ELECTRIC MACHINE ROTOR WITH FLUID BARRIERS VIA MAGNETIC POLE

Abstract

The invention relates to a rotor for an electric machine with a rotor body (1) and pairs of magnetic poles, each magnetic pole being composed of at least two flux barriers: an internal flux barrier comprising two inclined recesses (6) arranged on either side of a central recess (5), and an external flux barrier comprising two inclined recesses (7) arranged between the central recess (5) of the internal flux barrier and the outer edge of the rotor body (1), and a permanent magnet positioned in at least one recess (5, 6, 7) of each of said two flux barriers, and two additional recesses (20) arranged between the recesses (7) of the external flux barrier and the outer edge of the rotor body (1) to modify the trajectory of the magnetic fluxes emitted by said magnets. Figure 2 to be published

Description

Title of the invention: ELECTRIC MACHINE ROTOR WITH FLUX BARRIERS BY MAGNETIC POLE Technical field

[0001] The present invention relates to a synchronous-reluctant rotating electrical machine (assisted by permanent magnets), and more particularly concerns the particular architecture of a rotor of such a machine.

[0002] Generally, such an electrical machine comprises a stator and a rotor arranged coaxially one inside the other.

[0003] The rotor is formed of a rotor body with a stack of laminations placed on a rotor shaft. These laminations include housings for permanent magnets and perforations to create flux barriers allowing the magnetic flux from the magnets to be directed radially towards the stator and to promote the creation of a reluctance torque, and to lighten this rotor to reduce the centrifugal forces that the lamination stack must withstand.

[0004] This rotor is generally housed inside a stator which carries electrical windings configured to generate a rotating magnetic field enabling the rotor to rotate. Previous technique

[0005] As described in particular in patent application WO2020 / 020580 and in patent application WO 2022 / 0128541, the rotor of a synchronous reluctance machine comprises a plurality of axial recesses which pass through the laminations from one side to the other.

[0006] The rotor design described in patent application WO2020 / 020580 proposes a first series of axial recesses, arranged radially one above the other and spaced apart, which form housings for magnetic flux generators, here permanent magnets in the form of rectangular bars. The second series of recesses consists of perforations with an inclined radial direction, extending from these housings to the vicinity of the edge of the laminations, near the air gap. The inclined perforations are arranged symmetrically with respect to the magnet housings so as to form, each time, a geometric figure substantially in the shape of a flattened V, with the flat bottom formed by the magnet housing and the inclined arms of this V formed by the perforations. This creates flux barriers formed by the perforations.The magnetic flux from the permanent magnets can then only pass through the solid sections between the perforations. These solid sections are made of a ferromagnetic material.

[0007] The rotor design described in patent application WO 2022 / 0128541 is an improvement on the previous design and proposes a rotor body within which flux barriers are formed, with an external flux barrier and an internal flux barrier. The internal flux barrier is substantially U-shaped, and the external flux barrier is substantially V-shaped, each flux barrier comprising at least one radial magnetic bridge and one tangential magnetic bridge. This configuration of the flux barriers allows for good performance in terms of torque and power, while limiting mechanical stresses, in particular to allow applications of the electric machine over a wide range of rotational speeds, including high speeds (for example, 20,000 rpm or 30,000 rpm).

[0008] The present invention aims to further improve the design of this type of rotor with internal and external flux barriers, in order to increase its performance even further. In particular, it aims to increase the efficiency of the electric machine incorporating the rotor at low load and high speed, while ensuring the control and reduction of noise and vibrations generated by the electric machine during its operation. Summary of the invention

[0009] The invention relates firstly to a rotor for an electric machine, said rotor comprising a rotor body formed by a stack of laminations (preferably intended to be placed on a shaft called the rotor shaft, which is also part of the electric machine), and a plurality of pairs of magnetic poles, each magnetic pole being composed of at least two flux barriers, in particular two flux barriers, including: - an internal flux barrier comprising two recesses inclined relative to each other and arranged on either side of a central recess, said central recess being perpendicular to a radius of the rotor, - an external flux barrier comprising two recesses inclined relative to each other and arranged, on either side of said radius, between the central recess of the internal flux barrier and the outer edge of the rotor body,- and at least one permanent magnet positioned in at least one recess of each of said at least two flux barriers. At least one of the magnetic poles, in particular each magnetic pole, includes two additional recesses arranged between the recesses of the external flux barrier and the outer edge of the rotor body to modify the path of the magnetic fluxes emitted by said permanent magnets in the rotor.

[0010] As demonstrated later with examples, the electrical machine incorporating a rotor thus modified by these additional recesses is more efficient: it makes it possible to lower the no-load voltage peak while maintaining an effective voltage value high, which guarantees better performance in both torque / power and maximum speed of the electric machine.

[0011] According to one embodiment, the additional recesses each have, for one or each magnetic pole, a circular or oval or ovoid shape, or oblong, or triangular or polygonal type, in particular with four or more sides, in particular with rounded edges, in particular a square, a trapezoid, a rhombus, a rectangle.

[0012] The two additional recesses, for one or at least one or each magnetic pole, may have the same shape or a different shape, the same dimensions, or different dimensions.

[0013] The two additional recesses, for one or at least one or each magnetic pole, can be arranged on either side of said ray, in particular inclined to each other, and preferably arranged symmetrically with respect to said ray.

[0014] The additional recesses over the entire rotor can together represent 0.25% to 5% of the surface area of ​​the rotor cross-section.

[0015] At least one of the two additional recesses, for one or at least one or each magnetic pole, may have a portion of its edge that runs along the outer edge of the inclined recess of the nearest external flux barrier.

[0016] At least one of the two additional recesses for one or at least one or each magnetic pole, may have a part of its edge which runs along the outer edge of the rotor body.

[0017] The two additional recesses, for one or at least one or each magnetic pole, can be inclined relative to each other, and their opening angle Y is obtuse or right, and preferably identical or close to the opening angle B of the inclined recesses of the external flux barrier.

[0018] At least one of the two additional recesses for one or at least one or each magnetic pole, may be disposed at a distance from and along a portion of the outer edge of the inclined recess of the external flux barrier, in particular over at least 10% to 50% of the length of said outer edge.

