Rotor, stator, magnet-inclusion type synchronous machine consisting of rotor and stator, and manufacturing method of rotor core and stator core

Abstract

To give radial anisotropy to an induced transformation type magnet of a rotor core and to manufacture the rotor core and a stator core from materials of the same chemical composition.SOLUTION: A rotor 1 of a magnet-inclusion type synchronous machine consists of: a rotor core; a rare earth bond magnet 10 injection-molded in its included part; and polar anisotropic magnetization, wherein the rotor core consists of laminate of rotor core components consisting of magnets of induced transformation martensite structure, and is oriented and magnetized in radial anisotropy. The stator core consists of laminate of stator cores having heat-treated isotropic soft magnetic characteristics and having the same chemical composition as that of the rotor core.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an encapsulated magnet type synchronous machine comprising a rotor core having a radial anisotropy composed of an induced metamorphic martensite structure magnet and an isotropic stator core, the rotor core and the stator core having the same chemical composition, a rare earth bonded magnet being formed in an encapsulated portion provided in the rotor, and adjacent N poles and S poles being magnetized with pole anisotropy.

Background Art

[0002] There are various types of electric motors (simply referred to as "motors" including generators). Recently, with the development of inverter control and the spread of rare earth magnets with high magnetic properties, synchronous machines that can achieve power saving, high efficiency, high torque, or high output have attracted attention.

[0003] A synchronous machine is a motor having a permanent magnet for field excitation on a rotor and armature windings (coils) on a stator, and is an AC motor in which a rotating magnetic field is generated in the stator by supplying polyphase alternating current (AC) to the armature windings and rotates. Synchronous machines are roughly classified into a surface magnet type motor (SPM) in which a permanent magnet is disposed on the surface of the rotor and an embedded magnet type motor (IPM) in which a permanent magnet is embedded inside the rotor. Among them, the IPM, which has a large output torque, can prevent the magnet from flying off, and has high reliability, is becoming the current mainstream. Furthermore, in order to increase the output of the IPM motor, the rotational speed is being increased. Currently, Nd sintered magnets are mainly used as permanent magnets. However, with the increase in rotational speed, the heat generation problem has become serious, and a change to rare earth bonded magnets is being considered.

[0004] Furthermore, as a problem of Nd sintered magnets, conventional IPMs were configured by inserting a sintered magnet that had been cut, polished, etc. to a predetermined dimension and saturated magnetized into a slot (encapsulated portion) provided in the rotor. However, when inserting a strongly magnetized rare earth sintered magnet into the slot, the magnet is likely to be damaged. Therefore, Patent Document 1 discloses replacing a conventional sintered magnet with an injection-molded rare-earth bonded magnet composed of a rare-earth magnet and a resin by injecting and filling a molten strand composed of the rare-earth magnet and the resin into the slots of a rotor in a magnetic field and then cooling and solidifying it. From the above circumstances, in order to increase the rotational speed and output of an IPM motor, the adoption of an injection-molded rare-earth bonded magnet with an altered Nd sintered magnet is under consideration.

[0005] 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, and at the same time, the output can be increased by making the magnet at the end of the rotor core non-magnetic with an induced transformation type magnet. However, the problem of how to impart radial anisotropy to the induced transformation type magnet in the rotor core remains unsolved. Also, when using conventional materials for the stator core, if different materials are used as the two core materials, a significant cost increase will occur. The solution to these problems has been sought.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, Patent Document 1 merely proposes replacing the rare-earth sintered magnet of the IPM with a rare-earth bonded magnet, and does not touch on the configuration of the rotor and slots suitable for injection molding in a magnetic field of the rare-earth bonded magnet at all.

[0008] In Patent Document 2, it has been conventionally proposed to provide a non-magnetic portion in a part of the rotor that is the iron core. Thereby, leakage magnetic flux can be reduced, and the effective magnetic flux (linked magnetic flux) contributing to the motor output can increase. However, such a non-magnetic portion is merely arranged paying attention to the magnetic circuit formed between the rotor and the stator during motor operation, and has nothing to do with the orientation magnetic field during injection molding of the rare-earth bonded magnet as described later.

