JP7471580B1 - A rotor, a stator, an embedded magnet type synchronous machine including the rotor and the stator, and a manufacturing method of the rotor core and the stator core - Google Patents

Abstract

[Problem] To impart radial anisotropy to an induced transformation type magnet in a rotor core, and to make the rotor core and stator core out of materials of the same chemical composition. [Solution] The rotor of an embedded magnet type synchronous machine is made of a rotor core, a rare earth bonded magnet injection molded into its embedded portion, and polar anisotropically magnetized, and the rotor core is made of a laminate of rotor core parts made of magnets with induced transformation martensite structure, and is magnetized with radial anisotropic orientation. The stator core is made of a laminate of stator cores that have the same chemical composition as the rotor core and are heat-treated to have isotropic soft magnetic properties. [Selected Figure] Figure 1

Description

The present invention relates to an internal magnet type synchronous machine that is composed of a radially anisotropic rotor core made of magnets with an induced transformation martensite structure, and an isotropic stator core, the rotor core and the stator core having the same chemical composition, a rare earth bonded magnet formed in the internal portion of the rotor, and adjacent north and south poles magnetized with polar anisotropy.

There are various types of electric motors (including generators, simply called "motors"). Recently, with the development of inverter control and the widespread use of rare earth magnets with high magnetic properties, synchronous machines, which are energy-saving, highly efficient, and can provide high torque or high output, have been attracting attention.

A synchronous machine is a motor that has a permanent magnet for a field on the rotor and an armature winding (coil) on the stator, and is an AC motor that rotates by generating a rotating magnetic field in the stator by supplying polyphase alternating current (AC) to the armature winding. Synchronous machines are broadly classified into surface permanent magnet motors (SPM), in which permanent magnets are arranged on the surface of the rotor, and interior permanent magnet motors (IPM), in which permanent magnets are embedded inside the rotor. IPM, which has high output torque and is highly reliable because it prevents magnets from scattering, is currently becoming mainstream. In order to further increase the output of IPM motors, efforts are being made to increase the rotation speed.
Currently, neodymium sintered magnets are mainly used as permanent magnets, but as the rotation speed increases, the heat generation problem becomes more serious, and a change to rare earth bonded magnets is being considered.

Another problem with sintered Nd magnets is that conventional IPMs are constructed by inserting sintered magnets that have been cut and ground to a specified size and magnetized to saturation into slots (contained parts) in the rotor. However, when inserting a strong magnetized rare earth sintered magnet into a slot, the magnet is prone to damage.
Therefore, Patent Document 1 discloses replacing conventional sintered magnets with injection-molded rare earth bonded magnets in which molten strands made of rare earth magnets and resin are injected into rotor slots in a magnetic field and then cooled and solidified.
In view of the above, in order to increase the rotation speed and output of IPM motors, the adoption of injection molded rare earth bonded magnets, which are an alternative to sintered Nd magnets, is being considered.

Patent Document 6 discloses that in order to solve the above problems, an injection-molded rare earth bonded magnet can be used to achieve high speed rotation, while at the same time output can be increased by using an induced transformation type magnet in the rotor core and making the magnet ends nonmagnetic.
However, the problem of how to impart radial anisotropy to the induced transformation type magnet of the rotor core remains unsolved, and if conventional materials are used for the stator core, using different materials for the two core materials would result in a significant increase in cost.

Japanese Patent Application Laid-Open No. 11-206075 Japanese Patent No. 4626683 JP 2013-1433791 A Patent No. 6868174 Patent No. 7125684 Patent No. 7394427

However, Patent Document 1 merely proposes replacing the rare earth sintered magnets of IPM with rare earth bonded magnets, and makes no mention of the configuration of rotors or slots suitable for injection molding rare earth bonded magnets in a magnetic field.

Patent Document 2 proposes providing a non-magnetic portion in a portion of the rotor, which is an iron core. This reduces leakage flux and can increase the effective flux (flux linkage) that contributes to motor output. However, such non-magnetic portions are merely provided with an eye on the magnetic circuit formed between the rotor and stator when the motor is in operation, and are not related to the aligning magnetic field during injection molding of rare earth bonded magnets, as described below.

In Patent Document 3, the rare earth anisotropic magnet particles that make up rare earth bonded magnets, regardless of composition, have much higher magnetic flux density and coercive force than the commonly used ferrite magnet particles, and therefore require a higher aligning magnetic field for orientation during injection molding than ferrite magnet particles. Therefore, in order to efficiently produce high-performance IPMs, a method is disclosed in which the aligning magnetic field applied during injection molding of the rare earth anisotropic bonded magnet is effectively applied to the slots of the rotor core in which the bonded magnets are housed.
The non-magnetic parts are modified by laser welding, which transfers alloy elements, but the modified parts are very uneven and the shape changes, so the post-modification processing, such as surface grinding and shape correction, is complicated and not practical. In fact, this application was abandoned without a request for examination. Naturally, it is not used industrially.
However, rare earth bonded magnets are inferior in magnetic performance to sintered Nd magnets, and therefore tend to have lower motor torque, so measures to increase torque are desired.

Patent document 6 discloses that it is possible to increase the rotational speed by using an injection-molded rare earth bonded magnet, while at the same time increasing the output by using an induced transformation type magnet in the rotor core and making the magnet ends nonmagnetic.

