Compact high power alternator

• US 7,768,166 B2
• Filed: 12/06/2005
• Issued: 08/03/2010
• Est. Priority Date: 07/10/2003
• Status: Expired due to Fees

• Current Assignee: Magnetic Applications, Inc.
• Original Assignee: Magnetic Applications, Inc.
• Inventors: Lafontaine, Charles Y., Scott, Harold C.
• Primary Examiner(s): Le; Dang D
• Application Number:
  US11/295,888
• Publication Number:
  US 20060091761A1
• Time in Patent Office: 1,701 Days
• Field of Search: 310/90, 310/67.R, 310/156.08, 310/156.09, 310/156.14, 310/156.26
• US Class Current: 310/90
• CPC Class Codes: H02K 1/187 to inner stators
• CPC Class Codes: H02K 1/2791 Surface mounted magnets; Inset magnets
• CPC Class Codes: H02K 1/30 using intermediate parts, e.g. spiders
• CPC Class Codes: H02K 11/05 Rectifiers associated with casings, enclosures or brackets
• CPC Class Codes: H02K 21/22 with magnets rotating around the armatures, e.g. flywheel magnetos
• CPC Class Codes: H02K 2201/03 Machines characterised by aspects of the air-gap between rotor and stator
• CPC Class Codes: H02K 7/088 radially supporting the rotor directly
• CPC Class Codes: H02K 7/09 with magnetic bearings
• CPC Class Codes: H02K 9/06 with fans or impellers driven by the machine shaft
• CPC Class Codes: H02K 9/10 by gaseous cooling medium flowing in closed circuit, a part of which is external to the machine casing
• CPC Class Codes: H02K 9/19 for machines with closed casing and closed-circuit cooling using a liquid cooling medium, e.g. oil

Abstract

An apparatus for converting between mechanical and electrical energy, particularly suited for use as a compact high power alternator for automotive use and “remove and replace” retrofitting of existing vehicles. The apparatus includes a rotor with permanent magnets, a stator with a winding, and a cooling system. Mechanisms to prevent the rotor magnets from clashing with the stator by minimizing rotor displacement, and absorbing unacceptable rotor displacement are disclosed. Various open and closed cooling systems are described. Cooling is facilitated by, for example, loosely wrapping the winding end turns, use of an asynchronous airflow source, and/or directing coolant through conduits extending through the stator into thermal contact with the windings.

Claims

1. Compact, high power, power conversion apparatus comprising a shaft, a stator, and a rotor, the shaft, stator, and rotor being coaxially disposed with the rotor mounted on the shaft, the stator including at least one winding, and the rotor including a plurality of permanent magnets disposed proximate to the stator, separated from the stator by a predetermined gap distance, such that relative motion of the rotor and stator causes magnetic flux from the magnets to magnetically interact with the stator winding, wherein:

the shaft has a predetermined diameter and includes a shaft tapered portion disposed between the ends of the shaft at a predetermined position relative to the stator, the diameter of the shaft tapered portion varying in accordance with a predetermined taper from a minimum diameter greater than the predetermined diameter to a predetermined maximum diameter greater than the shaft predetermined diameter;

the rotor includes a hub and a central through-bore having the predetermined taper corresponding to that of the shaft tapered portion of the shaft, the diameter of the tapered through-bore varying in accordance with the predetermined taper from a minimum through-bore diameter greater than the shaft predetermined diameter to a predetermined maximum through-bore diameter; and

the rotor hub is disposed with the shaft journaled and extending through the hub through-bore, with the shaft tapered portion received in the through-bore with interior surface of the through bore and exterior surface of the shaft tapered portion in mating contact, wherein cooperation of the tapered rotor bore in surface contact with the shaft tapered portion positions the rotor both axially and radially with respect to the shaft and stator, coupling the rotor to the shaft for rotation therewith.

2. The apparatus of claim 1 wherein the predetermined taper is in the range of 1 in. diameter per 7 inches of length to 1 inch diameter per 16 inches of length.

