| 摘要 |
A vehicle braking system for a vehicle has primary and secondary braking circuits. The primary braking circuit has a vehicle brake pedal (12), a transducer (F, R) connected to the brake pedal, which generates braking demand signals in response to depression of the brake pedals (12). An electronic control unit (10, 18) receives the braking demand signals from the pedals (12). A first inlet solenoid valve (22) has an inlet connected to a primary source of braking pressure (S1) and an outlet connected to a load (32, 40), and is movable from a closed position to an open position by an output braking signal from the electronic control unit (10, 18), thereby connecting the primary source of braking pressure (S1) to the load (32, 40). An exhaust solenoid valve (24, 24') has an inlet in communication with the load (32, 40) and an outlet connected to atmosphere. The exhaust solenoid valve (24 24') is controllable by an output braking signal from the electronic control unit (10, 18), thereby releasing the braking pressure from the load (32, 40). The secondary braking circuit has a secondary source of braking pressure (S2), e.g. a pneumatic signal generated by a pressure modulated by a valve (12a) controlled by depression of the brake pedal (12). A second inlet solenoid valve (26, 34) is located between the second source of braking pressure (S2) and the load (32, 40), and is movable during normal braking by an output signal from the electronic control unit (10) which indicates correct operation of the electronic control unit, to a primary braking position in which the secondary source of braking pressure (S2) is isolated from the load (32, 40) and the first inlet solenoid valve (22) and the exhaust solenoid valve (24, 24') are connected to the load, from a secondary braking position in which the secondary source of braking pressure (S2) is connected to the load (32, 40). |
