CN112751432A

CN112751432A - Rotor and motor

Info

Publication number: CN112751432A
Application number: CN201911052194.9A
Authority: CN
Inventors: 黄启林
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2019-10-31
Filing date: 2019-10-31
Publication date: 2021-05-04
Also published as: WO2021083631A1

Abstract

The application provides a rotor of a motor, including: a rotor body arranged to be fixedly connectable with a shaft of the electrical machine and having a longitudinal axis, wherein the rotor body has a varying cross-section at different positions along the longitudinal axis. In addition, the application also provides a motor comprising the rotor. The rotor and the motor can reduce the temperature imbalance phenomenon of the rotor, and avoid local overheating of the motor, so that the load capacity of the motor is improved.

Description

Rotor and motor

Technical Field

The present application relates to the field of motor technology, and more particularly, to a rotor having an improved structure and a motor including the rotor.

Background

Electric machines are widely used as a device for converting electric energy into mechanical energy, for example, in electric vehicles. The existing motor generally includes a rotor and a stator, and is divided into various types according to the interaction manner of a magnetic field and an electric field between the rotor and the stator, and the like. Both the rotor and the stator of an electric machine generate a lot of heat during operation, since the magnetic field generates "hysteresis losses" and "eddy current losses" in the conductors (e.g. windings or cores) of the rotor and the stator.

The motor can radiate heat through natural cooling, forced air cooling or liquid cooling, but in practical application environment, the motor is often covered or blocked by other parts to influence air circulation or the temperature difference of the cooling medium at the local part of the motor to influence the heat radiation effect to cause local overheating. For example, naturally cooled motors for electric vehicles typically dissipate heat through natural convection of the housing and two end cover surfaces, but may be shielded by other components (e.g., vehicle beams, controls, cables, etc.) at certain axial locations of the motor due to limitations in the vehicle chassis mounting space. In such a layout, if the airflow at the surface of the casing cannot smoothly circulate, the temperature distribution of the rotor and the stator in the longitudinal axis direction in the motor may be unbalanced. For example, for a motor with forced air cooling or liquid cooling, the cooling effect at the position close to the air inlet (liquid) is better because the medium temperature of the air inlet (liquid) is lower, and the cooling effect at the position close to the air outlet (liquid) is poorer because the medium temperature of the air outlet (liquid) is higher. In addition, because of the interference fit between the stator and the housing, the heat of the stator can be dissipated out through the motor housing in time, and the heat of the rotor can be diffused out slowly, which results in heat accumulation. This imbalance becomes more severe if the axial length of the rotor of the machine is longer. This localized overheating limits the maximum electrical load that the motor can withstand, making the load much less than the designed peak torque, and possibly even causing the motor to burn out.

Therefore, there is a need for an improved motor to reduce the temperature imbalance of the rotor and avoid local overheating of the motor, thereby further improving the load capacity of the motor.

Disclosure of Invention

The object of the present application is to propose a rotor with an improved structure and an electric machine comprising such a rotor, in order to overcome the above-mentioned technical problems.

To this end, according to an aspect of the present application, there is provided a rotor of an electric machine, including: a rotor body arranged to be fixedly connectable with a shaft of the electrical machine and having a longitudinal axis, wherein the rotor body has a varying cross-section at different positions along the longitudinal axis.

Optionally, the rotor further comprises a plurality of permanent magnets embedded within the rotor body.

Optionally, the plurality of permanent magnets are arranged with their geometric centers at the same radial distance from the longitudinal axis of the rotor body.

Alternatively, the rotor body is made of different sized ferrous alloy sheets that overlap each other.

According to another aspect of the present application, there is provided a motor including: a stator provided with a cavity; a rotor as described above, housed within a chamber of the stator; and the shaft is fixedly connected with the rotor body.

Optionally, the chamber of the stator has a varying cross-section at different locations along the longitudinal axis of the rotor.

Optionally, the motor further comprises a housing, the large diameter portion of the rotor body is disposed at a position corresponding to a portion of the housing where a heat radiation condition is favorable, and the small diameter portion of the rotor body is disposed at a position corresponding to a portion of the housing where a heat radiation condition is unfavorable.

