Asymmetrical composite magnet structure for lobed rotor

Abstract

An interior permanent magnet electric motor. A lobed rotor comprising composite slots and non-composite slots radially spaced from its longitudinal axis of rotation extending parallel to the axis. Ferrite magnets are positioned in both the composite and non-composite slots and neo magnets are positioned in the composite slots only.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross sectional view perpendicular to an axis of rotation of a motor including a lobed rotor and a stator according to one embodiment of the invention, the rotor having two (2) composite slots for a first ferrite magnet and a second neo magnet wherein the slot is trapezoidal in the area of the second neo magnet and the rotor having two (2) other arc-shaped slots for a ferrite magnet.

FIG. 2 is a cross sectional view perpendicular to an axis of rotation of a rotor according to one embodiment of the invention having two (2) composite slots for a first ferrite magnet and a second neo magnet wherein the slot is trapezoidal in the area of the second neo magnet and the rotor having two (2) other arc-shaped slots for a ferrite magnet.

FIG. 3 is a cross sectional view perpendicular to an axis of rotation of a rotor according to one embodiment of the invention having two composite trapezoidal slots for an arc shaped ferrite magnet and two contiguous rectangular pieces of a neo magnetic material, and two arc-shaped slots for a ferrite magnet, this arrangement called a dual neo consequent configuration.

FIG. 4 is a cross sectional view perpendicular to an axis of rotation of a rotor according to one embodiment of the invention having slots for receiving arc shaped ferrite magnets, two of slots being composite slots for receiving separated rectangular pieces of a neo magnetic material in trapezoidal slots.

FIG. 5 is a cross sectional view perpendicular to an axis of rotation of a rotor according to one embodiment of the invention having two slots for receiving an arc shaped ferrite magnet and having two composite slots for receiving a bread loaf shaped neo magnet and an arc shaped ferrite magnet, each slot being a precision slot.

FIG. 6 is a cross sectional view perpendicular to an axis of rotation of a rotor according to one embodiment of the invention having two composite slots for receiving an arc shaped ferrite magnet and two separated bread loaf shaped pieces of a neo magnetic material in a trapezoidal slot and two non-composite slots for receiving arc shaped ferrite magnets.

FIG. 7 is a cross sectional view perpendicular to an axis of rotation of a rotor according to one embodiment of the invention having two composite slots for receiving an arc shaped ferrite magnet with contiguous rectangular slots for receiving neo magnets, and two non-composite slots for receiving arc shaped ferrite magnets, this arrangement called a consequent T configuration.

FIG. 8 is a partial cross sectional view perpendicular to an axis of rotation of an edge of a rotor according to one embodiment of the invention showing part of a composite slot for receiving an arc shaped ferrite magnet and one or more rectangular or bread loaf neo magnets in a trapezoidal portion of the composite slot, wherein the slot terminates in a rounded-off end slot.

FIG. 9 is a partial cross sectional view perpendicular to an axis of rotation of an edge of a rotor according to one embodiment of the invention showing part of a composite slot for receiving an arc shaped ferrite magnet and one or more rectangular or bread loaf neo magnets in a trapezoidal portion of the composite slot, wherein the slot terminates in a squared-off end slot.

FIG. 10 is a partial cross sectional view perpendicular to an axis of rotation of an edge of a rotor according to one embodiment of the invention showing part of a composite slot for receiving an arc shaped ferrite magnet and one or more rectangular or bread loaf neo magnets in a trapezoidal portion of the composite slot, wherein an end opening adjacent to the slot is provided.

FIG. 11 is a graph illustrating a cogging comparison of a 62 mm bore, 24 slot, 4 pole motor having composite slots in dual neo and consequent T configurations.

Claims

1. An electric motor rotor comprising: a core having a central longitudinal axis, said core having a pair of opposing first slots radially spaced from the longitudinal axis and extending parallel to the axis wherein said longitudinal axis is positioned between the pair of first slots, said core having a pair of opposing second slots radially spaced from the longitudinal axis and extending parallel to the axis wherein said longitudinal axis is positioned between the pair of second slots;first magnets extending parallel to the longitudinal axis, said first magnets positioned in the first slots and positioned in the second slots; andsecond magnets extending parallel to the longitudinal axis, said second magnets positioned in the first slots only, wherein the second magnets are positioned between the first magnets and an outer surface of the core.

2. The rotor of claim 1 wherein the outer surface is parallel to said longitudinal axis, said outer surface having a lobe.

3. The rotor of claim 2 further comprising an air space adjacent to at least one of the first or second magnets.

4. The rotor of claim 2 wherein the first slot each comprise an arc-shaped slot having ends which terminate in a rectangular slot, wherein the second slots each comprise an arc-shaped slot, wherein the first magnets are positioned in the arc-shaped slots and wherein the second magnets are positioned with the rectangular slots to form an air gap between the first magnets and the second magnets.

