WO1991013776A1

WO1991013776A1 - Spring arrangement in a vehicle

Info

Publication number: WO1991013776A1
Application number: PCT/SE1991/000197
Authority: WO
Inventors: Olle Hult
Original assignee: Saab-Scania Aktiebolag
Priority date: 1990-03-16
Filing date: 1991-03-15
Publication date: 1991-09-19
Also published as: SE9000940D0; DE4190458T; SE468124B; SE9000940L

Abstract

In a spring arrangement between a cab (1) and a vehicle frame (2), a telescopic shock absorber (4) is surrounded in the longitudinal direction by a bellows (16). In order detachably to fasten the shock absorber (4) to the bellows (16), use is made of a suspension element (36), for example a rubber ring, which must yield in order for it to be possible to free the shock absorber (4) from the bellows (16).

Description

Spring arrangement in a vehicle

The present invention relates to a spring arrangement in a vehicle, which spring arrangement comprises a telescopic shock absorber which is surrounded coaxially by at least one rigid tubular member, to which one end of a flexible tubular member is fixed in a gas-tight manner, which flexible tubular member is at its other end connected in a gas- tight manner to the shock absorber, the tubular members delimiting a space which is intended to be supplied with gaseous medium.

it is already known to arrange an air spring arrangement between a vehicle frame and a driving cab suspended on the frame, in order to afford the driver of the vehicle a comfortable working place even when the vehicle is driven on an uneven surface.

Known air spring arrangements consist of four air springs, one at each cab corner. Each air spring comprises a conventional telescopic shock absorber which connects the driving cab to the frame. The shock absorber, which comprises a damping cylinder and, projecting from this, a displaceable piston rod, is surrounded along the greater part of its length by a rubber bellows unit, one end part of which is passed through in a sealed manner by the displaceable piston rod while its other end part is detachably connected to the damping cylinder in order to make it possible to separate the shock absorber from the rubber bellows unit if any of the parts need to be repaired or exchanged. The rubber bellows unit delimits in this connection a space around the shock absorber, which space is supplied with air from the compressed-air system of the vehicle.

In order to prevent leakage of air between the rubber bellows unit and the displaceable piston, use is made of a conventional sliding seal which has proved to function excellently in practice. On the other hand, it has proved significantly more difficult to bring about a satisfactory detachable connection between the rubber bellows unit and the damping cylinder. Known connection arrangements have proved to be inadequate and are not always capable of detachably fixing in a satisfactory manner the position of the rubber bellows unit relative to the damping cylinder when the driving cab lurches relative to the frame. It has moreover proved to be very common that the rubber bellows unit in known solutions is displaced along the damping cylinder if for any reason there should be low air pressure in the rubber bellows unit. In this connection, the risk arises that the rubber bellows unit is brought to take up such a position relative to the damping cylinder that a proportionately great leakage of air arises.

Much time and trouble have been devoted to developing locking screws, plastic snap closures, band clamps and the like in order detachably to fasten the rubber bellows unit to the damping cylinder but, in spite of this, it has proved to be difficult to obtain a constructional solution which solves the fastening problem in a satisfactory manner.

The aim of the present invention is to eliminate the abovementioned disadvantages. To this end, the invention is characterised in ^"that the shock absorber comprises a support surface, against which the rigid tubular member bears, the support surface preventing displacement movement of the rigid tubular member in a first axial direction of the shock absorber, and in that there is arranged radially between the shock absorber and the rigid tubular member at least one suspension element which interacts with the shock absorber and the rigid tubular member, the suspension element counteracting displacement movement of the rigid tubular member in a second axial direction of the shock absorber.

