Patent GB-1354453-A (GB)
Title: Vehicle breaking system
IPC: B60T8/42
Filed: 1972-04-24
Abstract: 1354453 Hydraulic braking systems AISIN SEIKI KK 24 April 1972 [23 April 1971] 18956/72 Heading F2F In a vehicle braking system a wheel speed responsive electrical signal charges a condenser 107 the output voltage of which is varied in response to the braking effort applied to a braking member such as a pedal 11 and compared with a voltage developed in response to the rotational speed of the wheel 53 such that when the latter voltage is higher than the former the hydraulic pressure to a brake cylinder 54 is arranged to be increased. As shown the system comprises a master cylinder 14, a pressure reducer 16, a pressure intensifier 32 and solenoid valves 60, 80 arranged respectively to cause decrease and increase of the fluid pressure on reception of an appropriate signal from an electronic control circuit. In normal braking fluid passes to wheel cylinder 54 by way of conduit 15, pressure reducer 16, conduit 31, intensifier 32 and conduit 52. Wheel speed is detected by a generator 100 connected through a half-wave rectifier diode 101 and smoothing resistor 102 to one side of a condenser 103 the voltage across which is responsive to wheel speed. Current passes to the bases of transistors 111, 115 which are non-conductive thereby maintaining actuating transistors of solenoid valves 60, 80 non- conductive. When pedal 11 is depressed a switch 105 is opened and a condenser 107 begins to discharge through transistor 108 and resistor 109. This discharging voltage is established by the variable resistance appearing at an hydraulic pressure sensor connected to the base of transistor 108. With higher braking pressures a higher discharge voltage appears at the base of a transistor 111 the potential at which corresponds in turn to the foot pressure at pedal 11. Condenser 103 is connected in parallel with a diode 113 and resistor 114 and a junction e therebetween connects the base of the transistor 115 to the emitter of a transistor 116 thereby providing a comparator circuit. Wheel brake pressure amplification.-If the wheel speed voltage is higher than the condenser 107 discharge voltage, transistors 115, 111 and 123 conduct and a solenoid 86 of valve 80 is energized thereby attracting a plunger 88 leftwardly. A valve disc 89 thereupon separates from a seat 92 and contacts a seat 95 allowing air to pass through port 94, filter 93, port 85, conduit 84 and port 83 to chamber 40 of intensifier 32. A pressure differential across a diaphragm 38 is thereby established causing a plunger 42 rigid therewith to move leftwardly. A piston 45 is moved in the same direction to increase the pressure fed to wheel cylinder 54. Wheel brake pressure release.-When the wheel speed signal from generator 100 becomes significantly lower than that from condenser 107, transistors 116 and 125 become conductive thereby causing a solenoid 64 of valve 60 to be energized. A plunger 66 then moves leftwardly separating a valve disc 69 from a seat 70 and contacting it with seat 73. Air then passes through port 72, filter 71, port 62, conduit 59 and port 58 into the chamber 22 of pressure reducer 16 causing an air pressure differential across diaphragm 20. A valve ball 27 and plunger 33 are shifted leftwardly first to seat ball 27 at 36, thereby separating the master cylinder and wheel cylinder, whereafter plunger 33 moves further leftwardly to increase the volume of liquid in a chamber 29.