Patent ID: 8235406

Claim:
A damper unit, comprising: a cylinder, connected to a reservoir, in which a hydraulic fluid is sealed; a piston dividing an interior of the cylinder into two chambers, the two chambers configured to pass the hydraulic fluid from one to the other so as to damp vibration from an outside; a piston rod which is connected to the piston at one end, while being caused to extend outwards of the cylinder at the other end and in which a hollow recess portion is provided in an axial direction; an inner sleeve which exhibits a cylindrical shape and which is adapted to be accommodated rotatably within the hollow recess portion in the piston rod; a pump rod which is provided at an axial end portion of an inner circumferential surface of the cylinder at one end, while being inserted into an interior of the inner sleeve from a distal end side at the other end and in an interior of which a passage is provided; a pump unit configured to perform pumping for generating a force with which the piston is pushed out of the cylinder or the piston is drawn into the cylinder by moving the hydraulic fluid in the inner sleeve and the pump rod by a change in relative position between the inner sleeve and the pump rod which is triggered in association with a stroke of the piston rod; a hydraulic fluid releasing unit configured to release the hydraulic fluid within the inner sleeve and the pump rod to the reservoir or the two chambers when the piston reaches a predetermined position relative to the cylinder within a sliding range thereof by pumping of the pump unit; and a control unit configured to control the predetermined position where the hydraulic fluid is released by the hydraulic fluid releasing unit.