WO2020057847A1

WO2020057847A1 - Rotor with embedded magnets

Info

Publication number: WO2020057847A1
Application number: PCT/EP2019/070938
Authority: WO
Inventors: Andre Brune; Peter Theisinger; Alexander Rosen
Original assignee: Robert Bosch Gmbh
Priority date: 2018-09-18
Filing date: 2019-08-02
Publication date: 2020-03-26
Also published as: DE102018215864A1

Abstract

The present invention relates to a rotor (1) of an electric motor (2), comprising a rotor laminated core (3) and a multiplicity of permanent magnets (4, 5) which are arranged in recesses (6) of the rotor laminated core (3), wherein a rotor pole of the rotor (1) has, as seen in a cross-sectional plane of the rotor laminated core (3), two first permanent magnets (4) which are arranged adjacently in a V shape and a multiplicity of second permanent magnets (5) which are provided in a C-shaped arrangement and at least partially engage around, in particular, the first permanent magnets (4), characterized in that an angle (aa) between the first permanent magnets (4) is between 115° and 153°.

Description

description

title

ROTOR WITH EMBEDDED MAGNETS

State of the art

The present invention relates to a rotor of an electric motor. Furthermore, the invention relates to an electric motor comprising such a rotor. In particular, the rotor has a multiplicity of permanent magnets which are attached in a VC arrangement.

Electric motors are known from the prior art. These include a rotor that has a plurality of permanent magnets. For this purpose it is provided that the rotor has stacked sheets, said sheets

Have recesses into which permanent magnets can be inserted. For the arrangement of the permanent magnets within the laminated core are

different versions possible. A single V arrangement is known from WO 2012/059 258 A1. There are two for each pole

Permanent magnets arranged in the form of a "V". Document DE 10 2012 022 152 A1 also discloses such a V arrangement. A VC arrangement is also known, for example from DE 10 2009 046 165 A1, in which the V-shaped magnets are enclosed by an additional row of magnets, this additional row of magnets having a C-shape. In order to form a VC arrangement, a V arrangement is usually used, for which two permanent magnets are necessary. With at least four permanent magnets, the V-arrangement is enclosed by a C-arrangement, the C-arrangement comprising a combination of two V-angles between radially inner permanent magnets and radially outer permanent magnets due to its construction of four permanent magnets. From US 8 994 240 B1 a VC arrangement is known which is designed for maximum rotor flux. Finally, a multi-C arrangement is known from FR 2973179 B1, which has a large number of small permanent magnets. Disclosure of the invention

The rotor of an electric motor according to the invention allows a small one

Torque ripple and the lowest possible noise level. At the same time, it is increased compared to the prior art

Demagnetization resistance and thus rotor limit temperature can be achieved without negatively influencing rotor flux, torque ripple and noise level. The height of the permanent magnets is determined by a compromise between cost and demagnetization resistance and thus has a direct influence on the rotor temperature limit.

The rotor of an electric motor comprises a laminated rotor core and a large number of permanent magnets. The permanent magnets are arranged in recesses in the rotor laminated core. It is envisaged that the

Permanent magnets at least two first arranged in a V-shape

Has permanent magnets and a plurality of C-shaped second permanent magnets. The plurality of second permanent magnets preferably encompass at least partially the first permanent magnets. In particular, a rotor pole is formed by the V-shaped first permanent magnets and the C-shaped second permanent magnets. It is further provided that an angle between the first permanent magnets is between 115 ° and 153 °. Such a V-angle of the first permanent magnets results in a flat V-arrangement compared to the prior art. Thus, in particular, the plurality of C-shaped second permanent magnets can be arranged closer to the air gap between the rotor and stator of the electric motor, which means that the second permanent magnets are mounted closer to a radial outer surface of the rotor.

Such a design is easier to magnetize and allows more freedom for optimization for reduced torque ripple and

Torque locking behavior and for improved acoustic behavior. Furthermore, there is more free space for cooling holes in the rotor laminated core. Less magnetic mass is also necessary, since in particular there is no requirement for permanent magnets of the same size as in the prior art is present, whereby the rotor can be made cheaper in terms of material costs. Finally, by the more finely adjustable

Magnetic mass can reduce a field weakening current in the D-axis, whereby the continuous performance of the electric motor equipped with the rotor is improved. This behavior is particularly proportional to the short-circuit current of the machine. This means that if the magnetic mass increases, the short-circuit current increases, which reduces the continuous power and vice versa.

The dependent claims contain preferred developments of the invention.

The rotor has in particular a large number of rotor poles. All rotor poles in turn have only the two V-shaped first permanent magnets and the C-shaped second permanent magnets. Particularly advantageously, the rotor pole has no further permanent magnets, but only the first permanent magnets and second permanent magnets described.

