Patent ID: 7987668

Claim:
A fluid pressure actuator comprising: an output cylinder including a first output cylinder chamber, a second output cylinder chamber and an output piston arranged between said first output cylinder chamber and said second output cylinder chamber; a fluid pressure pump including a first supply and discharge port, a second supply and discharge port and a swash plate for changing displacement of said fluid pressure pump; an electric motor configured to drive said fluid pressure pump; a first output cylinder passage connecting said first output cylinder chamber and said first supply and discharge port; a second output cylinder passage connecting said second output cylinder chamber and said second supply and discharge port; a return passage connected to an accumulator for accumulating working fluid leaked from said fluid pressure pump; a swash plate control cylinder configured to be supplied with working fluid from one passage of said first output cylinder passage and said second output cylinder passage having higher pressure than another passage, to drive said swash plate and to discharge working fluid to said return passage; a swash plate control passage; a shuttle valve configured to supply working fluid from said one passage to said swash plate control passage; and a servo valve configured to have a first state and a second state, wherein said swash plate control cylinder includes a first swash plate control cylinder chamber, a second swash plate control cylinder chamber and a swash plate control piston arranged between said first swash plate control cylinder chamber and said second swash plate control cylinder chamber, said swash plate control piston is connected to said swash plate, when said servo valve has said first state, said servo valve connects said swash plate control passage and said first swash plate control cylinder chamber and connects said return passage and said second swash plate control cylinder chamber, and when said servo valve has said second state, said servo valve connects said swash plate control passage and said second swash plate control cylinder chamber and connects said return passage and said first swash plate control cylinder chamber.