GB2354496A

GB2354496A - Arrangement for improved vehicle traction control

Info

Publication number: GB2354496A
Application number: GB9918242A
Authority: GB
Inventors: Andrew Julian Burrows
Original assignee: Bayerische Motoren Werke AG; MG Rover Group Ltd
Current assignee: Bayerische Motoren Werke AG; MG Rover Group Ltd
Priority date: 1999-08-04
Filing date: 1999-08-04
Publication date: 2001-03-28
Anticipated expiration: 2019-08-04
Also published as: GB9918242D0; GB2354496B

Abstract

The traction arrangement comprises one or more individually driven wheels (26) on opposed sides of the vehicle. A torque differential is supplied by motors (16) via propellor shafts (22) which are substantially perpendicular to the drive shafts (24), this results in a reaction against which the wheels (26) move relative to a suspended part of the vehicle. The arrangement incorporates a displacement prop (100) in which the relative movement is sustained after removal of the torque differential. Typically, the displacement prop (100) comprises a piston (103) and cylinder (102) arrangement in which the piston (103) is moved freely in order to accommodate the relative movement, whilst return is either prevented or is at a much reduced rate in order to sustain the relative movement and therefore weight distribution, for improved traction control.

Description

2354496 A Vehicle Traction Sustain Arrangem nt The present invention

relates to traction control sustain and more particularly to traction control sustain where vehicle orientation is maintained in order to vary weight distribution within a vehicle.

It is known by varying the weight distribution within a vehicle that it is possible to alter the traction of each individual vehicle wheel in order to achieve the best traction force in order to propel the vehicle. It will also be understood that previously traction to each wheel has been varied by altering the torque force applied to that wheel through a drive shaft or other means in order to provide individual operation of each wheel.

In UK patent application number 9819328.7, filed 5 September 1998, a vehicle is described in which traction control is provided through utilising torque reaction at each wheel in order to provide relative vertical motions between sprung parts of the vehicle and so alter the weight distribution of the vehicle. In such circumstances, it will be appreciated those wheels bearing a greater proportion of the vehicle weight will generally provide more traction. Thus, in off- road situations where individual vehicle wheels may be in contact with ground surfaces with different coefficients of friction i.e. rock as compared to mud or sand, it will be understood that additional combined traction can be achieved through providing greater torque to those wheels in contact with good driving surfaces.

Regrettably, utilising torque reaction forces in order to lift or lower a vehicle part and so re-distribute weight may only be temporarily achieved without relatively sophisticated consideration of the torque reaction force across a vehicle wheel axle. Thus, it will be understood that a rocking motion can be readily provided for a vehicle across a vehicle wheel pick-up pair but more long term lifting of a vehicle sprung part is more difficult to achieve without considerable expenditure of maintenance torque energy and as is indicated previously potentially complex control of the reaction torque differential across a wheel pair.

It is an object of the present invention to provide a traction control sustain arrangement which can maintain a particular traction control configuration for a 5 longer period of time.

In accordance with the present invention there is provided a traction control sustain arrangement for a vehicle, the arrangement comprising a suspended part between at least two opposed wheels on opposed sides thereof and a drive train comprising two propeller shafts coupled through a respective coupling to a respective drive shaft, wherein each drive shaft extends substantially transversely to the vehicle and has one end connected to one of said wheels, and torque input means for applying a driving torque to each of said propeller shafts, wherein the respective couplings between the drive shafts and propeller shafts are arranged such that driving torque applied to each propeller shaft will tend to apply a torque to a respective drive shaft with a substantial torque component presented in an axis substantially perpendicular to the respective drive shaft so as to tend to move the wheel relative to the suspended part of the vehicle in order to alter the weight distribution between the opposed wheels,. the arrangement further comprising control means arranged to control the driving torques applied to each of the propeller shafts so as to produce controlled variation in the weight distribution between the opposed wheels and so the load presented at each of the opposed wheels, and at least one of said opposed wheels having a displacement prop between that opposed wheel and the suspended part whereby the displacement prop substantially freely moves to accommodate relative movement between that opposed wheel and the suspended part whilst retaining that relative movement until released to maintain the variation in the weight distribution for sustained traction control.

