Rotor structure

Abstract

To provide a rotor structure capable of reducing the magnetic flux directed toward a rotor shaft and increasing the magnetic flux directed toward a stator.SOLUTION: A structure of rotor 100 includes a rotor yoke 101 composed of magnetic material and provided around a rotor shaft 10, a plurality of permanent magnets 110 that is provided at predetermined angular intervals within the rotor yoke 101 along the circumferential direction of the rotor yoke 101 and magnetized in the radial direction, and a rotor cover 120 that is composed of a magnetic material, covers the axial end face of the rotor yoke 101, and covers a region of the outer peripheral surface of the rotor yoke 101 that is adjacent to the end face.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to the structure of a rotor used in an electric motor, and particularly to the structure of a rotor used in an embedded structure permanent magnet synchronous motor.

Background Art

[0002] In an embedded structure permanent magnet synchronous motor, a part of the magnetic flux that originally flows from the rotor to the stator may flow toward the rotation axis instead of from the rotor to the stator and circulate between the rotor and the rotation axis. As a result, there has been a problem of a decrease in the efficiency of the motor. In addition, the magnetic flux toward the rotation axis may affect various components such as bearings, encoders, and electromagnetic brakes, and countermeasures such as magnetic shields have been required. In order to reduce the magnetic flux that circulates within the rotor without flowing toward the stator, it has been conventionally known to provide a space with a high magnetic resistance called a flux barrier within the rotor yoke. A rotor having this type of flux barrier is disclosed in Patent Document 1 below.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1 above, a technique for reducing the magnetic flux that circulates near the outer periphery of the rotor by a flux barrier is disclosed in an embedded structure permanent magnet synchronous motor in which a plurality of permanent magnets are arranged in the circumferential direction.

[0005] However, in the technology disclosed in Patent Document 1, it is impossible to address the phenomenon where magnetic flux flows toward the rotation axis instead of toward the stator near the end face of the rotor of the buried permanent magnet synchronous motor, and magnetic flux circulates between the rotor and the rotation axis.

[0006] Therefore, it is desired to reduce the magnetic flux flowing from near the end face of the rotor of the buried permanent magnet synchronous motor toward the rotation axis and make more magnetic flux from the rotor flow toward the stator.

[0007] An object of the present invention is to provide a rotor structure capable of reducing the magnetic flux from the rotor toward the rotation axis and increasing the magnetic flux toward the stator.

Means for Solving the Problems

[0008] The rotor structure according to this invention includes a rotor yoke provided around the rotation axis and composed of a magnetic material, a plurality of permanent magnets provided at predetermined angular intervals in the rotor yoke along the circumferential direction of the rotor yoke and magnetized in the radial direction, and a rotor cover composed of a magnetic body that covers the axial end face of the rotor yoke and covers a region of the outer peripheral surface of the rotor yoke close to the end face.

[0009] In the rotor structure according to this invention, the rotor cover may be formed by an annular flat portion that covers the axial end face of the rotor yoke and a cylindrical portion provided at the outer peripheral portion of the annular flat portion that covers a region of the outer peripheral surface close to the end face.

[0010] In the rotor structure according to this invention, the annular flat portion may include flux barriers respectively formed in regions where the plurality of permanent magnets are adjacent.

[0011] In the rotor structure according to this invention, the flux barrier may be formed by a hollow hole provided in the rotor yoke.

[0012] In the rotor structure according to the present invention, the flux barrier may be formed in a shape in which the circumferential width becomes narrower toward the inner side in the radial direction. In the rotor structure according to the present invention, the rotor cover may be attached by being adhered to the end face of the rotor yoke or being press-fitted into the rotating shaft.

Advantages of the Invention

[0013] The rotor structure according to the present invention includes a rotor yoke provided around a rotating shaft and made of a magnetic material, a plurality of permanent magnets provided at predetermined angular intervals in the rotor yoke along the circumferential direction of the rotor yoke and magnetized in the radial direction, and a rotor cover made of a magnetic material that covers the axial end face of the rotor yoke and covers a region of the outer peripheral surface of the rotor yoke close to the end face. That is, since the axial end face of the rotor yoke and the region of the outer peripheral surface of the rotor yoke close to the end face are covered by the rotor cover made of a magnetic material, the magnetic flux from the rotor toward the rotating shaft is reduced, and the magnetic flux from the rotor toward the stator is increased.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments of the rotor structure of the present invention (hereinafter referred to as "the structure of rotor 100") will be described with reference to the drawings. In each figure, the same parts are denoted by the same reference numerals.

