SUSPENSION DEVICE FOR VEHICLES, COMPRISING A TELESCOPIC SHOCK ABSORBER AND AN AIR SPRING

Abstract: A suspension device for motor vehicles comprises a telescopic shock-absorber (2) and an air spring (3) which is arranged coaxially with the shock-absorber around the region of the seal between the cylinder (4) and the rod (6) of the shock-absorber (2). The air spring (3) defines a pneumatic chamber (25) of annular cross-section.

Description: The present invention relates to a suspension device for vehicles, according to the pre-characterising portion of the claim. From DE-A 2 014 593 - on which the preamble of the claim is based - it is known a suspension device comprising a telescopic shock absorber and an air spring coaxially arranged therewith, the spring comprising a casing which has an annular cross section in the region of the seal between the rod and the cylinder of the shock absorber. The casing of the spring comprises a rigid portion open at one end and having an annular outer wall and an annular inner wall, the latter being formed by the outer surface of the cylinder of the shock absorber. A flexible portion is fitted to the open end of the rigid portion and co-operates with an annular thrust member. The object of the present invention is to provide a suspension device of the above-mentioned type, having a simple structure and which allows to obtain a steep increase of stiffness when the spring goes near to its configuration of maximum compression. According to the present invention, this object is achieved by a suspension device having the features recited in the characterising portion of the claim. Further characteristics and advantages of the present invention will become clear from the detailed description which follows with reference to the appended drawing provided by way of non-limiting example and showing a partially-sectioned side elevational view of a suspension device according to the present invention. A suspension device is generally indicated 1 and is constituted by a telescopic shock-absorber 2 and an air spring 3 which is coaxial with the shock-absorber 2. In known manner, the shock-absorber 2 comprises a cylinder 4 with a piston 5 which is slidable therein and is fixed to a rod 6. The rod 6 projects from that end of the cylinder 4, indicated 7, which is at the top in the drawing . In correspondence with the end 7, the cylinder 4 carries a sealing ring 8 which, in known manner, effects the seal between the rod 6 and the cylinder 4. Two resilient bushes 9 for connection the body of the vehicle and to a wheel support (not illustrated in the drawing) are fixed to the lower end of the cylinder 4 and to the upper end of the rod 6. The air spring 3 includes a rigid casing 10 which is open at the top and is composed of an outer cylindrical wall 11 and an inner cylindrical wall 12 which are coaxial with each other and in their turn are coaxial with the shock-absorber 2. The rigid casing 10 is fixed to the cylinder 4 of the shock-absorber 2 and is provided at its lower end with an aperture 13 for connection to a compressed air source (not illustrated). An annular intermediate support plate 14 is situated in the rigid casing 10 and has its outer and inner circumferential edges welded to the outer wall 11 and the inner wall 12 of the casing 10, respectively. The support plate 14 has a plurality of holes 15, a resilient stop buffer 16 being located in each. Each buffer 16 has an inner through-hole 17 situated in correspondence with the respective hole 15, for the passage of the air through the intermediate plate 14. The plate 14 is also provided with a plurality of stiffening ribs 18. A flexible casing 19, which is open at the bottom, is fitted in correspondence with the upper opening of the rigid casing 10 and has a cylindrical outer wall 20 and a cylindrical inner wall 21. The outer wall 20 of the flexible casing 19 is fixed sealingly to the outer wall 11 of the rigid casing 10 by means of a ring 22. Similarly, the inner wall 21 of the flexible casing 19 is fixed sealingly to the inner wall 12 of the rigid casing 10 by means of a ring 23. The circumferential surfaces of contact between the flexible casing 19 and the rigid casing 10 are knurled 24 to improve their grip. The deformable casing 19, the rigid casing 10, and the intermediate support plate 14 define an annular chamber 25 which constitutes the active part of the spring 3. An annular thrust member 26, whose outer circumferential edge is formed as an axially-extending projection 27, is fixed to the upper end of the rod 6 and bears against the top of the deformable casing 19. The extreme operating configurations of the air spring 3 are shown in broken outline in the drawing. The upper broken line, indicated A, shows the configuration of the deformable casing 19 which corresponds to the maximum extension of the shock-absorber 2. The lower broken line, indicated B, shows the deformable casing 19 in correspondence with the maximum contraction of the shock-absorber 2. In this configuration, the annular projection 27 of the thrust member 26 reacts against the stop buffers 16. A generic operating configuration intermediate the extreme configurations described above is shown in continuous outline. As can be seen, the sealing ring 8 of the shock-absorber 2 is completely isolated from the pressurised region of the air spring 3 and sealing defects of the shock-absorber, with the consequent risk of admission of an unwanted pressure to the shock-absorber such as to alter its shock-absorbing characteristics, are therefore avoided.

Claims: A suspension device (1) for vehicles, comprising a telescopic shock-absorber (2) constituted by a cylinder (4) with a piston (5) which is slidable therein and is fixed to a rod (6) that projects sealingly from the cylinder (4), an air spring (3) arranged externally of the shock-absorber (2) and coaxially therewith, said air spring (3) comprising a casing (19) which is at least partially flexible and defines a pneumatic chamber (25), the pneumatic chamber (25) having an annular cross-section, at least in the region of a seal (8) between the rod (6) and the cylinder (4), wherein the casing (19) of the air spring (3) comprises: a rigid axially extending portion (10) which is fixed to either the cylinder (4) or the rod (6) of the shock-absorber (2) and is open at one end, the rigid portions (10) having an annular radially inner wall (12) and an annular radially outer wall (11) which are coaxial with each other, a flexible axially extending portion (19) which is fitted to the open end of the rigid-walled portion (10) and on the top of which bears an annular thrust member (26) carried by the other of either the rod (6) or the cylinder (4) respectively, the flexible portion (19) having an annular conformation with radially outer (20) and inner (21) peripheral edges fixed sealingly to the annular outer wall (11) and the annular inner wall (12) of the rigid portion (10), respectively, characterised in that an intermediate annular support plate (14) is situated within the rigid axial portion (10) and carries one or more resilient stop buffers (16), and in that the periphery of the thrust member (26) is bent axially(27) to cooperate with the buffers (16).

Inventors: GANDIGLIO, ROMOLO, URBINATI, MAURIZIO
Applicants: FIAT AUTO S.P.A.
Application year: 1989
Main classification: F16F9
IPC codes: B60G15, F16F9