To eliminate a starting shock when a moving-down motion starts without using an expensive valve such as a three-position changing valve or a solenoid proportional control valve.
This circuit has a sub-control valve Vh for connecting and disconnecting a supply and discharge hydraulic passage 33 which connects a control valve Vu for moving up and a control valve Vd for moving down which are connected in parallel and are of two-position changing type to a single motion type moving up-and-down cylinder 10 and has a gradual opening control means for opening the sub-control valve Vh in response to the opening of the control valve Vd for moving down and gradually increasing the valve opening of the sub-control valve Vh. The sub-control valve Vh is constituted by a checking poppet valve 21 and a sub-operation solenoid valve 28 of ON-OFF type for switching the poppet valve 21 at two positions, a closing position of disconnecting the supply and discharge hydraulic passage 33 and an opening position of connecting it and the gradual opening control means is constituted by controlling the duty ratio of a pulse current to the sub-operation valve 28.
| JP7130602 | harvester |
SOEJIMA KIJU
HATTORI AKIO
KUBOTA SEIKI KK