The V-shaped first permanent magnets (4) and the C-shaped second permanent magnets are each arranged symmetrically to a pole center of the rotor pole. The center of the pole is in particular a central axis which extends radially from a center of the rotor. Thus, the first are permanent magnets and the second

Permanent magnets arranged axially symmetrical. A radially innermost point of the first permanent magnet and a radially innermost point of the second

Permanent magnets are therefore at a minimal distance from said pole center or the central axis indicating the pole center.

It is preferably provided that the plurality of second permanent magnets comprise two inner permanent magnets and two outer permanent magnets with respect to a circumferential direction of the rotor. Thus, in particular, two inner second permanent magnets and two outer second permanent magnets are present in addition to the first permanent magnets. The inner second permanent magnets have an angle to each other between 101 ° and 104 °. Alternatively or additionally, the outer second permanent magnets have an angle to one another of between 64 ° and 105 °. By such Arrangement is achieved that all second permanent magnets are attached close to the outer circumferential surface of the rotor, whereby the second permanent magnets can be arranged close to an air gap of the electric motor between the rotor and the stator. This has advantages in terms of the performance of the electric motor as well as in terms of noise emission and

Torque ripple.

A first pole cover angle of the first permanent magnets preferably comprises between 59.5 ° and 72 °. Alternatively or additionally, a second pole cover angle of the second permanent magnets comprises between 11 1, 5 ° and 122.5 °. The pole cover angle is, in particular, such an angle that the first permanent magnets and / or the second permanent magnets as a whole sweep over. This is the case for each pole

Electric motor a V arrangement of first permanent magnets and a C arrangement of second permanent magnets available. A first pole covering angle of the first permanent magnets and a second pole covering angle of the second permanent magnets can thus be set for each pole. In contrast to the prior art, the first pole cover angle and the second pole cover angle are each not exclusively at maximum

Designed rotor flux, rather a low torque ripple and a low noise level is achieved.

A first magnet height of the first permanent magnets is advantageously different from a second magnet height of the second permanent magnets. The first magnet height is particularly preferably smaller than the second

Magnet height. Under magnet height is a particular strength

Understanding permanent magnets means a dimension of the

Permanent magnets perpendicular to the V direction and / or perpendicular to the C direction. The use of different magnet heights of first permanent magnets and second permanent magnets in particular prevents all permanent magnets from having the same dimensions. As a result, the arrangement of first permanent magnets and second permanent magnets can be designed flexibly, which means that

in particular, the advantages described above with regard to high performance and low noise emissions and low torque ripple can be set. Furthermore, it is provided that a central web width of the first

Permanent magnet is different from a second central web width of the second permanent magnet. The central web width is in particular a width of a web between the recesses in the rotor laminated core, in each of which half of the first permanent magnets and / or second permanent magnets are arranged. Thus, the V arrangement of first permanent magnets and the C arrangement of second permanent magnets achieve a symmetrical arrangement with respect to a central axis, this symmetrical arrangement comprising a total of four recesses in the rotor laminated core. So there are two recesses for the first

Permanent magnets are present, while there are also two recesses for the second permanent magnets. These recesses do not meet on the central axis, but have a central web here. As already described, the central web widths of the recesses for the first permanent magnets and the central web width for the recesses of the second permanent magnets are not identical. Rather, it is preferably provided that the second central web width of the second permanent magnets is larger than the first central web width of the first permanent magnets. The first central web width is particularly advantageously between 0.5 mm and 1.2 mm. Alternatively or additionally, the second central web width is between 2.0 and 3.2 mm.

A first web height between those recesses in which the first permanent magnets are arranged and a sheet metal packet outer surface and a second web height between those recesses in which the second permanent magnets are arranged and a metal sheet packet outer surface are in particular constant. Should the web height change along the circumference of the rotor laminated core, it is advantageously provided that the web height increases in the direction of the center of the pole. The web height thus separates the recesses for the first permanent magnets and / or the second

Permanent magnets from the rotor outer surface and thus from the air gap. In particular, it is provided that the first web height is smaller than the second web height. It is particularly advantageously provided that the first web height is at least between 0.7 mm and 1.5 mm. The second web height is advantageously at least between 0.8 mm and 2.2 mm. Such web heights allow the permanent magnets to be close to the outer surface of the rotor and thus close to the air gap. This is advantageous in terms of high performance and optimal torque ripple and less

Noise emissions.

