Integrated stator-axle for in-wheel motor of an electric vehicle
One or more wheels of an electrically powered vehicle contains a motor rotor and a motor stator that is mounted on an integrated structure having a motor stator mounting element portion and wheel axle portion on each side thereof. The structure is fabricated from a unitary non-ferromagnetic substance. A rotor housing is journalled to the axle portion on both sides of the motor stator mounting element via bearings. A wheel assembly is mounted on the rotor housing thereby to be driven by the rotor. Forced-air cooling is provided through a hollow central passage. A plug separates the passage into two distinct sections, the inlet and the outlet. A plurality of cavities, provided with heat exchanger surfaces, are contained within the stator mounting element portion. Channels at each end of each cavity extend in the radial direction into the central passage. Cooling air enters from one end of the central passage, is directed through the inlet channels, the cavities and outlet channels before exiting through the opposite end of the central passage. Additional channels provide wire access to the motor stator.
The present invention relates to electrically powered vehicles, more particularly to a vehicle wheel including a drive motor and an integrated motor mounting and wheel axle structure.
BACKGROUNDDevelopment of efficient and versatile direct current motor drives has provided advantageous implementation in battery powered electric vehicles. A vehicle drive motor, with or without control circuitry therefor, can be incorporated in one or more wheels of a vehicle for direct provision of wheel traction. Such arrangements are exemplified in U.S. Pat. No. 6,617,746 to Maslov et al. and U.S. Pat. No. 6,492,756 to Maslov et al., both patents commonly assigned with the present invention and incorporated herein in their entirety.
Within the cylindrical annular rotor structure, the stator core segments are rigidly secured by two plates 42, only one of which is illustrated in the drawing. Each plate is of a rigid circular configuration having an outer diameter and a circular cutout portion at its center that forms an inner diameter. The inner diameter is sized to fit a stationary shaft 44 and to be affixed to a member 46 integral with the shaft. Along the plate periphery, the plate is provided with holes, not shown, appropriately spaced to mate with corresponding through holes 48 in the stator core segments. Each of the plates is secured to the shaft and spaced from each other appropriately to be secured to, and to sandwich, the stator core segments at each axial side thereof via the mating holes. Suitable plate structure is illustrated in more detail in the '756 patent. Thus an annular ring is formed of stator core segments that are coextensively aligned in the axial direction across the air gap from the rotor. The stationary shaft, plates and stator structure, are contained within a housing 50, to which the annular rotor backplane and permanent magnets are attached. The housing is journalled to the shaft on the outside of the plates through appropriate bushings and bearings.
“In-wheel” motor construction raises several challenges. Considerable manufacturing complexity is involved in providing the proper structural support for maintaining the motor stator and the stationary shaft separated and positioned in relation to the wheel axle. As stator and wheel axle are produced from separate pieces, they must be manufactured with very high precision and mated together very precisely to minimize misalignments. These separate parts are often made from different materials which, due to different rates of thermal expansion, creates additional stresses during temperature cycling. The use of dissimilar metals also promotes galvanic action and accelerates corrosion. Each of these detractors increases the probability of premature motor and system failure. Provision of electrical connections to the stator elements and channeling of fluid to the stator for thermal management present additional challenges. Sleeves may be required to protect wires from sharp corners and seals may be required to contain fluid used to cool the motor.
Needs thus exist for an integrated wheel and axle structure that accommodates electrical wire access to the stator and coolant flow to the stator, that reduces stresses between the stator and the axle during thermal cycling and mechanical and electrical loading, and that provides easier service disassembly/assembly.
DISCLOSURE OF THE INVENTIONThe present invention fulfills the above described needs, at least in part, by provision of an electrically powered vehicle having one or more wheels containing a motor rotor and a motor stator that is mounted on an integrated structure having a wheel axle portion and a motor stator mounting element portion. The structure is fabricated from a unitary non-ferromagnetic substance. The stator mounting element portion has a cylindrical configuration with its axis collinear with the axis of the axle. At least one ferromagnetic segment of the motor stator is joined directly to the stator mounting element portion. Preferably, the motor stator comprises a plurality of ferromagnetic core segments ferromagnetically isolated from each other and mounted on the stator mounting element portion of the integrated structure. Such isolation enhances flux concentration to maximize interaction with rotor elements.
