GB2396340A

GB2396340A - Vehicle suspension with electrical generator

Info

Publication number: GB2396340A
Application number: GB0229536A
Authority: GB
Inventors: David Black
Original assignee: Dana Automotive Ltd
Current assignee: Dana Automotive Ltd
Priority date: 2002-12-19
Filing date: 2002-12-19
Publication date: 2004-06-23
Anticipated expiration: 2022-12-19
Also published as: GB2396340B; GB0229536D0

Abstract

A method of operating a suspension 10 for a vehicle wheel, the suspension including a piston 12 and fluid filled cylinder 13 device 14 secured to the vehicle wheel and body such that up and down movement of the wheel in response to changing ground conditions causes relative movement between the piston 12 and the cylinder 13, the suspension 10 further including a fluid system having an accumulator 16 for pressurising the fluid in the system, a pump 21 for pumping fluid into the fluid system, a reservoir 20 for system fluid, and there being a first valve 26 between the cylinder 13 at a first side of the piston 12 and the accumulator 16, a second valve 28 in a fluid flow path between the other side of the piston 12 and the reservoir 20, and there being a system controller which controls the operation of the first and second valves 26, 28 and the pump 21 dynamically to adjust or permit adjustment of the piston 12 position in the cylinder 13 in response to or in anticipation of changing ground conditions and wherein the method includes closing the first valve 26 and opening the second valve 28 so that in response to piston 12 movement in the cylinder 13 in a first direction, fluid is forced back to the reservoir, there being an electrical generator 21 through which the forced back fluid passes to the reservoir 20 to produce electrical energy the method including recovering the electrical energy produced and using it in the vehicle.

Description

PATENTS ACT 1977

A10760GB/DJL

Title: Method of Operating a Suspension for a Vehicle Wheel Description of Invention

5 This invention relates to a method of operating a suspension for a vehicle wheel.

More particularly the invention relates to a method of operating a suspension which includes a piston and fluid filled cylinder device with one of the piston and cylinder being secured relative to the vehicle wheel and the other 10 of the piston and cylinder being secured relative a body (or chassis) of the vehicle, such that up and down movement of the wheel in response to changing ground conditions as the vehicle travels over the ground, causes relative movement between the piston and the cylinder.

Suspensions of this general kind are known, for example from DE-A 15 3902743 and JP-A-62289418 which include a fluid system having one, or a pair of accumulators for pressurising the fluid in the system, a reservoir for system fluid, and an electrically operated pump for pumping fluid into the system from the reservoir.

According to a first aspect of the present invention we provide a method 20 of operating a suspension for a vehicle wheel, the suspension including a piston and fluid filled cylinder device with one of the piston and cylinder being secured relative to the vehicle wheel and the other of the piston and cylinder being secured relative a body of the vehicle, such that up and down movement of the wheel in response to changing ground conditions as the vehicle travels 25 over the ground, causes relative movement between the piston and the cylinder, the suspension further including a fluid system having an accumulator for pressurising the fluid in the system, a pump for pumping fluid into the fluid system, a reservoir for system fluid, and there being a first valve between the cylinder at a first side of the piston and the accumulator, a second valve in a

fluid flow path between the other side of the piston and the reservoir, and there being a system controller which controls the operation of the first and second valves and the pump dynamically to adjust or permit adjustment of the piston position in the cylinder in response to or in anticipation of changing ground 5 conditions and wherein the method includes closing the first valve and opening the second valve so that in response to piston movement in the cylinder in a first direction, fluid is forced back to the reservoir, there being an electrical generator through which the forced back fluid passes to the reservoir to produce electrical energy, the method including recovering the electrical energy 10 produced and using it in the vehicle.

Thus utilising the present invention, particularly but not exclusively in response to movement of the vehicle wheel as a result of the wheel encountering an upwardly extending projection in the road (a "bump"), energy may be recovered through the generator, for immediate or later use, in the 15 vehicle. For example, the energy thus recovered may be stored in a battery via a battery charging circuit.

Most conveniently the pump is an electrically operated pump for pumping fluid into the system from the reservoir, the pump when required, being operable as the generator.