That is, the inventors disclosed an invention of an induced transformation type magnet in 2019 (Patent Document 4). Furthermore, as shown in Patent Document 5, based on the experience of changing the plate components of a magnetic denture attachment from a magnetic material to an induced transformation type magnet, and the experience of increasing the adhesive force by 50%, and further noting that the resistivity of an induced transformation type magnet is 72 μΩcm, which is more than twice the 32 μΩcm of the 3% silicon steel plate used as the magnetic material of an IPM motor, the inventors considered changing the magnetic material of the rotor of the IPM motor to an induced transformation type magnet.
As a result of repeated trial and error, it was found that by changing the structure of Ni-based stainless steel from 100% austenite to one containing 80% or more martensite to create a semi-hard magnetic material, and by adopting an induced transformation type magnet with a saturation magnetization of 12,000 to 16,000 G, a coercive force of 80 to 300 Oe, a residual magnetization Br of 6,000 to 8,000 G, and a maximum energy product of 0.2 to 4 MGOe at room temperature as the magnetic performance after saturation magnetization, and further by modifying specific areas of the rotor core to make them nonmagnetic, it was possible to increase the motor torque by 30% or more compared to a rotor whose main body material has not been modified to be nonmagnetic with a magnetic material. Moreover, it was confirmed that by heating the nonmagnetic parts to 900°C or more using a laser or high-frequency heating method, the austenite phase is restored and the parts are modified to be nonmagnetic without changing the shape of the outer periphery.

However, the problem of how to impart radial anisotropy to the induced transformation type magnets in the rotor core remains unsolved, and if conventional materials are used for the stator core, using different materials for the two cores would result in a significant increase in costs. A solution to these problems was needed.

The present invention aims to solve the problems in Patent Document 6.

Based on the premise that rotor cores and stator cores require lamination of thin plate components, the inventors came up with the idea that for rotor cores requiring radial anisotropy, radial anisotropy can be ensured by laminating induced transformation type semi-hard magnetic plates (thin plates of semi-hard magnetic material) with uniaxial anisotropy at an angle. In other words, they discovered that in the case of six magnetic poles, six uniaxial anisotropic thin plate magnets can be assembled by rotating them 60 degrees to the left. They produced a rotor core with radial anisotropy and confirmed that compared to one with uniaxial anisotropy, the motor torque increased and the cogging torque was significantly reduced.

When the semi-hard magnetic material with the induced transformation structure is annealed to form a recrystallized ferrite structure, it becomes a soft magnetic material with the same chemical composition as the magnet. Focusing on this point, a rotor core and a stator core were made from an induced transformation type magnetic plate by pressing while maintaining the same axis, and the stator core parts were annealed to form a soft magnetic material, which was then laminated to produce the stator core. Compared to conventional silicon steel plates, the magnetic permeability is slightly inferior, but the resistivity is twice as high, and the overall effect was to obtain the same motor torque.

The method for manufacturing a laminated rotor core having radial anisotropy and a laminated stator core having isotropic soft magnetic properties comprises:
(1) A plate member of an Fe-based alloy having a non-magnetic austenitic structure is cold worked at a low temperature to induce 80% or more of a martensite structure to form a semi-hard magnetic plate member.
(2) Forming in the rolling direction, applying tension along the drawn fiber structure and heat treating it, strengthening the magnetic anisotropy and improving the magnetic properties;
(3) By pressing, the rotor core parts and the stator core parts are punched out from the plate member (the tension heat-treated plate member) on a common axis, thereby ensuring a high yield rate;
(4) The rotor core is formed into a cylindrical shape having radial anisotropy by laminating rotor core parts made of semi-hard magnetic plates having uniaxial anisotropy at angles so as to have radial anisotropy as a whole core;
(5) The stator core is formed by subjecting the stator core components to a recrystallization heat treatment to give them a ferrite structure with isotropic soft magnetic properties, and then laminating them to form a cylindrical shape.
It has been found that it is possible to manufacture rotor cores and stator cores.

(1) The rotor and stator core of an encapsulated magnet type synchronous machine have an even number of encapsulated portions consisting of magnets with induced martensite structure and gaps arranged axially symmetrically around the central axis of rotation, and are equipped with an even number of permanent magnets provided in the encapsulated portions.
The magnet end regions extending from the ends of the permanent magnets to the outer circumferential edge of the rotor body are made of nonmagnetic parts. Also, the magnet end outer circumferential region of the body, which is made up of the magnet end region extending from one end of one permanent magnet to the outer circumferential edge of the rotor body, the magnet end region extending from the other end of an adjacent permanent magnet to the outer circumferential edge of the rotor body, and a connecting region connecting the magnet ends, is made of nonmagnetic parts.
The permanent magnets consist of rare earth bonded magnets that are injection molded within an envelope that has an aligning magnetic field applied to it.
The stator core is made of a soft magnetic material having the same chemical composition as the magnets.

The rotor of the present invention is composed of a polar anisotropically oriented permanent magnet (rare earth bonded magnet) and an induced transformation type magnet section with radial anisotropy, both of which are integrated and polar anisotropically magnetized during injection molding, and are simultaneously combined with a stator core made of a soft magnetic material with the same chemical composition, contributing to the high performance of the encapsulated magnet type synchronous machine by increasing the torque and reducing the cogging torque. The reasons for this are thought to be as follows.

First, in the rotor of the present invention, as shown in Figure 4(b), there is a case where the non-magnetic part extends from the end of the permanent magnet stored in the internal portion to the outer peripheral end of the main body (referred to as the non-magnetic part of the magnet end region), and as shown in Figure 4(c), there is a case where the outer peripheral side region extending from the end of the permanent magnet stored in the internal portion to the outer peripheral end of the main body (rotor core) and extending from the end of another adjacent permanent magnet to the outer peripheral end of the main body is a non-magnetic part (referred to as the non-magnetic part of the magnet end outer peripheral side region).
When an aligning magnetic field is applied to an inner encapsulation portion with such a non-magnetic outer peripheral region during injection molding, the aligning magnetic field flows from the inner magnetic pole portion of the permanent magnet to the outer magnetic pole portion, and then flows from the outer magnetic pole portion of the adjacent permanent magnet to the inner magnetic pole portion.
However, if there were no nonmagnetic portion at the end of the magnet, a large leakage magnetic flux would flow directly from the inner magnetic pole to the outer magnetic pole of the permanent magnet, which would not contribute to the alignment of the rare earth anisotropic magnet powder, weakening the aligning magnetic field.
Conversely, if there is a non-magnetic portion at the end of the magnet, the leakage flux is drastically reduced and the aligning magnetic field is strengthened. Also, if there is a non-magnetic portion at the outer peripheral region of the end of the magnet, the large leakage flux that flows directly from the inner magnetic pole to the outer magnetic pole of the permanent magnet is further reduced, so the aligning magnetic field becomes even stronger.
Conversely, the aligning magnetic field applied externally to the rotor during injection molding becomes distributed at high density within the rotor's internal portion and in the induced transformation type magnet portion, greatly increasing the effective magnetic flux that contributes to the alignment of the rare earth anisotropic magnet powder. Therefore, the rare earth anisotropic bonded magnet of the present invention can be injection molded with an aligning magnetic field of 1 T or more acting on it.

