WO2006010207A1

WO2006010207A1 - Cooling of vehicle suspension systems

Info

Publication number: WO2006010207A1
Application number: PCT/AU2005/001100
Authority: WO
Inventors: Graeme Kershaw Robertson
Original assignee: Graeme Kershaw Robertson
Priority date: 2004-07-29
Filing date: 2005-07-27
Publication date: 2006-02-02

Abstract

A vehicle suspension has a motion damping unit (10) that is fluid-filled in operation and includes a pair of telescopic relatively moveable tube parts (12, 14)and valving (26) permitting flow of fluid between the tube parts (12,14). The tube parts (12, 14)are arranged for relative retracting and extending movement during which fluid is forced through said valving (26) at predetermined controlled flow rates so as to dampen the movement. The unit (10) further includes a fluid cooling circuit (60) having a first flow path (50) through the valving (26) between a primary chamber (29) of one of the tubes (14) and an annular, intermediate chamber (52). The fluid is forced along the flow path (50) during relative movement of the tubes (12, 14) in one direction to thereby pump the fluid in the fluid cooling circuit (60) which has means for cooling the fluid as it is circulated.

Description

Cooling of vehicle suspension systems

Field of the Invention

This invention relates generally to vehicle suspension systems, especially suspension systems of a type suitable for use in heavy duty applications such as off-road racing vehicles. However, the principals of the invention are equally applicable to other applications, such as suspension systems for motor bikes and other vehicles.

Background Art

A well known difficulty with suspension systems, particularly those employed in off-road racing vehicles such as described in international patent application WO 02/27211, is over-heating of suspension components, especially reciprocating components such as fluid or gas cushioning damping units. Local temperatures of up to 200⁰C or even higher have been observed: at these temperatures consequential effects such as local or bulk vaporization, gas expansion and seal failure tend to diminish the effectiveness of a suspension system and may even result in partial or substantially complete failure. Conventional cooling devices such as heat dissipation fins, cooling fluid jackets, and forced ventilation can be useful in reducing peak temperatures but have been found wanting under heavy load conditions.

It is therefore an object of the invention to ameliorate the heating of vehicle suspension systems under load in an effective and sufficient manner.

It is also desirable to provide a vehicle suspension system apparatus that is relatively simple in structure and economical to incorporate into a suspension system.

It is also desirable to provide in a fluid-filled, motion damping, reciprocating suspension component a simple means to minimize temperature build-up.

It is also desirable to provide an improved oleo-pneumatic, motion damping, suspension component having integral cooling to reduce undue temperature increase in the hydraulic fluid. It is also desirable to provide a reciprocating, oil-filled motion damping suspension component that is relatively simple and efficient in operation.

Summary of the Invention

According to one aspect of the invention there is provided a vehicle suspension apparatus, including: relatively reciprocably moveable first and second parts; motion damping means that includes valve means through which fluid is forced, at respective predetermined controlled flow rates, during said relative reciprocal movement of said parts so as to dampen said movement; a fluid cooling circuit including a first fluid flow path associated with said valve means whereby, during said relative reciprocal movement in at least one direction, a portion of said fluid is forced along said first flow path, whereby to pump the fluid in said fluid cooling circuit; and cooling means for cooling said fluid circulated in said cooling circuit.

The invention further provides, in a second aspect, a vehicle suspension apparatus including motion damping means that is fluid-filled in operation and has a pair of relatively moveable parts and valve means permitting flow of said fluid between said parts, said parts comprising a first part and a second part in which the first part is receivable, whereby the parts are arranged for relative retracting and extending movement during which fluid is forced through said valve means at respective predetermined controlled flow rates so as to dampen the movement; wherein said relatively moveable parts contain respective primary chambers for said fluid, and said first part is smaller in cross-section than said second part to define an intermediate chamber at least partly about the first part within the second part; and wherein said apparatus further includes a fluid cooling circuit having a first flow path through said valve means, between said primary chamber of the second part and said intermediate chamber, along which first flow path said fluid is forced during said movement in one direction, whereby to pump the fluid in said fluid cooling circuit, and a second flow path between said primary chamber of the second part and said intermediate chamber, which second flow path has means for cooling said fluid as it is circulated along said second flow path during operation of the apparatus. Preferably, said fluid cooling circuit includes one or more one-way or non-return valves for determining a direction of flow of the fluid in the cooling circuit.

