| 摘要 |
PROBLEM TO BE SOLVED: To prevent impact to the crew and collision from behind by a succeeding vehicle by actuating a fail safe valve and feeding the control chamber of a booster with engine negative pressure when the relation between a target control output value based on a control signal to a negative changeover valve and an atmospheric pressure changeover valve and a detected value of control pressure has exceeded a specific range. SOLUTION: A first inlet port of the fail safe valve 30 is connected to a negative pressure pipe 6 and a second inlet port in connected to a control pipe line 51 from a negative pressure changeover valve 4 and an atmospheric pressure changeover 5. The fail safe valve 30 is connected to a control chamber 13 of the booster 100 through a control pipe line 41. A controller 42 outputs an actuation signal to the fail safe valve 30 when the detected pressure of a pressure sensor 35 on the control pipe line 51 is outside of a control maintaining range. An outlet port to the control pipe line 41 and the first inlet port from the negative pressure pipe 6 are connected together and from the second inlet port to the outlet port is blocked. Thus engine negative pressure in induced into the control chamber 13, slow speed down reducing operation is released and the vehicle is restored to a normal braking. |
