GB2454013A

GB2454013A - A road vehicle suspension system

Info

Publication number: GB2454013A
Application number: GB0721112A
Authority: GB
Inventors: Steven Kenchington
Original assignee: Lotus Cars Ltd
Current assignee: Lotus Cars Ltd
Priority date: 2007-10-26
Filing date: 2007-10-26
Publication date: 2009-04-29
Anticipated expiration: 2027-10-26
Also published as: GB0721112D0; GB2454013B; WO2009053712A1

Abstract

A road vehicle suspension system comprising a pair of wheels 40,41 spaced transversely apart across the vehicle; for each wheel a swing arm pivotally connecting the wheel to the vehicle; and an anti-roll bar 50 extending across the vehicle to interconnect the pair of wheels 40,41. The anti-roll bar has a first part 51 connected to a first 40 of the pair of wheels and a second part 52 connected to a second 41 of the pair of wheels. An electrically-controlled actuator 12 interconnects the first 51 and second 52 parts of the anti-roll bar 50 and is operable to control how much torque is transmitted from one part of the anti-roll bar to the other part of the anti-roll bar. An electronic controller controls operation of the actuator.

Description

A Land Vehicle Suspension System The present invention relates to a land vehicle suspension system.

It is well known to use in conventional suspension systems devices called anti-roll bars' which act between a pair of wheels located on opposite sides of the vehicle and act to lessen rolling of the vehicle as it corners, therefore improving its driving characteristics. However, such devices often have the undesired effect of adding stiffness to the suspension when the vehicle is travelling in a straight line, thereby degrading the ride' characteristics of the vehicle and exposing the driver to a greater degree of ride harshness as the vehicle passes over a rough surface in a straight line.

The present invention provides in a first aspect a road vehicle suspension system comprising: a pair of wheels spaced transversely apart across the vehicle; for each wheel a swing arm pivotally connecting the wheel to the vehicle; and an anti-roll bar extending across the vehicle to interconnect the pair of wheels, wherein: the anti-roll bar has a first part connected to a first of the pair of wheels and a second part connected to a second of the pair of wheels; an electrically-controlled actuator interconnects the first and second parts of the anti-roll bar and is operable to control how much torque is transmitted from one part of the anti-roll bar to the other part of the anti-roll bar; and an electronic controller controls operation of the actuator.

The present invention provides in a second aspect a road vehicle suspension system comprising: a pair of front wheels spaced transversely apart across the vehicle; a pair of rear wheels spaced transversely apart across the vehicle; for each wheel a swing arm pivotally connecting the wheel to the vehicle; a front anti-roll bar extending across the vehicle to interconnect the pair of front wheels; a rear anti-roll bar extending across the vehicle to interconnect the pair of rear wheels; wherein: the front anti-roll bar has a first part connected to a first of the pair of front wheels and a second part connected to a second of the pair of front wheels; the rear anti-roll bar has a first part connected to a first of the pair of rear wheels and a second part connected to a second of the pair of rear wheels; an electrically controlled front actuator connects the first and second parts of the front anti-roll bar and controls how much torque is transmitted from one part of the front anti-roll bar to the other part of the front anti-roll bar; an electrically controlled rear actuator interconnects the first and second parts of the rear anti-roll bar and controls how much torque is transmitted from one part of the rear anti-roll bar to the other part of the rear anti-roll bar; and an electronic controller controls operation of the front and rear actuators.

The present invention enables a vehicle to benefit from the action of an anti-roll bar during cornering without suffering from undesired increased stiffness of the suspension while the vehicle is travelling in a straight line.

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a hydraulic schematic diagram of a land vehicle suspension system according to the present invention; Figure 2 is a schematic drawing of an anti-roll bar arrangement for a single pair of wheels of a vehicle in the land vehicle suspension system of figure 1; Figure 3 is an illustration of an anti-roll bar of the arrangement of figure 2; Figure 4 is an illustration of a rotary actuator of the arrangement of figure 3; and Figure 5 is a hydraulic circuit diagram of the land vehicle suspension system of figure 1.

Turning first to figure 1 there can be seen a hydraulic schematic of a land vehicle suspension system according to the present invention. The system is for a vehicle having four wheels: a pair of front wheels (not shown in figure 1) located spaced laterally apart on opposite sides of the vehicle (assuming that the longitudinal direction of the vehicle runs fore and aft and the lateral direction perpendicular to this, from side to side); and a pair of rear wheels (not shown in figure 1) again located spaced laterally apart on opposite sides of the vehicle.