Desirably, the circulation of said fluid in said cooling circuit does not substantially diminish the damping action of said motion damping means, or otherwise compromise the performance of the suspension apparatus.

The cooling means may comprise, for example, fins, a heat-exchanger, a labyrinthine flow path or any other suitable arrangement to allow said fluid to shed or dissipate heat to the environs or to another medium.

Advantageously, the first and second parts comprise telescopically interengaged tubes respectively of relatively smaller and larger diameter. The valve means is then conveniently provided in a valve body fixed at an inner end of the tube comprising said first part.

The valve means preferably includes respective sets of shims in part determining said respective predetermined controlled flow rates and further determining the respective directions of flow.

Advantageously, the apparatus further includes pressurised gas cushioning means including structure defining a first cavity for storing a pressurised gas and a second cavity for storing a fluid under pressure, and a floating piston sealingly separating said cavities, wherein the second cavity is in fluid flow communication with the motion damping means. The aforesaid movement is such that when said relatively moveable parts relatively extend, fluid is caused to flow from the second cavity of the pressurised gas cushioning means to the damping means whereby gas pressure in the first cavity moves the floating piston to reduce the gas pressure in the first cavity, and when the parts relatively retract, fluid is caused to flow from the damping means to the second cavity whereby to move the floating piston to increase the gas pressure of the gas in the first cavity.

In a convenient configuration, the first part of the motion damping means and the aforesaid structure of the pressurised gas cushioning means are integral whereby the second cavity and the primary chamber of the first part comprise a single chamber. More conveniently, the first part of the motion damping means and the structure of the pressurised gas cushioning means are provided by a single tube.

Preferably, the valve means is such that the respective predetermined controlled flow rates in the respective directions are different whereby to vary the damping characteristics according to whether the movement is relative retracting or extending movement.

It will be seen that, in preferred forms, the invention entails the concept of utilising the suspension unit itself as it is caused to move, in use, as the power source in a secondary fluid circuit in which one or more side streams of the working fluid are circulated and cooled.

Brief Description of the Drawing

The invention will be further described, by way of example only, with reference to the accompanying drawing, which is an axial cross-sectional view of vehicle suspension apparatus according to an embodiment of the invention.

Description of Preferred Embodiments

The illustrated embodiment of vehicle suspension apparatus is an integral suspension unit that would typically be one of a number of such units collectively providing a suspension system in a vehicle such as, for example, as described in the international patent publication WO 02/27211. The units may be acting individually or be linked in a fluid circuit to provide a managed and balanced suspension response.

The suspension unit 10 has a first cylindrical tube 12 telescopically received within a second cylindrical tube 14 so that the two tubes are mutually reciprocably moveable. Tube 12 is connected to tube 14 through a head 13 of tube 14 that includes a sealing configuration 17 about tube 12. Tube 12 is provided, in this case at the outboard or proximal end, with a filling valve 18 for introducing gas, such as air, nitrogen or similar, under pressure into the tube 12 to fill a first cavity or chamber 20 defined by the tube 12 at the proximal end of tube 12 for storing gas under pressure. A double- sided floating piston 22, with O-ring seals 22a, is provided intermediate the ends of tube 12. The first chamber 20 is formed between the filling valve 18 and the piston 22. A second chamber 24 is formed between piston 22 and the inner or distal end of tube 12. Hydraulic fluid fills the second chamber 24 of tube 12.

A double-acting valve arrangement 26 is provided in a valve body 25 at or towards the inner or distal end of tube 12. Valve body 25 slidably engages the cylindrical interior surface 15 of outer tube 14 and separates the chamber 24 from a chamber 29 defined within tube 14 between valve body 25 and an end cap 27 that seals the end of the tube 14. Elsewhere in this specification, chambers 24 and 29 are referred to as the primary chambers of tubes 12 and 14, respectively. When relative movement between the tubes 12 and 14 takes place, due to operation of the suspension components, the valve body 25 moves through the hydraulic fluid or the hydraulic fluid moves through the valve body in accordance with corresponding movement of tube 12, depending on whether the valve body 2 is fixed or free to move. Preferably, the valve body 25 is fixed about the end of tube 12 by transverse fastening screws (not shown) and moves therewith.

