| 摘要 |
According to progress of a vehicle, a pump is actuated to feed fluid into a brake pipe. The discharge of the pump is generally proportioned to vehicle speed. On the other hand, the fluid within the brake pipe is relieved to an upper stream side of the pump at a predetermined flow rate regulated by an orifice. Accordingly, when the flow rate of the fluid fed by the pump is less than the predetermined flow rate, in other words, when the vehicle speed is less than the predetermined speed, pressure within the brake pipe is not increased. However, when the discharge of the pump exceeds the predetermined flow rate, the pressure within the brake pipe is increased. Due to this increased pressure, a vehicle wheel braking device is actuated to brake the wheels. Thus, vehicle speed is lowered. Since the pump discharges fluid in one direction or the other direction according to forward and backward movement of the vehicle, the pump can be functioned as a reverse speed restricting device when the vehicle moves backwardly and as a vehicle speed sensor for vehicle speed responsive control devices when the vehicle moves forwardly.
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