Permanent magnet rotor

Abstract

The invention relates to a permanent magnet rotor comprising a metallic body intended to be driven in rotation around an axis (X), the rotor (1) having a plurality of magnetic poles which are distributed around the axis and alternately presenting a first magnetic pole having a first polarity and a second magnetic pole having a second polarity different from the first polarity, the first magnetic pole and the second magnetic pole being asymmetrical;the first magnetic pole comprising a first magnetic assembly having a concave shape and comprising a first permanent magnet (3) which is located in a first housing (4) and a second permanent magnet (3) which is located in a second housing (4) adjacent to the first housing, the first and second housings being partially separated from each other by a first wall (23) of the metallic body (2), the second magnetic pole comprising a first permanent magnet (3). Figure for the abbreviation: 1;

Description

Title of the invention: Permanent magnet rotor technical field

[0001] The invention relates to the field of rotating electrical machines and in particular to synchronous machines equipped with a permanent magnet rotor.

[0002] More particularly, the invention relates to a permanent magnet rotor Technological background

[0003] A rotating electrical machine is known, comprising a cylindrical stator having copper coils all around the longitudinal axis of the rotor and a cylindrical rotor having a plurality of permanent magnets located all around the longitudinal axis of the rotor. The cylindrical rotor is arranged in the stator so as to be able to rotate coaxially with the stator.

[0004] In order to increase the performance, and in particular the power and torque, of rotating electrical machines, it is known to increase the total mass of the permanent magnets present in the rotor. Thus, increasing the performance of an electrical machine results in an undesirable increase in its mass. Summary of the invention

[0005] One idea underlying the invention is to provide a permanent magnet rotor that improves the ratio between its performance and its mass.

[0006] Another idea underlying the invention is to provide an electrically rotating machine comprising a smaller quantity of permanent magnets while maintaining satisfactory performance.

[0007] According to one embodiment, the invention provides a permanent magnet rotor for an electrical rotating machine comprising a metallic body intended to be driven in rotation about an axis X, the rotor having a plurality of magnetic poles which are distributed around the axis X and alternately having at least a first magnetic pole having a first polarity and at least a second magnetic pole having a second polarity different from the first polarity, the first magnetic pole and the second magnetic pole being asymmetrical to each other with respect to a radial axis separating the first magnetic pole and the second magnetic pole; the first magnetic pole comprising a first magnetic assembly and including at least a first permanent magnet which is located in a first housing and a second permanent magnet which is located in a second housing adjacent to the first housing, the first and second housings being separated at least partially from each other by a first wall of the metallic body, in which the second magnetic pole has at least one permanent magnet.

[0008] Thus, by eliminating the symmetrical nature of the first and second magnetic poles with respect to each other, it is possible to optimize the performance / mass ratio of the rotor, which makes it possible to produce, at constant mass, a greater torque and therefore a greater output power.

[0009] In addition, since the first and second housings are separated from each other by a wall, the mechanical strength of the mechanical body, particularly under the effect of centrifugal force, is improved.

[0010] According to embodiments, such a rotor may include one or more of the following characteristics.

[0011] According to one embodiment, the first magnetic assembly has a concave shape.

[0012] According to one embodiment, the first magnetic assembly has a concavity directed radially outwards.

[0013] According to one embodiment, the first magnetic assembly has a general shape of “C”, “V” or “U”.

[0014] According to one embodiment, the first magnetic assembly includes a third permanent magnet which is located in a third housing adjacent to the second housing and is separated at least partially from said second housing by a second wall of the magnetic body.

[0015] According to one embodiment, the permanent magnets of the first magnetic pole have identical shapes.

[0016] According to one embodiment, the permanent magnets of the first magnetic pole and at least one permanent magnet of the second magnetic pole have identical dimensions.

[0017] According to one embodiment, the permanent magnets of the first magnetic pole and / or at least one permanent magnet of the second magnetic pole have a trapezoidal shape.

[0018] According to one embodiment, the first magnetic pole comprises a second magnetic assembly comprising at least one permanent magnet located radially outside the first magnetic assembly.

[0019] According to one embodiment, the second magnetic assembly has a concave shape.

[0020] According to one embodiment, the second magnetic set has a concavity that is opposite to the concavity of the first magnetic set.

[0021] According to one embodiment, the first permanent magnet of the second magnetic pole has a concave shape.

[0022] According to one embodiment, at least one permanent magnet of the second magnetic pole has a concavity opposite to that of the first magnetic assembly.

