JP2015223079A - Rotor and spork-type ipm permanent magnetic rotating machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotor for a permanent magnetic rotating machine and the permanent magnetic rotating machine having high output and demagnetization resistance.SOLUTION: A rotor used for a permanent magnetic rotating machine 1 comprises: a rotor 10 comprising a rotor core 11, and a plurality of permanent magnets 12 embedded in each of a plurality of insertion holes formed in the rotor core 11; and a stator 20 comprising a stator core 21 having a plurality of slots 22, and winding wire 23 wound around the stator core 21. The permanent magnets 12 are in a form of a rectangular parallelepiped with two sides parallel to a radial direction of the rotor on a surface perpendicular to a rotation axis of the rotor 10, and is in a form of a rectangular having four side edges parallel to an axis direction, and at least one angular portion of four angular portions including each side edge of the four side edges of the permanent magnet 12 has stronger coercive force than that of a center inside the rectangular parallelepiped, and is placed in the insertion hole such that the angular portion is on a stator side and in a rear of the rotor 10 in a rotating direction. Also provided is the permanent magnetic rotating machine comprising the rotor.

Description

  The present invention relates to a permanent magnet-type rotating machine (so-called magnet) in which a rotor in which a plurality of permanent magnets are embedded in a rotor core and a stator in which a winding is wound around a stator core having a plurality of slots are arranged via a gap. The present invention relates to a rotor used in an embedded structure rotating machine and an IPM (interior permanent magnet) rotating machine, and a permanent magnet rotating machine using the same.

  Nd-based sintered magnets are increasingly used for their excellent magnetic properties. In recent years, in the field of rotating machines such as motors and generators, permanent magnet type rotating machines using Nd-based sintered magnets have been developed along with reductions in the size, performance, and energy saving of equipment. Among them, the IPM rotating machine with a magnet embedded in the rotor can utilize the reluctance torque due to the magnetization of the rotor yoke in addition to the torque due to the magnetization of the magnet. Is progressing. Since the IPM rotating machine has magnets embedded in the rotor yoke made of silicon steel plate, etc., the magnets do not pop out even during rotation, and the mechanical safety is high, and the current phase is controlled. High-torque operation and a wide range of speeds are possible, resulting in energy-saving, high-efficiency, and high-torque motors. In recent years, the use as electric motors, hybrid cars, high-performance air conditioners, industrial motors, electric motors and generators has been rapidly expanding.

  In general, a permanent magnet in a rotating machine is easily demagnetized due to a demagnetizing field caused by a winding, and a coercive force of a certain level or more is required. In addition, since the coercive force decreases as the temperature rises, a magnet having a higher room temperature coercive force is required when used at high temperatures such as for hybrid vehicles. On the other hand, the residual magnetic flux density, which is an index of the magnitude of the magnetic force, directly affects the motor output, and is required to be as high as possible.

  The coercive force and the residual magnetic flux density of the Nd-based sintered magnet are in a trade-off relationship, and the residual magnetic flux density decreases as the coercive force is increased. For this reason, when a magnet having a coercive force higher than necessary is used in a rotating machine, there is a problem that the motor output decreases.

  In recent years, as seen in Patent Document 1, Dy (dysprosium) and Tb (terbium) are diffused from the surface of a sintered magnet by a coating method or a sputtering method to maintain the residual magnetic flux density without decreasing. A technique for improving the magnetic force has been reported. In these methods, since Dy and Tb can be efficiently concentrated at the grain boundary, it is possible to increase the coercive force with almost no decrease in the residual magnetic flux density. Further, since the added Dy and Tb diffuse to the inside as the magnet size is smaller, this method is applied to a small or thin magnet.

  Patent Document 2 reports a so-called surface magnet type rotating machine (SPM (surface permanent magnet) rotating machine) in which magnets obtained by diffusing Dy and Tb are arranged on the surface of a rotor. In Patent Document 2, increasing the coercive force of the thin portion of the D-shaped magnet is effective for preventing demagnetization, and such a magnet can be obtained by diffusing Dy or Tb. Has been reported.

  Patent Document 3 reports a method for manufacturing a magnet in which Dy or Tb is diffusion-treated. Further, an increase in coercive force is recognized from the magnet surface to a depth of 6 mm, and the coercive force of the magnet surface is 500 kA / m in the case of Dy diffusion and 800 kA / m in the case of Tb diffusion, compared to the coercive force of the central portion in the magnet. m is reported to be high.

