GB1421703A - Hydraulic pressure modulatorp - Google Patents

Abstract

1421703 Pressure modulating valves SOC ANON DBA 4 March 1974 [3 April 1973] 9630/74 Headings F2F and F2V An hydraulic pressure modulator for an antiskid brake circuit comprises a housing 20 provided with a fluid duet 22 having an inlet orifice 23 and an outlet orifice 25 adapted to be connected to a source of variable brake pressure, e.g. a master cylinder 10, and a set of brake actuators 14 respectively, a non-return valve 24 in the duct allowing fluid to flow from the outlet orifice towards the inlet orifice, a control plunger 36 slidable in a bore 32 so as to define therein a modulation chamber 46, and a passage 48 connecting the chamber with the inlet port downstream of the valve 24. The latter is controlled by the plunger so that the plunger is capable of modulating the fluid pressure in the modulation chamber as a function of a variable control force transmitted by a differential driving piston 34 in the stepped bore 32 in which it defines a compression chamber 42 adjacent to that end face of the piston having the larger effective area and a decompression chamber 44 adjacent that end face of the piston having the smaller effective area. A work valve 56 is actuated by the plunger for controlling the fluid flow through the passage 48 the effective area B of the work valve seat being less than the effective area A of the plunger. When the latter has left its idle position and is submitted to the pressure prevailing in the modulation chamber 46. Prestressed resilient means, i.e. springs 50, 52, act on the differential piston for biasing the plunger toward the said idle position in which the work valve is closed and the non-return valve 24 is open. As shown, the one-piece member 30 forming the piston 34 and plunger 36 contains a leakage duct 60, which has mounted therein a calibrated valve 62 allowing fluid to flow only from the chamber 46 to the chamber 44. The valve 18 is operated by an hydraulic assisting circuit comprising a pump 64 connected by a non-return valve 66 to a pressure fluid accumulator 68 which is connected to the decompression chamber 44 via an orifice 70 and to the compression chamber 42 via an orifice 72 and an antiskid valve 74, the latter orifice being also connected to a low-pressure fluid reservoir 78 via an anti-skid valve 76. The valves 74, 76 represent a system of anti-skid solenoid valves operated by signals generated by an anti-skid control device which responds to signals generated by speed sensors and representing the angular motion of at least one wheel 16 of the vehicle.