Permanent-magnet electric machine

Abstract

The invention relates to a permanent-magnet electric machine (100), in particular of the synchronous type, in particular for a motor vehicle, the electric machine comprising: - a stator; - and a rotor (2) comprising a rotor body (3) and, for each pole, a pair of main permanent magnets (5) arranged in a V shape with the point of the V positioned toward the center of the rotor (2), these main permanent magnets (5) being placed respectively in main recesses (6) in the rotor body (3), each main recess (6) comprising, in cross-section, an end cavity (7) extending longitudinally in line with the magnet toward an outer periphery (9) of the rotor (2), the rotor body (3) having a bridge of material (10) located radially between the end cavity (7) of the main recess (6) and the outer periphery (9) of the rotor (2), the bridge of material (10) having a thickness (E) which is measured radially in a plane of the cross-section, the thickness increasing toward the middle of the V, in particular with a ratio (W2 / W1) of the largest thickness (W2) of the bridge of material (10) to the smallest thickness (W1) of the bridge of material (10) of between 3 and 5.

Description

[0001] DESCRIPTION

[0002] Title: Permanent Magnet Electric Machine

[0003] [1] The invention relates in particular to an electric machine with permanent magnets.

[0004] [2] Patent application WO2022064614 discloses an electrical machine comprising a plurality of permanent magnets with a main magnetic pole which are magnetized in a direction orthogonal to the main surface of a rear cylinder head, and are arranged in an array such that their magnetization directions alternate.

[0005] [3] The invention aims in particular to further improve electrical machines, in particular by making it possible to reduce unwanted harmonics and noise.

[0006] [4] The invention thus relates to a permanent magnet electric machine, in particular of the synchronous type, particularly for a motor vehicle, the electric machine comprising: a stator, a rotor comprising a rotor body and, for each pole, a pair of main permanent magnets arranged in a V with the point of the V placed on the side of the center of the rotor, these main permanent magnets being placed respectively in main housings in the rotor body, each main housing comprising in cross-section (namely the section taken in a plane perpendicular to the axis of the rotor) an end recess extending in the longitudinal continuation of the magnet, in the direction of an outer periphery of the rotor, the rotor body having a material bridge located radially between the end recess of the main housing and the outer periphery of the rotor, the material bridge having a thickness, the thickness being measured radially,in a cross-sectional plane, thickness which increases towards the middle of the V, notably with a ratio (W2 / W1) between the greatest thickness (W2) of the material bridge and the smallest thickness (W1) of the material bridge which is between 3 and 5.

[0007] [5] The material bridge is thus formed between the end recess of the main magnet housing and an air gap which is defined by the space between the rotor and the stator of the rotating electrical machine.

[0008] [6] Thanks to the invention, the harmonics of the no-load electromotive force and, consequently, the phase current harmonics are significantly reduced when the machine is supplied with sinusoidal voltages. This makes it possible to reduce electromagnetic losses and noise. Indeed, leakage flux at the ends of the magnets is avoided, thus preventing performance degradation. This is an advantage compared to configurations of constant-thickness material bridges.

[0009] [7] According to one aspect of the invention, the material bridge starts with the smallest thickness (W1) towards the largest thickness (W2) when approaching the middle of the V-shape.

[0010] [8] According to one aspect of the invention, the smallest thickness (W1) of the material bridge is between 1 and 1.5 mm.

[0011] [9] According to one aspect of the invention, the greatest thickness (W2) of the material bridge is between 3 and 7.5 mm.

[0012]

[0010] According to one aspect of the invention, the thickness of the material bridge exhibits a linear growth, going towards the middle of the V-shape.

[0013]

[0011] Alternatively, the thickness of the material bridge exhibits an evolution, going towards the middle of the V-shape, which is non-linear.

[0014]

[0012] For example, the thickness of the material bridge shows an evolution, going towards the middle of the V-shape, which follows a curve that is piecewise linear.

[0015]

[0013] Alternatively, the thickness of the material bridge has an evolution, going towards the middle of the V shape, which follows a curve with at least one rounding.

[0016]

[0014] According to one aspect of the invention, in cross-section, the end recess has a substantially triangular shape.

[0017]

[0015] Any other shape is possible, which is compatible with the evolution of the thickness.

[0018]

[0016] According to one aspect of the invention, the V-shaped main permanent magnets have a mirror axis of symmetry, this axis of symmetry being a radius of the rotor.

[0019]

[0017] According to one aspect of the invention, for each pole of the rotor, the rotor body comprises, in addition to the main permanent magnets, at least one pair of secondary permanent magnets, preferably also arranged in a V.