[0023] According to one embodiment, the first and second permanent magnets of the first magnetic pole and the at least one permanent magnet of the second magnetic pole each have a trapezoidal shape, the first and second permanent magnets of the first magnetic pole each having a length chosen from the shorter or longer length of the trapezoid directed radially outwards, and the at least one permanent magnet of the second magnetic pole has the other length chosen from the shorter or longer length of the trapezoid directed radially outwards.

[0024] According to one embodiment, the permanent magnets are made of an alloy chosen from: Neodymium-iron-boron (NdFeB), samarium-cobalt (SmCo) and Ferrite (iron oxide).

[0025] According to one embodiment, the first wall of the metal body has a thickness of between 3 and 4 mm.

[0026] According to one embodiment, the metallic body has a radially external surface, the distance between an external end of the first and / or second permanent magnet of the first magnetic assembly and the radially external surface being between 1 and 3 mm.

[0027] Thus, the rotor exhibits excellent mechanical properties with particular resistance to cracking and rotor degradation. It has been found that a rotor with such a characteristic can withstand fatigue tests at a speed of approximately 1.4 times the maximum rotor rotational speed.

[0028] According to one embodiment, the metallic body has a radially external surface. According to another embodiment, said radially external surface has, in a region located radially outside the first magnetic pole, an alternation of concavities and convexities.

[0029] According to one embodiment, the rotor further comprises an external fiberglass coating positioned against the radially external surface of the rotor. Such a coating limits parasitic air gaps.

[0030] According to one embodiment, the rotor has a cylindrical shape, preferably circular.

[0031] According to one embodiment, the total mass of the permanent magnets of the first magnetic pole is equal to or greater than twice the total mass of the permanent magnets of the second magnetic pole

[0032] According to one embodiment, the rotor comprises between 30 and 90 permanent magnets, preferably between 40 and 70 permanent magnets, for example 60 magnets permanent. For example, a rotor mentioned above comprising 60 permanent magnets is equivalent, in terms of quantity of magnetic flux, to a conventional rotor of the prior art comprising 172 magnets.

[0033] According to one embodiment, the invention also provides an electrical rotating machine comprising a permanent magnet rotor according to one of the preceding claims and a stator arranged radially outside said permanent magnet rotor.

[0034] According to one embodiment, the stator is cylindrical, preferably circular.

[0035] According to one embodiment, the stator comprises housings projecting from an internal circumferential surface of the stator, all around the longitudinal axis of the stator, the housings receiving copper coils.

[0036] According to one embodiment, the dwellings are spaced from each other by a predetermined distance.

[0037] According to one embodiment, the copper coils are arranged in a three-phase system.

[0038] According to one embodiment, the rotating electric machine comprises a rotor shaft positioned at the center of the rotor.

[0039] According to one embodiment, the rotating electrical machine is an electric motor or an electric generator

[0040] According to one embodiment, the invention also provides a vehicle comprising a rotating electric machine as described above. Brief description of the figures

[0041] The invention will be better understood, and other objects, details, features and advantages thereof will become more apparent from the following description of several particular embodiments of the invention, given solely by way of illustration and not limitation, with reference to the accompanying drawings.

[0042] Fig. 1 represents a cross-sectional view of a rotor for an electric rotating machine, according to a first embodiment of the invention.

[0043] Fig. 2 represents a cross-sectional view of the rotor of Fig. 1, along a plane spaced from the cutting plane of Fig. 1, in which the permanent magnets have been deliberately omitted.

[0044] Fig. 3 represents a cross-sectional view of a rotor for an electric rotating machine, according to another embodiment of the invention.

[0045] Fig. 4 represents a partial cross-sectional view of a rotor for an electric rotating machine according to another embodiment.

[0046] Fig. 5 represents a partial cross-sectional view of a rotor and stator for an electric rotating machine according to another embodiment.

[0047] Fig. 6 represents a partial cross-sectional view of a rotor for an electric rotating machine according to another embodiment.

[0048] Fig. 7 represents a partial cross-sectional view of a rotor for an electric rotating machine according to another embodiment, in which the permanent magnets have been deliberately omitted.

[0049] Fig. 8 represents a partial top view of an electrical rotating machine comprising the aforementioned rotor.

