FR2497551A1 - TELESCOPIC HYDRAULIC IMPACT SHOCK ABSORBER - Google Patents

Abstract

THE INVENTION RELATES TO A TELESCOPIC HYDRAULIC SHOCK ABSORBER. THIS SHOCK ABSORBER INCLUDES TWO COAXIAL TUBES 10, 12 DELIMING BETWEEN THEM AN INTERMEDIATE SPACE 18 SERVING AS A FLUID TANK, THE INTERIOR TUBE 12 FORMING A CYLINDER IN WHICH IS PROVIDED A PISTON LINKED TO A PISTON ROD 16. TO CENTER THE TUBES AND CLOSE THE TUBES. '' TOGETHER, A CAP CONSISTING OF TWO SHEET SLEEVES 20, 22 OF WHICH THE FIRST IS MOUNTED ON THE INTERNAL TUBE 12 AND CARRIES A CUSHION 42 FORCE INSERTED IN THE CYLINDRICAL PART 36 OF THE CUSHION HOLDER SLEEVE 20 AND OF WHICH THE SECOND INCLUDES A CYLINDRICAL PART 44 SURROUNDING WITH SET 45 THE FIRST SLEEVE AND A FLARED PART 46 WHICH ALLOWS THROUGH ITS TERMINAL PART 48, 50 CENTERING IN THE OUTER TUBE 10. THE INVENTION APPLIES TO HYDRAULIC SHOCK ABSORBERS OF THE DOUBLE TUBE TYPE.

Description

I

  The present invention relates to a hydraulic shock absorber

  telescopic port, of the double tube type, comprising coaxial tubes, namely an inner tube and an outer tube, which define between them an intermediate space, the inner tube constituting a cylinder for a piston provided with a rod which projects out of the upper end of the damper which it leaves sealed with a terminal annular cap, common to both tubes and centered in

  the upper end of the outer tube, this cap being housed axially

  between an annular shoulder of the upper end of the outer tube and the upper end of the inner tube and being coupled

  to the inner tube so as to center the latter, said end cap

  the annular ring being provided with a coaxial cylindrical central seat in which is retained a bearing made of a material with a low coefficient of friction, bearing in which the piston rod slides. In this

  which follows and in the appended claims, the terms "superior",

  "lower", and equivalents, are used in consideration of the position most frequently adopted by a damper in use in a suspension of a motor vehicle, position in which the upper end of the damper is that by which the piston rod

fate.

  The hydraulic dampers of the double tube type are mainly used in MacPherson suspensions, in which they

  constitute the amount of the suspension itself.

  In a suspension MacPherson type, the amount is subject to significant bending loads. In order not to give excessive dimensions to the upright, and in order to limit the weight of its components to the minimum necessary, the piston rod of the damper is made from a steel rod of relatively small dimensions if the we consider the bending loads that it must support. Under the effect of these loads, the rod of the damper is subjected to deformations in bending of a certain importance, where it follows that the pad, made of material with a low coefficient of friction, which serves to guide the rod in the annular end cap, is subject to very high contact pressures. These contact pressures are not uniformly distributed over the entire surface of the pad but concentrated mainly in

  two diametrically opposed zones lying in a parallel plane

  is related to the direction of vehicle travel, since bending loads occur most frequently in this direction due to acceleration and braking. In addition, lateral loads due to fast turns can create contact pressures

  excessively in different areas of the above-mentioned areas.

  Excessive contact pressures on the inner surface of the pad give rise to both abnormal wear in the

  areas of preferential contact and to some "stickiness" in the sliding

the damper rod.

  The annular end caps commonly used for double tube type dampers consist of rigid bodies normally formed by sintering steel powder. A body of this type prevents any deformation or change of orientation of the pad under the effect of bending stresses of the rod, contrary to what would be desirable to eliminate, or at least to reduce, the phenomenon of abnormal wear of the pad . A system in which the pad is supported on the annular end cap by means of a ball joint has already been tried. However,

  Such a solution is extremely expensive and therefore not

  tible to be adopted for mass production.

  The object of the present invention is to provide a shock absorber of the type mentioned at the beginning, in particular intended for suspensions of the MacPherson type, this damper having a terminal cap that can be manufactured simply and economically and allowing the pad "to accompany" the deformations. in particular flexural deformations,

of the damper rod.