[0009] In Patent Document 3, the rare-earth anisotropic magnet particles constituting the rare-earth bonded magnet generally have a much higher coercive force as well as magnetic flux density compared with the ferrite magnet particles commonly used regardless of the composition. Therefore, a higher orientation magnetic field is required for orientation during injection molding than that of ferrite magnet particles. Accordingly, in order to efficiently produce a high-performance IPM, a method of effectively applying the orientation magnetic field applied during injection molding of the rare-earth anisotropic bonded magnet to the slots of the rotor core in which the bonded magnet is accommodated is disclosed. The modification of the non-magnetic portion is performed by laser welding or the like that transfers alloy elements. However, since the modified portion has severe irregularities and its shape also changes, the post-treatment such as surface grinding and shape correction processing is complicated and cannot be said to be practical. Actually, this application has been abandoned without being examined and claimed. Naturally, it is not used industrially. However, since the rare-earth bonded magnet is inferior in terms of magnet performance compared with the Nd sintered magnet, it tends to decrease in terms of motor torque, and countermeasures for torque increase are expected.

[0010] In Patent Document 6, it is disclosed that by using an injection molding type rare-earth bonded magnet, aiming at high-speed rotation, and simultaneously making the magnet end non-magnetic with an induced transformation type magnet in the rotor core, the output can be increased.

[0011] That is, the inventors disclosed the invention of an induced transformation type magnet in 2019 (Patent Document 4). Furthermore, as shown in Patent Document 5, based on the experience that when the plate part of a magnetic denture attachment was changed from a magnetic material to an induced transformation type magnet, the adsorption force increased by as much as 50%, and also paying attention to the fact that the specific resistance of the induced transformation type magnet is more than twice that of the 3% silicon steel sheet, which is 32 μΩcm and is used as the magnetic material of an IPM motor, they considered changing the magnetic material of the rotor of the IPM motor to an induced transformation type magnet. As a result of repeated trials, the structure of Ni-based stainless steel was changed from a 100% austenite structure to a structure having 80% or more martensite structure to form a semi-hard magnetic material. And the magnetic properties of the magnet after saturation magnetization are, at room temperature, an induced transformation type magnet having a saturation magnetization of 12,000 to 16,000 G, a coercive force of 80 to 300 Oe, a residual magnetism Br of 6,000 to 8,000 G, and a maximum energy product of 0.2 to 4 MGOe. Furthermore, by making a specific area of the rotor core non-magnetic by modification, it was found that the motor torque can be increased by 30% or more compared to a rotor whose main body material is a magnetic material and has not been non-magnetically modified. Moreover, it was confirmed that the non-magnetic part can be restored to the austenite phase and non-magnetically modified without changing the shape of the outer peripheral part by heating it to 900 °C or higher by a heating method using a laser or high frequency.

[0012] However, the problem of how to impart radial anisotropy to the induced transformation type magnet of the rotor core remains unsolved. Also, when using the conventional material for the stator core, if the two core materials are of different types, a significant cost increase will occur. The solution to these problems has been demanded.

[0013] The object of the present invention is to solve the problems in Patent Document 6.

Means for Solving the Problems

[0014] Based on the premise that the rotor core and stator core need to be laminated with thin plate components, the inventors found that for a rotor core that requires radial anisotropy, when laminating an induced transformation type semi-hard magnetic plate (thin plate of semi-hard magnetic material) with uniaxial anisotropy, radial anisotropy can be ensured by laminating at an angle. That is, when the number of magnetic poles is 6, it was found that 6 uniaxial anisotropic thin plate magnets can be assembled by rotating and folding them 60 degrees each. When a rotor core with radial anisotropy was manufactured and compared with one having uniaxial anisotropy, it was confirmed that the motor torque increased and the cogging torque decreased significantly.

[0015] The semi-hard magnetic material having the above induced transformation structure becomes a soft magnetic material having the same chemical composition as the magnet when it is made into a recrystallized ferrite structure by annealing heat treatment. Focusing on this point, the rotor core and stator core were manufactured by pressing from an induced transformation type magnetic plate while maintaining coaxiality. The stator core parts were subjected to annealing heat treatment to make them into a soft magnetic material, and then laminated to manufacture the stator core. Compared with the conventional one made of silicon steel sheet, it has the characteristic that the magnetic permeability is slightly inferior, but the specific resistance is excellent at twice that, and the same motor torque can be obtained by the comprehensive effect.