Preferably, the relative movement between the opposed wheel and the suspended part is released by the displacement prop under the control of the control means.

The displacement prop may be a hydraulic or compressed gas or fluid piston 5 cylinder arrangement coupled between the opposed wheel and the suspended part. Alternatively, the displacement prop may comprise a ratchet arrangement or a cable and reel arrangement between the opposed wheel and the suspended part.

Where a hydraulic or compressed gas or fluid piston cylinder arrangement is used a one way valve may be provided in order to allow the substantially free movement to accommodate relative movement between the opposed wheel and the suspended part whilst a release valve is provided to allow the relative movement between the opposed wheel and the suspended part to be diminished or removed and so return that opposed wheel and the suspended part to their normal relative positions. The release valve may take the form of a simple one way valve of lower flow rate than the one way valve arranged to allow substantially free movement between the opposed wheel and the suspended part or comprise a controllable valve in which the rate of return movement between the suspended part and the opposed wheel can be controlled as required by the control means.

Where a mechanical displacement prop is used such as a ratchet or cable and reel it will be understood that the relative movement between the opposed wheel and the suspended part may be maintained by an actuator or brake engaging the ratchet or cable and reel arrangement. This actuator or brake may clamp the ratchet or cable in order to maintain the relative movement between the suspended part and the opposed wheel. The brake actuator may be operated by a magnetic coupling or lock engagement under control of a servo motor or similar device operated by the control means.

Preferred embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure I is a schematic representation of a vehicle according to one manner of achieving relative movement between an opposed wheel and suspended part; Figures 2 and 3 are schematic end views of part of the vehicle of Figure 1; Figure 4 is a schematic end view similar to Figure 3 in a vehicle according to a second manner of achieving relative movement between an opposed wheel and a suspended part; Figures 5a and 5b are schematic plan views of the embodiment of Figure 4; Figures 6 and 7 show one axle of the vehicle of Figure 4 under different conditions; Figure 8 is a cross section through the vehicle of Figure 4 during cornering; and, Figure 9 is a cross-section through a displacement prop arranged to sustain traction control.

Referring to Figure 1, a hybrid vehicle comprises an internal combustion engine 10, an electrical generator 12 driven by that engine 10 and a storage battery 14 for storing electrical energy produced by the generator 12. The hybrid vehicle also includes four electric motors 16a, 16b, 16c, 16d which are each independently driven using energy from the battery 14. The motors 16a, 16b, 16c 16d are under the control of a control unit 18 to produce respective driving torque for each of four wheels 20a, 20b, 20c, 20d.

Each of the motors 16 drives a respective propeller shaft 22a, 22b, 22c, 22d which extends longitudinally of the vehicle. Each propeller shaft 22a, 22b, 22c, 22d is connected to a drive shaft 24a, 24b, 24c, 24d which extends, in the embodiment depicted, at right angles to that propeller shaft 22a, 22b, 22c, 22d and transversely of the vehicle. Each drive shaft 24a, 24b, 24c, 24d drives a respective one of the two rear wheels 26a, 26b and two front wheels 26c, 26d. The propeller shafts 22 are coupled to the drive shafts 24 by means of bevel gear box couplings 28 which are arranged to rotate with the drive shafts 24 relative to the sprung or suspended parts of the vehicle during vertical wheel travel.

The bevel gear box couplings 28 are each arranged to provide a driving torque in a respective propeller shaft 22. Thus, as described in relation to only one coupling 28 for clarity, when the driving torque is in the direction which will drive the wheel 26 in a forward direction then the shaft 22 applies a torque to the drive shaft 24 through a bevel gear box coupling 28 about the longitudinal axis of the propeller shaft 22. In such circumstances, there is a reaction force to the driving torque in a direction which tends to lower the outboard end of the drive shaft 24.

Thus, the wheel 26 is urged downwards relative to the sprung or suspended parts of the vehicle whilst that driving torque persists.

As can be seen in Figure 2, the downward reaction force F on the wheel 26 is equal to the torque T transmitted into the drive shaft 24 divided by the lateral distance d between the bevel gear box coupling 28 and the contact patch of the wheel 26.