Optionally, the motor further includes a cooling fan, the large diameter portion of the rotor body is disposed close to the cooling fan, and the small diameter portion of the rotor body is disposed far from the cooling fan.

Optionally, the motor further comprises a liquid cooling loop, the large diameter portion of the rotor body is disposed proximate to an inlet of the liquid cooling loop, and the small diameter portion of the rotor body is disposed proximate to an outlet of the liquid cooling loop.

The rotor and the motor comprising the rotor can improve the heat distribution of the rotor by enabling the rotor to have a variable cross section in the direction of the longitudinal axis, so that the unbalance phenomenon of the temperature of the rotor is reduced, and the safe and efficient operation of the motor is ensured.

Drawings

Exemplary embodiments of the present application will be described in detail below with reference to the attached drawings, it being understood that the following described embodiments are merely illustrative of the present application and do not limit the scope of the present application, and in which:

fig. 1 is a cross-sectional view schematically illustrating a motor according to an embodiment of the present application;

fig. 2A is a perspective view schematically showing a rotor of the motor in fig. 1;

fig. 2B is a perspective view schematically showing a stator of the motor in fig. 1;

fig. 3A and 3B are cross-sectional views schematically showing the motor in fig. 1 taken at a large-diameter portion and a small-diameter portion of a rotor, respectively.

Detailed Description

Preferred embodiments of the present application are described in detail below with reference to examples. In the embodiments of the present application, the present application is described taking a rotor including permanent magnets and a permanent magnet motor as examples. However, it should be understood by those skilled in the art that these exemplary embodiments are not meant to limit the present application in any way. Furthermore, the features in the embodiments of the present application may be combined with each other without conflict. In the different figures, identical or similar components are indicated with identical reference numerals and other components are omitted for the sake of brevity, but this does not indicate that the rotor and the motor of the present application may not comprise other components. It should be understood that the sizes, proportions and numbers of elements in the drawings are not intended to limit the present application.

As shown in fig. 1, a motor 100 according to an embodiment of the present application generally includes a rotor 20, a stator 30, and a shaft 40. The rotor 20 includes a rotor body 21, and the rotor body 21 is provided to be capable of being fixedly connected with the shaft 40. For example, the shaft 40 may pass through the central bore 23 of the rotor body 21 and be keyed or otherwise fixedly coupled to the rotor body 21. The rotor body 21 has a longitudinal axis X and accordingly a longitudinal length extending along the longitudinal axis X. The stator 30 is provided with a cavity 31, and the rotor 20 may be accommodated in the cavity 31 of the stator 30. In addition, the motor 100 may further include a housing 10, a first end cap 11, and a second end cap 12, and the housing 10 and the first and

second end caps

11 and 12 together define a space for accommodating the rotor 20 and the stator 30. One end of the shaft 40 may extend through the first end cap 11 to connect to a transmission (not shown). Of course, the motor 100 may also include other components, such as bearings, bolts, wires, etc., which are not described in detail herein.

As shown in fig. 1 and 2A, in the electric machine 100 of the present application, the cross-section of the rotor 20 at different positions along the longitudinal axis X is not constant as in the prior art, but varies. In particular, the rotor body 21 may have a varying cross-section at different positions along its longitudinal axis X. That is, the rotor body 21 may have different cross-sections in different planes perpendicular to the longitudinal axis X. In the case of a rotationally symmetrical rotor body 21 with respect to the longitudinal axis X, the rotor body 21 may have different outer diameters in a direction along the longitudinal axis X. In this way, by providing the rotor body 20 with a varying cross-section at different positions on the longitudinal axis X, the heat distribution of the rotor 20 may be improved. Accordingly, the cross-section of the stator 30 at different locations on the longitudinal axis X may also be varied to conform to the varying cross-section of the rotor 20 and maintain a small gap, as shown in fig. 1 and 2B. In addition, the stator 30 may also include wire slots 32 to accommodate field windings.