The reason that cogging torque can be reduced is that the magnets in the rotor core and the magnets formed by injection molding in the internal portion are integrated and polar anisotropically magnetized, resulting in excellent axial symmetry. In addition, because the magnets in the rotor core have radial anisotropy, the magnetic force of the polar anisotropic magnetization is axially symmetric in all directions.

In addition, when an orientation magnetic field of 1T or more is applied, the rare earth bonded magnet is molded in a saturated magnetized state. The reason for the saturated magnetization is that the injection molding temperature is high at 200°C or more, so the coercive force of the magnetic powder of the rare earth magnet is reduced to about 0.5T. The saturated magnetized state is maintained even after injection molding is completed, so magnetization after injection molding (post-magnetization) may not be necessary. This is particularly effective in the case of rare earth anisotropic bonded magnets made of rare earth anisotropic magnet powder (such as Nd-Fe-B magnet powder), which is a difficult-to-align magnet powder that requires a magnetizing magnetic field of about 3T in the post-magnetization process.

At the same time, the laminated rotor core with radial anisotropy formed from induced transformation type magnet material is magnetized from its semi-hard magnetic properties to oriented saturation by the oriented magnetic field from the north pole to the south pole of the rare earth magnet, becoming a permanent magnet, and the magnetic flux emanating from the rotor's magnetic poles increases by about 10% by changing the rotor core material from a magnetic material to an induced transformation type magnet. This increases the motor torque by about 10%.

Furthermore, by demagnetizing the magnet end region that extends from the end (end face) of the permanent magnet, which is the different magnetic pole surface, to the outer circumferential edge of the rotor body (as shown in FIG. 4(b)), or by demagnetizing the magnet end outer circumferential edge region that consists of the magnet end region that extends from the end (end face) of the permanent magnet, which is the different magnetic pole surface, to the outer circumferential edge of the rotor body, another magnet end region that extends from the end (end face) of the other permanent magnet, which is the different magnetic pole surface, to the outer circumferential edge of the rotor body, and a connecting region that connects these two magnet end regions (as shown in FIG. 4(c)), the magnetic flux increases by about 30%. This increases the motor torque by about 30%.

Naturally, in this invention, the permanent magnets contained in the rotor are bonded magnets, which has many advantages over embedding sintered magnets. For example, it is possible to reduce the use of rare earth elements, which are scarce and expensive. Also, when using sintered magnets, precision grinding and magnetization are required, but injection molded magnets do not require such processing. In addition, no processing waste is generated, so rare and expensive rare earth elements are not wasted.

On the other hand, when using sintered magnets, adhesive is required to fix the sintered magnets in the encapsulation part (slot) when they are inserted into the encapsulation part, which results in a non-magnetic gap between the magnet and the magnetic material of the rotor, increasing the magnetic resistance and impairing the flow of magnetic flux. In addition, the permanent magnets must be magnetized to saturation before being installed in the encapsulation part, which can cause problems such as collisions between the permanent magnets and the magnetic material of the rotor, resulting in defects.
However, bonded magnets, which are integrally molded within the encapsulation portion, are naturally and firmly fixed within the slot, so they do not have the drawbacks of sintered magnets.

Furthermore, when a synchronous machine is in operation, large eddy currents can cause iron loss in the sintered magnets. As the rotation speed increases, the eddy current loss increases exponentially, causing the magnet to heat up and reduce its coercive force, eventually resulting in demagnetization due to the demagnetizing field from the electromagnet.
On the other hand, in bonded magnets, each magnetic particle is insulated by the binder resin, which is an insulator, so the iron loss caused by the eddy current is very small. Therefore, synchronous machines with rotors containing bonded magnets are efficient. In addition, since each magnetic particle in bonded magnets is covered with the binder resin, they have high oxidation resistance without the need for surface treatment.

<Enclosed magnet type synchronous machine>
(1) The present invention is an encapsulated magnet type synchronous machine having the rotor core and stator core described above. That is, the present invention may be an encapsulated magnet type synchronous machine including the rotor described above and a stator having coils evenly arranged around the rotor and a yoke that forms a magnetic circuit on the outer periphery of the coils. The yoke may include teeth inside the coils as appropriate.

Synchronous machines basically generate a rotational force (magnetic torque) based on the attractive and repulsive forces generated by the magnetic poles formed by the permanent magnets on the rotor and the rotating magnetic field formed around the rotor by the stator. However, unlike surface magnet type synchronous machines, embedded magnet type (contained magnet type) synchronous machines tend to have a difference between the inductance (Ld) generated at the magnetic poles and the inductance (Lq) generated between the magnetic poles, so reluctance torque based on the attractive force is often generated in the rotor. In particular, when Ld<Lq, the reluctance torque and magnetic torque are in the same direction, and the output torque can increase.