[0020]

[0018] According to one aspect of the invention, the V-shape of the secondary permanent magnets is inside the V-shape of the primary permanent magnets.

[0021]

[0019] According to one aspect of the invention, the V-shape of the secondary permanent magnets and the V-shape of the main permanent magnets have the same mirror axis of symmetry, this axis of symmetry being a radius of the rotor.

[0022]

[0020] According to one aspect of the invention, the secondary permanent magnets are placed in respective secondary housings of the rotor body.

[0021] According to one aspect of the invention, the secondary housing comprises, in cross-section, an end recess extending in the longitudinal direction of the magnet, towards an outer periphery of the rotor, the rotor body having a material bridge located radially between the end recess of the secondary housing and the outer periphery of the rotor, the material bridge having a thickness that increases towards the middle of the V, in particular with a ratio between the greatest thickness of the material bridge and the smallest thickness of the material bridge that is between 3 and 5.

[0023]

[0022] According to one aspect of the invention, the end recess of a main housing and the end recess of a secondary housing (which are on the same side of the respective V-shapes) overlap radially, in particular over an angular sector of overlap between 0.5° and 3°, being for example substantially equal to 2°.

[0024]

[0023] In the present invention, radial overlap means that there is an angular sector of the rotor which cuts, radially in succession, the end recess of the main housing and the end recess of the secondary housing.

[0025]

[0024] According to another embodiment of the invention, the end recess of a main housing and the end recess of a secondary housing (which are on the same side of the respective V-shapes) are tangent to the same radius of the rotor.

[0026]

[0025] Advantageously, even a slight radial overlap allows for a gradual transition from one end recess to the other. Conversely, in the absence of overlap, a break can occur when moving from an end recess of a larger V shape to an end recess of the other V shape, generating a break and therefore undesirable harmonics.

[0027]

[0026] According to one aspect of the invention, the end recess of the larger V has a point directed towards the end recess of the smaller V.

[0028]

[0027] According to one aspect of the invention, the tip protrudes beyond a longitudinal flank of the main magnet housing.

[0029]

[0028] According to another aspect of the invention, the end recess of a main housing radially overlaps a slot (which is notably empty, and therefore without a magnet) in the rotor body, in particular over an angular sector of overlap between 0.5° and 3°, being for example substantially equal to 2°.

[0030]

[0029] This ensures the smoothing function of the electromotive force of the electric machine.

[0030] The outer circumference of the rotor forms an air gap with the stator of the electric machine.

[0031]

[0031] The invention also relates to a rotor comprising a rotor body and, for each pole, a pair of main permanent magnets arranged in a V with the tip of the

[0032] V placed on the center side of the rotor, these main permanent magnets being placed respectively in main housings in the rotor body, each main housing comprising in cross section (namely the section taken in a plane perpendicular to the axis of the rotor) an end recess extending in the longitudinal extension of the magnet, in the direction of an outer periphery of the rotor, the rotor body having a material bridge located radially between the end recess of the main housing and the outer periphery of the rotor, the material bridge having a thickness (the thickness being measured radially, in the plane of the cross section) which is increasing towards the middle of the V, in particular with a ratio (W2 / W1) between the greatest thickness (W2) of the material bridge and the smallest thickness (W1) of the material bridge which is between 3 and 5.

[0033]

[0032] The invention further relates to a rotor comprising a rotor body and, for each pole, a pair of main permanent magnets arranged in a V with the tip of the

[0034] V placed on the center side of the rotor, these main permanent magnets being placed respectively in main housings in the rotor body, each main housing comprising in cross-section (namely the section taken in a plane perpendicular to the axis of the rotor) an end recess extending in the longitudinal direction of the magnet, towards an outer periphery of the rotor, and, for each pole of the rotor, the rotor body comprises, in addition to the main permanent magnets, at least one pair of secondary permanent magnets also arranged in a V, the V shape of the secondary permanent magnets being inside the V shape of the main permanent magnets, the secondary permanent magnets being placed in respective secondary housings of the rotor body, the secondary housing comprising, in cross-section, an end recess extending in the longitudinal direction of the magnet,towards an outer periphery of the rotor, the end recess of a primary housing and the end recess of a secondary housing (which are on the same side of the respective V-shapes) overlap radially, in particular over an angular sector of overlap between 0.5° and 3°, being for example substantially equal to 2°.

[0035]

[0033] According to one aspect of the invention, the permanent magnet synchronous electric machine comprises at least two pole pairs, in particular three or four pole pairs. The machine can be configured as an electric motor, in particular.

