GB2377415A

GB2377415A - A semi-active roll control system for a motor vehicle

Info

Publication number: GB2377415A
Application number: GB0212835A
Authority: GB
Inventors: Robin N Oakley
Original assignee: Delphi Technologies Inc
Current assignee: Delphi Technologies Inc
Priority date: 2001-06-22
Filing date: 2002-06-05
Publication date: 2003-01-15
Anticipated expiration: 2022-06-05
Also published as: GB0212835D0; GB2377415B

Abstract

A roll control system 20 for installation between axially aligned wheels of a motor vehicle comprises a torsion bar 22; an actuator 24 attached to one end 28 of the torsion bar and attachable to one of the wheels; and an electronic control unit 26 monitoring one or more predetermined signals. The actuator is of the piston-and-cylinder type and includes ratchet teeth 60 formed on the piston rod 58 and an electrically actuated device 36 mounted on the actuator housing 52 adjacent one end of the housing and actuable by the control unit in response to the monitored signals. A lock pin 38 is mounted in and movable by the device 36, the lock pin being engageable with the ratchet teeth 60 in the piston rod 58 to allow axial movement of the piston rod relative to the housing in a direction towards a predetermined relative position. The device 36 is actuable to move the lock pin 38 between a first engaged position and a second disengaged position.

Description

A ROLL CONTROL SYSTEM FOR A MOTOR VEHICLE Technical Field The present invention relates to a roll control system for a motor vehicle, and in particular to a semi-active roll control system.

Background of the Invention In order to prevent excessive rolling (which has an impact on vehicle attitude and handling) of a motor vehicle, especially during cornering, it is known to provide a torsion bar between the front wheels of a motor vehicle, and, in some cases, a second torsion bar between the rear wheels. However, during straight line motion of a vehicle and when the vehicle is off-road, the torsion bar can have a detrimental effect on comfort and wheel articulation.

Semi-active roll control systems have been proposed which monitor various vehicle conditions. Such roll control systems include a locking device associated with the torsion bar and the wheels. When the sensed vehicle conditions indicate roll stiffness is not required, the locking device is unlatched to effectively disconnect the effect of the torsion bar between the wheels. When the sensed vehicle conditions indicate that roll stiffness is required, the locking device is latched to connect the wheels by way of the torsion bar. The latch position of the locking device determines the overall effect of the torsion bar on the wheels, and hence determines the level of roll control on the vehicle. In certain circumstances, it is possible to latch the torsion bar in the wrong position. EP-A-1000782 and EP-A-1022169 describe roll control systems using hydraulic fluid which overcome the above mentioned problem.

Summary of the Invention The object of the present invention is to lessen the risk and problems of potential incorrect latching without using hydraulic fluid.

A roll control system in accordance with the present invention for installation between axially aligned wheels of a motor vehicle comprises a torsion bar; an actuator attached to one end of the torsion bar and attachable to

one of the wheels; means attached to the other end of the torsion bar and attachable to the other wheel; and an electronic control unit monitoring one or more predetermined signals; wherein the actuator comprises an axially extending cylindrical housing; a piston slidably mounted inside the housing; a piston rod connected to the piston, extending out of one end of the housing, movable in an axial direction relative to the housing, and having ratchet teeth formed thereon; an electrically actuated device mounted on the housing and actuable by the control unit dependent on the monitored signals; and a lock pin mounted in and movable by the device, the lock pin being engageable with the ratchet teeth on the piston rod to allow axial movement of the piston rod relative to the housing in a direction towards a predetermined relative position; the device being actuable to move the lock pin between a first position in which the lock pin engages the ratchet teeth and a second position in which the lock pin is disengaged from the ratchet teeth.

The means may be a rigid arm, or a second actuator.

In the present invention, the variable force within the or each actuator is such as to tend to move the piston rod relative to the housing to the predetermined relative position, dependent on the arrangement of the ratchet teeth and the lock pin. Where the roll control system comprises two actuators, each actuator preferably moves to either a full rebound position in which the actuator is fully extended, or to a full compression position in which the actuator is fully compressed, dependent on the arrangement of the ratchet teeth and lock pin. If the control unit actuates the device of the or each actuator for roll control, when the piston rod/housing are not at the predetermined relative position, the variable force will act on the actuator to gradually move the piston rod relative to the housing until the predetermined relative position is reached.

As a consequence, the roll control system of the present invention reduces the problem of latching the torsion bar in an incorrect position.