[0016] Embodiment 1. First, the structure of rotor 100 in Embodiment 1 will be described with reference to FIGS. 1 to 3. FIG. 1 is a configuration diagram showing the structure of rotor 100 according to Embodiment 1. FIG. 2 is a cross-sectional view showing a cross-section taken along line II-II of FIG. 1. FIG. 3 is a perspective view showing a rotor cover 120 used for rotor 100 according to Embodiment 1.

[0017] [Structure of Rotor 100] Rotor 100 is used as a rotor in an embedded structure permanent magnet synchronous motor (hereinafter referred to as "motor"). Rotor 100 mainly includes a rotor yoke 101, a permanent magnet 110, and a rotor cover 120.

[0018] The rotor yoke 101 is composed of a magnetic material such as laminated electromagnetic steel sheets, and is provided around the rotation shaft 10 of the motor and inside the stator 200. The permanent magnet 110 is embedded in the rotor yoke 101 along the circumferential direction of the rotor yoke 101. A plurality of permanent magnets 110 are provided in the rotor yoke 101 at a predetermined angular interval. The plurality of permanent magnets 110 are magnetized in the radial direction so as to have different polarities (hereinafter referred to as different polarities) alternately. Here, the direction along the radius of the rotor yoke 101 is defined as the "radial direction", and the direction along the rotation direction of the rotor yoke 101 is defined as the "circumferential direction".

[0019] The rotor cover 120 is made of a magnetic material and is configured to cover the axial end face of the rotor yoke 101 and cover the region of the outer peripheral surface of the rotor yoke 101 close to the end face. Here, the direction along the axis of the rotating shaft 10 is defined as the "axial direction". The rotor cover 120 is composed of a first rotor cover 120a (see (a) of FIG. 3) and a second rotor cover 120b (see (b) of FIG. 3). The first rotor cover 120a covers one axial end face of the rotor yoke 101. The second rotor cover 120b covers the other axial end face of the rotor yoke 101. The first rotor cover 120a and the second rotor cover 120b have an annular flat portion 121 and a cylindrical portion 122. The annular flat portion 121 is configured to cover the axial end face of the rotor yoke 101. The cylindrical portion 122 is provided on the outer peripheral portion of the annular flat portion 121 and is configured to cover the region of the outer peripheral surface of the rotor yoke 101 close to the end face. The rotor cover 120 is adhered to the axial end face of the rotor yoke 101 or press-fitted into the rotating shaft 10 for attachment. Thereby, the rotor cover 120 prevents the permanent magnet 110 from coming off the rotor yoke 101. Only the annular flat portion 121 of the rotor cover 120 may be adhered to the rotor yoke 101, or both the annular flat portion 121 and the cylindrical portion 122 may be adhered to the rotor yoke 101.

[0020] [Explanation of magnetic flux] Hereinafter, with reference to FIGS. 4 and 5, the difference between the comparative example and the first embodiment will be described with respect to the magnetic flux from the rotor 100 to the stator 200. FIG. 4 is an explanatory diagram schematically showing the magnetic flux from the rotor 100A in the comparative example. FIG. 5 is an explanatory diagram schematically showing the magnetic flux from the rotor 100 in the first embodiment.

[0021] In the rotor 100A of the comparative example, as shown in FIG. 4, most of the magnetic flux φorg from the outer peripheral surface of the rotor yoke 101 goes toward the opposing stator 200. On the other hand, the magnetic flux φbk from the end of the outer peripheral surface of the rotor yoke 101 heads toward the rotation shaft 10 instead of toward the stator 200. That is, the magnetic flux circulates along a path such as the N pole of the permanent magnet 110, the end of the outer peripheral surface of the rotor yoke 101, the rotation shaft 10, the rotor yoke 101, and the S pole of the permanent magnet 110. As a result, the magnetic flux φorg from the rotor 100A toward the stator 200 decreases, causing a problem of a decrease in the efficiency of the motor. In addition, the magnetic flux φbk toward the rotation shaft 10 may magnetically affect various components such as bearings, encoders, and electromagnetic brakes (not shown) provided in the vicinity of the rotation shaft 10. For this reason, it is necessary to provide magnetic shielding for various components such as this type of bearing, encoder, and electromagnetic brake.

