JP6440349B2 - Rotating electric machine - Google Patents

Description

  The present invention relates to a rotating electrical machine having a permanent magnet as a field source in a rotor.

In a rotating electrical machine using a rare earth permanent magnet, there are problems such as a reduction in efficiency and an increase in magnet temperature due to eddy current loss caused by leakage magnetic flux interlinking with the permanent magnet. In particular, when a neodymium-based rare earth permanent magnet is used, irreversible demagnetization occurs when exposed to a high temperature of 150 to 200 ° C. Therefore, it has been an important issue to reduce eddy current loss as a heat source. On the other hand, the rotor core shape and the like have been devised in order to reduce the loss generated in the permanent magnet.
On the other hand, in a rotating electrical machine using permanent magnets, irreversible demagnetization of the permanent magnets due to reaction magnetization created by the current flowing in the armature winding is a problem, and a plurality of permanent magnets having different coercive forces are arranged per pole. I have tried to solve it.

  For example, in Japanese Patent Application Laid-Open No. 52-61712 (Patent Document 1), a rotation direction that is easy to demagnetize by a reaction magnetic field by using two types of permanent magnets, a barium ferrite magnet in the rotation advance direction and a strontium ferrite magnet in the delay direction. The delay side is configured to be strong against demagnetizing fields.

  In JP 2009-38930 A (Patent Document 2), a permanent magnet having a low coercivity is sandwiched between permanent magnets from both ends.

JP 52-61712 A JP 2009-38930 A

  However, there are many cases where the paths of the leakage magnetic flux and the main magnetic flux interlinking with the permanent magnet overlap, and it is difficult to effectively reduce only the leakage magnetic flux due to the iron core shape.

  In addition, although there are many prior arts from the viewpoint of coercive force mainly to prevent irreversible demagnetization in terms of improving the characteristics of rotating electrical machines by combining multiple types of permanent magnets, eddy currents generated in permanent magnets There is no prior art from the viewpoint of reducing loss.

  The problem to be solved by the present invention is to provide a rotating electrical machine in which eddy current loss generated in a permanent magnet disposed in a rotor of the rotating electrical machine is reduced and efficiency is improved.

  In order to solve the above-mentioned problems, the present invention is configured such that one rotor magnetic pole is composed of two or more types of rare earth permanent magnets having different residual magnetic flux densities, and per unit area from the magnetic pole center to the rotation advance side and the rotation delay side. The rare earth permanent magnets were arranged so that the residual magnetic flux densities of the magnets differed.

ADVANTAGE OF THE INVENTION According to this invention, the rotary electric machine which reduced the loss of the rotary electric machine and improved efficiency can be provided.

It is an axial sectional view of the rotating electrical machine according to the first embodiment to which the present invention is applied. It is a figure which shows the rotor of the rotary electric machine by Example 1. FIG. It is a figure explaining the relationship between the magnetic flux density in an iron core, and a relative magnetic permeability. It is a figure which shows the time change of the harmonic magnetic flux in the permanent magnet surface in connection with Example 1. FIG. It is a figure which concerns on Example 1 and shows the calculation result by the magnetic field analysis of the eddy current loss which generate | occur | produces in a permanent magnet. It is a figure which shows the rotor of the rotary electric machine by Example 2 to which this invention is applied. FIG. 10 is a view showing a rotor of a rotating electrical machine according to a modification of the second embodiment. It is axial direction sectional drawing of the rotor of the rotary electric machine by Example 3 to which this invention is applied. FIG. 10 is an axial cross-sectional view of a rotor of a rotating electrical machine according to a modification of Example 3. It is axial direction sectional drawing of the rotor of the rotary electric machine by Example 4 to which this invention is applied. It is sectional drawing which looked at the rotary electric machine provided with a permanent magnet in a rotor from the circumferential direction. It is a figure explaining the residual magnetic flux density and coercive force of a permanent magnet. It is axial direction sectional drawing of the rotor of the rotary electric machine by Example 5 to which this invention is applied. It is an axial sectional view of a rotor of a rotating electrical machine showing a modification when Example 1 is applied as a generator.