By using the invention, it is ensured that the shock absorber and the rubber bellows unit are connected to one another during all operating conditions of the vehicle and even if the air pressure should for any reason fall in the rubber bellows unit. If it is necessary to free the shock absorber from the rubber bellows unit, for example in order to repair or exchange any of the parts, this is also possible in a relatively simple manner. By using a suitable working method and/or a tool, it is in fact possible to force displacement movement on the parts relative to one another. Consequently, the suspension element yields so that it no longer retains the shock absorber on the rubber bellows unit. In addition to said advantages, the invention has simple parts which are inexpensive to manufacture and which allow simple assembly. In an advantageous embodiment of the invention, the suspension element is constituted by a rubber ring. In order to free the shock absorber from the rubber bellows unit, it is necessary that the rubber ring yields. Tests have shown that a rubber ring, used in this connection, offers unexpectedly great resistance to yielding when the cab lurches relative to the frame or in the event of low air pressure in the rubber bellows unit, as a result of which it renders more difficult, very effectively and in a manner not previously known, sliding apart of said parts relative to one another. By using a rubber ring, it is moreover possible in a simple manner to make it easier or more difficult to free the shock absorber from the rubber bellows unit. This is brought about by exchanging the existing rubber ring for a rubber ring made of softer or harder material.

Other features characterising the invention emerge from the following patent claims and the description below of an embodiment exemplifying the invention. The description is carried out with reference to the attached figures, in which :

Figure 1 shows a diagrammatic side view of an air spring according to the invention, which is arranged between a vehicle cab and a vehicle frame;

Figure 2 shows a partially cut-away front view of an air spring according to the invention;

Figure 3 shows a partially cut-away view of the lower part of an air spring according to the invention, and

Figure 4 shows a partially cut-away view of an alternative embodiment of an air spring according to the invention.

In Figure 1 , a vehicle cab 1 is shown, which is suspended in a sprung manner on a vehicle frame 2. Between the cab 1 and the frame 2, four air springs are mounted, one at each cab corner. In order to illustrate the present invention, only one air spring 3 is described below, namely that which is mounted at one of the front corners of the cab. In this connection, it is understood that the other air springs are constructed in the same manner as the air spring described. The air spring 3 comprises a conventional telescopic shock absorber 4 which consists inter alia of a damping cylinder 5 and, projecting from this, a displaceable piston rod 6. The damping cylinder 5 is designed with a bushing 7 which is passed through by a bolt connection 8 in order to fasten the shock absorber 4 between two plates 9 which extend in the longitudinal direction of the vehicle and are connected to the lower part of an attachment 10 fixed to the frame.

The piston rod 6 is fastened to a U-shaped stirrup 11 which is fastened by means of a bolt connection 12 to a stay 13 which forms part of the shell of the cab. At the bolt connection 12, one end of a leg 14, which extends in the longitudinal direction of the vehicle, is also fastened. The other end of the leg 14 is fastened in a rotationally fixed manner to one end of a rod 15 which extends through the upper part of the attachment 10 fixed to the frame and in the transverse direction of the vehicle in orderto damp lurches of the cab 1 relative to the frame 2. Since this "stabiliser" represents conventional technology which is not directly involved in the invention, it is not described or shown in greater detail.

The shock absorber 4 is surrounded along the greater part of its length by a flexible tubular member 16 which delimits a space 17 around the shock absorber 4, which space 17 is supplied with air through a hose or pipe 18 which is connected to the compressed-air system of the vehicle. Of the compressed-air system, only a diagrammaticaliy shown compressed-air tank 19 is reproduced in Figure 1. The flexible tubular member 16 is preferably manufactured from rubber in order to be capable of being pressed together or extended depending on the vibrations of the cab 1 and whether, which is the case in air springs with variable damping, air is being supplied to or removed from the air spring. Henceforward, the expression bellows is used in the description when the flexible tubular member 16 is intended.

In Figure 2, a clarified picture is shown of the air spring 3 and how it is connected to the cab 1 and the attachment 10 fixed to the frame respectively. The figure shows that the bellows 16, at its end which faces the cab 1, is threaded onto a spring seat 20 which bears against the U-shaped stirrup 11. The bellows 16 is fastened to the spring seat 20 by means of an annular fastening member 21 which surrounds the bellows 16 and presses it sealingly against the spring seat 20. The annular fastening member 21 is pressed onto the bellows 16 in the manufacture of the air spring 3 in orderto ensure reliable gas-tight sealing between the parts throughout the entire life of the air spring 3.