International Publication No. 2006 / 043348A1 JP 2008-61333 A JP 2010-135529 A JP 2004-173491 A

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a rotor for a permanent magnet type rotating machine and a permanent magnet type rotating machine having high output and resistance to demagnetization.

  As a result of intensive studies to achieve the above object, the present inventor, as an IPM rotating machine using a plurality of rectangular parallelepiped permanent magnets, each permanent magnet has a permanent magnet having a high coercive force at the stator side corner. It was found that the use was effective. Furthermore, it has been found that it is effective to use a magnet having a high coercive force at a corner portion on the stator side of the magnet, particularly in a spoke type IPM rotating machine including a spoke type rotor. The spoke type rotor is a rectangular magnet in a plane perpendicular to the rotation axis of the rotor, its two parallel sides are parallel to the radial direction of the rotor, and the magnetization direction of the magnet is parallel to the circumferential direction of the rotor. That is, a rotor in which magnets are embedded so as to be perpendicular to the radial direction of the rotor. An example of a spoke type IPM rotating machine can be found in US Pat.

  The present invention is a rotor comprising a rotor core and a plurality of permanent magnets embedded in each of a plurality of insertion holes provided in the circumferential direction inside the rotor core, and disposed on the outer periphery of the rotor via a gap. A rotor having a stator core having a plurality of slots and a stator having a winding wound around the stator core, the rotor being used in a permanent magnet type rotating machine, wherein the permanent magnet is attached to a rotating shaft of the rotor A rectangular parallelepiped having two sides parallel to the radial direction of the rotor and two sides parallel to the circumferential direction on a vertical plane and having four sides parallel to the axial direction of the rotor. The magnetization direction is parallel to the circumferential direction of the rotor, the magnetization directions of the permanent magnets adjacent to each other in the circumferential direction are opposite to each other, the permanent magnet is an Nd-based rare earth sintered magnet, and the four sides 4 including each side of At least one corner of the portion has a coercive force higher than the inner center of the rectangular parallelepiped, and is disposed in the insertion hole so that the corner is on the stator side and behind the rotor in the rotation direction. A permanent magnet type rotating machine rotor is provided. Further, the present invention provides a permanent magnet comprising the rotor, and a stator that is disposed on the outer periphery of the rotor with a gap and includes a stator core having a plurality of slots and a winding wound around the stator core. A rotating machine is provided.

  According to the present invention, by using a permanent magnet having a high residual magnetic flux density and a high coercive force, particularly a high coercive force at a corner portion on the stator side, for a rotor of a spoke type IPM rotating machine, a high output and a high demagnetization. A spoke-type IPM permanent magnet rotating machine having resistance can be provided.

It is a figure which shows the example of the spoke type IPM rotating machine of this invention. It is a figure which shows the mode of the magnetic flux recirculation | reflux in the permanent magnet embedded inside the rotor core. It is a figure which shows intensity distribution of the demagnetizing field of the permanent magnet embedded inside the rotor core. It is a figure which shows the coercive force distribution state of the permanent magnet by which the diffusion process was carried out.

  In the rotor of the permanent magnet type rotating machine according to the present invention, a rotor in which a plurality of permanent magnets are embedded in a rotor core and a stator in which a winding is wound around a stator core having a plurality of slots are arranged via a gap. It is a rotor used for an IPM type permanent magnet type rotating machine. Preferably, the spoke is an IPM in which the magnet is rectangular in a plane perpendicular to the rotation axis of the rotor, two parallel sides are parallel to the radial direction of the rotor, and the magnetization direction of the magnet is parallel to the circumferential direction of the rotor. It is a rotor used for a rotating machine. In the present invention, the coercive force at the corner of the permanent magnet on the stator side is configured to be higher than the coercive force at the center of the magnet.

