Armature with a core having teeth of different circumferential widths and electric motor including the armature and a rotor

1. An armature comprising:

a multi-phase armature coil; and

an armature core including a back yoke, a plurality of large-width teeth and a plurality of small-width teeth having a smaller circumferential width than the large-width teeth, the large-width teeth each radially protruding from the back yoke and being spaced from one another in a circumferential direction of the armature core, the large-width teeth having the armature coil concentratedly wound thereon, the small-width teeth each radially protruding from the back yoke and being spaced from one another in the circumferential direction of the armature core, the small-width teeth being arranged alternately with the large-width teeth in the circumferential direction of the armature core such that there is one of the plurality of small-width teeth between each adjacent pair of the large-width teeth,

wherein

1≤ W 1/ W 2≤2,

where W 1 is a radial width of the back yoke and W 2 is the circumferential width of the small-width teeth.

2. The armature as set forth in claim 1 , wherein the small-width teeth also have the armature coil concentratedly wound thereon, and

the armature coil is comprised of a plurality of phase windings that are arranged in the circumferential direction of the armature core in a predetermined sequence.

3. The armature as set forth in claim 2 , wherein 0<N 2 ≤N 1 , where N 1 is the number of turns of the armature coil on each of the large-width teeth and N 2 is the number of turns of the armature coil on each of the small-width teeth.

4. The armature as set forth in claim 1 , wherein 1.5≤W 3 /W 2 ≤2.7, where W 3 is the circumferential width of the large-width teeth.

5. The armature as set forth in claim 4 , wherein:

W 2 is a minimum circumferential width of the small-width teeth; and

W 3 is a minimum circumferential width of the large-width teeth.

6. The armature as set forth in claim 4 , wherein:

each of the plurality of small-width teeth includes a first enlarged collar at the free end;

each of the plurality of large-width teeth includes a second enlarged collar at the free end;

W 2 is the circumferential width of the small-width teeth exclusive of the first enlarged collar; and

W 3 is the circumferential width at the large-width teeth exclusive of the second enlarged collar.

7. The armature as set forth in claim 1 , wherein each of the large-width teeth has at least one groove formed in a distal end surface thereof so as to extend in an axial direction of the armature core.

8. The armature as set forth in claim 7 , wherein for each of the large-width teeth, the least one groove formed in the distal end surface of the large-width tooth comprises a plurality of grooves that are arranged at a predetermined angular pitch in the circumferential direction of the armature core, and

θp=360°/(p×m), where θp is the predetermined angular pitch in mechanical angle, p is the number of poles and m is the number of phases of the armature coil.

9. The armature as set forth in claim 7 , wherein the armature is configured to be arranged in a rotating electric machine to face a rotor of the rotating electric machine through a gap formed therebetween, and

for each of the large-width teeth, the least one groove formed in the distal end surface of the large-width tooth has a depth greater than or equal to the size of the gap between the armature and the rotor.

10. The armature as set forth in claim 9 , wherein for each of the large-width teeth, the least one groove formed in the distal end surface of the large-width tooth has a circumferential width greater than or equal to twice the size of the gap between the armature and the rotor.

11. The armature as set forth in claim 1 , wherein the armature core further includes a plurality of slots in which the armature coil is received,

each of the slots is formed between one circumferentially-adjacent pair of the large-width and small-width teeth and has an opening at a radial end thereof on an opposite side to the back yoke, and

180°/( p×m )≤θ≤360°/( p×m )

where p is the number of poles, m is the number of phases of the armature coil and θ is an opening angle of each of the openings of the slots in mechanical angle.

12. The armature as set forth in claim 1 , wherein the armature coil is wound in an alpha winding manner.

13. The armature as set forth in claim 1 , wherein:

each of the plurality of small-width teeth has a first circumferential width at a first junction of the each of the plurality of small-width teeth and the back yoke and each of the plurality of large-width teeth has a second circumferential width at a second junction of the each of the plurality of large-width teeth and the back yoke; and

the second circumferential width is larger than the first circumferential width.

14. The armature as set forth in claim 1 , wherein windings of the multi-phase armature coil are sequentially and repeatedly arranged in phase sequence in slots formed between the plurality of small-width teeth and the plurality of large-width teeth.

15. A rotating electric machine comprising:

the armature as set forth in claim 1 ; and

a rotor disposed to face the armature through a gap formed therebetween.