| 摘要 |
PROBLEM TO BE SOLVED: To reduce deposit of foreign matter between a spool and a body for positive switching in the electromagnetic direction by electrically-driving a spool constantly in both the normal and reverse directions within a range less than the switching stroke and at a prescribed frequency and waveform while a pair of electromagnetic actuators facing each other are on standby. SOLUTION: During a standby time except for driving of electromagnetic actuators 10A, 10B, a spool 2 is electrically-driven constantly in the normal and reverse directions within a range less than the switching stroke, so that its position is switched frequently. Thus, a spool 2 can be reciprocated without switching an electromagnetic direction switching valve and foreign matter deposited between the spool 2 and the spool opening 1a of a body 1 can be raked out outside a sealed part, so that the lock of the spool can be prevented effectively. The possible abnormal abrasion of the spool and the body is prevented by setting a prescribed frequency at 0.5 to 10 Hz, so that they can be used for a long time. It is possible to attain stable circuit switching operation by making a prescribed waveform into a square wave.
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