Patent GB-1437769-A (GB)
Title: Powered brake systems for vehicles
IPC: B60T13/14
Filed: 1974-05-29
Abstract: 1437769 Anti-skid brake systems AISIN SEIKI KK 29 May 1974 [29 May 1973] 23763/74 Heading F2F An anti-skid braking system comprises a control valve 30 connected between slave cylinders and a powered hydraulic pressure source, an anti-skid control valve assembly connected between a reservoir 17 and the control valve for connecting the slave cylinders to the reservoir or to the control valve in reponse to an electrical signal indicating a wheel skid condition and a valve connected between the control valve and the anti-skid control valve assembly for limiting the rate of supply of hydraulic fluid under pressure only when the pressure of fluid supplied by the control valve is higher than that at the slave cylinders. As shown, an unloader valve 12, actuated by an electromagnetic valve 14, is connected to a pump 10 driven by an engine 11 and to a reservoir 17, a safety valve 22 being connected to a motor-driven pump 20 which is activated when the pump 10 is inoperative. Accumulators 24, 25 for front and rear brakes 26, 27, provided with sensors 55, 80, are connected between the safety valve and a control valve 30 actuated by a brake pedal 31. Connected to the valve 30 are, respectively, for the front and rear brakes, orifice valves 33, 58, main valves 46, 71 and by-pass valves 48, 73, these valves and the valve 14 being connected to electronic circuitry 56 which provides a brake control signal on sensing an actual or incipient skid condition of the vehicles wheels. In normal brake operation, depression of the pedal 31 causes pressurized fluid to be transmitted via the chamber 40 and port 45 of the valve 33 to the main valve 46, the by-pass valve 48 and to the front wheel brakes 26; pressurized fluid is also transmitted to the chamber 41 of the valve 33 so that pressure on both sides of the piston 36 thereof is equalized, the piston being maintained in position to retain the ball valve 42 open since the load of the spring 44 is greater than that of the spring 43. Upon release of the pedal pressurized fluid is returned through the passage 38 in the valve 33. The rear brakes 27 are operated in a similar manner. When the electronic circuitry 56 senses a change in the rate of rotation of wheels of the vehicle indicating a skid condition, the valve 14 is energized and pressurized fluid passes from the valve 12 to the valve 22; the main valve 46 is also energized and pressurized fluid from the front brakes 26 passes back to the valve through the by-pass valve 48 and to the reservoir 17 via a restriction orifice 51. Energization of the by-pass valve 48 allows pressurized fluid to pass from the front brakes 26 back to the reservoir 17 through the main valve 46 and via the restriction orifices 53, 51. When the braking pressure has been decreased to such an extent that the skid condition is terminated, the main valve 46 is de-energized and the piston 36 of the valve 33 moves against the bias of the spring 44 whereby the ball valve 42 closes and pressurized fluid from the control valve 30 is transmitted through restriction orifice 39, port 45, main and by-pass valves 46, 48 to the front brakes 26; the rate of re-application of full braking pressure is determined by the orifice 39. When the bypass valve 48 is actuated during re-application of the brakes the rate of re-application is determined by the restriction orifices 39, 53. In a modification, a spool 33a, Fig. 7, of the orifice valve 33 is moved against the bias of a spring 33b by the pressurized fluid transmitted from the control valve 30 to the conduit 47 via from the chamber 33c via a restriction orifice 33e. Various modifications, Figs. 7, 9 and 11 (not shown), of the system and the valves 12, 14 between the pump 10 and the accumulators 24, 25 are described, and the unloader valve 12 may be dispensed with, Fig. 11 (not shown).