ROTOR FOR AN ELECTRIC MACHINE, ELECTRIC MACHINE FOR A VEHICLE AND VEHICLE

Description

[0001] The present invention relates to a rotor for an electrical machine, comprising a rotor core divided into several sectors, in each of which a permanent magnet arrangement is arranged, which comprises two permanent magnets positioned in a V-shape and symmetrically with respect to a plane of symmetry dividing the sector into two half-sectors.

[0002] The invention also relates to an electric machine for a vehicle and a vehicle.

[0003] Such a rotor is known, for example, from document DE 10 2012 219 175 A1, which relates to a rotating electrical machine. This comprises an embedded permanent magnet (IPM) rotor in which several sets of permanent magnets are embedded such that magnets of each set comprise a pair of permanent magnets arranged in a V-shaped arrangement opening toward an outer circular peripheral surface.

[0004] Such a rotor is characterized by a high saliency ratio, which generates a high reluctance torque. However, the V-shaped arrangement of the permanent magnets results in a distorted magnetic air gap field that deviates from the desired sinusoidal shape.

[0005] Further rotors with permanent magnets are known from US 2007 / 145850 A1 and JP 2015053757 A. The invention is therefore based on the object of providing a possibility for improving the distribution of the magnetic air gap field of an electrical machine, while simultaneously generating a high reluctance torque.

[0006] To achieve this object, the invention provides for a rotor of the type mentioned above to have an outer radius of the rotor core in a respective sector that has a pair of local minimum values ​​that are formed symmetrically with respect to the plane of symmetry in a respective half-sector of the sector. The rotor according to the invention is defined by the appended independent claim 1.

[0007] The invention is based on the idea of ​​adapting the outer shape of the rotor core by forming local minimum values ​​of the outer radius so that the distribution of a magnetic air gap field approximates a desired sinusoidal shape. It was recognized that in a conventional rotor with a constant outer radius, the V-shaped arrangement of the permanent magnets generates an essentially stepped air gap field, with a trapezoidal shape additionally occurring in the area of ​​stray flux. By deliberately altering the outer radius, this shape of the air gap field can be counteracted, so that the air gap field in the rotor according to the invention advantageously approximates the desired sinusoidal shape and, at the same time, a high reluctance torque can be generated.

[0008] The permanent magnets typically extend in the axial direction along the rotor. Typically, each permanent magnet has the shape of a cuboid. A cross-sectional area of ​​each permanent magnet, whose surface normal runs in the axial direction, typically has a long side and a short side, with the long sides being open towards the outer radius of the rotor laminated core. The rotor laminated core expediently has a magnetic pocket for each permanent magnet, which extends through the rotor laminated core in the axial direction and within which one of the permanent magnets is arranged. The magnetic pockets can also form free spaces in the rotor, in particular adjacent to the short sides of the permanent magnets. Typically, each sector forms one pole of the rotor. The plane of symmetry typically extends in the radial and axial directions.The symmetry of the half-sectors should not be understood to mean that the rotor core itself must be symmetrical within the half-sectors. For example, it is conceivable that an opening through the rotor may not have symmetry of the half-sectors in order to secure a shaft within the opening.

[0009] It is particularly preferred for the rotor according to the invention if a maximum value of the outer radius is located on the plane of symmetry across a respective sector. A maximum of the approximately sinusoidal air gap field should lie in this region, so that the rotor can have the maximum value of its outer radius here. A local maximum value of the outer radius is typically formed at the boundary between two adjacent sectors in the rotor according to the invention.

[0010] It has been experimentally determined that a respective local minimum value of the pair is advantageously located within a sub-sector of the half-sector which is circumferentially bounded by the position of a radially outermost point of the permanent magnet arrangement and by a position of a circumferentially outermost point of the permanent magnet arrangement.

[0011] According to the invention, a second permanent magnet arrangement is arranged in a respective sector, wherein a radially innermost point of the second permanent magnet arrangement is located radially further outward than a radially innermost point of the first permanent magnet arrangement, wherein the outer radius of the rotor core has a second pair of local minimum values ​​that are formed symmetrically with respect to the plane of symmetry in a respective half-sector of the sector and are located closer to the plane of symmetry in the circumferential direction than the first pair of local minimum values. Thus, the optimized air gap field can be realized even with more complex permanent magnet structures within a sector.

[0012] It is preferred if there is one, in particular exactly one, local maximum value in a respective half-sector between the minimum value of the first pair and the minimum value of the second pair.