[0019] One or at least one or each magnetic pole may also include at least one relief recess between the recesses of the external flux barrier and the outer edge of the rotor body. Said relief recess preferably has a substantially triangular shape. The two additional recesses may be arranged on either side of said relief recess.

[0020] The invention also relates to any electrical machine comprising a stator and a rotor as described above, said rotor being housed inside said stator. It may also include a rotating shaft on which the rotor is mounted.

[0021] Said stator may include a plurality of radial notches arranged circumferentially along said stator.

[0022] Said electrical machine may be a synchronous-reluctant electrical machine assisted by permanent magnets.

[0023] According to one embodiment, for each magnetic pole, a permanent magnet, preferably a single permanent magnet, is positioned in said central recess of said internal flux barrier.

[0024] According to one implementation, for each magnetic pole, a permanent magnet, preferably a single permanent magnet, is positioned in each inclined recess of said internal flux barrier.

[0025] According to one embodiment, for each magnetic pole, a permanent magnet, preferably a single permanent magnet, is positioned in each inclined recess of said external flux barrier.

[0026] According to one characteristic, for each magnetic pole, said inclined recesses of said internal and / or external flux barriers are symmetric with respect to said perpendicular radius of said central recess of said internal flux barrier.

[0027] Advantageously, two consecutive magnetic poles are asymmetric.

[0028] According to one embodiment, the opening angle of the inclined recesses of said internal flow barrier is strictly less than the opening angle of the inclined recesses of said external flow barrier, the opening angle of said inclined recesses of said internal or external flow barriers being defined by the angle formed between two straight lines, each straight line passing through the middle of two sides of an inclined recess, said two sides of the inclined recess being the one facing the periphery of the rotor and the one facing the center of the rotor.

[0029] Advantageously, the opening angle of the inclined recesses of said flow barrier is acute.

[0030] According to one aspect, the opening angle of the inclined recesses of said external flow barrier is obtuse or right.

[0031] According to one embodiment, each magnetic pole comprises a plurality of permanent magnets arranged in said recesses of said flux barriers, said permanent magnets being of identical dimensions.

[0032] According to an optional embodiment, at least one of the magnetic poles, in particular each magnetic pole, has a relief recess between said external flux barrier and the periphery of said rotor body, preferably said relief recess has a substantially triangular shape, preferably two sides of said triangular shape are substantially parallel to said inclined recesses of said external flux barrier.

[0033] Advantageously, said number of magnetic pole pairs is between 2 and 9, preferably between 3 and 6, and is preferably 4.

[0034] Advantageously, said at least one permanent magnet has a rectangular cross-section.

[0035] Other features and advantages of the device and method according to the invention will become apparent from the following description of non-limiting examples of embodiments, with reference to the figures attached and described below.

[0036] List of figures [Fig.la] Figure 1 represents a sheet of a rotor according to a comparative example corresponding to a prior design in accordance with the teaching of patent application WO2022 / 128541. [Fig.lb] Figure 1b represents the geometric parameterization of the rotor of [Fig.la]. [Fig.2]

[0037] Figure [Fig.2] represents a sheet of a rotor according to a first embodiment of the invention. [Fig.3] Figure 3 represents a sheet of a rotor according to a second embodiment of the invention. [Fig.4] Figure 4 represents a graph of the no-load back electromotive force (induced voltage) between phases (corresponding to the "Phase-to-phase BEMF" according to the English expression) as a function of the position of the rotor in mechanical angle, with, on the abscissa, the position of the rotor expressed in degrees (°) and on the ordinate the voltage expressed in Volts (V), for the rotor according to a comparative example 2 (according to Figure 16) and for a rotor according to example 1 of the invention (according to Figure 2), for a rotational speed of 14000 rpm. [Fig. 5] Figure 5 represents a harmonic order graph, i.e. the Fourier series decomposition of the induced open-circuit voltage between phases, with the harmonics on the abscissa and the voltage expressed in volts (V) on the ordinate, with the rotor according to comparative example 2 (Fig. 16) and a rotor according to example 1 of the invention (Fig. 2). [Fig.6] Figure 6 shows a graph of the maximum values ​​of the no-load induced phase-to-phase voltage (corresponding to the "Phase-to-phase Peak BEMF") as a function of motor speed, with the rotor speed on the x-axis. in revolutions per minute (rpm according to the corresponding English acronym for "revolution of the crank per minute"), and on the ordinate the voltage expressed in volts (V), with the rotor according to comparative example 2 ([Fig. 16]) and a rotor according to example 1 of the invention ([Fig.2]). the invention. [Fig.7] Figure 7 represents a graph of the maximum effective values ​​of the no-load induced voltage between phases (corresponding to the "Phase-to-phase RMS BEMF" according to the English expression) as a function of the motor speed, with the rotor speed in revolutions per minute (rpm) on the abscissa and the voltage expressed in volts (V) on the ordinate, with the rotor according to comparative example 2 (Fig. 16) and a rotor according to example 1 of the invention (Fig. 2). [Fig.8] Figure 8 represents a graph of the mechanical torque envelope under load of the electric machine expressed in Newton-meters (Nm) as a function of the rotational speed expressed in revolutions per minute (rpm), for the machine equipped with the rotor according to comparative example 2 (Fig. 16) and the rotor according to example 1 of the invention (Fig. 2). [Fig.9] Figure 9 represents a graph of the mechanical power envelope under load (expressed in watts (W) as a function of the rotational speed expressed in revolutions per minute (rpm), for the machine equipped with the rotor according to comparative example 2 (Fig. 16) and the rotor according to example 1 of the invention (Fig. 2). [Fig.10] Figure 10 shows two side-by-side graphs: the graph on the right shows the electromagnetic torque ripples (“EM Torque ripple”) as a function of the maximum current (“Ipeak” expressed in amperes (A)) for the machine equipped with the rotor according to comparative example 2 (Fig. 16) and the rotor according to example 1 of the invention (Fig. 2); and the graph on the left shows the average electromagnetic torque (“EM Mean Torque”) expressed in Nm as a function of the maximum current (“Ipeak” expressed in amperes (A)) for the machine equipped with the rotor according to comparative example 2 (Fig. 16) and the rotor according to example 1 of the invention (Fig. 2). [Fig.11] Figure 11 shows a graph comparing the efficiency of two electrical machines as a function of the machine speed (rpm) and mechanical torque. (in Nm) for the machine equipped with the rotor according to comparative example 2 ([Fig. 16]) and the rotor according to example 1 of the invention ([Fig.2]). [Fig.12] Figure 12 represents a graph with the mechanical torque envelope (in Nm) as a function of the wheel rotation speed expressed in revolutions per minute (rpm), for a motor vehicle equipped with the electric machine equipped with the rotor according to comparative example 2 (Fig. 16) and the rotor according to example 1 of the invention (Fig. 2). [Fig.13] Figure 13 represents a graph with the mechanical power envelope (W) as a function of the wheel rotation speed expressed in revolutions per minute (rpm), for a motor vehicle equipped with the electric machine equipped with the rotor according to comparative example 2 (Fig. 16) and the rotor according to example 1 of the invention (Fig. 2). [Fig.14] Figure 14 represents a sheet of a rotor according to a third embodiment (example 3) of the invention. The figures representing the rotors, in particular, are schematic for ease of reading and do not necessarily represent a portion of the rotor in its operating position within the electrical machine. The same reference numerals designate the same element / object from one figure to another. [Fig.15] Fig. 15 represents, on the left, the distribution of the flow lines according to the comparative example of Figure 1 with the V-shaped barrier and the U-shaped barrier, and, on the right, the same area of ​​the rotor but this time according to the invention, as shown in Fig. 2, with the two additional recesses. [Fig.16] Figure 16 represents a sheet of a rotor according to a second comparative example (comparative example 2).