  An example of a spoke type IPM rotating machine is shown in FIG. A spoke type IPM rotating machine 1 shown in FIG. 1 includes a rotor (rotor) 10 and a stator (stator) 20 disposed on the outer periphery of the rotor 10 via a gap. The rotor 10 includes a rotor core 11 in which electromagnetic steel plates are laminated, for example. The rotor core 11 also functions as a yoke. The rotor core 11 is provided with a plurality of insertion holes in the circumferential direction. A permanent magnet 12 is accommodated in each insertion hole. Each insertion hole is preferably provided in substantially the same shape as the shape of the permanent magnet 12 to be accommodated. Each insertion hole is rectangular in a plane perpendicular to the rotation axis of the rotor 10, and the pair of parallel two sides is provided to be parallel to the radial direction of the rotor 10, and the other pair of parallel 2 The sides are provided so as to be parallel to the circumferential direction. Furthermore, the insertion hole has a depth in the axial direction of the rotor 10. The insertion hole may be a through hole. In FIG. 1, arrows in the permanent magnets 12 indicate the magnetization directions of the permanent magnets 12. The magnetization direction of the permanent magnet 12 is parallel to the circumferential direction of the rotor 10, and the magnetization directions of the magnets 12 adjacent in the circumferential direction are opposite to each other.

  The stator 20 includes a stator core 21 having slots 22, for example, laminated magnetic steel sheets. A winding (coil) 23 is wound around each tooth 21 a of the stator core 21. The coil 23 is, for example, a three-phase Y connection. FIG. 1 illustrates a stator 20 having a 12-slot structure, but the number of slots is not limited to this and can be selected according to the purpose of the rotating machine.

  FIG. 1 illustrates a rotor 10 having a 10-pole structure, but the number of poles is not limited to this, and can be selected according to the purpose of the rotating machine. The number of poles, that is, the number of insertion holes into which magnets are inserted is preferably an even number, and is preferably arranged at equal intervals in the circumferential direction.

  The outer peripheral shape of the rotor core 11 is preferably formed in a shape that is not a perfect circle in a plane perpendicular to the rotation axis. Preferably, the outer peripheral shape of the rotor core 11 in the plane perpendicular to the rotation axis has the same number of outwardly convex arch shapes (including arcs) as the permanent magnets 12, and the starting point of the arch shape and the center of the rotor core 11 are the same. The connecting straight line passes through the permanent magnet 12. Such an outer peripheral shape is effective when it is desired to reduce torque ripple and cogging torque.

The permanent magnet 12 is preferably an Nd-based rare earth sintered magnet. Rare-earth sintered magnets are remarkably superior in both residual magnetic flux density and coercivity compared to other magnets. Furthermore, the Nd-based rare earth sintered magnet is lower in cost and has a higher residual magnetic flux density than the Sm-based rare earth sintered magnet. Therefore, the Nd-based rare earth sintered magnet is an optimum magnet material for a high-performance rotating machine. Examples of the Nd-based rare earth sintered magnet include a sintered magnet having an Nd—Fe—B-based composition, such as Nd ₂ Fe ₁₄ B.

  The permanent magnet 12 is preferably a rectangular parallelepiped (including a cube). The permanent magnet 12 has a rectangular shape in the insertion hole having two sides parallel to the radial direction of the rotor 10 and two sides parallel to the circumferential direction in a plane perpendicular to the rotation axis of the rotor 10. It is accommodated so as to have four sides in the direction. The length of the two sides parallel to the radial direction of the rectangle is preferably 2 to 20 times the length of the two sides parallel to the circumferential direction. Thereby, the area | region of a rotor part can be utilized effectively. The height of the permanent magnet 12 may be approximately the same as the height (axial length) of the rotor 10.

  As the permanent magnet 12, one permanent magnet piece may be accommodated in each insertion hole of the rotor core 11. Alternatively, a plurality of divided permanent magnet pieces may be accommodated in each insertion hole of the rotor core 11 by using an adhesive or the like, and the plurality of divided permanent magnet pieces may be stored without using an adhesive or the like. May be stacked and accommodated.

  In the permanent magnet type rotating machine, the coil current is maximized when the maximum torque is generated, and the magnetic field generated by the coil is also maximized. In the IPM rotating machine, the magnetic flux generated from the coil of the stator passes through the gap between the stator and the rotor from the teeth around which the coil is wound, enters the rotor yoke, and then the direction of the magnetic flux in the circumferential direction inside the rotor yoke. Then, the air passes through the gap again, and returns to the tooth around which the coil in which a current flowing in the opposite direction flows next to the tooth is wound. At this time, the magnetic flux generated from the coil tries to pass through the yoke having a higher magnetic permeability than the magnet, so that the magnetic flux flows inside the rotor while avoiding the magnet insertion hole provided in the rotor. The magnetic flux is leaked into the insertion hole due to the magnetic saturation state in the portion where the magnetic flux path is narrow. In particular, since the magnet stator side region is close to the coil, the magnetic flux from the coil tends to leak into the magnet region. This magnetic flux becomes a demagnetizing field with respect to the magnet accommodated in the insertion hole, and the magnet is easily demagnetized.

