| 摘要 |
A pre-engagement unit for a braking pressure modulator for a pressure regulating circuit of an electronic braking system includes a first pneumatic inlet through which a supply pressure is supplied to the pre-engagement unit, a second pneumatic inlet through which a redundancy pressure is supplied to the pre-engagement unit, a first pneumatic output terminal through which the pre-engagement unit is connected to an air quantity augmenting relay valve, a second pneumatic output terminal through which the pre-engagement unit is connected to a pressure sink, and an electrically actuated valve system. The electrically actuated valve system has three substantially identical 2/2-way solenoid valves. Each of the 2/2-way solenoid valves includes first and second pneumatic terminals, and an electric terminal which is connected to an electronic control unit of the electronic braking system for selective actuation of the 2/2-way solenoid valves. The first and second terminals of the 2/2-way solenoid valves are selectively connected to the pneumatic inlets and output terminals of the pre-engagement unit and to each other so that the first 2/2-way valves serves as an air admission valve for supply pressure to the pressure regulating circuit, the second 2/2-way solenoid valve serves as an air admission/exhaust valve for redundancy pressure to the pressure regulating circuit, and the third 2/2-way solenoid valve serves as an exhaust valve for the pressure regulating circuit. Thereby, the pressure in the pressure regulating circuit can be increased, decreased, or maintained. Desirably, the first, second, and third 2/2-way solenoid valves are connected in parallel to each other.
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