Rotary electric machine with rotor having permanent magnets with concave faces between two flat portions

Abstract

A rotary electric machine having a stator, and a rotor having a shaft and permanent magnets on the surface of the shaft, the permanent magnets having a face of concave overall shape directed toward the stator.

Claims

1. A rotary electric machine having: a stator having teeth, and an internal rotor having a shaft and permanent magnets disposed on the surface of the shaft, the permanent magnets having a face of concave overall shape directed toward the stator, a concave face of the permanent magnet of the rotor having a concave portion, the concave portion of the concave face being disposed between two flat lateral portions, the teeth of the stator having end faces of concave shape directed toward the rotor, wherein the faces of concave overall shape of the permanent magnets are directed toward the stator in a radial direction outward from an axis of rotation of the rotary electric machine, wherein a width of a permanent magnet of the rotor measured perpendicularly to the axis of rotation is between 0.1π(D.sub.S−2d)/P and 2π(D.sub.S−2d)/P mm (millimeters), where D.sub.S is the diameter of a stator bore, P is the number of poles of the rotor, and d is a simple air gap, that is to say the smallest width of the air gap.

2. The machine as claimed in claim 1, wherein the permanent magnets of the rotor have a thickness, measured along a radius of the rotor, of between 2 and 10 mm.

3. The machine as claimed in claim 1, wherein a ratio between the greatest depth of the concavity of the concave portion, measured along a radius of the rotor, and the thickness of the permanent magnet is between 0 and 0.9.

4. The machine as claimed in claim 1, wherein the permanent magnets are fastened to the shaft of the rotor by adhesive bonding.

5. The machine as claimed in claim 1, wherein the permanent magnets have a flat fastening face on the opposite side from the concave face directed towards the stator.

6. The machine according to claim 1, wherein a width of a flat lateral portion measured perpendicularly to a radius of the rotor is between 0.75 and 7 mm.

7. The machine as claimed in claim 1, wherein the rotor and stator form an air gap between one another, the air gap having a width, measured along a radius of the machine, of between 0.5 and 3 mm.

8. The machine as claimed in claim 7, wherein the width of the air gap, measured along a radius passing through the middle of one of the permanent magnets, is between 0.5 and 5 mm.

9. The machine as claimed in claim 1, wherein the concave portion has a width measured perpendicularly to a radius of the rotor of between 2 and 56 mm.

10. The machine as claimed in claim 9, wherein the greatest depth of the concavity of the concave portion, measured along a radius of the rotor, is between 0.05 and 3 mm.

11. The machine as claimed in claim 9, wherein the concave portion is a portion of a circle or ellipse in section.

12. The machine according to claim 11, wherein the radius of the circle or the major axis of the ellipse is between 0.1 h*, where h is the thickness of the magnet, and 100 h mm.

13. The machine as claimed in claim 1, wherein the stator has concentrated winding, having coils disposed on the teeth.

14. The machine as claimed in claim 13, wherein the teeth of the stator have pole shoes.

15. The machine as claimed in claim 14, wherein the opening of the slots in the stator, measured circumferentially, is between 0.175 and 8 mm.

16. The machine as claimed in claim 15, wherein the opening of the slots in the stator is measured circumferentially between the pole shoes.

Description

DETAILED DESCRIPTION

(1) The invention may be understood better from reading the following detailed description of nonlimiting implementation examples thereof and from examining the appended drawing, in which:

(2) FIG. 1 is a partial schematic view of a rotary electric machine according to the invention,

(3) FIGS. 2a and 2b are views in cross section and longitudinal section, respectively, of a permanent magnet of the machine in FIG. 1, and

(4) FIG. 3 is a view similar to FIG. 1 of an embodiment variant.

(5) FIG. 1 shows a rotary electric machine 1 according to the invention, having an external stator 10 and an internal rotor 20 having a shaft 21 and permanent magnets 22 disposed on the surface of the shaft 21.

(6) The stator 10 has concentrated winding in the example described. The stator 10 has teeth 11 that each bear an individual coil 12 disposed on the corresponding tooth. The coils 12 are connected electrically together so as to be supplied with a three-phase current.