Tube 12 is appreciably smaller in cross-section than the tube 14 so that an intermediate variable-volume annular chamber 52 is provided within the tube 14 and about the tube 12 between the head 13 and the valve body 2.

The individual valving of the valve arrangement 26 is such as to allow fluid to flow in one direction at one rate when tube 12 moves in a first axial direction relative to the tube 14 and to flow in the opposite direction at a second rate when tube 12 moves in the opposite relative direction. The rate of movement of fluid through the valving is dependent on the number, size and arrangement of the apertures, ports or ducts 40, 42, 50, and on any flow control elements, which, in this embodiment comprise shims 4 and 55, forming the actual valving of valve arrangement 26. In other arrangements, the valving may comprise one-way valves of a different type, such as spring loaded ball valves.

More specifically, when the unit 10 is under compression thus causing the tubes 12 and 14 to relatively retract, the internal enclosed volume defined by the two tubes 12 and 14 and the respective ends is reduced. This causes fluid to be forced from the chamber 29 through a series of obliquely inclined ports 40 formed in the valve body 25 and passed uplifting shims 54 into chamber 24. As the volume of fluid being forced into chamber 24 increases, piston 22 travels axially along the inside wall of tube 12 towards the outboard or proximal end of this tube, thereby further compressing the gas in chamber 20 and increasing the internal pressure within component . This in turn offers increasing resistance to further relative movement of tubes 12 and 14 , thus limiting the amount of travel of tube 14. At the same time, as the valve body moves towards the head 13 of the tube 14, fluid within the intermediate chamber 52 is pumped therefrom into the cooling circuit 60, the annular valve shim set 57 acting to close the ducts 50.

On extension or rebound, the annular non-return shim set 57 in chamber 52 opens the ducts 50 so that fluid is able to pass into the chamber 52, and shims 54 close the ports 40, and the compressed gas in the chamber 20 causes the piston 22 to move thereby causing fluid to flow from chamber 24 into chamber 29 through a second series of oblique ports 42 controlled by shims 55.

Both ends of the integrated unit 10 are provided with suitable fittings such as the fitting eye 31 to enable the unit 10 to be located in place as part of the suspension system of a motor vehicle or the like. It is to be noted that any suitable fitting 27 can be provided at either or both ends of this form of the unit: exemplary fittings are illustrated.

In operation of this embodiment of the suspension unit 10, the outboard end of damping tube 14 is mounted to suspension components of the vehicle, or to other components by which the unit is connected either directly or indirectly to a road wheel of the vehicle. As the wheel traverses the ground, the tube 14 moves in accordance with the relative vertical movement of the vehicle wheel as it moves over the terrain. The outboard end of tube 12 may be connected to the chassis or body work of the motor vehicle, or other fixed component, and is thus relatively fixed in place.

With the tube 12 being of a relatively large diameter relative to that of the tube 14 such that the volume of the intermediate chamber 52 is minimised, the unit is of the general kind disclosed in international patent publication WO 02/27211 and is capable of independently supporting a suspended load. In other cases where tube 12 is relatively much smaller, or is a solid shaft, the unit has utility as a shock absorber auxiliary to primary suspension devices such as suspension springs.

When the road wheel returns to its normal position, such as for example, when rebounding or when encountering a trough or crest in the road, the length of combined unit 10 is increased by tubes 12 and 14 telescopically expanding with respect to each other, thereby allowing fluid to move from chamber 24 into tube 14, which reduces the amount of fluid in chamber 24 allowing piston 22 to move under the increased gas pressure of the compressed gas stored in chamber , which in turn reduces the compression or gas pressure of the gas in chamber . Further fluid is pumped into tube 14 until all of the pressures equilibrate. The rate at which fluid can flow through valve arrangement 26 limits the amount of travel of the road wheel in the substantially vertically downward direction.

The annular chamber 52 and outer ducts 50 form part of a fluid cooling circuit indicated generally at 60 that is effective in helping to prevent the suspension unit 10 from reaching excessive temperatures when working in heavy duty conditions such as off-road racing. Circuit 60 further includes a second, external, flow path 62 between chamber 52 and chamber 29 that incorporates, firstly, respective one-way or non-return valves 64 and 65 at the outlet from chamber 52 and the intake to chamber 29, and, secondly, a cooling means 100 of any suitable type for cooling the fluid in circuit 60. Suitable cooling units 100 comprise, for example, cooling fins, a heat-exchanger, a labyrinthine flow path or any other suitable arrangement to allow the fluid to dissipate or shed heat to the environs or to another medium.