Referring to Figure 3, the illustrated embodiment has an independent suspension system which means that the respective drive torque to each of the wheels 26 can be used to control each respective contact force F at each of the wheels 26 independently of the wheels 26, subject to obvious physical and dimensional constraints.

The contact force F cannot be increased to or at all of the wheels 26 for long periods or at the same time. The contact force F to each wheel 26 can be increased briefly, to provide an upward acceleration or movement of the vehicle body relative to the ground i.e. wheel contact patch. However, this upward movement will then decrease as the limit of vertical travel is reached.

The distribution of the total drive torque T can be varied to alter the vehicle weight distribution presented as load between the four wheels. Thus, an altered weight distribution can be sustained over longer periods in the steady state as the total contact force F can be kept constant. i.e. equal to the weight of the vehicle. In such circumstances, there are various ways in which the torque supply to the respective vehicle wheels can be controlled to improve the traction of the wheels. Typically, the controlled variations in torque for weight distribution are superimposed on top of the mean torque T to each wheel 26 which is controlled by the driver using the accelerator pedal in the usual manner for vehicle motion and acceleration.

In a first mode of operation, the control unit 18 alternates the torque supplied to all four wheels 26. As mentioned above, this will result in an oscillation of the contact force F for all of the wheels 26 about its mean value as the vehicle body moves up and down.

It is well known that, under some circumstances, if a vehicle is stuck in an area of soft ground where traction is not good, it is helpful to "bounce" the vehicle up and down to improve traction. In this invention, the same effect can be achieved by alternating the torque to all four wheels simultaneously at a frequency approximately equal to the natural frequency of the vehicle in bounce, which is generally of the order of I or 2 Hz. This not only produces the desired vertical bouncing of the vehicle, but also ensures that, when the vehicle is travelling forwards, the maximum torque is provided to the wheels at the time when the 5 contact force is greatest thereby maximising traction.

In another mode of operation the invention can be used to improve traction in a situation where the wheels of the vehicle are on surfaces of different coefficient of friction. It is well known to control the torque applied to the wheels of a vehicle so that greater torque is applied to the wheel or wheels which are on a surface with higher coefficient of friction. This can be done passively using a mechanical differential, or actively by measuring the coefficient of friction at each wheel.

In the vehicle of Figure I the control unit 18 is arranged to monitor the coefficients of friction at each of the wheels 26. The control unit 18 can modify the torque distribution between the wheels 26 so as to provide a higher torque to wheels on surfaces with a higher coefficient of friction. It is due to such modified torque distribution that that wheel or those wheels in contact with higher friction surface will tend to be moved downwards most and will therefore take a higher proportion of the total weight of the vehicle than other wheels. Thus, the maximum traction force available is higher than if the weight remained more evenly distributed between the wheels.

Alternatively, this traction effect can be achieved if the control means operates not by actually measuring the coefficient of friction at each of the wheels 26, but by limiting the difference in speeds between the vehicle wheels 26. Thus, the control unit 18 will increase the torque to slower moving wheels and decrease the torque to faster moving wheels. This is the electrical equivalent of a mechanical differential.

In a vehicle with beam axles the invention can still be made to work, although the ways in which it can be controlled and utilised are more limited. Referring to Figure 4, in a second embodiment of the invention a vehicle has the same drive train layout as shown in Figure 1. However, the suspension is different in that the rear wheels 40a, 40b are mounted on opposite ends of a rigid beam 42, and the drive shafts 44a, 44b driving them are rigidly mounted in the beam 42.

The beam 42 is free to move relative to the sprung or suspended parts of the vehicle to allow vertical wheel travel. If the torques Ti and T2 applied to the two rear wheels 40a, 40b are the same then the resultant torque on the beam 42 will be zero. However, if one of the torques Ti or T2 is greater than the other, a resultant net torque will be produced in the beam 42 which will tend to raise one of the wheels 40a, 40b and lower the other relative to the sprung or suspended part of the vehicle.

As with the fully independent type suspension illustrated in figures 1-3 this effect of torque induced movement can be utilised in various ways. Firstly, if the torque distribution is oscillated from side to side at both the front and rear axles simultaneously at frequencies of the order of the roll frequency of the vehicle, i.e.

typically of the order of 0.5 to 2Hz. This rocking motion will then be set up the vehicle so that the contact load force L on the two sides of the vehicle will oscillate in an out-of-phase manner. Provided the vehicle is in a forward gear the side with the greatest contact force L will be the side where the greatest driving torque is applied at any one time.

