| 摘要 |
A vehicle brake system includes a brake pedal unit coupled to a vehicle brake pedal. The system includes an input piston connected to operate a pedal simulator during a normal braking mode, and coupled to actuate a pair of output pistons during a manual push through mode. The output pistons are operable to generate brake actuating pressure at first and second outputs of the brake pedal unit. A hydraulic pressure source supplies fluid at a controlled boost pressure. A hydraulic control unit is adapted to be hydraulically connected to the brake pedal unit and the hydraulic pressure source. The hydraulic control unit includes a slip control valve arrangement, and a switching base brake valve arrangement for switching the brake system between the normal braking mode wherein boost pressure from the pressure source is supplied to first and second vehicle brakes, and the manual push through mode wherein brake actuating pressure from the brake pedal unit is supplied to the first and second vehicle brakes. The input piston cooperates with a seal mounted in the brake pedal unit to provide for a progressive rate of friction therebetween as the input piston is advanced in the brake pedal unit by the brake pedal.
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