  In the spoke type IPM rotating machine, the magnetization direction of the magnet is oriented in the circumferential direction, so that the magnetic flux generated from the magnet flows into the stator mainly through the gap between the stator and the rotor. However, as indicated by an annular arrow in FIG. 2, the magnetic flux generated from the magnet is recirculated near the plane parallel to the magnetization direction. If there is a large amount of returned magnetic flux, the magnetic flux flowing into the stator is reduced, leading to a reduction in torque. Therefore, it is preferable to reduce the amount of the returned magnetic flux by making the yoke 11a of the magnetic flux return portion as narrow as possible. However, the narrow yoke 11a is in a magnetic saturation state, and the magnetic flux tends to leak. As described above, the magnetic flux generated from the coil also flows into the magnetic flux return portion because it passes through the yoke 11a, but the magnetic flux leaks to the magnet portion because of the magnetic saturation state. The leaked magnetic flux acts as a demagnetizing field on the magnet, and the magnet is easily demagnetized. Therefore, magnetic saturation becomes remarkable especially in the magnetic flux return part close to the gap, and magnetic flux leakage increases, and the demagnetizing field becomes large in the magnet corner part on the stator side.

  FIG. 3 shows the intensity distribution of the demagnetizing field inside the permanent magnet at the maximum torque in the IPM rotating machine illustrated in FIG. In FIG. 3, as indicated by an arrow R, the rotor rotates counterclockwise. At this time, the demagnetizing field acting on the magnet is the largest at the stator side corner at the rear in the rotation direction (right side stator side corner in the magnet of FIG. 3). Also, since the demagnetizing field becomes large at the stator side corner at the rear of the rotation direction, when the rotor rotating direction is reversed, the portion where the demagnetizing field is large is also reversed (the left side of the magnet in FIG. 3). Become. Therefore, the permanent magnet has a high coercive force in at least one of the four corners including the four sides, and the corner is on the stator side, and the rotation direction of the rotor. It is embedded in the insertion hole so as to be rearward. Furthermore, it is preferable to use a magnet having a high coercive force at the other corner (forward in the rotational direction) located on the stator side. That is, preferably, a magnet having a high coercive force is used in at least two corners on the stator side among the four corners.

  As a method for obtaining a magnet having a high coercive force, Dy or Tb diffusion treatment by a coating method or a sputtering method is preferable. In addition, as a general method of obtaining a magnet having a high coercive force, there is a method using a magnet having a high coercive force as a whole. However, when the coercive force is increased, the residual magnetic flux density is lowered and the motor output is reduced. End up. On the other hand, in the Dy or Tb diffusion treatment method, the coercive force can be increased to a depth of about 6 mm from the magnet surface, while the residual magnetic flux density hardly decreases. Further, as will be described later, the effect of increasing the coercive force by the diffusion treatment is greatest at the corners of the magnet. Therefore, the technique of increasing the coercive force by performing the Dy or Tb diffusion process described above is very effective as a countermeasure against the demagnetization of the magnet of the spoke type IPM rotating machine. When the coercive force of the corners on the stator side of the magnet is increased in this way and the magnet is used, the rotating machine is operated at the rated power and a large demagnetizing field is generated at the stator side corners of the magnet. But it can prevent demagnetization. Furthermore, since the magnet by such a method has a higher residual magnetic flux density than a magnet whose coercive force has been increased by another method, the output of the rotating machine can be increased.

A method of diffusing Dy or Tb from the magnet surface to the inside by a coating method or a sputtering method is described in Patent Documents 1 and 2, and is also called a surface treatment by a grain boundary diffusion alloy method. This method preferably contains one or more elements selected from rare earth elements including Y and Sc, more preferably one or more elements selected from oxides, fluorides, and oxyfluorides of Dy or Tb. In a state where the powder is present on the surface of the sintered magnet body, the sintered magnet body and the powder are subjected to heat treatment in a vacuum or an inert gas at a temperature lower than the sintering temperature of the sintered magnet body. is there. The sintered magnet body is preferably a sintered magnet body having an R ¹ —Fe—B-based composition (R ¹ represents one or more selected from rare earth elements including Y and Sc).

