JPS6430865A - Control device for brake pressure - Google Patents

Abstract

PURPOSE:To prevent the lack of braking force at the time of the failure of a load sensor, a motor, or a front-wheel brake system by providing a valve opening solenoid valve for a movable plunger which oppositely receives front and rear wheel brake device side pressures in a part between the inlet and outlet of a pressure control valve device. CONSTITUTION:At the time of the failure of a pulse motor 10 or a load sensor 23, a controller 11 feeds a signal to the magnetic coil 92 of a bypass valve device 90. Thereupon, a plunger 68 is moved upward making a valve ball 76 seated on a fixed plunger 77 while simultaneously separating a valve ball 69 from the center hole of a member 65, to connect connecting ports 63 and 64. Hence, the pressure of the other fluid pressure generating chamber of a master cylinder 1 is fed directly to the wheel cylinders of rear wheels 9a, 9b. Then, at the time of the failure of the brake system of front wheels 5a, 5b, the fluid pressure applied to the top end of the plunger 68 through the plunger 77 becomes zero. Therefore, even without exciting the plunger 68, the pressure of the other chamber of the cylinder 1 is applied to the bottom end of the plunger 68 moving it upward, and the valve ball 76 is seated to a through passage while separating the valve ball 69 from the member 65 to connect the connecting ports 63 and 64.