Patent GB-1439293-A (GB)
Title: Powered brake system for vehicles
IPC: B60T8/46
Filed: 1974-06-03
Abstract: 1439293 Anti-skid braking systems AISIN SEIKI KK 3 June 1974 [1 June 1973] 24432/74 Heading F2F A powered hydraulic brake system comprises a control valve 16 connected between an hydraulic source and one or more wheel cylinders, an antiskid control valve device connected between a reservoir R and the control valve 16 for connecting the wheel cylinders to either the reservoir R or the control valve 16 in response to an electrical signal indicating a wheel skid condition and an orifice valve 24 connected between the control valve 16 and the antiskid control valve device for limiting the rate of supply of hydraulic fluid under pressure from the control valve 16 to the antiskid control valve device only when the pressure of fluid supplied by the control valve 16 exceeds a predetermined threshold pressure. As shown, the twin braking system includes antiskid pressure control valve assemblies 15, 151 respectively for controlling the braking pressures at the front and rear wheels 42, 42<SP>1</SP> and an engine driven pump PE transmits hydraulic fluid from a reservoir R to a safety valve SV, there being a further pump PM driven by an electric motor for use when the pump PE is inoperative. The safety valve, which blocks transmission of fluid to one or other of the wheel brake circuits in the case of pressure loss therein so that fluid pressure maintainence in the other circuit is insured, is connected to the normally closed control valve 16 which is operated by a brake pedal 17 to control fluid flow to the front and rear brakes via an orifice valve 24 and solenoid actuated anti-skid main control valves 28 and solenoid actuated by-pass valves 35 which together with the valves 28, is connected to an antiskid electronic control circuit 52, the latter supplying output signals received from sensors 50, 501, of, e.g. a dynamo tachometer kind, and when the deceleration of the wheels exceed a predetermined threshold value indicating actual or imminent skidding of the wheels. In operation, under normal running conditions, fluid from the pump PE discharges into the accumulator 21 and when the brakes are applied the normally closed valve 16 progressively opens for passage of fluid via the pipe 22 to the valve 24; when the pressure applied to the control port 26 of the valve 24 is of lesser value than a predetermined threshold value the valve opens and fluid pressure is applied to the front and rear brakes via the normally open main antiskid control and by-pass valves 28, 35. Upon release of the brake pedal 17, fluid discharges to the reservoir R. When the braking pressure exceeds a predetermined threshold value the force of a calibrated spring 60 is overcome and a ball valve, Fig. 2 (not shown) or a valve spool, Fig. 3 (not shown), moves to a closing position whereby fluid flow is restricted by causing it to pass a throttle opening 31. When the orifice valve 24 is closed and the vehicle wheels undergo excessive deceleration during braking such as to cause a skid condition, the control device 52 detects such condition and energizes the valves 28, 35 whereby the brakes are connected to the reservoir R via the throttle 45, valves 28, 35 and throttle 39 to cause a gradual diminution of fluid pressure; when the wheels are no longer in a skid condition the device 52 de-energizes the valves 28, 35 when normal braking is resumed.