[0016] A method for manufacturing a laminated rotor core having radial anisotropy and a laminated stator core having isotropic soft magnetic characteristics is as follows: (1) A plate member of an Fe-based alloy having a non-magnetic austenite structure is cold-worked at a low temperature to induce a martensite structure of 80% or more to obtain a semi-hard magnetic plate member. (2) Formed in the rolling direction, heat treatment is performed by applying tension along the elongated fiber structure to strengthen the magnetic anisotropy and improve the magnet characteristics. (3) By pressing, the rotor core parts and stator core parts are punched out from the above plate member (tension heat-treated plate member) with a common axis to ensure a high yield. (4) The rotor core is formed by laminating rotor core parts made of a semi-hard magnetic plate having uniaxial anisotropy at an angle so as to have radial anisotropy characteristics as a whole core to form a cylindrical shape having radial anisotropy. (5) The stator core is formed by stacking anisotropic soft magnetic ferrite structures obtained by recrystallization heat treatment of stator core components into a cylindrical shape. It has been found that the rotor core and the stator core can be manufactured.

[0017] (1) Rotor and stator cores of an interior permanent magnet synchronous machine The rotor has an even number of inclusion parts composed of magnets with an induced transformed martensite structure and voids axially symmetrically arranged around the rotation center axis, and is provided with an even number of permanent magnets provided in the inclusion parts. The magnet end region from the end of the permanent magnet to the outer peripheral end of the rotor body is made of a non-magnetic part. Also, the magnet end outer peripheral side region of the body, which consists of the magnet end region from one end of one permanent magnet to the outer peripheral end of the rotor body, the magnet end region from the other end of the adjacent permanent magnet to the outer peripheral end of the rotor body, and the connection region connecting the magnet ends, is made of a non-magnetic part. The permanent magnet is made of a rare earth bonded magnet injection molded within the inclusion part where an orientation magnetic field is applied. The stator core is made of a soft magnetic material having the same chemical composition as the magnet.

[0018] The rotor of the present invention is composed of a permanently magnet (rare earth bonded magnet) with pole anisotropy and a magnet part of an induced transformation type having radial anisotropy. The two are integrated and magnetized with pole anisotropy during injection molding, and at the same time, it is combined with a stator core made of a soft magnetic material having the same chemical composition, contributing to high performance such as high torque and reduced cogging torque of the interior permanent magnet synchronous machine. The reason is considered as follows.

[0019] First, in the rotor of the present invention, as shown in FIG. 4(b), when the part from the end of the permanent magnet housed in the inclusion part to the outer peripheral end of the body is a non-magnetic part (referred to as the non-magnetic part of the magnet end region), and as shown in FIG. 4(c), when the part extending from the end of the permanent magnet housed in the inclusion part to the outer peripheral end of the body (rotor core), the part extending from the end of the other adjacent permanent magnet to the outer peripheral end of the body, and the outer peripheral side region connecting the outer peripheral ends of both are non-magnetic parts (referred to as the non-magnetic part of the magnet end outer peripheral side region). When an orientation magnetic field is applied during injection molding into an encapsulated portion with such a non-magnetic outer peripheral region, the orientation magnetic field flows from the inner magnetic pole portion of the permanent magnet to the outer magnetic pole portion, and then continues to flow from the outer magnetic pole portion of the adjacent permanent magnet to the inner magnetic pole portion. However, if there is no non-magnetic portion at the magnet end at this time, there will be a large leakage magnetic flux that directly flows from the inner magnetic pole to the outer magnetic pole of the permanent magnet and does not contribute to the orientation of the rare earth anisotropic magnet powder, resulting in a weakening of the orientation magnetic field. Conversely, if there is a non-magnetic portion at the magnet end, the leakage magnetic flux will sharply decrease, and the orientation magnetic field will be strengthened. Also, if there is a non-magnetic portion in the outer peripheral region at the magnet end, the large leakage magnetic flux that directly flows from the inner magnetic pole to the outer magnetic pole of the permanent magnet will be further reduced, so the orientation magnetic field will become stronger. Conversely, the orientation magnetic field applied to the rotor from the outside during injection molding becomes densely distributed inside the encapsulated portion of the rotor and in the magnet portion of the induced transformation type, and the effective magnetic flux contributing to the orientation of the rare earth anisotropic magnet powder increases significantly. Therefore, the rare earth anisotropic bonded magnet according to the present invention can be injection molded in a state where an orientation magnetic field of 1 T or more acts.