[0050] Fig. 9 represents a cross-sectional view of a rotor for an electric rotating machine, according to an embodiment not covered by the present invention. Description of the implementation methods

[0051] In the description and claims, the terms "external" and "internal," as well as the orientations "axial" and "radial," will be used to designate, according to the definitions given in the description, elements of the electric machine. By convention, the X-axis of rotation of the rotor defines the "axial" orientation. The terms "external" and "internal" are used to define the relative position of one element with respect to another, with reference to the X-axis; an element close to the X-axis is thus described as internal, as opposed to an external element located radially at the periphery.

[0052] By convention, the same reference numbers will be used to refer to the same parts, components and structures or to similar parts throughout the figures.

[0053] Figures 1 and 2 illustrate a permanent magnet rotor for an electrical rotating machine according to a first embodiment.

[0054] The rotor 1 has a general cylindrical shape and comprises a cylindrical ferrous metal body 2 having an internal orifice 21 intended to receive a rotor shaft, and an external surface 22 intended to be surrounded by a stator (not shown) located radially towards the outside of the rotor 1.

[0055] The rotor 1 consists of a plurality of discs, for example made of electrical steel, which are stacked axially against each other to form a laminate.

[0056] The rotor 1 comprises a plurality of permanent magnets 3 arranged in housings 4 provided in the metal body 2. The housings are formed by cutouts which are provided in the rotor discs and are arranged axially one after the other.

[0057] The housings 4 which house the permanent magnets 3 are located near the external surface 22 and are spaced from each other all around the X axis. In the embodiment shown, the housings further have injection holes 41, which allows the permanent magnets to be formed by injection directly into the housing 4.

[0058] Furthermore, the permanent magnets 3 have a curved shape and conform to the shape of the housings 4, which are also curved. The housings 4 have the same dimensions, and the permanent magnets 3 have the same dimensions. This limits the variety of different permanent magnets used, thereby reducing manufacturing costs.

[0059] The rotor 1 comprises eight magnetic poles, including four North poles and four South poles located all around the X axis. The South poles S and the North poles N are alternated all around the X axis, which means that the polarities of adjacent magnetic poles are different.

[0060] Each magnetic North pole N comprises two adjacent permanent magnets 3 which are separated from each other by a separating wall 23 of the metallic body 2. The separating wall has a thickness, for example, of between 3 and 4 mm.

[0061] The two permanent magnets of the North magnetic pole N form a North magnetic pole N assembly which has an overall concave shape, here in the form of a “C”, directed radially outwards.

[0062] In other words, the first lateral end 31 of the magnetic assembly and the second lateral end 32 of the magnetic assembly opposite the first lateral end 31 are closer to the external surface 22 than the central areas of the magnetic assembly. The distance between the first and second external lateral ends 31, 32 and the external surface 22 is between 1 and 3 mm.

[0063] The South magnetic poles S are each located between two North magnetic poles N. Each South magnetic pole S comprises a permanent magnet 3 forming a South magnetic pole S assembly. The South magnetic pole S assembly has a concavity opposite to the concavity of the first magnetic assembly.

[0064] The curvature of the magnetic assembly of a South magnetic pole S is the same as the curvature of the external surface 22 of the rotor 1. Thus, the entire external surface 33 of the permanent magnet 3 is located at the same distance from the external surface, i.e. for example at a distance of about 2 mm.

[0065] In the embodiment shown in [Fig.2], the separating wall 23 is interrupted, along the longitudinal direction of the rotor 1, by interruption zones 24 of the separating wall 23. In other words, the separating wall 23 between two permanent magnets of one of the North magnetic poles is not present in all the disks of the rotor 1. In the disks in which the separating wall is absent, the two permanent magnets are therefore positioned in the same cutout of the disk.

[0066] Thus, two permanent magnets 3 of a magnetic assembly of the North magnetic pole N are spaced apart from each other, along the longitudinal direction of the rotor 1, by a equivalent distance to the thickness of the separation wall 23 at the interruption zones 24 and spaced by the separation wall 23 in the other zones.

[0067] It is illustrated with [Fig.3] a rotor according to a second embodiment.

[0068] The rotor 101 of [Fig. 3] differs from the rotor 1 in that it has a coating external fiberglass positioned against external surface 22.

[0069] Figure 4 illustrates a portion of a rotor according to a third embodiment. Figure 4 is partial and illustrates a single North N magnetic pole. It should also be noted that the three other North N magnetic poles of the rotor 201 have the same characteristics as the North N magnetic pole illustrated in Figure 4.

[0070] The rotor 201 differs from the rotor 1 in that it has an additional permanent magnet 34 forming a second magnetic assembly of the North magnetic pole N. The additional permanent magnet 34 is located in an additional housing 43 comprising two injection holes 42.

