PURPOSE: To prevent the transmission of vibration from a gear to a base substrate.

CONSTITUTION: In the base substrate 11, a through hole 14, into which one end side of a metal sleeve 31 is inserted, is formed. A center post 71 is constituted by having one end side of a metal post 74 inserted and bonded to a cylindrical part 73 of a resin holder 72. In the state of inserting the cylindrical part 73, into which the metal post 74 is inserted, into the metal sleeve 31 from one surface side of the base substrate 11, the center post 71 is fitted and fixed to the base substrate 11 by inserting a crew 17 into a through hole 77 and screwing it into a screw hole 16. By such a structure, transmission of a vibration from the gear to the base substrate can be prevented.