| 摘要 |
PROBLEM TO BE SOLVED: To carry out operation even if a mode selector valve is locked in the midway of switching a mode by constructing the mode selector valve to be switched to one of supply and discharge modes when a valve element is located at the stroke end on one side, and to be switched to a by-path mode when the valve element is located at the stroke end on the other side. SOLUTION: This mode selector valve 33 is adapted to communicate actuator side ports 33f, 33g connected to oil chambers 13, 14 with each other when a valve element 33 is located at the most end position of the other side in the moving direction, and by-pass control valves 31, 32 to connect the oil chambers 13, 14 with an oil passage 28. When a valve element 33j is located at the stroke end on one side, the selector valve is switched to one of supply of discharge mode positions, for example, to a mechanical mode position, and when the valve element 33j is located at the stroke end on the other side, it is switched to the by-path mode. Thus, at the time of mode switching between FBW mode and the mechanical mode, the selector valve is prevented from entering the by-path mode due to locking of the valve element 33j or the like.
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