The invention also relates to an electric motor. The electric motor includes a rotor as previously described. In addition, the electric motor comprises a stator for driving the electric motor. Due to the design of the rotor, the electric motor has a high torque and a high output. At the same time, a good acoustic property is realized by the

Electric motor has a low noise emission. Finally, it is also achieved that the electric motor has a low torque ripple.

Finally, it is preferably provided that a web angle in the q-axis is between 7.5 ° and 16 °. In particular, it can thus be achieved or at least supported that an increased rotor flux does not lead to an increase in losses.

The electric motor particularly advantageously has an air gap between 1.0 mm and 1.7 mm. Such an air gap in particular ensures that an increased rotor flux does not lead to an increase in losses in the

Electric motor leads. The air gap tends to be large.

Losses can thus be minimized or avoided, particularly in the field weakening area.

The first magnet height is particularly advantageously the first

Permanent magnets between 2.6 mm and 4.8 mm. The second magnet height of the second permanent magnets is advantageously between 4.0 mm and 6.5 mm. Thus, a compact structure for a VC arrangement is the

Permanent magnets reached.

Brief description of the drawing

Exemplary embodiments of the invention are described in detail below with reference to the accompanying drawing. In the drawing is: Figure 1 is a schematic illustration of a section of a

Electric motor according to an embodiment of the invention.

Embodiment of the invention

FIG. 1 schematically shows a section of an electric motor 2 comprising a rotor 1 and a stator 8. Only a section of the electric motor 2 is shown, which comprises a pole of the electric motor 2.

The rotor 1 is designed around an axis of rotation 100 and comprises a

Rotor laminated core 3, which comprises a plurality of stacked laminations. The rotor core 3 comprises a plurality of recesses 6, first permanent magnets 4 and second permanent magnets 5 being arranged in the recesses 6. The first permanent magnets 4 form a V-shape, while the second permanent magnets 5 form a C-shape. Thus, the permanent magnets 4, 5 of the electric motor 2 are attached in a VC arrangement. The C arrangement of second permanent magnets 5 at least partially encompasses the V arrangement of first permanent magnets. The V arrangement of first permanent magnets 4 comprises two first permanent magnets 4, which are arranged symmetrically about a central axis of the pole. The C arrangement of the second permanent magnets 5 is also symmetrical about a central axis of the pole and comprises a total of four second permanent magnets. This results in two V-angles for the second permanent magnets, since two radially inner permanent magnets 5a and two radially outer ones

Permanent magnets 5b are present. The inner second permanent magnets 5a have a first V angle, while the outer second

Permanent magnets 5b have a second V angle.

It is provided that an angle a _a between the first permanent magnets 4 is between 115 ° and 153 °. An angle <2 between the inner second permanent magnets 5a is between 101 ° and 140 °. An angle ai between the outer second permanent magnets 5b is between 64 ° and 105 °. Such an arrangement realizes a flat VC arrangement, in which all permanent magnets 4, 5 are attached as close as possible to the outer surface 7 of the laminated core. It is thus achieved in particular that a design that can be magnetized very easily is present. In particular, everyone is Magnet, which is arranged radially as far as possible on the outside of the rotor laminated core 3, is easier to magnetize than if it were located radially inside in the

Rotor laminated core 3 is attached. Furthermore, such a design creates more scope for optimization for reduced torque ripples and cogging torques, as well as improved acoustic behavior due to low noise emissions. There is also more free space for cooling holes within the rotor laminated core 3. Finally, it is also advantageous that the total magnetic mass of the permanent magnets 4, 5 can be lower than in the prior art. This is particularly advantageous in terms of material costs. In addition, field weakening currents in the D axis can be reduced, as a result of which the continuous power of the electric motor 2 increases.

Furthermore, a first pole coverage angle is β, the first

Permanent magnets 4 formed between 1 11, 5 ° and 122.5 °. A second pole coverage angle β _{a of} the second permanent magnets 5 is preferably between 59.5 ° and 72 °. This means that in addition to a high rotor flux, there is also a low torque ripple and the lowest possible

Noise levels are present. In contrast to the prior art, the rotor 1 is therefore not designed solely for maximum rotor flux. Rather, the torque ripple and the noise level have also been discussed in order to optimize these parameters as well.

In order not to obtain increased losses due to an increased rotor flux, the air gap ^ is also preferably made relatively large.

In particular, the air gap J is between 1.0 mm and 1.7 mm. At the same time, the web angle is optimized in the q-axis, which means that in particular the

Web angle in the q-axis f _{h is} between 7.5 ° and 16 °.