(7) The teeth of the stator have pole shoes 13. The opening o of the slots in the stator, measured circumferentially, between the pole shoes 13, is for example around 1.5 mm.

(8) The bore of the stator, which corresponds to the inside diameter of the stator, is around 90 mm.

(9) The stator also has an external field frame surrounding the yoke (not shown).

(10) On the rotor, the shaft 21 is integral, being hollow in the middle, forming a space 26.

(11) According to the invention, the permanent magnets 22 of the rotor have a face 23 that is directed toward the stator and has a concave overall shape. The face 23 of the magnets that is directed toward the stator corresponds to the opposite face of the magnets from the axis of rotation X of the machine.

(12) The concave face 23 of a permanent magnet 22 of the rotor has a concave portion 24.

(13) The width l of the concave portion 24, measured perpendicularly to a radius of the rotor, in section, is around 9 mm in the example described.

(14) The width L of a permanent magnet 22 of the rotor, measured perpendicularly to the axis of rotation, in section, is around 13 mm.

(15) The greatest depth p of the concavity of the concave portion, measured along a radius of the rotor, in section, is around 0.5 mm.

(16) The greatest depth of the concavity of the concave portion, measured along a radius of the rotor, is situated at the middle of the concave face of the corresponding permanent magnet in the example described. The permanent magnet is symmetric with respect to a plane P that intersects it in its middle, this plane passing through the axis of rotation of the machine and a radius of the rotor.

(17) The concave portion 24 is a portion of a circle, with a radius R of around 20 mm, in section in the example described.

(18) The concave portion 24 of the concave face 23 is disposed between two flat lateral portions 26.

(19) The width e of a flat lateral portion measured perpendicularly to a radius of the rotor, in section, is around 2 mm.

(20) The concave portion forms around 75% of the total width of the corresponding magnet in the example described.

(21) The permanent magnets of the rotor have, when the machine is viewed along the axis of rotation, a cross section of rectangular overall shape, with the long side oriented perpendicularly to a radius of the machine.

(22) The permanent magnets 22 of the rotor have a thickness h, measured along a radius of the rotor, in section, of around 3 mm.

(23) A ratio p/h between the greatest depth p of the concavity of the concave portion, measured along a radius of the rotor, and the thickness h of the permanent magnet 22 is around 0.2.

(24) The rotor and the stator form an air gap 30 between one another. The air gap has a width, measured along a radius of the machine, in section, of around 0.9 mm. The width d.sub.0 of the air gap, measured along a radius passing through the middle of a magnet 22, in section, is around 1.5 mm.

(25) The bore of the rotor, which corresponds to the outside diameter of the rotor, is around 50 mm.

(26) The permanent magnets 22 of the rotor have a fastening face 28 on the opposite side from the concave face 23 directed toward the stator, said fastening face 28 having a flat shape in the example described. The flat face is oriented perpendicularly to the radius passing through the axis of rotation and intersecting the corresponding magnet 22 halfway along the latter.

(27) The permanent magnets 22 are fastened to the shaft of the rotor by adhesive bonding in a housing 29 provided for this purpose at the surface of the shaft 21. The housing 29 has a flat surface corresponding to the shape of the fastening face of the magnets.

(28) The concave face 23 may have one or more concave portions 24 and one or more flat portions 26, as illustrated above, or be entirely concave, as has been illustrated by way of example in FIG. 3.

(29) In this example, in the absence of a flat lateral portion, the concave portion 24 makes up 100% of the total width of the corresponding magnet.

(30) In the examples in question, the rotor has 16 poles and the stator has 18 teeth. If the number thereof is different, this does not constitute a departure from the scope of the present invention.

(31) The invention is not limited to the exemplary embodiments that have just been described, and the rotor may for example have a different number of poles, this also being the case for the teeth of the stator.

(32) Moreover, in the example described, the rotor is internal, but if the rotor is external, or if the machine has both an internal rotor and an external rotor that are each disposed radially on either side of the stator and are rotationally coupled, this does not constitute a departure from the scope of the present invention.

(33) The machine may be used not only as a motor but also as a generator in order to recover energy, for example.

(34) The machine according to the invention may find applications other than the motorization of robots.