| 摘要 |
In a brake system including a master cylinder (11) and an electrically-driven hydraulic pressure generator (23) with front and rear pistons (38B,38A), when the hydraulic pressure generator (23) cannot be operated and a failure of a first hydraulic system (Pa,Pc) linked to a rear fluid chamber (39A) of the generator (23) occurs and makes a first hydraulic system (Pa,Pc) open to the atmosphere, the brake-fluid pressure of a second hydraulic system (Qa,Qc) transmitted from the master cylinder (11) to a wheel cylinder (20,21) via a front fluid chamber (39B) of the generator (23) is used to perform braking. A forward-facing third front cup seal (C5) provided at an intermediate portion of the front piston (38B) prevents the brake-fluid pressure generated by the master cylinder (11) from leaking out from a front supply port (49B) via the rear fluid chamber (39A). At the same time, a stopper (51) prevents the pressure of the front fluid chamber (39B) from moving the front piston (38B) excessively backward. The braking is accordingly secured by use of the second hydraulic system (Qa,Qc) linked to the front fluid chamber (39B) of the hydraulic pressure generator (23).
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