Rotating electric motor with reduced cogging torque

• US 4,692,646 A
• Filed: 07/30/1985
• Issued: 09/08/1987
• Est. Priority Date: 08/01/1984
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Gotou, Makoto
• Primary Examiner(s): Skudy, R. S.
• Application Number:
  US06/760,509
• Time in Patent Office: 770 Days
• Field of Search: 310/180, 310/184, 310/68 R, 310/156, 310/198, 310/207, 310/185, 310/46, 310/186, 310/259, 310/187, 310/216
• US Class Current: 310/184
• CPC Class Codes: H02K 1/165 Shape, form or location of the slots
• CPC Class Codes: H02K 29/06 with position sensing devices H02K29/03 takes precedence

Abstract

A rotating electric motor has a permanent magnet member of a circular form and an armature core made of a magnetic material. The permanent magnet member has a plurality of N and S poles positioned alternately around the rotary shaft of the motor, and the number of the poles is P which is an even number. The armature core has a plurality of teeth formed between two adjacent winding slots of the armature core, and the number of the teeth is T which is an integer not less than 2P. Overlapping winding coils of polyphase winding groups are wound in the winding slots of the armature core, and the number of the phases of the polyphase winding groups is H which is an integer not less than 2. The armature core has at least a pair of short-blocks and long-blocks, each of which is a group of teeth having at least one tooth and positioned sequentially. Each short-block has at least one short-tooth and no long-tooth, and each long-block has at least one long-tooth and no short-tooth, where the effective pitch of each short-tooth is smaller than D=(360/T) degrees and the effective pitch of each long-tooth is larger than D. Because of this arrangement, the phases of the winding slots of the armature core with the period of 1 pole pitch of the permanent magnet member are different from each other, and the cogging torque of the rotating electric motor is small. Preferably, dummy-slot portions are provided at least on the faces of the long-teeth of the armature core.

Claims

1. A rotating electric motor comprising:

a field permanent magnet member substantially of a circular form having permanently magnetized N and S poles alternately positioned around a rotary shaft of said rotary electric motor, said magnet member having a number of poles P which is an even number at least equal to 4; and

an armature core of a magnetic material having a plurality of teeth each disposed between an adjacent pair of a plurality of winding slots where a plurality of overlapping winding coils of polyphase winding groups are wound, said teeth being opposed to the poles of said magnet member, said core having a number of said teeth T which is an integral multiple of P and at least equal to 2P, and said polyphase winding groups having a number of phases H which is at least equal to 2;

wherein said teeth are composed of short-teeth each having an effective pitch smaller than D=360/ T and long-teeth each having an effective pitch larger than D, wherein the effective pitch of a tooth is defined by an angle between centers of entrance parts of adjacent pairs of slots forming the tooth;

wherein said long-teeth are positioned at intervals of an equal angle, and said core has a number of said long-teeth which is less than or equal to T/2 and other than an integral multiple of P; and

wherein each of said long-teeth has a dummy-slot portion opposed to said magnet member and an effective pitch defined by an angle between centers of entrance parts of said dummy-slot and each of adjacent pairs of slots forming each of said long-teeth being equal to the effective pitch of each of said short-teeth.

2. A rotating electric motor as claimed in claim 1, wherein the number of said long-teeth is an integral multiple of H.

3. A rotating electric motor as claimed in claim 2, wherein the number of said long-teeth is equal to H.

4. A rotating electric motor as claimed in claim 2, wherein H=3.

5. A rotating electric motor as claimed in claim 1, wherein a ratio of the effective pitch of each of said short-teeth to the effective pitch of each of said long-teeth is R:

R+1, wherein R is an integer.

6. A rotating electric motor as claimed in claim 1, wherein T is an integral multiple of H multiplied by P.

7. A rotating electric motor as claimed in claim 6, wherein H=3.

8. A rotating electric motor as claimed in claim 7, wherein T=6P.

9. A rotating electric motor as claimed in claim 7, wherein T=3P.

10. A rotation electric motor comprising:

a field permanent magnet member substantially of a circular form having permanently magnetized N and S poles alternately positioned around a rotary shaft of said rotary electric motor, said magnet member having a number of poles P which is an even number at least equal to 4; and

an armature core of a magnetic material having a plurality of teeth each disposed between an adjacent pair of a plurality of winding slots where a plurality of overlapping winding coils of polyphase winding groups are wound, said teeth being opposed to the poles of said magnet member, said core having a number of said teeth T which is an integral multiple of P and at least equal to 2P, and said polyphase winding groups having a number of phases H which is at least equal to 2;

wherein said teeth are composed of short-teeth each having an effective pitch smaller than D-360/T and long-teeth each having an effective pitch larger than D, wherein the effective pitch of a tooth is defined by an angle between centers of entrance parts of adjacent pairs of slots forming the tooth;

wherein said short-teeth are positioned at intervals of an equal angle, and said core has a number of said short-teeth which is less than or equal to T/2 and other than an integral multiple of P; and

wherein each of said long-teeth has a dummy-slot portion opposed to said magnet member and an effective pitch defined by an angle between centers of entrance parts of said dummy-slot and each of adjacent pairs of slots forming each of said long-teeth being equal to the effective pitch of each of said short-teeth.

