Injection molded motor assembly

• US 6,020,661 A
• Filed: 02/17/1998
• Issued: 02/01/2000
• Est. Priority Date: 04/03/1995
• Status: Expired due to Term

• Current Assignee: Pacific Scientific Company (Parker-Hannifin Corporation)
• Original Assignee: Pacific Scientific Company (Parker-Hannifin Corporation)
• Inventors: Neal, Griff D., Byrnes, Edward J., Trago, Bradley A.
• Primary Examiner(s): Ramirez, Nestor
• Assistant Examiner(s): Waks, Joseph
• Application Number:
  US09/024,595
• Time in Patent Office: 714 Days
• Field of Search: 310/43, 310/217, 310/254, 310/87, 264/272.2, 264/279.1, 29/596
• US Class Current: 310/43
• CPC Class Codes: H02K 15/12 Impregnating, heating or drying of windings, stators, rotors or machines
• CPC Class Codes: H02K 15/16 Centering rotors within the stator; Balancing rotors
• CPC Class Codes: H02K 2211/03 Machines characterised by circuit boards, e.g. pcb
• CPC Class Codes: H02K 5/08 Insulating casings
• CPC Class Codes: H02K 5/225 Terminal boxes or connection arrangements specially adapted for submersible motors H02K5/132
• CPC Class Codes: Y10T 29/49009 Dynamoelectric machine

Abstract

An electrical motor and the process for forming that motor utilizes injection molding techniques to unitize the stator assembly. The stator assembly includes a stator lamination stack and preferably a metal front end cap which is secured to the lamination stack after the lamination stack is insulated and wound. The windings are terminated at a plurality of conductive pins fusion welded to the terminating ends of the windings. The stator assembly with front end cap in place is positioned in an injection molding die. Pressure is applied to the die, and molten plastic is injected under pressure to fill voids in the stator assembly, and also to form a plastic mass which will serve as the rear end cap. The rear end cap is also molded with a connector portion which fixes the conductive pins in place as a part of the connector. A bore formed in the stator assembly provides mounting surfaces for bearings on a rotor assembly.

Claims

1. An injection molded electrical motor assembly comprising:

a rotor assembly having a central rotor portion on a rotor shaft, and a rotor bearing disposed near each end of the rotor shaft;

a unitary stator assembly included a stator lamination stack forming stator poles, stator windings carried on the stator poles, a front end cap positioned on one end of the lamination stack, and a high strength plastic unitizing member comprising a unitary injection molded non-cured plastic mass that substantially encapsulates the stator poles and the windings and fills interior voids of the lamination stack, thereby unitizing the stator assembly, the plastic mass extending to and forming an unitary rear end cap disposed on another end of the lamination stack opposite the front end cap; and

a continuous bore formed in the stator assembly through the front end cap, the stator lamination stack, and the unitary rear end cap, the continuous bore defining mounting surfaces in the front and rear end caps for directly receiving and supporting the rotor bearings, the rotor assembly being carried within the bore formed in the stator assembly with the rotor beatings engaging the mounting surfaces in the end caps for support thereby, an air gap being defined between the central rotor portion and the stator lamination stack.

2. The electrical motor of claim 1, wherein the front end cap is an injection molded plastic member forming a part of said plastic mass, the front end cap further having a bearing support surface formed directly in the plastic mass.

3. The electrical motor of claim 2 further including magnetic inserts in the gaps, the plastic mass in the gaps serving to secure the inserts in the gaps.

4. The electrical motor of claim 1, wherein the stator lamination stack has a plurality of inwardly facing stator poles, each of the poles having a plurality of inwardly facing teeth separate by gaps, the plastic mass extending into the gaps.

5. The electrical motor of claim 1, wherein the molded rear end cap encapsulates an insulator insert that substantially surrounds the stator poles, the insulator carrying the stator windings.

