JP4990599B2 - Permanent magnet rotating electric machine - Google Patents

Description

  The present invention relates to a permanent magnet rotating electrical machine.

It is known that a rotating electrical machine can be highly efficient by using a permanent magnet for generating a field magnetic flux. Recently, a high-efficiency and compact rotating electrical machine can be constructed by using a high-performance magnet to achieve a high magnetic flux density in the gap. In addition, the use of permanent magnet rotating electrical machines has increased due to higher magnet properties and improved technology, and high-performance permanent magnets have been used in high-speed rotating applications and large rotating electrical machines.

High-performance magnets have high conductivity, and in high-speed rotations or large-sized rotating electrical machines, there is a problem that efficiency is reduced due to eddy currents generated in the magnets. In order to solve the problem, Patent Document 1 discloses a technique in which an eddy current of a permanent magnet is reduced by interposing an insulating material between high-performance conductive permanent magnet materials.

However, in the technique described in the above patent, stress is generated due to the difference in thermal expansion coefficient between the insulator and the conductive permanent magnet, and the magnet may be broken. In addition, since the insulating member is interposed between the magnet pieces, it takes time and cost to arrange the insulating member evenly and to perform the construction. Moreover, since the above-mentioned technique arranges the insulating member between the magnet pieces, there arises a problem that the characteristic as a magnet is reduced.
Japanese Patent Laid-Open No. 11-4555

In view of the above problems, the present invention prevents damage to magnets due to heat, further reduces eddy current loss while reducing eddy currents generated in permanent magnets, and further shortens construction time and cost. An object of the present invention is to provide a permanent magnet rotating electrical machine that can perform the above.

The permanent magnet rotating electric machine according to the present invention has a plurality of permanent magnets arranged inside or on the surface of the rotor core, and the rotor circumferential direction is spaced from each other so as to have different magnetic pole directions in the rotor circumferential direction. In order to reduce the eddy current generated in the permanent magnet, the permanent magnet provided in an annular shape on the rotor is arranged in the rotor circumferential direction, the axial direction or the circumferential direction and the shaft. It is composed of a plurality of permanent magnets (magnet piece aggregates) arranged in the direction, and no insulating member is disposed between the magnet pieces.

Specifically, the present invention includes a stator having a plurality of stator salient poles wound with windings, and a rotor that is rotatably held by the stator with a rotation gap. The rotor is adjacent to the rotor core having a plurality of permanent magnet insertion holes arranged in a ring in the circumferential direction of the rotor in the circumferential direction and the plurality of permanent magnet insertion holes in the circumferential direction of the rotor. A permanent magnet inserted in such a way that the insertion holes have different magnetic pole directions, and the permanent magnet is composed of a plurality of magnet pieces arranged side by side, and an inclusion is not arranged between the magnet pieces. Yes, and the magnet piece, to provide a permanent magnet rotating electrical machine is obtained by dividing the same permanent magnet sintered body.

A permanent magnet having an insulator between magnet pieces uses an insulator such as an epoxy resin containing an organic solvent. However, in a vacuum, the organic solvent diffuses at a high temperature and cannot be used. The permanent magnet provided with the magnet piece in the permanent magnet rotating electric machine of the present invention does not diffuse the organic solvent even at high temperature and under vacuum, and can be used without any problem.
In addition, the division of permanent magnets for the purpose of eddy current countermeasures can be damaged due to the difference in expansion coefficient at high temperatures and the heat resistance problem of insulators when there is an insulator between the magnet pieces. is there. According to the present invention, by providing no inclusions between the divided magnet pieces, the stress of the magnet due to the temperature rise is relieved, and an eddy current reducing magnet having heat resistance is provided, and cost and processing time are greatly increased. It became possible to shorten it.

FIG. 1 is a sectional view of a permanent magnet rotating electric machine, and FIG. 2 is a plan view of the permanent magnet rotating electric machine.
In this embodiment, the stator coil has 6 poles and the rotor has 4 permanent magnet poles, but the present invention can be applied to other salient poles.

1 and 2, the permanent magnet rotating electric machine includes a stator 1 and a rotor 2, and the stator 1 includes a stator core 3 and a stator winding 4.
The rotor 2 has a shaft held by a bearing 5 and can freely rotate.
The rotor 2 is provided with holes 6 for inserting a plurality of permanent magnets, and the permanent magnets 7 are inserted and fixed in the holes 6.