11. A rotating electric motor as claimed in claim 10, wherein the number of said short-teeth is an integral multiple of H.

12. A rotating electric motor as claimed in claim 11, wherein the number of said short-teeth is equal to H.

13. A rotating electric motor as claimed in claim 11, wherein H=3.

14. A rotating electric motor as claimed in claim 10, wherein a ratio of the effective pitch of each of said short-teeth to the effective pitch of each of said long-teeth is R:

R+1, where R is an integer.

15. A rotating electric motor as claimed in claim 10, wherein T is an integral multiple of H multiplied by P.

16. A rotating electric motor as claimed in claim 15, wherein H=3.

17. A rotating electric motor as claimed in claim 16, wherein T=6P.

18. A rotating electric motor as claimed in claim 16, wherein T=3P.

19. A rotating electric motor comprising:

a field permanent magnet member substantially of a circular form having permanently magnetized N and S poles alternately positioned around a rotary shaft of said rotary electric motor, said magnet member having a number of poles P which is an even number at least equal to 4; and

an armature core of a magnetic material having a plurality of teeth each disposed between an adjacent pair of a plurality of winding slots where a plurality of overlapping winding coils of polyphase winding groups are wound, said teeth being opposed to the poles of said magnet member, said core having a number of said teeth T which is an integral multiple of P and at least equal to 2P, and said polyphase winding groups have a number of phases H which is at least equal to 2;

wherein a group of sequential L teeth of said armature core has a pitch which is defined by an angle between centers of entrance parts of two winding slots positioned at either side of the group of sequential L teeth and equal to (360/P)Q degrees, wherein L is an integer larger than T/P and Q is an integer at least equal to 2;

wherein a ratio of a smallest effective pitch of a tooth of said sequential L teeth to an effective pitch of a m-th tooth of said sequential L teeth is R;

R+Vm, wherein the effective pitch of a tooth is defined by an angle between centers of entrance parts of an adjacent pair of winding slots forming the tooth, R being a positive integer, Vm being an integer including Q; and

wherein sum of Vm from m=l to m=L is W which is other than an integral multiple of Qd, where Qd is a divisor of Q and at least equal to 2.

20. A rotating electric motor as claimed in claim 19, wherein W=Qd-1.

21. A rotating electric motor as claimed in claim 19, wherein W=Qd+1.

22. A rotating electric motor as claimed in claim 19, wherein W=Qm-1, where Qm is an integral multiple of Q.

23. A rotating electric motor as claimed in claim 19, wherein W=Qm+1, where Qm is an integral multiple of Q.

24. A rotating electric motor as claimed in claim 19, wherein Q=P.

25. A rotating electric motor as claimed in claim 19, wherein H=3.

26. A rotating electric motor as claimed in claim 19, wherein Q is other than an integral multiple of H.

27. A rotating electric motor as claimed in claim 19, wherein at least two of said sequential L teeth respectively have dummy-slot portions opposed to said magnet member.

28. A rotating electric motor as claimed in claim 27, wherein centers of entrance parts of said dummy-slot portions and said winding slots in said group of said sequential L teeth are positioned at intervals of an equal angle.

29. A rotating electric motor comprising:

a field permanent magnet member substantially of a circular form having permanently magnetized N and S poles alternately positioned around a rotary shaft of said rotary electric motor, said magnet member having a number of poles P which is an even number at least equal to 4; and

an armature core of a magnetic material having a plurality of teeth each disposed between an adjacent pair of a plurality of winding slots where a plurality of overlapping winding coils of polyphase winding groups are wound, said teeth being opposed to the poles of said magnet member, said core having a number of said teeth T which is an integral multiple of P and at least equal to 2P, and said polyphase winding groups having a number of phases H which is at least equal to 2;

wherein at least two of said teeth respectively have dummy-slot portions opposed to said magnet member;

wherein said armature core has at least first and second slot-groups adjacent to each other, centers of entrance parts of said dummy-slot portions and said winding slots in said first slot-group being positioned at intervals of a first pitch, centers of entrance parts of said dummy-slot portions and said winding slots in said second slot-group being positioned at intervals of the first pitch; and

wherein a second pitch defined by an angle between centers of entrance parts of adjacent winding slots of said first slot-group and said second slot-group is other than an integral multiple of said first pitch.

30. A rotating electric motor as claimed in claim 29, wherein a ratio of the second pitch to the first pitch is equal to one of either (1+N/M) or (1-N/M), where M is an integer at least equal to 2 and N is a positive integer other than an integral multiple of M.