[0020] The reason why the cogging torque can be reduced is that the magnet of the rotor core and the magnet formed by injection molding in the encapsulated portion are integrated and subjected to pole anisotropic magnetization and excellent axisymmetric magnetization. Also, because the magnet of the rotor core has radial anisotropy, the magnetic force of pole anisotropic magnetization is axisymmetric in any direction.

[0021] Also, in the case of an applied orientation magnetic field of 1 T or more, the rare earth bonded magnet is molded in a state of being saturated magnetized. The reason for the saturated magnetization is that the injection molding temperature is as high as 200 °C or more, so the coercive force of the magnetic powder of the rare earth magnet becomes as small as about 0.5 T. Since the state of saturated magnetization is maintained even after the injection molding is completed, post-magnetization (post-magnetization) after injection molding may not be required. This is particularly effective in the case of a rare earth anisotropic bonded magnet made of rare earth anisotropic magnet powder (for example, Nd-Fe-B based magnet powder, etc.), which is a difficult-to-orient magnet powder that requires a magnetization field of about 3 T in the post-magnetization process.

[0022] At the same time, a laminated rotor core having radial anisotropy formed from an induced metamorphic type magnet material is also magnetized to saturation orientation from semi-hard magnetic properties by an orientation magnetic field directed from the N pole to the S pole of the rare earth magnet to become a permanent magnet. The magnetic flux emitted from the magnetic poles of the rotor increases by about 10% by changing the core material of the rotor from a magnetic material to an induced metamorphic type magnet. As a result, the motor torque increases by about 10%.

[0023] Furthermore, by demagnetizing (shown in Fig. 4(b)) the magnet end region extending from the position of the end (end face), which is a different magnetic pole face of the permanent magnet, to the outer peripheral end of the rotor body, or by making non-magnetic (shown in Fig. 4(c)) the magnet end outer peripheral side region consisting of the magnet end region extending from the position of the end (end face), which is a different magnetic pole face of the permanent magnet, to the outer peripheral end of the rotor body and the other magnet end region extending from the position of the end (end face), which is a different magnetic pole face of the other permanent magnet, to the outer peripheral end of the rotor body and the connecting region connecting these two magnet end regions, the magnetic flux increases by about 30%. As a result, the motor torque increases by about 30%.

[0024] Of course, in the present invention, since the permanent magnet enclosed in the rotor is a bonded magnet, it has many advantages compared to the case of embedding a sintered magnet. For example, the use of rare and expensive rare earths can be suppressed. Also, when using a sintered magnet, precision grinding and magnetization are required, but in the case of an injection molded magnet, such processing is not necessary. In addition, no processing waste is generated, so rare and expensive rare earths are not wasted.

[0025] On the other hand, when using a sintered magnet, an adhesive for fixing inside the enclosure is required when inserting the sintered magnet into the enclosure (slot). As a result, a non-magnetic gap is generated between the magnet and the magnetic material of the rotor, increasing the magnetic resistance and impairing the flow of magnetic flux. Also, it is necessary to magnetize the permanent magnet to saturation and install it inside the enclosure, so troubles such as collisions between the permanent magnet and the magnetic material of the rotor resulting in defects may occur. However, in the case of a bonded magnet integrally formed inside the enclosure, it will naturally be firmly and closely fixed inside the slot, so there are no drawbacks such as those of sintered magnets.

[0026] Also, during the operation of the synchronous machine, iron loss due to large eddy currents can occur in the sintered magnet. As the rotational speed increases, the eddy current loss increases quadratically, and accordingly, the magnet heats up, the coercive force decreases, and finally, demagnetization occurs due to the demagnetizing field from the electromagnet. On the other hand, since each magnet particle of the bonded magnet is insulated by a binder resin which is an insulator, the iron loss due to the generated eddy currents is very small. Therefore, a synchronous machine comprising a rotor incorporating the bonded magnet is efficient. Also, since each magnet particle of the bonded magnet is coated with a binder resin, it has high oxidation resistance without the need for surface treatment or the like.

[0027] <Embedded Magnet Type Synchronous Machine> (1) The present invention is an embedded magnet type synchronous machine having the rotor core and the stator core described above. That is, the present invention may be an embedded magnet type synchronous machine including the rotor described above, a stator having a coil evenly disposed around the outer periphery of the rotor, and a yoke that constitutes a magnetic circuit on the outer peripheral side of the coil. Incidentally, the yoke may appropriately include teeth in the coil.