The permanent magnet 7 shown in FIGS. 1 and 2 is preferably divided in the circumferential direction and / or the axial direction, and more preferably divided in the axial direction to disperse stress. The permanent magnet 7 may be divided only in the circumferential direction.
Although the number of divisions depends on the length of the rotating machine, it is desirable to divide one magnet normally into 3 to 15 in one direction. In addition, as shown in FIG. 3, the magnetization direction of the magnet piece of 1 row is formed so that it may become the same direction and may become parallel.
The magnet pieces are preferably obtained by cutting and dividing the same permanent magnet sintered body from the standpoint of high magnetization uniformity. The permanent magnet sintered body is a permanent magnet fired body obtained by being molded into a size that can enter the permanent magnet insertion hole 6 and firing.
The permanent magnet sintered body may be annealed prior to split cutting in order to make the magnetization direction uniform. The annealing temperature is preferably 150 to 1000 ° C, more preferably 300 to 900 ° C.
As a method for dividing the permanent magnet sintered body, for example, a diamond cutter, a wire saw,
The method of cut | disconnecting using an outer periphery blade cutting machine etc. is mentioned.
These divided magnets can be individually inserted into the respective holes 6, or can be inserted into the respective holes 6 after the divided magnets are integrated using a fixing member.

For example, as shown in the perspective view of FIG. 4, when the magnet pieces 8 are arranged in the permanent magnet insertion holes 6, the upper and lower rotors can be fixed without arranging inclusions between the plurality of magnet pieces. A method using the lid 10 may be mentioned. By this method, among the magnet pieces 9, it can be fixed particularly in the axial direction.
Moreover, as shown in FIG. 5, the magnet piece 8 is arrange | positioned on the plate 11 for magnet fixation, and it can also be made that there is no inclusion between each magnet piece. Furthermore, as shown in FIG. 6, both the circumferential direction and the axial direction can be fixed by a method in which the periphery is bound by a magnet fixing band 12. The material of the magnet piece fixing material such as the plate-like fixing case 11 and the fixing band 12 may be either a magnetic material or a non-magnetic material as long as it does not affect the generated magnetic field. Examples thereof include aluminum and stainless steel.

As described above, for example, by using the configuration as shown in FIGS. 4 to 6, there is no inclusion between the magnet pieces, so that stress due to the difference in expansion coefficient between the magnet piece and the inclusion at high temperature is increased. It does not occur and it is possible to prevent the magnet from being damaged. Furthermore, since the magnets are divided individually, eddy current loss can be reduced, and further, since no inclusions are provided between the magnet pieces, the number of steps can be greatly shortened.
Therefore, even when a conductive permanent magnet is used, it is possible to provide a permanent magnet that can suppress the generation of stress, reduce eddy currents, and shorten the machining process. Can be provided.
The operating temperature of the permanent magnet rotating electrical machine of the present invention is preferably 50 to 350 ° C., 200
The stress generated inside the magnet can be made extremely small even at high temperature operation of ℃ or higher. If an operating temperature is in the said range, an upper limit can be 350 degreeC.
The permanent magnet rotating electrical machine of the present invention can be particularly suitably used for an electric motor having a rotational speed of 2000 rpm to tens of thousands rpm and an output of 10 kW to 1 MW.

EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to this.
Example 1
A rotating electrical machine having a maximum rotational speed of 7200 rpm as shown in FIG. 2 was used. The stator was composed of a silicon steel plate having a stator salient pole around which a coil was wound. A stator having an outer diameter of 300 mm and an inner diameter of 150 mm was used. A permanent magnet having a size of 60 mm × 16 mm × 150 mm was inserted into each of the four insertion holes of the rotor made of a silicon steel plate.
As the permanent magnet, an Nd—Fe—B magnet having a BHmax of 48 MGOe and a conductive rare earth sintered magnet was used. As shown in FIG. 3, the 60 mm direction of this magnet was divided into 3 parts, and the 150 mm direction was divided into 7 parts to produce magnet pieces. At this time, the inclusions were not inserted between the magnet pieces and inserted into each hole, and fixed with a lid of SUS304.
The temperature rises to 180 ° C, 200 ° C, and 240 ° C while driving by applying a current having a frequency of 85 Hz to 240 Hz corresponding to the rotation speed of 2550 rpm to 7200 rpm to the three-phase windings constituting the stator of the rotating electric machine Then, the damage situation of the rotor was investigated.
The rotor using the permanent magnet provided with the magnet piece did not change at any temperature of 180 ° C., 200 ° C., and 240 ° C.