  The particle diameter of the powder affects the reactivity when the Dy or Tb component of the powder is absorbed by the magnet, and the smaller the particle, the greater the contact area involved in the reaction. In order to achieve the effect of the present invention, the average particle size of the powder to be present is preferably 100 μm or less, more preferably 10 μm or less. The lower limit is not particularly limited, but is preferably 1 nm or more. The average particle diameter is preferably determined by a laser diffraction method.

  Due to the Dy or Tb diffusion treatment, Dy or Tb contained in the powder present on the magnet surface is absorbed by the magnet and concentrated near the interface of the crystal grains of the magnet body. Thereby, coercive force can be raised, suppressing the fall of a residual magnetic flux density.

Further, according to the Dy or Tb diffusion treatment, the concentration of Dy or Tb in the vicinity of the interface decreases from the magnet surface toward the inside. Therefore, it is considered that the coercive force increasing effect by the diffusion treatment is higher as it is closer to the magnet surface, and the coercive force increasing effect is gradually reduced as the depth from the magnet surface is increased.
In the portion where at least two orthogonal surfaces intersect and the magnet corner in the vicinity thereof, Dy or Tb is diffused from each surface, so that Dy or Tb is concentrated more than the center of the diffused surface. The effect of increasing the coercive force is increased. Therefore, as shown in FIG. 4, when the distance from the magnet corner A toward the magnet inner center A ′ not affected by the diffusion process is taken as the X axis and the coercive force is taken as the Y axis, the closer to the magnet corner, the more the coercive force. It can be seen that the increase effect is high.

  Therefore, for the magnet environment having the demagnetizing field intensity distribution shown in FIG. 3, the increase in coercive force by the diffusion process is particularly effective. The amount of increase in coercive force due to the diffusion treatment is about 500 to 800 kA / m near the center of the magnet surface and further increases at the corners of the magnet. Therefore, sufficient coercivity is provided for the magnet having the demagnetizing field strength distribution shown in FIG. It can be said that magnetic force rises.

  In the example shown in FIG. 3, the demagnetizing field has a higher value of 475 kA / m at the stator side corner (847 kA / m) than at the magnet inner center (372 kA / m). When the thickness of the magnet is about 10 mm or more, the effect of the diffusion treatment does not sufficiently reach the center of the magnet and it is difficult to expect an increase in the coercive force at the center of the magnet. Therefore, in order to prevent demagnetization, the magnet before the diffusion treatment needs to have a coercive force that can withstand the demagnetizing field at the center of the magnet, and the coercive force is 475 kA / m by the diffusion treatment at the corner of the magnet. As described above, it is preferable to increase by 500 kA / m or more, more preferably by 600 kA / m or more. On the other hand, when the thickness of the magnet is less than about 10 mm, the increase in the coercive force at the center of the magnet due to the diffusion treatment increases as the thickness decreases, and the difference in coercive force from the corners decreases. If the design is such that the increased coercive force at the center of the magnet after diffusion treatment can withstand the demagnetizing field at the center of the magnet, there is a risk that the magnet corners cannot withstand a large demagnetizing field. Therefore, it is preferable to use a magnet in which the coercive force of the magnet corner is increased by 600 kA / m or more by the diffusion treatment, regardless of the thickness of the magnet. Accordingly, even when a large demagnetizing field is generated at the stator side corner of the magnet, demagnetization can be prevented, and the output of the rotating machine can be increased because the residual magnetic flux density is high. The coercive force of the magnet before the diffusion treatment is preferably 800 to 2800 kA / m, more preferably 800 to 2000 kA / m, and still more preferably 800 to 1600 kA / m.

  From the above, as the magnet used in the spoke type IPM rotating machine, a magnet whose coercive force at the stator corner is preferably increased by 475 kA / m, more preferably 600 kA / m or more by the diffusion treatment is used.

The diffusion treatment of Dy or Tb may be performed on the entire surface of the permanent magnet, or may be performed partially on the surface of the permanent magnet. In the case of partial application, the coercive force only needs to increase at least one of the stator side corners including the side of the permanent magnet, and diffuses to at least the stator side corner including the side of the rectangular parallelepiped permanent magnet. What is necessary is just to make it process.
The width of the corner to be processed depends on the size of the rectangular cross section perpendicular to the rotation axis and whether it is installed at the rear or front of the rotation direction, but preferably left and right (circumferential direction and radial direction) from the side. Toward, it is 10 to 100% of the size of each magnet.

