The present invention enables a simple structure to provide an easy adjustment of damping torque to be caused by applied rotation.
The rotary damper (1) is intend to limit movement of viscous fluid filled in a circular cylindrical chamber (111), thereby generating a damping torque in response to an applied rotational force. The lid (15) is the screw-on type capable of being screwed into the casing (11), and thus adjusting a clearance gap G1 between the lid (15) and each partition (115) by way of changing the screwing amount of the lid (15) into the casing (11) allows amount of viscous fluid moving through the clearance gap G1 to be adjusted, thereby resulting in adjustment of a damping torque to be caused by rotation. In addition, each axial force generation member (17) includes a plastically or elastically deformable element and is located between the lid (15) and the corresponding partition (115) to apply a reaction force to the lid (15). This causes screwing the lid (15) into the casing (11) to generate an axial force, thereby preventing external-leakage of the viscous fluid via a threaded interface between the lid (15) and the casing (11), and allows the leeway for the adjustment of the clearance gap G1 to increase.