[0028] Basically, a synchronous machine generates a rotational force (magnet torque) based on the attractive force and repulsive force generated by the magnetic poles formed by the permanent magnets provided on the rotor and the rotating magnetic field formed around the outer periphery of the rotor by the stator. However, in the case of an embedded magnet type (embedded magnet type) synchronous machine different from the surface magnet type synchronous machine, since the difference between the inductance (Ld) generated in the magnetic poles and the inductance (Lq) generated between the magnetic poles is likely to occur, the reluctance torque based on the attractive force often occurs in the rotor. Particularly when Ld < Lq, the reluctance torque and the magnet torque are in the same direction, and the output torque can increase.

[0029] Therefore, it is preferable that the rotor according to the present invention also has salient poles that adjust the shape, arrangement, etc. of the permanent magnets (embedded portions) in the rotor, and generate a reluctance torque acting in the same direction as the magnet torque generated by the magnetic poles, for example, between adjacent magnetic poles formed by the permanent magnets. Since the output of the synchronous machine is proportional to the rotational speed, it is desirable to increase the rotational speed. In the case of Nd sintered magnets, the heat generation increases as the rotational speed increases, and it is difficult to increase the rotational speed to 30,000 RPM or more. Therefore, the present invention using rare earth injection molded bonded magnets is more suitable for synchronous machines having a rotational speed of 30,000 RPM or more.

[0030] <Manufacturing method of an interior magnet type synchronous machine> Furthermore, the present invention can be understood not only as the above-described interior magnet type synchronous machine but also as a manufacturing method for its rotor core and stator core. That is, the present invention includes: (1) A plate member of an Fe-based alloy having a non-magnetic austenite structure is cold-rolled at a low temperature to induce a martensite structure of 80% or more to form a semi-hard magnetic plate member. (2) Tension is applied along the formed and stretched fiber structure in the rolling direction and heat treatment is performed to strengthen the magnetic anisotropy and improve the magnet characteristics. (3) By press working, the rotor core part and the stator core part are punched out from the above-mentioned tension heat-treated plate material with a common axis to ensure a high yield. (4) The rotor core is formed by laminating rotor core members made of magnets having uniaxial anisotropy at an angle so as to have a radial anisotropy characteristic as a whole core, and then the inner region or the outer peripheral region between the inner part of the cylinder and the rotor surface is made into a non-magnetic part by laser heating. (5) The stator core is characterized in that the stator core part is made into an isotropic soft magnetic ferrite structure by recrystallization heat treatment and then laminated into a cylindrical shape to manufacture the stator core and the rotor core.

[0031] The cylindrical rotor core has an inner part composed of voids arranged axially symmetrically around the rotation center axis. After heating the intermediate region or the outer peripheral region of the rotor core surface from the end of the void to form a non-magnetic part, a molten mixture in which rare earth anisotropic magnet powder is dispersed in a molten binder resin is injection-filled in the void part in an orientation magnetic field to mold a rare earth anisotropic bonded magnet and at the same time, saturated magnetization is performed to form the rotor. Here, the intermediate region can be defined as the magnet end region extending from the end of the permanent magnet to the outer peripheral end of the rotor core. Also, the outer peripheral side region can be defined as the magnet end region extending from one end of the permanent magnet to the outer peripheral end of the rotor core, the magnet end region extending from the other end of another permanent magnet adjacent to the permanent magnet to the outer peripheral end of the rotor core, and the magnet end outer peripheral side region consisting of the connecting region connecting the magnet end regions.

[0032] Attach a field coil to the stator core to form a stator. An interior permanent magnet type synchronous machine can be manufactured in combination with the above rotor.

Advantages of the Invention

[0033] According to the present invention, in an IPM motor having a rotation speed of 30,000 RPM or more, the axial anisotropy in the magnetized state is improved, the motor torque is increased by 30% or more, and cogging torque can be reduced.

Brief Description of the Drawings

[0034]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Best Mode for Carrying Out the Invention

[0035] The rotor core of the interior permanent magnet synchronous machine of the present invention is composed of an induced transformation type magnet having uniaxial anisotropy, has a rotation center axis, and has an even number of interior portions composed of gaps axially symmetrically arranged around the rotation axis. The number of interior portions (hereinafter, an example of six interior portions is used.) According to the number of interior portions, a magnet plate having uniaxial anisotropy is rotated about six times at 30 degrees as shown in FIG. 9, and laminated as shown in FIG. 10 to have radial anisotropy. The rotor body includes an even number of permanent magnets provided in the interior portions of the laminated type rotor core. The magnet end region from the end of the permanent magnet to the outer peripheral end of the rotor body is composed of a non-magnetic portion. The permanent magnet is injection molded within the interior portion to which an orientation magnetic field is applied, and is composed of a rare earth anisotropic bonded magnet that is oriented along the orientation magnetic field and is simultaneously saturated magnetized.

