GB2296074A

GB2296074A - Suspension strut compensation valve assembly

Info

Publication number: GB2296074A
Application number: GB9425179A
Authority: GB
Inventors: Erwin Jentsch
Original assignee: ACG Deutschland GmbH
Current assignee: ACG Deutschland GmbH
Priority date: 1994-12-14
Filing date: 1994-12-14
Publication date: 1996-06-19
Anticipated expiration: 2014-12-14
Also published as: GB2296074B; GB9425179D0

Abstract

A suspension strut of the twin tube damper type includes an outer tube (12); an inner tube (14); and a compensation valve (20) assembly, wherein the compensation valve assembly comprises first valve means (50 - 56) allowing fluid flow from a compression chamber (38) to a compensation chamber (40) when fluid pressure in the compression chamber exceeds that in the compensation chamber by a predetermined amount, second valve means (64, 66) allowing fluid flow from the compensation chamber to the compression chamber when fluid pressure in the compensation chamber exceeds that in the compression chamber by a predetermined amount, and a two part housing (74) retaining the first and second valve means, and comprising a first part (72) with a cylindrical outer wall (76) having a free edge (100), and a second part (82) with an annular outer wall (92, 94) having a circumferential groove (98), portions (102) of the free edge being staked over into the groove to secure the two parts of the housing together, and portions of the cylindrical outer wall being trapped between the annular outer wall and the inner tube. Reduces the risk of two parts of the housing separating when the suspension strut is in use. <IMAGE>

Description

SUSPENSION STRUT The present invention relates to a suspension strut or shock absorber for the suspension system of a motor vehicle.

Known suspension struts comprise an inner tube; an outer tube; a compensation chamber formed between the inner and outer tubes; a piston assembly sealably slidably mounted in the inner tube, the piston assembly separating a compression chamber from a rebound chamber within the inner tube; a rod guide positioned at one end of the inner and outer tubes; a piston rod connected to the piston assembly and extending through the rebound chamber and the rod guide; and a compensation valve assembly positioned at the other end of the inner tube. These known suspension struts are commonly referred to as twin-tube dampers.

In these known arrangements, the compensation valve assembly typically comprises a number of apertures normally closed by one of two valve elements (such as resilient discs). One valve element allows flow of fluid through some of the apertures from the compensation chamber to the compression chamber, and the other valve element allows flow of fluid through the remaining apertures during use of the suspension strut. Similarly the piston assembly allows fluid flow between the rebound chamber and the compression chamber during use of the suspension strut. One known construction of the compensation valve assembly includes a two part housing in which the two parts are joined together at surfaces which extend in a plane substantially normal to the longitudinal axis of the suspension strut.

It is an aim of the present invention to provide an improvement to the above arrangement.

To this end, a suspension strut in accordance with the present invention comprises an outer tube; an inner tube positioned inside the outer tube; a compensation valve assembly closing one end of the inner tube; one end of the outer tube being closed; a rod guide closing the other ends of the inner tube and the outer tube; a piston assembly slidably sealably positioned inside the inner tube and dividing the inner tube into a rebound chamber and a compression chamber; a piston rod connected to the piston assembly and extending through the rebound chamber and the rod guide; and a compensation chamber formed between the inner tube and the outer tube; wherein the compensation valve assembly comprises a first valve means allowing fluid flow from the compression chamber to the compensation chamber when fluid pressure in the compression chamber exceeds that in the compensation chamber by a predetermined amount, a second valve means allowing fluid flow from the compensation chamber to the compression chamber when fluid pressure in the compensation chamber exceeds that in the compression chamber by a predetermined amount, and a two part housing retaining the first and second valve means, the two part housing having a first part with a cylindrical outer wall having a free edge, and a second part with an annular outer wall having a circumferential groove, portions of the free edge being staked over into the groove to secure the two parts of the housing together, and portions of the cylindrical outer wall being trapped between the annular outer wall and the inner tube.

The present invention securely holds the two parts of the housing of the compensation valve assembly together during use of the suspension strut.

