Motor armature having distributed windings for reducing arcing

• US 20050206268A1
• Filed: 09/08/2004
• Published: 09/22/2005
• Est. Priority Date: 06/14/2000
• Status: Active Grant

• Current Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Wang, Ren Hong, Walter, Richard T.
• Granted Patent: US 7,274,126 B2
• Time in Patent Office: Days
• US Class Current: 310/225
• CPC Class Codes: H02K 23/30 having lap or loop windings
• CPC Class Codes: H02K 3/38 around winding heads, equalising connectors, or connections thereto
• CPC Class Codes: Y10T 29/49009 Dynamoelectric machine
• CPC Class Codes: Y10T 29/49011 Commutator or slip ring assembly

Abstract

An armature for a brush commutated electric motor having a distributed coil winding arrangement for reducing brush arcing and electromagnetic interference (EMI). The winding pattern involves winding a first coil into a first pair of slots of the armature. A second coil having a first subcoil portion is then wound into the same slots as the first coil, while a second subcoil portion of the second coil is wound into a pair of slots that is offset by one slot position from the first pair of slots. The two subcoil portions have the same number of turns, and the total turns of the two subcoil portions equals the number of turns of the first coil. A third coil is then wound in the same slots as the second subcoil portion of the second coil. The third coil has the same number of turns as the first coil. This pattern is repeated around the armature. In a two coil per slot armature, this pattern enables the magnetic axis of each coil to be maintained at a constant angular position relative to the commutator bars to which it is coupled without the need for using uneven numbers of turns for the two subcoil portions of each segmented coil.

Claims

1. A power tool comprising:

a housing;

an electric motor supported within said housing;

said electric motor including having an armature with a plurality of circumferentially arranged winding slots;

a commutator on said armature with twice as many commutator bars as armature slots;

a stator having a plurality of field coils defining a commutation zone therebetween;

said armature including;

a first coil wound around a first pair of spaced apart ones of said slots such that said first coil at least substantially completes commutation within said commutation zone;

a second coil split into first and second serially connected subcoils, with the first subcoil wound in the first pair of slots and the second subcoil wound in a second pair of said slots offset from said first pair of slots, said second coil at least substantially completing commutation within said commutation zone; and

a third coil wound into said second pair of slots, said third coil operating to at least substantially complete commutation within said commutation zone.

2. The power tool of claim 1, wherein said first coil and said second coil have the same number of total winding turns.

3. The power tool of claim 1, wherein said first and second subcoils have the same number of winding turns.

4. The power tool of claim 1, wherein each of said coils is coupled to a pair of commutator bars on said armature;

and

wherein each coil having said first and second subcoils has one of said subcoils advanced, and the other retarded, relative to said commutator bars to which it is coupled.

5. The power tool of claim 1, wherein the first and third coils each have twice the number of winding turns of the first subcoil of the second coil.

6. The power tool of claim 1, wherein the first coil has twice the number of winding turns as each of the first and second subcoils of the second coil.

7. An electric motor comprising:

a stator having a plurality of field coils defining at least one gap therebetween, the gap defining a commutation zone;

an armature supported coaxially within the stator for rotational movement within the stator;

said armature having a plurality of circumferentially arranged winding slots;

a first coil wound in a first pair of said winding slots;

a second coil split into serially connected first and second subcoil portions, said first subcoil portion being wound in said first pair of slots and said second subcoil portion being wound in a second pair of said slots that is circumferentially offset by one slot position from said first pair of slots;

a third coil wound in said second pair of slots; and

wherein each of said first, second and third coils substantially complete commutation within said commutation zone.

8. The electric motor of claim 7, wherein each of said coils is coupled to a pair of commutator bars;

and

wherein each of said first subcoil portions is retarded, relative to said commutator bars to which it is coupled, and each of said second subcoil portions is advanced, relative to said commutator bars to which it is coupled.

9. The electric motor of claim 7, wherein said first coil has a different number of turns from said first subcoil portion of said second coil.

10. The electric motor of claim 7, wherein said first coil and said third coil each have the same number of turns.

11. The electric motor of claim 7, wherein said first coil and said third coil each have twice the number of winding turns as said first subcoil portion of said second coil.

12. The electric motor of claim 7, wherein said first subcoil portion and said second subcoil portion each have the same number of winding turns.

13. The electric motor of claim 7, further comprising a fourth coil having first and second subcoil portions;

said first subcoil portion of said fourth coil being wound in the same slots as said third coil; and

said second subcoil portion of said fourth coil being wound in a third pair of slots circumferentially offset by one slot position from said third coil.

14. The electric motor of claim 7, wherein every other coil on said armature includes a winding having no subcoil portions.

15. The electric motor of claim 7, wherein every other coil on said armature includes a winding having a pair of subcoil portions.

16. A method for forming a power tool, comprising:

forming a stator having at least a pair of field coils separated by a gap, said gap defining a commutation zone;

locating the stator within a tool housing;

locating an armature coaxially relative to the stator, and within the housing;

forming the armature with a plurality of circumferentially arranged winding slots;

winding a first coil into a first pair of said winding slots;

forming a second coil with first and second serially coupled subcoil portions, and winding said first subcoil portion into said first pair of slots, and winding said second subcoil portion into a second pair of slots that are offset by one slot position from said first pair of slots;

winding a third coil in said second pair of slots; and

forming a fourth coil with first and second subcoil portions, and winding said first subcoil portion of said fourth coil in said second pair of slots, and winding said second subcoil portion of said fourth coil in a third pair of slots that are offset by one slot position from said second pair of slots; and

wherein each of said coils at least substantially completes commutation within said commutation zone.