The spring seat 20 is designed with a hole 22 which is passed through by the piston rod 6 of the shock absorber 4. Between the spring seat 20 and the piston rod 6, a sliding seal 23 is arranged to prevent leakage of air between the parts 6, 20. A nut 24 is moreover threaded onto the piston rod 6 and presses the spring seat 20 against the U- shaped stirrup 11 and thus connects the air spring 3 to the cab 1.

It emerges further from Figure 2 that the bellows 16 is turned inwards and upwards and connected to the upper end of a rigid tubular member 25 which surrounds coaxially the damping cylinder 5 of the shock absorber 4 and delimits a gap 26 between the parts 25, 5. Henceforward, the expression sleeve is used when the rigid tubular member 25 is intended. The bellows 16 is connected to the sleeve 25 with the aid of an annular fastening member 27 which, like the previously mentioned fastening member 21 , is pressed onto the bellows 16 in the manufacture of the air spring 3.

The sleeve 25, which is preferably manufactured from plastic, is designed, at its end which faces the frame, with a wall 28 which is directed radially towards the longitudinal axis of the shock absorber and which constitutes a support surface for a sleeve body 30 which is connected in a fixed manner to the damping cylinder 5 of the shock absorber 4. As emerges from Figures 2 and 3, the sleeve body 30 is designed with a projecting flange 31 which in turn is designed with a support surface 32, against which a wall surface 33 formed on the sleeve 25 bears. The support surface 32 prevents in this connection displacement movement of the sleeve 25 relative to the shock absorber 4 in the downward axial direction. As emerges most clearly from Figure 3, the sleeve body 30 is moreover designed with an upper and lower, in the axial direction, circular groove 34, 35, each of which constitutes a bearing surface for a suspension element 36, 37 arranged in the radial direction. The suspension elements 36, 37 are preferably constituted by rubber rings and advantageously have circular or at least rounded cross- sectional shape.

The lower suspension element 37 interacts with the wall 28 in order to prevent leakage of air between the sleeve 25 and the sleeve body 30. The upper suspension element 36, which has an external diameter which is greater than the diameter of the continuous hole 29, interacts on the other hand with a wall surface 38 formed on the sleeve 25. By means of this interaction, the shock absorber 4 is detachably fixed relative to the sleeve 25 and thus relative to the air bellows 16 also.

In Figure 4, an alternative embodiment of the sleeve 25 and the sleeve body 30 is shown. It emerges from the figure that it is also possible to design the upper and lower circular groove 34, 35 respectively, and thus also to arrange the suspension elements 36, 37, in the sleeve 25. The lower suspension element 37 interacts in this connection with the sleeve body 30 in order to prevent leakage of air between the sleeve 25 and the sleeve body 30. The upper suspension element 36 interacts with a circular groove 39 in the sleeve body 30 in order detachably to fix the shock absorber 4 relative to the sleeve 25/the air bellows 16. It is of course possible, if so desired, to arrange one suspension element on one of the parts 25, 30 and the second suspension element on the second of the parts 25, 30. Other embodiments are also possible without the inventive idea being lost.

When the vehicle is driven on an uneven surface, the air spring arrangement described damps the transmission of shocks, which disturb the comfort, between the frame 2 and the cab 1. In spite of this, the cab 1 of course lurches, at least limitedly, relative to the frame 2. During these lurches, the sleeve 25 the air bellows 16 and the shock absorber 4 tend to be displaced relative to one another in the direction which the arrow A indicates in

Figures 2, 3 and 4. Since the wall surface 38 of the sleeve 25 in Figure 3 bears against the upper suspension element 36, the displacement movement is counteracted. In the alternative embodiment in Figure 4, the displacement movement is counteracted by virtue of the fact that the upper suspension element 36 bears against the edge 40 of the circular groove 39. In order that the shock absorber 4 and the bellows 16 slide apart, it is necessary that the suspension element 36 yields so much that its external diameter is adapted to the diameter of the continuous hole 29. Tests have shown that a rubber ring offers unexpectedly great resistance to yielding, as a result of which it very effectively renders more difficult sliding apart of said parts relative to one another during operation of the vehicle but nevertheless makes it possible that the parts can be separated from one another in the event of need for repair or the like.

