CONTROL ARRANGEMENT

Abstract: An active roll control system (10) for attachment to a vehicle having a wheel suspension system (54, 56, 58, 60) comprises an actuator (62) attached by a linkage (62c, 54a) to the wheel suspension system. The actuator (62) is controlled by a programmable computer (40) having input signals (46) from a lateral accelerometer and a load cell (66) and an output signal to a servo-valve (64) controlling the hydraulic fluid to the actuator. The active roll control system operates to maintain the vehicle in a substantially level state about the vehicle longitudinal axis.

Description: CONTROL ARRANGEMENT 1 This invention relates to motor vehicles. In particular the invention relates to an active roll control arrangement for a motor vehicle already equipped with wheel suspension systems. For example, such wheel suspension systems can comprise springs and dampers. The handling and ride characteristics of road vehicles are essentially a compromise because the wheel suspension systems cannot manage to the fullest extent all the different types of motion of the motor vehicle. Usually wheel suspension systems incorporating springs and dampers provide adequate handling and ride qualities whilst the vehicle is travelling in a straight line. When the motor vehicle turns a corner there is a tendency for the motor vehicle to roll about its longitudinal axis under the application of lateral forces incurred by the cornering motion. The conventional spring and damper wheel suspension system will be designed to try and minimise the degree of roll, and sometimes further arrangements such as anti roll bars are fitted to further minimise the degree of roll. However a degree of roll is usually encountered causing uncomfortable movement to drivers and passengers and unwelcome motion of loose objects in the motor vehicle. It is therefore desirable that the motor vehicle remains level in a lateral sense whilst the vehicle is cornering. Accordingly, the present invention is concerned with providing a roll control arrangement for a vehicle which is already equipped with a known form of wheel suspension device or devices and which is active only during vehicle cornering to correct the vehicle roll and to maintain the vehicle substantially level in the lateral sense during vehicle cornering. Accordingly the invention provides, in a vehicle having wheel suspension means to support the vehicle deadweight and having damping means to attenuate dynamic loads, an active roll control system comprising at least one actuating means associated with at least one pair of the pairs of vehicle wheels, the said at least one actuating means being secured to effect displacement between the sprung and unsprung mass of the vehicle, and means responsive to loads applied to the actuating means to generate a signal to cause the actuating means to operate as a function of the said signal, so that loads are applied to the vehicle suspension means to oppose any dynamic loads tending to roll the vehicle. An actuating means can be provided for one or both pairs of vehicle wheels, and the actuating means can comprise a double acting hydraulic actuator. The attachment of the or each hydraulic actuator can include a linkage arranged so that upon operation of the or each hydraulic actuator the vehicle is maintained substantially level about its longitudinal axis. The attachment of the or each hydraulic actuator can be between the sprung and unsprung mass or masses of the motor vehicle or between associated unsprung masses of the motor vehicle, for example the two independently suspended front wheels of a motor vehicle. The means responsive to the loading of the actuating means can generate an electric signal and can include signal processing means for the said εigrial. The signal- rocessing means can comprise a computer arranged also to receive electric input signals from a source independent of the loading of the actuating means. The signals from the independent source can comprise signals from a lateral accelerometer and the signals from the means responsive to the loading of the actuating means can originate from a load cell. The supply of hydraulic fluid to the or each hydraulic actuator can be controlled by a servo valve which is included in an hydraulic power supply comprising an hydraulic pump and accumulator. Other control devices can be used as well as, or instead of a servo-valve, for example, a solenoid valve with pulse width modulation. The or each servo valve can be controlled by a signal from the signal processing means. In a further arrangement according to the present invention an hydraulic actuator can be provided for each wheel of a motor vehicle, each wheel being equipped with a wheel suspension means, each hydraulic actuator having signal generating means which are used to operate the hydraulic actuators to maintain the motor vehicle substantially level whilst the motor vehicle is cornering. The present invention will now be more particularly described with reference to the accompanying drawings in which: Figure 1 is a diagra atic representation of one form of roll control arrangement according to the present invention and Figure 2 illustrates one form of linkage for use with the roll control arrangement illustrated in Figure 1. Referring to the figures a roll control arrangement 10 comprises two double acting hydraulic actuators 12 and 14 located at the front and rear of a motor vehicle (not shown) respectively. Each hydraulic actuator comprises a cylinder 12A, 1AA attached to the sprung mass 16 of the motor vehicle and a piston 12B, 14B attached by a piston rod 12C, 1AC to the unsprung mass of the vehicle. For example in the case of the hydraulic actuator 12 the rod 12C can be attached by a suitable linkage (see Figure 2) to the wishbones on which the front wheels of the motor vehicle are mounted and the rear hydraulic actuator 14 can also be attached by a suitable linkage to the rear axle of