[0038] A series of examples will be described with the figures: Comparative example 1 is shown in Figure 1. Comparative example 2 is shown in [Fig.16]. Example 1 according to the invention is shown in [Fig.2]. Example 2 according to the invention is shown in [Fig.3]. Example 3 according to the invention is shown in [Fig. 14]. Description of the implementation methods

[0039] The present invention relates to a rotor for an electrical machine, in particular a synchro-reluctance type electrical machine assisted by permanent magnets. Furthermore, the present invention relates to an electrical machine comprising a rotor according to the invention and a stator, the rotor being arranged within the stator coaxially therewith. The machine may also include the rotor shaft.

[0040] The present invention is an improvement on the rotor design described in the aforementioned patent application WO2022 / 128541, to which reference may be made for further details. Embodiments of the rotor design according to that application will therefore be described below. This design is supplemented / modified by the invention through the addition of so-called supplementary recesses, which are not intended to receive magnets, but rather to modify, by creating these air pockets, the trajectory of the magnet flux within the rotor, thereby achieving multiple advantages described and demonstrated later.

[0041] The rotor for an electric machine according to patent application WO2022 / 128541 has features also used in the context of the present invention, namely: - a rotor body formed by a stack of sheet metal, preferably the rotor body can be placed on a rotor shaft, - a plurality of pairs of magnetic poles, each magnetic pole is composed of - two flux barriers: an external flux barrier, which is closer to the periphery of the rotor, and an internal flux barrier, which is closer to the center of the rotor, the flux barriers being formed by a plurality of axial recesses (the axial direction being the axial direction of the rotor), - at least one permanent magnet positioned in one of the axial recesses of said rotor body. The presence of at least one permanent magnet generates a magnetic flux, enabling the rotor to rotate by creating a rotating magnetic field generated by the stator. Flux barriers guide the magnetic field generated by the rotor and the at least one permanent magnet towards the air gap (the space between the rotor's periphery and the stator), thereby limiting magnetic flux leakage and increasing the performance (particularly torque and power) of the electric machine. A pair of magnetic poles comprises two magnetic poles of opposite polarities.

[0042] For each magnetic pole, the internal flux barrier consists of three recesses: two inclined (lateral) recesses positioned and spaced on either side of a central recess, which is perpendicular to a radius of the rotor. The recesses of the internal flux barrier form substantially a U-shape (with respect to a cross-section with respect to the rotor axis, which corresponds to the plane of a sheet constituting the body). of the rotor), the base of the U being formed by the central recess, and the opposite segments of the U being formed by the inclined recesses. Furthermore, the two inclined recesses are spaced away from the periphery of the rotor. In other words, there is a magnetic bridge (a material bridge) between the inclined recesses and the central recess, and there is another magnetic bridge (a material bridge) between the inclined recesses and the periphery of the rotor. These spacings, achieved by these magnetic bridges, ensure good mechanical strength of the rotor body while maintaining its good magnetic properties.Indeed, tangential magnetic bridges (between the inclined recesses and the rotor periphery) create local saturation, thus directing the magnetic flux generated by at least one permanent magnet towards the air gap of the electric machine. Radial magnetic bridges (between the inclined recesses and the central recess) improve the mechanical strength of the electric machine at high speeds (e.g., 20,000, 30,000 rpm). This advantage can also be leveraged for low-speed applications (e.g., 10,000 rpm) to optimize the bridges and maximize torque density. The recesses are inclined relative to the radius perpendicular to the central recess.In other words, each inclined recess is oriented so as to form an angle with respect to the ray perpendicular to the central recess, this angle being non-zero and not a right angle (in other words, the inclined recesses are neither parallel nor perpendicular to the ray perpendicular to the central recess).

[0043] Furthermore, for each magnetic pole, the external flux barrier consists of two recesses: two recesses spaced apart and inclined (lateral) with respect to the radius perpendicular to the central recess of the internal flux barrier of the magnetic pole. The recesses of the external flux barrier substantially form a V (with respect to a cross-section with respect to the rotor axis, which corresponds to the plane of a sheet constituting the rotor body), each inclined recess forming a segment of the V. Moreover, the two inclined recesses are spaced apart from the periphery of the rotor. In other words, there is a magnetic bridge (a material bridge) between the inclined recesses, and there is a magnetic bridge (a material bridge) between the inclined recesses and the periphery of the rotor.

[0044] This spacing achieved by this material bridge ensures good mechanical strength of the rotor body, while maintaining good magnetic properties of the rotor body. Indeed, the tangential magnetic bridges (between the inclined recesses and the periphery of the rotor) create local saturation, thus allowing the magnetic flux created by at least one permanent magnet to be directed towards the air gap, and the radial magnetic bridges (between the inclined recesses) improve the mechanical strength of the electric machine at high speeds (for example, 20,000, 30,000 rpm). This advantage can also be used for low-speed applications (for example, 10,000 rpm) to optimize the bridges and maximize torque density. The angle formed by each inclined recess with respect to the radius perpendicular to the central recess is non-zero and not a right angle (in other words, the inclined recesses are neither parallel nor perpendicular to the radius perpendicular to the central recess).