The axle portion is a round shaft having a length greater than its diameter; the diameter of the cylindrical stator mounting element is greater than its length in the direction of the axis. The wheel axle portion extends on each axial side of the motor stator mounting element. Both axle sections are collectively termed an axle portion in the following description. The rotor has an annular ring configuration that surrounds the stator about a radial air gap. A rotor housing is journalled to the axle portion on both sides of the motor stator mounting element via bearings. A wheel assembly is mounted on the rotor housing thereby to be driven by the rotor.
A hollow central passage, extends along the axis of the axle portion and the stator mounting element portion. A plug in the passage prevents flow of air in a direct path along the entire passage. A plurality of cavities, provided with heat exchanger fins or other cooling surfaces, are contained within the stator mounting element portion. Each cavity forms an arc at a fixed radial distance from the axis and extends in a direction parallel to the axis from a first end to a second end. Channels at each end of each cavity extend in the radial direction from the respective cavity to an opening in the central passage. The plug in the central passage is located at a position intermediate the locations along the axis of the first and second ends of the cavities. Thus, incoming air from one end of the central passage is directed through the inlet channels to the first ends of the cavities, through the cavities and heat exchanger surfaces to the second ends of the cavities, through the outlet channels at the second ends and into the central passage near the exit. The wheel axle portion additionally contains one or more channels for providing wire access to the motor stator.
Additional advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description, wherein only the preferred embodiment of the invention is shown and described, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.
BRIEF DESCRIPTION OF DRAWINGSThe present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying, drawing and in which like reference numerals refer to similar elements and in which:
In the present invention, stator elements are directly mounted on an integrated structure that includes an axle portion and a stator element mounting portion. The rotor radially surrounds the stator and is separated therefrom by a radial air gap.
As shown in
The central passage 62 and the cable access channels 64 extend from the inner axle portion 60 into the stator mounting portion 68, as is more evident from
The integrated support structure can be seen from
Hollow central passage 62 contains channels 73 and 75that are circumferentially distributed about the passage. As illustrated, inlet channels 73 are vertically aligned with the left end of cavity 70 and outlet channels 75 are vertically aligned with the right end of cavity 70. Both channels 73 and 75 extend radially from the central passage 62 to ends of the cavity 70. Central passage 62 permits entry of coolant air supplied to the inner axle portion 60. Plug 76 is situated in central passage 62 at a location along the axis that is between the channels 73 and 75. The plug is a barrier that prevents a direct flow of the coolant air along the central passage 62 from the inlet at axle portion 60 to the outlet at the outer axle portion 61.
In the illustrated embodiment, it is preferred that three coolant inlet channels 73 and three corresponding outlet channels 75 be provided for each cavity 70 to permit a relatively even distribution of coolant air through the heat exchanger surfaces in the cavity. As five cavities 70 are provided in this embodiment, fifteen inlet channels 73 and fifteen outlet channels 75 are formed in the stator support portion 68. Coolant air flow paths are thus traversed from the inlet of passage 62 through the fifteen inlet channels 73, through the five cavities 70, through the fifteen outlet channels 75, and exits outwards through the central passage 62. The effective areas of the central passage 62, inlet channels 73, cavities 70 and outlet channels 75 are closely matched to minimize pressure drops in the cooling system.
In this disclosure there is shown and described only preferred embodiments of the invention and but a few examples of its versatility. It is to be understood that the invention is capable of use in various other combinations and environments and is capable of changes or modifications within the scope of the inventive concept as expressed herein. For example, it is within the contemplation of the invention that a different number of stator elements and rotor magnets may be utilized, which may indicate a change in the number of cooling cavities, cooling channels, passage holes and/or cable channels. The invention is also applicable to motors in which the stator core is a single ferromagnetic piece mounted on the integrated support structure. The concepts of the invention are not limited to permanent magnet motors, and are also applicable, for example, to reluctance motors.
