GB1308502A - Vehicle braking system - Google Patents

Abstract

1308502 Aritiskid braking systems KELSEYHAYES CO 13 July 1970 [5 Sept 1969] 33964/70 Heading F2F In a vehicle hydraulic braking system a varying output signal is generated in response to the occurrence of a skid condition which is fed to a control circuit generating pulses the width of which vary with the magnitude of the output signal to vary the braking pressure. The hydraulic fluid is controlled by a control device to an inlet 18 of which the fluid is fed before passing through a cylinder 60, past check valve 76, grooves 92 and bore 90 of a cylinder 82, and groove 88 of a control piston 46 to an outlet 16. Piston 46 controlling check valve 76 is operated by a vacuum suspended diaphragm 42, Fig. 5 (not shown), which is operated by the admission of air to one side (50), under the control of a solenoid 48, operated valve arrangement. When the solenoid is actuated by the control circuit a plunger 228 moves a cap 156 of the valve arrangement into a cylinder (144), Fig. 5 (not shown), to engage a sealing washer 164 thereby closing a radial path 178 communicating with vacuum by way of a line (52). At the same time a space is formed between a seal 160 and washer 146 and air passes through voids between projections 182, 186 and through path 190 to act on the diaphragm (42). Air pressure acting on a flexible sealing flange 188 causes it to be deflected into engagement with a counterbore 159 closing a second path 174 to vacuum. As the diaphragm (42) moves leftwardly the piston 46 disengages a shoulder 86 and valve 76 moves under the bias of a spring 84 so that groove 92 is effectively within the bore 82 and pressure to the brake cannot increase. By rapidly actuating and deactuating solenoid 48 the diaphragm assembly (42) is maintained at a preselected position at which the brake pressure is at a desired magnitude. The control circuit, Fig. 2 (not shown) achieving this comprises D.C. converters (300) receiving signals picked up from wheel sensors (28) on each wheel, the output of the converters being fed to a summing circuit (302) and then to a differentiator. The differentiator output passes to a threshold circuit (308) feeding a signal to a summing network (316) and also to a triangle wave generator, 312 the output of which is also fed to the summing network. The summing network passes a signal to a valve driver circuit 324 controlling solenoid 48. In the embodiment shown the rear wheel brakes only are controlled but the front, or front and rear may also be controlled.