[0045] According to one embodiment, the central recess of the internal flow barrier may have (in the transverse plane of the rotor) a length substantially identical to the length of the lateral recesses of the internal flow barrier. In other words, the length of the central recess of the internal flow barrier may be between 75 and 125% of the length of the lateral recesses of the internal flow barrier.

[0046] The laminations can be made of ferromagnetic material so as to guide the magnetic flux of the permanent magnets and the stator. The recesses of the flux barriers can be obtained by perforations in the stacked laminations forming the rotor body, and the magnetic bridges are formed by the lamination itself.

[0047] At least one permanent magnet may have a rectangular parallelepiped shape, one dimension of which is parallel to the rotor axis. In particular, in a cross-section across the rotor axis, the at least one permanent magnet may have a rectangular shape. Preferably, all the permanent magnets may have a rectangular parallelepiped shape. Alternatively, the at least one permanent magnet may have other shapes, in particular a parallelogram shape in a cross-section across the rotor axis, for example, substantially a trapezoidal shape.

[0048] According to another alternative, in which the permanent magnets can be plasto-magnets (flexible magnets), the permanent magnet can have a parallelogram shape in cross-section, or a curved shape. One example is the plasto-ferrite material, which is composed of ferrite powder mixed with a thermoplastic binder. This compound combines the magnetic properties of ferrite with the mechanical properties of thermoplastic.

[0049] The recesses may preferably have a shape compatible with the shape of at least one permanent magnet. For example, the recess may have a substantially parallelogram shape (in cross-section), for example trapezoidal or rectangular, or curved shape (particularly in the case of a plasto-magnet). The recesses may further include additional shapes at at least one, preferably both, ends of the recess considered in the rotor cross-section. These additional shapes may be circular, rectangular, oval, curved, L-shaped, or other. These additional shapes of the recesses allow, when a permanent magnet is provided in the recess, for limiting magnetic flux losses and channeling the magnetic flux towards the air gap of the electrical machine and to limit mechanical stress in magnetic bridges. These additional shapes can be filled with a material such as resin, in particular to ensure the stability of permanent magnets. For the embodiment in which the magnet is in the form of a plastic magnet, the recesses may preferably not include additional shapes at the ends.

[0050] For each magnetic pole, a permanent magnet can be positioned in the central recess of the internal flux barrier. Preferably, a single permanent magnet can be positioned in the central recess. Thus, the number of permanent magnets per recess is limited, which simplifies the manufacturing operations of the electrical machine and avoids the manufacturing constraints of the permanent magnets.

[0051] Alternatively or cumulatively, for each magnetic pole, a permanent magnet can be positioned in each lateral recess of the internal flux barrier. Preferably, a single permanent magnet can be positioned in each lateral recess of the internal flux barrier. Thus, the number of permanent magnets per recess is limited, which simplifies the manufacturing operations of the electrical machine and avoids the manufacturing constraints of the permanent magnets.

[0052] Alternatively or in addition to one of the two preceding embodiments, for each magnetic pole, a permanent magnet can be positioned in each lateral recess of the external flux barrier. Preferably, a single permanent magnet can be positioned in each lateral recess of the external flux barrier. Thus, the number of permanent magnets per recess is limited, which simplifies the manufacturing operations of the electrical machine and avoids the manufacturing constraints of the permanent magnets.

[0053] According to a preferred embodiment, each magnetic pole can comprise five permanent magnets positioned in the five recesses: in the three recesses of the internal flux barrier, and in the two recesses of the external flux barrier. This implementation improves torque density and power density. Having five magnets also allows for a smaller diameter rotor with a high number of pole pairs, since fewer magnets need to be arranged within each magnetic pole, while respecting industrial constraints on the dimensions of permanent magnets.

[0054] Alternatively, only the lateral recesses of the internal and external flow barriers may be provided with permanent magnets.

[0055] When each magnetic pole comprises a plurality of permanent magnets, the permanent magnets can have identical dimensions. This solution ensures good performance of the electrical machine while minimizing the cost manufacturing. This design is particularly advantageous when each magnetic pole has five permanent magnets.

[0056] Alternatively, the dimensions of the permanent magnets may be different.

[0057] For each magnetic pole, the lateral recesses of the internal and / or external flux barriers can be symmetrical with respect to the radius perpendicular to the central recess of the internal flux barrier. Preferably, this symmetry exists for both the internal and external flux barriers. When the external flux barrier is symmetrical, the magnetic bridge located between the inclined recesses is radial and lies on the radius perpendicular to the central recess of the internal flux barrier. This symmetry allows for optimization of the mechanical performance of the electric machine.

[0058] Advantageously, the central recess of the internal flow barrier can also be symmetrical to the radius that is perpendicular to it.

[0059] All the rotor's magnetic poles can be identical. Alternatively, consecutive rotor magnetic poles can be different: two consecutive rotor magnetic poles are then asymmetrical. This asymmetry can be created by different inclination angles of the inclined recesses of the internal and external flux barriers. For this implementation, if the rotor has p pairs of magnetic poles, it comprises p identical primary magnetic poles and p identical secondary magnetic poles, which are different from the primary magnetic poles, with the secondary magnetic poles interposed between the primary magnetic poles. This asymmetrical design reduces torque ripple, back electromotive force harmonics, and acoustic noise.

[0060] For this embodiment, relationships can be defined between the angles of the magnetic poles. If p denotes the number of pole pairs of the rotor, the average angle of a magnetic pole (which would be the angle of the magnetic poles of a rotor without asymmetry) can be denoted:

[0061] y =

[0062] The angle between the primary magnetic poles, ypl, can then be written by an equation of the form: ypl = kxy, where k is an asymmetry constant. According to one embodiment of the invention, k can be between 0.9 and 1 (inclusive lower bound), and preferably between 0.91 and 0.95 (inclusive). These value ranges allow for a good reduction of torque ripple.