The system has a front hydraulic rotary actuator 11 associated with the front pair of wheels and a rear hydraulic rotary actuator 12 associated with the rear pair of wheels. Figure 4 shows one of the rotary actuators 11,12 -both will be identical to each other. Each is of a compact design and allows a significant degree of wheel travel. Each has two chambers and operates to apply a torque in a first sense (e.g. clockwise) if one chamber is connected to receive fluid pressure and the other to a fluid return, and operates to apply a torque in an opposite sense (e.g. anti-clockwise) if chamber connection are reversed. Rotary actuators are commercially available products.

Figure 2 shows an anti-roll bar 50 for a pair of rear wheels 40,41 (the anti-roll bar for the front wheels will be identical). The rear rotary actuator 12 provides the connection between two parts 51,52 of the anti-roll bar 50.

It controls the torque transmitted from the wheel 40 on one side on the vehicle to the wheel 41 on the other side of the vehicle. Figure 3 is a simplified view of this arrangement showing the two parts 51,52 of the anti-roll bar 50 are connected via the rotary actuator 12. The figure also shows conventional spring-and-damper assemblies 80 and 81 respectively for the wheels 40, 41. The roll bar arrangement acts in parallel with the spring-and-damper assemblies to provide suspension for the wheels 40, 41.

The system has a pump 13 common to both actuators 11,12, which is mechanically driven by a belt 14 relaying power from an internal combustion engine 15. The pump 13 draws hydraulic fluid from a sump 16, which also provides the fluid return for the actuators 11,12. An electrically controlled throttle valve 17 is used both to disconnect the pump 13 from the sump 16 and also to control the rate of flow of fluid to the pump 13 when the pump 13 is connected to sump 16. A pressure relief valve 18 is included in the hydraulic circuit for safety and at a preset pressure opens to allow fluid to flow directly from the pump 13 to the sump 16 to prevent excessive build up of pressure in the hydraulic circuit. The valve 18 is a spring-loaded valve which operates automatically once a threshold pressure is reached. An electrically controlled dump valve 19 is also provided which can be opened to allow flow of fluid directly from pump 13 to sump 16 when the rotary actuators 11 and 12 are isolated (see later) . Two expansion chambers 20, 21 are provided to allow for storage of hydraulic fluid under pressure for release at times of high demand for fluid flow.

A front servo-valve 22 is provided to control operation of the front actuator 11. It is a three position valve, having: a first position in which fluid supplied to the rotary actuator 11 causes the actuator 11 to apply a torque in a first (e.g. clockwise) rotational sense; a second position in which fluid supplied to the rotary actuator 11 causes the actuator 11 to apply a torque in a second (e.g. anti-clockwise) rotational sense opposite to the first rotational sense; and a third position in which the actuator 11 is isolated by the valve 22 from the pump 13 and sump 16.

A rear servo-valve 23 is provided to control operation of the rear actuator 12. It is a three position valve, having: a first position in which fluid supplied to the rotary actuator 12 causes the actuator 12 to apply a torque in a first (e.g. clockwise) rotational sense; a second position in which fluid supplied to the rotary actuator 12 causes the actuator 12 to apply a torque in a second (e.g. anti-clockwise) rotational sense opposite to the first rotational sense; and a third position in which the actuator 12 is isolated by the valve 23 from the pump 13 and sump 16.

Both of the valves 22 and 23 are metering valves which can control the rate of flow of fluid through them.

Connected between the valve 22 and the front actuator 11 is a soft system' 24. This comprises an electrically-controlled valve 26 which either connects the two chambers of the actuator 11 together or disconnects them from each other. This can be seen in figure 5, where it can also be seen that the valve 22 is connected in parallel with the valve 26 to the actuator 11 via the soft system 24. The valve 26 is a proportional valve which not only connects together the two chambers of the actuator 11 but can also control a rate of flow of fluid from one chamber to the other when they are connected.

Connected between the valve 23 and the front actuator 12 is a soft system' 25. This comprises an electrically-controlled valve 27 which either connects the two chambers of the actuator 12 together or disconnects them from each other. This can be seen in figure 5, where it can also be seen that the valve 23 is connected in parallel with the valve 27 to the actuator 12 via the soft system 25. The valve 27 is a proportional valve which not only connects together the two chambers of the actuator 12, but can also control a rate of flow of fluid from one chamber to the other when they are connected.

