GB1283908A - Pressure proportioning valve assembly for hydraulic brake systems - Google Patents

Abstract

1283908 Hydraulic systems; modulating valves; differential braking; valves MIDLANDROSS CORP 27 Oct 1970 [6 Nov 1969 15 July 1970] 51069/70 Headings F2F and F2V A proportioning valve assembly 10 is interposed between a master cylinder 12 and the rear wheel cylinders 24, 26 of an automobile dual hydraulic braking system and is actuable to establish a pressure differential between the rear wheel cylinders 24, 26 and the front wheel cylinders 18, 20 in the higher range of pressure applied by the master cylinder 12 and to increase the pressure differential at a linear rate as the master cylinder pressure increases in such higher range. The valve 10 comprises an inlet port 34 and an outlet port 40 and fluid flow therebetween is controlled by an annular valve element 50 having a passageway 111 therethrough and an annular seat 115, and a piston 48 with a lip postion 98, the piston 48 being movable against the action of a coil spring 124 to cause engagement of lip portion 98 with the seat 115 and thereby cut off communication between the inlet port 34 and the outlet port 40. When the brake pedal 14 is initially operated identical pressure is applied at the front cylinders 18, 20 and the rear cylinders 24, 26. The communication of the master cylinder 12 to the rear cylinders 24, 26 through the assembly 10 comprises a passageway 60, a portion 58 of a stepped bore 32 in the valve body 30, a passageway defined between a central portion 82 of the piston 48 and the wall of the passageway 111 through the valve element 50, a reduced diameter portion 52 of the stepped bore 32, and passageways 96 and 54 to the outlet port 40. The passage ways 96 are formed between angularly spaced projections 94 on a head portion 92 of the piston 48; the central portion 82 of the piston 48 has flat sides (84, 86) joined by arcuate surfaces (88, 90) and the piston 48 also includes a radially extending flange portion 100 having flat sides (102, 104) coplanar with flat sides (84, 86) and arcuate surfaces (106, 108) concentric with but greater in diameter than surfaces (88, 90), Fig. 3 (not shown). As increasing force is applied to the brake pedal 14 a point will be reached where the pressure in the stepped bore 32 moves the piston 48 downwardly against the bias of the spring 124. When the tip portion 98 comes into engagement with the sealing surface 115 communication between the inlet port 34 and the outlet port 40 is interrupted. Increased master cylinder pressure acting on the piston 48 will now cause communication to be reinstated. In this way the lip portion 98 opens and closes against the sealing surfaces 115, thereby modulating the pressure at the outlet port 40 so that the pressure at the outlet port 40 increases at a lower rate than the pressure applied by the master cylinder 12.