[0036] Also, the non-magnetic portion of the rotor core of the interior permanent magnet synchronous machine is The magnet end outer peripheral side region composed of the magnet end region from one end of the permanent magnet to the outer peripheral end of the rotor body, the magnet end region from the other end of the other permanent magnet adjacent to the permanent magnet to the outer peripheral end of the rotor body, and the connection region connecting the magnet end regions is composed of a non-magnetic portion. Hereinafter, it will be described in detail with reference to FIGS. 1 to 4.

[0037] <Rotor of Interior Permanent Magnet Synchronous Machine> (1) Main body (rotor) The rotor body 11 is made of an induced transformation type magnet 10, and the material thereof is not limited, but an Fe-based alloy material such as Cr-Ni series stainless steel or Mn-based non-magnetic steel, which is a semi-hard magnetic material with a non-magnetic austenite phase at room temperature and a magnetic martensite phase after cold working, is preferable. The shape usually consists of a laminate of thin plates with both sides insulated and coated. Thereby, a non-magnetic portion can be easily formed by partial modification by local heating.

[0038] (2) Encapsulation part The encapsulation parts 12, 121 to 126 of the rotor 11 are provided in the above-mentioned body 11 and consist of voids for arranging permanent magnets. Since the encapsulation parts 12, 121 to 126 encapsulate permanent magnets serving as magnetic poles, there are at least two or more of them, and usually, these are symmetrically arranged around the rotation center axis of the body.

[0039] The shape of the encapsulation part is a convex encapsulation part with a convex shape on the inner peripheral side so that a high orientation magnetic field can act uniformly on the entire encapsulation part, and it has a smooth curve shape. Note that the shape of the encapsulation part is appropriately adjusted according to the specifications of the synchronous machine and the like. For example, when the number of magnetic poles is 6 poles, the encapsulation parts 12, 121 to 126 may be radial encapsulation parts (12, 121 to 126) extending linearly in the radial direction from the center. Also, it is preferable that the encapsulation part has a uniform groove width. Conversely, the less sudden shape changes and dimensional changes that are likely to cause local concentration of the applied orientation magnetic field, the better.

[0040] Furthermore, the encapsulation part may be a multi-layer type encapsulation part with a plurality in the radial direction. When a multi-layer type encapsulation part is used, an increase in reluctance torque can be achieved. The number of layers of the multi-layer type encapsulation part is not limited, but 2 layers or 3 layers are preferable for achieving both the characteristics and productivity of the synchronous machine.

[0041] In the present invention, since the rare earth bonded magnet (hereinafter referred to as the bonded magnet) in which the permanent magnet is injection-molded, the permanent magnet will basically follow the shape of the inner part regardless of the shape of the inner part. However, since it is also possible to perform injection molding with a spacer or the like interposed in the inner part, the shape of the inner part and the shape of the permanent magnet may not match. There are two types of bonded magnets: an isotropic type and an anisotropic type, and it is preferable to adopt the anisotropic type. This eliminates the magnetic field distribution, variation, and local heat generation of the rotor, enables high-speed rotation of the rotor, and makes it possible to increase the output of the IPM motor.

[0042] (3) Non-magnetic part The non-magnetic parts 14 are locations where the magnetic permeability is 1.2 or less. The non-magnetic parts 14, 141 to 146 are constituted by modified parts obtained by partially modifying the semi-hard magnetic material before saturation magnetization of the induction transformation type magnet 10 constituting the rotor main body 11. This makes it possible to improve the efficiency of the magnetic circuit, and it is expected that the motor torque will be improved by 30%.

[0043] Here, the modification of the semi-hard magnetic material can be performed by restoring the semi-hard magnetic material composed of a martensite structure having ferromagnetism to a non-magnetic austenite structure. Such modification can be stably performed by local heating at 900 °C or higher, irradiation with a laser, an electron beam, or the like, or high-frequency induction heating.

