US Patent 7165468 Starter

An outer diameter portion of a sealing member is rotatably supported by an inner surface of a nose portion. The axial movement of the sealing member is regulated. A tooth profile-shaped hole having approximately the same shape as that of a gear portion of a pinion is formed in the center of the sealing member. The gear portion of the pinion is constantly fitted into the tooth profile-shaped hole between the position where the pinion is stationary and the maximum moving position of the pinion in an axial direction. Therefore, the gear portion of the pinion cooperatively rotates with the pinion while sliding inside the tooth profile-shaped hole in the sealing member when the pinion moves on an output shaft in the direction opposite to the motor. Even after the gear portion mates with the ring gear, the sealing member cooperatively rotates with the pinion.