  According to the invention, this is achieved by means of a damper of the type mentioned at the beginning, characterized in that the annular end cap has two separate coaxial sleeves in sheet metal, one being a spacer sleeve which has a lower part cylindrical and an annular upper edge for centering in the upper part of the outer tube and for axial support of an annular shoulder of the outer tube, the other sleeve being a bearing sleeve which comprises, near its lower end, a radial collar. external housing housed between the lower portion of the spacer sleeve and the upper portion of the inner tube, a tubular portion located inside the spacer sleeve and defining the cylindrical seat in which is retained the pad in which the rod slides, and a cylindrical peripheral skirt located in the intermediate space and in which is housed and centered the upper part of the ube inside and in that the

  tubular portion has an immobilizing portion which is located immediately

  immediately following the collar and which adjusts, with

  sation, in the lower portion of the spacer sleeve in which it is centered, and a projecting portion which extends into the spacer sleeve while leaving a circumferential clearance between it and this sleeve, this projecting portion ranging the immobilizing portion at a free upper end of the tubular portion. With this solution according to the invention, the pad in which the rod slides is mounted so as to protrude from the immobilizing zone of the bearing sleeve between the

  spacer sleeve and the inner tube.

  Another advantage of the invention lies in the fact that the end annular cap is formed by means of two steel-tipped sleeves, which is considerably lighter than a solid end cap made of sintered steel, and therefore leads to a weight reduction no

suspended from the suspension.

  The invention will be better understood and other features

  will appear with the following description and accompanying drawings

  o: - Figure I is a side view, in partial longitudinal section,

  of the upper part of a damper according to a form of embodiment

preferred embodiment of the invention;

  FIG. 2 is an exploded perspective view of the elements

  shown in Figure 1; and FIG. 3 represents a longitudinal section of a variant of a

  detail of the structure according to Figure 1.

  In FIGS. 1 and 2, a hydraulic telescopic damper

  The inner tube 12 constitutes the cylinder in which a piston provided with valves (not shown) can slide. To this piston, is rigidly connected a piston rod 16 which, by its end

  upper, protrudes out of the damper.

  Between the two tubes 10 and 12, there is an intermediate space

  18 which, in known manner, is intended to receive a portion of the oil coming from the inside of the chamber of the cylinder 12 during the

contraction of the shock absorber.

  In the upper part of the outer tube 10 is contained a structure constituting an annular end cap for the interconnection of the two tubes 10 and 12. This structure comprises two shaped shaped thick steel sleeves, generally designated

by references 20 and 22.

  The sleeve 20, called "cushion holder", comprises, near its lower end, a radial outer collar 24 which rests on the upper end of the inner tube 12. Starting from this radial collar 24, a cylindrical annular skirt 26 followed by a collar 28

  turned outwards, extends into the intermediate space 18.

  The upper end of the inner tube 12 is held and centered in the skirt 26. In order to maintain and maintain quality, the skirt 26 has a cylindrical inner surface 27 obtained by stamping. The outwardly facing collar 28 extends radially in the intermediate space and has a circular peripheral edge 30 which is immediately adjacent to the outer tube 10, for purposes which

will appear in the following.

  A tubular portion 32 extends upwardly from the radial collar 24. This tubular portion 32 comprises, from bottom to top, a short portion 34 with a large diameter and a longer portion 36

  having a slightly smaller diameter.

  The portion 34, which follows the collar 24, has an outer cylindrical surface 38 obtained by stamping. The surface 38 is coaxial with the surface 27. The tubular cylindrical portion 32 also has a cylindrical surface 40 obtained by stamping and is coaxial

to surfaces 27 and 28.

  The surface 40 constitutes a seat in which a pad 42 is force-fitted. This pad 42 is made of a material with a low coefficient of friction. Preferably, this pad is of a type

  well-known split, consisting of an annular body made of split steel

  tudinally wearing, on its inner surface, a coating of

  porous copper impregnated with polytetrafluoroethylene.

  The pad 42 constitutes a sliding surface for the

  rod 16, in the upper part of the damper.