Therefore, it is preferable that the rotor of the present invention also has a salient pole between adjacent magnetic poles formed by the permanent magnets, which generates a reluctance torque acting in the same direction as the magnet torque generated by the magnetic poles, by adjusting the shape and arrangement of the permanent magnets (enclosed portion) in the rotor.
Since the output of a synchronous machine is proportional to the number of revolutions, it is desirable to increase the number of revolutions. In the case of sintered Nd magnets, the faster they rotate, the more heat they generate, making it difficult to increase the number of revolutions to 30,000 RPM or more. Therefore, the present invention, which uses rare earth injection molded bonded magnets, is more suitable for synchronous machines with a number of revolutions of 30,000 RPM or more.

<Manufacturing method of encapsulated magnet type synchronous machine>
Furthermore, the present invention can be understood not only as the above-mentioned encapsulated magnet type synchronous machine, but also as a manufacturing method for the rotor core and the fixed core.That is, the present invention is as follows: (1) a plate member of an Fe-based alloy having a non-magnetic austenite structure is cold-rolled at a low temperature to induce 80% or more of a martensite structure to form a semi-hard magnetic plate member; (2) the plate member is formed in the rolling direction, tension is applied along the stretched fiber structure, and heat treatment is performed to strengthen the magnetic anisotropy and improve the magnetic properties; (3) the rotor core parts and the stator core parts are punched out from the plate material subjected to the above-mentioned tension heat treatment with a common axis by press processing, and a high yield is ensured; (4) the rotor core is formed into a cylindrical shape having radial anisotropy by laminating the rotor core parts made of magnets having uniaxial anisotropy at an angle so that the entire core has radial anisotropy characteristics, and then the encapsulated part of the cylinder and the intermediate region or the outer peripheral region of the rotor surface are made into a non-magnetic part by laser heating;
(5) The method for producing the stator core is characterized in that the stator core components are subjected to a recrystallization heat treatment to form a ferrite structure with isotropic soft magnetic properties, and then stacked into a cylindrical shape to produce the stator core and the rotor core.

The cylindrical rotor core has an internal portion consisting of gaps arranged symmetrically around the central axis of rotation. The intermediate or outer peripheral area of the rotor core surface is heated from the end of the gap to form a non-magnetic portion, and then a molten mixture of rare earth anisotropic magnet powder dispersed in a molten binder resin is injected into the gap in an aligning magnetic field to form a rare earth anisotropic bonded magnet, which is then magnetized to saturation to form a rotor.
Here, the intermediate region can be defined as a magnet end region extending from an end of the permanent magnet to the outer circumferential edge of the rotor core, and the outer circumferential edge region can be defined as a magnet end outer circumferential edge region including a magnet end region extending from one end of the permanent magnet to the outer circumferential edge of the rotor core, a magnet end region extending from the other end of another permanent magnet adjacent to the permanent magnet to the outer circumferential edge of the rotor core, and a connecting region connecting the magnet end regions.

The stator is made by attaching a field coil to the stator core. By combining this with the rotor, an internal magnet type synchronous machine can be manufactured.

The present invention improves the axial anisotropy of the magnetized state in an IPM motor with a rotation speed of 30,000 RPM or more, increasing motor torque by 30% or more and reducing cogging torque.

1 is a cross-sectional view of a main portion of a synchronous motor according to the present invention; FIG. 2 is a plan cross-sectional view of a semi-hard magnetic material, an inner portion, and a non-magnetic portion that constitute a cylindrical rotor prebody. FIG. 2 is a plan view of an induced transformation type magnet, a permanent magnet, and a non-magnetic portion that constitute a cylindrical rotor. 1A is a partial view of a rotor preform, showing (a) a punched material with an inner encapsulation portion formed therein, (b) a non-magnetic portion only in the magnet end region, and (c) a plan view showing the non-magnetic portion in the outer peripheral region of the magnet end. FIG. 4 is a flow diagram of a manufacturing process for a rotor core and a stator core. 1A to 1C are diagrams showing a method for simultaneously punching out a rotor core and a stator core from a semi-hard magnetic plate. FIG. 2 is a plan view of a rotor core part produced by punching. FIG. 4 is a plan view of a stator core part produced by punching. 1A to 1C are diagrams showing a lamination method for a rotor core having radial anisotropy. FIG. 2 is a perspective view showing a laminated state of a rotor core.

The rotor core of the encapsulated magnet type synchronous machine of the present invention consists of an induced transformation type magnet with uniaxial anisotropy, has a central axis of rotation, and has an even number of encapsulated parts consisting of gaps arranged axially symmetrically around the rotation axis.Depending on the number of encapsulated parts (hereinafter, an example is given of six encapsulated parts), the magnet plate having uniaxial anisotropy is rotated about six times at 30 degrees as shown in Figure 9, and stacked as shown in Figure 10 to have radial anisotropy.
The rotor body comprises an even number of permanent magnets provided in the internal encapsulation portion of a laminated type rotor core, and the magnet end region extending from the end of the permanent magnet to the outer peripheral end of the rotor body is made of a non-magnetic portion, and the permanent magnet is made of a rare earth anisotropic bonded magnet that is injection molded within the internal encapsulation portion to which an aligning magnetic field is applied, and is oriented along the aligning magnetic field while simultaneously being saturated magnetized.

In addition, the non-magnetic part of the rotor core of the encapsulated magnet type synchronous machine is
The magnet end outer circumferential region, which consists of a magnet end region extending from one end of the permanent magnet to the outer circumferential edge of the rotor body, a magnet end region extending from the other end of another permanent magnet adjacent to the permanent magnet to the outer circumferential edge of the rotor body, and a connecting region connecting the magnet end regions, is made of a non-magnetic part.
A detailed explanation will be given below with reference to FIG. 1 to FIG.

<Rotor of encapsulated magnet type synchronous machine>
(1) Main body (rotor)
The rotor body 11 is made of an induced transformation type magnet 10, and although the material is not critical, it is preferable to use an Fe-based alloy material such as Cr-Ni stainless steel or Mn-based non-magnetic steel, which is a semi-hard magnetic material that is in a non-magnetic austenite phase at room temperature and becomes a magnetic martensite phase after cold working. The shape is usually a laminate of thin plates with insulating coating on both sides.
This makes it possible to easily form non-magnetic portions by partial modification through local heating.

