JP2017085783A - Rotary electric machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotary electric machine which inhibits demagnetization of magnets while reducing costs.SOLUTION: A rotary electric machine includes: a stator; a rotor core 21; neodymium magnets 22; and first ferrite magnets 23. The neodymium magnets 22 are housed in housing holes 212 of the rotor core 21. Each first ferrite magnet 23 covers a first circumferential end part 221 on a radial outer surface of the neodymium magnet 22.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a rotating electrical machine.

  A rotating electric machine is used as a power source in hybrid cars and electric cars. Note that hybrid cars and electric vehicles widely employ IPM (Interior Permanent Magnet) motors in which a permanent magnet is embedded in a rotor core as a rotating electrical machine. When a reverse magnetic field by a stator coil acts on this permanent magnet, there is a problem that demagnetization occurs at both ends of the permanent magnet in a direction perpendicular to the magnetic field (see Patent Document 1).

Japanese Patent No. 4466682

  In order to prevent the demagnetization of the permanent magnet as described above, for example, a countermeasure such as embedding a magnet added with dysprosium in the rotor core is taken. However, since dysprosium is expensive, there arises a problem of high cost.

  An object of the present invention is to suppress demagnetization of a magnet while suppressing cost.

  A rotating electrical machine according to an aspect of the present invention includes a stator, a rotor core, a neodymium magnet, and a first ferrite magnet. The rotor core has a receiving hole extending in the axial direction. The rotor core is disposed so as to be rotatable about the rotation axis on the radially inner side of the stator. The neodymium magnet is accommodated in the accommodation hole. The first ferrite magnet covers the first end portion in the circumferential direction on the radially outer surface of the neodymium magnet.

  According to this configuration, since the first ferrite magnet covers the first end portion of the neodymium magnet, demagnetization at the first end portion of the neodymium magnet can be suppressed. In addition, since a ferrite magnet is not so expensive, it is cheaper than adding dysprosium to a neodymium magnet. Further, the ferrite magnet is difficult to demagnetize in the temperature range where the rotating electrical machine operates. For this reason, demagnetization of the first ferrite magnet can also be suppressed.

  Preferably, the rotating electrical machine further includes a second ferrite magnet. The second ferrite magnet covers the second end portion in the circumferential direction on the radially outer surface of the neodymium magnet. According to this configuration, demagnetization of the second end of the neodymium magnet can also be suppressed.

  Preferably, the central portion in the circumferential direction on the radially outer surface of the neodymium magnet is in contact with the rotor core.

  Preferably, the first ferrite magnet is disposed at a distance from the second ferrite magnet.

  Preferably, the neodymium magnet does not contain dysprosium.

  According to the present invention, it is possible to suppress demagnetization of a magnet while suppressing cost.

The front view of a rotary electric machine. The front view of a rotor core. The enlarged view of a rotor. The front view of the rotor core concerning a modification. The figure which shows the analysis result of the conventional rotary electric machine. The figure which shows the analysis result of the rotary electric machine which concerns on this embodiment. The graph which shows the characteristic of a neodymium magnet and a ferrite magnet.

  Embodiments of a rotating electrical machine according to the present invention will be described below with reference to the drawings. In the following description, the axial direction indicates the direction in which the rotation axis extends. The radial direction indicates the radial direction of a circle around the rotation axis. The circumferential direction indicates the circumferential direction of a circle around the rotation axis.

  As shown in FIG. 1, the rotating electrical machine 100 includes a stator 1 and a rotor 2. A rotor 2 is rotatably disposed inside the stator 1 in the radial direction. The rotating electrical machine 100 functions as, for example, a motor. The rotating electrical machine 100 is specifically an IPM (Interior Permanent Magnet) motor.

  The stator 1 has a substantially cylindrical shape. The stator 1 has a stator core 11 and a stator coil 12 wound around the stator core 11. The stator core 11 is formed by laminating a plurality of electromagnetic steel plates in the axial direction.

  The rotor 2 includes a rotor core 21, a plurality of neodymium magnets 22, a plurality of first ferrite magnets 23, and a plurality of second ferrite magnets 24. The rotor 2 is configured to be rotatable about the rotation axis O on the radially inner side of the stator 1.

  The rotor core 21 is substantially cylindrical and has a mounting hole 211 extending in the axial direction. An output shaft is attached to the attachment hole 211. The rotor core 21 is formed by laminating a plurality of electromagnetic steel plates in the axial direction. The rotor core 21 is disposed so as to be rotatable about the rotation axis O on the radially inner side of the stator 1.

  FIG. 2 is a front view showing the rotor core 21. As shown in FIG. 2, the rotor core 21 has a plurality of pairs of accommodation holes 212 and a plurality of bridge portions 213. Each accommodation hole 212 extends in the axial direction. The respective accommodation holes 212 are arranged at intervals in the circumferential direction. In detail, the accommodation hole pair 210 which became a pair via the bridge part 213 is arrange | positioned at intervals with the adjacent accommodation hole pair 210. As shown in FIG. Each accommodation hole 212 is arranged at the outer peripheral end of the rotor core 21.

  The two accommodation holes 212 that are paired are spaced apart from each other in the circumferential direction. A bridge portion 213 is disposed between the two accommodation holes 212. The bridge portion 213 extends in the radial direction. The pair of accommodation holes 212 are arranged in a V shape when viewed in the axial direction.

