A junction at which the pinion shafts are connected to each other by
themselves is formed in a portion of the rotational axis of an outer
rotary member where the pinion shafts meet each other. Therefore, the
positional relation of the pinion shafts without any substantial error is
reliably secured and maintained, and the uniform transmission of power to
the pinion shafts becomes possible. Accordingly, the number of parts is
reduced, and it is not necessary to give any heat treatment to the clutch
tooth or select any material of high strength therefor.