[0013] According to a particularly preferred embodiment, the second permanent magnet arrangement comprises two further permanent magnets arranged in a V-shape and symmetrically with respect to the plane of symmetry of the sector. A respective permanent magnet of the second permanent magnet arrangement typically has a smaller cross-sectional area than a respective permanent magnet of the first permanent magnet arrangement.

[0014] According to a further preferred embodiment, the second permanent magnet arrangement comprises a permanent magnet arranged orthogonally to the plane of symmetry. The permanent magnet is therefore located in both half-sectors.

[0015] It was further recognized within the scope of the invention that the course of the outer radius of the rotor can also be described analytically. Thus, it is preferred that the course of the outer radius lies in a region of the function close to the symmetry plane with respect to a minimum value r = R max + δ 0 − δ x with δ x = α cos π τ p x Alternatively or additionally, the course of the outer radius can be determined in a region of the function remote from the symmetry plane with respect to a minimum value r = R max + δ 0 − δ x with δ x = β 1 − 2 τ p x cos π τ p x follow. Describe r is the value of the outer radius, R max is the maximum value of the outer radius, δ 0 is a constant or minimum of the air gap between the rotor and a stator of the electrical machine, α, β each have a positive proportionality factor, τ p a distance in the circumferential direction between the planes of symmetry of adjacent sectors and x a coordinate in the circumferential direction with x = 0 at the position of the symmetry plane and x = τ p 2 at a middle position between the symmetry planes of neighboring sectors.

[0016] In principle, it can be provided in the rotor according to the invention that the or a respective pair of local minimum values ​​are located at a position in the circumferential direction at which a magnetic leakage flux increases significantly.

[0017] The object underlying the invention is further achieved by an electric machine for a vehicle, comprising a stator and a rotor according to the invention rotatably mounted within the stator.

[0018] The object underlying the invention is finally also achieved by a vehicle comprising an electric machine according to the invention which is designed to drive the vehicle.

[0019] Further advantages and details of the present invention will become apparent from the exemplary embodiments described below and from the drawings. These are schematic representations and show: Fig. 1 is a sectional schematic diagram of a first embodiment of the rotor according to the invention; Fig. 2 is a detailed view of a sector of the rotor according to Fig. 1 shown rotor; Fig. 3 a schematic diagram of a half sector of the rotor shown in Fig. 1 shown rotor; Fig. 4 a diagram of an outer radius of the rotor over a coordinate in the circumferential direction; Fig. 5 a diagram of the magnetic flux density over the coordinate in the circumferential direction of the rotor; Fig. 6 a Fig. 5 corresponding diagram of a conventional rotor; Fig. 7 a sectional schematic diagram of another embodiment of the rotor according to the invention; and Fig. 8 a schematic diagram of an embodiment of the vehicle according to the invention with an embodiment of the electric machine according to the invention.

[0020] Fig. 1 is a sectional schematic diagram of a first embodiment of a rotor 1.

[0021] The rotor 1 comprises a rotor core 2 which is divided into a total of eight sectors 3. In the cross-sectional view shown, each point of the rotor 1 is assigned to exactly one sector 3. Two adjacent sectors 3 therefore border one another directly. In each sector 3, a first permanent magnet arrangement 4 with two permanent magnets 6, 7 positioned in a V-shape and symmetrically with respect to a plane of symmetry 5 is arranged. The plane of symmetry 5 extends in the axial and radial direction of the rotor 1 and divides the sector 3 into two half-sectors 8, 9. The permanent magnet 6 is located in the half-sector 8 and the permanent magnet 7 in the half-sector 9. Each sector 3 forms a pole of the rotor 1, whereby the number of sectors 3 or poles is purely exemplary.

[0022] Furthermore, the rotor 1 comprises a second permanent magnet arrangement 10, which comprises two further permanent magnets 11, 12 arranged in a V-shape and symmetrically with respect to the plane of symmetry 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. A radially innermost point of the second permanent magnet arrangement or of a respective permanent magnet 11, 9 is located radially further outward than a radially innermost point of the first permanent magnet arrangement 4 or of the permanent magnets 6, 7.

[0023] In addition, the rotor 1 has a through opening 13 for a shaft (not shown) extending in the axial direction at the center.

