Valve arrangement for controlling the brake pressure in a vehicle

Abstract

The invention provides a valve arrangement for controlling the brake pressure in a hydraulic power-brake system. By actuating a brake valve, a brake pressure proportional to the actuation force builds up in an outlet pressure chamber, with a first ball-seat valve. By displacing an actuation piston from its normal open position in which the outlet pressure chamber is connected to a relief chamber which is continuously kept free of pressure, the first ball-seat valve can be adjusted into a blocking position. After the first ball-seat valve has closed, further axial displacement of the actuation piston, (out of its normal blocking position, in which an inlet pressure chamber which is subjected to the high outlet pressure of a pressure accumulator is blocked off with respect to the outlet pressure chamber) moves a second ball-seat valve into its open position. The latter ball-seat valve, however, again assumes its blocking position as an equilibrium position which corresponds to equality between the actuation force and a reaction force resulting from the application of pressure to a piston face of a control piston, which is subjected to the outlet pressure. The pressure-medium flow path, which can be cleared by opening the second ball-seat valve, is provided with a restrictor which limits the maximum rate of increase of the brake-pressure.