Brief Description of the Drawings

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which :-

Figure 1 is a schematic view of a motor vehicle having a roll c control system in accordance with a first embodiment of the present invention; Figure 2 is a perspective view of the roll control system of Figure

1 ; Figure 3 is a cross-sectional view of one of the actuators of the roll control system of Figure 2; Figure 4 is a schematic view of a motor vehicle having a roll control system in accordance with a second embodiment of the present invention; Figure 5 is a perspective view of the roll control system of Figure 4; and Figure 6 is a cross-sectional view of the actuator of the roll control system of Figure 5.

Description of the Preferred Embodiment Figure 1 shows an outline of a motor vehicle 10 having a pair of front wheels 12 and a pair of rear wheels 14. Each wheel 12,14 is rotatably mounted on an axle 16 and attached to the body of the motor vehicle 10 by way of a suspension unit 18. A roll control system 20 in accordance with a first embodiment of the present invention is connected between the front wheels 12.

Alternatively, a substantially identical roll control system may be connected between the rear wheels 14. As a further alternative, substantially identical roll control systems may be connected between the front wheels 12 and the rear wheels 14.

Referring to Figure 2, the roll control system 20 comprises a torsion bar 22, first and second actuators 24, and an electronic control unit 26.

The actuators 24 are substantially identical. Each actuator 24 is mounted between an end 28 of the torsion bar 22 and one of the suspension units 18.

A preferred arrangement for each actuator 24 is shown in Figure 3. Each actuator 24 comprises an axially extending cylindrical housing 52 which has a closed first end 54, and a substantially closed second end 55. A piston 34 makes a sealing sliding fit with the inner surface 56 of the housing 52.

The piston 34 defines, within the housing 52, a first (compression) chamber 30 between the piston 34 and the first end 54, and a second (rebound) chamber 32 between the piston and the second end 55. A piston rod 58 is secured to the piston 34, extends through the rebound chamber 32 and out of the second end 55 of the housing 52, and is secured to one end 28 of the torsion bar 22. The first end 54 of the housing 52 is secured to the suspension unit 18. The piston 34 and piston rod 58 are movable in the axial direction relative to the housing 52. An electrically actuated device in the form of a solenoid valve 36 is mounted on the housing 52 adjacent the second end 55 and extends into the rebound chamber 32. A lock pin 38 is mounted in, and is movable by, the solenoid valve 36. Ratchet teeth 60 are formed on the piston rod 58 and are engageable by the lock pin 38.

The valve 36 is actuable to move the lock pin 38 between a first position in which the lock pin engages the ratchet teeth 60 and a second position in which the lock pin is disengaged from the ratchet teeth. In the first position, the lock pin 38 engages the ratchet teeth 60, and the design of the teeth and pin are such as to allow the piston rod 58 to move axially relative to the housing 52 in one direction, but to prevent relative axial movement in the opposite direction. In the second position, the lock pin 38 is disengaged from the ratchet teeth 60, and the piston rod 58 is free to move relative to the housing 52. The lock pin 38 is preferably biased to the first position, preferably with a spring (not shown), and the valve 36 is actuated to move the lock pin to the second position. The valve 36 is electrically connected to the control unit 26 by electrical leads 40.

The position of each piston 34 and piston rod 58 relative to the housing 52 is dependent on the position of the associated end 28 of the torsion bar 22 relative to the associated suspension unit 18. When the actuator 24 is

substantially in full compression, as shown in Figure 3, the volume of the compression chamber 30 is at a minimum. In the present embodiment, the desired position (the predetermined relative position of the piston rod to the housing) of each actuator 24, when roll stiffness is required, is full compression, when there is substantially no torque in the torsion bar 22 during straight line motion of the motor vehicle with both actuators in full compression. Due to the dynamic forces exerted on the actuators 24 by the road or the vehicle body, there are forces exerted on the actuator which move each actuator towards full compression (because of the above mentioned relative movement in one direction only). The ratchet teeth 60 and lock pin 38 are therefore such as to allow the actuator 24 to move to full compression when the teeth are engaged by the lock pin, but to substantially prevent movement in a direction which extends the actuator.

The control unit 26 is preferably a microprocessor which receives signals from one or more sensors (such as a vehicle speed sensor 42, a transmission speed sensor 44, a steering wheel angle sensor 46, and/or a driver preference switch 48) monitoring certain vehicle conditions and/or driver preference. The control unit 26 controls the actuation of the valve 36, and hence the movement of the lock pin 38 between the first position and the second position, dependent on the signals received from the sensors and driver preference switch, and may also actuate an alarm, such as a warning light 50, inside the vehicle 10 during certain monitored conditions.