(2) The encapsulation sections 12, 121-126 of the encapsulation section rotor 11 are provided in the main body 11 and consist of gaps for disposing permanent magnets. The encapsulation sections 12, 121-126 contain permanent magnets that serve as magnetic poles, so there are at least two of them, and they are usually arranged symmetrically around the central axis of rotation of the main body.

The shape of the inner packet part is a convex shape that is convex on the inner circumference so that a strong aligning magnetic field can be applied uniformly throughout the entire inner packet part, and is formed into a smooth curved shape.
The shape of the inner encapsulation part is adjusted appropriately according to the specifications of the synchronous machine. For example, in the case where the number of magnetic poles is six, the inner encapsulation part 12, 121-126 may be a radial inner encapsulation part (12, 121-126) that extends linearly from the center in the radial direction. It is also preferable that the inner encapsulation part has a uniform groove width. Conversely, it is preferable that there is no sudden change in shape or size that would cause the applied orientation magnetic field to concentrate locally.

Furthermore, the inner encapsulation portion may be a multi-layered inner encapsulation portion with multiple layers in the radial direction. A multi-layered inner encapsulation portion can increase the reluctance torque. The number of layers in the multi-layered inner encapsulation portion is not important, but two or three layers are preferred in terms of achieving both the characteristics and productivity of the synchronous machine.

In the present invention, the permanent magnet is made of an injection-molded rare earth bonded magnet (hereinafter referred to as a bonded magnet), so regardless of the shape of the contained part, the permanent magnet will basically conform to the shape of the contained part. However, since it is possible to injection-mold the contained part with a spacer or the like interposed therebetween, the shape of the contained part and the shape of the permanent magnet may not match. There are two types of bonded magnets: isotropic and anisotropic, and it is preferable to use the anisotropic type.
This eliminates the magnetic field distribution and variation in the rotor and localized heat generation, enabling the rotor to rotate at high speeds and increasing the output of the IPM motor.

(3) Non-magnetic Parts The non-magnetic parts 14 are parts with a magnetic permeability of 1.2 or less. The non-magnetic parts 14, 141 to 146 are formed by modifying the semi-hard magnetic material of the induced transformation type magnet 10 that constitutes the rotor body 11, partially before it is magnetized to saturation.
This makes it possible to improve the efficiency of the magnetic circuit, and it is expected that motor torque will increase by 30%.

The semi-hard magnetic material can be modified by restoring the semi-hard magnetic material, which is made of a ferromagnetic martensite structure, to a non-magnetic austenite structure. Such modification can be stably performed by localized heating at 900°C or higher, irradiation with a laser or electron beam, high-frequency induction heating, etc.

The formation of the non-magnetic portion will be explained with reference to FIG. 4, which is a partial view of six magnetic poles.
(a) A rotor pre-body (pre-main body) 110 is produced by punching out a thin plate of a semi-hard magnetic material 111 having an inner portion formed therein. The outer periphery of the rotor pre-body (pre-main body) is defined as an outer periphery end 111e.
Each of the inner packet part 121 and the adjacent inner packet part 122 has two end faces (end parts), one end face being 121a and the other end faces being 121b and 122a, 122b.
The region extending from the end 121a of the inner packet part 121 to the outer circumferential end 111e is referred to as the magnet end region 121am. Similarly, the region extending from the end of the inner packet part to the outer circumferential end is referred to as the magnet end region below.

(b) Non-magnetic portions of magnet end regions The magnet end regions 121a, 121b, 122a, 122b made of a semi-hard magnetic material are locally heated to change the martensite structure to an austenite structure, thereby forming non-magnetic portions 141a, 141b, 142a, 142b.
The non-magnetic portions are formed at two locations by this modification, at both ends of each inner capsule.

(c) Since one end 121a of the non-magnetic portion contained in the inner portion 121 in the magnet end outer peripheral region and the other end 122b of the inner portion 122 are adjacent to each other, the three regions consisting of the magnet end region 121am of the inner portion 121, the adjacent magnet end region 122b (symbol omitted in the figure) of the inner portion 122, and the connecting region connecting the two magnet end regions are modified by a single local heating as the magnet end outer peripheral region to form the non-magnetic portion 141.
This method makes it possible to form one non-magnetic portion in one inner packet, thereby reducing the number of times local heating is performed by half.

The non-magnetic portion 14 according to the present invention is formed by heating and modifying the martensite structure in the outer peripheral region between adjacent permanent magnets (bonded magnets) so that a high aligning magnetic field is uniformly induced in the portion (encapsulated portions 121-126) where the bonded magnets are injection molded, to form a non-magnetic portion.
This allows the flow of the aligning magnetic field applied from the outside of the body to be greatly reduced in the leakage magnetic flux that flows directly from the inner magnetic pole to the outer magnetic pole via a specific portion of the outer peripheral region of the end, thereby strengthening the aligning magnetic field that contributes to the alignment. The non-magnetic portion in Fig. 4(c) is preferable to that in Fig. 4(b) because it can reduce the leakage magnetic flux even more.

The non-magnetic parts mentioned above are made of Cr-Ni stainless steel and have excellent mechanical properties. As they are merely modified by localized heating, the precision of the rotor body at the time of manufacture is maintained, making them ideal for high-speed rotation of the rotor.

<Rare earth anisotropic bonded magnet>
(1) The raw rare earth anisotropic bonded magnet basically consists of rare earth anisotropic magnet powder and binder resin. The rare earth anisotropic magnet powder is not particularly limited in type, and examples include Nd-Fe-B magnet powder, Sm-Fe-N magnet powder, Sm-Co magnet powder, etc. These rare earth anisotropic magnet powders may consist of one type or multiple types.

