| 摘要 |
A master cylinder assembly for a vehicle braking system having two pressure circuits, comprises a master cylinder having two separate pressure chambers associated with respective pistons one chamber being arranged for connection to one of the pressure circuits, generally the circuit to the front wheel brakes, and a control valve arrangement fast with the master cylinder. The control valve arrangement has an inlet for connection to the other of the chambers and an outlet for connection to the other of the pressure circuits, usually the rear wheel brake circuit, a normally-open valve for controlling communication between the inlet and the outlet, and an auxiliary piston assembly movable to open and close the valve to control the pressure applied to the rear wheel brakes as compared to full braking pressure applied to the front wheel brakes. The auxiliary piston assembly has two portions, one portion being subjected to the outlet pressure of the valve arrangement, and the other portion being subjected to the pressure of the chamber of the master cylinder and being engageable by the adjacent piston of the master cylinder, in the event of failure of pressure in said one pressure circuit, to move the piston to a position in which the valve is held open so that full braking pressure is applied to the rear wheel brakes. |
