To provide a hydraulic actuator capable of controlling a position of a driven part by one servo valve.
This hydraulic actuator comprises a piston body 50 having a piston head 51 stored slidably in a hydraulic cylinder 10 in a non-contact condition through a hydrostatic bearing, a passage part 12 for supplying fluid having fixed pressure P into a pressure chamber on one side having the piston head arranged between both pressure chambers in the hydraulic cylinder and controlling and supplying pressure P1 of fluid through a servo valve into the pressure chamber on the other side, a first pressure sensor 15 and a second pressure sensor 16 for detecting pressure of the pressure chamber on one side and the pressure chamber on the other side, and a position sensor 41 for detecting a position of the piston body. There is difference between pressure receive area S of the piston head in the pressure chamber on one side and pressure receive area S1 of the piston head in the pressure chamber on the other side. A controller 1 receives each detection signal from the second pressure sensor and the position sensor as feedback value to control a position of the piston body.
SAKAKI KAZUTOSHI
HARA TOSHIFUMI
Kenho Ikeda
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