PURPOSE: To improve a life time by forming in a shaft mounting unit a peripheral coating part and an inertia unit receiving part and interposing between an inertia unit peripheral surface and a peripheral coating part internal peripheral surface a gel-state substance vibration-absorptively connected.

CONSTITUTION: A shaft mounting unit 10 is constituted by connecting a holding unit 11 to a boss 12. Between a receiving part 13, formed inside a peripheral coating part 11A in the peripheral edge of this holding unit 11, and an inertia unit 20, a gel-state substance 30 is interposed, and both the inertia unit 20 and the gel-state substance 30 are vibration-absorptively connected. In this way, a product can improve its life time by increasing an area of arranging the gel-state substance 30 decreasing a resisting load per unit area.