  FIG. 3 is an enlarged view showing details of the rotor 2. As shown in FIG. 3, each neodymium magnet 22 is accommodated in the accommodation hole 212. Each neodymium magnet 22 extends in the axial direction. The pair of neodymium magnets 22 are arranged in a V shape when viewed in the axial direction. The radially outer side surface of the neodymium magnet 22 has a first end 221, a second end 222, and a center 223 in the circumferential direction. In the present embodiment, the first end portion 221 is an end portion on the side away from the bridge portion 213, and the second end portion 222 is an end portion on the bridge portion 213 side. The central portion 223 is a region between the first end 221 and the second end 222. The radially outer surface of the neodymium magnet 22 is a surface facing the radially outer side. That is, the radially outer side surface of the neodymium magnet 22 faces the stator 1 in the radial direction. The neodymium magnet 22 preferably does not contain dysprosium.

  The first ferrite magnet 23 is disposed in the accommodation hole 212. The first ferrite magnet 23 covers the first end 221 on the radially outer side surface of the neodymium magnet 22. The first ferrite magnet 23 extends in the axial direction. Preferably, the first ferrite magnet 23 has substantially the same length as the neodymium magnet 22 in the axial direction. Thus, since the first end 221 of the neodymium magnet 22 is covered with the first ferrite magnet 23, it does not contact the rotor core 21.

  The second ferrite magnet 24 is disposed in the accommodation hole 212. The second ferrite magnet 24 covers the second end 222 of the radially outer surface of the neodymium magnet 22. The second ferrite magnet 24 extends in the axial direction. Preferably, the second ferrite magnet 24 has substantially the same length as the neodymium magnet 22 in the axial direction. That is, the second ferrite magnet 24 has the same configuration as that of the first ferrite magnet 23 except for the arrangement location. As described above, the second end portion 222 of the neodymium magnet 22 is covered with the second ferrite magnet 24 and thus does not contact the rotor core 21.

  The 1st ferrite magnet 23 and the 2nd ferrite magnet 24 are arrange | positioned at intervals in the circumferential direction. For this reason, the central portion 223 of the neodymium magnet 22 is not covered by the first ferrite magnet 23 or the second ferrite magnet 24. For this reason, the central part 223 of the neodymium magnet 22 is in contact with the rotor core 21.

[Modification]
As mentioned above, although embodiment of this invention was described, this invention is not limited to these, A various change is possible unless it deviates from the meaning of this invention.

Modification 1
In the neodymium magnet 22 of the above embodiment, the first end portion 221 is an end portion on the side away from the bridge portion 213 and the second end portion 222 is an end portion on the bridge portion 213 side. Good. That is, the first end portion 221 may be an end portion on the bridge portion 213 side, and the second end portion 222 may be an end portion on the side away from the bridge portion 213. In this case, the first ferrite magnet 23 covers the first end 221 that is the end on the bridge portion 213 side, and the second ferrite magnet 24 covers the second end 222 on the side away from the bridge portion 213.

Modification 2
In the above embodiment, the two accommodation holes 212 are paired, but the accommodation holes 212 may not be paired. For example, as shown in FIG. 4, the accommodation holes 212 may be arranged at equal intervals.

(Example)
FIG. 5 is a diagram showing an electromagnetic analysis result when a neodymium magnet is used alone, and FIG. 6 is a diagram showing an electromagnetic analysis result regarding the neodymium magnet whose both ends are covered with the first and second ferrite magnets. . 5 and 6, the numerals in the drawings indicate the residual magnetic flux density (T: Tesla) at the locations indicated by arrows. FIG. 7 is a graph showing the magnetic flux density and magnetic field strength of each magnet. In FIG. 7, line X shows the characteristics of the neodymium magnet, and line Y shows the characteristics of the ferrite magnet.

  As shown in FIG. 5, when the neodymium magnet is used alone, the residual magnetic flux density at the end of the neodymium magnet is 0.29T. Referring to FIG. 7, when the residual magnetic flux density of the neodymium magnet becomes 0.29 T, it belongs to the irreversible region A. For this reason, it turns out that the edge part of a neodymium magnet is demagnetizing.

  On the other hand, as shown in FIG. 6, the residual magnetic flux density at the end of the neodymium magnet is 0.59T, 0.56T, and 0.58T. When FIG. 7 is seen, even if the residual magnetic flux density of the neodymium magnet becomes 0.59T, 0.56T, and 0.58T, it does not belong to the irreversible region A. For this reason, it turns out that the edge part of a neodymium magnet is not demagnetized. That is, it can be seen that demagnetization at each end of the neodymium magnet can be suppressed by covering both ends with the ferrite magnet. Further, as shown in FIG. 6, the residual magnetic flux density at the end of the ferrite magnet is 0.17T. Referring to FIG. 7, since the ferrite magnet does not have an irreversible region, it does not demagnetize even when the residual magnetic flux density is 0.17T.

1: Stator 2: Rotor 21: Rotor core 22: Neodymium magnet 23: 1st ferrite magnet 24: 2nd ferrite magnet 100: Rotating electrical machine 212: Housing hole 221: 1st end 222: 2nd end 223: Center part O :Axis of rotation

Claims (5)

A stator,
A rotor core having a housing hole extending in the axial direction and arranged rotatably about the rotation axis on the radially inner side of the stator;
A neodymium magnet accommodated in the accommodation hole; a first ferrite magnet covering a first end portion in a circumferential direction on a radially outer surface of the neodymium magnet;
A rotating electrical machine.
A second ferrite magnet covering the second end in the circumferential direction on the radially outer surface of the neodymium magnet;
The rotating electrical machine according to claim 1.
The central portion in the circumferential direction on the radially outer surface of the neodymium magnet is in contact with the rotor core.
The rotating electrical machine according to claim 1 or 2.
The first ferrite magnet is disposed at a distance from the second ferrite magnet.
The rotating electrical machine according to any one of claims 1 to 3.
The neodymium magnet does not contain dysprosium,
The rotating electrical machine according to any one of claims 1 to 4.

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