| 摘要 |
PURPOSE:To improve neutral stability by opening up a control passage to a tank line and connecting a selecting means to a command means via a function circuit having a dead zone when a proportional solenoid is not electrified. CONSTITUTION:A pair of proportional solenoids 21, 22 are provided on a proportional control valve 20 and, when the proportional solenoids 21, 22 are not electrified, control passages 26, 27 are opened up to a tank line 28, 29, while a selecting means 35 which selectively inputs to one of the proportional solenoid 21, 22, is connected to a command means 31 via a function circuit 36 having a dead zone. Thereby, even if there is a displacement due to, e.g., vibration, etc. in the neutral operation position N of the command means 31, the neutral position of a variable control element 1 can be securely maintained, thereby, improving neutral stability.
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