Rotor for motor, motor for vehicle, and vehicle

Abstract

A rotor (1) for an electric machine (28), comprising a rotor lamination stack (2) divided into a plurality of sectors (3), a permanent magnet assembly (4) being arranged in each of the sectors (3), the permanent magnet assembly (4) comprising two permanent magnets (6, 7) positioned in a V-shaped symmetry relative to a symmetry plane (5), the symmetry plane (5) dividing the sector (3) into two half sectors (8, 9), wherein the outer diameter (r) of the rotor lamination stack (2) in a particular sector (3) has a pair of local minima (16), the local minima (16) being formed symmetrically with respect to the symmetry plane (5) in the half sectors (8, 9) of the sector (3).

Description

Technical Field

[0001] The invention relates to a rotor for an electric machine, comprising a rotor lamination stack divided into a plurality of sectors, each sector being provided with a permanent magnet assembly, the permanent magnet assembly comprising two permanent magnets in V-shaped symmetry with respect to a symmetry plane, the symmetry plane dividing the sector into two half sectors.

[0002] Furthermore, the invention relates to an electric machine for a vehicle and a vehicle. Background Art

[0003] Such a rotor is known, for example, from document DE 10 2012 219 175 A1, which relates to a rotating electrical machine. The rotating electrical machine comprises a rotor with embedded permanent magnets (IPM), in which a plurality of sets of permanent magnets are embedded, each set of magnets comprising a pair of permanent magnets in openings arranged in a V-shape in the direction of the outer circumferential surface.

[0004] Such motors are characterized by a high saliency ratio, which results in a high reluctance torque. However, the V-shaped arrangement of the permanent magnets results in a distorted air gap magnetic field, which deviates from the desired sinusoidal form. Summary of the invention

[0005] The object of the present invention is therefore to describe a possibility for improving the air gap magnetic field distribution of an electric machine, wherein at the same time a high reluctance torque can be generated.

[0006] To achieve this object, according to the invention, in a rotor of the type described at the outset, it is provided that the outer diameter of the rotor lamination stack in a particular sector has a pair of local minima which are formed symmetrically to one another with respect to the symmetry plane in a half-sector of the sector.

[0007] The invention is based on the following consideration: the shape of the rotor lamination stack is adjusted by forming a local minimum of the outer diameter so that the distribution of the air gap magnetic field approximates the desired sinusoidal curve. It has been found that in conventional rotors with a constant outer diameter, a roughly stepped air gap field is generated by the V-shaped arrangement of the permanent magnets, wherein in the region of the magnetic leakage flux, a trapezoidal trend is additionally provided. By selectively changing the outer diameter, this trend of the air gap field can be offset, so that the air gap field of the rotor according to the invention advantageously approximates the desired sinusoidal curve and simultaneously generates a high reluctance torque.

[0008] The permanent magnets usually extend in the axial direction along the rotor. The permanent magnets usually have a rectangular parallelepiped form. The surface normal of the cross-sectional area of ​​the permanent magnet extends in the axial direction, and the cross-section usually has a long side and a short side, wherein the long side is open toward the outer diameter of the rotor lamination stack. Suitably, the rotor lamination stack for each permanent magnet has a magnet pocket, which passes through the rotor lamination stack in the axial direction and in which one of the permanent magnets is arranged. Because of the magnet pocket, gaps may also be formed in the rotor, especially adjacent to the short sides of the permanent magnets. Each sector usually forms a magnetic pole of the rotor. The plane of symmetry usually extends in the radial and axial directions. The symmetry of the half-sector cannot be understood as being limited to the rotor lamination stack itself having to be formed symmetrically within the half-sector. For example, it is conceivable that the opening through the rotor does not have the symmetry of the half-sector in order to fix the shaft in the opening.

[0009] In the rotor according to the invention, it is particularly preferred that the maximum of the outer diameter in a sector lies on the symmetry plane. In this region, the maximum of the approximately sinusoidal air gap field should be present so that the rotor has a maximum of the outer diameter in this region. In the case of the rotor according to the invention, the local maximum of the outer diameter is usually formed at the boundary between two adjacent sectors.

[0010] It has been determined experimentally that the pair of local minima is advantageously located in a partial sector of a half sector which is defined in the circumferential direction by the position of the radially outermost point of the permanent magnet assembly and the position of the circumferentially outermost point of the permanent magnet assembly.