[0022] In FIG. 5, most of the magnetic flux φorg from the outer peripheral surface of the rotor 100 of Embodiment 1 heads toward the opposing stator 200 as in FIG. 4. On the other hand, the region of the outer peripheral surface of the rotor yoke 101 close to the end face is covered by the cylindrical portion 122 of the rotor cover 120. The outer peripheral surface of the cylindrical portion 122 has a shorter distance to the stator 200 than the outer peripheral surface of the rotor 100 and a longer distance to the rotation shaft 10 than the outer peripheral surface of the rotor 100 due to the thickness of the cylindrical portion 122. For this reason, the magnetic flux from the region of the outer peripheral surface of the rotor yoke 101 close to the end face heads toward the stator 200 as the magnetic flux φfwd via the cylindrical portion 122.

[0023] As a result, the rotor 100 of Embodiment 1 can reduce the magnetic flux from the rotor yoke 101 toward the rotation shaft 10 and increase the magnetic flux from the rotor 100 toward the stator 200 as compared with the rotor 100A of the comparative example. For this reason, it is possible to eliminate the decrease in the efficiency of the motor caused by the decrease in the magnetic flux φorg from the rotor 100 toward the stator 200. And in order not to generate the magnetic flux from the rotor 100 toward the rotation shaft 10, it is possible to avoid magnetically affecting various components such as bearings, encoders, and electromagnetic brakes (not shown) provided in the vicinity of the rotation shaft 10. For this reason, magnetic shielding and the like become unnecessary.

[0024] [Effects Obtained by Embodiment 1] The rotor 100 according to Embodiment 1 includes a rotor yoke 101, permanent magnets 110, and a rotor cover 120. The rotor yoke 101 is provided around the rotation axis 10 and is made of a magnetic material. A plurality of permanent magnets 110 are provided in the rotor yoke 101 at predetermined angular intervals along the circumferential direction of the rotor yoke 101 and are magnetized in the radial direction. The rotor cover 120 is made of a magnetic material and is configured to cover the axial end face of the rotor yoke 101 and the region of the outer peripheral surface close to the end face. Here, since the region of the outer peripheral surface of the rotor yoke 101 close to the end face is covered by the rotor cover 120, the distance to the stator 200 is shortened. Therefore, the magnetic flux from the region of the outer peripheral surface of the rotor yoke 101 close to the end face travels toward the stator 200 through the cylindrical portion 122. That is, since the axial end face of the rotor yoke 101 and the region of the outer peripheral surface of the rotor yoke 101 close to the end face are covered by the rotor cover 120 made of a magnetic material, the magnetic flux from the rotor 100 toward the rotation axis 10 is reduced, and the magnetic flux from the rotor 100 toward the stator 200 is increased.

[0025] In the rotor 100 according to Embodiment 1, the rotor cover 120 is formed by an annular planar portion 121 that covers the axial end face of the rotor yoke 101 and a cylindrical portion 122 that is provided on the outer peripheral portion of the annular planar portion 121 and covers the region of the outer peripheral surface close to the end face. Here, the region of the outer peripheral surface of the rotor yoke 101 close to the end face is covered by the cylindrical portion 122 of the rotor cover 120. Due to the thickness of the cylindrical portion 122, the distance from the outer peripheral surface of the cylindrical portion 122 to the stator 200 is shorter than that from the outer peripheral surface of the rotor 100, and the distance from the outer peripheral surface of the cylindrical portion 122 to the rotation axis 10 is longer than that from the outer peripheral surface of the rotor 100. Therefore, the magnetic flux from the region of the outer peripheral surface of the rotor yoke 101 close to the end face travels toward the stator 200 through the cylindrical portion 122. That is, the axial end face of the rotor yoke 101 and the region of the outer peripheral surface of the rotor yoke 101 close to the end face are covered by the rotor cover 120 having the annular flat portion 121 and the cylindrical portion 122, so that the magnetic flux from the rotor 100 toward the rotating shaft 10 is reduced and the magnetic flux from the rotor 100 toward the stator 200 is increased. In the rotor 100 according to the first embodiment, the rotor cover 120 is adhered to the axial end face of the rotor yoke 101 or press-fitted into the rotating shaft 10 and attached. Thereby, the rotor cover 120 prevents the permanent magnet 110 from coming off the rotor yoke 101.

