PURPOSE: To reduce a gear noise by connecting a flange portion and a hub arm with a little clearance remaining between a gear member and a boss member, between the gear member and a connecting member or between the boss member and a connecting member.

CONSTITUTION: After each hub arm 22 is disposed in a groove 20 between each pair of a fan-like flange portions 18a, 18b, a pin 16c is inserted through circular holes 21, 23 and caulked by both outer surface sides of each pair of the fan-like flange portions 18a and 18b. Thus, a gear member 16a and a boss member 16b are assembled to each other. Accordingly, each hub arm 22 has a clearance to the boss member 16b and the pin 16c between the forward end surface 22a and the base 20a of the groove 20 between both side surfaces in the axial direction of the boss member 16b and both side wall surfaces 20, and between the peripheral surface of the circular hole 23 and the peripheral surface of the pin 16c. On the other hand, the inside diameter side end surfaces 18c, 18d of the fan-like flange portions 18a, 18b have clearance to the outer peripheral surface of the boss member.