[0063] The angle of the secondary magnetic poles yp2 can then be deduced from the equation: yp2 = 2y-ypl

[0064] An angle of inclination of the inclined recesses can be defined which corresponds to the angle between a straight line passing through the center C of the rotor and a midpoint positioned at the level of an external face of the inclined recess of the considered flow barrier and the radius perpendicular to the central recess of the internal flow barrier. The angle of inclination of the inclined recesses of the internal flow barrier is referred to as the internal angle of inclination, and the angle of inclination of the inclined recesses of the external flow barrier is referred to as the external angle of inclination.

[0065] According to one embodiment, the internal inclination angle of the primary magnetic pole ôIp 1 can be defined by the relation: 51pl = k\p\ X ypl, with k\p\ a constant, with k[p\ being between 0.5 and 0.9 (inclusive), preferably between 0.7 and 0.9 (inclusive).

[0066] Furthermore, the external inclination angle of the primary magnetic pole ô2pl can be defined by the relation: <52 / tl = x <51pl with kip\ a constant, with k^p\ being between 0.4 and 0.9 (inclusive), preferably between 0.5 and 0.65 (inclusive).

[0067] According to one embodiment, the internal inclination angle of the secondary magnetic pole ôlp2 can be defined by the relation: 51p2 = k\p2 X yp2, with k]p2 a constant, with k\pz being between 0.5 and 0.9 (inclusive), preferably between 0.7 and 0.9 (inclusive).

[0068] Furthermore, the external inclination angle of the primary magnetic pole Ô2p2 can be defined by the relation: d2p2 ~ ^^2 x Ôlp2 with ^2^2 a constant, with ^2 / ,2 being between 0.4 and 0.9 (inclusive), preferably between 0.5 and 0.7 (inclusive).

[0069] These angular ranges allow for optimization of the magnet arrangement, generating reduced torque ripples while maximizing the torque and power of the high-speed machine.

[0070] The opening angle of the inclined recesses of the internal or external flow barrier is defined as the angle formed between two straight lines, each straight line passing through the midpoint of two sides of an inclined recess (without taking into account any additional shapes at the ends of the recess). The two sides of the inclined recess are the one facing the periphery of the rotor and the one facing the center of the rotor. These two sides correspond to the shorter sides of the recesses. For the embodiment in which the recesses have a substantially rectangular shape (excluding any additional shapes) in the transverse plane of the rotor, the two sides correspond to the thickness of the recesses. In other words, the opening angle of the external flow barrier corresponds to the angle formed by the segments of the V, and the opening angle of the internal flow barrier corresponds to the angle formed by the opposite segments of the U.

[0071] According to one embodiment, the opening angle of the inclined recesses of the internal flow barrier can be strictly less than the opening angle of the inclined recesses of the external flow barrier.

[0072] According to one embodiment, the opening angle of the inclined recesses of the internal flux barrier can be acute, i.e. less than 90°. Such an angle makes it possible to increase the size of the lateral recesses, and where applicable the size of any lateral permanent magnets, which makes it possible to maximize the torque of the electric machine.

[0073] According to one embodiment, the opening angle of the inclined recesses of the external flux barrier can be obtuse or right, i.e. greater than or equal to 90°. Such an angle makes it possible to increase the size of the lateral recesses, and where applicable the size of any lateral permanent magnets, which makes it possible to maximize the torque of the electric machine.

[0074] An internal radius can be defined to designate the radius of the internal flow barrier, the internal radius being the distance between the center of the rotor and the side of the central recess of the internal flow barrier facing the center of the rotor, this internal radius being defined on the radius perpendicular to the central recess of the internal flow barrier.

[0075] The ratio between the internal radius and the rotor radius can be between 0.3 and 0.8 (inclusive terminals) and preferably between 0.55 and 0.7 (inclusive terminals) to optimize the torque and power of the electric machine.

[0076] An external radius can be defined to designate the radius of the external flux barrier, the external radius being the distance between the center of the rotor and a projection of the point closest to the center of the rotor of an inclined recess of the external flux barrier onto the radius perpendicular to the central recess of the internal flux barrier.

[0077] According to one embodiment, a relationship can be defined between the internal radius rint, the rotor radius r and the external radius rext:

[0078] r -r. +k(rr. ) ' ext ~ ' int ^Kr\r ' int)

[0079] With kr being a coefficient, kr can be between 0.2 and 0.8 (inclusive terminals), preferably between 0.35 and 0.55 (inclusive terminals) to optimize the magnetic performance of the electric machine.

[0080] The magnetic poles may include weight-relieving recesses arranged between the external flux barrier and the periphery of the rotor. In other words, each magnetic pole may include a weight-relieving recess between the external flux barrier and the periphery of the rotor. These weight-relieving recesses are not intended to house permanent magnets. They allow for a reduction in the rotor mass and a reduction in the mechanical stresses on the rotor body at high speed, and for maximizing the rotor performance density. These lightening zones do not create local saturation between them and the V-shaped flow barrier, which is not the case with the additional recesses according to the invention, creating new air zones.

[0081] Advantageously, the weight-relieving recess can have a substantially triangular shape. Preferably, two sides of the triangular shape can be parallel to the inclined recesses of the external flux barrier. Thus, the spacing between the weight-relieving recess and the inclined recesses is virtually constant, which allows for good mechanical stability of the rotor body without loss of electromagnetic performance. Furthermore, one vertex of the triangle can be positioned on the radius perpendicular to the central recess of the internal flux barrier, and the radius perpendicular to the central recess of the internal flux barrier can optionally be an axis of symmetry of the triangle. In addition, the third side can face the periphery of the rotor, being parallel to the tangent of the rotor periphery at the point of intersection with the radius perpendicular to the central recess of the internal flux barrier.

[0082] Alternatively, the weight-relieving recess may have other shapes, such as circular, rectangular, a portion of a disk shape for example with the face near the periphery of the rotor being an arc of a circle with a radius identical or different from the radius of the periphery of the rotor, etc.

[0083] The rotor can comprise p pairs of magnetic poles (or 2xp magnetic poles). Advantageously, p can be between 2 and 9, and preferably p is between 3 and 6, and preferably equals 4.

[0084] According to the present invention, two additional recesses are added to the rotor, arranged between the recesses of the external flux barrier and the outer edge of the rotor body, to modify the trajectory of the magnetic fluxes emitted by said permanent magnets in the rotor.

