| 摘要 |
PURPOSE:To make the frequency of lockup of a serivce brake as low as possible, by preventing the lockup of the service brake under the operation of a parking brake as long as no lockup instruction is applied for the service brake. CONSTITUTION:Even if a parking brake is operated and a sensor switch 10 is closed during the closure of a main switch 9, a solenoid 7a is not energized and a solenoid shutoff valve 7 for a service brake is not operated as long as a lockup instruction switch 11 is open. However, once the lockup instruction switch 11 is closed during the closure of the sensor switch 10, a coil 12a is energized to close a contact 12b to energize the solenoid 7a and a coil 13a so that the service brake is locked up, the contact 13b of a relay switch 13 is closed and a self- holding circuit Ch is closed. As a result, the valve 7 is kept in operation even if the switch 11 is opened. The locked-up service brake is unlocked only by releasing the parking brake. |