a vehicle. In this way by means of appropriate linkages a single hydraulic actuator can be used for each pair of vehicle wheels in order to correct the roll of the vehicle which occurs when the vehicle corners. Although the roll control arrangement in Figure 1 illustrates the use of an hydraulic actuator for both the front and rear pairs of wheels it may only be necessary to use an hydraulic actuator and suitable linkage for the front pair of wheels in order to maintain the vehicle substantially level in the lateral sense whilst the vehicle is cornering. The roll control arrangement 10 also includes an hydraulic power supply comprising an hydraulic pump 18, which draws hydraulic fluid from a reservoir 20 and supplies hydraulic fluid to servo valves 22 and 24 associated with the hydraulic actuators 12 and 14 respectively. The hydraulic power supply includes a return line 26 to the reservoir 20. The or each of servo-valve 22 and 24 can be replaced by a solenoid valve provided with pulse width modulation or any other type of electrically controlled hydraulic valve. The servo valves 22 and 24 can be controlled so as to return hydraulic fluid to the reservoir via the return line 26 or to supply hydraulic fluid to the upper part of the hydraulic actuators 12 and 14 by lines 28 and 30 respectively or to the lower part of the hydraulic actuators by lines 32 and 34 respectively. The hydraulic power supply circuit also includes accumulators 36 and 38. The operation of the servo valves 22 and 24 is controlled by a control unit comprising a pre-programmed or programmable computer 40 having on electrical input from load cells 42 and 44 on the actuators 12 and 14 respectively, and input from one or more lateral accelerometers 46 and inputs from other sources 48 and 50 which can be, for example, position and attitude transducers. All of these electrical input signals are processed by the computer to generate an output to each servo valve 22 and 24 to supply and withdraw hydraulic fluid as appropriate from one or both hydraulic actuators 12 and 14 so as to maintain the motor vehicle substantially level in the lateral sense whilst the motor vehicle is cornering. Referring to figure 2 which shows diagramatically a roll control arrangement according to the present invention applied to the suspended front wheels 52 of a motor vehicle (not shown). Each of the wheels 52 is mounted on a wishbone 54 pivoted at 56 to the chassis 58 of the vehicle. A conventional spring and damper strut 60 is mounted between each wishbone 54 and the vehicle structure 58. The roll control arrangement comprises a single actuator 62 comprising a cylinder 62A, piston 62B, piston rod 62C, together with a servo valve 64 and a load cell 66. Each wishbone 54 has a crank arm 54A and the cylinder 62A is connected to one crank arm 54A, whilst the piston rod 62C is connected to other the crank arm 54A. Electrical signals from the load cell 66 pass to a computer (not shown) similar to the computer 40, described with reference to figure 1 and the servo valve 64 receives a control signal from the computer, so that the computer also receives inputs analagous to the inputs 46, 48 and 50. This servo valve 64 forms part of a hydraulic circuit (not shown), similar to the hydraulic circuit shown in figure 1, that is a circuit including a pump, reservoir, and accumulator. It will be appreciated that extending or reducing the length of the actuator 62, will cause each wishbone 54 to rotate about its pivot 56. If the vehicle is cornering and is tending to roll in the direction of arrow A, thereby causing the right hand strut 60 to compress and the left hand strut 60 to extend, the signal from the computer to the servo valve 64 will be such that hydraulic fluid will be pumped from the right hand side of the cylinder 62A and hydraulic fluid will be admitted to the left hand side of the cylinder 62A, thereby shortening the actuator 62 and causing the left hand strut 60 to compress and the right hand strut 60 to extend in order to maintain the vehicle substantially level whilst cornering. Whilst the motor vehicle is travelling in a straight line the roll control arrangement 10 is inoperative and the deadweight of the vehicle and the dynamic forces acting on the vehicle are reacted by the existing wheel suspension arrangements for the wheels of the motor vehicle. It will be appreciated that whilst the motor vehicle is travelling in a straight line there could be electric signals generated by the load cells 42 and 44 and also from the other sources 48 and 50. However the logic of the signal processing is such that unless there is an input from the lateral accelerometer 46 which senses the forces generated when the motor vehicle corners, signal processing will not occur and thus there will be no output from the computer 40 to one or both of the servo valves 22 and 2 . It will also be appreciated that a roll control arrangement according to the present invention does not comprise part of the vehicle suspension system. The roll control arrangement according to the present invention is not operational whilst the vehicle is travelling in a straight line or stationary, and its function is to react the loads generated due to vehicle cornering so that the vehicle is maintained substantially level in a lateral sense. Therefore the roll control arrangement of the present invention functions to level the vehicle in the lateral sense, i.e. about the longitudinal axis of the vehicle and does not form part of the normal vehicle suspension arrangements. The roll control arrangement according to the present invention is load sensitive, that is as the loads on one or both of the hydraulic actuators will vary according to the rate of cornering the electric signals generated by the load cells will vary and therefore the correcting displacement of the hydraulic actuators brought about by the control of the respective servo valves will vary according to the applied load.

