| 摘要 |
A hydraulic braking system, particularly for motor vehicles equipped with anti-skid devices, includes a housing having at least one chamber accommodating a pressure control unit controlling the pressure of hydraulic fluid admitted into brake circuits leading to respective brake-operating cylinders. The pressure control unit includes an actuating piston which subdivides the chamber into an actuating compartment, a working compartment, a supply compartment therebetween which is sealed from the actuating compartment and communicates with the working compartment through a gap between the piston and the housing, and another compartment at the end of the piston remote from the working compartment. An auxiliary piston is accommodated in the last-mentioned compartment and subdivides the same into two spaces into one of which the auxiliary pressure is admitted at the same time that it is admitted into the supply compartment. A sealing ring extends across the gap and permits flow from the supply into the working compartment but not in the opposite direction. The piston has a passage through which the hydraulic fluid can flow between the working compartment and the other space which is connected to a reservoir, unless a valve member engages a seat surrounding the end of the passage that opens into the working compartment. The valve member carries a tappet extending through the passage and through a house in the auxiliary piston to abut an end wall of the housing. When the auxiliary source fails, the pressure in the actuating compartment compresses the fluid in the working compartment so that braking action is still assured. Two pressure-control units can be used side-by-side for separate operation of two brake circuits. |