20 Of course, when it is desired to operate the pump to pump fluid into the system from the reservoir, the pump will consume energy, including possibly any energy recovered previously when the pump was acting as the electrical generator. The first and second valves and the electrically operated pump may be 25 controlled according to an algorithm in a suspension controller, for example in response to a first input from a piston position sensor which senses the position of the piston relative to the cylinder, and a second input from a pressure sensor which senses the pressure in the fluid system between the first valve and the accumulator. Thus for example, the suspension controller may determine

whether, after the piston has been moved in the first direction in response to the bump, the accumulator is sufficiently pressurised to return the piston to a datum position when the first valve is opened, or whether the pump needs to be operated to charge the fluid system. The system controller may close the first 5 valve when the piston has been returned to the datum position.

The fluid system may include a third valve in a passage between the first and a second opposite side of the piston, which third valve may also be controllable by the suspension controller, to allow a selected proportion of fluid to pass from the first or the second side of the piston to the second or first side 10 respectively, when the piston moves in response to changing ground conditions as the vehicle travels over the ground.

Furthermore, the fluid system may include a fourth valve which may be controlled by the suspension controller to allow a proportion of or prevent fluid flow from the first side of the piston to the generator and/or pump, so that with 15 the first valve closed and the third valve at least partly open, piston movement in the cylinder in either the first or opposite second direction is damped by fluid flowing from one side of the piston to the other. Of course if desired, the system may be operated with the first valve open and the second and fourth valves closed, so that the suspension operates as a conventional sprung 20 suspension.

Thus the method may include providing a biasing device for at least the first valve, to bias the first valve to its open condition, and biasing devices may be provided to bias each of the second and fourth valves to their closed conditions, so that in the event of any system failure for example, the 25 suspension may provide some damping for the wheel.

However, by operating the first, second, third, and fourth valves and the pump according to a control algorithm in response to the first and second inputs, an intelligent suspension may be provided.

The fluid system may include a fifth valve between the first valve and the first side of the cylinder which may be opened and closed by the suspension controller to control the flow of fluid between the generator and/or pump and the first side of the piston, and preferably the fifth valve is biased to an open 5 condition in the event of a system failure.

The suspension controller may receive additional inputs which affect the method of operation of the suspension. For example, the datum position of the piston in the cylinder may be adjusted by a manual input, whereby the ride height of the wheel may be selected by an operator. Thus for different road/off 10 road conditions, an appropriate ride height may be selected by charging or discharging the accumulator and fluid system, whilst opening and closing the respective fluid control valves.

According to a second aspect of the invention we provide a suspension for a vehicle wheel, the suspension including a piston and fluid filled cylinder 1 S device with one of the piston and cylinder being secured relative to the vehicle wheel and the other of the piston and cylinder being secured relative a body of the vehicle, such that up and down movement of the wheel in response to changing ground conditions as the vehicle travels over the ground, causes relative movement between the piston and the cylinder, the suspension further 20 including a fluid system having an accumulator for pressurising the fluid in the system, a pump for pumping fluid into the fluid system, a reservoir for system fluid, and there being a first valve between the cylinder at a first side of the piston and the accumulator, a second valve in a fluid flow path between the other side of the piston and the reservoir, and there being a system controller 25 which controls the operation of the first and second valves and the pump dynamically to adjust or permit adjustment of the piston position in the cylinder in response to or in anticipation of changing ground conditions, and the suspension including an electrical generator through which fluid may be forced to pass to the reservoir to produce electrical energy when the first valve is

closed and the second valve is opened and piston movement occurs in the cylinder in a first direction.

According to a third aspect of the invention we provide a vehicle having a suspension according to the second aspect of the invention.

5 Embodiments of the invention will now be described with reference to the accompanying drawing which is a schematic drawing of a suspension which may be operated by the method of the invention.

Referring to the drawing a suspension 10 is shown which is for a vehicle wheel (not shown) to which a piston 12 of a piston and cylinder device 14 is 10 secured, and with a cylinder 13 of the device 14 being secured relative to a vehicle body or chassis (not shown).

The piston and cylinder device 14 is fluid filled, and up and down movement of the vehicle wheel in response to changing road conditions as the vehicle moves over the ground, results in piston 12 movement in the cylinder 15 13.