When the control unit 26 determines that no roll control is required (typically during straight line motion of the vehicle 10 or when offroad), the valves 36 are actuated to move the lock pins 38 to their second position such that piston rod 58 can freely move relative to the housing 52 of each actuator 24. The torsion bar 22 is, therefore, substantially disconnected from the front wheels 12.

When the control unit 26 determines that roll control is required, the valves 36 are actuated to move the lock pins 38 to their first position to engage the ratchet teeth 60 on the piston rod 58 of each actuator 24. The pistons

34 in each actuator 24 are therefore effectively latched to prevent extension of the actuators 24 due to the conditions sensed by the control unit 26. In this situation, the position of the torsion bar 22 relative to the front wheels 12 is effectively locked to provide the desired roll control for the vehicle 10. As mentioned above, the desired position for each actuator 24 is full compression.

If, however, one of the pistons 34 is latched such that the associated actuator 24 is not in full compression, the torsion bar 22 and any road irregularities, will exert a variable force on that piston. The effect of the variable force is to push the ratchet teeth 60 past the lock pin 38. Such an arrangement allows the incorrectly latched piston 34 to gradually move to reduce the volume of the compression chamber 30, and hence bring the actuator 24 towards a full compression position.

The actuators 24 may additionally include an elastomeric stop member 72 positioned in the compression chamber 30 adjacent the first end 54 of the housing 52 to substantially prevent the piston 34 directly engaging the first end. Also, a stop member 74 may be positioned in the rebound chamber 32 adjacent the valve 36 to substantially prevent the piston 34 directly engaging the valve and the second end 55 of the housing 52. The compression chamber 30 and the rebound chamber 32 are preferably filled with air. In this arrangement, apertures are preferably formed in the housing 52 to allow air to enter and leave the chambers during motion of the piston 34 relative to the housing. One or both chambers 30,32 may contain lubricating fluid.

Alternative arrangements for the above described arrangement for each actuator 24 may be used. For example, the mounting arrangement of the actuator 24 may be reversed with the piston rod 58 attached to the suspension unit 18 and the housing 52 attached to the torsion bar 22. The arrangement of the ratchet teeth 60 and lock pin 38 may be reversed to allow the actuators 24 to move to a full extended position (the predetermined relative position of the piston rod to the housing) when the teeth and lock pins are engaged, and to substantially prevent movement in a direction which compresses the actuators. The lock pins 38 may be biased to the second

position, and the valves 36 actuated to move the lock pins to the first position.

Each valve 36 may be mounted on the outside of the housing 52 with the lock pin 38 extending into the rebound chamber 32. Alternatively, each valve 36 may be mounted on the outside of the housing 52 with the lock pin 38 engaging the ratchet teeth outside the housing.

Figure 4 shows an outline of a motor vehicle 10 having a pair of front wheels 12 and a pair of rear wheels 14. Each wheel 12,14 is rotatably mounted on an axle 16 and attached to the body of the motor vehicle 10 by way of a suspension unit 18. A roll control system 200 in accordance with a second embodiment of the present invention is connected between the front wheels 12.

Referring to Figure 5, the roll control system 200 comprises a torsion bar 22, an actuator 24', an arm 25, and an electronic control unit 26.

The actuator 24'is mounted between one end 28 of the torsion bar 22 and one of the suspension units 18. The arm 25 is mounted between the other end 29 of the torsion bar 22 and the other suspension unit 18.

A preferred arrangement for the actuator 24'is shown in Figure 6. The actuator 24'comprises an axially extending cylindrical housing 52' which has a closed first end 54', and a substantially closed second end 55'. A piston 34'makes a sliding fit with the inner surface 56'of the housing 52'. The piston 34'defines, within the housing 52', a first (compression) chamber 30' between the piston 34'and the first end 54', and a second (rebound) chamber 32'between the piston and the second end 55'. A piston rod 58'is secured to the piston 34', extends through the rebound chamber 32'and out of the second end 55'of the housing 52', and is secured to the one end 28 of the torsion bar 22. The first end 54'of the housing 52'is secured to the suspension unit 18.

The piston 34'and piston rod 58'are movable in the axial direction relative to the housing 52'. An electrically actuated device in the form of a solenoid valve

36'is mounted on the housing 52'and extends into the rebound chamber 32'.