[0011] According to a particularly preferred embodiment of the rotor of the invention, it is provided that the second permanent magnet assembly is arranged in the sector, wherein the radially innermost point of the second permanent magnet assembly is further outward than the radially innermost point of the first permanent magnet assembly, wherein the outer diameter of the rotor lamination stack has a second pair of local minima, which are formed symmetrically to each other with respect to the symmetry plane in the half-sector of the sector and are closer to the symmetry plane in the circumferential direction with respect to the first pair of local minima. Thus, an optimized air gap field can also be achieved by a more complex permanent magnet structure in the sector.

[0012] In this case, it is preferred that the local maximum, in particular a local maximum, lies exactly in the half sector between the first pair of minima and the second pair of minima.

[0013] According to a particularly preferred alternative, it is provided that the second permanent magnet assembly comprises two further permanent magnets arranged in V-shaped symmetry with respect to the symmetry plane of the sector. The permanent magnets of the second permanent magnet assembly generally have a smaller cross-sectional area than the permanent magnets of the first permanent magnet assembly.

[0014] According to another preferred alternative, it is provided that the second permanent magnet assembly comprises permanent magnets arranged orthogonally to the symmetry plane. Thus, the permanent magnets are located in two half sectors.

[0015] In the context of the invention, it has also been recognized that the course of the outer diameter of the rotor can also be described analytically. It is therefore preferred that, in terms of the minimum, in the region close to the plane of symmetry, the course of the outer diameter follows the function:

[0016] r=R max +δ0-δ(x)

[0017] and

[0018]

[0019] Alternatively or additionally, the course of the outer diameter in a region remote from the plane of symmetry relative to the minimum value may follow the following function:

[0020] r=R max +δ0-δ(x)

[0021] and

[0022]

[0023] in this case,

[0024] -r describes the value of the outer diameter,

[0025] -R max Describes the maximum value of the outer diameter,

[0026] -δ0 describes the constant or minimum value of the air gap between the rotor and stator of the motor,

[0027] -α, β describe a positive proportional factor respectively,

[0028] -τ p describes the distance between the symmetry planes of adjacent sectors in the circumferential direction, and

[0029] -x describes the coordinate in the circumferential direction, where x=0 at the position of the symmetry plane and x=0 at the center position between the symmetry planes of adjacent sectors

[0030] In principle, it can be provided in the rotor according to the invention that the pair or a pair of local minima is located at locations where the magnetic flux leakage intensity in the circumferential direction increases.

[0031] The object underlying the invention is also achieved by an electric machine for a vehicle, comprising a stator and a rotor according to the invention, which is rotatably mounted in the stator.

[0032] Finally, the object underlying the invention is also achieved by a vehicle comprising an electric machine according to the invention, which is designed to drive the vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Further advantages and details of the invention will become clear from the exemplary embodiments described below and from the accompanying drawings. These are schematic diagrams and show:

[0034] Figure 1 is a basic cross-sectional view of a first exemplary embodiment of a rotor according to the present invention;

[0035] Figure 2 yes Figure 1 A detailed view of a sector of the rotor is shown;

[0036] Figure 3 yes Figure 1 Basic diagram of a half sector of the rotor shown;

[0037] Figure 4 is a graph of the rotor outer diameter on circumferential coordinates;

[0038] Figure 5 is a graph of the magnetic flux density on the coordinates in the circumferential direction of the rotor;

[0039] Figure 6 The conventional rotor corresponds to Figure 5 Graph of

[0040] Figure 7 is a basic cross-sectional view of another exemplary embodiment of a rotor according to the present invention, and

[0041] Figure 8 is a basic diagram of an exemplary embodiment of a vehicle according to the invention having an exemplary embodiment of an electric machine according to the invention. DETAILED DESCRIPTION

[0042] Figure 1 A basic cross-sectional view of a first exemplary embodiment of a rotor 1 is shown.

[0043] The rotor 1 comprises a rotor lamination stack 2 which is divided into a total of 8 sectors 3. In this case, each point of the rotor 1 in the cross section shown is associated with exactly one sector 3. Thus, two adjacent sectors 3 are directly bounded by each other. A first permanent magnet assembly 4 is arranged in each sector 3, which comprises two permanent magnets 6, 7 positioned in a V-shaped symmetry relative to a symmetry plane 5. The symmetry plane 5 extends in the axial and radial directions of the rotor 1 and divides the rotor 3 into two half-sectors 8, 9. In this case, the permanent magnet 6 is located in the half-sector 8 and the permanent magnet 7 is located in the half-sector 9. Each sector 3 forms a pole of the rotor 1, and the number of sectors 3 or poles is only exemplary.