[0044] The formation of the non-magnetic part will be described with reference to a partial view having six magnetic pole numbers in FIG. 4. (a) Punched material with an inner part formed A rotor preform (preliminary main body) 110 is produced by punching from a thin plate of the semi-hard magnetic material 111. Its outer periphery is the outer peripheral end 111e. The inner parts 121 and the adjacent 122 each have two end faces (ends), and one end face is 121a, the other end face is 121b, and the other end faces are 122a and 122b. A region extending from the end portion 121a of the inner inclusion portion 121 to the outer peripheral end 111e is defined as a magnet end region 121am. Hereinafter, similarly, a region extending from the end portion of the inner inclusion portion to the outer peripheral end is defined as a magnet end region.

[0045] (b) Non-magnetic portion of the magnet end region The magnet end regions 121a, 121b, 122a, and 122b made of a semi-hard magnetic material are locally heated to be modified from a martensite structure to an austenite structure to form non-magnetic portions 141a, 141b, 142a, and 142b. Since the non-magnetic portions formed by this modification are formed at both ends for each inner inclusion portion, two non-magnetic portions are formed.

[0046] (c) Non-magnetic portion of the magnet end outer peripheral side region Since one end portion 121a of the inner inclusion portion 121 and the other end portion 122b of the inner inclusion portion 122 are adjacent to each other, three regions including the magnet end region 121am of the inner inclusion portion 121, the magnet end region 122b of the adjacent inner inclusion portion 122 (omitted in the figure), and the connection region connecting the magnet end regions of both are defined as the magnet end outer peripheral side region and modified by one-time local heating to form a non-magnetic portion 141. In this method, it is possible to form one non-magnetic portion in one inner inclusion portion, and the number of times of local heating can be reduced by half.

[0047] By the way, the non-magnetic portion 14 according to the present invention is formed by heating and modifying the martensite structure in the outer peripheral side region between adjacent permanent magnets (bond magnets) so that a high orientation magnetic field is uniformly induced to the portion (inner inclusion portions 121 to 126) where the bond magnet is injection molded to form a non-magnetic portion. Thereby, in the flow of the orientation magnetic field applied from the outside of the main body, the leakage magnetic flux directly flowing from the inner magnetic pole side to the outer magnetic pole side through a specific portion of the outer peripheral side region at the end portion can be significantly reduced, and the orientation magnetic field contributing to the orientation can be strengthened. The non-magnetic portion is preferable because it can reduce the leakage magnetic flux more in FIG. 4(c) than in FIG. 4(b).

[0048] The above non-magnetic part is made of Cr-Ni series stainless steel or the like, has excellent mechanical properties, and since it has only been modified by local heating, the accuracy during the production of the rotor body is maintained as it is, making it suitable for high-speed rotation of the rotor.

[0049] <Rare earth anisotropic bonded magnet> (1) Raw materials The rare earth anisotropic bonded magnet basically consists of rare earth anisotropic magnet powder and a binder resin. The type etc. of the rare earth anisotropic magnet powder are not particularly limited, and for example, there are Nd-Fe-B based magnet powder, Sm-Fe-N based magnet powder, Sm-Co based magnet powder, etc. These rare earth anisotropic magnet powders may consist of not only one kind but also a plurality of kinds.

[0050] As the binder resin, a known material containing rubber can be used. For example, it is preferable to use a thermoplastic resin such as polyethylene, polypropylene, polyamide, liquid crystal polymer, polyamideimide, etc. Also, a thermosetting resin such as an epoxy resin, reticulated resin, melamine resin, polyurethane, etc. can be appropriately used.

[0051] (2) Injection molding The rare earth anisotropic bonded magnet according to the present invention is formed by injecting a molten mixture obtained by heating and melting pellets etc. composed of the above raw materials into an inner part to which an orientation magnetic field is applied, and then cooling and solidifying. Each condition of the injection molding is appropriately adjusted in consideration of the characteristics of the raw materials, the filling amount, the cooling property of the inner part, etc. For example, the heating temperature (temperature of the molten mixture) during injection molding is preferably below the Curie point of the rare earth anisotropic magnet powder.

[0052] Also, the orientation magnetic field needs to be applied before the molten mixture solidifies, and its start may be from the beginning of the injection molding or from the middle of the injection molding. For example, when using a permanent magnet as the orientation magnetic field source, it may be from the beginning of the injection molding, and when using an electromagnet, it may be from the middle of the injection molding. The application form of the orientation magnetic field (distribution of the magnetic flux density formed in the rotor) is appropriately adjusted according to the shape of the inner part and thus the specifications of the synchronous machine.

