Damper device for a motor

Abstract

A damper device for a motor having a boss section attached to a rotary shaft of the motor, a mass inertia section rotatably supported by the boss section such that it surrounds the outer periphery of the boss section with a gap left therebetween, a magnetic fluid filling up the gap, and magnets provided in either the boss section or the mass inertia section for preventing leakage of the magnetic fluid. Furthermore, the boss section and the mass section facing each other through the gap are made of materials differing in the coefficient of thermal expansion, even if the magnetic fluid is heated by heating of the motor, an external temperature variation and the like so that its viscosity is decreased, such a decrease in viscosity can be canceled out by a change in gap dimension caused by the difference in expansion between the boss section material and the mass section material differing in the coefficient of thermal expansion. Therefore, the damping effect is kept constant without being influenced by thermal fluctuations.