  Embodiments to which the present invention is applied will be described below with reference to the drawings. Since the present invention relates to a permanent magnet provided in a rotor of a rotating electrical machine, the following description will be mainly made using a cross-sectional view of the rotor. FIG. 11 is a cross-sectional view of a rotating electrical machine having a permanent magnet on a rotor as viewed from the circumferential direction. 1 is a rotor, 2 is a rotor core, 3 is a stator, 4 is a stator core, and 5 is a stator winding. A wire, 9 is a shaft, and 10 is a permanent magnet. In the description of the embodiment, an axial sectional view of the rotary electric machine as viewed in the A-A ′ section in FIG. 11 is mainly used.

  FIG. 2 is a diagram showing a rotor of the rotating electrical machine according to the first embodiment to which the present invention is applied. FIG. 1 is a cross-sectional view of the rotating electrical machine according to the present embodiment viewed from the axial direction in the vicinity of the center in the axial direction of the iron core, that is, in the A-A ′ cross section in FIG. 11.

  As shown in FIG. 2, the rotor 1 of the rotating electrical machine according to the present embodiment has a rotor core 2 and a shaft 9 (see FIG. 11) and a magnet insertion hole 11, which are configured by stacking a plurality of punched steel plates in the axial direction. A plurality of permanent magnets 10 (10a, 10b) are inserted into the structure. The permanent magnet is fixed in the magnet insertion hole 11 using an adhesive or the like, and a resin spacer or the like is also used if necessary. In the cross-sectional view of FIG. 1, 6 is a stator slot, 7 is an air gap, and 8 is a stator core teeth portion.

  In FIG. 2, the present embodiment shows an example of a rotating electrical machine having 4 poles, and a total of four permanent magnets 10 in the circumferential direction and two in the axial direction serve as a rotor as a field source for one pole. It is arranged in a magnet insertion hole 11 provided in the iron core 2. This configuration is symmetrically arranged in a total of four, 90 ° in the rotation direction, and constitutes a field source for four poles. The rotation direction is counterclockwise when viewed from above, and a rare earth permanent magnet 10a having a high residual magnetic flux density is arranged on the rotation advance side, and a rare earth permanent magnet 10b having a low residual magnetic flux density is arranged on the rotation delay side. At this time, the coercive force of the permanent magnet may be equal, or from the viewpoint of preventing demagnetization, one having a higher coercive force may be used, and the residual magnetic flux density is arranged as in this embodiment. If so, the effect of reducing eddy current loss in the permanent magnet can be obtained.

  In this embodiment, it is necessary to arrange a plurality of permanent magnets per pole in the circumferential direction, which is the rotation direction of the rotating electrical machine. However, the number of arrangement may be one in the axial direction. It is better to select appropriately in view of the overall length of the electric machine in the axial direction and manufacturability.

  The principle by which the eddy current loss generated in the permanent magnet is reduced by the arrangement of the permanent magnet shown in this embodiment will be described with reference to FIGS.

  FIG. 3 is a diagram for explaining the relationship between the magnetic flux density in the iron core and the relative magnetic permeability. Based on the characteristics of a typical electromagnetic steel sheet used in a rotating electrical machine, the magnetic flux density acting on the iron core and the relative magnetic permeability at that time. It is shown. The magnetic steel sheet used for the iron core of a rotating electrical machine increases in relative permeability as the magnetic flux density increases from 0, shows the maximum magnetic permeability around 1T, and increases with increasing magnetic flux density in the region of 1T or higher. Decrease. Therefore, when a rare earth permanent magnet having a residual magnetic flux density of 1 T or more is used, the higher the magnetic flux density of the iron core near the permanent magnet, the smaller the relative permeability, that is, the magnetic flux is difficult to pass. On the other hand, when, for example, a ferrite magnet having a small residual magnetic flux density is used, the relative permeability increases in the iron core near the magnet as the magnetic flux density increases, that is, the magnetic flux easily passes.

  Therefore, as shown in FIG. 4, the stator core teeth portion 8 on the rotation advance side where the rare earth permanent magnet 10 a having a high residual magnetic flux density is arranged is compared to the rare earth permanent magnet 10 b on the rotation delay side having a low residual magnetic flux density. And pulsation of magnetic flux due to the difference in magnetic resistance between the stator slot 6, that is, the amplitude becomes small. Therefore, the leakage magnetic flux acting on the permanent magnet is also reduced in amplitude, and eddy current loss caused in the permanent magnet due to the leakage magnetic flux is also reduced. In other words, in the vicinity of the permanent magnet where the leakage magnetic flux often penetrates, the harmonic magnetic flux that penetrates the permanent magnet can be reduced by reducing the relative permeability of the iron core, and the eddy current loss generated in the permanent magnet is reduced.

