Patent ID: 8096393

Claim:
A breakdown preventive mechanism of a rotary damper having a small force against a rotary motion in one direction, and generating a damping force against a rotary motion in another direction, and said breakdown preventive mechanism preventing from breaking down when a load of high torque is generated, comprising: an upper housing, an upper rotor freely rotating within the upper housing, having a first pressure transmission hole in a lower part of the upper rotor, and being forced downward, a lower housing mounted in the upper housing, and having a viscous fluid sealed between the lower housing and the lower part of the upper rotor, a lower rotor freely coupled in the lower housing along rotation of the upper rotor, and having a second pressure transmission hole communicating with the first pressure transmission hole, and a relief hole for allowing the viscous fluid to escape from a positive pressure side to a negative pressure side, a valve body mounted on the lower rotor, and allowing the viscous fluid to escape from the positive pressure side to the negative pressure side depending on a rotating direction of the lower rotor, a relief valve moving downward by a pressure of the viscous fluid flowing in from the first and second pressure transmission holes, and a cage type relief valve supporting the relief valve and being forced to an upper rotor side.