Abstract: A joining structure of a power source and a transmission includes a joining portion joining a power source and a transmission to each other, the joining portion includes a first fitting portion centering a first housing and a second housing with each other, a second fitting portion where a rotary portion of the transmission is fitted to an output shaft portion of the power source, a housing spacer fixed to the first housing, and a third fitting portion including a protruding portion and a recessed portion, the recessed portion fitted to the protruding portion and centering the second housing and the housing spacer with each other, wherein in a case where the transmission is at a position where the protruding portion and the recessed portion start fitting to each other, the rotary portion is away from a position at which the rotary portion starts fitting to the output shaft portion.

Abstract: A motor includes: a rotating shaft having a key groove formed in the peripheral surface of the rotating shaft; a rotor core having a through hole in which the rotating shaft can be received and a key portion formed on the inner surface of the rotor core defining the through hole, the key portion being fittable in the key groove; and a stress relaxation groove formed at a position adjacent to the key portion in the inner surface of the rotor core defining the through hole, and depressed away from the peripheral surface of the rotating shaft. The inner surface of the through hole is arc-shaped. A bottom surface of the stress relaxation groove, located radially outward in the inner surface of the stress relaxation groove, includes an arc portion centered at the center defining the through hole.

Abstract: A motor includes: a rotating shaft having a key groove formed in the peripheral surface of the rotating shaft; a rotor core having a through hole in which the rotating shaft can be received and a key portion formed on the inner surface of the rotor core defining the through hole, the key portion being fittable in the key groove; and a stress relaxation groove formed at a position adjacent to the key portion in the inner surface of the rotor core defining the through hole, and depressed away from the peripheral surface of the rotating shaft. The inner surface of the through hole is arc-shaped. A bottom surface of the stress relaxation groove, located radially outward in the inner surface of the stress relaxation groove, includes an arc portion centered at the center defining the through hole.