Claims: CLAIMS 1 0 1 In a vehicle having wheel suspension means to support the vehicle dead weight and having damping means to attenuate dynamic loads, the provision of an active roll control system comprising at least one actuating means associated with at least one pair of the pairs of vehicle wheels, the said at least one actuating means being secured to effect displacement between the sprung and unsprung mass of the vehicle, and means responsive to loads applied to the actuating means to generate a signal to cause the actuating means to operate as a function of the said signal, so that loads are applied to the vehicle suspension means to oppose any dynamic loads tending to roll the vehicle. 2 A vehicle as claimed in claim 1 in which the actuating means comprises a double acting hydraulic actuator, the actuator being connected to the suspension means of the or each pair of vehicle wheels by an actuating linkage, the actuating linkage being arranged to move the suspension means of one vehicle wheel of the said pair of vehicle wheels in one direction and the suspension means of the other vehicle wheel in the opposite direction to maintain the vehicle in a substantially level position about its longitudinal axis. 3 A vehicle as claimed in claim 2 in which the said pair of vehicle wheels comprise the front wheels of a vehicle. A vehicle as claimed in claim 2 in which the said pair of vehicle wheels comprise the rear wheels of a vehicle. A vehicle as claimed in claim 2 in which an active roll control system is provided for bo -. pairs of vehicle wheels. A vehicle as claimed in claim 2 in which the linkage includes an arm rigidly secured to a pivotable arm of each wheel of the or each pair of vehicle wheels, a rod attached to the piston of the actuator attached to one of said arms and a further rod extending from the actuator and attached to the other one of said arms. Vehicle as claimed in claim 2 in which the actuating means is secured between the sprung and unsprung mass of the vehicle. A vehicle as claimed in claim 2 in which the actuating means is secured between two unsprung masses of the vehicle. A vehicle as claimed in any one of the preceding claims in which the means responsive to the loading of the actuating means generates an electrical signal, and includes means for processing said signal. A vehicle as claimed in claim 9 in which the processing means receive electrical signals from a source independent of the loading of the actuating means. A vehicle as claimed in claim 10 in which the independent source comprises a lateral accelerometer. A vehicle as claimed in any one of the preceding claims in which the means responsive to the loading of the actuating means comprises a load cell. A vehicle as claimed in any one of the preceding claims 9-12 in which the actuator has an hydraulic fluid supply including a pump, a reservoir and an accumulator, the hydraulic supply to the actuator being controlled by a servo-valve, the servo-valve being controlled by an output from the signal processing means. A vehicle as claimed in any one of the preceding claims 9-13 in which the signal processing means comprises a computer programmed to control the servo-valve so that the actuator operates on the wheel suspension means to maintain the vehicle on a substantially level state about the longitudinal axis of the vehicle.

Inventors: HARVEY-BAILEY RHODERICK MCINTY, HARVEY-BAILEY, RHODERICK, MCINTYRE
Applicants: SPEECHBOND LIMITED
Application year: 1989
Main classification: B60G17
IPC codes: B60G17, B60G21