[0024] Fig. 2 is a detailed view of a sector 3 of the rotor 1, which is representative of all other sectors 3. As can be seen, respective permanent magnets 6, 7, 11, 12 are each arranged in a magnetic pocket 14, so that respective long sides of the permanent magnets 6, 7, 11, 12 touch the rotor core 2. The magnetic pockets, which extend as through openings in the axial direction, are each larger than a cross-sectional area of ​​the accommodated permanent magnet 6, 7, 11, 12, so that free spaces 15 are formed in the rotor 1 on their respective short sides.

[0025] Fig. 3 is a schematic diagram of half-sector 8 of sector 3. The schematic diagram is also, when viewed in mirror image, representative of half-sector 9 of sector 3 and the corresponding half-sectors 8 and 9 of the remaining sectors 3.

[0026] An outer radius r of the rotor core 2 has a first local minimum value 16 in the half-sector 8. Consequently, due to the symmetry of the half-sectors 8, 9, a first pair of local minimum values ​​is formed in a respective sector 3. The first local minimum value 16 is located within a - in Fig. 3 hatched - partial sector 17 of the half-sector 8, which is limited in the circumferential direction by the position of a radially outermost point 18 of the first permanent magnet arrangement 4 or of the permanent magnet 6 and by a position of a circumferentially outermost point 19 of the permanent magnet.

[0027] The outer radius r further has a second local minimum value 20 in the half-sector 8, which is located closer to the plane of symmetry 5 in the circumferential direction than the first local minimum value 16. Between the minimum values ​​16, 20 there is a local maximum value 21 of the outer radius r. For the sake of completeness, it should be mentioned that due to the symmetry of the half-sectors, a second pair of local minimum values ​​and a pair of local maximum values ​​are formed.

[0028] In addition, the outer radius r has a global maximum value R max over the entire sector 3, which is shown in the figures as a dashed line over the entire circumference of the rotor 1. Another local maximum value is formed by the boundary between two adjacent sectors 3.

[0029] Fig. 4 is a diagram of the outer radius r of rotor 1 over a coordinate x in the circumferential direction. The coordinate x describes the distance from the plane of symmetry, where x = 0 at the position of the plane of symmetry and the value of the coordinate x = τ p / 2 at the boundary between two adjacent sectors 3. τ p describes the pole pitch of rotor 1.

[0030] In a region 22 close to the symmetry plane with respect to the first local minimum value 16, which extends from the position of the local maximum value 21 to the position of the first local minimum value 16, as well as in a region 23 close to the symmetry plane with respect to the second local minimum value 20, which extends from the position of the symmetry plane 5 to the position of the second local minimum value 20, the course of the outer radius r follows the function r = R max + δ 0 − δ x with δ x = α cos π τ p x where α is a proportionality factor for a respective area 22, 23 and δ 0 a minimum value of an air gap between the rotor 1 and a stator 29 (see Fig. 8 ) In other words, δ 0 the minimum air gap to a stator inner bore.

[0031] In a region 24 remote from the symmetry plane with respect to the first local minimum value 16, which extends from the position of the local minimum value 16 to the boundary of the adjacent sector 3, as well as in a region 25 remote from the symmetry plane with respect to the second local minimum value 20, which extends from the position of the second local minimum value 20 to the local maximum value 21, the course of the outer radius r follows the function r = R max + δ 0 − δ x with δ x = β 1 − 2 τ p x cos π τ p x where β describes a proportionality factor for a respective area 24, 25.

[0032] Fig. 5 und Fig. 6 are each a diagram of the magnetic flux density B over the coordinate x. Fig. 5 on the magnetic air gap field of an electrical machine with the embodiment of the rotor 1 and Fig. 6 on the magnetic air gap field of an electrical machine with a rotor corresponding to rotor 1, whose outer radius constantly corresponds to the value R max.

[0033] This is evident in Fig. 5 shown magnetic air gap field is much closer to a sinusoidal shape than the one in Fig. 6 This results from the circumferential positions of the minimum values ​​16 and 20 being chosen to take into account the sharp increase in the magnetic leakage flux at these points as well as the stepped pattern.

[0034] Fig. 7 is a schematic diagram of a second embodiment of a rotor 1, which corresponds to the first embodiment, unless otherwise stated below. Identical or equivalent components are provided with identical reference numerals.

