US Patent 9371675 Rotary damper and hinge device with damper

A rotary damper has a damper body having a receiving portion, and a rotor rotatably disposed in the receiving portion of the damper body. A space between an inner circumferential surface of the receiving portion and an outer circumferential surface of the rotor is divided into a plurality of pressure chambers. A rotation speed of the rotor is controlled to be at a low speed by a flow resistance of fluid filled in each of the pressure chambers when the fluid flows through gaps between an inner surface of the receiving portion and an outer surface of the rotor opposed to each other in a direction of a rotation axis of the rotor. The damper body and the rotor are relatively movable in the direction of the rotation axis of the rotor.