5. The rotor of claim 1 wherein, when viewed in cross section, the first magnet is arch-shaped, having a convex surface facing the central longitudinal axis and a concave surface facing the second magnet.

6. The rotor of claim 5 wherein at least one of the following: (1) when viewed in cross section, the second magnet has a convex surface generally complementary to and in contact with the concave surface of the first magnet; and(2) when viewed in cross section, at least a portion of the first magnet contacts the concave surface of the second magnet.

7. The rotor of claim 1: (a) wherein said core has end slots which are contiguous with the first slots and form an air space; or(b) wherein said core has end openings adjacent to the first slots and spaced from the first slots so that the end openings are not contiguous with the first slots, said end openings forming an air space.

8. The rotor of claim 7 wherein said end slots comprise elongated slots radially spaced from the longitudinal axis and extending tangentially relative to the outer surface of the core.

9. The rotor of claim 1 wherein the first magnets are strontium ferrite, wherein the second magnets are neodymium-iron-boron, and wherein the core is steel.

10. A method of producing an electric motor comprising: forming a rotor core having a central longitudinal axis;forming a pair of opposing first slots in the rotor core, said longitudinal axis located between the first slots;forming a pair of opposing second slots in the rotor core, said longitudinal axis located between the second slots;inserting a first magnet in each of the first and second slots;inserting a second magnet in each of the first slots only, wherein said second magnet is positioned between the first magnet and an outer surface of the core;inserting the rotor core into a stator having windings; andconnecting the windings of the stator to a commutation circuit.

11. The method of claim 10 wherein the first magnets are strontium ferrite, wherein the second magnets are neodymium-iron-boron, and wherein the core is steel.

12. An electric motor comprising: a rotor including: a core having a central longitudinal axis, said core having a pair of opposing first slots radially spaced from the longitudinal axis and extending parallel to the axis wherein said longitudinal axis is positioned between the pair of first slots, said core having a pair of opposing second slots radially spaced from the longitudinal axis and extending parallel to the axis wherein said longitudinal axis is positioned between the pair of second slots;first magnets extending parallel to the longitudinal axis, said first magnets positioned in the first slots and positioned in the second slots; andsecond magnets extending parallel to the longitudinal axis, said second magnets positioned in the first slots only, wherein the second magnets are positioned between the first magnets and an outer surface of the core;a stator in magnetic coupling relation to the rotor having windings; anda commutation circuit electrically connected to the windings of the stator.

13. The rotor of claim 12 wherein the outer surface is parallel to said longitudinal axis, said outer surface having a lobe.

14. The rotor of claim 12 further comprising an air space adjacent to at least one of the first or second magnets.

15. The rotor of claim 14 wherein the first slot each comprise an arc-shaped slot having ends which terminate in a rectangular slot, wherein the second slots each comprise an arc-shaped slot, wherein the first magnets are positioned in the arc-shaped slots and wherein the second magnets are positioned with the rectangular slots to form an air gap between the first magnets and the second magnets.

16. The rotor of claim 12 wherein, when viewed in cross section, the first magnet is arch-shaped, having a convex surface facing the central longitudinal axis and a concave surface facing the second magnet.

17. The rotor of claim 12 wherein at least one of the following: (1) when viewed in cross section, the second magnet has a convex surface generally complementary to and in contact with the concave surface of the first magnet; and(2) when viewed in cross section, at least a portion of the first magnet contacts the concave surface of the second magnet.

18. The rotor of claim 12: (a) wherein said core has end slots which are contiguous with the first slots and form an air space; or(b) wherein said core has end openings adjacent to the first slots and spaced from the first slots so that the end openings are not contiguous with the first slots, said end openings forming an air space.

19. The rotor of claim 18 wherein said end slots comprise elongated slots radially spaced from the longitudinal axis and extending tangentially relative to the outer surface of the core.

20. The rotor of claim 12 wherein the first magnets are strontium ferrite, wherein the second magnets are neodymium-iron-boron, and wherein the core is steel.

21. An electric motor rotor comprising: a core having a central longitudinal axis, said core having a pair of opposing first slots radially spaced from the longitudinal axis and extending parallel to the axis wherein said longitudinal axis is positioned between the pair of first slots, said core having a pair of opposing second slots radially spaced from the longitudinal axis and extending parallel to the axis wherein said longitudinal axis is positioned between the pair of second slots;first magnets extending parallel to the longitudinal axis, said first magnets positioned in the first slots and positioned in the second slots; andsecond magnets extending parallel to the longitudinal axis, said second magnets positioned in the first slots and positioned in the second slots, wherein the second magnets are positioned between the first magnets and an outer surface of the core;wherein:(a) said core having end slots which are contiguous with the first and second slots and form an air space; or(b) said core having end openings adjacent to the first and second slots and spaced from the first and second slots, respectively, so that the end openings are not contiguous with the first slots and the second slots, said end openings forming an air space.

22. The rotor of claim 21 wherein said end slots comprise elongated slots radially spaced from the longitudinal axis and extending tangentially relative to the outer surface of the core.