  The sleeve 22, called the spacer sleeve, has a cylindrical portion 44 which surrounds the tubular portion 32 of the sleeve bearing sleeve 20. The portion 34 of the latter is fixed and centered, by its outer surface 38, in the lower portion of the portion

cylindrical 44.

  The cylindrical portion 44 of the spacer sleeve 22 has an inside diameter larger than the outside diameter of the cylindrical portion 36 of the bearing sleeve 22. Thus, there is

  a game or annular space 45 between the two portions 36 and 44.

  The cylindrical portion 44 extends around the tubular portion 32, substantially to the upper end thereof, beyond which the spacer sleeve has a portion

  flared 46 of substantially frustoconical shape.

  This flared portion 46 is connected, at its upper part, to

  a radial annular portion 48 to which is connected an annular skirt

50.

  The radial portion 48 has a flat upper annular surface 52. The skirt 50 has cylindrical surfaces, namely an inner surface 54 and an outer surface 56. The three surfaces 52,

  54 and 56 are preferably made by stamping. The perimeter area

  Phérique 56 is in contact with the inner surface of the outer tube 10

for centering purposes.

  The two surfaces 52 and 54 constitute a seat in which is housed, and centered, a metal reinforcing ring 58. This ring 58 constitutes a support for a lip seal 60, of a known type, which cooperates with the rod 16, this at the upper end of the damper. Above the skirt 50 and the ring 58, is formed, by discharge, an inwardly directed radial upper lip 62, which belongs to the outer tube 10. Between the upper face of the ring 58 and the lip 62 turned inwards, is clamped a flat sealing washer 64 which is made of rubber or the like and which hermetically seals the junction between outer tube 10 and

ring 58.

  The lip or shoulder 62 facing inwardly serves, inter alia, to maintain the correct axial and radial relative position of the inner and outer tubes 12 and 10, and of the two sleeves 20 and 22, the radial collar 24 of the sleeve 20 being housed between the ends

  corresponding to the tube 12 and the sleeve 22.

  In a variant, shown in Figure 3, the flared portion (again with reference 46) of the spacer sleeve terminates at its upper end by a radial wall 148 similar to the wall 48, but with an edge Peripheral circular cut-out 156 for centering with respect to the outer tube 10. This wall 148 has a flat upper surface 152 on which rests a reinforcement ring 158 similar to the ring 58, but with an outside diameter corresponding to the inside diameter of the tube 10. The assembly is again retained by an inwardly directed lip 62 of the outer tube 10, with the interposition of a flat sealing washer 164 placed between the lip 62 and

the ring 158.

  In the annular end cap formed by the sleeves 20 and 22, the space between the rod 16 and the flared portion 46 of the spacer sleeve 22 constitutes a collection trap for the oil rising, by displacement, between the tigSe 16 and the

  pad 42. In the flared portion 46, a circular opening is formed.

  66 by which excess oil can be discharged from this trap to

  the intermediate space 18. To allow the oil to reach easily

  the intermediate space 18, at least one notch 68 (or one or

  several openings of this type) is formed in part 28, radially

  outwardly, bearing sleeve 20.

  As can be seen in Figure 1, the pad 42 in

  which the sliding rod is retained only in the tuhu

  This tubular portion 36 is, in its entirety, protruding out of the immobilizing zone defined by the portion 34. The presence of the circumferential clearance 45 allows this projecting portion 36 to bend, relative to the immobilizing portion. 34, in all the radial planes passing through the longitudinal axis of the damper, to follow the flexion of the rod 16 under the effect of lateral loads. Because of this, the pressures exerted on the pad 42, because of the bending of the rod 16, are less intense insofar as they are distributed over larger areas than would be the case if the

  pad 42 was unable to perform lateral movements.

  The displacement of the pad 42 under the effect of the bending of the rod 16 may also include a component due to the bending of the spacer sleeve 22 and the inner tube 12. Due to this bending, the edges of the inner tube 12 and of the sleeve 32 which surrounds the neck 34 can be moved laterally. The contact of the edge 30 with the

  outer tube 10 prevents excessive lateral displacement.

  Of course, the embodiments described are not

  in no way limitative of the invention.

