| 摘要 |
PURPOSE:To forcibly reset a valve when the valve continues operating even though a neutrality signal is generated, by providing a position sensor for a control valve controlled by a microcomputer. CONSTITUTION:The control valve is operated by a solenoid 22, and has such a construction that ports A, B communicated to a power cylinder, a port P communicated to a pump and a port T communicated to a tank are changed over in accordance with the position of a spool 21. The spool 21 is provided with the valve position sensor 35 and is connected with a solenoid valves 31, 32 through logical circuits 38-40. When the spool 21 is deviated from a neutral position even though the neutrality signal is generated, the solenoid valve is opened to supply a hydraulic oil into a spring chamber 26 or 27, thereby forcibly resetting the spool 21. Accordingly, even when the valve is erroneously operated due to the presence of dusts or the like, the danger of continuing the operation of the power cylinder can be prevented. |