As an alternative the torques supplied to the two axles could be arranged to oscillate from side to side in an out of phase manner, as illustrated in Figure 5.

This will increase the contact force at first in one diagonally opposite pair of wheels 40a, 40d and then in the other pair of wheels 40b, 40c in turn. While the contact force of one such pair is increased that of the other such pair will be decreased, and vice versa. Therefore the overall resultant movement of the suspended or sprung part of the vehicle will be substantially zero. With this embodiment the use of torque distribution control when the wheels are on surfaces of unequal coefficient of friction can be used in the same way as the first embodiment.

Referring to Figure 6, if one of the wheels 40a is on a surface with a lower coefficient of friction jil than that coefficient A2 of the other three wheels then the torque supplied across an axle can be re-distributed so as to reduce the driving torque Ti to that one wheel 40a and increase the driving torque T2 to the other wheel on the same axle. This will transfer the weight of the vehicle away from the wheel 40a having the least traction and therefore increase the effective total traction from all of the wheels. In order to prevent body roll, the torque and distribution across the other axle could be controlled in the opposite direction by the same amount.

In other circumstances it is important to keep the traction torques at the wheels equal, rather than achieving the maximum total traction force. In such circumstances, for each axle, the torque to the wheel on the surface of lower coefficient of friction needs to be increased compared to that to the wheel on the surface of higher coefficient of friction, until the maximum traction force, i.e. force in the forward direction is equal on the two wheels. This would be particularly useful in a two-wheel drive application where the resulting change in load distribution at the other axle would not affect the total traction torque.

Referring to Figure 7, the drive train layout of the invention can also be utilised to overcome grounding in some circumstances. If one wheel 40b is lifted off the ground due to grounding of the vehicle body there will be no wheel 40b ground contact and so no available traction from that wheel 40b. In order to simultaneously increase the available traction and transfer weight off the grounded part of the vehicle, the driving torque Ti to the ground contacting wheel 40a can be increased above that torque T2 applied to the non-ground contacting wheel 40b. This torque differential will urge the ground contacting wheel 40a downwards with a force Fi and the non-ground contacting wheel 40b upwards with a force F2. This will tend to transfer weight from the grounded part of the vehicle into the ground-contacting wheel 40a, and therefore help with freeing the vehicle.

The downward force on the ground-contacting wheel 40a is related to the difference between the driving torques Ti and T2 of the two wheels 40a, 40b. Thus, it is possible to enhance this effect by applying a backward driving torque through the drive train to a braked or non-ground contacting wheel 40b and an increased forward driving torque to the ground contacting wheel 40a. This would preferably require braking of the non-ground contacting wheel 40b. Such braking could be achieved by co-ordinated control of the vehicle brakes which is known in conventional traction control systems.

It will also be understood from above that rather than only brake wheels 40 when there is ground clearance that deliberate selective braking of wheels whilst in motion could be used to amplify vehicle weight distributions by altering body movements. Thus, whilst the vehicle is in motion, individual wheels could be marginally braked against the torque applied in order to emphasis the torque differential across a wheel pair for relative body i.e. suspended part lift or drop. Clearly, heavy braking to stop, or near stop, would be unusual but transient short term braking of individual wheels will provide the weight re- distributions desired for traction control, at least transiently.

It will be understood that there is an inherent hysteresis with most vehicle suspension arrangements. Thus, although only transient, weight redistributions as a result of torque differentials may affect traction control for longer periods of time as the natural damping of the suspension arrangement oscillates about and 5 returns to its steady state position.

As indicated above deliberate selective and deliberate wheel braking may be used to'lift'a vehicle in order to amplify down force in a driven wheel. Similarly, a vehicle may be "bounced" in order to find which wheels have better traction and then the vehicle 'set' in terms of the relative torque distribution between the wheels and vehicle weight distribution through body lift etc. for best or desired traction control. In such circumstances, it will be understood that a vehicle suspension arrangement will be used that can vary in terms of hardness and damping in order to retain the vehicle 'set' created by torque distribution. In any event, it will be understood that, for example upon vehicle take-off from a standing start additional traction can be provided to those wheels best suited to such acceleration by retention of an appropriate vehicle body orientation produced by differential torque and sustained by the suspension arrangement or otherwise. The vehicle weight would then be re-aligned for more even distribution for normal driving.