  The coercive force of a general rare earth permanent magnet is 500 kA / m or more, and the upper limit is about 3000 kA / m as a current product. As the rare earth permanent magnet used in this embodiment, a residual magnetic flux density of 1.0 T or more, a theoretical limit value of 1.6 T, and a coercive force of 500 kA / m or more are effective, and a residual magnetic flux density of 1.2 T and a coercive force of around 1000 kA / m. Is desirable.

  In addition, when a magnet having a high residual magnetic flux density is simply used, the induced voltage increases and the specification is changed. Therefore, it is necessary to reduce the overcurrent loss without changing the specification of the induced voltage. Therefore, it is necessary to adjust the overall induced voltage by configuring one pole of the rotor magnetic pole with two or more types of magnets having different residual magnetic flux densities.

  FIG. 5 shows the result of calculating the eddy current loss of the permanent magnet by magnetic field analysis for the electric motor according to the present embodiment. As a condition in the analysis, in the “conventional” configuration, the residual magnetic flux density of the permanent magnet is 1.15 T, which is the same on both the rotation advance side and the delay side, and in the “invention” configuration, the residual magnetic flux density of the permanent magnet is rotationally advanced. + 10% on the side and -10% on the delay side. Since the amount of magnetic flux per magnetic pole is the same, the output as an electric motor is equivalent. The permanent magnet on the rotation advance side has more leakage flux from the stator to the rotor, so that the eddy current loss is larger on the permanent magnet on the rotation advance side. This is because when operating as an electric motor, the magnetic field created by the current flowing in the stator winding on the stator side rotates slightly ahead of the rotor field.

  Therefore, when operating as a generator, as shown in FIG. 14, a rare earth permanent magnet 10b having a low residual magnetic flux density is arranged on the rotation advance side and a rare earth permanent magnet 10a having a high residual magnetic flux density is arranged on the rotation delay side. The eddy current loss generated in the permanent magnet can be reduced by adopting the reverse configuration of the present embodiment.

  In the case of a generator / motor that uses both a generator and an electric motor, the arrangement of the permanent magnets may be determined mainly depending on whether the generator is operated as a generator or an electric motor.

  Further, in the following embodiments, unless otherwise specified, the description will be made on the assumption that the rotating electrical machine operates as an electric motor.

  As shown in FIG. 5, when the configuration of the present embodiment is used with respect to the conventional configuration, the magnet eddy current loss generated in the permanent magnet can be reduced. The loss is also reduced in the permanent magnet on the rotation delay side, but this is because the relative magnetic permeability in the rotor core on the rotation advance side is reduced, so that the leakage magnetic flux itself entering from the stator to the rotor is reduced. This is because. In this embodiment, the example of the combination of the number of magnetic poles 4 and the number of slots 6 of the stator is shown, but the number of magnetic poles and the number of slots may be other than this.

  As described above, in this embodiment, one pole of the rotor magnetic pole is composed of two or more types of rare earth permanent magnets having different residual magnetic flux densities, and per unit area on the rotation advance side and the rotation delay side from the magnetic pole center. The rare earth permanent magnets were arranged so that the residual magnetic flux densities were different. Thereby, the rotary electric machine which can reduce the eddy current loss which arises in a permanent magnet, can reduce the temperature in a rotary electric machine with high efficiency can be provided.

  FIG. 6 is a diagram illustrating a rotor of a rotating electrical machine according to the second embodiment. FIG. 7 is a view showing a rotor of a rotating electrical machine according to a modification of this example.

  In this embodiment, six permanent magnets 10, two in the circumferential direction and three in the axial direction, are arranged in the magnet insertion holes 11 provided in the rotor core 2 as field sources for the magnetic poles. This configuration is symmetrically arranged in a total of four, 90 ° in the rotation direction, and constitutes a field source for four poles.

  The rotation direction is counterclockwise when viewed from above. In FIG. 6, all of the permanent magnets in the rotation advance direction have high residual magnetic flux density, and all of the permanent magnets in the rotation delay direction have low residual magnetic flux density. 10b.