The binder resin may be any known material containing rubber. For example, it is preferable to use thermoplastic resins such as polyethylene, polypropylene, polyamide, liquid crystal polymer, and polyamide-imide. Thermosetting resins such as epoxy resin, mesh resin, melamine resin, and polyurethane may also be used as appropriate.

(2) Injection Molding The rare earth anisotropic bonded magnet according to the present invention is molded by heating and melting pellets or the like made of the above-mentioned raw materials, injecting the molten mixture into an encapsulating part to which an aligning magnetic field is applied, and then cooling and solidifying the mixture. The conditions for injection molding are appropriately adjusted taking into consideration the characteristics of the raw materials, the filling amount, the cooling properties of the encapsulating part, etc. For example, the heating temperature during injection molding (the temperature of the molten mixture) is preferably lower than the Curie point of the rare earth anisotropic magnet powder.

The aligning magnetic field must be applied before the molten mixture solidifies, but it may be applied from the beginning of the injection molding or halfway through the injection molding. For example, if a permanent magnet is used as the aligning magnetic field source, it may be applied from the beginning of the injection molding, and if an electromagnet is used, it may be applied halfway through the injection molding. The application form of the aligning magnetic field (distribution of magnetic flux density formed within the rotor) is adjusted appropriately according to the shape of the encapsulation portion and ultimately the specifications of the synchronous machine.

<Stator>
The stator core is made by pressing and punching the above-mentioned induced transformation type magnet material together with the rotor core to produce a thin plate stator core component. It is then annealed at 600°C to 850°C to form a ferrite recrystallized structure, which changes the semi-hard magnetic properties to soft magnetic properties. This is then laminated to produce the stator core. The field coil is attached to a designated location on the stator to complete the stator production.

The above rotor and stator are combined to produce an internal magnet type synchronous machine.

<Enclosed magnet type synchronous machine and its applications>
The present invention is suitable for application to an internal magnet type synchronous machine (IPM motor) having a rotation speed of 30,000 RPM. Its applications include vehicle drive motors used in electric automobiles, hybrid vehicles, and railroad cars, and motors for home appliances used in air conditioners, refrigerators, washing machines, etc. However, it is not limited to the above applications.

The method for manufacturing the rotor core and the stator core of the present invention will be described in detail with reference to the flow chart of FIG.
In the following description, six inner packet parts will be used as an example of an even number of inner packet parts.
<Step 201>
The base material is an Fe-based alloy material having a non-magnetic austenitic structure, and is made of Cr-Ni-based stainless steel, Mn-based non-magnetic steel, etc. The base material is made of a steel plate having a thickness of about 1 mm.

<Step 202>
This is a process for producing a 0.2 to 0.5 mm thick thin plate member (semi-hard magnetic plate member) made of semi-hard magnetic material by inducing 80% or more of martensite structure from a plate member of an Fe-based alloy with an austenitic structure by cold rolling. In this process, a uniaxial fibrous structure is formed from an elongated martensite structure formed in the rolling direction. This allows the rotor core parts to be magnetized to saturation to produce magnets.
In addition, in Figs. 6 to 9, the rolling direction of the uniaxial fibrous structure is indicated by a chain line (- - - -).

<Step 203>
This is a process in which a heat treatment is performed in which tension is applied along the fibrous structure formed in the rolling direction and stretched.
The tension heat treatment is performed at 400 to 600° C. under a tension of 20 to 80 kg/mm ^2. This strengthens the magnetic anisotropy and improves the magnetic properties.

<Step 204>
This is a press process in which the rotor core parts and the stator core parts are punched out around a common axis.
This will be explained with reference to FIG.
The tension heat-treated semi-hard magnetic plate member 300 (the rolling direction is indicated by the horizontal chain line 301) is pressed, and before the rotor core part 310 is punched out, the unnecessary inner part 312, the central hole (for shaft) 313, and the slot part 323 are punched out once or twice to form voids. After the rotor core part 310 is punched out, the stator core part 320 is punched out.

<Step 205>
FIG. 7 shows a rotor core part 310 produced by pressing.
The rotor core part 310 is made of a thin disk 311, an inner portion 312 in which a rare earth bonded magnet is injection molded, and a central hole 313 for inserting a shaft is punched out to form a gap.

<Step 206>
This is a process for manufacturing a rotor core by radially laminating rotor core components 310.
This will be explained with reference to FIG. 9 and FIG.
This is the process of manufacturing rotor core components made of semi-hard magnetic plates (thin circular plates) with uniaxial anisotropy into a cylindrical shape with radial anisotropy by stacking them at an angle so that the entire core has radial anisotropy characteristics.
The inner encapsulation portion 312 has six axes, and as shown in Figure 9, the first row is parallel to the rolling direction, the second row is rotated 30 degrees clockwise from the rolling direction, and the third row is rotated another 30 degrees for a total of 60 degrees, and the fourth to sixth rows are rotated 30 degrees each, 90 degrees, 120 degrees, and 150 degrees, respectively, to form radial anisotropic properties.
FIG. 10 is a perspective view of a cylindrically laminated rotor core 400 .
This gives radial characteristics to the induced transformation type magnet, enabling high speed rotation.

<Step 207>
FIG. 8 shows a stator core part 320 produced by pressing.
The stator core part 320 is made of a thin plate ring 321 and has teeth 322 around which a field coil is wound, and slots 323 are punched out to form voids.

<Step 208>
This is a heat treatment process in which the stator core parts are subjected to a recrystallization heat treatment at 600° C. to 850° C., preferably 500° C. to 700° C., to give them a ferrite structure with isotropic soft magnetic properties.
This allows the material to function as a stator, and is comparable to the electromagnetic steel sheets used in conventional embedded magnet type synchronous machines.

<Step 209>
This is a process in which stator core parts having isotropic soft magnetic properties due to a heat treatment process are laminated and formed into a cylindrical shape to produce a stator core.

