Damper and vibration damping structure using the same

A damper comprising:

• at least a hollow outer elongated body and a hollow inner elongated body,
• said hollow outer elongated body having a hollow portion defined by an axially extending inner surface thereof,
• said hollow inner elongated body including an inserted portion which has an outer surface extending in an axial direction and is disposed in said hollow portion of said hollow outer elongated body with a gap on said outer surface thereof with respect to said axially extending inner surface of said hollow outer elongated body, and which is inserted in said hollow portion of said hollow outer elongated body so as to be relatively movable in the axial direction, and an axial end portion which integrally extends from said inserted portion in the axial direction and projects to the outside from one axial end portion of said hollow outer elongated body,
• a liquid viscous body or a liquid viscoelastic body being disposed in the gap between the axially extending inner surface of said hollow outer elongated body and the outer surface of said inserted portion of said hollow inner elongated body in such a manner as to be in contact with the axially extending inner surface and the outer surface,
• a first attaching structure being provided on another axial end portion of said hollow outer elongated body, and a second attaching structure being provided on the axial end portion of said hollow inner elongated body, and
• a controller to control an increase or decrease of the internal pressure of the liquid viscous body or the liquid viscoelastic body due to the extension or retraction of said inserted portion of said hollow inner elongated body in the axial direction with respect to said hollow portion of said hollow outer elongated body.