  When three or more permanent magnets are arranged in the axial direction, as shown in FIG. 6, all of the permanent magnets on the rotational direction advance side are made of the rare earth permanent magnet 10a having a high residual magnetic flux density, and all of the permanent magnets on the rotational delay side are made of the residual magnetic flux density. As shown in FIG. 7, two of the three permanent magnets on the rotational direction leading side are composed of 10a and one of the permanent magnets 10b, and the permanent magnet on the rotational direction lagging side is permanent. Two of the three magnets may be combined as 10b and one as 10a.

  In the present embodiment, the effect can be obtained if the permanent magnet is arranged so that the residual magnetic flux density per unit area on either the rotation advance side or the delay side is increased from the center of the magnetic pole for one magnetic pole. In addition, when a plurality of permanent magnets are arranged in the axial direction, the present invention can also be applied to a case where magnets are combined from adjustments with other design items such as coercive force, and the degree of freedom increases.

  FIG. 8 is an axial sectional view of the rotor of the rotating electrical machine according to the third embodiment. FIG. 9 is an axial sectional view of a rotor of a rotating electrical machine according to a modification of the present embodiment.

  When two or more magnets are arranged in the circumferential direction in a magnet insertion hole with a small size, adhesive or the like does not spread between the magnets, and there is a possibility that sufficient holding strength cannot be obtained. As the output is generated, a load is applied to the permanent magnet in the circumferential direction and the radial direction, and when the holding strength is insufficient, the permanent magnet vibrates in the insertion hole, leading to breakage.

  Therefore, in this embodiment, magnet insertion holes 11 are provided in the rotor core 2 in accordance with the number of permanent magnets arranged in the circumferential direction. Thereby, each permanent magnet can be fixed in the insertion hole with an adhesive or the like, and the holding strength of the magnet can be improved.

  Specifically, in FIG. 8, as a field source for one pole, two magnet insertion holes are provided in the circumferential direction, and the rare earth permanent magnet 10a having a high residual magnetic flux density in the rotational advance direction of each magnet insertion hole is rotated. A rare earth permanent magnet 10b having a low residual magnetic flux density is inserted and fixed in the delay direction. Further, in FIG. 9, as a field source for one pole, three magnet insertion holes are provided in the circumferential direction, and a rare earth permanent magnet 10a having a high residual magnetic flux density is provided in two in the rotational advance direction of each magnet insertion hole. A rare earth permanent magnet 10b having a low residual magnetic flux density is inserted and fixed in the rotation delay direction.

  The distance between the respective magnet insertion holes should be appropriately selected from the viewpoint of strength and leakage flux. This is because the core size between the magnet insertion holes is in a trade-off relationship between strength and effective magnetic flux. In other words, considering the centrifugal force that can be calculated from the rotational speed, it is preferable to make the size as large as possible from the viewpoint of strength according to the steel sheet used, and the leakage magnetic flux that returns to the opposite magnetic pole without the magnetic flux of the permanent magnet reaching the stator From the viewpoint of reducing the amount, the size should be as small as possible.

  As described above, according to this embodiment, the holding strength can be obtained even when a plurality of permanent magnets are arranged in the circumferential direction.

  FIG. 10 is a sectional view in the axial direction of the rotor of the rotating electrical machine according to the fourth embodiment.

  Since it is necessary to select two or more types of magnets having different residual magnetic flux densities in order to implement this embodiment, for example, the coercive force is the same in the relationship between the residual magnetic flux density and the coercive force of the permanent magnet shown in FIG. A magnet having the characteristic 21 and a magnet having the characteristic 22 are combined. That is, it is desirable to select a magnet having a necessary coercive force from the operating temperature of the rotating electrical machine to be applied and the magnetic field acting so that irreversible demagnetization does not occur with respect to the reaction magnetic field.

  On the other hand, the characteristics of the permanent magnet shown in FIG. 12 are manufactured so as to have desired values depending on differences in the manufacturing method, additive elements, magnetization method, and the like of the permanent magnet. Moreover, the straight line in FIG. 12 shows the average value of the characteristic of the magnet manufactured by the same manufacturing method. Therefore, by selecting a permanent magnet manufactured by a similar manufacturing method, there are advantages such as shortening the delivery time of the rotating electrical machine and reducing manufacturing cost. Therefore, when combining the magnet of the characteristic 21 and the magnet of the characteristic 23 on the same straight line, The coercive force of the permanent magnet having the characteristic 23 is smaller than that of the magnet having the characteristic 21, and there is a problem that it is easy to demagnetize.

