GB2286805A

GB2286805A - Vehicle roll control system

Info

Publication number: GB2286805A
Application number: GB9402919A
Authority: GB
Inventors: Nouredine Benkaza; Jacques Loche
Original assignee: ACG France SAS
Current assignee: ACG France SAS
Priority date: 1994-02-16
Filing date: 1994-02-16
Publication date: 1995-08-30
Anticipated expiration: 2014-02-16
Also published as: GB9402919D0; GB2286805B

Abstract

A vehicle roll control system (22, 24 Fig. 1) for a vehicle (10) having a pair of wheels (12, 16) each rotatable on an axle (14, 18), comprises a torsion bar 26 which can twist about its longitudinal axis; a pair of arms (28, 30) extending substantially perpendicular to the torsion bar, the arms being fixed to the torsion bar at one end and being connectable to respective axles at the other end. A lever 32 is fixed to the torsion bar adjacent each arm, each lever having a pair of opposed surfaces 44, 46 which are substantially parallel and which extend substantially parallel to the longitudinal axis; and twist control means comprising an actuator 34, 35 positioned about each lever and actuator control means (90 Fig. 5), each actuator comprising a pair of actuable pistons (60, 62 Fig. 4) positioned on opposite sides of the respective lever, each piston being engageable with one of the opposed surfaces, and the actuator control means, on detection of a predetermined vehicle condition, applying a force to the pistons such that each piston applies a predetermined force to its respective opposed surface to control the twist stiffness of the torsion bar. <IMAGE>

Description

VEHICLE ROLL CONTROL SYSTEM The present invention relates to a roll control system for a motor vehicle.

The aim of the present invention is to provide an active roll control system which is actuable when one or more monitored vehicle conditions indicates roll control is required.

To this end, a vehicle roll control system in accordance with the present invention for a vehicle having a pair of wheels each rotatable on an axle, comprises a torsion bar which can twist about its longitudinal axis; a pair of arms extending substantially perpendicular to the torsion bar, the arms being fixed to the torsion bar at one end and being connectable to respective axles at the other end; a lever fixed to the torsion bar adjacent each arm, each lever having a pair of opposed surfaces which are substantially parallel and which extend substantially parallel to the longitudinal axis; and twist control means comprising an actuator positioned about each lever and actuator control means, each actuator comprising a pair of actuable pistons positioned on opposite sides of the respective lever, each piston being engageable with one of the opposed surfaces, and the actuator control means, on detection of a predetermined vehicle condition, applying a force to the pistons such that each piston applies a predetermined force to its respective opposed surface to control the twist stiffness of the torsion bar.

The present invention will now be described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic presentation of a vehicle incorporating an embodiment of vehicle roll control system in accordance with the present invention at the front and at the rear of the vehicle; Figure 2 is a side view of the vehicle roll control system at the front of the vehicle shown in Figure 1; Figure 3 is a side view of the arms of the vehicle roll control system shown in Figure 2; Figure 4 is a cross-sectional view taken on the line IV-IV of Figure 2 of one of the levers, the associated hydraulic actuator, and the torsion bar; Figure 5 is a schematic diagram of part of the hydraulic and electrical control circuit of the vehicle roll control system shown in Figure 2; and Figure 6 is a similar view to Figure 4 of a modified hydraulic actuator.

Referring to Figure 1, a vehicle 10 is shown schematically and comprises a pair of front wheels 12 each rotatably mounted on an axle 14, a pair of rear wheels 16 each rotatably mounted on an axle 18, and a shocking absorbing system 20 associated with each wheel. A vehicle roll control system 22 in accordance with the present invention is associated with the front wheels 12, and a vehicle roll control system 24 in accordance with the present invention is associated with the rear wheels 16. The vehicle roll control systems 22, 24 are substantially the same but with modifications made solely to allow fitting to the vehicle 10.

Referring in more detail to Figures 2 to 5, the vehicle roll control system 22 for the front of the vehicle comprises a torsion bar 26, a first arm 28, a second arm 30, a pair of levers 32,33, and a pair of hydraulic actuators 34,35. The torsion bar 26 (which has a longitudinal axis A) is mounted on the vehicle by a pair of resilient mounts 36 in conventional manner to extend longitudinally between the wheels 12. The first and second arms 28,30 (Figure 3) are fixed at one end 38 by a splined connection 40 to the torsion bar 26. The other end 4? of each arm 28,30 is connected to the axle 14 of one of the front wheels 12. The first and second arms 28,30 extend substantially parallel to one another when the vehicle is stationary, and substantially perpendicular to the torsion bar 26.