Claims (9)

  1. A telescopic hydraulic shock absorber, of the double tube type, comprising coaxial tubes, namely an inner tube and an outer tube, which define between them an intermediate space, the inner tube constituting a cylinder for a piston provided with a rod which protrudes out of the upper end of the damper which it leaves sealed with a terminal annular cap, common to both tubes and centered in the upper end of the tube   outside, this cap being housed axially between an annular shoulder   the upper end of the outer tube and the upper end   of the inner tube and being coupled to the inner tube so as to center the inner tube, said annular end cap being provided with a coaxial cylindrical central seat in which is retained a pad of a material with a low coefficient of friction, pad in which the piston rod slides, said damper being characterized in that the annular end cap comprises two coaxial t8le separate sleeves, one being a spacer sleeve (22) having a cylindrical lower portion (44) and an annular upper edge (50) for centering in the upper part of the outer tube (10) and for axial support of an annular shoulder (62) of the outer tube, the other sleeve (20) being a bearing sleeve which comprises, close to its lower end, an outer radial collar (24) housed between the   lower part of the spacer sleeve (22) and the upper part   the inner tube (12), a tubular portion (32) located inside the spacer sleeve (22) and defining the cylindrical seat (40) in which the bearing (42) is retained in which the stem (16) ), and a peripheral cylindrical skirt (26) located in the intermediate space (18) and in which is housed and centered the upper portion of the inner tube (12), and in that the tubular portion (36) comprises a portion immobilisante (34) which is located   immediately following the collar (24) and adjusts, with effect of immo-   in the lower part of the spacer sleeve (22) in which it is centered, and a projecting portion (36) which extends into the spacer sleeve (22) while leaving a circumferential clearance (45). ) between it and this sleeve, this portion   protrusion from the immobilizing portion (34) to a top end   free of the tubular portion (32).   2. Damper according to claim 1, characterized in that a slide bearing (42) is placed only inside the portion (36) projecting from the tubular portion (32) of the sleeve cushion holder (20).   3. Shock absorber according to one of the ravendicaticns 1 or 2, characterized in that aua skirt (26) of the sleeve porta-pad (20) has, at its lower end, a collar (28) tourrin ve-ars the outside, which extends radially in the intermediate space (18) and which has a   circular peripheral edge (30) directly adjacent to the outer tube laughter (10).   4. Damper according to any one of claims 1 to   3, characterized in that the shrink sleeve (22) has a lower cylindrical portion (44) which surrounds the tubular portion (36) of the bushing sleeve (20), and a flared upper portion (46) which connects to the lower cylindrical part and which has a   annular upper edge (56; 156) with centering effect.   Shock absorber according to Claim 4, characterized in that the upper portion (45) of the spacer sleeve (22) has at least one opening (66) for communicating with the intermediate space (18).   Shock absorber according to Claim 5, characterized in that the skirt (26) of the bearing sleeve (20) has at its end   lower, an outwardly extending collar (28) extending radially   in the intermediate space and which has a circular peripheral edge (30) directly adjacent to the outer tube (10), this collar having at least one opening or notch (68) for establishing a   communication with the intermediate space (18).   Shock absorber according to any one of Claims 1, 4   or 5, characterized in that the shoulder (62) of the upper end of the outer tube (10) is a lip of this tube, rotated radially inwards, in that the upper annular edge of the spacer sleeve (22) comprises a radial annular portion (48; 148) and in that between this radial portion and said inwardly facing lip are housed a reinforcing ring (58; 158) carried on the radial portion and supporting a lip seal (60) cooperating with the shank (16), and a sealing washer (64; 164) interposed between the reinforcing ring (58; 158) and said inwardly facing lip (62). 8. Shock absorber according to claim 7, characterized in that said radial annular portion (48) has a peripheral skirt.   cylindrical (50), for centering, interposed between the reinforcing ring   cement (58) and the region of the outer tube (10) immediately adjacent to the lip (62) facing inwardly. Shock absorber according to Claim 7, characterized in that the periphery of the reinforcing ring (158) meets the outer tube (10) in the region immediately adjacent to the lip (62) and in that said radial annular portion ( 148) has a peripheral circumferential edge (156) which is in contact with the outer tube (10) in a region immediately adjacent to that   encountered by the reinforcement ring (158).