[0034] Other features, details, and advantages of the invention will become clearer upon reading the following description, on the one hand, and several illustrative and non-limiting examples of embodiments given with reference to the accompanying schematic drawings, on the other hand, in which:

[0036]

[0035] [Fig 1] Figure 1 represents very schematically, in cross-section, an electric machine with permanent magnets according to an example of an embodiment of the invention;

[0037]

[0036] [Fig. 2] Figure 2 is a detailed view of the electrical machine of Figure 1;

[0038]

[0037] [Fig. 3] Figure 3 is a view similar to Figure 1,

[0039]

[0038] [Fig. 4] Figure 4 shows schematic graphs called GRAPH-1 and

[0040] GRAPH-2 containing curves representing no-load electromotive forces with respect to an electrical machine according to the state of the art and no-load electromotive forces with respect to an electrical machine comprising the invention.

[0041]

[0039] The features, variants, and different embodiments of the invention can be combined in various ways, provided they are not incompatible or mutually exclusive. In particular, variants of the invention may be conceived comprising only a selection of features, described hereafter in isolation from the other described features, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from the prior art.

[0042]

[0040] Figure 1 shows, on an angular sector only, a synchronous permanent magnet electric machine 100, here with 3 pole pairs, comprising a stator 1 and a rotor 2.

[0043]

[0041] The rotor 2 comprises a rotor body 3 and, for each pole, a pair of main permanent magnets 5 arranged in a V with the tip of the V placed on the center side of the rotor 2, these main permanent magnets 5 being placed respectively in main housings 6 in the rotor body 3.

[0044]

[0042] Each main housing 6 comprises in cross-section, namely a section taken in a plane perpendicular to the axis XR of the rotor 2, an end recess 7 extending in the longitudinal extension, here an axis ML, of the main permanent magnet 5, in the direction of an outer periphery 9 of the rotor 2, the rotor body 3 having a material bridge 10 located radially between the end recess 7 of the main housing 6 and the outer periphery 9 of the rotor 2.

[0045]

[0043] The material bridge 10 has a thickness E (the thickness being measured radially, in the plane of the cross section, namely a plane perpendicular to the axis XR) which is increasing towards the middle of the V, with a ratio (W2 / W1) between the greatest thickness W2 of the material bridge 10 and the smallest thickness W1 of the material bridge 10 which is between 3 and 5.

[0046]

[0044] The material bridge 10 is thus formed between the end recess 7 of the main housing 6 of the magnet and an air gap 50 which is defined by the space between the rotor 2 and the stator 1 of the rotating electrical machine 100.

[0047]

[0045] The material bridge 10 starts with the smallest thickness W1 towards the largest thickness W2 when approaching the middle of the V shape, the middle which corresponds to an axis AS of mirror symmetry of the V shape. This axis AS of symmetry corresponds to a radius of the rotor 2.

[0048]

[0046] The smallest thickness W1 of the material bridge 10 is between 1 and 1.5 mm.

[0049]

[0047] The greatest thickness W2 of the material bridge 10 is between 3 and 7.5 mm.

[0050]

[0048] The thickness E of the material bridge 10 exhibits a growth, going towards the middle of the V-shape, which is linear.

[0051]

[0049] Alternatively, the thickness E of the material bridge 10 exhibits a non-linear evolution towards the middle of the V-shape. For example, the thickness of the material bridge 10 exhibits a piecewise linear evolution towards the middle of the V-shape.

[0052]

[0050] In cross-section, the end recess 7 has a substantially triangular shape.

[0053]

[0051] For each pole of the rotor 2, the rotor body 3 comprises, in addition to the main permanent magnets 5, at least one pair of secondary permanent magnets 12, also arranged in V.

[0054]

[0052] The V-shape of the secondary permanent magnets 12 is inside the V-shape of the primary permanent magnets 5.

[0055]

[0053] The V-shape of the secondary permanent magnets 12 and the V-shape of the main permanent magnets 5 have the same axis of mirror symmetry AS.

[0056]

[0054] The secondary permanent magnets 12 are placed in respective secondary housings 14 of the rotor body 3.

[0057]

[0055] The secondary housing 14 comprises, in cross-section, an end recess 15 extending in the longitudinal extension of the magnet 12, towards an outer periphery 9 of the rotor 2, the rotor body 3 having a material bridge 17 located radially between the end recess 15 of the secondary housing 15 and the outer periphery 9 of the rotor 2, the material bridge 17 having a thickness which is increasing towards the middle of the V, in particular with a ratio between the greatest thickness W4 of the material bridge and the smallest thickness W3 of the material bridge 17 which is between 3 and 5.