It will be understood that the illustrated arrangement utilises the pumping action of the outer part of the valve body 25 as the driving energy source in a side circuit 60 in which a proportion of the hydraulic fluid in the system is systematically and continuously cooled with each cycle of movement of the suspension unit 10 without substantially restricting the performance of the suspension. It is found empirically that the arrangement can lower peak temperatures in a vehicle suspension system under severe load, for example, in off-road racing, from temperatures of the order of 200°C to a figure nearer ambient temperature.

It has been observed that, although the unit is pumping a proportion of the working fluid through the side circuit, the performance of the suspension system is not compromised, and the performance of the damping function in particular is not substantially diminished. For this outcome, chamber 52 is preferably of a volume substantially smaller than the volumes of either chamber 24 or chamber 29. It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. AU of these different combinations constitute various alternative aspects of the invention.

Claims

1. A vehicle suspension apparatus, including: relatively reciprocably moveable first and second parts; motion damping means that includes valve means through which fluid is forced, at respective predetermined controlled flow rates, during said relative reciprocal movement of said parts so as to dampen said movement; a fluid cooling circuit including a first fluid flow path associated with said valve means whereby, during said relative reciprocal movement in at least one direction, a portion of said fluid is forced along said first flow path, whereby to pump the fluid in said fluid cooling circuit; and cooling means for cooling said fluid circulated in said cooling circuit.

2. A vehicle suspension apparatus according to claim 1 wherein said first fluid flow path includes a non-return valve controlling movement of fluid through the first fluid flow path.

3. A vehicle suspension apparatus according to claim 1 or claim 2 wherein the cooling means comprises one or more of heat radiating fins, a heat-exchanger, and a labyrinthine flow path which dissipates heat from the fluid to the environs or to another medium.

4. A vehicle suspension apparatus according to any one of claims 1 to 3 wherein the first and second parts comprise telescopically interengaged tubes respectively of relatively smaller and larger diameter.

5. A vehicle suspension apparatus according to claim 4 wherein the valve means is provided in a valve body fixed at an inner end of the tube comprising said first part.

6. A vehicle suspension apparatus according to any one of claims 1 to 5 wherein the valve means includes respective sets of shims in part determining said respective predetermined controlled flow rates and further determining the respective directions of flow of fluid through said valve means during said reciprocal movement.

7. A vehicle suspension apparatus according to any one of claims 1 to 6 wherein said first fluid flow path is incorporated in said valve means.

8. A vehicle suspension apparatus according to any one of claims 1 to 7 wherein said fluid cooling circuit includes one or more one-way valves to confine fluid flow to one direction in the cooling circuit.

9. A vehicle suspension apparatus according to any one of claims 1 to 8 wherein the first and second parts comprise telescopically interengaged tubes respectively of relatively smaller and larger diameter defining therebetween an annular chamber, said valve means is mounted on an inner end of the smaller diameter tube and includes passageways controlled by shims to control the flow of fluid through the valve means, the valve means further including said first fluid flow path comprising one or more further passageways communicating with said annular chamber, said further passageways incorporating non-return valves thereby forming a pump for fluid through the first fluid path upon relative reciprocal movement of said tubes.

10. A vehicle suspension apparatus according to claim 8 wherein said fluid cooling circuit includes a fluid outlet communicating with said annular chamber and a fluid inlet communicating with a chamber defined by said large diameter tube.

11. A vehicle suspension apparatus according to any one of claim 1 to 10 wherein the apparatus further includes pressurised gas cushioning means including structure defining a first cavity for storing a pressurised gas and a second cavity for storing a fluid under pressure, and a floating piston sealingly separating said cavities, wherein the second cavity is in fluid flow communication with the motion damping means.

12. A vehicle suspension apparatus according to claim 11 wherein when said relatively reciprocably moveable parts relatively extend, fluid is caused to flow from the second cavity of the pressurised gas cushioning means to the damping means whereby gas pressure in the first cavity moves the floating piston to reduce the gas pressure in the first cavity, and when the parts relatively retract, fluid is caused to flow from the damping means to the second cavity whereby to move the floating piston to increase the gas pressure of the gas in the first cavity.

