| 摘要 |
PURPOSE:To enable a spring brake to be operated even when a hydraulic brake system fails by switching and controlling a valve installed between an air tank and the spring brake by means of the detected signal of the excessive displacement of the output member of a booster in case of said failure in the hydraulic brake system. CONSTITUTION:Should an oil pipe 10 be cut off, the output member of a booster 8 is excessively displaced when a brake pedal 4 is stepped on, turning on a stroke switch 16. Thereby the solenoid of a valve unit 17, which is installed between an air tank 2 and a spring brake 19, is excited causing a valve body 22 to be lifted. Due to this lifting motion, the hole 24f of the valve unit 17, which is connected to the spring brake 19, is isolated from the hole 24g which is connected to the tank 2, while it is connected simultaneously to the hole 23c of an exhaust valve 23. Thereby when the supply of air to the spring brake 19 is stopped, at the same time, the air is discharged from the brake 19 to the atmosphere allowing the brake 19 to operate. |
