Rotary damper

A rotary damper for limiting a movement of a viscous fluid to generate a damping torque in reaction to a rotating force applied, the rotary damper comprising:

• a casing having an opening end on one side and including a circular cylindrical chamber defined inside, the circular cylindrical chamber being filled by the viscous fluid;
• a rotor being placed in the circular cylindrical chamber and being rotatable relative to the circular cylindrical chamber;
• and
• a lid attached to the opening end of the casing and keeping the rotor together with the viscous fluid sealed inside the circular cylindrical chamber;
• the rotor comprising:
• a rotor body in cylindrical shape;
• and
• a vane projecting radially outward from an outer circumferential surface of the rotor body and placing a front end surface of the vane close to a sidewall surface inside the circular cylindrical chamber to partition an inside of the circular cylindrical chamber;
• the casing comprising:
• a partition projecting radially inward from the sidewall surface inside the circular cylindrical chamber and placing a front end surface of the partition close to the outer circumferential surface of the rotor body to partition the inside of the circular cylindrical chamber;
• and
• a first threaded portion formed on the opening end of the casing;
• the lid comprising a second threaded portion formed on the lid and engaged with the first threaded portion formed on the opening end of the casing;
• and
• the rotary damper further comprising an axial force generation member, the axial force generation member including a plastically or elastically deformable element and being located between a back face of the lid and a facing surface of the partition to the back face of the lid so that screwing the second threaded portion of the lid onto the first threaded portion of the casing causes the axial force generation member to generate an axial force;
• wherein a clearance gap adjustable by way of adjustment of a screwing amount of the second threaded portion of the lid onto the first threaded portion of the casing is defined between the back face of the lid and the facing surface of the vane to the back face of the lid to act as a flow passage for limiting the movement of the viscous fluid.