GB1453962A - Powered hydrualic braking systems - Google Patents

Abstract

1453962 Hydraulic power assisted brake systems AISIN SEIKI KK 2 Nov 1973 [14 Nov 1972] 51109/73 Heading F2F Hydraulic fluid flows from a pressure source via a main control valve and a subcontrol valve operated by, e.g. wheel skid detectors to one or more wheel brake slave cylinders, the subcontrol valve alternatively communicating the cylinders with a reservoir via a safety valve which blocks communication therewith only if upon main control valve actuation the pressure source fails. In Fig. 1 an engine driven pump 10 feeds an accumulator 16 via a charging valve which allows flow back to the reservoir 12 if the accumulator is at the required pressure. Upon pedal actuation, a piston controlled thereby in the main control valve 22 moves a ball into contact with a spring biased hollow stem to block communication between the reservoir 12 and the subcontrol valve 53. Further piston movement moves an external shoulder of the stem from a seating to open communication between the accumulator 16 and the valve 53. The subcontrol valve 53 has a cupped disc holding a member against a seating to block an outlet from a chamber on one side of a hollow spool so that chambers on either side of the spool, which communicate via a restricted orifice, are at equal pressures. In this condition the spool allows communication between the valve 22 and the slave cylinders 83. Upon receipt of a brake release wheel skid signal, the cupped disc valve member is actuated by a solenoid to allow fluid flow from the one chamber so that the spool moves to block valve 22-cylinders 83 communication and to open cylinders 83-safety valve 81 communication. If the pressure source fails, movement of the main control valve piston reduces chamber volume in the control valve 22 to pressurize the cylinders 83. However, a small leakage of fluid around the subcontrol valve spool is allowed to the reservoir, so this has to be blocked under pressure failure conditions; Fig. 4 shows the safety valve 81 wherein a piston 99 moves leftwardly due to pressure decrease in a chamber 100 communicating with the accumulator 16, allowing a ball 88, previously held clear of a seat providing communication between an inlet from the valve 53 and the reservoir 12, to block such communication. In Fig. 5 the main control valve 22a is fed directly by a pump 10a allowing fluid return to the reservoir 12a via passages 33a, 36a, 32a, 31a when not actuated. Pedal movement causes gradual closing of the passage 32a to increase pressure to the subcontrol valve 53a (similar to valve 53) up to pump pressure. Upon pump failure, the volume decrease in a chamber 29a of the valve 22a causes pressurization of the wheel cylinders 83a. Here the safety valve 81a is solenoidcontrolled by a switch actuated by a pedal 47a, during extra movement due to such failure, to close communication to the reservoir 12a.