[0085] These additional recesses may each have a circular, oval, or ovoid shape, or be triangular, or have four or more sides, including rounded edges, such as a square, trapezoid, rhombus, or rectangle. They may have the same shape or a different shape, the same dimensions, or different dimensions.

[0086] They can be arranged on either side of the radius R mentioned above, in particular inclined to each other, and preferably arranged symmetrically with respect to said radius.

[0087] The recesses, which are the subject of the invention, on the whole of the rotor (described by a solid disk of external diameter which is that of the rotor) can together represent 0.25% to 5% of the surface area of ​​the section of the rotor.

[0088] At least one of the two additional recesses may have a portion of its edge that runs along the outer edge of the inclined recess of the nearest external flow barrier

[0089] At least one of the two additional recesses may have a portion of its edge that runs along the outer edge of the rotor body.

[0090] The two additional recesses can be inclined relative to each other, and their opening angle (y)> defined similarly to the opening angles a,B mentioned above can be obtuse or right, and preferably be identical or close to the opening angle B of the inclined recesses of the external flow barrier.

[0091] At least one of the two additional recesses may be disposed at a distance from a portion of the outer edge of the inclined recess of the external flow barrier and along said portion, in particular over at least 10 or 25% or 50% of the length of said outer edge.

[0092] The invention also relates to an electrical machine comprising a stator and a rotor as described above. The rotor is arranged inside the stator. Conventionally, the stator includes windings to generate a rotating magnetic field capable of rotating the rotor relative to the stator. The windings can be inserted into axial slots in the stator, the slots being arranged circumferentially within the stator.

[0093] According to one embodiment, the electric machine is a synchronous reluctance machine assisted by permanent magnets.

[0094] Figures 1a and 1b, described together, illustrate schematically and without limitation an electric machine rotor according to a first comparative example (comparative example 1) corresponding to a rotor embodiment according to the aforementioned patent application WO2022 / 128541 (comparative example 1). It is a view of a cross-section perpendicular to the rotor axis: Figure 1 represents a quarter of the rotor corresponding to two magnetic poles of a rotor with four pairs of magnetic poles; the other pairs of magnetic poles are deduced by circular repetition of the partial view. In this Figure 1, no permanent magnet is shown; the different embodiments of the permanent magnet arrangement are illustrated and detailed in Figures 3 to 8. The rotor 1 is formed from a stack of laminations connected to a rotor shaft 4. The illustrated portion of the rotor 1 comprises two magnetic poles 16, 16'.Each magnetic pole 16, 16' comprises two flux barriers: an internal flux barrier 2 and an external flux barrier 3. The internal flux barrier 2 comprises a central recess 5, and two inclined recesses 6 on either side of the central recess 5; these three recesses 5, 6 form a flux barrier having an essentially U-shaped form. A radial magnetic bridge 17 is provided between the central recess 5 and each inclined recess 6. A tangential bridge. 18 is provided between each inclined recess 6 and the periphery of the rotor 1. The external flux barrier 3 comprises two inclined recesses 7, these two recesses 7 forming a flux barrier having a substantially V-shape. A radial magnetic bridge 19 is provided between the inclined recesses 7. A tangential bridge 20 is provided between each inclined recess 7 and the periphery of the rotor 1.

[0095] In addition, the rotor includes an optional weight-relieving recess 8, having substantially a triangular shape and disposed between the external flow barrier 3 and the periphery of the rotor 1. The weight-relieving recess 8 has two sides parallel to the lateral recesses 7 of the external flow barrier 3, the third side faces the periphery of the rotor 1. The rotor may include other weight-relieving recesses, such as the weight-relieving recesses 15 provided between the rotor shaft 4 and the internal flow barrier 2.

[0096] In the embodiment of [Fig. 1a], each recess 5, 6, or 7 of the internal and external flow barriers is substantially rectangular in shape and includes two additional shapes at its ends. These are the additional shapes 10 for the central recess 5, the additional shapes 9 for the inclined recesses 6, and the additional shapes 11 for the inclined recesses 7. These additional shapes 9, 10, and 11 are L-shaped, rounded rectangular, and segment-shaped.

[0097] Figure 1b represents the radius R, which is perpendicular to the central recess 5. The radius R is an axis of symmetry of the central recess 5. Furthermore, in this figure, the lines D6 and D7 are drawn. The lines D6 pass through the midpoints of two opposite sides of the inclined recesses 6 (not counting the additional shapes 9). The lines D7 pass through the midpoints of two opposite sides of the inclined recesses 7 (not counting the additional shapes 11). The opening angle of the inclined recesses 6 of the internal flow barrier is denoted α; it is defined by the angle formed by the two lines D6, this angle α is an acute angle. The opening angle of the inclined recesses 7 of the external flow barrier is denoted θ; it is defined by the angle formed by the two lines D7, this angle θ is an obtuse angle. Furthermore, we have the following relationship: a<[3.

[0098] In the illustrated embodiment, the magnetic pole is symmetrical with respect to the radius R. In this case, angle α is formed by a first angle of inclination αi and a second angle of inclination α2. Each of angles αi and α2 is defined between a line D6 and the radius R, with αi = α2 (which implies that the inclined recesses α6 are symmetrical). Furthermore, angle θ3 is formed by a first angle of inclination θ31 and a second angle of inclination θ32. Each of angles θ31 and θ32 is defined between a line D7 and the radius R, with θ31 = θ32 (which implies that the inclined recesses θ7 are symmetrical).

[0099] Furthermore, the two magnetic poles 16 and 16' are different: the angles of the inclined recesses of the flux barriers of the magnetic pole 16 are greater than the angles of the inclined recesses of the flux barriers of the magnetic pole 16'. In addition, the additional shapes 10, 11 are different between the magnetic poles 16 and 16'.

[0100] Furthermore, here, the radius R is an axis of symmetry of the relief recess 8.

[0101] Alternatively, all the magnetic poles of the rotor 1 can be identical.