6. The electrical motor of claim 1, wherein the front end cap is integrally formed of an injection molded plastic.

7. The electrical motor of claim 1, wherein the plastic is a thermoplastically processible resin.

8. The electrical motor of claim 1, wherein the plastic is a thermoplastically processible resin selected from the group consisting of 6,6-polyamide, 6-polyamide, 4,6-polyamide, 12,12-polyamide, 6,12-polyamide, polyamides containing aromatic monomers, polybutylene terephthalate, polyethylene terephthalate, polyethylene napththalate, polybutylene napththalate, aromatic polyesters, liquid crystal polymers, polycyclohexane dimethylol terephthalate, copolyetheresters, polyphenylene sulfide, polyacylics, polypropylene, polyethylene, polyacetals, polymethylpentene, polyetherimides, polycarbonate, polysulfone, polyethersulfone, polyphenylene oxide, polystyrene, styrene copolymer, mixtures and graft copolymers of styrene and rubber, and mixtures thereof.

9. The electrical motor of claim 8 wherein the plastic further comprises a filler.

10. The electrical motor of claim 8, wherein the plastic further comprises a reinforcement of fiberglass or carbon fiber.

11. The electrical motor of claim 1, wherein the plastic is a glass reinforced polyethylene terephthalate thermoplastic molding resin.

12. An injection molded electrical motor assembly comprising:

a rotor assembly having a central rotor portion on a rotor shaft, and a rotor bearing disposed near each end of the rotor shaft;

a unitary stator assembly including a stator lamination stack forming stator poles, stator windings carried on the stator poles, a front end cap positioned on one end of the lamination stack, and a high strength plastic unitizing member comprising a unitary injection molded plastic mass that substantially encapsulates the stator poles and the windings and fills interior voids of the lamination stack, thereby unitizing the stator assembly, the plastic mass extending to and forming an unitary rear end cap disposed on an end of the lamination stack opposite the front end cap; and

a continuous bore formed in the stator assembly through the front end cap, the stator lamination stack, and the unitary rear end cap, the continuous bore defining mounting services in the front and rear end caps for receiving and supporting the rotor bearings, the rotor assembly being carried within the bore formed in the stator assembly with the rotor bearings engaging the mounting surfaces in the end caps for support thereby, an air gap being defined between the central rotor portion and the stator lamination stack; and

wherein the front end cap is fabricated from metal and has pilot holes, the lamination stack having anchor holes, the plastic mass extending from the anchor holes in the lamination stack to the pilot holes in the front end cap to form plastic rivets which secure the front end cap to the lamination stack.

13. An injection molded electrical motor assembly comprising:

a rotor assembly having a central rotor portion on a rotor shaft, and a rotor bearing disposed near each end of the rotor shaft;

a unitary stator assembly including a stator lamination stack forming stator poles, stator windings carried on the stator poles, a front end cap positioned on one end of the lamination stack, and a high strength plastic unitizing member comprising a unitary injection molded plastic mass that substantially encapsulates the stator poles and the windings and fills interior voids of the lamination stack, thereby unitizing the stator assembly, the plastic mass extending to and forming an unitary rear end cap disposed on an end of the lamination stack opposite the front end cap; and

a continuous bore formed in the stator assembly through the front end cap, the stator lamination stack, and the unitary rear end cap, the continuous bore defining mounting services in the front and rear end caps for receiving and supporting the rotor bearings, the rotor assembly being carried within the bore formed in the stator assembly with the rotor bearings engaging the mounting surfaces in the end caps for support thereby, an air gap being defined between the central rotor portion and the stator lamination stack; and

wherein the front end cap is fabricated from metal and has pilot holes which align the anchor holes in the lamination stack, threaded fasteners inserted through the pilot holes into the anchor holes for securing the front end cap to the lamination stack and preventing creep, the plastic mass surrounding the threaded fasteners and filling the front end cap.

14. An injection molded electrical motor assembly comprising:

a rotor assembly having a central rotor portion on a rotor shaft, and a rotor bearing disposed near each end of the rotor shaft;

a unitary stator assembly including a stator lamination stack forming stator poles, stator windings carried on the stator poles, a front end cap positioned on one end of the lamination stack, and a high strength plastic unitizing member comprising a unitary injection molded plastic mass that substantially encapsulates the stator poles and the windings and fills interior voids of the lamination stack, thereby unitizing the stator assembly, the plastic mass extending to and forming an unitary rear end cap disposed on an end of the lamination stack opposite the front end cap; and

continuous bore formed in the stator assembly through the front end cap, the stator lamination stack, and the unitary rear end cap, the continuous bore defining mounting, services in the front and rear end caps for receiving and supporting the rotor bearings, the rotor assembly being carried within the bore formed in the stator assembly with the rotor bearings engaging the mounting surfaces in the end caps for support thereby, an air gap being defined between the central rotor portion and the stator lamination stack; and

wherein a matrix of conductive pins is electrically connected to the stator windings, and the molded rear end cap includes a connector housing integrally formed of injection molded plastic that is disposed around the matrix of pins, the housing adapted to receive a mating connector.