A lock pin 38'is mounted in, and is movable by, the solenoid valve 36'.

Ratchet teeth 60'are formed on the piston rod 58'and are engageable by the lock pin 38'. The ratchet teeth 60'have first and second portions 62,64 positioned on either side of a slot 66 formed in the piston rod 38'. The shape and disposition of teeth of the first portion 62 is reversed relative to (a mirror image of) the shape and disposition of the teeth of the second portion 64.

The valve 36'is actuable to move the lock pin 38'between a first position in which the lock pin engages the ratchet teeth 60'and a second position in which the lock pin is disengaged from the ratchet teeth. In the first position, the lock pin 38'either engages the ratchet teeth 60'of the first portion 62 or the ratchet teeth of the second portion 64, and the design of the teeth and pin are such as to allow the piston rod 58'to move axially relative to the housing 52'in a direction towards a predetermined relative position when the pin engages the slot 66. When the lock pin 38'engages the slot 66 further relative axial movement between the piston rod 58'and the housing 52'is substantially prevented. In the second position, the lock pin 38'is disengaged from the ratchet teeth 60', and the piston rod 58'is free to move relative to the housing 52'. The lock pin 38'is preferably biased to the first position, preferably with a spring (not shown), and the valve 36'is actuated to move the lock pin to the second position. The valve 36'is electrically connected to the control unit 26 by electrical leads 40'.

The position of the piston 34'and piston rod 58'relative to the housing 52'is dependent on the position of the end 28 of the torsion bar 22 relative to the associated suspension unit 18. In the present embodiment, the desired position of the actuator 24', when roll stiffness is required, is when the lock pin 38'is engaged with the slot 66 (as shown in Figure 6), when there is substantially no torque in the torsion bar 22 during straight line motion of the motor vehicle. Due to the dynamic forces exerted on the actuator 24'by the road or the vehicle body, there are forces exerted on the actuator which move the piston rod 58'relative to the housing 52'until the predetermined relative

position is reached (because of the above mentioned relative movement). The ratchet teeth 60'and lock pin 38'are therefore such as to allow the actuator 24' to extend or contract in length until the predetermined relative position is achieved (when the teeth are engaged by the lock pin), but to substantially prevent relative movement after the predetermined relative position is achieved.

The control unit 26 is preferably a microprocessor which receives signals from one or more sensors (such as a vehicle speed sensor 42, a transmission speed sensor 44, a steering wheel angle sensor 46, and/or a driver preference switch 48) monitoring certain vehicle conditions and/or driver preference. The control unit 26 controls the actuation of the valve 36', and hence the movement of the lock pin 38'between the first position and the second position, dependent on the signals received from the sensors and drive preference switch, and may also actuate an alarm, such as a warning light 50, inside the vehicle 10 during certain monitored conditions.

When the control unit 26 determines that no roll control is required (typically during straight line motion of the vehicle 10 or when offroad), the valve 36'is actuated to move the lock pin 38'to its second position such that piston rod 58'can freely move relative to the housing 52'of the actuator 24'. The torsion bar 22 is, therefore, substantially disconnected from the front wheels 12.

When the control unit 26 determines that roll control is required, the valve 36'is actuated to move the lock pin 38'to its first position to engage the ratchet teeth 60'on the piston rod 58'of the actuator 24'. The piston 34'in the actuator 24'is therefore effectively latched to prevent extension or contraction of the actuator 24'due to the conditions sensed by the control unit 26. In this situation, the position of the torsion bar 22 relative to the front wheels 12 is effectively locked to provide the desired roll control for the vehicle 10. As mentioned above, the desired position for the actuator 24'is when the piston rod 58'is at the predetermined position relative to the housing 52'. If, however, the piston 34'is latched such that the associated actuator 24'is not in the desired position, the torsion bar 22 and any road irregularities, will exert a

variable force on that piston. The effect of the variable force is to push the ratchet teeth 60'past the lock pin 38', until the lock pin engages in the slot 66.

Such an arrangement allows the incorrectly latched piston 34'to gradually move (extend or contract), and hence bring the actuator 24'towards the desired position.

The actuator 24'may additionally include an elastomeric stop member 72'positioned in the compression chamber 30'adjacent the first end 54'of the housing 52'to substantially prevent the piston 34'directly engaging the first end. Also, a stop member 74'may be positioned in the rebound chamber 32'adjacent the valve 36'to substantially prevent the piston 34' directly engaging the valve. The compression chamber 30'and the rebound chamber 32'are preferably filled with air. In this arrangement, apertures are preferably formed in the housing 52'to allow air to enter and leave the chambers during motion of the piston 34'relative to the housing. One or both chambers 30', 32' may contain lubricating fluid.