The course of events described here arises not only when the cab lurches during operation of the vehicle but also if the air pressure should for any reason fall in the air spring.

In the construction described above, it is possible in a simple manner to make it easier or more difficult to free the shock absorber from the sleeve, or in fact from the whole unit of which the sleeve forms part. This is brought about by exchanging the existing upper suspension element, that is to say the rubber ring in this case, for a rubber ring made of softer or harder material.

Within the scope of this invention, it is possible to design the upper suspension element in another manner than has been exemplified in the description. It is, for example, possible to make use of any form of "piston ring" since one of these, at least in the piston of a vehicle engine, has such elastic properties as are desired in this invention. Other embodiments of elastic members are also possible without the inventive idea being lost.

The arrangement described can advantageously be used in a vehicle cab which is suspended in a sprung manner as has been exemplified in the description. It is possible, however, to use an air spring with the arrangement according to the invention between, for example, the body and a front or rear axle on a passenger car. There is in fact in principle no great difference between the air spring arrangements which are used in the two areas of application.

Claims

Patent Claims

1. Spring arrangement in a vehicle, which spring arrangement comprises a telescopic shock absorber (4) which is surrounded coaxiaily by at least one rigid tubular member (25), to which one end of a flexible tubular member (16) is fixed in a gas-tight manner, which flexible tubular member (16) is at its other end connected in a gas-tight mannerto the shock absorber (4), the tubular members (16, 25) delimiting a closed space (17) which is intended to be supplied with gaseous medium, characterised in that the shock absorber (4) comprises a support surface (32), against which the rigid tubular member (25) bears, the support surface (32) preventing displacement movement of the rigid tubular member (25) in a first axial direction of the shock absorber, and in that there is arranged radially between the shock absorber (4) and the rigid tubular member (25) at least one suspension element (36) which interacts with the shock absorber (4) and the rigid tubular member (25), the suspension element (36) counteracting displacement movement of the rigid tubular member (25) in a second axial direction of the shock absorber (4).

2. Spring arrangement according to claim , characterised in that the rigid tubular member (25) is designed with a wall (28) which surrounds a hole (29), through which the shock absorber (4) extends, which wall (28) is designed with a first wall surface (33) which bears against the support surface (32) and a second wall surface (38) which interacts with the suspension element (36) in orderto counteract displacement movement of the rigid tubular member (25) in the second axial direction of the shock absorber.

3. Spring arrangement according to claim 2, characterised in that the suspension element (36) is annular and has an external diameter which is greater than the diameter of the hole (29).

4. Spring arrangement according to claim 3, characterised in that the suspension element (36), upon demounting, has essentially the same diameter as the hole (29).

5. Spring arrangement according to claim 4, characterised in that the suspension element (36) is constituted by a rubber ring with circular or at least rounded cross-sectional shape.

6. Spring arrangement according to claim 2, characterised in that the suspension element (36) is fixed in a groove (34) on the shock absorber (4).

7. Spring arrangement according to claim 6, characterised in that the groove (34) is designed in a sleeve (30) which is connected in a fixed manner to the shock absorber (4).

8. Spring arrangement according to claim 2 and 7, characterised in that the support surface (32) is designed in the sleeve (30).

9. Spring arrangement according to claim 2, characterised in that the hole (29) constitutes a support surface for the shock absorber (4), there being arranged between the shock absorber (4) and the support surface a further suspension element (35), which suspension element (35) prevents leakage between the parts (29, 30).

10. Spring arrangement according to claim 9, characterised in that the suspension element (35) is constituted by a rubber ring.