Hydraulic actuator and joint driving unit employing the same

A rotatable hydraulic actuator comprising:

• a base member;
• a swash member which is held with respect to the base member through a universal joint mechanism and is configured to be capable of rocking with respect to a first axis including a joint center of the universal joint mechanism being based on the base member;
• a first rotational member which is held rotatably with respect to the swash member about a second axis including the joint center of the universal joint mechanism being based on the swash member;
• a second rotational member which is held rotatably with respect to the first rotational member about a third axis being perpendicular to the second axis and including the joint center of the universal joint mechanism and is held rotatably about the first axis with respect to the base member;
• a high-pressure pipe portion filled with a non-compressible fluid being pressurized by a pressure accumulation mechanism;
• a low-pressure pipe portion filled with the non-compressible fluid while being maintained at a pressure lower than that of the non-compressible fluid in the high-pressure pipe portion;
• a pump mechanism which transfers the non-compressible fluid in the low-pressure pipe portion to the high-pressure pipe portion;
• a plurality of rocking-torque generation mechanisms which couple the base member and the swash member to each other and are driven by the non-compressible fluid to generate a rocking torque to the swash member, with the rocking-torque generation mechanisms being connected to the high-pressure pipe portion, the low-pressure pipe portion, and the pump mechanism;
• a control valve device which controls connection of the non-compressible fluid between the rocking-torque generation mechanisms and the high-pressure pipe portion as well as the low-pressure pipe portion;
• and
• a rocking-angle adjustment unit configured to change a relative angle between the first rotational member and the second rotational member about the third axis;
• wherein the control valve device controls such that the rocking-torque generation mechanisms generate the rocking torque about a fourth axis perpendicular to the first axis and the third axis, with respect to the swash member.