The valves 22 and 23 and the valves 26,27 are all controlled by a common electronic controller (not shown) The electronic controller is connected to sensors around the vehicle (e.g. a lateral accelerometer, yaw rate gyrometer, steer angle sensor, wheel hub accelerometers and force and/or position sensors associated with the wheels) which together enable the controller to ascertain whether the vehicle is travelling in a straight line or whether the vehicle is cornering.

When the vehicle is travelling in straight line (e.g. when the controller determines that lateral acceleration is below a chosen threshold value) the controller will control the valves 22 and 23 to isolate the actuators 11,12 from the pump 13 and sump 16. At the same time the valves 26,27 are controlled to connect together the two chambers of each rotary actuator. The rate of flow of fluid between the two chambers of each actuator is also controlled. The rotary actuators are thus controlled to offer a variable degree of damping to relative rotation between the two halves of each anti-roll bar. Any damping provided by the actuators when operating with their chambers interconnected will be additional to and in parallel with the damping provided by the spring-and-damper assemblies (e.g.80,81). The actuators can be controlled, if desired, to offer minimal damping when the vehicle is travelling in a straight line in which case little or no torque will be transmitted through each anti-roll bar and each wheel will move independently controlled by its own spring and damper assembly.

When the vehicle is cornering then the electronic controller will control the valves 25 and 26 so that they disconnect the two chambers of each actuator 11,12. The valves 22 and 23 will then be controlled to connect one chamber of each actuator to fluid pressure and the other to fluid return so that the actuators apply torques between the halves of the anti-roll bars which resist rolling of the vehicle while cornering. The sense of torque applied (clockwise or anticlockwise) will depend on whether the vehicle is cornering through a left hand or a right hand corner. The metering capability of the valves 22,23 will be used by the electronic controller to control the amount of rotation and/or torque transmitted from one half of each ant-roll bar to the other and thereby control the rolling of the vehicle through corners. The controller will use the signals it receives form the vehicle's sensors (e.g. a lateral accelerometer, yaw rate gyrometer, steer angle sensor, wheel hub accelerometers and force and/or position sensors associated with the wheels) to determine the right level of torque to be applied. The pressure in the control line will also be monitored and controlled because the torque applied will vary with line pressure available.

In a failsafe mode the rotary actuators will be locked so that each anti-roll effectively functions as a conventional anti-roll bar. It may be desirable to allow some leakage through each control valve to provide the overall system with some compliance.

As shown above, the valves 26 and 27 are pilot-operated valves, in other words they have spools moved by the application of hydraulic pressure, the application of hydraulic pressure being controlled by a pair of valves 60,61 -one for each valve 26,27. The valves 60,61 are electrically controlled by the electronic controller.

However, the valves 26,27 could themselves be directly electrically controlled by the electronic controller and the need for the valves 60,61 avoided.

The operation of the system is energy efficient since there is little power required to power the pump when the vehicle is travelling in a straight line and the valves 26,27 connect together the two chambers of the rotary actuators.

The electronic controller operates to effectively decouple the anti-roll bars when the vehicle is travelling in a straight line to ensure that the vehicle has good ride characteristics in such circumstances; however, if desired the actuator can provide some controlled damping of wheel movement. The electronic controlling then couples in the anti-roll bars during cornering and controls the functioning of the roll bars to provide the vehicle with good cornering characteristics.

Whilst above the actuators used are rotary actuators, and this is preferred for reasons of packaging, it would be possible to use linear actuators each connecting the two halves of a roll bar through suitable linkages.

Claims

-10 - CLAI MS

1. A road vehicle suspension system comprising: a pair of wheels spaced transversely apart across the vehicle; for each wheel a swing arm pivotally connecting the wheel to the vehicle; and an anti-roll bar extending across the vehicle to interconnect the pair of wheels, wherein: the anti-roll bar has a first part connected to a first of the pair of wheels and a second part connected to a second of the pair of wheels; an electrically-controlled actuator interconnects the first and second parts of the anti-roll bar and is operable to control how much torque is transmitted from one part of the anti-roll bar to the other part of the anti-roll bar; and an electronic controller controls operation of the actuator.