The device 14 is provided in a fluid system which includes a hydraulic accumulator 16 which in this example includes a mechanical spring 17 acting on a piston 18 but may instead include a diaphragm and trapped volume of gas, in each case the accumulator 16 being operative to pressurise the fluid in the 20 system. The fluid system also includes a reservoir 20 for hydraulic fluid, and a fluid pump 21, as well as several fluid control valves which the operation and effect of which will be described below.

The suspension 10 further includes a suspension controller (not shown) which may be a dedicated controller, or integrated with another vehicle system, 25 such as an engine management system. The controller operates the suspension 10 according to an algorithm in response to various inputs, including a piston position sensor 22 which senses the position of the piston 12 relative to the cylinder 13, and a pressure sensor 24 which is provided adjacent to an outlet

from the accumulator 16 to sense the fluid pressure exerted by the accumulator 16. Other inputs may be provided to the suspension controller, such as manual inputs to change operating parameters of the suspension 10. For 5 example, a manual input may be provided by a vehicle operator to change the ride height of the wheel relative to the vehicle body or chassis, or the stiffness of the suspension may be changed to give alternative driving conditions, for example to suit different on and offroad conditions.

If desired, an input may be provided from a sensor which senses future 10 road conditions, such as for example a laser or other optical, or acoustic or radar type sensor, which senses bumps and troughs in the road surface ahead of these being encountered by the wheel, so as to enable the suspension controller to prepare the suspension for such an event.

The fluid system includes a first electrically operated fluid valve 26, 15 which when closed by the suspension controller, prevents the flow of fluid to or from the accumulator 16 so that the accumulator is isolated. The pressure sensor 24 is provided between the accumulator 16 and the first valve 26 so as to sense available pressure to the fluid system if and when the first valve 26 is opened. 20 A second electrically operated fluid valve 28 is provided in a line between the reservoir 20 and the piston and cylinder device 14. When the second valve 28 is opened by the suspension controller, fluid ejected from below the piston 12 as seen in the drawing, which is referred to below as a second side of the piston 12, as the piston 12 moves in a downward, second, 25 direction, for example in response to the wheel encountering a trough in the road surface, is returnable to the reservoir 20.

The fluid system includes a third electrically operated fluid valve 30 which is provided in a by-pass line 31 which communicates with the cylinder 13 at either side of the piston 12. When the third valve 30 is opened by the

suspension controller, at least a proportion of fluid ejected from the cylinder 13 from either side of the piston 12 may flow to the opposite side of the piston 12, as the piston 12 moves in the cylinder 13.

A fourth electrically operated fluid valve 32 is provided adjacent to the 5 electrically operated pump 21, which may be closed to prevent the flow of fluid to and from the pump 21, and a fifth electrically operated fluid valve 34 is provided adjacent to the piston and cylinder device 14.

The various fluid valves 26, 28, 30, 32, 34 are each controllable to achieve different operational modes.

10 In accordance with the invention, the electrically operated pump 21 when not pumping fluid into the fluid system, may be utilised to recover energy input into the system as a result of the displacement of the piston 12 in response to bumps in the road surface.

In this mode of operation, the first valve 26 is closed whilst second 15 valve 28 is opened. The third valve 30 may be completely closed or in a partially open condition, whilst the fourth valve 32 is opened and the fifth valve 34 would be fully or partially open.

Thus as the piston 12 moves upwardly in the cylinder 13 in a first direction, fluid ejected from the first upper side of the piston 12 passes via fifth 20 and fourth valves 34, 32 to the pump 21, and passes back through the pump 21 to cause an impeller of the pump 21 to rotate, and hence the fluid passes to the reservoir 20.

The pump 21 is-provided in an electrical charging circuit so that during such rotation of the impeller caused by the fluid being forced through the pump 25 21, electricity is generated and may be stored by being used for battery charging, and hence for later use in the vehicle. Otherwise the electricity produced may be used as it is produced, in the vehicle. Thus the pump 21 is an electric motor, the coils of which may be energised to cause the impeller to pump fluid into the system under pressure, or the windings of the motor may

have electrical current generated therein as a result of the impeller being rotated as fluid is forced back through the pump 21 as a result of piston 12 movement as described.

It will be appreciated that in this latter mode of operation, fluid may pass 5 from the reservoir 20 via the second open valve 28, to fill the space under the piston 12 with fluid so that the fluid system remains filled.