Claims
1. An electric motor vehicle comprising:
- a wheel containing a motor stator and a motor rotor;
- an integrated structure fabricated from a unitary non-ferromagnetic substance, said structure having a wheel axle portion and a motor stator mounting element portion, the stator mounting element portion having a cylindrical configuration with its axis collinear with the axis of the axle, the integrated structure comprising a central passage that extends along the axis of the axle portion and the stator mounting element portion; and
- wherein at least one ferromagnetic segment of the motor stator is joined directly to the stator mounting element.
2. An electric motor vehicle as recited in claim 7, wherein the diameter of the cylindrical stator mounting element portion is greater than its length in the direction of the axis and the axle portion comprises a section formed at each axial side of the stator mounting element portion.
3. An electric motor vehicle as recited in claim 7, wherein the rotor comprises an annular ring configuration radially surrounding the stator and separated therefrom by a radial air gap, and a rotor housing; and
- the rotor housing is journalled to the axle portion via bearings.
4. An electric motor vehicle as recited in claim 3, wherein the wheel axle portion extends on each axial side of the motor stator mounting element and bearings circumscribe the axle portion on both sides of the motor stator mounting element.
5. An electric motor vehicle as recited in claim 3, wherein a wheel assembly is mounted on the rotor housing.
6. An electric motor vehicle as recited in claim 1, wherein the motor stator mounting element portion comprises cooling means in communication with said central passage for cooling the stator.
7. An electric motor vehicle [as recited in claim 6, wherein said cooling means] comprising:
- a wheel containing a motor stator and a motor rotor:
- an integrated structure fabricated from a unitary non-ferromagnetic substance, said structure having a wheel axle portion and a motor stator mounting element portion, the stator mounting element portion having a cylindrical configuration with its axis collinear with the axis of the axle, the integrated structure comprising a central passage that extends along the axis of the axle portion and the stator mounting element portion: wherein
- at least one ferromagnetic segment of the motor stator is joined directly to the stator mounting element:
- the motor stator mounting element portion comprises cooling means in communication with said central passage for cooling the stator: and
- said cooling means comprises:
- a plurality of cavities, each cavity-formed-along an arc at a fixed radial distance from the axis and extending in a direction parallel to the axis from a first end to a second end; and
- heat exchanger surfaces provided in the cavities.
8. An electric motor vehicle as recited in claim 7, wherein said central passage is hollow and contains a barrier to prevent flow of air directly along the entire passage, the barrier located in the central passage at a position intermediate the locations along the axis of the first and second ends of the cavities; and
- said cooling means further comprises a channel at each end of each cavity extending in the radial direction from the respective cavity to an opening in the central passage;
- whereby incoming air from one end of the central passage is directed through inlet channels to the first ends of the cavities, through the cavities and heat exchanger surfaces to the second ends of the cavities, through the outlet channels at the second ends and into the central passage.
9. An electric motor vehicle as recited in claim 1, further comprising at least one channel in a first of the wheel axle portion sections for providing wire access to the motor stator.
10. An electric motor vehicle as recited in claim 9, wherein the diameter of the first wheel axle portion section is greater than the diameter of the other wheel axle portion section.
11. An electric motor vehicle as recited in claim 7, wherein the motor stator comprises a plurality of ferromagnetic core segments ferromagnetically isolated from each other.
12. An electric motor apparatus comprising:
- a hollow shaft having a central passage extending from a first end to a second end;
- a stator support structure secured to said hollow shaft;
- a plurality of electric motor stator elements secured to said stator support structure; and
- a rotor housing surrounding said stator support structure, said rotor housing having a plurality of permanent magnets secured thereto;
- wherein said rotor housing is supported by said hollow shaft and said permanent magnets are separated from said stator elements by an air gap.
13. An electric motor apparatus as recited in claim 12, wherein said stator support structure is formed from a unitary material.
14. An electric motor apparatus as recited in claim 12, wherein said stator support structure is non-ferromagnetic.
15. An electric motor apparatus as recited in claim 12, wherein said stator support structure has a cylindrical shape about a central axis.
16. An electric motor apparatus as recited in claim 12, wherein said stator support structure axis is collinear with the axis of said hollow shaft.
