the lower end of the bushing 15 and serves as a reinforcement for a seat 32 for the thrust bearing. As can be seen from the Figure, the damping rubber layer above the thrust bearing is relatively thin, which results in a stiffer damping of the spring mounting than for the piston rod mounting.

In an alternative embodiment to that shown in the drawing, the vertical flange of the L-shaped reinforcing ring 31 can be coated on its outside with a rubber layer which holds the thrust bearing in place during assembly. The sleeve 16 can also be coated with a rubber layer on its outside to serve as insulation between the sleeve 16 and the mounting members 13, 14. Within the scope of the invention, it is also possible to replace the onepiece sleeve 16 with several axially spaced cylinder or ring elements which are vulcanized into the bushing 15 slightly beneath its lateral surface, with the uppermost ring element having a portion which can be bent over the upper edge of the cylinder portion, thus forming an abutment for the bead 24.

In addition to the advantages described in the introduction as regards the possibility of optimizing the damping characteristic, the invention provides a suspension strut mounting which can be made significantly smaller than conventional mountings.

Several components can be vulcanized simultaneously in the tool, which, together with the above described simple "riveting" assembling, reduces costs.

Claims

1. Device for mounting a suspension strut for a steerable vehicle wheel, said strut comprising a tubular portion surrounded by a helical spring, said tubular portion being connected at its lower end to a wheel axle and containing a shock absorber cylinder with a piston and a piston rod extending through the upper end of the tubular portion, said mounting device comprising an inner sleeve which is securely fixed in a surrounding bushing of elastic material and is designed to hold the upper end of the piston rod, and a surrounding sleeve element in which the bushing is securely fixed, characterized by a damping element of an elastic material which is harder than the material in the bushing, said damping element, when the suspension strut is mounted in place, being so mounted relative to the inner sleeve that there is a small gap between the damping element and an abutment surface fixed relative to the sleeve element, to permit limited axial movement of the inner sleeve before the damping element strikes the abutment surface.

2. Device according to Claim 1, characterized in that the damping element comprises a metal washer and an annular bead of elastic material adheringly fixed thereto.

3. Device according to Claim 2, characterized in that the washer is bowl-shaped with a flat bottom and an outwardly inclined lateral edge to which the bead is fixed.

4. Device according to Claim 3, characterized in that the sleeve element has a flange portion extending above the bushing, which is bent outwards to form an abutment surface with the same incline as the lateral edge of the washer.

5. Device according to any one of Claims 2-4, characterized in that the washer, when the suspension strut is mounted, is held tightly between the upper edge of the inner sleeve and a nut screwed onto the piston rod.

6. Device according to Claim 4, characterized in that the bushing and the sleeve element have a substantially cylindrical portion surrounding the inner sleeve and at the lower end of the cylindrical portion a radially extending flange portion, which lies on the underside of a flange of a surrounding fastening element and, together with the outwardly bent portion, fixes the sleeve element relative to the fastening element.

7. Device according to any one of Claims 1-6, characterized in that an abutment is fixed relative to the piston rod on the underside of the bushing and spaced from the downwardly facing surface of the bushing.

8. Device according to Claim 7, characterized in that the abutment is formed of an annular metal washer, which is held tightly between the lower edge of the inner sleeve and a shoulder on the piston rod.

9. Device according to any one of Claims 1-8, characterized in that the bushing is made with a seat for a thrust bearing intended for rotatable mounting of an upper supporting plate of the helical spring.

10. Device for mounting a suspension strut for a steerable vehicle wheel substantially as hereinbefore described with reference to and as shown in the accompanying drawing.