[0035] In the rotor 1 according to the second embodiment, the second permanent magnet arrangement 10 comprises a permanent magnet 26 arranged orthogonally to the symmetry plane 5. Even with such a structure of permanent magnets 6, 7, 26, an air gap field approximating the sinusoidal curve can be generated by the formation of local minimum values ​​16, 21 or local maximum values ​​18, wherein the curve of the outer radius r here differs from the representation in Fig. 4 or the functions for the outer radius r have to be adapted to the different stray field.

[0036] Fig. 8is a schematic diagram of an embodiment of a vehicle 27, comprising an embodiment of an electric machine 28. The electric machine 28 has a stator 29 and a rotor 1 arranged within the stator 29 according to one of the previously described embodiments. The electric machine 28 is configured to drive the vehicle 27. The vehicle can accordingly be an electric vehicle (BEV) or a hybrid vehicle.

Claims

1. Rotor (1) for an electric machine (28), comprising a rotor lamination stack (2) subdivided into a plurality of sectors (3), in each of which a first permanent magnet arrangement (4) is arranged, which comprises two permanent magnets (6, 7) positioned in a V-shape and symmetrically with respect to a symmetry plane (5) that divides the sector (3) into two half-sectors (8, 9), wherein an outer radius (r) of the rotor lamination stack (2) in a respective sector (3) comprises a first pair of local minima (16), which are formed symmetrically with respect to the symmetry plane (5) in a respective half-sector (8, 9) of the sector (3), and are each located within a sub-sector (17) of the half-sector (8, 9), and a second pair of local minima (20), which are formed symmetrically with respect to the symmetry plane (5) in a respective half-sector (8, 9) of the sector (3), and are located in the circumferential direction closer to the symmetry plane (5) than the first pair of local minima (16), wherein a local maximum of the outer radius (r) is formed at the boundary between two adjacent sectors (3), characterized in that the sub-sector (17) is delimited in the circumferential direction by the position of a radially outermost point (18) of the first permanent magnet arrangement (4) and by a position of a radially outermost point (19) of the first permanent magnet arrangement (4) located furthest from the symmetry plane in the circumferential direction, wherein in a respective sector (3) a second permanent magnet arrangement (10) is arranged, wherein a radially innermost point of the second permanent magnet arrangement (10) lies radially further outward than a radially innermost point of the first permanent magnet arrangement (4).

2. Rotor according to claim 1, wherein a maximum value (Rmax) of the outer radius (r) in a respective sector (3) is located on the symmetry plane (5).

3. Rotor according to claim 1 or 2, wherein a respective minimum value (16) of the first pair is smaller than a respective minimum value (20) of the second pair.

4. Rotor according to any one of the preceding claims, wherein in a respective half-sector (8, 9) between the minimum value (16) of the first pair and the minimum value (20) of the second pair, a further local maximum value (21) is located.

5. Rotor according to any one of the preceding claims, wherein the second permanent magnet arrangement (10) comprises two further permanent magnets (11, 12) arranged in a V-shape and symmetrically with respect to the symmetry plane of the sector.

6. Rotor according to any one of claims 1 to 4, wherein the second permanent magnet arrangement (10) comprises a permanent magnet (26) arranged orthogonally to the symmetry plane (5).

7. Rotor according to any one of the preceding claims, wherein the profile of the outer radius - in a region (22, 23) near the symmetry plane with respect to a minimum value (16, 20) follows the function r = R max + δ 0 − δ x with δ x = α cos π τ p x and / or - in a region (24, 25) distant from the symmetry plane with respect to a minimum value (16, 20) follows the function r = R max + δ 0 − δ x with δ x = β 1 − 2 τ p x cos π τ p x wherein - r is the value of the outer radius, - Rmax is the maximum value of the outer radius, - δ0 is a constant, - α, β are respective positive proportionality factors, - τp is a distance in the circumferential direction between the symmetry planes (5) of adjacent sectors (3), and - x is a coordinate in the circumferential direction with x = 0 at the position of the symmetry plane (5) and x = τp / 2 at a mid-position between the symmetry planes (5) of adjacent sectors (3).

8. Rotor according to any one of the preceding claims, wherein a respective pair of local minima (16, 20) is located at a position in the circumferential direction where a magnetic stray flux exhibits a local maximum.

9. Electric machine (28) for a vehicle (27), comprising a stator (29) and a rotor (1) according to any one of the preceding claims, wherein the rotor (1) ist rotatably supported within the stator (29).

10. Vehicle (27), comprising an electric machine (28) according to claim 9, which is configured to drive the vehicle (27).