It will be understood that each side of the vehicle could be lifted one after the other. Thus, one side would be braked preferably against a torque whilst the other is subject to an opposite torque to provide vehicle lift or lowering. This lift or lowering will be sustained and the roles reversed to lift or lower the other side.

A further use of the present invention is with regard to straight or substantially straight line vehicle motion. It will be understood that a vehicle driven in a straight may be subjected to significant jostle due to striking pot-holes and ruts, cross winds and road camber etc. In such circumstances, it win be understood that such jostle may be ameliorated by torque differential and weight distribution in accordance with the traction control mechanism described above. The effect of altering torque across the wheels will adjust for the variations in friction coefficients of ground contact. Normally, the torque differentials will be pulsed for trim correction rather than sustained vehicle torque distribution or suspended part body orientation.

Referring to Figure 8, a further application of the invention is in the control of body roll in a vehicle, for example during cornering. By applying a greater driving torque T2 to the wheels 40b on the outside of the corner, than that the torque Ti applied to the wheels 40a on the inside of the corner, the vehicle body 42 is urged to roll towards the inside of the corner, thereby counteracting the normal tendency to roll towards the outside of the corner under centrifugal forces. This controlled re-distribution of driving torque can be made in response to detection of vehicle cornering, for example by means of lateral accelerometers, or by means of sensors of vehicle speed and steering angle. The fraction of the total driving torque applied to the outside wheels 40b is increased with increasing lateral acceleration during cornering so that the resistance to roll increases as required to keep the vehicle body as level as possible.

As illustrated it is normal for the drive shafts to each wheel to be substantially perpendicular to its propeller shaft in order to maximise the torque effect upon its respective wheel and so across a wheel pair. However, it will be understood by those skilled in the art that it is the perpendicular component of the torque which provides the effect in accordance with the present invention. Thus, the drive shafts could be arranged relative to their respective wheel and propeller shaft at an angle different to perpendicular provided there is a significant perpendicular torque component applied to the wheel for reaction effect in accordance with the present invention. Normally, an angle greater than 45 will be required for such a perpendicular torque component.

From Figures 1 to 8 above, it will be appreciated that reaction to the torque differential across an opposed wheel pair can be utilised in order to move the opposed wheel relative to the suspended part of the vehicle and so alter the weight distribution of that vehicle for traction control. However, as also indicated above such movement is temporary and only maintained while the particular torque differential across an opposed wheel pair is maintained. Clearly, maintenance of such a torque differential is both wasteful in terms of the energy required and also requires more complicated operation of the vehicle when forward or reverse motion is required as the prime purpose of the torque applied to each drive shaft to the opposed wheels. In accordance with the present invention a displacement prop is provided which allows controlled maintenance of the relative displacement between the opposed wheels and the suspended part of the vehicle.

In Figure 9 one embodiment of a displacement prop 100 is illustrated. It win be appreciated this displacement prop 100 is secure between an opposed wheel and a suspended part of a vehicle. Thus, the sprung relationship between the suspended part of the vehicle and the opposed wheel is still achieved through a spring or other device but the displacement prop 100 can be arranged to maintain relative movements between that suspended part of the vehicle and the opposed wheel. In such circumstances, a piston rod 101 can move up and down in the direction of arrowheads A in order to freely accommodate the movement between the opposed wheel and suspended part of the vehicle.

The displacement prop 100 in addition to the piston 101 includes a closed cylinder 102 and a piston 103 secured to the piston rod 101. The cylinder 102 is filled with a fluid such that with displacement of the rod 101 in the direction of arrowheads A fluid can pass through a one way valve 104 and so the piston 103 in order to freely accommodate relative displacement between an opposed wheel secured to the rod 101 and a suspended part of a vehicle secured to the cylinder 102 or at least its housing. It will be understood that movement of the fluid between the respective sides 105, 106 of the prop 100 is required in order to equalise fluidic pressure. However, once relative movement between the suspended part of a vehicle and the opposed wheel has reached its maximum or a desired level, the valve 104 through a flap or similar device 107 prevents return of fluid to the natural relative volume relationship between the two sides 105, 106 of the prop 100 through the valve 104. In such circumstances, it will be appreciated that the relative movement between the suspended part of the vehicle and the opposed wheel will be retained by the prop 100.