From the above-mentioned manufacturing method of the rotor core and the stator core,
1) It is possible to impart radial anisotropy to the induced transformation type magnet of the rotor core,
2) The stator core can be made of materials with the same chemical composition as the rotor core, which allows for significant cost reductions.

An embodiment of an internal magnet type synchronous machine of the present invention will be described with reference to FIGS. 1 to 10, in which 18Cr-8Ni stainless steel having a nonmagnetic austenitic structure is used as a base material.
FIG. 1 shows a cross-sectional view of a main portion of a synchronous motor SM, FIG. 2 shows a plan view of the semi-hard magnetic material, encapsulated portion and non-magnetic portion that constitute the rotor preform, FIG. 3 shows a plan view of the induced transformation type magnets, permanent magnets and non-magnetic portion that constitute the rotor, and FIG. 4 is a partial view of the rotor preform of FIG. 3, showing (a) the punched material that forms the encapsulated portion, (b) the non-magnetic portion in the magnet end region, and (c) the non-magnetic portion in the outer circumferential region of the magnet end.
Figure 5 shows a flow chart of the manufacturing process for the rotor core and stator core, Figure 6 shows a method of simultaneously punching a rotor core and a stator core from a semi-hard magnetic plate, Figure 7 shows a plan view of a rotor core component made by punching, Figure 8 shows a plan view of a stator core component made by punching, Figure 9 shows a method of laminating a rotor core having radial anisotropy, and Figure 10 is an oblique view showing the laminated state of the rotor core.
The synchronous motor SM shown in FIG. 1 is a 6-pole, 18-throttle type.
The stator S and the rotor 1 will be described in detail below.

(1) Stator As shown in FIG. 1, the stator S is made of laminated steel plates of 18Cr-8Ni stainless steel ferritic structure, and comprises an annular yoke Sa, teeth Sb protruding evenly from the yoke Sa toward the center, and slots Sc formed between adjacent teeth Sb.
Each slot Sc houses an electromagnetic coil (not shown) that is wound around the teeth Sb in a distributed manner. When an inverter-controlled three-phase AC current is supplied to each electromagnetic coil, a rotating magnetic field is generated in the stator S at a synchronous speed according to the frequency and number of poles.

(2) Rotor Core Component The rotor core component 110, as shown in FIG. 2, is composed of a disk-shaped semi-hard magnetic material 111 having a central hole 151 and six internal portions 121-126 arranged evenly and axially symmetrically around the center thereof, each of which is made of an equal-width long groove that penetrates the inner periphery with a curved shape (convex shape) toward the inner circumference, and is rotated by an angle corresponding to the number of internal portions and stacked (FIGS. 9 and 10).
By stacking this semi-hard magnetic material 111, a rotor core 110 having radial anisotropy is formed, and the internal encapsulation portions 121 to 126 consisting of long grooves become penetrating internal encapsulation portions extending in the same direction in which the permanent magnet M is injection molded, and the central hole 151 becomes a shaft hole 151 extending in the direction in which the shaft (not shown) of the synchronous motor SM is inserted.

The ends of the inner container are modified parts 141-146 (non-magnetic parts) in which the outer circumferential end of the spare body 110, made of a semi-hard magnetic material, has been modified to a non-magnetic austenitic structure. This modification process was carried out by localized heating, using a laser to heat the outer circumferential region of the spare body 110, which is the part to be treated, to 900°C or higher.

(2) Rotor: Within the encapsulation portion 12 (121-126) having the modified portions 141-146 on the outer periphery at both ends, permanent magnets M made of rare earth anisotropic bonded magnets were formed by injection molding in a magnetic field.
Specifically, first, the spare body 110 is set in a magnetic field injection filling device (not shown), and an aligning magnetic field, the polarity of which alternates between adjacent packet parts 12 , is applied toward the packet parts 12 .
Furthermore, at the same time as forming the permanent magnets M (121M to 126M), a preliminary body made of a semi-hard non-magnetic material was magnetized to saturation to form an induced transformation type 18Cr-8Ni stainless steel magnet. In this way, the rotor body 11 was produced.

That is, a molten mixture obtained by heating and melting pellets made of Nd-Fe-B anisotropic magnet powder, Sm-Fe-N magnet powder, and polyphenylene sulfide resin (binder resin) is injected and filled into the internal portion 12. The molten mixture in the internal portion 12 is then solidified by cooling in the mold of the magnetic field injection filling device, and a permanent magnet M is formed that is integrally molded within the internal portion 12. In this way, a rotor 1 was obtained that contains permanent magnets M curved on the inner circumference in an evenly distributed ring shape.

In this embodiment, an aligning magnetic field was applied to the slot 12 from the start of filling the molten mixture to the end of filling. At this time, the aligning magnetic field was 0.7 T, the temperature of the molten mixture was 300°C, the injection pressure was 80 MPa, and the injection speed was 80 mm/sec.

As a result, the magnetic particles in the permanent magnet M are not only oriented during injection molding in a magnetic field, but are also magnetized at the same time, so that the permanent magnet M already has a high magnetic flux density. For this reason, in this embodiment, there was no need to perform post-magnetization.

The stator core was press-punched out from the above-mentioned induced transformation type magnet material plate at the same time as the rotor core. This improved the material yield of the stator core and rotor core material. It was then annealed at 650°C for 30 minutes to create a ferrite recrystallized structure with soft magnetic properties. The pieces were then laminated to create the stator core. A field coil was attached to the designated position of the stator core to create the stator. The stator and rotor were combined to create an internal magnet type synchronous machine.

(3) A shaft (not shown) is fitted into the shaft hole 19 of the rotor 1 containing the motor permanent magnet M. This rotor 1 is rotatably disposed within the stator S. At this time, the gap formed between the outer peripheral end face of the rotor 1 and the inner end faces of the teeth Sb is made constant. This synchronous motor SM is obtained. When this synchronous motor SM is connected to an inverter-controlled power supply and a rotating magnetic field is generated in the stator S, the rotor 1 rotates in synchronization with it.