[0026] Embodiment 2. The structure of the rotor 100 in the second embodiment will be described with reference to FIGS. 6 to 8. FIG. 6 is a configuration diagram showing the structure of the rotor 100 according to the second embodiment. FIG. 7 is a cross-sectional view showing a cross-section taken along line VII-VII of FIG. 6. FIG. 8 is a perspective view showing the rotor cover 120 used for the rotor 100 according to the second embodiment.

[0027] [Structure of Rotor 100] The rotor 100 mainly includes a rotor yoke 101, a permanent magnet 110, a rotor cover 120, and a flux barrier 125. The flux barrier 125 is provided on the annular flat portion 121 of the rotor cover 120. The flux barriers 125 are each formed as hollow holes in a region of the annular flat portion 121 where a plurality of permanent magnets 110 are adjacent to each other.

[0028] [Explanation of Magnetic Flux] The plurality of permanent magnets 110 are magnetized in the radial direction so as to have different polarities alternately. For this reason, there is a possibility that magnetic flux circulates between adjacent permanent magnets 110 through the rotor cover 120 which is a magnetic body. When such magnetic flux circulating between adjacent permanent magnets 110 is generated, the magnetic flux φorg toward the stator 200 will decrease. Therefore, as shown in FIGS. 6 to 8, in the region of the annular planar portion 121 where a plurality of permanent magnets 110 are adjacent to each other, a flux barrier 125 is formed as a hollow hole of an air layer having a higher magnetic resistance than the rotor cover 120. Such a flux barrier 125 formed by such a hollow hole has a higher magnetic resistance than a magnetic material. Therefore, in the case of the rotor 100 having the flux barrier 125, it is possible to reduce the magnetic flux circulating through the rotor cover 120 between adjacent permanent magnets 110 and increase the magnetic flux directed from the rotor 100 to the stator 200. For this reason, it is possible to eliminate the reduction in the efficiency of the motor caused by the decrease in the magnetic flux φorg directed from the rotor 100 to the stator 200.

[0029] [Modification Example of Rotor Cover] A modification example of the rotor cover 120 used for the rotor 100 of the second embodiment will be described with reference to FIG. 9. FIG. 9 is an explanatory diagram showing a modification example of the rotor cover 120 used in the structure of the rotor 100 according to the second embodiment. On the annular planar portion 121 of the rotor cover 120, a flux barrier 125 having a shape in which the circumferential width becomes narrower toward the inner side in the radial direction is provided. That is, the flux barrier 125 is formed in a trapezoidal shape having the inner side in the radial direction as the upper base and the outer side in the radial direction as the lower base so as to match the shape of the region where a plurality of permanent magnets 110 are adjacent to each other. Although rectangular permanent magnets 110 are used in FIG. 9, when the shape of the permanent magnet 110 is different, the shape of the flux barrier 125 may be changed so as to match the shape of the region where the permanent magnets 110 are adjacent to each other. In the case of the rotor 100 having such a flux barrier 125, it is possible to effectively reduce the magnetic flux circulating through the rotor cover 120 between adjacent permanent magnets 110 and increase the magnetic flux directed from the rotor 100 to the stator 200.