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional view of a suspension strut in accordance with the present invention; and Figure 2 is an enlarged cross-sectional view of the compensation valve assembly of the suspension strut of Figure 1.

Referring to Figure 1 of the drawings, the suspension strut 10 shown in Figure 1 is of the twin tube damper type, and comprises an outer tube 12, an inner tube 14 substantially coaxial with the outer tube on an axis L, a piston assembly 16, a piston rod 18 having a longitudinal axis on axis L, a compensation valve assembly 20, and a rod guide 22.

The piston assembly 16 and the rod guide 22 may be any suitable conventional design well known to those skilled in the art, and will not be described in detail. The compensation valve assembly 20 is described in greater detail below. The inner tube 14 is substantially closed at one end 24 by the compensation valve assembly 20, and is substantially closed at the other end 26 by the rod guide 22. The outer tube 12 is closed at one end 28 by an integral formation of the outer tube walls or any other suitable means, and is substantially closed at the other end 30 by the rod guide 22. The piston rod 18 extends through, and makes a sealing sliding fit with the rod guide 22. The piston assembly 16 makes a sealing sliding fit with the inner surface 32 of the inner tube 14. The piston rod 18 is secured to the piston assembly 16 by a nut 34 or any other suitable means.The piston assembly 16 divides the inner area of the inner tube 14 into a rebound chamber 36 and a compression chamber 38. The area between the inner tube 14 and the outer tube 12 defines a compensation chamber 40. The rebound and compression chambers 36 and 38 are substantially filled with fluid to damp reciprocating movement of the piston assembly 16 and piston rod 18 along axis L relative to the outer and inner tubes 12 and 14. Valves (not shown) in the piston assembly 16 allow controlled flow of fluid between the rebound chamber 36 and the compression chamber 38 as is well known to those skilled in the art. The compensating chamber 40 is partly filled with fluid and acts as a reservoir for the fluid in the rebound and compression chambers 36 and 38. The suspension strut 10 is mounted in a motor vehicle (not shown) in any suitable manner.

The compensation valve assembly 20, as shown in Figure 2, comprises an inner member 42 with a substantially central through aperture 44 and one of more through apertures 46 offset from the central aperture. On one side 48 of the inner member 42, the central aperture 44 is closed by a disc 50 having an annular ridge 52 which is biased against the side 48 by a coil spring 54. A substantially cup-shaped spring retainer 56 having at least one opening 58 therethrough holds the coil spring 54 in position.

The or each aperture 46 opens into an annular channel 60 formed in the other side 62 of the inner member 42.

An annular disc 64 covers the channel 60 and is biased into contact with the other side 62 of the inner member 42 by an annular plate spring 66. The disc 64 and the plate spring 66 have openings 68, 70 respectively therethrough.

At a predetermined fluid pressure differential where the pressure in the compression chamber 38 exceeds the pressure in the compensation chamber 40, the disc 50 will move away from the one side 48 of the inner member 42 against the bias of the spring 54. This allows fluid to flow from the compression chamber 38 to the compensation chamber 40 by way of openings 70, 68, central aperture 44, and opening 58. This predetermined fluid pressure differential can be changed by changing the spring 54 to one having a different spring rate and/or by changing the disc 50 to one having a different diameter for the annular ridge 52.

At a predetermined fluid pressure differential where the pressure in the compensation chamber 40 exceeds the pressure in the compression chamber 38, the disc 64 will move away from the channel 60 in the other side 62 of the inner member 42 against the bias of the spring 66. This allows fluid to flow from the compensation chamber 40 to the compression chamber 38 by way of opening 58, aperture or apertures 46, and openings 80, 68, and 70.

A first part 72 of a two part housing 74 holds the plate spring 66 in position. The first part 72 of the housing 74 is substantially cup-shaped and comprises a substantially cylindrical outer wall 76 and a base 78 with an opening 80 therethrough. The housing 74 includes a second part 82 which is substantially annular. The outer wall 76 of the first part 72 is bent to define an annular shoulder 84 which is directed towards the second part 82, and the second part is formed with a corresponding annular shoulder 86 directed towards the first part. The shoulders 84 and 86 are positioned inwardly of the first and second parts 72, 82 respectively. On assembly of the compensation valve assembly 20, the peripheral edge 88 of the inner member 42 and the peripheral edge 90 of the spring retainer 56 are trapped between the shoulders 84, 86.