Alternative arrangements for the above described arrangement for the actuator 24'may be used. For example, the mounting arrangement of the actuator 24'may be reversed with the piston rod 58'attached to the suspension unit 18 and the housing 52'attached to the torsion bar 22. The lock pin 38'may be biased to the second position, and the valve 36'actuated to move the lock pins to the first position. The valve 36'may be mounted on the outside of the housing 52'with the lock pin 38'extending into the rebound chamber 32'.

Alternatively, the valve 36'may be mounted on the outside of the housing 52' with the lock pin 38'engaging the ratchet teeth outside the housing.

The present invention provides a roll control system 20,200 in which the actuators 24, 24' reduce problems associated with latching of the torsion bar 22 in the wrong position. Also, the actuators 24, 24' do not require hydraulic fluid.

Claims

1. A roll control system for installation between axially aligned wheels of a motor vehicle, the roll control system comprising a torsion bar; an actuator attached to one end of the torsion bar and attachable to one of the wheels; means attached to the other end of the torsion bar and attachable to the other wheel; and an electronic control unit monitoring one or more predetermined signals; wherein the actuator comprises an axially extending cylindrical housing; a piston slidably mounted inside the housing ; a piston rod connected to the piston, extending out of one end of the housing, movable in an axial direction relative to the housing, and having ratchet teeth formed thereon; an electrically actuated device mounted on the housing and actuable by the control unit dependent on the monitored signals; and a lock pin mounted in and movable by the device, the lock pin being engageable with the ratchet teeth on the piston rod to allow axial movement of the piston rod relative to the housing in a direction towards a predetermined relative position; the device being actuable to move the lock pin between a first position in which the lock pin engages the ratchet teeth and a second position in which the lock pin is disengaged from the ratchet teeth.

2. A roll control system as claimed in Claim 1, wherein the means comprises a second actuator, the two actuators being substantially identical; and wherein the lock pin of each actuator is engageable with the associated ratchet teeth on the piston rod to allow axial movement of the piston rod relative to the housing in one direction, and to substantially prevent axial movement of the piston rod relative to the housing in the opposite direction.

3. A roll control system as claimed in Claim 2, wherein the one direction is towards full compression of the actuators.

4. A roll control system as claimed in Claim 2, wherein the one direction is towards full extension of the actuators.

5. A roll control system as claimed in Claim 1, wherein the means is a rigid arm.

6. A roll control system as claimed in Claim 5, wherein the ratchet teeth on the piston rod comprise a first portion and a second portion positioned respectively on either side of a slot formed in the piston rod; the shape and disposition of the teeth of the first portion being reversed relative to the shape and disposition of the teeth of the second portion; and wherein the lock pin is engageable with the ratchet teeth to allow axial movement of the piston rod relative to the housing to allow the lock pin to move towards the slot, but to prevent the lock pin moving away from the slot.

7. A roll control system as claimed in any one of Claims 1 to 6, wherein the lock pin of the or each actuator is biased towards the first position and is movable, on actuation of the electrically actuated device, to the second position.

8. A roll control system as claimed in any one of Claims 1 to 6, wherein the lock pin of the or each actuator is biased towards the second position and is movable, on actuation of the electrically actuated device, to the first position.

9. A roll control system as claimed in any one of Claims 1 to 8, wherein the electrically actuated device of the or each actuator is mounted on the housing to extend into the housing adjacent said one end thereof.

10. A roll control system as claimed in any one of Claims 1 to 9, wherein the electrically actuated device of the or each actuator is a solenoid valve.

11. A roll control system as claimed in any one of Claims 1 to 10, wherein the or each actuator further includes first and second, axially spaced, stop members engageable by the piston to limit the axial movement of the piston rod relative to the housing.

12. A roll control system as claimed in any one of Claims 1 to 11, wherein the control unit is a microprocessor which is electrically connected to, and receives the predetermined signals from, one or more sensors mountable

on the vehicle and monitoring predetermined vehicle operating conditions, z : l and/or a driver preference switch.

13. A roll control system as claimed in any one of Claims 1 to 12, wherein the piston rod of the or each actuator is attached to the torsion bar.

14. A roll control system substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.