| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem of causing shock by the upper and lower vibration of a working part when a tractor or the like is suddenly started or stopped in the travel or the like among fields because a gap in some degree is formed in a link structure although the working part is connected through the link structure to the tractor or the like and has a structure of lifting and lowering the working part by the operation of a hydraulic cylinder. SOLUTION: A sensor for detecting the height of a working part, and a control valve 5 for closing and opening a pressurized oil in a hydraulic cylinder 3, installed in a hydraulic circuit are installed in a tractor or the like capable of lifting and lowering ths working part by the operation of the hydraulic cylinder 3. When the working part is lifted and held, and the stopping condition of the vehicle such as the stepping on of a right or left braking pedal is detected, the pressurized oil in the hydraulic cylinder 3 is temporarily switched from a sealed state to an opened state to reduce the shock transmitted from the cylinder 3.
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