Clearly, as the relative movement retained by the prop 100 is not a natural configuration for the relationship between the suspended part of the vehicle and the opposed wheel it will be understood that one side 105, 106 of the prop 100 will be pressurised by the uneven weight distribution of the vehicle. In such circumstances, either the valve 104 or a bleed tube 108 is used to allow passage of fluid between the respective sides 105, 106 of the prop 100 to adjust the relative position of the piston 103 within the cylinder 102 to that required for retention of the movement between the suspended part of the vehicle and the opposed wheel.

The valve 104 and/or the bleed 108 will typically be controlled by the control means used to vary the torque differential across an opposed wheel pair such that the torque reaction creating the movement between the suspended part of the vehicle and the opposed wheel will initially achieve a relative displacement in the direction of arrowheads A and this displacement will be retained by the prop 100 through preventing return movement of liquid between the sides 105, 106 of the prop 100 until release either through the valve 104 or an alternative valve (not shown) or through the bleed 108.

It will be understood that depending upon the efficiency of the nonreturn valve 104 that the relative displacement may be retained by the prop 100 in order to vary the vehicle orientation and therefore weight distribution for relatively long periods if not indefinitely. In such circumstances, the vehicle orientation can be altered as required for better traction control in a sustained manner.

Rather than retaining fluids in either side 105, 106 in order to retain the movement between the suspended part of the vehicle and the opposed wheel, it will be understood that there may simply be provided respective one way valves such that fluid flow in one direction is relatively free through large cross-section apertures while return in the other direction is slow through much narrower apertures in these valves. In such circumstances, there will be a dampening effect in which the movement achieved by the reaction to the torque differential across an opposed wheel pair will be retained for a longer period of time as the lower flow capacity valve allows re-establishment of the natural fluid distribution between the respective sides 105, 106 of the prop 100. In effect, the larger valve flow capacity in one direction allows free accommodation ofthe relative movement between the suspended part of the vehicle and the opposed wheel due to reaction torque whilst the lower flow capacity of the lower cross-section valve transiently sustains that displacement due to the longer period of time required to return the displaced volume of fluid which passes through the larger flow capacity valve for relatively free movement with torque reaction across an opposed wheel pair.

Operation of valves through a control mechanism is relatively well known to those skilled in the art. Thus, a baffle or plate such as plate 107 in Figure 9 may be used and displaced such that there is lift-off as a result of fluid flow in the direction of arrowheads B due to relative displacement in the direction of arrowheads A between the suspended part of the vehicle relative to the opposed wheel through the rod 101. However, when sufficient displacement has been achieved the plate 107 may be closed through a magnetic or servo coupling to prevent further flow of fluid in the direction of arrowheads B. It will also be understood that the pressure of fluid in the side 106 of the prop 100 will also act against the plate 107 in order to close the valve 104 in some circumstances. Alternatively, a swaging plate could be placed across a flow aperture in the piston 103 in order to prevent fluid flow.

Similarly, when return of fluid to its natural steady state between the sides 105, 106 of the prop 100 is required, the valves in the piston 103 may be opened fully or partially in order to allow ready fluid flow therethrough in order to balance fluid pressures either side 105, 196 of the prop 100. Thus, the vehicle weight is supported by the existing spring or other mechanisms until further movement is produced by the reaction to torque differential across an opposed wheel pair of the vehicle.

As an alternative to providing a piston and cylinder it will be understood that a ratchet arrangement could be provided in which a detent engages a ratchet as the relative movement between a suspended part of a vehicle and an opposed wheel is produced by the torque differential across an opposed pair of such opposed wheels. In such circumstances, the displacement prop would be released when required by simply dis-engaging the detent latch from the ratchet to enable the vehicle to return to its natural orientation or that currently provided by the reaction to the torque differential across an opposed pair of opposed wheels.