The levers 32,33 (Figure 4) are fixed to the torsion bar 26 by welding or forging, or by a spline connection, or by any other suitable means, substantially adjacent the one end 38 of the first and second arms 28,30. Each lever 32,33 has substantially parallel opposed surfaces 44,46 which define planes which extend in substantially the same direction as the longitudinal axis A. Each hydraulic actuator 34,35 (Figures 2 and 4) is mounted on a part 47 of the body of the vehicle 10 and a bridge portion 48 thereof straddles the periphery 50 of its respective lever 32,33. Each hydraulic actuator 34,35 further comprises a pair of bodies 52,54 each of which defines a fluid chamber 56,58 within which is mounted a piston 60,62 which makes a sealing sliding fit with its respective body. As shown in Figure 4, the bodies 52,54 are connected to either end of the bridge portion 48.Each hydraulic actuator 34,35 is mounted on the torsion bar 26 in such a manner that the bodies 52,54 lie along side the opposed surfaces 44,46 respectively of the associated lever 32,33, and such that the piston 60,62 in each body is biased into engagement with the adjacent opposed surface by a spring 61,63 respectively.

The fluid chamber 56 of one hydraulic actuator 34 and the fluid chamber 58 of the other hydraulic actuator 35 (see Figures 4 and 5) are fluidly connectable by a fluid line 64 to a fluid pressure source 66. Similarly, the fluid chamber 58 of said one hydraulic actuator 34 and the fluid chamber 56 of the said other hydraulic actuator 35 are fluidly connectable by a fluid line 68 to another fluid pressure source 70. A fluid reservoir 72 supplies hydraulic fluid to the fluid pressure sources 66,70 by way of a fluid line 74. A one-way valve 76 is positioned in the fluid line 74 to prevent flow of fluid from the fluid pressure sources 66,70 to the fluid reservoir 72. The fluid pressure sources 66,70 are substantially identical and comprise a fluid chamber 78 connected to fluid lines 64,68 and 74.A piston 80 makes a sealing fit in the fluid chamber 78 and is reciprocatingly driven by a nut 82 which is threadingly engaged to a screw 84. The screw 84 is rotatably driven by meshing gears 86 connected to a DC electric motor 88. Actuation of the DC motor 88 drives the piston 80 to increase or decrease the fluid pressure in the fluid chamber 78.

The operation of the DC motors 88 is controlled by an electronic and/or computerised control module 90 (Figure 5). The control module 90 operates the DC motors 88 dependent on predetermined vehicle conditions which are determined by signals from a steering sensor 92 (which monitors the steering angle of the front wheels 12) and/or a lateral g sensor 94 (which monitors the sideways acceleration of the vehicle). The control module 90 may also take into account signals received from a vehicle speed sensor 96 and/or any other relevant parameter to determine the required state of operation of the vehicle control system.

If the control module 90 detects that roll control is required, the control module sends a signal to the DC motors 88 to actuate the motors to move the pistons 80 to increase the fluid pressure in the fluid chambers 78. This action increases the fluid pressure in the fluid chambers 56,58 of each hydraulic actuator 34,35 to increase the force applied by the pistons 60,62 to the opposed surfaces 44,46 of each lever 32,33. Different signals are sent to each DC motor 88 of each fluid pressure source 66,70, such that different fluid pressures are generated in each fluid line 64,68.Such action controls the twisting stiffness of the torsion bar 26 by applying a first force to the surface 44 of lever 32 and to the surface 46 of lever 33, and a second force (which is different to the first force) to the surface 46 of lever 32 and to the surface 44 of lever 33, to control the roll of the vehicle 10. The level of the fluid pressure in each fluid chamber 56,58 determines the force applied by the pistons 60,62 to the opposed surfaces 44,46 of the levers 32,33, and hence the determines the amount of control of the twisting stiffness. The hydraulic actuators 34,35, fluid pressure sources 66,70 and control module 90 define twist control means. The control system can also be modified to provide antidive and anti-lift capabilities for the vehicle when certain vehicle operating conditions are detected simply by providing the same fluid pressure in each fluid line 64,68 and hence the same fluid pressure in each fluid chamber 56,58 of each hydraulic actuator 34,35 to effectively lock the levers 32,33. This will allow increased rear braking during anti-lift control, and reduce the risk of wheel spin during anti-dive control.

If the control module 90 detects that roll control is no longer required, the control module sends a signal to the DC motors 88 to drive the pistons 80 to reduce the fluid pressure in the fluid chambers 78. Fluid pressure in the fluid chambers 56,58 of the hydraulic actuators 34,35 is reduced to remove the force applied by the pistons 60,62 to the levers 32,33 due to the fluid pressure.