2. A road vehicle suspension system comprising: a pair of front wheels spaced transversely apart across the vehicle; a pair of rear wheels spaced transversely apart across the vehicle; for each wheel a swing arm pivotally connecting the wheel to the vehicle; a front anti-roll bar extending across the vehicle to interconnect the pair of front wheels; a rear anti-roll bar extending across the vehicle to interconnect the pair of rear wheels; wherein: -11 -the front anti-roll bar has a first part connected to a first of the pair of front wheels and a second part connected to a second of the pair of front wheels; the rear anti-roll bar has a first part connected to a first of the pair of rear wheels and a second part connected to a second of the pair of rear wheels; an electrically controlled front actuator connects the first and second parts of the front anti-roll bar and controls how much torque is transmitted from one part of the front anti-roll bar to the other part of the front anti-roll bar; an electrically controlled rear actuator interconnects the first and second parts of the rear anti-roll bar and controls how much torque is transmitted from one part of the rear anti-roll bar to the other part of the rear anti-roll bar; and an electronic controller controls operation of the front and rear actuators.

3. A road vehicle suspension system as claimed in claim 1 or claim wherein: the actuator is a hydraulic actuator which has at least first and second chambers; the vehicle comprises a source of pressurised hydraulic fluid and a return for hydraulic fluid; for each/the actuator a first electrically-controlled servo-valve is provided to control connection of the actuator to the source and the return for each/the actuator a second electrically-controlled valve is provided which has a first operating condition in which the first and second actuator chambers are connected to each other by the second electrically-controlled valve -12 -and a second operating condition in which the first and second actuator chambers are disconnected from each other by the second electrically-controlled servo-valve, the second electrically-controlled valve metering flow of fluid between the chambers when they are connected together; and the electric controller controls operation of the first and second electrically-controlled valves.

4. A road vehicle as claimed in claim 3 wherein each/the first electrically-controlled valve can: connect the first chamber to the source of pressurised fluid and the second chamber to the return for pressurised fluid in order to apply torque in a first sensor between the parts of the respective anti-roll bar; connect the first chamber to the return for pressurised fluid and the second chamber to the source of pressurised fluid to apply torque in a second sense, opposite to the first sense, between the parts of the respective anti-roll bar; and seal off both the first and second chambers from the source of pressurised fluid and the return for pressurised fluid; and each/the second electrically-controlled valve connects together the chambers of the actuator associated therewith when the first electrically-controlled for the actuator seals off both chambers of the actuator from the source of pressurised fluid and the return for pressurised fluid.

5. A road vehicle as claimed in any one of the preceding claims which is provided with sensors which provide signals which indicate whether the road vehicle is travelling in a straight line or is cornering, which signals are processed -13 -by the electronic controller and when the electronic controller determines that the vehicle is cornering then the actuator(s) is/are connected to the source of pressurised fluid and apply torque between the first and second parts of the anti-roll bar(s) to provide an anti-roll force to the vehicle and when the controller determines that the vehicle is travelling in a straight line then the controller disconnects the actuator(s) from the source of pressurised fluid.

5. A road vehicle as claimed in claim in claim 3 or claim 4 which is provided with sensors which indicate whether the road vehicle is travelling in a straight line or is cornering, which signals are processed by the electronic controller and when the electronic controller determines that the vehicle is travelling in a straight line the controller controls the second control valve to connect the first and second chambers of the actuator(s) together and when the electronic controller determines that the vehicle is cornering then the controller controls the second control valve to disconnect the first and second chamber(s) of the actuator(s) from each other and controls the first control valve(s) to connect one of the chambers of the/each actuator to the source of pressurised fluid and the other chamber to the return for pressurised fluid in order that the anti-roll bar applies forces on the pair of wheels resisting rolling of the vehicle while cornering.

6 A road vehicle as claimed in claim 5 wherein each wheel is provided with a spring-and-damper assembly connecting the wheel to the remainder of the vehicle and when each/the second electrically-controlled valve connects together both -14 -chambers of an actuator associated therewith then the valve can be controlled by the electronic controller to meter flow of fluid between the interconnected chambers to provide damping of wheel motion in addition to damping provided by the spring-and-damper assembly.

7. A road vehicle suspension system as claimed in any one of claims 1 to 4 wherein each/the electrically-controlled actuator is a rotary actuator.

8. A road vehicle suspension system substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

830526, AWP, AWP