  Therefore, in the present embodiment, as shown in FIG. 10, a rare earth permanent magnet 10c having a high residual magnetic flux density is disposed on the rotation advance side, and a rare earth permanent magnet 10b having a low residual magnetic flux density is disposed on the rotation delay side. The thickness is made thicker than the permanent magnet 10b. As the characteristics of each permanent magnet, the permanent magnet 10c is a characteristic 23 in FIG. 12, and the permanent magnet 10b is a permanent magnet having the characteristic 21. Thereby, since the coercive force of the permanent magnet 10c having a low coercive force is increased by increasing the thickness, demagnetization can be prevented.

  As described above, according to this embodiment, demagnetization can be prevented even when there is a relatively large difference in coercive force when magnets having different residual magnetic flux densities are selected.

  FIG. 13 is an axial sectional view of a rotor of a rotating electrical machine according to the fifth embodiment.

  In FIG. 13, the rotation direction is the same as that of the first embodiment and the arrangement of the permanent magnets. Further, the flux barrier 12 prevents the magnetic flux from entering the outer diameter side portion of the permanent magnet 10 a having a high residual magnetic flux density of the rotor core 2. Is provided so that the leakage magnetic flux does not easily pass through the permanent magnet 10a.

  According to the present embodiment, it is possible to reduce the eddy current loss of the permanent magnet similar to that of the first embodiment, but further, by implementing the method of reducing the magnetic flux entering the permanent magnet by the iron core shape, Eddy current loss can be further reduced.

  In addition, as a modified example in which the leakage magnetic flux is less likely to pass through the permanent magnet 10a, for example, an asymmetric rotor shape may be used so that the air gap 7 corresponding to the permanent magnet 10a becomes equivalently large.

  Although the embodiments have been described above, the present invention is not limited to the above-described embodiments, and includes various modifications. For example, in the above-described embodiment, the case where two or three permanent magnets in the circumferential direction and two or three permanent magnets in the axial direction are configured as the field source of each magnetic pole of the rotor has been described. However, other configurations may be used. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Moreover, it is also possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 1 ... Rotor, 2 ... Rotor core, 3 ... Stator, 4 ... Stator core 5 ... Stator winding, 6 ... Stator slot, 7 ... Air gap 8 ... Stator core teeth part, 9 ... Shaft 10 DESCRIPTION OF SYMBOLS 10a, 10b, 10c ... Permanent magnet 11 ... Magnet insertion hole, 12 ... Flux barrier.

Claims (4)

A stator winding, a stator core around which the stator winding is wound, a rotor disposed concentrically on the inner peripheral side of the stator core, and a permanent magnet serving as a field source in the rotor In rotating electrical machines,
The rotor has a rotor core made of a material whose relative permeability decreases with an increase in the magnetic flux density above a predetermined magnetic flux density,
One pole of the rotor magnetic pole is composed of two or more types of rare earth permanent magnets having different residual magnetic flux densities, and the plurality of rare earth elements are arranged such that the residual magnetic flux density on the rotation advance side from the magnetic pole center is higher than that on the rotation delay side. A rotating electric machine, wherein a permanent magnet is arranged and operated as an electric motor. A stator winding, a stator core around which the stator winding is wound, a rotor disposed concentrically on the inner peripheral side of the stator core, and a permanent magnet serving as a field source in the rotor In rotating electrical machines,
The rotor has a rotor core made of a material whose relative permeability decreases with an increase in the magnetic flux density above a predetermined magnetic flux density,
One pole of the rotor magnetic pole is composed of two or more types of rare earth permanent magnets having different residual magnetic flux densities, and the plurality of rare earths are set so that the residual magnetic flux density on the rotation delay side from the magnetic pole center is higher than that on the rotation advance side. A rotating electric machine characterized in that a permanent magnet is arranged and operated as a generator. The rotating electrical machine according to claim 1 or 2,
A rotating electric machine characterized in that among the plurality of rare earth permanent magnets, the magnet thickness of a rare earth permanent magnet having a high residual magnetic flux density is made thicker than that of a rare earth permanent magnet having a low residual magnetic flux density. The rotating electrical machine according to claim 1 or 2,
A rotating electrical machine comprising a flux barrier for preventing magnetic flux from entering an outer diameter side rotor core of a rare earth permanent magnet having a high residual magnetic flux density among the plurality of rare earth permanent magnets.

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