[0071] The additional permanent magnet 34 is located between the two magnets 3 of the North magnetic pole N and the external surface 22. The additional permanent magnet 34 has a concave shape opposite to the concave shape of the first magnetic assembly, i.e. with a concavity directed radially inwards.

[0072] The additional permanent magnet 34, the additional housing 43 and the injection holes 42 have dimensions smaller than the permanent magnets 3, the housings 4 and the injection holes 4L, respectively.

[0073] A portion of a stator and rotor according to a fourth embodiment is illustrated in [Fig.5].

[0074] The stator 6 is positioned radially outside the rotor 301. The stator 6 has a plurality of teeth 63 that project radially inwards. The teeth 63 are spaced from each other by a predetermined interval in the circumferential direction so as to provide slots 61 between the teeth 63. Coils 62a, 62b, 62c are thus housed in the slots 61 and wound around the teeth 63. These coils 62a, 62b, 62c are arranged so as to generate a rotating magnetic field when supplied with a three-phase alternating current.

[0075] Coils 62a correspond to the first phase, coils 62b correspond to the second phase and coils 62c correspond to the third phase.

[0076] This configuration makes it possible to induce a rotary motion in the rotor 201 when the stator 6 is supplied with electricity, thus ensuring the operation of a rotating electrical machine.

[0077] The stator 6 includes an iron core comprising, for example, several plates, for example of electrical steel, which are superimposed one on top of the other to form a laminate.

[0078] The rotor 301 differs from the rotor 1 in that each of the permanent magnets 3 has a trapezoidal shape with the same dimensions.

[0079] The permanent magnet 3 of the South magnetic pole S is arranged so that its shorter length 35 is directed towards the inside of the rotor 301 and its longer length 36 is directed outwards. The permanent magnet 3 is straight, without concavity.

[0080] Conversely, the two permanent magnets 3 of the North magnetic pole N form a magnetic assembly with a generally concave shape, here in the form of a "V", directed radially outwards. Each of the two permanent magnets 3 is arranged so that its shorter length 35 is directed outwards and its longer length 36 is directed towards the inside of the rotor 301.

[0081] The distance between the outer ends of the permanent magnets and the outer wall 22 is between 1 and 3 mm, that is to say that between the long length 36 of the permanent magnet 3 of the South magnetic pole S, the lateral ends 37 opposite each other for the two permanent magnets 3 of the North magnetic pole N, and the outer wall 22 there is a distance between 1 and 3 mm.

[0082] It is illustrated with [Fig.6] a portion of a rotor according to a fifth embodiment.

[0083] The rotor 401 differs from the rotor 301 in that the magnetic assembly of the North magnetic pole N further comprises a third permanent magnet 3 situated between two permanent magnets 3, and separated from the adjacent magnets by a separating wall 23. The trapezoidal dimensions of the permanent magnets 3 are smaller than the trapezoidal dimensions of those of the rotor 301. The three permanent magnets 3 of the North magnetic pole N form a magnetic assembly having an overall concave shape, here in the form of a "U", directed radially outwards.

[0084] Trapezoidal magnets are, for example, formed by cutting a rectangular metal strip. Thus, the trapezoidal shape helps to limit material waste during the manufacture of the magnets.

[0085] It is illustrated with [Fig.7] a portion of a rotor according to a sixth embodiment.

[0086] The rotor 501 differs from the rotor 1 in that the external surface 22 has a region of curvature located opposite the North magnetic pole N. The region of curvature comprises a convex area 25 with the convexity directed outwards situated between two concave areas 26 having a concavity directed outwards.

[0087] Fig. 7 illustrates a partial view of the rotor 501 and shows a single North N magnetic pole. It should also be noted that the three other North N magnetic poles of the rotor 201 have the same characteristics as the North N magnetic pole shown in Fig. 7.

[0088] The aforementioned rotors can be included in a rotating electrical machine such as the permanent magnet synchronous machine 7 as illustrated in [Fig. 8]. This electrical machine 7 can, in particular, be used as a motor to provide propulsion for an electric or hybrid vehicle and / or as a generator for such a vehicle.

[0089] The electric machine 7 comprises a housing 8 and a stator 6 as above and a rotor 1, 101, 201, 301, 401, 501 as above which are housed in the housing 8. The stator 6 is fixed inside the housing 8 and radially surrounds the rotor 1, 101, 201, 301, 401, 501 and the rotor is mounted to rotate about the axis of rotation X.