The improvement resulting from the variation in the cross-section of the rotor 20 is further described below by way of example of a permanent magnet machine.

For a permanent magnet machine, as shown in fig. 2A, the rotor 20 may further include a plurality of permanent magnets 22, and the plurality of permanent magnets 22 may be embedded within the rotor body 21. Typically, the permanent magnets 22 are arranged with their geometric centers at the same radial distance from the longitudinal axis X of the rotor body 21, i.e. evenly distributed in the rotor body 21 in a ring around the longitudinal axis X. It should be noted that, in addition to the "V" shaped arrangement of the permanent magnets 22 shown in fig. 2A, other arrangements may be employed depending on the magnet shape, the number of pole pairs, the magnetic field direction, and the like. The permanent magnets 22 may be ferrite magnets, rare earth magnets, etc., which are widely used in the art, and the rotor body 21 may be made of iron alloy sheets having different sizes, i.e., iron cores, which are overlapped with each other.

During operation, the magnetic flux of the permanent magnets 22 flows in the rotor body 21 generating heat, so-called "hysteresis losses". In addition, since the rotor body 21 itself is also a conductor, an induced electromotive force is generated in a plane perpendicular to the magnetic force lines, and a closed circuit is formed in the cross section of the rotor body 21 to generate a current, which causes the rotor body 21 to generate heat, that is, so-called "eddy current loss". In the case where the permanent magnets 22 embedded in the rotor body 21 are positionally invariant with respect to the longitudinal axis X, the permanent magnets 22 are at different distances from the outer surface of the rotor body 21, since the cross section of the rotor body 21 of the rotor 20 at different positions along the longitudinal axis X varies. As shown in fig. 3A, at the large diameter portion of the rotor body 21, the distance of the permanent magnet 22 from the outer surface of the rotor body 21 is large, and accordingly the material thickness of the rotor body 21 at that position is large. In this case, the path of the magnetic flux flowing in the rotor body 21 is long, resulting in a large "hysteresis loss", while the induced electromotive force forms a large closed loop in the rotor body material of a large cross section, resulting in a large "eddy current loss". Thus, having the rotor body 21 of the rotor 20 generate more heat at the large diameter portion centering on the permanent magnets 22 results in a higher temperature there, and the speed of heat diffusion out is correspondingly slower due to the larger distance of the permanent magnets 22 from the outer surface of the rotor body 21. Combining the factors that affect the heat generation and the heat diffusion, it is known that the temperature of the rotor 20 is high at the large-diameter portion. On the contrary, as shown in fig. 3B, at the small diameter portion of the rotor 20, the distance of the permanent magnet 22 from the outer surface of the rotor body 21 is small, and accordingly the heat and temperature conditions are opposite to the above.

Therefore, in the design of the rotor 20, the large diameter portion of the rotor body 21 may be disposed at a position corresponding to a portion where the heat radiation condition of the casing 10 is favorable, and the small diameter portion of the rotor body 21 may be disposed at a position corresponding to a portion where the heat radiation condition of the casing 10 is unfavorable. It should be noted that fig. 1 to 2B are merely examples of a natural air-cooled motor, and the shapes of the rotor 20 and the stator 30 that vary in the longitudinal axis direction are shown only schematically, and may vary in an actual motor according to heat dissipation conditions, structural requirements, and the like of the motor at different positions. Accordingly, the rotor 20 of the present application is not limited to the shape and structure shown in fig. 1 to 2B.

Still further, the motor 100 may also be a forced air-cooling motor, and accordingly includes a cooling fan (not shown), for example, installed at one end of the motor 100, and the large-diameter portion of the rotor body 21 may be disposed close to the cooling fan and the small-diameter portion of the rotor body 21 may be disposed far from the cooling fan. Alternatively, the motor 100 may also be a forced liquid-cooled motor, correspondingly including a liquid-cooled circuit (not shown), for example, surrounding the housing 10 or embedded within the housing 10, and the large-diameter portion of the rotor body 21 may be disposed proximate to an inlet of the liquid-cooled circuit, and the small-diameter portion of the rotor body 21 may be disposed proximate to an outlet of the liquid-cooled circuit.