17. An electric motor apparatus as recited in claim 12, wherein the diameter of the cylindrically shaped stator support structure is greater than its length in the direction of the axis.
18. An electric motor apparatus as recited in claim 12, wherein the first end of the hollow shaft has an outside diameter that is greater than the outside diameter at the second end.
19. An electric motor apparatus as recited in claim 12, wherein said hollow shaft comprises a cavity that extends in a radial direction from the central passage to said stator support structure.
20. An electric motor apparatus as recited in claim 19, wherein at least one heat exchanger is in thermal communication with said cavity.
21. An electric motor apparatus as recited in claim 20, wherein incoming coolant from one end of said central passage is directed through said cavity past said heat exchangers to the other end of said central passage.
22. An electric motor apparatus as recited in claim 19, wherein said cavity is in thermal communication with said air gap that separates said permanent magnets from said stator elements.
23. An electric motor apparatus as recited in claim 22, wherein said hollow shaft comprises a plurality of cable apertures.
24. The An electric motor apparatus as recited in 23, wherein said cable apertures extend through said stator support structure to allow at least one cable to extend from said stator element to a position external to said hollow shaft.
25. An electric motor apparatus as recited in claim 12, further comprising a cavity in an interior portion of the stator support structure that extends in a direction parallel to the axis from a first location to a second location, a passage extending in the radial direction from each of said first and second cavity locations to the central passage of the hollow shaft.
26. An electric motor apparatus as recited in claim 25, wherein at least one heat exchanger is in thermal communication with said cavity.
27. An electric motor apparatus as recited in claim 26, wherein incoming coolant from one end of said central passage is directed through said cavity past said heat exchangers to the other end of said central passage.
28. An electric motor apparatus as recited in claim 25, wherein said cavity is in thermal communication with said air gap that separates said permanent magnets from said stator elements.
29. An electric motor apparatus as recited in claim 28, wherein said hollow shaft has a plurality of cable apertures.
30. An electric motor apparatus as recited in claim 29, wherein said cable apertures extend through said stator support structure to allow at least one cable to extend from said stator element to a position external to said hollow shaft.
31. An electric motor apparatus as recited in claim 25, wherein said hollow shaft comprises a plug that directs at least some portion of coolant through said cavity from a first side of said plug to a second side of said plug.
32. An electric motor apparatus as recited in claim 25, wherein said cavity is formed along an arc at a fixed radial distance from the hollow shaft in a direction parallel to the axis.
33. An electric motor apparatus as recited in claim 12, wherein said hollow shaft comprises a plurality of cavities to secure said hollow shaft to a frame.
34. An electric motor apparatus as recited in claim 12, wherein said hollow shaft is secured to a machine.
35. An electric motor apparatus as recited in 34, wherein said machine is a vehicle.
36. An electric motor apparatus as recited in claim 12, wherein a wheel is adapted to be secured to said rotor housing.
37. An electric motor apparatus as recited in claim 36, wherein the wheel may be secured by a plurality of spokes.
38. An electric motor apparatus as recited in claim 12, wherein said rotor housing rotates via a bearing arrangement located on each side of said stator elements in the axial direction.
39. An electric motor apparatus as recited in claim 12, wherein the rotor housing comprises an annular ring shape.
40. An electric motor apparatus as recited in claim 12, wherein coolant means passes through said central passage during motor operation.
41. An electric motor apparatus as recited in claim 12, wherein the stator elements are ferromagnetically isolated from each other.
42. An electric motor apparatus as recited in claim 12, wherein said plurality of stator elements are in communication with a power supply.
43. An electric motor apparatus as recited in claim 12, wherein said plurality of stator elements are in communication with an electrical control unit.
44. An electric motor apparatus as recited in claim 12, wherein a back iron is located between said permanent magnets and said rotor housing.
45. An electric motor apparatus as recited in claim 12, wherein said air gap is either radial or axial.
Type: Application
Filed: Nov 13, 2003
Publication Date: May 19, 2005
Inventors: William Perkins (Dearborn, MI), Joseph Palazzolo (Commerce Twp, MI), Mansour Peyghaleh (Sterling, VA), Mark Benson (Leesburg, VA)
Application Number: 10/706,277