If the third valve 30 is partially open during this mode of operation, some of the fluid ejected from the one side of the piston 12 will be fed to the second side of the piston so that less fluid will be passed back through the 10 pump 21, and less make-up fluid will be required to pass from the reservoir 20 to the underside of the piston 12.

However pressurised fluid will be lost from the fluid system via the pump 21 back to the reservoir 20 and in order to make up the pressurised fluid and return the piston 12 to a datum position in the cylinder 13, the first valve 26 15 is opened by the suspension controller so that pressurised fluid from the accumulator 16 may pass to the first upper side of the piston 12 via the fifth valve 34. When the first valve 26 is opened, the fourth valve 32 is closed to isolate the pump 21, but if the pressure sensor 24 determines that the pressure in the accumulator 16 is lower than a threshold, the fourth valve 32 is opened 20 and the pump 21 is operated, so that fluid is pumped into the fluid system to restore the pressure. When the piston 12 is determined to be at a datum position in the cylinder 13, the fifth valve 34 may be closed so that the fluid is only pumped into the accumulator 16 to charge the system with pressurised fluid.

In the event of some system failure, or in response to a manual input to 25 the suspension controller, the system may be operated in a non-active mode, with the first and fifth valves 26, 34 open, and the second and fourth valves 28, 32 closed, and the third valve 30 completely closed or partially open, so that fluid is contained in the fluid system as the piston 12 responds to changing road

conditions by moving in the cylinder 13, with such movement being damped by the effect of the accumulator 16.

Various dynamically active modes of operation are possible by opening and closing the valves 26, 28, 30, 32, 34 and operating the pump 21 as 5 appropriate to suit different road conditions encountered and in response to different manual and other inputs to the suspension controller. Also the stiffness of the suspension may be altered, for example by opening the various first, second, third and fifth valves 26, 28, 30, 34 by different proportions to allow varying flows of fluid in the various operating modes, to provide varying 10 damping to piston 12 movement in the cylinder 13.

Various modifications may be made without departing from the scope of the invention. For example, in the embodiment described and shown in the drawings, the pump 21 acts as the electrical generator when fluid is forced back through the pump 21 in response to upward piston movement. In another 15 example a separate generator may be provided, with their being appropriate one way valves or the like to isolate the pump 21 and generator in different modes of system operation.

The fourth valve 32 may not be required where the pump 21 or pump 21 generator combination is effective to prevent the flow of fluid to and from the 20 reservoir 20 when not desired.

The third valve 30 may not always be required.

It will be appreciated that a suspension for a single wheel has been described with reference to the drawings, but the piston 12 could be secured to a pair of wheels for example on an axle and thus may be responsive to complex 25 wheel/axle movements. The fourth valve 32, the pump 21 and the reservoir 20 at least may be components of a suspension 10 for a plurality of wheels each having their own associated accumulators 16 and piston and cylinder devices 14. The routing for hydraulic fluid shown in the drawing is purely diagrammatic and would be specific for particular vehicles or vehicle types.

The algorithm for the suspension controller would be vehicle specific and may be sufficiently intelligent to control the suspension taking into consideration past suspension performance.

The features disclosed in the foregoing description, or the following

5 claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A method of operating a suspension for a vehicle wheel, the suspension including a piston and fluid filled cylinder device with one of the piston and 5 cylinder being secured relative to the vehicle wheel and the other of the piston and cylinder being secured relative a body of the vehicle, such that up and down movement of the wheel in response to changing ground conditions as the vehicle travels over the ground, causes relative movement between the piston and the cylinder, the suspension further including a fluid system having an 10 accumulator for pressurising the fluid in the system, a pump for pumping fluid into the fluid system, a reservoir for system fluid, and there being a first valve between the cylinder at a first side of the piston and the accumulator, a second valve in a fluid flow path between the other side of the piston and the reservoir, and there being a system controller which controls the operation of the first and 15 second valves and the pump dynamically to adjust or permit adjustment of the piston position in the cylinder in response to or in anticipation of changing ground conditions and wherein the method includes closing the first valve and opening the second valve so that in response to piston movement in the cylinder in a first direction, fluid is forced back to the reservoir, there being an electrical 20 generator through which the forced back fluid passes to the reservoir to produce electrical energy, the method including recovering the electrical energy produced and using it in the vehicle.

