A coupling portion is provided on either a rotary shaft or a worm shaft in an integrally rotational manner, said coupling portion for connecting the rotary shaft to the worm shaft and having a coupling hole therein. The coupling projection provided on the other of the rotary shaft and the worm shaft is inserted in the coupling hole. A circumferential clearance and a radial clearance are formed between the inner surface of the coupling hole and the coupling projection. Circumferential buffer portions are interposed in the circumferential clearance, and radial buffer portions are interposed in the radial clearance. The inner surface of the coupling hole and the coupling projection are arranged such that the circumferential buffer portions are compressed to deform in the circumferential direction whereby to allow the buffer portions to be brought into contact with each other when the rotary shaft is rotating.
1. A motor comprising:
a motor body having a rotary shaft;
a speed reduction mechanism, which includes a worm shaft and a worm wheel meshed with the worm shaft; and
a coupling portion, which has a coupling hole and couples the rotary shaft and the worm shaft with each other so that the rotary shaft and the worm shaft are integrally rotational, wherein
the coupling portion is provided to be rotational integrally with one of the rotary shaft and the worm shaft,
a coupling projection is provided on the other one of the rotary shaft and the worm shaft, the coupling projection being inserted in the coupling hole,
a circumferential clearance, which is a clearance in a circumferential direction, and a radial clearance, which is a clearance in a radial direction, are formed between an inner surface of the coupling hole and the coupling projection,
a circumferential buffer portion is located in the circumferential clearance,
a radial buffer portion is located in the radial clearance, the radial buffer portion supporting the worm shaft by contacting the worm shaft when the motor body drives the rotary shaft to rotate and
the inner surface of the coupling hole and the coupling projection are configured to be contactable with each other in the circumferential direction while compressing and deforming the circumferential buffer portion in the circumferential direction when the motor body drives the rotary shaft to rotate and the rotation of the rotary shaft is transmitted to the worm shaft.
2. The motor according to claim 1 , wherein
the rotary shaft and the worm shaft are made of metal, and
the coupling portion is a plastic member formed separately from the rotary shaft and the worm shaft.
3. The motor according to claim 2 , wherein the circumferential buffer portion and the radial buffer portion are provided in the coupling portion.
4. The motor according to any claim 1 , wherein the circumferential buffer portion and the radial buffer portion are made of rubber.
5. The motor according to claim 1 , wherein an axial buffer portion is located between the coupling projection and a bottom surface of the coupling hole in the axial direction.
6. The motor according to claim 5 , wherein
the rotary shaft and the worm shaft are made of metal,
the coupling portion is a plastic member formed separately from the rotary shaft and the worm shaft, and
the axial buffer portion is provided in the coupling portion.
7. The motor according to claim 5 , wherein the axial buffer portion is made of rubber.
8. The motor according to claim 1 , wherein an inner surface of the coupling portion has a contact portion that contacts the coupling projection, and the circumferential buffer portion is located radially inward of the contact portion of the coupling hole inner surface.
9. The motor according to claim 1 , wherein the circumferential buffer portion supports the worm shaft by contacting the worm shaft.