In order to achieve a compact design as described above, it is particularly provided that a first magnet height h _{ma of} the first permanent magnets 4 and a second magnet height h _{mi of} the second permanent magnets 5

is different. In particular, the first magnet height h _{ma is} between 2.6 mm and 4.8 mm. The second magnet height h _mi is preferably between 4.0 mm and 6.5 mm. Likewise, a first central web b _sa is preferably smaller than a second central web b _Si , the first central web b _{sa being} the central web of the recesses 6 of the first permanent magnets, while the second central web b _{Si is} Middle web between the recesses 6 of the second permanent magnet 5. The first central _web width b _sa is in particular between 0.5 mm and 1.2 mm. The second central _web width b _Si is preferably between 2.0 mm and 3.2 mm.

Furthermore, there is a minimal web height between the outer surface 7 of the laminated core and the recesses 6. A first web height h _sa between the recesses 6 of the first permanent magnets 4 and a second web height h _Si between the recesses 6 of the second permanent magnets 5a and the outer surface 7 of the laminated core are in particular different. Furthermore, the first web height h _sa and the second web height h _Si advantageously increase in the direction of the pole center or are constant. The first is preferably

Web height h _sa at least between 0.7 mm and 1.5 mm. The second web height h _Si is advantageously at least between 0.8 mm and 2.2 mm.

With such an arrangement of the first permanent magnets 4 and the second permanent magnets 5 it can be achieved that the electric motor 2 is optimally designed as a permanently excited synchronous machine. In particular, there is a high torque and a high output of the electric motor 2. There is also a high speed stability and optimal acoustic

Characteristics in that a low noise level is realized. There is also a slight torque ripple. In addition, losses, in particular iron losses and magnetic losses, are minimized. At the same time, the electric motor 2 is simple and inexpensive to manufacture, so that the material costs and manufacturing costs are minimized. Finally, a high result

Resistance to demagnetization and high rotor temperature limits.

Claims

Expectations

1. rotor (1) of an electric motor (2) comprising a rotor laminated core (3) and a plurality of permanent magnets (4, 5) which are arranged in recesses (6) in the laminated rotor core (3), a rotor pole of the rotor (1) Seen in a cross-sectional plane of the rotor laminated core (3), two first permanent magnets (4) arranged adjacent to one another in a V-shape and a plurality of second permanent magnets (5) which are provided in a C-shaped arrangement and in particular at least partially encompass the first permanent magnets (4) , characterized in that an angle (a _a ) between the first permanent magnets (4) is between 115 ° and 153 °.

2. Rotor (1) according to claim 1, characterized by a plurality of

Rotor poles, all of the rotor poles having only the two V-shaped first permanent magnets (4) and the C-shaped second permanent magnets (5).

3. Rotor (1) according to claim 1 or 2, characterized in that the

Rotor pole has a pole center, in particular a central axis, the V-shaped first permanent magnets (4) and the C-shaped second permanent magnets (5) each being arranged symmetrically to the pole center, in particular the central axis.

4. Rotor (1) according to one of the preceding claims, characterized

characterized in that the plurality of second permanent magnets (5) with respect to a circumferential direction of the rotor (1) two inner second

Permanent magnets (5a) and two outer second permanent magnets (5b), the inner second permanent magnets (5a) making an angle (02) to each other between 101 ° and 140 ° and / or the outer second permanent magnets (5b) making an angle (ai) to each other between 64 ° and 105 °.

5. Rotor (1) according to one of the preceding claims, characterized

characterized in that a first pole cover angle (β _a ) of the first permanent magnets (4) between 59.5 ° and 72 ° and / or a second pole cover angle (β,) of the second permanent magnets (5) between 11 1, 5 ° and 122.5 ° is.

6. Rotor (1) according to one of the preceding claims, characterized

characterized that a first magnet height (h _ma ) of the first

Permanent magnets (4) differ from a second magnet height

in particular smaller than the second magnet height

The second

Permanent magnet (5) is.

7. Rotor (1) according to one of the preceding claims, characterized

characterized in that a first central web _width (b _sa ) of the first

Permanent magnets (4) differ from a second central web _width (b _si ) of the second permanent magnets (5).

8. rotor (1) according to any one of the preceding claims, characterized

characterized in that a first web height (h _sa ) between those recesses (6) in which the first permanent magnets (4) are arranged and an outer surface of the laminated core (7) and a second web height (h _Si ) between those recesses (6), in which the second

Permanent magnets (5) are arranged, and an outer surface of the laminated core (7) is constant or increases in the direction of a pole center.

9. Electric motor (2) comprising a rotor (1) according to one of the preceding claims, wherein the rotor (1) from a stator (8) of the electric motor (2) can be driven.

10. Electric motor (2) according to claim 9, characterized in that a

Web angle (<p _q ) in the q axis is between 7.5 ° and 16 °.