Power seat driving apparatus for vehicle

A power seat driving apparatus for a vehicle comprising:

• a moving unit adapted to be arranged between a seat and a vehicle floor so as to move the seat relative to the vehicle floor;
• and
• a decelerating mechanism connected to the moving unit, decelerating a driving force generated by a driving source and transmitting a decelerated driving force to the moving unit, wherein
• the decelerating mechanism includes a driving gear to which the driving force generated by the driving source is inputted, a driven gear engaged with the driving gear so as to be rotatably driven in response to a rotation of the driving gear while decelerating a rotational speed of the driving force transmitted to the driving gear, and a housing rotatably supporting the driving gear and the driven gear,
• at least one of the driving gear and the driven gear includes a shaft portion formed in a cylindrical shape so as to extend along a rotational axis, and a gear portion formed coaxially with the shaft portion so that a diameter of the gear portion is set to be greater than a diameter of the shaft portion and including a tooth portion, which engages with a tooth portion formed at the other one of the driving gear and the driven gear,
• an annular recessed portion is formed at a stepped portion between the gear portion and the shaft portion so as to be coaxial with the rotational axis, the annular recessed portion includes a radially inner circumferential surface whose diameter is set to be the same degree as the diameter of the shaft portion and a radially outer circumferential surface, whose diameter is set to be smaller than a diameter of a base portion of the tooth portion, and
• the housing includes a bearing bore having a bearing surface, which contacts an outer circumferential surface of the shaft portion and the radially inner circumferential surface of the annular recessed portion and an annular protruding portion, which is fitted into the annular recessed portion and which includes an auxiliary bearing outer circumferential surface contacting the radially outer circumferential surface.