[0044] Furthermore, the rotor 1 comprises a second permanent magnet assembly 10, which comprises two further permanent magnets 11, 12 in V-shaped symmetry with respect to the symmetry plane 5 of the sector 3, wherein the permanent magnet 11 is arranged in the half-sector 8 and the permanent magnet 12 is arranged in the half-sector 9. The radially innermost point of the second permanent magnet assembly or the permanent magnets 11, 9 is further outward than the radially innermost point of the first permanent magnet assembly 4 or the permanent magnets 6, 7.

[0045] Furthermore, the rotor 1 has a through hole 13 for a shaft (not shown) extending in the axial direction at a central point.

[0046] Figure 2 A detail of a sector 3 of the rotor 1 is shown, which is representative of all other sectors 3. The permanent magnets 6, 7, 11, 12 are shown, which are arranged in magnet pockets 14, respectively, so that the long sides of the permanent magnets 6, 7, 11, 12 contact the rotor lamination stack 2. The magnet pockets extending in the axial direction as through holes are respectively larger than the cross-sectional area of ​​the permanent magnets 6, 7, 11, 12 accommodated, so that gaps 15 are formed in the rotor 1 on the short sides of the magnets.

[0047] Figure 3 The basic diagram is shown for a half sector 8 of a sector 3. The basic diagram is also considered to represent a mirror image of a half sector 9 of a sector 3 and the corresponding half sectors 8, 9 of the other sectors 3.

[0048] The outer diameter r of the rotor lamination stack 2 has a first local minimum 16 in the half-sector 8. Therefore, due to the symmetry of the half-sectors 8, 9, a first pair of local minima is formed in the sector 3. The first local minimum 16 is located in the sub-sector 17 of the half-sector 8 (at Figure 3 In the figure (shown with shading in FIG), the sub-sector is defined in the circumferential direction by the position of the radially outermost point 18 of the first permanent magnet assembly 4 or the permanent magnet 6 or by the position of the outermost point 19 of the permanent magnet in the circumferential direction.

[0049] The outer diameter r in the half-sector 8 also has a second local minimum 20 which is circumferentially closer to the plane of symmetry 5 than the first local minimum 16. The local maximum 21 of the outer diameter r is located between the minima 16 and 20. For the sake of completeness, it should be mentioned that, due to the symmetry of the half-sector, a second pair of local minima and a pair of local maxima are formed.

[0050] In addition, the outer radius r over the entire sector 3 has a global maximum value R max , which is indicated in the figure by a dashed line over the entire circumference of the rotor 1. Further local maxima form the boundaries between two adjacent sectors 3.

[0051] Figure 4is a graph of the outer diameter r of the rotor 1 over the coordinate x in the circumferential direction. In this case, the coordinate describes the distance from the symmetry plane, where x=0 at the position of the symmetry plane and x=τ at the boundary between two adjacent sectors 3 p / 2. In this case, τ p The width of the magnetic poles of the rotor 1 is described.

[0052] In the first region 22 (closer to the symmetry plane relative to the first local minimum 16 and extending from the position of the local maximum 21 to the position of the first local minimum 16) and the second region 23 (closer to the symmetry plane relative to the second local minimum 20 and extending from the position of the symmetry plane 5 to the position of the second local minimum 20), the course of the outer diameter r follows the function:

[0053] r=R max +δ0-δ(x)

[0054] and

[0055]

[0056] Here, α describes the proportionality factor of the first region 22 and the second region 23, and δ0 describes the proportionality factor of the rotor 1 and the stator 29 (see Appendix Figure 8 ) In other words, δ0 describes the minimum air gap relative to the stator inner bore.

[0057] In the third region 24 (away from the symmetry plane relative to the first local minimum 16 and extending from the position of the local minimum 16 to the boundary of the adjacent sector 3) and the fourth region 25 (away from the symmetry plane relative to the second local minimum 20 and extending from the second local minimum 20 to the local maximum 21), the outer diameter r follows the function

[0058] r=R max +δ0-δ(x)

[0059] and

[0060]

[0061] Here, β describes the scaling factor of the third region 24 and the fourth region 25 .

[0062] Figure 5 and Figure 6 The graphs of the magnetic flux density B at the coordinate x are shown respectively. In this case, Figure 5 relates to the air gap magnetic field of an electric machine having an exemplary embodiment of a rotor 1, and Figure 6 It concerns the air gap magnetic field of an electric machine having a rotor corresponding to rotor 1 and whose outer diameter is constant corresponding to the value R max.

[0063] It can be seen that Figure 5 The air gap magnetic field ratio is shown Figure 6 The illustrated curve is closer to a sine curve. This results in the fact that the positions of the minima 16, 20 in the circumferential direction are selected so as to take into account the sharp rise and the step-like course of the magnetic flux at these positions.