13. A vehicle suspension apparatus according to claim 12 wherein the first part of the motion damping means and said structure of the pressurised gas cushioning means are integral whereby the second cavity and the primary chamber of the first part comprise a single chamber.

14. A vehicle suspension apparatus according to claim 12 or claim 13 wherein the first part of the motion damping means and said structure of the pressurised gas cushioning means are provided by a single tube.

15. A vehicle suspension apparatus according to any one of claims 1 to 14 wherein the valve means is formed such that the respective predetermined controlled flow rates in the respective directions are different whereby to vary the damping characteristics according to whether the relatively reciprocal movement is relative retracting or extending movement.

16. A vehicle suspension apparatus including motion damping means that is fluid- filled in operation and has a pair of relatively moveable parts and valve means permitting flow of said fluid between said parts, said parts comprising a first part and a second part in which the first part is receivable, whereby the parts are arranged for relative retracting and extending movement during which fluid is forced through said valve means at respective predetermined controlled flow rates so as to dampen the movement; wherein said relatively moveable parts contain respective primary chambers for said fluid, and said first part is smaller in cross-section than said second part to define an intermediate chamber at least partly about the first part within the second part; and wherein said apparatus further includes a fluid cooling circuit having a first flow path through said valve means, between said primary chamber of the second part and said intermediate chamber, along which first flow path said fluid is forced during said movement in one direction, whereby to pump the fluid in said fluid cooling circuit, and a second flow path between said primary chamber of the second part and said intermediate chamber, which second flow path has means for cooling said fluid as it is circulated along said second flow path during operation of the apparatus.

17. A vehicle suspension apparatus according to claim 16 wherein said fluid cooling circuit includes one or more non-return valves for controlling a direction of flow of the fluid in the cooling circuit.

18. A vehicle suspension apparatus according to claim 16 wherein the circulation of said fluid in said cooling circuit does not substantially diminish the damping action of said motion damping means.

19. A vehicle suspension apparatus according to any one of claims 16 to 18 wherein said fluid cooling circuit has cooling means comprises one or more of heat radiating fins, a heat-exchanger, and a labyrinthine flow path which dissipates heat from the fluid to the environs or to another medium.

20. A vehicle suspension apparatus according to any one of claims 16 to 19 wherein the first and second parts comprise telescopically interengaged tubes respectively of relatively smaller and larger diameter.

21. A vehicle suspension apparatus according to claim 20 wherein the valve means is provided in a valve body fixed at an inner end of the tube comprising said first part.

22. A vehicle suspension apparatus according to any one of claims 16 to 21 wherein the valve means includes respective sets of shims in part determining said respective predetermined controlled flow rates and further determining the respective directions of flow of fluid through said valve means during said relative movement.

23. A vehicle suspension apparatus according to any one of claims 16 to 22 wherein the first and second parts comprise telescopically interengaged tubes respectively of relatively smaller and larger diameter defining therebetween said intermediate chamber, said valve means being mounted on an inner end of the smaller diameter tube.

24. A vehicle suspension apparatus according to any one of claim 16 to 23 wherein the apparatus further includes pressurised gas cushioning means including structure defining a first cavity for storing a pressurised gas and a second cavity for storing a fluid under pressure, and a floating piston sealingly separating said cavities, wherein the second cavity is in fluid flow communication with the motion damping means.

25. A vehicle suspension apparatus according to claim 24 wherein when said relatively moveable parts relatively extend, fluid is caused to flow from the second cavity of the pressurised gas cushioning means to the damping means whereby gas pressure in the first cavity moves the floating piston to reduce the gas pressure in the first cavity, and when the parts relatively retract, fluid is caused to flow from the damping means to the second cavity whereby to move the floating piston to increase the gas pressure of the gas in the first cavity.

26. A vehicle suspension apparatus according to claim 25 wherein the first part of the motion damping means and said structure of the pressurised gas cushioning means are integral whereby the second cavity and the primary chamber of the first part comprise a single chamber.

27. A vehicle suspension apparatus substantially as hereinbefore described with reference to the accompanying drawings.