In the synchronous motor SM, the inductance Lq1 in the q-axis direction, which is shifted by π/2 (electrical angle) from the d-axis direction, is greater than the inductance Ld1 in the d-axis direction that passes through the center of the permanent magnet M. Therefore, in the synchronous motor SM1, not only is the magnet torque Tm1 due to the permanent magnet M1 generated, but also the reluctance torque Tr1 based on the inductance difference (Lq1-Ld1) is generated in the same direction as the magnet torque Tm1. Therefore, the synchronous motor SM1 exerts a greater output. Also, the cogging torque has been reduced. Note that the definitions of the d-axis and q-axis are the same in the following examples.

It can be widely used as a vehicle drive motor for electric vehicles, hybrid vehicles, or railroad cars, as a motor for home appliances such as air conditioners, refrigerators, or washing machines, and as a drive motor for various robotic devices.

SM: Synchronous motor (contained magnet type synchronous machine)
1: rotor 10: induced transformation type magnet (plate), 12: encapsulated part, 14: non-magnetic part, 15: shaft M: permanent magnet (rare earth anisotropic bonded magnet)
d: Axial direction passing through the center of the permanent magnet M, q: Axial direction shifted by π/2 (electrical angle) from the d-axis direction, 2: Stator, Sa: Annular yoke, Sb: Teeth, Sc: Slot

110: Spare rotor body (spare main body)
111: semi-hard magnetic material, 121 to 126: inner part, 141 to 146: non-magnetic part,
151: Shaft hole

11: Rotor (main body)
10: Induced transformation type magnet (induced transformation type magnet part)
110: Outer periphery of main body 121M to 126M: Permanent magnet 121Ma: One end of permanent magnet 122Mb: Other end of permanent magnet 141 to 146: Non-magnetic portion 151: Shaft hole

30: Semi-hard magnetic material formed by punching the inner part 111: Semi-hard magnetic material (spare body)
111e: Outer periphery of spare body 121-122: Inner containment part 121a: One end of inner containment part 121 121am: Magnet end region of inner containment part 121 121b: Other end of inner containment part 121 122a: One end of inner containment part 122 122b: Other end 30A of inner containment part 122: Non-magnetic part of magnet end region 121-122: Inner containment part 141a: Non-magnetic part obtained by modifying magnet end region 121am 141b: Non-magnetic part obtained by modifying magnet end region 121bm (no reference number in the figure) 142a: Non-magnetic part obtained by modifying magnet end region 122am (no reference number in the figure) 142b: Non-magnetic part 30B obtained by modifying magnet end region 122bm (no reference number in the figure): Non-magnetic part of the outer periphery of the magnet end region 121-122: Inner containment part 141: magnet end region outer periphery region (121am, 122bm and the connecting region between them)
Non-magnetic portion 142: Non-magnetic portion in the outer peripheral region of the end region of the magnet; Non-magnetic portion 146: Non-magnetic portion in the outer peripheral region of the end region of the magnet

300: Simultaneous punching of rotor core and stator core 301: Tension heat-treated semi-hard magnetic plate member 302: Rolling direction (chain line)
310: Rotor core part 311: Thin plate disc 312: Encapsulated part 313: Central hole 320: Stator core part 321: Thin plate ring 322: Teeth 323: Slot 400: Rotor core (radially laminated in a cylindrical shape)

Claims (5)

The rotor of an internal magnet type synchronous machine consists of a rotor core and a permanent magnet.
The rotor core is made of a laminate of rotor core parts made of magnets with induced transformation martensite structures having uniaxial anisotropy , and has an even number of encapsulation portions each consisting of voids arranged axially symmetrically around a central axis of rotation,
And the magnet plate having uniaxial anisotropy is rotated and stacked according to the number of the inner encapsulation parts to have radial anisotropy;
The permanent magnets are arranged in an even number in the inner container, and are made of rare earth anisotropic bonded magnets that are injection molded in the inner container to which an aligning magnetic field is applied;
A rotor, characterized in that a magnet end region extending from an end of the permanent magnet to an outer peripheral end of the rotor core is a non-magnetic portion.
In claim 1,
A rotor characterized in that a magnet end outer circumferential region consisting of a magnet end region extending from one end of the permanent magnet to the outer circumferential edge of the rotor core, a magnet end region extending from the other end of another permanent magnet adjacent to the permanent magnet to the outer circumferential edge of the rotor core, and a connecting region connecting the magnet end regions, is made of a non-magnetic part. In the stator of an internal magnet type synchronous machine,
The stator core of the stator has the same chemical composition as the rotor core of claim 1;
A stator comprising a laminate of heat treated stator core components. An internal magnet type synchronous machine comprising a rotor according to claim 1 or 2 and a stator. A method for manufacturing a rotor core and a stator core of a stator that constitute an internal magnet type synchronous machine, comprising:
(1) A plate member of an Fe-based alloy having a non-magnetic austenitic structure is cold-rolled at a low temperature to induce 80% or more of a martensite structure to form a semi-hard magnetic plate member;
(2) applying tension along the fiber structure formed and stretched in the rolling direction and carrying out a heat treatment;
(3) A rotor core part and a stator core part are punched out of a plate member by a press working, with a common axis;
(4) The rotor core is formed into a cylindrical shape having radial anisotropy by laminating rotor core parts made of magnets having uniaxial anisotropy at an angle so that the core as a whole has radial anisotropy characteristics;
(5) The stator core is formed by laminating the stator core components into a cylindrical shape after subjecting them to a recrystallization heat treatment to give them a ferrite structure with isotropic soft magnetic properties.
A manufacturing method comprising the steps of: manufacturing a rotor core and a stator core.

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