As shown in Figure 2, a carrier tube 98 may be mounted on the torsion bar 26. The fluid pressure sources 66, 70 may be mounted on the carrier tube 98 along with associated components such as the fluid reservoir 72, and one-way valve 76. This arrangement allows part of the vehicle roll control system 22 to be assembled as a separate module for subsequent attachment to the vehicle 10, with portions of the fluid lines 64,68 being flexible. The carrier tube 98 also provides protection for the torsion bar 26. The same control module 90 can be used for both front and rear vehicle roll control systems 22,24 and thereby provide associated roll control for the front and the rear of the vehicle 10.

As a further alternative, the hydraulic circuit may be omitted, and the hydraulic actuators replaced by electric actuators in which each piston therein is actuated directly by a DC electric motor controlled by the control module 90.

Referring to Figure 6, a modified version of the hydraulic actuators 34,35 is shown. This modified hydraulic actuator 100 comprises a bridge portion 48' and a pair of bodies 52',54' with associated fluid chambers 56',58', pistons 60',62', and springs 61',63' as with the hydraulic actuators 34,35. Also sealingly slidably mounted in each fluid chamber 56',58' is an additional piston 102,104 respectively. Each additional piston 102,104 is biased towards its associated piston 60',62' by a spring 106,108 respectively. Each additional piston 102,104 normally engages a stop 110,112, respectively, formed in the associated fluid chamber 56',58'.The fluid chambers 56',58' are effectively situated between the pistons 60' and 102, and 62' and 104, with the pistons 56',58' having longitudinally extending slots 114 formed therein to allow even distribution of fluid pressure within the fluid chambers 56',58'. Air vents 116 to atmosphere are formed in the bodies 52',54' on the opposite sides of the pistons 102,104 to the fluid chambers 56',58'. By making the resilience of the springs 106,108 greater than the resilience of the springs 61',63', the control of the twist stiffness of the torsion bar 26 can be attained at lower fluid pressures than when using the hydraulic actuator shown Figure 4, and, also, the control of the twist stiffness is damped to provide a smoother control.

In the present invention, the twist stiffness of the torsion bar of a vehicle can be actively controlled dependent on vehicle operating conditions, to control the total vehicle roll stiffness, without significantly affecting the suspension stiffness of the vehicle. The present invention effectively divides the torsion bar into a number of torsion bars of reduced length, the twist stiffness of each of which is controlled.

Claims

Claims:

1. A vehicle roll control system for a vehicle having a pair of wheels each rotatable on an axle, comprising a torsion bar which can twist about its longitudinal axis; a pair of arms extending substantially perpendicular to the torsion bar, the arms being fixed to the torsion bar at one end and being connectable to respective axles at the other end; a lever fixed to the torsion bar adjacent each arm, each lever having a pair of opposed surfaces which are substantially parallel and which extend substantially parallel to the longitudinal axis; and twist control means comprising an actuator positioned about each lever and actuator control means, each actuator comprising a pair of actuable pistons positioned on opposite sides of the respective lever, each piston being engageable with one of the opposed surfaces, and the actuator control means, on detection of a predetermined vehicle condition, applying a force to the pistons such that each piston applies a predetermined force to its respective opposed surface to control the twist stiffness of the torsion bar.

2. A vehicle roll control system as claimed in Claim 1, wherein each actuator is a hydraulic actuator and wherein the actuator control means is a fluid pressure control means which supplies pressurised fluid to a fluid chamber positioned on the opposite side of each piston to the respective opposed surface when the application of force is required by the pistons.

3. A vehicle roll control system as claimed in Claim 2, wherein the fluid pressure control means comprises an electronic control means and fluid pressure sources actuated by the electronic control means to control the pressure of fluid acting on each piston in each fluid chamber.

4. A vehicle roll control system as claimed in Claim 2 or Claim 3, wherein the pistons in each hydraulic actuator are biased into engagement with their respective opposed surface by a spring.

5. A vehicle roll control system as claimed in any one of Claims 2 to 4, wherein the movement of each piston in each hydraulic actuator is damped by a resiliently biased second piston positioned on the opposite side of the fluid chamber to the respective piston.

6. A vehicle roll control system substantially as hereinbefore described with reference to, and a shown in, Figures 1 to 5 of the accompanying drawings.

7. A vehicle roll control system substantially as hereinbefore described with reference to, and a shown in, Figures 1 to 3, 5 and 6 of the accompanying drawings.