PURPOSE: To selectively and precisely adjust the height of a seat as a person is seated by detecting the holding pressure of a cylinder for a weight on a seat side and controlling an electromagnetic-proportion depressurizing valve to correct the height of the seat to an optimum value in accordance with the detection result and a target value.
CONSTITUTION: A rod 2 which has an accumulator and a depressurizing valve inside is elevated up and down by supplying and discharging operating oil into/from a cylinder 3. At this time, the rod 2 is extended and shrinked by the operation of an electromagnetic-proportion depressurizing valve, corresponding to outer force. Operating oil is supplied and discharged by an oil supplying/discharging device 9 to/from the cylinder 3 through the electromagnetic-proportion depressurizing valve which can be switched by an up-switch and a down-switch 7 above a seat 1. In addition, the displacement of the rod 2 is detected by a displacement sensor 6 to obtain the positional height of the seat 1 at the end of the rod 2. The holding pressure of the cylinder 3 for a weight on the seat 1 side is detected corresponding to the output of the displacement sensor 6 and the electromagnetic-proportion depressurizing valve is controlled by a control circuit 8 to correct the height of the seat 1 to an optimum value in accordance with the detection result and a target value.
HANAWA NOBUMICHI
YOSHIDA KENJI