[0030] [Effects Obtained by the Second Embodiment] The rotor 100 according to the second embodiment includes a rotor yoke 101, permanent magnets 110, a rotor cover 120, and a flux barrier 125. The rotor yoke 101 is provided around the rotation axis 10 and is made of a magnetic material. A plurality of permanent magnets 110 are provided in the rotor yoke 101 at predetermined angular intervals along the circumferential direction of the rotor yoke 101 and are magnetized in the radial direction. The rotor cover 120 is made of a magnetic material and is formed by an annular flat portion 121 that covers the axial end face of the rotor yoke 101 and a cylindrical portion 122 that is provided on the outer peripheral portion of the annular flat portion 121 and covers a region of the outer peripheral surface close to the end face. The flux barriers 125 are each formed in the annular flat portion 121 in a region where a plurality of permanent magnets 110 are adjacent to each other, having a higher magnetic resistance than the rotor cover 120. When the rotor 100 has the flux barriers 125 as described above, the magnetic flux circulating between adjacent permanent magnets 110 through the rotor cover 120 can be reduced, and the magnetic flux from the rotor 100 toward the stator 200 can be increased. Therefore, it is possible to eliminate the reduction in the efficiency of the motor caused by the decrease in the magnetic flux φorg from the rotor 100 toward the stator 200.

[0031] In the structure of the rotor 100 according to the second embodiment, the flux barrier 125 is formed by a hollow hole provided in the rotor yoke. Here, the flux barrier 125 is formed as a space of an air layer having a higher magnetic resistance than the rotor cover 120 by a hollow hole provided in the rotor yoke 101. When the rotor 100 has the flux barriers 125 formed by the hollow holes as described above, the magnetic flux circulating between adjacent permanent magnets 110 through the rotor cover 120 can be effectively reduced by the flux barriers 125, and the magnetic flux from the rotor 100 toward the stator 200 can be increased. Further, by making the flux barrier 125 a hollow hole, the moment of inertia of the rotor 100 can be reduced.

[0032] In the structure of the rotor 100 according to the second embodiment, the flux barrier 125 is formed in a shape in which the circumferential width becomes narrower toward the inner side in the radial direction. That is, the flux barrier 125 is formed to match the shape of the region where the plurality of permanent magnets 110 are adjacent to each other. When the rotor 100 has the flux barrier 125 that matches the shape between the adjacent permanent magnets 110 as described above, the magnetic flux circulating through the rotor cover 120 between the adjacent permanent magnets 110 can be effectively reduced, and the magnetic flux from the rotor 100 toward the stator 200 can be increased.

[0033] Other embodiments. In the above-described first and second embodiments, the rotor cover 120 is provided on both end faces of the rotor yoke 101. However, when the purpose is to eliminate magnetic problems with other components, it is also possible to provide the rotor cover 120 only on the side where there are other components that are easily affected by magnetism.

Description of reference numerals

[0034] 10 Rotation axis, 100 Rotor, 101 Rotor yoke, 110 Permanent magnet, 120 Rotor cover, 121 Annular flat portion, 122 Cylindrical portion, 125 Flux barrier, 200 Stator, φbk Magnetic flux from the end of the rotor yoke toward the rotation axis, φfwd Magnetic flux from the end of the rotor yoke toward the stator, φorg Magnetic flux from the outer peripheral surface of the rotor yoke toward the stator.

Claims

1. A rotor yoke (101) provided around a rotating shaft (10) and composed of a magnetic material, and a plurality of permanent magnets (110) provided at predetermined angular intervals in the rotor yoke (101) along the circumferential direction of the rotor yoke (101) and magnetized in the radial direction, a rotor cover (120) composed of a magnetic body, covering the axial end face of the rotor yoke (101) and covering a region of the outer peripheral surface of the rotor yoke (101) close to the end face, A rotor structure comprising the above.

2. The rotor cover (120) is an annular flat portion (121) covering the axial end face of the rotor yoke (101), and a cylindrical portion (122) provided at the outer peripheral portion of the annular flat portion (121) and covering a region of the outer peripheral surface close to the end face, The rotor structure according to claim 1 formed by the above.

3. The annular flat portion (121) includes flux barriers (125) respectively formed in regions where the plurality of permanent magnets (110) are adjacent to each other, The rotor structure according to claim 2.

4. The flux barrier (125) is formed by a hollow hole provided in the rotor yoke (101), The rotor structure according to claim 3.

5. The flux barrier (125) is formed in a shape in which the circumferential width becomes narrower toward the inner side in the radial direction, The rotor structure according to claim 3.

6. The rotor cover (120) is adhered to the end face of the rotor yoke (101) or press-fitted onto the rotating shaft (10) for attachment, The rotor structure according to claim 1.

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