Comparative Example 1
A rotor was manufactured by processing in the same manner as in Example 1 except that 100 μm of an epoxy adhesive was applied between the magnet pieces and each magnet piece was fixed. We assembled a rotating electrical machine equipped with this rotor, applied a current of a frequency corresponding to each rotation speed to the three-phase windings applied to the rotating electrical machine to drive the temperature, and investigated the damage of the rotor at that time. . There was no change at 180 ° C., discoloration at 200 ° C., and separation between the magnet pieces at 240 ° C.

Example 2
A rotary electric machine having a cross-sectional shape as shown in FIG. 2 was used. The axial length of the iron core was 150 mm. A permanent magnet having a size of 52 mm × 7.5 mm × 150 mm was inserted into each of four insertion holes of a rotor made of a silicon steel plate having an outer diameter of 200 mm. The rated output of this rotating electrical machine was 50 kW at a rated current of 200 A. As in Example 1, the stator having an outer diameter of 300 mm had a stator salient pole around which a coil was wound, and was composed of a silicon steel plate.
As a permanent magnet, an Nd—Fe—B sintered magnet having a BHmax of 48 MGOe was used, and as shown in FIG. 3, 52 mm was divided into 3 parts and 150 mm was divided into 7 parts to produce magnet pieces. The divided magnet pieces were gathered again without providing inclusions between the magnet pieces, and the ends of the obtained magnets were covered with a cover of SUS304, and the cover was fixed to the rotor with bolts.
A sine wave alternating current with a rated current was applied to the three-phase windings arranged on the stator of the rotating electrical machine, and the rotating electrical machine was operated at temperatures of 20 ° C., 180 ° C., 200 ° C., and 240 ° C. The rotational speed was set to 2550 rpm, which is the rated rotational speed.
Thereafter, the magnet was taken out from the insertion hole, each magnet piece was fixed with a band, and the torsional fracture strength was measured with a load cell. The torsion breaking strength is a force required to break the magnet central part by twisting in a state where both ends of the magnet are fixed. The measurement was performed 4 times, and the average value was calculated. The results are shown in Table 1.

Comparative Example 2
When collecting the divided magnet pieces, a magnet was produced under the same conditions as in Example 2 except that 80 μm of epoxy adhesive was applied between the magnet pieces and each magnet piece was fixed. Drove. Thereafter, the torsional fracture strength of the magnet was measured under the same conditions as in Example 2. The results are shown in Table 1.

  From Table 1, it was found that in Example 2 having no inclusions between the magnet pieces, stress fracture due to an increase in the operating temperature was remarkably suppressed as compared with Comparative Example 2 having inclusions between the magnet pieces.

Sectional drawing of a permanent magnet rotary electric machine is shown. The top view of a permanent magnet rotary electric machine is shown. The top view of the magnetic pole direction of each magnet piece in one permanent magnet insertion hole is shown. The perspective view of a rotor and the example of the insertion method and fixing method of a magnet piece to a magnet insertion hole are shown. An example of a magnet piece fixing method will be shown. The other example of the fixing method of a magnet piece is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stator 2 Rotor 3 Stator iron core 4 Stator winding 5 Bearing 6 Permanent magnet insertion hole 7 Permanent magnet 8 Magnet piece 9 Between magnet pieces 10 Rotor lid 11 Magnet fixing plate 12 Magnet fixing band

Claims (3)

A stator having a plurality of stator salient poles wound with windings;
A rotor rotatably held by the stator with a rotation gap;
The rotor is
A rotor core having therein a plurality of permanent magnet insertion holes arranged in an annular manner at intervals in the circumferential direction of the rotor;
A permanent magnet inserted into the plurality of permanent magnet insertion holes so as to have different magnetic pole directions in insertion holes adjacent to the circumferential direction of the rotor,
The permanent magnet is composed of a plurality hotel has been magnet pieces, have a structure that does not place the inclusions magnet pieces,
The permanent magnet rotating electric machine , wherein the magnet pieces are obtained by dividing the same permanent magnet sintered body .   The permanent magnet rotating electric machine according to claim 1, wherein the permanent magnet includes a plurality of magnet pieces arranged side by side in a circumferential direction and / or an axial direction of the rotor. The permanent magnet rotating electric machine according to claim 1, wherein the permanent magnet includes a plurality of magnet pieces provided side by side in the axial direction of the rotor.

Images