15. The electrical motor of claim 14 wherein electrical connections between conductive pins of the matrix and the stator windings comprises fusion welds securing the pins to the windings.

16. An injection molded electrical motor assembly comprising:

a rotor assembly having a central rotor portion on a rotor shaft, and a rotor bearing disposed near each end of the rotor shaft;

a unitary stator assembly including stator poles and means for magnetizing the stator poles, a front end cap positioned on one end of the lamination stack, and a plastic unitizing member comprising a unitary injection molded non-cured plastic mass that substantially encapsulates the stator poles and fills interior voids of the stator, thereby unitizing the stator assembly, the plastic mass extending to and forming an unitary rear end cap disposed on another end of the lamination stack opposite the front end cap; and

bearing support surfaces in the front and rear end caps separated by a bore of a size sufficient to receive the central rotor portion, the bearing support surfaces defining mounting surfaces in the end caps for directly receiving and supporting the rotor bearings, the rotor assembly being carried in the bore formed in the stator assembly with the rotor bearings engaging the mounting surfaces in the end caps for support thereby, an air gap being defined between the central rotor portion and the stator lamination stack.

17. The electrical motor of claim 16 in which the mounting surfaces are machined surfaces adapted to receive the rotor bearings.

18. The electrical motor of claim 16 in which the mounting surfaces are of a size adapted for interference fit with the rotor bearing when the rotor bearings are pressed into engagement with the mounting surfaces.

19. The electrical motor of claim 16 wherein the unitary stator assembly includes windings on the stator poles serving as the means for magnetizing the stator poles.

20. The electrical motor of claim 16 wherein the unitary stator assembly includes permanent magnets forming the stator poles, the magnetic polarization of the permanent magnets providing the means for magnetizing the stator poles.

21. The electrical motor of claim 16 wherein the plastic is a thermoplastically processible resin selected from the group consisting of 6,6-polyamide, 6-polyamide, 4,6-polyamide, 12,12-polyamide, 6,12-polyamide, polyamides containing aromatic monomers, polybutylene terephthalate, polyethylene terephthalate, polyethylene napththalate, polybutylene napththalate, aromatic polyesters, liquid crystal polymers, polycyclohexane dimethylol terephthalate, copolyetheresters, polyphenylene sulfide, polyacylics, polypropylene, polyethylene, polyacetals, polymethylpentene, polyetherimides, polycarbonate, polysulfone, polyethersulfone, polyphenylene oxide, polystyrene, styrene copolymer, mixtures and graft copolymers of styrene and rubber, and mixtures thereof.

22. The electrical motor of claim 16 wherein the plastic is a glass reinforced polyethylene terephthalate thermoplastic molding resin.

23. An injection molded electrical motor assembly comprising:

a rotor assembly having a central rotor portion on a rotor shaft, and a rotor bearing disposed near each end of the rotor shaft;

a unitary stator assembly including stator poles and means for magnetizing the stator poles, a front end cap positioned on one end of the lamination stack, and a plastic unitizing member comprising, a unitary injection molded plastic mass that substantially encapsulates the stator poles and fills interior voids of the stator, thereby unitizing the stator assembly, the plastic mass extending to and forming an unitary rear end cap disposed on an end of the lamination stack opposite the front end cap; and

bearing support surfaces in the front and rear end caps separated by a bore of a size sufficient to receive to the central rotor portion, the bearing support surfaces defining mounting surfaces and the end caps for receiving and supporting the rotor bearings, the rotor assembly being carried in the bore formed in the stator assembly with the rotor bearings engaging the mounting surfaces in the end caps for support thereby, an air gap being defined between the central rotor portion and the stator lamination stack; and

wherein the bearing support surface for the front end cap has a larger diameter than the bearing support surface for the rear end cap.

24. The electrical motor of claim 23 in which the bearing support surface for the front end cap continues into a smooth bore formed through the central bore but terminating short of the rear end cap, a smaller diameter bearing support surface being formed in the rear end cap.