2. A method according to claim 1 wherein the energy recovered is stored in 25 a battery of the vehicle via a battery charging circuit.

3. A method according to claim 1 or claim 2 wherein the pump is an electrically operated pump for pumping fluid into the system from the reservoir, the pump when required, being operable as the generator.

4. A method according to any one of claims 1 to 3 wherein the first and second valves and the electrically operated pump are controlled according to an algorithm in a suspension controller.

5. A method according to claim 4 wherein the suspension controller responds to a first input from a piston position sensor which senses the position of the piston relative to the cylinder, and a second input from a pressure sensor which senses the pressure in the fluid system between the first valve and the 1 0 accumulator.

6. A method according to claims wherein the suspension controller may determine whether, after the piston has been moved in the first direction in response to the bump, the accumulator is sufficiently pressurised to return the 15 piston to a datum position when the first valve is opened, or whether the pump needs to be operated to charge the fluid system, and the system controller closing the first valve when the piston has been returned to the datum position.

7. A method according to any one of claims 1 to 6 wherein the fluid system 20 includes a third valve in a passage between the first and a second opposite side of the piston, the third valve being controllable by the suspension controller, to allow a selected proportion of fluid to pass from the first or the second side of the piston to the second or first side respectively, when the piston moves in response to changing ground conditions as the vehicle Ravels over the ground.

8. A method according to claim 7 wherein the fluid system includes a fourth valve which is controllable by the suspension controller to allow a proportion of or prevent fluid flow from the first side of the piston to the generator and/or pump, so that with the first valve closed and the third valve at

least partly open, piston movement in the cylinder in either the first or opposite second direction is damped by fluid flowing from one side of the piston to the other. 5

9. A method according to claim 7 or claim 8 which includes operating the system with the first valve open and the second and fourth valves closed, so that the suspension operates as a conventional sprung suspension.

10. A method according to claim 9 wherein the method includes providing a 10 biasing device for at least the first valve, to bias the first valve to its open condition, and each of the second and fourth valves to their closed conditions.

11. A system according to any one of claims 8 to 11 where appendant to claim 8 wherein the fluid system includes a fifth valve between the first valve 15 and the first side of the cylinder which is opened and closed by the suspension controller to control the flow of fluid between the generator and/or pump and the first side of the piston, the fifth valve being biased to an open condition.

12. A method according to any one of the preceding claims which includes 20 manually providing an input to the suspension controller whereby a datum position of the piston in the cylinder is adjustable to adjust the ride height of the wheel.

13. A method according to claim 12 wherein for different road/off-road 25 conditions, an appropriate ride height is selected by charging or discharging the accumulator and fluid system, whilst opening and closing the respective fluid control valves.

14. A method of operating a suspension substantially as hereinbefore described with reference to the accompanying drawing.

15. A suspension for a vehicle wheel, the suspension including a piston and 5 fluid filled cylinder device with one of the piston and cylinder being secured relative to the vehicle wheel and the other of the piston and cylinder being secured relative a body of the vehicle, such that up and down movement of the wheel in response to changing ground conditions as the vehicle travels over the ground, causes relative movement between the piston and the cylinder, the 10 suspension further including a fluid system having an accumulator for pressurising the fluid in the system, a pump for pumping fluid into the fluid system, a reservoir for system fluid, and there being a first valve between the cylinder at a first side of the piston and the accumulator, a second valve in a fluid flow path between the other side of the piston and the reservoir, and there 15 being a system controller which controls the operation of the first and second valves and the pump dynamically to adjust or permit adjustment of the piston position in the cylinder in response to or in anticipation of changing ground conditions, and the suspension including an electrical generator through which fluid may be forced to pass to the reservoir to produce electrical energy when 20 the first valve is closed and the second valve is opened and piston movement occurs in the cylinder in a first direction.

16. A suspension for a vehicle substantially as hereinbefore described with reference to and/or as shown in the accompanying drawing.

17. A vehicle including a suspension according to claim 15 or claim 16.

18. Any novel feature or novel combination of features described herein and/or in the accompanying drawings.