[0064] Figure 7 The basic diagram of a second exemplary embodiment of a rotor 1 is shown, which corresponds to the first exemplary embodiment, unless otherwise stated below. In this case, equivalent or functionally equivalent components have the same reference numerals.

[0065] In the rotor 1 according to the second exemplary embodiment, the second permanent magnet arrangement 10 comprises permanent magnets 26 orthogonal to the symmetry plane 5. With this arrangement of permanent magnets 6, 7, 26, it is possible to generate an air gap field which is approximately sinusoidal by forming local minima 16, 21 or local maxima 18, wherein the course of the outer diameter r here will be determined according to Figure 4 The graph in is adjusted, or the function of the outer diameter r is adjusted here according to the deviated leakage magnetic field.

[0066] Figure 8 The basic diagram of an exemplary embodiment of a vehicle 27 is shown, comprising an exemplary embodiment of an electric machine 28. The electric machine 28 has a stator 29 and a rotor 1 according to any of the above-described exemplary embodiments, which is arranged in the stator 29. The electric machine 28 is designed to drive the vehicle 27. Thus, the vehicle can be an electric vehicle (BEV) or a hybrid vehicle.

Claims

1. A rotor for an electric machine, comprising a rotor lamination stack (2) divided into a plurality of sectors (3), a first permanent magnet assembly (4) being arranged in each of the sectors (3), the first permanent magnet assembly (4) comprising two permanent magnets (6, 7) positioned in a V-shaped symmetry relative to a symmetry plane (5), the symmetry plane (5) dividing the sector (3) into two half sectors (8, 9), It is characterized in that The outer diameter (r) of the rotor lamination stack (2) in a specific sector (3) has a pair of first local minima (16), which are formed symmetrically to each other in half sectors (8, 9) of the sector (3) with respect to the symmetry plane (5); The pair of first local minima (16) are located in a sub-sector (17) of the half-sector (8, 9), wherein the sub-sector (17) is defined in the circumferential direction by the position of the radially outermost point (18) of the first permanent magnet assembly (4) and the position of the outermost point (19) of the first permanent magnet assembly (4) in the circumferential direction.

2. The rotor according to claim 1, wherein: The maximum value R of the outer diameter r on the sector (3) max Located on the symmetry plane (5).

3. The rotor according to claim 2, wherein: A second permanent magnet assembly (10) is arranged in the sector (3), wherein the radial innermost point of the second permanent magnet assembly (10) is radially further outward than the radial innermost point of the first permanent magnet assembly (4), wherein the outer diameter r of the rotor lamination stack (2) has a pair of second local minima (20), the second local minima (20) are formed symmetrically with respect to the symmetry plane (5) in the half sectors (8, 9) of the sector (3), and the second local minima (20) is closer to the symmetry plane (5) in the circumferential direction than the first local minimum (16).

4. The rotor according to claim 3, wherein: The local maximum (21) is located in a half sector (8, 9) between a pair of said first local minima (16) and a pair of said second local minima (20).

5. The rotor according to claim 3 or 4, wherein: The second permanent magnet assembly (10) comprises two other permanent magnets (11, 12) which are arranged in a V-shaped symmetry relative to the symmetry plane of the sector.

6. The rotor according to claim 3 or 4, wherein: The second permanent magnet assembly (10) comprises permanent magnets (26) arranged orthogonally to the symmetry plane (5).

7. The rotor according to claim 3 or 4, wherein: In a first region (22) close to the symmetry plane relative to the first local minimum (16) and in a second region (23) close to the symmetry plane relative to the second local minimum (20), the outer diameter follows the function r=R max +δ0-δ(x) and And / or in a third region (24) far from the symmetry plane relative to the first local minimum (16) and a fourth region (25) far from the symmetry plane relative to the second local minimum (20), the outer diameter follows the function r=R max +δ0-δ(x) and in, -r describes the value of the outer diameter, -R max Describes the maximum value of the outer diameter, -δ0 describes the constant, -α, β describe the positive proportionality factors, -τ p describes the distance between the symmetry planes (5) of adjacent sectors (3) in the circumferential direction, and -x describes the coordinate in the circumferential direction, x=0 at the position of the symmetry plane (5), x=0 at the center position between the symmetry planes (5) of adjacent sectors (3) 8. The rotor according to claim 3 or 4, wherein: A pair of local minima are located at positions where the magnetic leakage flux in the circumferential direction has a local maximum.

9. A motor for a vehicle, characterized in that: It comprises a stator (29) and a rotor according to any one of the preceding claims, the rotor being rotatably mounted in the stator (29).

10. A vehicle, characterized in that: The electric machine according to claim 9 is designed to drive a vehicle.

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