Field assemblies having pole pieces with axial lengths less than an axial length of a back iron portion and methods of making same

• US 7,211,920 B2
• Filed: 02/18/2005
• Issued: 05/01/2007
• Est. Priority Date: 09/05/2003
• Status: Expired due to Fees

• Current Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Du, Hung T., Verbrugge, Brandon L., McCormick, Garrett P., Ortt, Earl M.
• Primary Examiner(s): NGUYEN, TRAN N
• Application Number:
  US11/062,345
• Publication Number:
  US 20050189840A1
• Time in Patent Office: 802 Days
• Field of Search: 310216-218, 310/254
• US Class Current: 310/216.001
• CPC Class Codes: H02K 1/148 Sectional cores H02K1/141 takes precedence
• CPC Class Codes: H02K 1/18 Means for mounting or fastening magnetic stationary parts on to, or to, the stator structures
• CPC Class Codes: H02K 15/0435 Wound windings
• CPC Class Codes: H02K 15/10 Applying solid insulation to windings, stators or rotors
• CPC Class Codes: H02K 15/12 Impregnating, heating or drying of windings, stators, rotors or machines
• CPC Class Codes: H02K 3/325 for windings on salient poles, such as claw-shaped poles
• CPC Class Codes: H02K 3/522 for generally annular cores with salient poles

Abstract

An electric motor, power tool using the electric motor, and method of making the electric motor includes making a stator that includes pole portions that have axial lengths less than an axial length of a back iron portion. Alternatively, or in addition, the pole portions have axially opposed ends that decrease in width. Alternatively, or in addition, the pole portions have dovetail features that are received in corresponding recesses of the back iron portion.

Claims

1. An electric motor, comprising:

a. a stator having a back iron portion and at least two pole portions on which field coils are disposed, the pole portions having an axial length less than an axial length of back iron portion;

b. the field coils formed so that ends of the field coils don'"'"'t extend beyond axial ends of the back iron portion; and

c. an armature disposed in the stator.

2. The electric motor of claim 1 wherein each pole portion has axial opposed ends where each axial opposed end gradually decreases in width from a point axially inwardly spaced from an outermost end of that axial opposed end to the outermost end of that axial opposed end.

3. The electric motor of claim 1 wherein the back iron portion comprises at least two return path pieces and each pole portion includes a pole piece, the return path pieces and pole pieces being separately formed and mated together.

4. The electric motor of claim 3 wherein the field coils are preformed and placed on the pole pieces before the pole pieces are mated to the return path pieces.

5. The electric motor of claim 3 wherein the field coils are wound on the pole pieces after the pole pieces have been mated to the return path pieces.

6. The electric motor of claim 4 wherein each pole piece has axial opposed ends where each axial opposed end gradually decreases in width from a point axially inwardly spaced from an outermost axial end of that axial opposed end to the outermost axial end of that axial opposed end.

7. The electric motor of claim 1 wherein the pole portions, back iron portion and field coils are separately formed, each pole portion having a neck with a radial outer end having a dovetail feature, the dovetail feature of each pole piece received in a corresponding recess of the back iron portion after one of the field coils has been placed over the neck of that pole piece.

8. The electric motor of claim 7 wherein each pole piece has axial opposed ends where each axial opposed end gradually decreases in width from a point axially inwardly spaced from an outermost axial end of that axial opposed end to the outermost axial end of that axial opposed end.

9. A power tool, comprising:

a. a housing;

b. a motor disposed in the housing, the motor including;

i. a stator having a back iron portion and at least two pole portions on which field coils are disposed, the pole pieces having an axial length less than an axial length of back iron portion;

ii. the field coils formed so that ends don'"'"'t extend beyond axial ends of the return path pieces; and

iii. an armature disposed in the stator.

10. The power tool of claim 9 wherein each pole portion has axial opposed ends where each axial opposed end gradually decreases in width from a point axially inwardly spaced from an outermost axial end of that axial opposed end to the outermost axial end of that axial opposed end.

11. The power tool of claim 9 wherein the back iron portion comprises at least two return path pieces and each pole portion includes a pole piece, the return path pieces and pole pieces being separately formed and mated together.

12. The power tool of claim 11 wherein the field coils are preformed and placed on the pole pieces before the pole pieces are mated to the return path pieces.

13. The power tool of claim 11 wherein the field coils are wound on the pole pieces after the pole pieces have been mated to the return path pieces.

14. The power tool of claim 11 wherein each pole portion has axial opposed ends where each axial opposed end gradually decreases in width from a point axially inwardly spaced from an outermost axial end of that axial opposed end to the outermost axial end of that axial opposed end.

15. The power tool of claim 9 wherein the pole portions, back iron portion and field coils are separately formed, each pole portion having a neck with a radial outer end having a dovetail feature, the dovetail feature of each pole piece received in a corresponding recess of the back iron portion after one of the field coils has been placed over the neck of that pole piece.

16. The power tool of claim 15 wherein each pole portion has axial opposed ends where each axial opposed end gradually decreases in width from a point axially inwardly spaced from an outermost axial end of that axial opposed end to the outermost axial end of that axial opposed end.