[0058]

[0056] The end recess 7 of the main housing 6 and the end recess 15 of the secondary housing 14 (which are on the same side of the respective V-shaped forms) overlap radially, in particular on an angular sector ST of overlap between 0.5° and 3°, being for example substantially equal to 2°.

[0059]

[0057] In the present invention, radial overlap means that there is an angular sector ST of the rotor 2 which cuts, radially in succession, the end recess of the main housing 6 and the end recess of the secondary housing.

[0060]

[0058] Advantageously, even a slight radial overlap allows for a gradual transition from one end recess to the other. Conversely, in the absence of overlap, a break can occur when moving from an end recess of a larger V shape to an end recess of the other V shape, generating a break and therefore undesirable harmonics.

[0061]

[0059] The end recess 7 of the larger V has a point 19 directed towards the end recess 15 of the smaller V.

[0062]

[0060] The tip 19 protrudes beyond a longitudinal flank 22 of the main housing 6 of the magnet.

[0063]

[0061] In another embodiment of the invention (not illustrated), the end recess 7 of the main housing 6 radially overlaps a slot which is in particular empty, and therefore without a magnet, in the rotor body 3, in particular over an angular sector of overlap between 0.5° and 3°, being for example substantially equal to 2°.

[0064]

[0062] This ensures the smoothing function of the electromotive force of the electric machine.

[0065]

[0063] Thanks to the invention, the harmonics of the no-load electromotive force and, consequently, the phase current harmonics are significantly reduced when the machine is supplied with sinusoidal voltages. This makes it possible to reduce electromagnetic losses and noise. Indeed, leakage flux at the ends of the magnets 5 is avoided, thus preventing performance degradation. This is an advantage compared to configurations of constant-thickness material bridges.

[0066]

[0064] The invention thus makes it possible to obtain sinusoidal (or quasi-sinusoidal) phase currents following a reduction / suppression of harmonic currents of a higher order than the fundamental, which are the source of undesirable eddy currents.

[0065] This is illustrated in the graphs labeled GRAPH-1 and GRAPH-2 in Figure 4.

[0067]

[0066] Graph GRAPH-1 shows no-load electromotive forces (Phase U, Phase V, Phase W) and ideal sinusoidal electromotive forces (Sinus U, Sinus V, Sinus W) of an electrical machine according to the prior art (i.e. including a non-optimized design).

[0068]

[0067] Graph GRAPH-2 shows the no-load electromotive forces (Phase U, Phase V, Phase W) and ideal sinusoidal electromotive forces (Sinus U, Sinus V, Sinus W) of an electrical machine according to the invention (i.e., comprising a design optimized according to the invention). It can be seen that the harmonics of the electromotive forces are greatly reduced, resulting in sinusoidal (or quasi-sinusoidal) phase currents when supplied with a sinusoidal voltage.

[0069]

[0068] The invention thus relates to a rotor 2 comprising a rotor body 3 and, for each pole, a pair of main permanent magnets 5 arranged in a V with the point of the V placed on the side of the center of the rotor 2, these main permanent magnets 5 being placed respectively in main housings 6 in the rotor body 3, each main housing 6 comprising in cross-section (namely the section taken in a plane perpendicular to the axis of the rotor 2) an end recess 7 extending in the longitudinal continuation of the magnet, in the direction of an outer periphery 9 of the rotor 2, the rotor body 3 having a material bridge 10 located radially between the end recess 7 of the main housing 6 and the outer periphery 9 of the rotor, the material bridge 10 having a thickness (the thickness being measured radially, in the plane of the cross-section) which is increasing towards the middle of the V,in particular with a ratio (W2 / W1) between the largest thickness (W2) of the material bridge 10 and the smallest thickness (W1) of the material bridge 10 which is between 3 and 5.