  When diffusion treatment is performed on the entire surface of a rectangular magnet, the coercive force increases at all corners, but this does not adversely affect the magnet or rotating machine, and the coercive force at the stator side corners increases. If so, it will not be a problem. Also, it has a length twice as large as its radial dimension with respect to the magnet incorporated in the rotor. For other dimensions, the same magnet is prepared, and after diffusion treatment is performed on the entire surface, the magnet is The magnet may be divided into two in the length direction that is doubled, and the magnet divided into two may be inserted into the rotor with the corners with increased coercivity facing the stator.

  When a plurality of permanent magnet pieces divided into the respective insertion holes are accommodated, diffusion processing may be performed on all the permanent magnet pieces, which corresponds to at least one of the two stator side corners including the side of the permanent magnet. The diffusion treatment may be performed on one or more permanent magnet pieces including the permanent magnet pieces. Further, the diffusion treatment may be performed before or after the permanent magnet pieces are laminated.

  When the circumferential side of the magnet is 2 mm or less, the magnet is thin, so that the effect of the diffusion treatment reaches to the inside of the magnet to some extent, the internal coercivity increases to some extent, and the difference in coercivity between the inside and the corner is Although it is smaller, this does not cause any adverse effects.

  In Patent Document 2, in the SPM rotating machine, when Dy or Tb diffusion treatment is performed on a thin portion of a D-shaped magnet that has a large self-demagnetizing field and is likely to be demagnetized, the inside is sufficiently retained because of its thinness. Since the magnetic force increases, it is reported that Dy or Tb diffusion treatment is an effective method for preventing demagnetization. On the other hand, in the case of a rectangular magnet used in an IPM rotating machine, the thickness of the magnet is constant and there is no significant difference in the magnitude of the self-demagnetizing field, so it has been considered that the diffusion treatment method is effective in preventing demagnetization. It was not done. However, according to the present invention, a demagnetizing field due to the stator coil must be taken into consideration for demagnetization, and even in an IPM rotating machine having a spoke-type rotor, the increase in coercive force due to the diffusion process prevents the demagnetization of the magnet. It has been found useful for this.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to examples, but the content of the present invention is not limited thereto.

<Example 1>
Nd ₂ Fe ₁₄ B of a rectangular parallelepiped Nd-based rare earth sintered magnet having a residual magnetic flux density of 1.32 T, a coercive force of 1000 kA / m, dimensions of length 12 mm × width 3 mm × height 50 mm, width 3 mm A magnet whose direction is the magnetization direction was used. A plurality of these magnets were prepared and subjected to diffusion treatment. As diffusion treatment, granular dysprosium fluoride with an average particle diameter of 5 μm is mixed with ethanol at a mass fraction of 50%, the magnet is immersed in this, and then heat treated at 900 ° C. for 1 hour in an Ar atmosphere. It was. A cube with a side of 1 mm was cut from one of the magnets from the corner of the magnet including the apex of the magnet, and the coercive force was measured using a BH tracer. As a result, the coercive force of the corner magnet was 1600 kA / m. Therefore, the coercive force increased by 600 kA / m.

  This magnet was incorporated into a rotating machine having 10 poles and 12 coils as shown in FIG. 1 and having a rotor diameter of 50 mm and a shaft length of 50 mm, and a motor output test was conducted. The magnets were arranged such that the magnetization direction was the circumferential direction, the magnetization directions of the magnets adjacent in the circumferential direction were opposite to each other, and the height of the magnet was the axial direction of the rotor. The rotor and stator were each made of a laminated structure of 0.35 mm thick electromagnetic steel sheets, and the coils were wired in a three-phase Y connection with concentrated winding.