3. The apparatus of claim 1 wherein the predetermined taper is on the order of 1 inch per foot.

4. The apparatus of claim 1 further including first and second endplates, an outer casing and a plurality of tie rods, cooperating to maintain alignment of the shaft, rotor, and stator, wherein:

the shaft is rotatably held by the endplates in axial alignment with the endplates with the shaft tapered portion at a predetermined position therebetween;

the stator is affixed to one of the endplates and maintained in predetermined disposition with respect thereto and with respect to the shaft tapered portion; and

the outer casing is disposed between the front and rear endplates with tie rods disposed to compress the front and rear endplates against the outer casing.

5. The apparatus of claim 1 wherein:

the rotor comprises an endcap and a cylindrical casing, the magnets being disposed on the interior of the casing; and

the stator is disposed within the rotor casing.

6. The apparatus of claim 5 wherein the rotor endcap comprises a peripheral portion connecting to the casing, the central hub having the tapered bore and a connecting portion connecting the peripheral portion to the central hub and including at least one air passageway therethrough.

7. The apparatus of claim 6 wherein the connecting portion comprises a plurality of crossarms.

8. The apparatus of claim 7 wherein, in operation, the rotor casing tends to be subject to a conical movement of the rotor casing toward and away from the stator about an anchor point, and the plurality of crossarms extend inwardly from the peripheral portion at a non-perpendicular angle relative to the axis of the rotor casing such that the rotor end cap central hub is disposed within the interior of the rotor casing, establishing the anchor point rearwardly displaced along the axis of the shaft from the axial position of the peripheral portion by a predetermined distance to reduce the extent of the conical movement of the rotor casing in the vicinity of the magnets and stator to an amount less than the predetermined gap distance.

9. The apparatus of claim 5 wherein the rotor casing is subject to potential conical displacement from nominal position relative to the stator, and the rotor endcap is contoured such that when the shaft tapered portion is received in the rotor bore, the shaft tapered portion is within the interior of the rotor casing disposed axially displaced from the forward end of the rotor casing in the direction of the magnets by a predetermined axial distance to reduce such potential conical displacement to less than the predetermined gap distance between magnets and stator.

10. The apparatus of claim 9 wherein the rotor casing has a diameter in the range of 2 ½

to 5 inches and a length in the range of 3 to 6 inches and the predetermined axial distance from the rotor casing forward end is in the range of ½

to 1 inch.

11. The apparatus of claim 9 wherein the rotor casing has a diameter in the range of 5 to 8 inches and a length in the range of 5 ½

to 10 inches and the predetermined axial distance from the rotor casing first end is in the range of ¾

inch to 2 inches.

12. The apparatus of claim 1 wherein:

the stator comprises a core including front and back side-faces and a generally cylindrical outer peripheral surface with a predetermined number of slots formed therein; and

the stator winding is wound around the core, such that with respect to at least one end face, the winding passes through a first slot, forms an end turn extending outwardly beyond the core side face, providing a space between the end turn and end face, then passes back through another slot.

13. The apparatus of claim 12 further including a fan and respective air passageways disposed to circulate air moved by the fan over the winding end turns.

14. The apparatus of claim 13 wherein the fan is electrically driven.

15. The apparatus of claim 1 further including a front endplate, a rear endplate, an outer casing, cooperating to maintain alignment of the shaft, rotor, and stator;

and

at least one air passageway through the rear end plate, at least one air passageway through the stator core, at least one air passageway through the rotor endcap, and at least one air passageway through the front end plate.

16. The apparatus of claim 15 wherein the stator core and rotor endcap are substantially open.

17. The apparatus of claim 1 wherein the rotor is adapted to rotate over a predetermined operational range of rotational speeds, operation at and above a predetermined speed within the range of speeds tending to generate heat that, if not dissipated, would raise the temperature of the magnets above a predetermined destructive level;

and the apparatus further includes cooling means for dissipating heat and maintaining the temperature of the magnets below the predetermined destructive level over the predetermined operational range of rotational speeds.