[0102] Fig. 2 represents a first example of an embodiment according to the invention (example 1) of a portion of a rotor, here a quarter of a rotor in a manner analogous to the representation according to Fig. 1a. The characteristics already described in Figure 1, concerning the design of the internal flow barrier 2 and the external flow barrier 3, will not be described again. Only additional, different or modified characteristics of the rotor in Figure 1 will be described: Here, there is no weight-relieving recess 8 (although this recess can be provided optionally, as described later with reference to [Fig. 14]). Two additional recesses 20 are provided in the area of ​​the rotor 1 delimited on one side by the external flow barrier 3 defined by the two recesses 7 and on the other side by the outer edge 21 of the rotor body 1. They are triangular in shape with rounded edges and are identical in size and shape. They are arranged on either side of the radius R, preferably symmetrically with respect to this radius, like the recesses 7. One of their edges runs along the outer edge 21 of the rotor, and another of their edges runs along the outer edge 71 of the nearest recess 7. The triangular shape shown here is essentially isosceles, but could just as easily be equilateral, rectangular, or otherwise.

[0103] The surface area of ​​these additional recesses throughout the rotor represents 0.25% to 5% of the total section of the rotor.

[0104] The surface area of ​​these additional recesses can also represent, for comparison purposes, from 5% to 50% of the surface area of ​​the recesses 7 of the external flow barrier.

[0105] The presence of these additional recesses 20 will modify the magnetic flux generated by the magnets of the magnetic pole in question, which can be visualized using [Fig. 15]: on the left, flux lines are shown for a portion of the rotor according to the comparative example (Figure 1), and on the right, the flux lines are shown when the two additional recesses are provided according to Example 1 of the invention ([Fig. 2]). The presence of the air zones creates at least two local saturations (darker areas in the figure), one near the magnet and the other near the outer radius of the rotor. These Saturations create toothing in the rotor, which helps to reduce magnetic flux and voltage harmonics.

[0106] Figure 3 shows a second embodiment of the invention (Example 2): All other things being equal with respect to the first example shown in Figure 2, the additional recesses 20' here have a more trapezoidal shape, with rounded edges. Their longer sides (corresponding to the larger base of the trapezoid) 201 run along the outer edge 7 of the recesses 7, and one of their shorter sides (corresponding to the smaller base of the trapezoid) runs along the outer edge 21 of the rotor. Their surfaces are larger than the surfaces of the additional recesses 20 shown in Figure 1, and they are inclined relative to each other, along the length of their longer edges 201 (corresponding to the larger base of the trapezoid), at an opening angle Y that may be similar or identical to the opening angle B between the recesses 7.

[0107] Figure 14 shows a rotor plate according to a third embodiment (Example 3) of the invention: all other things being equal, it adds to the rotor of Example 2 (according to Figure 3) a weight-reducing recess 8', 8" arranged between each pair of additional recesses 20. These weight-reducing recesses may or may not be identical to each other. In Example 3, they are arranged in the same way with respect to the recesses 20; they are both circular, but one (8') has a larger diameter than the other (8"). Alternatively, the weight-reducing recesses may be identical and / or arranged differently with respect to the other recesses and / or non-circular in shape (oval, for example). As their name indicates, their function is solely to lighten the rotor, unlike the recesses 20.

[0108] Comparative example 2 is shown in [Fig. 16]: all other things being equal, it represents a portion of rotor similar to that of the comparative example according to [Fig.laa], with the difference that here there is no weight-reduction recess 8.

[0109] Figures 4 to 7 represent, through different graphs, the no-load performance of the electric machine equipped with the rotor according to comparative example 2 of [Fig. 16] (curves Cl) and according to example 1 according to the invention (curves C2):

[0110] The graph in [Fig.4] represents the phase-to-phase induced voltage curve Cl of the electric machine integrating the rotor according to comparative example 2 ([Fig.16]) and the curve C2 of that integrating the rotor according to the first example ([Fig.2]): it can be seen that by the appropriate placement of the two additional recesses, it is possible to modulate the waveform of the induced voltage, with a curve Cl smoother than the curve C2 and with a lowered maximum peak.

[0111] The graph in [Fig. 5] represents the Fourier series decomposition of the voltage Induced between phases. For each harmonic, the right-hand bar of the bar graph corresponds to comparative example 2 ([Fig. 16]) and the left-hand bar to that of the first example ([Fig.2]): we see the very significant contribution of the additional recesses 20 on the harmonics 5, 11 and 13, which leads to facilitating the control of the electrical machine.

[0112] The graph in [Fig. 6] represents the maximum induced phase-to-phase voltage as a function of motor speed (rotor speed), using the same conventions as for graph 4: curve C1 corresponds to comparative example 2 ([Fig. 16]) and curve C2 to the first example (example 1, [Fig. 2]) according to the invention. It can be seen that curve C2 is below curve C1, and this is all the more pronounced as the rotor speed increases.

[0113] The graph in [Fig. 7] represents the fundamental of the induced voltage as a function of the motor speed, with the same conventions as for graphs 4 and 6: the curve Cl corresponds to comparative example 2 ([Fig. 16]) and the curve C2 to the first example according to the invention (example 1, [Fig. 2]). It can be seen that the curves are almost superimposed.

[0114] What can be deduced from the graphs in [Fig. 6] and [Fig. 7] is that with the invention:

[0115] - we manage to significantly reduce the peak induced open-circuit voltage, here by approximately 10%, ([Fig.6]), which is favorable to a rapid increase in the speed of the electric machine- - while the corresponding voltage drop ([Fig.7]) is very small, here less than 1%, which is favorable to obtaining a high torque.

[0116] The solution according to the invention, compared with the prior art, therefore makes it possible to lower the no-load voltage peak while maintaining a high effective voltage value, which guarantees better performance in both torque / power and maximum speed ramp-up of the electric machine.

[0117] Figures 8 to 11 represent, through different graphs, the load performance of the electric machine equipped with the rotor according to comparative example 2 ([Fig.16]) (curves Cl) and according to the first example (example 1, [Fig.2]) according to the invention (curves C2): Figure 8 shows that the mechanical torque envelope as a function of rotor speed is close for both examples. Figure 9 shows that the mechanical power envelope as a function of rotational speed is also close for both examples, with the advantage, for the first example according to the invention (curve C2) of being able to ensure operation at very high rotational speeds, beyond 12000 rpm and even in the vicinity of 15000 rpm, rotational speed values ​​inaccessible with the comparative example (curve C1). Figure 10 includes: - a graph on the right representing the electromagnetic torque ripple (“EM Torque ripple”) as a function of the peak current (“Ipeak”), in amperes (A) for the machine equipped with the rotor according to comparative example 2 ([Fig. 16]) and the rotor according to the invention (example 1, [Fig.2]): we see that the C2 curve, for a current of 100A, starts above the Cl curve, then it crosses the Cl curve for an intensity of about 150 A and beyond this value, it drops much more than the Cl curve, with a break in the curve around 230 A. We see that around 350 to 450 A, the Cl curve reaches high values, around 17%, while the C2 curve is only at 10%: we thus see that with the invention, we very significantly reduce the “ripple” over a very wide current range.