  First, when the no-load electromotive force at a rotation speed of 1000 rpm was measured using a voltmeter, the line temperature was 114 V at a magnet temperature of 20 ° C. Next, when the operation was performed at a rated output of 800 W at a rotation speed of 1000 rpm, the coil current was 4.5 A. The magnet temperature at this time was 90 degreeC. Thereafter, in order to investigate the demagnetization state of the magnet, the no-load electromotive force at a rotation speed of 1000 rpm was measured again, and the magnet temperature was 20 ° C. and the line voltage was 114V. Therefore, the line voltage was the same before and after the rated operation. Therefore, it was confirmed that the magnet was not demagnetized. As described above, by increasing the coercive force at the stator corners of the magnet by 600 kA / m by the diffusion treatment, a rotating machine that does not cause demagnetization can be obtained.

<Comparative Example 1>
On the other hand, a plurality of magnets having the same magnetic characteristics as in Example 1 and having the same size and shape as in Example 1 and the same magnetization direction were prepared, and the same test as in Example 1 was performed without subjecting this magnet to diffusion treatment. . First, when the no-load electromotive force was measured at a rotational speed of 1000 rpm, the line voltage was 114 V as in Example 1. Next, when the operation was performed at a rotational speed of 1000 rpm and a coil current of 4.5 A, the magnet temperature was 90 ° C. and the output was 760 W. It is presumed that the output was lower than in Example 1 because the magnet was demagnetized. Thereafter, in order to examine the demagnetization state of the magnet, the no-load electromotive force at the rotation speed of 1000 rpm was measured again, and the magnet temperature was 20 ° C. and the line voltage was 108V. Therefore, the line voltage after the rated operation was reduced by about 5% from that before the rated operation. From this result, it was confirmed that the magnet was demagnetized.

  From the above, it was found that a magnet that did not improve the coercive force at the stator side corner part was demagnetized and the motor output decreased.

DESCRIPTION OF SYMBOLS 1 IPM rotating machine 10 Rotor 11 Rotor core 11a Yoke of magnetic flux return part 12 Permanent magnet 20 Stator 21 Stator core 21a Teeth 22 Slot 23 Coil

Claims (8)

A rotor provided with a rotor core and a plurality of permanent magnets embedded in each of a plurality of insertion holes provided in the circumferential direction inside the rotor core; and a plurality of slots arranged on the outer periphery of the rotor via gaps A stator having a stator core having a stator and a winding wound around the stator core, and a rotor for use in a permanent magnet rotating machine comprising:
The permanent magnet is a rectangle having two sides parallel to the radial direction of the rotor and two sides parallel to the circumferential direction on a plane perpendicular to the rotation axis of the rotor, and 4 parallel to the axial direction of the rotor. A rectangular parallelepiped having sides,
The magnetization directions of the permanent magnets are parallel to the circumferential direction of the rotor, and the magnetization directions of the permanent magnets adjacent in the circumferential direction are opposite to each other,
The permanent magnet is an Nd-based rare earth sintered magnet, and at least one of the four corners including each of the four sides has a coercive force higher than the inner center of the rectangular parallelepiped. The rotor for a permanent magnet type rotating machine is arranged in the insertion hole so that the corner is on the stator side and behind the rotor in the rotation direction.   2. The rotor for a permanent magnet type rotating machine according to claim 1, wherein another corner portion located on the stator side among the four corner portions also has the high coercive force.   The permanent magnet rotating machine according to claim 1 or 2, wherein the high coercive force is obtained by increasing the coercive force from the surface of the permanent magnet to a maximum depth of 6 mm by Dy or Tb diffusion treatment. Rotor.   The rotor for a permanent magnet type rotating machine according to claim 3, wherein the high coercive force is a coercive force that is 475 kA / m or more higher than the permanent magnet not subjected to the diffusion treatment.   The rotor for a permanent magnet type rotating machine according to claim 4, wherein the high coercive force is a coercive force that is 600 kA / m or more higher than that of the permanent magnet not subjected to the diffusion treatment.   The permanent magnet rotating machine according to any one of claims 1 to 5, wherein a length of two sides parallel to the radial direction of the rectangle is 2 to 20 times a length of two sides parallel to the circumferential direction. Rotor.   The shape of the outer periphery of the rotor core has the same number of outwardly convex arch shapes as permanent magnets, and a straight line connecting the starting point of the arch shape and the center of the rotor core is a shape passing through the permanent magnets. A rotor for a permanent magnet type rotating machine according to any one of the above. A rotor according to any one of claims 1 to 7;
A stator provided with a stator core having a plurality of slots and a winding wound around the stator core, arranged on the outer periphery of the rotor via a gap;
A permanent magnet type rotating machine.

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