17. The method of claim 16, further comprising winding each of said subcoil portions with approximately half the number of winding turns as said first coil.

18. The method of claim 16, further comprising winding each of said subcoil portions with the same number of winding turns.

19. The method of claim 16, further comprising winding each of said first and third coils with an identical number of winding turns.

20. The method of claim 16, further comprising winding each of said first and third coils with identical numbers of winding turns;

and

winding each of said subcoil portions with identical numbers of winding turns.

21. A method for forming an electric motor, comprising:

forming a stator having a pair of field coils defining a gap therebetween, the gap defining a commutation zone;

forming an armature and locating the armature coaxially relative to said stator;

forming said armature with a plurality of parallel, circumferentially arranged slots;

winding a first coil in a first pair of said slots;

forming a second coil in first and second subcoil portions connected serially with one another;

winding said second coil such that said first subcoil portion is wound in said first pair of slots, and said second subcoil portion is wound in a second pair of slots offset by one slot position from said first pair of slots;

winding a third coil in said second pair of slots;

forming a fourth coil having first and second subcoil portions serially connected with one another, and winding said first subcoil portion of said fourth coil in said second pair of slots, and winding said second subcoil portion of said fourth coil in a third pair of slots offset by one slot position from said second pair of slots; and

wherein each of said coils substantially complete commutation while a magnetic axis of each said coil passes through said commutation zone.

22. The method of claim 21, wherein said electric motor forms an electric motor with twice the number of commutator bars as armature slots.

23. A method for reducing brush arcing in an electric motor, comprising:

forming a stator having at least a pair of field coils separated by a gap, the gap defining a commutation zone;

forming an armature with a plurality of circumferentially arranged slots, a second plurality of commutator bars, and locating the armature coaxially adjacent said stator;

winding a first coil in a first pair of said slots;

segmenting a second coil into first and second subcoil portions and winding said first subcoil portion in said first pair of slots, and said second subcoil portion in a second pair of slots offset by one slot position from said first pair of slots;

winding a third coil in said second pair of slots;

segmenting a fourth coil into first and second subcoil portions, and winding said first subcoil portion of said fourth coil into said second pair of slots and winding said second subcoil portion of said fourth coil into a third pair of slots that are offset by one slot position from said second pair of slots; and

further arranging said first and second subcoil portions of each of said second and fourth coils such that a magnetic axis of said first subcoil portions are advanced, relative to a pair of commutator bars with which it is associated, and that said second subcoil portions each have a magnetic axis that is retarded, relative to its associated pair of commutator bars; and

wherein each of said coils substantially completes commutation with said commutation zone.

24. The method of claim 23, wherein said subcoil portions of said third coil each have a magnetic axis, with one of said magnetic axes being retarded, relative to a pair of commutator bars to which said third coil is coupled, and the other of said subcoil portions being advanced, relative to said commutator bars.

25. A method for controlling commutation in an electric motor to reduce brush arcing, the method comprising:

winding a plurality of slots of an armature with a plurality of first coils and a plurality of second coils;

forming each of said second coils with first and second subcoil portions;

winding each of said first coils about a single pair of slots;

winding said second coils about two spaced apart pairs of slots, and further such that said first subcoil portion thereof is wound in a common pair of slots with one of said first coils, and the second subcoil portion is wound in a pair of slots that is spaced apart, by one slot position, from the first subcoil portion; and

further winding said subcoil portions such that one of said portions is advanced, relative to a pair of commutator bars with which it is coupled, while the other one of the pair is retarded relative to the same pair of commutator bars.

26. The method of claim 25, further comprising winding each of said subcoil portions with the same number of winding turns.

27. The method of claim 25, further comprising winding each subcoil portion with a lesser number of turns that each said first coil.

28. A method of controlling commutation of an electric motor, comprising:

forming an armature with a plurality of circumferentially arranged winding slots;

forming the armature with a circumferentially arranged plurality of commutator bars;

winding a first coil around a first pair of said slots and coupling said coil to a first pair of adjacent ones of said commutator bars such that a magnetic axis of said first coil is centered over the first pair of commutator bars;

forming a second coil into first and second subcoil portions, winding said first subcoil portion in the same pair of slots as the first coil and winding said second subcoil portion in a pair of winding slots that is offset by one slot position from said slots in which said first coil is wound in, and coupling ends of said second coil to a second pair of commutator bars that is offset by one said commutator bar from said first pair of commutator bars,

winding each of said first and subcoil portions with a number of turns such that said a magnetic axis of said first subcoil portion is advanced, relative to said second pair of commutator bars, and a magnetic axis of said second subcoil portion is retarded, relative to said second pair of commutator bars, and further such that a resultant magnetic axis of said second coil is centered over said second pair of commutator bars; and

each of said first and second coils at least substantially completing commutation with a predetermined, fixed commutation zone.

29. The method of claim 28, further comprising alternating winding said first and second coils around said slots such that one of said subcoil portions is wound in an overlapping pair of slots with one of said first coils.