Therefore, by designing the rotor 20 to have a varying cross-section along the longitudinal axis X of the rotor body 21, the heat generation and dissipation in the axial direction of the rotor 20 can be adjusted to match the actual heat dissipation conditions, so that the overall temperature of the rotor 20 of the electric machine is balanced, local overheating is avoided, and the power density of the electric machine can be increased.

Of course, the permanent magnets 22 may also be arranged at different radial distances from the longitudinal axis X of the rotor body 21, depending on magnetic field design requirements and the like. In this case, the heat distribution of the rotor 20 can also be adjusted by adjusting the cross-sections of the rotor 20 at different positions on the longitudinal axis X, so as to improve the heat dissipation of the motor, which is not described herein again.

Although the principle of the present invention is explained above by taking a rotor including permanent magnets and a permanent magnet motor as an example, for any motor that uses the electromagnetic induction principle to realize conversion between electrical energy and mechanical energy, if there is "hysteresis loss" and/or "eddy current loss" in the rotor and/or stator to generate heat and the heat dissipation conditions are limited, the heat dissipation conditions can be matched by changing the cross section of the rotor according to the principle of the present invention, so as to reduce the temperature imbalance of the motor, avoid local overheating of the motor, and further improve the load capacity of the motor.

The present application is described in detail above with reference to specific embodiments. It is to be understood that both the foregoing description and the embodiments shown in the drawings are to be considered exemplary and not restrictive of the application. For example, the present application has been described in the preferred embodiments with reference to a permanent magnet motor and its rotor, but it will be apparent to those skilled in the art that various changes or modifications may be made therein without departing from the spirit of the present application, and such changes or modifications do not depart from the scope of the present application.

Claims

1. A rotor (20) of an electrical machine, the rotor (20) comprising:

a rotor body (21), the rotor body (21) being arranged to be fixedly connectable with a shaft (40) of the electrical machine, and the rotor body (21) having a longitudinal axis (X),

characterized in that the rotor body (21) has a varying cross-section at different positions along the longitudinal axis (X).

2. The rotor (20) of claim 1, wherein the rotor (20) further comprises a plurality of permanent magnets (22), the plurality of permanent magnets (22) being embedded within the rotor body (21).

3. The rotor (20) according to claim 2, characterized in that the plurality of permanent magnets (22) are arranged with their geometric centers at the same radial distance from the longitudinal axis (X) of the rotor body (21).

4. The rotor (20) according to any of claims 1 to 3, characterized in that the rotor body (21) is made of different sized ferrous alloy sheets overlapping each other.

5. An electric machine (100), the electric machine (100) comprising:

a stator (30), the stator (30) being provided with a chamber (31);

the rotor (20) of any one of claims 1 to 4, the rotor (20) being housed within a cavity (31) of the stator (30); and

a shaft (40), the shaft (40) being fixedly connected with the rotor body (21).

6. The electrical machine (100) according to claim 5, characterized in that the cavity (31) of the stator (30) has a varying cross section at different positions along the longitudinal axis (X) of the rotor (20).

7. The electric machine (100) according to claim 5, characterized in that the electric machine (100) further comprises a housing (10), the large diameter portion of the rotor body (21) is provided at a position corresponding to a portion of the housing (10) where heat dissipation conditions are favorable, and the small diameter portion of the rotor body (21) is provided at a position corresponding to a portion of the housing (10) where heat dissipation conditions are unfavorable.

8. The electric machine (100) of claim 7, further comprising a cooling fan, wherein the large diameter portion of the rotor body (21) is disposed proximate to the cooling fan and the small diameter portion of the rotor body (21) is disposed distal to the cooling fan.

9. The electric machine (100) of claim 7, wherein the electric machine (100) further comprises a liquid cooling circuit, wherein the large diameter portion of the rotor body (21) is disposed proximate to an inlet of the liquid cooling circuit and the small diameter portion of the rotor body (21) is disposed proximate to an outlet of the liquid cooling circuit.