BRAKING FORCE HOLDING DEVICE FOR AN AIR BRAKE SYSTEM

摘要

A braking force holding device for an air brake system, maintains a braking force when a vehicle is stopped facing upwardly on a hill to facilitate the start of the vehicle on the hill. The braking force holding device includes a main body having an inlet port connected to a brake valve, an outlet port connected to a pneumatic relay valve, a control port connected to the pneumatic actuator of a clutch operating device, and a passage interconnecting the inlet port and the outlet port; a valve device capable of intercepting the flow of air from the outlet port toward the inlet port; and a control unit for controlling the valve device. The control unit has a movable member capable of being shifted to a first position to open the valve device or to a second position to close the valve device depending on the difference between a force corresponding to the pressure of compressed air applied thereto through the control port and a force corresponding to the pressure of compressed air applied thereto through the outlet port. The timing of relieving the braking pressure maintained is varied according to the level of the braking pressure.