To avoid the vibrations of respective members in a thrust direction and noises, etc., caused by the vibrations by a method wherein a sliding part is formed on the inner wall of a hollow container over the moving range of a power converting member and the sliding part is composed of a sliding noise absorbing member.

An armature 22 in a motor housing 20 is made to rotate and a wheelgear 30 geared with a worm 24 is turned to retarded rotation. At that time, the protrusion of the wheelgear 30 is made to slide on the inner wall of a hollow container 10 to avoid the inclination and loosening of the gear 30 and the gear 30 made of resin is made to slide on the lower part of the inner wall of the hollow container 10 made of metal to suppress the sliding noise. In a region including an output shaft 54, a power converting member 40 which slides on the rear surface of a cover 12 is pressed in a thrust direction (direction A) by a sliding member 42 which is formed integrally with the power converting member 40 and a lever 50 linked with the sliding member 42 to suppress the sliding contact noise and eliminate loosening. Further, the respective sliding parts are made from combination of sliding noise absorbing material and metallic material to suppress the sliding noise.