The second part 82 of the housing 74 has an outer wall with a first diameter part 92 and a second diameter part 94 which define a second annular shoulder 96 therebetween. The first diameter part 92 has a smaller diameter than the second diameter part 94. The second shoulder 96 is directed towards the first part 72 of the housing 74. A circumferential groove 98 is formed in the first diameter part 92 adjacent the second shoulder 96. The outer wall 76 of the first part 72 has a free edge 100. Adjacent the free edge 100 of the outer wall 76, the inner diameter of the outer wall is substantially the same as the diameter of the first diameter part 92 of the second part 82.On assembly of the first and second parts 72, 82 of the housing 74, the free edge 100 of the outer wall 76 of the first part 72 is positioned adjacent the second shoulder 96, and a number of portions 102 of the free edge are staked over into the groove 98 to secure the first and second parts 72, 82 together.

Adjacent the free edge 100 of the outer wall 76, the outer diameter of the outer wall is substantially the same as the inner diameter of the inner tube 14. The diameter of the second diameter part 94 of the second part 82 of the housing 74 is substantially the same as, but preferably no less than, the outer diameter of the inner tube 14. On attachment of the compensation valve assembly 20 to the one end 24 of the inner tube 14, the one end of the inner tube engages the second shoulder 96 of the second part 82 and traps a portion of the outer wall 76 of the first part 72 adjacent the free edge 100 between the inner tube and the first diameter part 92 of the second part 82. With this arrangement, the staked over portions 102 remain trapped in the groove 98 to substantially prevent the first and second parts 72, 82 of the housing 74 from separating during use of the suspension strut 10.

On assembly of the suspension strut 10, the second diameter part 94 of the second part 82 of the housing 74 is trapped between the one end 24 of the inner tube 14 and shoulders 104 formed at the one end 28 of the outer tube 12.

Claims

Claims:

1. A suspension strut comprising an outer tube; an inner tube positioned inside the outer tube; a compensation valve assembly closing one end of the inner tube; one end of the outer tube being closed; a rod guide closing the other ends of the inner tube and the outer tube; a piston assembly slidably sealably positioned inside the inner tube and dividing the inner tube into a rebound chamber and a compression chamber; a piston rod connected to the piston assembly and extending through the rebound chamber and the rod guide; and a compensation chamber formed between the inner tube and the outer tube; wherein the compensation valve assembly comprises a first valve means allowing fluid flow from the compression chamber to the compensation chamber when fluid pressure in the compression chamber exceeds that in the compensation chamber by a predetermined amount, a second valve means allowing fluid flow from the compensation chamber to the compression chamber when fluid pressure in the compensation chamber exceeds that in the compression chamber by a predetermined amount, and a two part housing retaining the first and second valve means, the two part housing having a first part with a cylindrical outer wall having a free edge, and a second part with an annular outer wall having a circumferential groove, portions of the free edge being staked over into the groove to secure the two parts of the housing together, and portions of the cylindrical outer wall being trapped between the annular outer wall and the inner tube.

2. A suspension strut as claimed in Claim 1, wherein the annular outer wall of the second part of the two part housing comprises a first diameter part, a second diameter part, and a shoulder therebetween, the first diameter part having a diameter which is less than the second diameter part, and wherein the circumferential groove is formed in the first diameter part adjacent the shoulder.

3. A suspension strut as claimed in Claim 2, wherein the one end of the inner tube engages the shoulder.

4. A suspension strut as claimed in Claim 3, wherein the second diameter part of the second part of the two part housing is trapped between the one end of the inner tube and the one end of the outer tube.

5. A suspension strut as claimed in any one of Claims 1 to 5, wherein the first part of the two part housing is substantially cup-shaped, and wherein the second part is substantially annular.

6. A suspension strut substantially as herein described with reference to, and as shown in, the accompanying drawings.