A further alternative could be to provide a cable and reel arrangement in which the reel and cable end are secured between the suspended part of a vehicle and the opposed wheel such that relative movement between that suspended part and the opposed wheel is accommodated and retained by reeling in and reeling out the cable and braking the reel as required. Clearly, such a cable and reel arrangement the reel or the cable may be braked to retain and therefore sustain the relative movement between the suspended part of the vehicle and the opposed wheel in order to provide torque control through weight distribution as described previously.

The brake or detent latch used in either the ratchet arrangement or the cable and reel arrangement could be operated in accordance with known techniques utilising magnetic or servo motor displacement in order to achieve necessary retention of relative displacement between the suspended part of the vehicle and the opposed wheel as a result of torque reaction across a wheel pair.

It will be understood that generally all the opposed wheels of a vehicle win incorporate a displacement prop in accordance with the present invention in order that relative movements between the respective suspended parts of the vehicle and their opposed wheel can be retained by their displacement prop and so provide more sustained traction control as a result of weight distribution alterations.

Claims

-18CLAIMS

A traction control sustain arrangement for a vehicle, the arrangement comprising a suspended part between at least two opposed wheels on opposed sides thereof and a drive train comprising two propeller shafts coupled through a respective coupling to a respective drive shaft wherein each drive shaft extends substantially transversely to the vehicle and has one end connected to one of said wheels and torque input means for applying a drive torque to each of said propeller shafts wherein the respective couplings between the drive shafts and the propeller shafts are arranged such that driving torque applied to each propeller shaft will tend to apply a torque to its respective drive shaft with a substantial torque component presented in an axis substantially perpendicular to the respective drive shafts so as to tend to move the wheel relative to the suspended part of the vehicle in order to alter the weight distribution between the opposed wheels, the arrangement further comprising control means arranged to control the driving torques applied to each propeller shaft so as to produce controlled variation in the weight distribution between the opposed wheels and so the load presented at each of said opposed wheels, and at least one of said opposed wheels having a displacement prop between that opposed wheel and the suspended part of the vehicle whereby the displacement props substantially freely moves to accommodate relative movement between the opposed wheel and the suspended part as a result of the torque applied to the drive shafts whilst retaining that relative movement until released to maintain the variation in weight distribution for sustained traction control.
2. An arrangement as claimed in claim 1 wherein the displacement prop is configured so that relative movement is released by the displacement prop under the control of the control means.
3. An arrangement as claimed in claim 1 or claim 2 wherein the displacement prop comprises a hydraulic or compressed gas or fluid piston and cylinder arrangement between the opposed wheel and the suspended part of the vehicle.
4. An arrangement as claimed in claim 3 wherein the piston incorporates a one way valve in order to provide for substantially free movement of the piston within the cylinder to accommodate relative free movement between the opposed wheel and the suspended part.
5. An arrangement as claimed in claim 3 or claim 4 wherein the piston incorporates a release valve to allow return of the piston and so release of the relative movement between the opposed wheel and the suspended part of the vehicle.
6. An arrangement as claimed in claim 3, 4 or 5 wherein the one way valve has a significantly greater cross-section for flow therethrough compared to the release valve in order to provide a slower return of the displacement prop than that of the relative free movement between the opposed wheel and the suspended part of the vehicle as a result of torque applied to the respective drive shafts.
7. An arrangement as claimed in claim 1 or claim 2 wherein the displacement prop comprises a ratchet and detent latch.
8. An arrangement as claimed in claim 1 or claim 2 wherein the displacement prop comprises a cable and reel between the opposed wheel and the suspended part of the vehicle.
9. An arrangement as claimed in claim 7 or claim 8 wherein the displacement prop incorporates a brake or clamp in order to retain the relative free movement between the opposed wheel and the suspended part of the vehicle.
10. An arrangement as claimed in claim 9 wherein the brake or clamp is activated by the control means.
11. An arrangement as claimed in any preceding claim wherein the arrangement incorporates a displacement prop for each of the opposed wheels.
12. A traction control sustain arrangement substantially as hereinbefore described with reference to the accompanying drawings.
13. A vehicle incorporating a traction control sustain arrangement as claimed in any preceding claim.