[0090] The electric machine 7 also includes an interconnector, not shown, which allows, on the one hand, the coils to be connected to each other and, on the other hand, to be connected to a control module of the electric machine, such as an inverter configured to convert a direct current (DC) into an alternating current (AC) to power the electric machine.

[0091] Finally, [Fig. 9] illustrates a rotor according to an embodiment that is not covered by the invention. The rotor 901 differs from the rotor 1 in that the South S magnetic poles do not have permanent magnets. They are instead magnetized with a South S polarity by the permanent magnets 3 of the North N poles.

[0092] Although the invention has been described in connection with several particular embodiments, it is clearly evident that it is by no means limited to them and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention.

[0093] The use of the verb "comprise", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or other steps than those stated in a claim.

[0094] In the claims, any reference sign in parentheses shall not be interpreted as a limitation of the claim.

Claims

Demands

1. Permanent magnet rotor for an electrical rotating machine comprising a metallic body intended to be driven in rotation about an axis (X), the rotor (1, 101, 201, 301, 401, 501) having a plurality of magnetic poles which are distributed around the axis (X) and alternately having at least one first magnetic pole having a first polarity (S, N) and at least one second magnetic pole having a second polarity (S, N) different from the first polarity, the first magnetic pole and the second magnetic pole being asymmetric to each other with respect to a radial axis separating the first magnetic pole and the second magnetic pole;the first magnetic pole comprising a first magnetic assembly having at least a first permanent magnet (3) which is located in a first housing (4) and a second permanent magnet (3) which is located in a second housing (4) adjacent to the first housing, the first and second housings being separated at least partially from each other by a first wall (23) of the metallic body (2), in which the second magnetic pole has at least one permanent magnet (3).

2. Permanent magnet rotor according to claim 1, wherein the first magnetic assembly has a concave shape.

3. Permanent magnet rotor according to claim 2, wherein the first magnetic assembly has a concavity directed radially outwards.

4. Permanent magnet rotor according to any one of claims 1 to 3, wherein the first magnetic assembly comprises a third permanent magnet (3) which is located in a third housing (4) adjacent to the second housing and is separated at least partially from said second housing by a second wall (23) of the magnetic body.

5. Permanent magnet rotor according to any one of claims 1 to 4, wherein the permanent magnets of the first magnetic pole have identical shapes.

6. Permanent magnet rotor according to any one of claims 1 to 5, wherein the first magnetic pole comprises a second magnetic assembly comprising at least one permanent magnet (34) located radially outside the first magnetic assembly.

7. Permanent magnet rotor according to claim 6, wherein the second magnetic assembly has a concave shape.

8. Permanent magnet rotor according to claims 2 and 7 taken in combination, wherein the second magnetic assembly has a concavity which is opposite to the concavity of the first magnetic assembly.

9. Permanent magnet rotor according to any one of claims 1 to 8, wherein the first permanent magnet of the second magnetic pole has a concave shape.

10. Permanent magnet rotor according to claims 2 and 9 taken in combination, wherein at least one permanent magnet of the second magnetic pole has a concavity opposite to that of the first magnetic assembly.

11. Permanent magnet rotor according to any one of claims 1 to 10, wherein the first and second permanent magnets of the first magnetic pole and at least one permanent magnet of the second magnetic pole each have a trapezoidal shape, wherein the first and second permanent magnets of the first magnetic pole each have a length chosen from the shorter length (35) or the longer length (36) of the trapezoid directed radially outwards, and wherein at least one permanent magnet of the second magnetic pole has the other length chosen from the shorter or longer length of the trapezoid directed radially outwards.

12. Permanent magnet rotor according to any one of claims 1 to 11, wherein the first wall of the metal body has a thickness of between 3 and 4 mm.

13. Permanent magnet rotor according to any one of claims 1 to 12, wherein the metal body has a radially external surface (22), the distance between an external end of the first and / or second permanent magnet of the first magnetic assembly and the radially external surface being between 1 and 3 mm.

14. Permanent magnet rotor according to any one of claims 1 to 13, wherein the metal body has a radially external surface, said radially external surface having in a region 12 located radially outside the first magnetic pole an alternation of concavities (26) and convexities (25).

15. Electric rotating machine (7) comprises a permanent magnet rotor according to any one of claims 1 to 14 and a stator (6) arranged radially outside said permanent magnet rotor.

16. Vehicle comprising a rotating electrical machine according to claim 15.

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