GB2302929A

GB2302929A - Shock absorber

Info

Publication number: GB2302929A
Application number: GB9513410A
Authority: GB
Inventors: Antonio Perez De La Las Arjona; Francisco Javier Sanch Jimenez
Original assignee: ACG ESPANA SA
Current assignee: ACG ESPANA SA
Priority date: 1995-06-30
Filing date: 1995-06-30
Publication date: 1997-02-05
Anticipated expiration: 2015-06-30
Also published as: GB9513410D0; GB2302929B

Abstract

A shock absorber comprising an outer tube (12); a rod guide (22) positioned at one end (30) of the outer tube, the one end being bent over to retain the rod guide, and the rod guide having an outer peripheral surface (44) in contact with the outer tube, the outer peripheral surface having at least one circumferentially extending groove (48) formed therein; a piston rod (18) extending through the rod guide and having a piston attached thereto within the outer tube; and a ring (50) positioned around the outer tube adjacent the outer peripheral surface of the rod guide; wherein the outer tube has a groove (56) formed therein which extends into the groove in the rod guide; and wherein the ring has a groove (54) formed therein which extends into the groove in the outer tube.

Description

SHOCK ABSORBER The present invention relates to a shock absorber or hydraulic damper for use in a suspension system of a motor vehicle.

GB-A-2104186 describes a shock absorber having a thin walled outer tube which is closed at one end by the combination of a piston rod guide and an end cap. The end cap is secured in place by deforming the outer wall of the end cap and the outer tube into a groove in the piston rod guide. The groove contains an O-ring seal to form a seal between the rod guide and the outer tube. It has been found that this arrangement is liable to fail if the piston rod guide is subjected to a force tending to push the piston rod guide in an axial direction out of the outer tube.

It is an object of the present invention to provide an arrangement in which the risk of this type of failure is substantially reduced.

A shock absorber in accordance with the present invention comprises an outer tube; a rod guide positioned at one end of the outer tube, the one end being bent over to retain the rod guide, and the rod guide having an outer peripheral surface in contact with the outer tube, the outer peripheral surface having at least one circumferentially extending groove formed therein; a piston rod extending through the rod guide and having a piston attached thereto within the outer tube; and a ring positioned around the outer tube adjacent the outer peripheral surface of the rod guide; wherein the outer tube has a groove formed therein which extends into the groove in the rod guide; and wherein the ring has a groove formed therein which extends into the groove in the outer tube.

When compared to the above mentioned prior art arrangement, the arrangement of the present invention has a higher resistance to failure if the piston rod guide is subjected to a force in the axial direction which tries to push the piston rod guide out of the outer tube.

The present invention is applicable for shock absorbers which comprise an inner tube and an outer tube (sometimes referred to as twin tube dampers) or shock absorbers having a single tube (sometimes referred to as monotube dampers).

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 shock absorber in accordance with the present invention; and Figure 2 is an enlarged cross-sectional view of one end of the shock absorber of Figure 1.

Referring to the drawings, the shock absorber 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 20, and a rod guide 22. The piston assembly 16, the compensation valve 20 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 inner tube 14 is substantially closed at one end 24 by the compensation valve 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, and is substantially closed at the other end 30 (the open end) by the rod guide 22 and by pushing or bending over the end 30 of the tube. 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. 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 shock absorber 10 is mounted in a motor vehicle (not shown) in a standard manner.

Referring more particularly to Figure 2, the end 30 of the outer tube 12 is closed by the rod guide 22 and a seal 42 positioned between the rod guide and the bent over end 30 of the outer tube. The seal 42 extends to, and makes a sealing sliding fit with, the piston rod 18. The rod guide 22 has an outer peripheral surface 44 which extends around the axis L and engages the inner surface 46 of the outer tube 12.

The outer peripheral surface 44 has at least one, and preferably two, circumferentially extending grooves 48 formed therein. After assembly of the above mentioned components of the shock absorber 10, a separately formed ring 50 is positioned around the outer surface 52 of the outer tube 12 adjacent the rod guide 22. The ring 50 has a longitudinal axis on axis L. The ring 50 has an axial length H which is great enough to cover the adjacent grooves 48 in the rod guide 22. The ring 50 and the outer tube 12 are then crimped or rolled or otherwise worked to substantially simultaneously form grooves 54,56 respectively therein. The grooves 56 in the outer tube 12 extend into the grooves 48 in the rod guide 22. The grooves 54 in the ring 50 extend into the grooves 56 in the outer tube 12. This arrangement enhances the securing of the rod guide 22 in the outer tube 12.

The outer tube 12 is preferably formed from a thin-walled metal, preferably aluminium, and is preferably formed by impact extrusion. the preferred wall thickness is 0.5 to 1.5 mm. The ring 50 is preferably formed of the same material as the outer tube 12. The end 30 of the outer tube 12 is preferably closed by spin closing, as, for example, described in our GB patent application no. 9412806.3 filed 25 June 1994. As an alternative to the above described arrangement, the grooves 56 in the outer tube 12 may be formed in a first operation, and the grooves 54 in the ring 50 may be formed in a second subsequent operation.

Tests have shown that a shock absorber in accordance with the present invention can withstand higher forces on the rod guide in an axial direction tending to push the rod guide out of the outer tube than the shock absorber shown in GB-A-2104186. This is due to the combined effects of the grooves in the outer tube and the ring, and the bent over end of the outer tube. The use of seal 42, which provides the dual purpose of providing a seal between the rod guide 22 and the piston rod 18, and between the rod guide and the outer tube 12, reduces the number of seals when compared to the arrangement in GB-A-2104186. Further, this arrangement means that there is no need for O-ring seals in the grooves 48 in the rod guide 22, which allows a metal-to-metal connection between the rod guide and the outer tube 12 for increased strength in the connection when compared to GB-A-2104186.

Claims

Claims:

1. A shock absorber comprising an outer tube; a rod guide positioned at one end of the outer tube, the one end being bent over to retain the rod guide, and the rod guide having an outer peripheral surface in contact with the outer tube, the outer peripheral surface having at least one circumferentially extending groove formed therein; a piston rod extending through the rod guide and having a piston attached thereto within the outer tube; and a ring positioned around the outer tube adjacent the outer peripheral surface of the rod guide; wherein the outer tube has a groove formed therein which extends into the groove in the rod guide; and wherein the ring has a groove formed therein which extends into the groove in the outer tube.

2. A shock absorber as claimed in Claim 1 wherein the rod guide, the outer tube and the ring have two grooves formed therein.

3. A shock absorber as claimed in Claim 1 or Claim 2, wherein the groove or grooves in the outer tube and the ring have been formed substantially simultaneously.

4. A shock absorber as claimed in any one of Claims 1 to 3, wherein the outer tube and the ring are formed from the same material.

5. A shock absorber as claimed in any one of Claims 1 to 4, wherein the outer tube has been formed by impact extrusion.

6. A shock absorber as claimed in any one of Claims 1 to 5, wherein the outer tube is formed from aluminium.

7. A shock absorber as claimed in any one of Claims 1 to 6, wherein said one end of the outer tube has been bent over by spin closing.

8. A shock absorber substantially as herein described with reference to, and as shown in, the accompanying drawings.