18. Compact, high power, power conversion apparatus comprising:

first and second endplates;

the endplates comprising a central hub, and outer portion, and a connecting portion connecting the outer portion to the central hub;

a shaft rotatably coupled to the first and second endplate hubs, the shaft having a predetermined diameter and including a tapered projecting portion disposed at a predetermined position between the first and second endplate hubs, the diameter of the tapered projecting portion varying, in accordance with a predetermined change in diameter per unit axial length, from a minimum diameter to a predetermined maximum diameter greater than the shaft predetermined diameter;

an outer casing having a cylindrical interior surface disposed concentric with the shaft between the first and second endplate outer portions;

a stator comprising a core and at least one conductive winding,

the core including a central aperture of predetermined cross section and a peripheral portion having respective radially extending side faces and a generally cylindrical outer peripheral surface,

the core peripheral portion having a predetermined number of slots formed therein extending between the side faces, successive slots separated by intervening portions of the core peripheral portion,

the winding being wound around the core peripheral portion through respective slots separated by a predetermined number of intervening portions of the core peripheral portion, forming end turns between the respective slots,

the stator core being fixed to the second endplate, disposed such that the core outer peripheral surface is concentric with the shaft, with the shaft extending through the stator central aperture;

a rotor comprising a hub, a cylindrical casing, and a connecting portion attaching the cylindrical casing to the hub,

the rotor hub including a tapered central through-bore, the diameter of the tapered through-bore varying, in accordance with the predetermined change in diameter per unit axial length of the shaft tapered projecting portion, from a minimum diameter greater than the shaft predetermined diameter to a predetermined maximum diameter,

the rotor hub being disposed with the shaft extending through the hub through-bore, with the shaft tapered portion received in the through-bore with interior surface of the through bore and exterior surface of the shaft tapered portion in mating contact, cooperation of the tapered rotor bore and tapered projecting shaft portion positioning the rotor both axially and radially with respect to the shaft and stator core peripheral surface, coupling the rotor to the shaft for rotation therewith,

the rotor cylindrical casing being disposed concentric with the shaft, outer casing and stator core peripheral surface, and within the outer casing between the first and second endplates, spaced apart from the interior surface of the outer casing by a predetermined distance,

the rotor including a predetermined number of permanent magnets disposed on the interior of the casing concentric with the stator core outer peripheral surface, the stator core being received within the interior of the rotor casing proximate to the rotor magnets, separated from the magnets by a predetermined gap distance, such that relative motion of the rotor and stator causes electromagnetic interaction between the magnets and the stator winding;

the first and second endplates, shaft tapered projecting portion, rotor hub tapered through-bore, and outer casing cooperating to maintain the alignment of the shaft, rotor and stator.

19. The compact, high power, power conversion apparatus of claim 18, having a range of operational speeds wherein:

the rotor and stator are configured such that rotation of the rotor at and above a predetermined speed within the range of operational speeds tends to cause generation of heat that, if not dissipated, would raise the internal temperature of the apparatus to above a level destructive to the magnets;

the rotor connecting portion and the second end plate connecting portion each include openings of predetermined cross section therethrough in predetermined disposition relative to the stator central aperture, cooperating with the stator central aperture to provide a coolant flow path over the winding end turns; and

the relative dispositions and cross sections of the stator central aperture, rotor connecting portion and the second end plate connecting portion being such that the coolant flow path permits sufficient coolant flow over the winding end turns at and above the predetermined speed to dissipate heat generated and maintain the internal temperature of the apparatus below the destructive level.

20. The apparatus of claim of 19 wherein the stator includes a plurality of windings, the end turns of such windings extending outwardly beyond the core by varying distances to present a lattice-like structure in the coolant flow path.

21. The apparatus of claim 19 wherein the predetermined speed is relatively low within the range of speeds.

22. The apparatus of claim 19 wherein the predetermined speed is idle speed.

23. The apparatus of claim 18 wherein, in the absence of external forces, the rotor is disposed in a predetermined position relative to the stator with the magnets proximate to the stator, separated from the stator by the predetermined gap distance, and further including at least one bumper disposed to prevent the position of rotor from deviating, in response to external forces, more than a predetermined amount from the predetermined position relative to the stator, such that clashing between the magnets and the stator is avoided.

24. The apparatus of claim 18 wherein the rotor casing is subject to potential conical displacement from nominal position relative to the stator, and the rotor connecting portion is contoured such that when the shaft tapered portion is received in the rotor bore, the shaft tapered projecting portion is within the interior of the rotor casing disposed axially displaced from the forward end of the rotor casing in the direction of the magnets by a predetermined axial distance to reduce such potential conical displacement to less than the predetermined gap distance between magnets and stator.

25. The apparatus of claim 18 configured as a compact high power alternator to retrofit existing vehicles.