[0070]

[0069] The invention further relates to a rotor 2 comprising a rotor body 3 and, for each pole, a pair of main permanent magnets 5 arranged in a V with the point of the V placed on the side of the center of the rotor 2, these main permanent magnets 5 being placed respectively in main housings 6 in the rotor body 3, each main housing 6 comprising in cross-section (namely the section taken in a plane perpendicular to the axis of the rotor 2) an end recess 7 extending in the longitudinal continuation of the magnet, in the direction of an outer periphery 9 of the rotor 2, and, for each pole of the rotor 2, the rotor body 3 comprises, in addition to the main permanent magnets 5, at least one pair of secondary permanent magnets 12 also arranged in a V, the V shape of the secondary permanent magnets 12 being inside the V shape of the main permanent magnets 5,the secondary permanent magnets 12 being placed in respective secondary housings of the rotor body 3, the secondary housing comprising, in cross-section, an end recess 7 extending in the longitudinal continuation of the magnet, in the direction of an outer periphery 9 of the rotor 2, the end recess of a main housing 6 and the end recess of a secondary housing (which are on the same side of the respective V-shapes) overlapping radially, in particular over an angular sector of overlap between 0.5° and 3°, being for example substantially equal to 2°.

Claims

DEMANDS

1. An electric machine (100) with permanent magnets, in particular of the synchronous type, particularly for a motor vehicle, the electric machine comprising: a stator (1), a rotor (2) comprising a rotor body (3) and, for each pole, a pair of main permanent magnets (5) arranged in a V with the point of the V located on the side of the center of the rotor (2), these main permanent magnets (5) being respectively located in main housings (6) in the rotor body (3), each main housing (6) comprising in cross-section an end recess (7) extending in the longitudinal direction of the magnet, towards an outer periphery (9) of the rotor (2), the rotor body (3) having a material bridge (10) located radially between the end recess (7) of the main housing (6) and the outer periphery (9) of the rotor (2), the material bridge (10) having a thickness (E), the thickness being measured radially,in a plane of the cross-section, thickness which increases towards the middle of the V, in particular with a ratio (W2 / W1) between the greatest thickness (W2) of the material bridge (10) and the smallest thickness (W1) of the material bridge (10) which is between 3 and 5.

2. Machine according to the preceding claim, wherein the smallest thickness (W1) of the material bridge (10) is between 1 and 1.5 mm.

3. Machine according to any one of the preceding claims, wherein the greatest thickness (W2) of the material bridge (10) is between 3 and 7.5 mm.

4. Machine according to any one of the preceding claims, wherein the thickness of the material bridge (10) exhibits a growth, going towards the middle of the V-shape, which is linear.

5. Machine according to any one of claims 1 to 3, wherein the thickness of the material bridge (10) exhibits an evolution, going towards the middle of the V-shape, which is non-linear.

6. Machine according to any one of the preceding claims, wherein, in cross-section, the end recess (7) has a substantially triangular shape.

7. A machine according to any one of the preceding claims, wherein, for each pole of the rotor (2), the rotor body (3) comprises, in addition to the magnets primary permanent magnets (5), at least one pair of secondary permanent magnets (12), preferably also arranged in a V.

8. Machine according to the preceding claim, wherein the V-shape of the secondary permanent magnets (12) is inside the V-shape of the primary permanent magnets (5), and the V-shape of the secondary permanent magnets (12) and the V-shape of the primary permanent magnets (5) have the same axis of mirror symmetry, this axis of symmetry being a radius of the rotor (2).

9. Machine according to claim 7 or 8, wherein the secondary permanent magnets (12) are placed in respective secondary housings (14) of the rotor body (3), and the secondary housing comprises, in cross-section, an end recess (7) extending in the longitudinal continuation of the magnet, in the direction of an outer periphery (9) of the rotor (2), the rotor body (3) having a material bridge (17) located radially between the end recess (7) of the secondary housing and the outer periphery (9) of the rotor (2), the material bridge (17) having a thickness which increases towards the middle of the V, in particular with a ratio between the greatest thickness of the material bridge (17) and the smallest thickness of the material bridge (17) which is between 3 and 5.

10. Machine according to any one of claims 7 to 9, wherein the end recess of a main housing (6) and the end recess of a secondary housing (14) overlap radially, in particular over an angular sector of overlap between 0.5° and 3°, being for example substantially equal to 2°.

11. A rotor (2) comprising a rotor body (3) and, for each pole, a pair of main permanent magnets (5) arranged in a V with the apex of the V located on the center side of the rotor (2), these main permanent magnets (5) being respectively located in main housings (6) in the rotor body (3), each main housing (6) having in cross-section an end recess (7) extending in the longitudinal direction of the magnet, towards an outer periphery (9) of the rotor (2), the rotor body (3) having a material bridge (10) located radially between the end recess (7) of the main housing (6) and the outer periphery (9) of the rotor (2), the material bridge (10) having a thickness that increases towards the middle of the V, in particular with a ratio (W2 / W1) between the greatest thickness (W2) of the material bridge (10) and the smallest thickness (W1) of the material bridge (10) which is between 3 and 5.

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