[0118] - a graph on the left, representing the average electromagnetic torque (“EM Mean Torque » in English) expressed in Nm, as a function of the peak current (“Ipeak”), in amperes (A) for the machine equipped with the rotor according to comparative example 2 ([Fig. 16]) and the rotor according to the invention (example 1, [Fig.2]): we see that the two curves Cl and C2 are almost superimposed, the curve C2 standing out from the curve Cl and being slightly below it when the current reaches 250 A.

[0119] What can be deduced from these two graphs is that the example according to the invention slightly reduces the average torque at maximum current by 2-3%, this loss being largely acceptable in view of the gain observed on the torque ripples of the order of 40%.

[0120] Figure 11 shows a graph comparing the efficiency of two electrical machines as a function of machine speed (rpm) and mechanical torque (in Nm) for the machine equipped with the rotor according to comparative example 2 (Fig. 16) (C1, solid curve) and the rotor according to example 1 (Fig. 2) of the invention (C2, dashed curve). The circled areas Z are impacted areas.

[0121] It follows that the example according to the invention makes it possible to improve the efficiency of the machine from 9000 rpm, with gains of up to 3, or even 5 points of efficiency.

[0122] However, a decrease in efficiency of approximately 1 percentage point is observed at low speed and high load. This decrease in efficiency in this range is largely compensated by the gain observed at high speed.

[0123] From this series of figures, we see that the maximum power of the electric machine equipped with the rotor according to the invention remains unchanged, but that we have been able to gain about 10% on the maximum speed of the electric machine, which is very significant.

[0124] Figures 12 and 13 concern the torque / power envelope graphs referred to the wheels of a vehicle equipped with an electric drive machine described above, with the rotor according to comparative example 2 - [Fig. 16] (curve Cl) and according to example l - [Fig. 2] of the invention (curve C2): [Fig. 12] relates to the torque envelope and the [Fig. 13] to the power envelope, as a function of the wheel speed in revolutions per minute. From these two figures, we can see that with the invention we have gained about 10% on the maximum speed of the electric machine, and that we have been able to increase the torque on the road by about 10% at the same maximum speed of the vehicle.

Claims

Demands

1. Rotor for an electric machine, said rotor comprising a rotor body (1) formed by a stack of laminations, and a plurality of pairs of magnetic poles (16, 16'), each magnetic pole (16, 16') being composed of at least two flux barriers, including: - an internal flux barrier (2) comprising two recesses inclined (6) to each other and disposed on either side of a central recess (5), said central recess (5) being perpendicular to a radius (R) of the rotor, - an external flux barrier (3) comprising two recesses inclined (7) to each other and disposed, on either side of said radius (R), between the central recess (5) of the internal flux barrier (2) and the outer edge (21) of the rotor body (1), - and at least one permanent magnet (12) positioned in at least one recess (5,6,7) of each of the two said flux barriers (2, 3), characterized in that at least one of the magnetic poles, in particular each magnetic pole,includes two additional recesses (20) arranged between the recesses (7) of the external flux barrier (3) and the outer edge (21) of the rotor body (1) to modify the trajectory of the magnetic fluxes emitted by said permanent magnets (12) in the rotor.

2. Rotor for electric machine according to claim 1, characterized in that the additional recesses (20) each have a circular or oval or ovoid, or oblong, or triangular or polygonal shape, in particular with four or more sides, in particular with rounded edges, in particular a square, a trapezoid, a rhombus, a rectangle.

3. Rotor for electric machine according to any one of the preceding claims, characterized in that the two additional recesses (20) of a magnetic pole have the same shape or a different shape, the same dimensions, or different dimensions.

4. Rotor for an electric machine according to any one of the preceding claims, characterized in that the two additional recesses (20) of a magnetic pole are arranged on either side of said radius (R), in particular inclined to one another with respect to to the other, and preferably arranged symmetrically with respect to said radius (R).

5. Rotor for electric machine according to any one of the preceding claims, characterized in that the additional recesses (20) over the whole rotor together represent 0.25% to 5% of the surface area of ​​the rotor cross-section.

6. A rotor for an electric machine according to any one of the preceding claims, characterized in that at least one of the two additional recesses (20) has a portion of its edge that runs along the outer edge (71) of the inclined recess (7) of the nearest external flux barrier (3).

7. Rotor for electric machine according to any one of the preceding claims, characterized in that at least one of the two additional recesses (20) has a portion of its edge which runs along the outer edge (21) of the rotor body.

8. Rotor for electric machine according to any one of the preceding claims, characterized in that the two additional recesses of a magnetic pole (20) are inclined relative to each other, and in that their opening angle (y) is obtuse or right, and preferably identical or close to the opening angle (B) of the inclined recesses (7) of the external flux barrier (3).

9. Rotor for electric machine according to any one of the preceding claims, characterized in that at least one of the two additional recesses (20) of a magnetic pole is disposed at a distance from and along a portion of the outer edge (71) of the inclined recess (7) of the external flux barrier (3), in particular over at least 10% to 50% of the length of said outer edge.

10. Rotor according to any one of the preceding claims, characterized in that at least one of the magnetic poles, in particular each magnetic pole also comprises a lightening recess (8) between the recesses (7) of the external flux barrier (3) and the outer edge (21) of the rotor body (1), said lightening recess (8) preferably having a substantially triangular shape, the two additional recesses (20) being arranged on either side of said lightening recess (8).

11. Electric machine characterized in that it comprises a stator and a rotor (1) according to any one of the preceding claims, said rotor being housed inside said stator.

12. An electrical machine according to the preceding claim, characterized in that said stator comprises a plurality of radial slots arranged circumferentially along said stator.

13. Electric machine according to any one of claims 11 or 12, characterized in that said electric machine is a synchronous-reluctant electric machine assisted by permanent magnets.

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