[0053] <Stator> The stator core is press-punched from the above-mentioned induced transformation type magnetic material simultaneously with the rotor core to produce a single thin plate stator core component. Then, annealing heat treatment is performed at 600°C to 850°C to modify the semi-hard magnetic properties to soft magnetic properties as a ferrite recrystallized structure. These are laminated to form a stator core. A field coil is attached to a predetermined part of the stator to manufacture the stator.

[0054] The above rotor and stator are combined to manufacture an interior permanent magnet synchronous machine.

[0055] <Interior Permanent Magnet Synchronous Machine and Its Applications> The present invention is suitable for application to an interior permanent magnet synchronous machine (IPM motor) having a rotational speed of 30,000 RPM. Its applications are suitable for vehicle drive motors used in electric vehicles, hybrid vehicles, or railway vehicles, etc., and home appliance motors used in air conditioners, refrigerators, washing machines, etc. However, it is not limited to the above applications.

[0056] The manufacturing method of the rotor core and stator core of the present invention will be described in detail with reference to the flowchart of FIG. 5. Note that, as an example of an even number of interior parts, six interior parts will be described. <Step 201> The base material is an Fe-based alloy material having a non-magnetic austenite structure, and is made of Cr-Ni-based stainless steel, Mn-based non-magnetic steel, etc. It is made of a steel plate with a thickness of about 1 mm.

[0057] <Step 202> This is a step of producing a thin plate member (semi-hard magnetic plate member) with a thickness of 0.2 to 0.5 mm made of a semi-hard magnetic material by inducing more than 80% martensite structure from a plate member of an Fe-based alloy with an austenite structure by cold rolling. In this step, a uniaxial fibrous structure composed of elongated martensite structure formed in the rolling direction is formed. Thereby, a magnet can be produced in the rotor core component by saturation magnetization. In FIGS. 6 to 9, the fibrous structure in the uniaxial direction is indicated by a chain line (-----) in the rolling direction.

[0058] <Process 203> This is a process of performing a heat treatment in which tension is applied along the formed and stretched fibrous structure in the rolling direction. The tension heat treatment is performed at a tension of 20 to 80 kg / mm 2 and a heat treatment at 400 to 600 °C. This strengthens the magnetic anisotropy and improves the magnet characteristics.

[0059] <Process 204> This is a process of punching out the rotor core component and the stator core component with a common axis by press working. This will be described with reference to FIG. 6. The semi-hard magnetic plate member 300 that has undergone tension heat treatment (the rolling direction is indicated by the chain line 301 in the left-right direction) is first punched by press working to remove the unnecessary inclusion part 312, the center hole (for shaft) 313, and the slot part 323 in one or two punches to create voids prior to punching out the rotor core component 310. After manufacturing the rotor core component 310 by punching, the stator core component 320 is manufactured by punching.

[0060] <Process 205> The rotor core component 310 manufactured by press working is shown in FIG. 7. The rotor core component 310 is composed of a thin disk 311, and the inclusion part 312 where the rare earth bond magnet is injection molded and the center hole 313 for shaft insertion are punched out to form voids.

[0061] <Process 206> This is a process of manufacturing a rotor core by radially laminating the rotor core components 310. This will be described with reference to FIGS. 9 and 10. This is a process of laminating the rotor core components made of semi-hard magnetic plates (thin disks) having uniaxial anisotropy at an angle so as to have radial anisotropy characteristics and manufacturing a cylindrical shape having radial anisotropy as the entire core. The inner package part 312 has six axes. As shown in Fig. 9, in the first stage, it is parallel to the rolling direction, in the second stage, it is rotated 30 degrees clockwise from the rolling direction, in the third stage, it is further rotated 30 degrees for a total of 60 degrees of rotation, and in the fourth to sixth stages, it is rotated 30 degrees each to form 90 degrees of rotation, 120 degrees of rotation, and 150 degrees of rotation, and they are laminated to form radial anisotropic characteristics. Fig. 10 shows a perspective view of the rotor core 400 laminated in a cylindrical shape. As a result, radial characteristics are imparted to the induced transformation type magnet, enabling high-speed rotation.

[0062] <Process 207> Fig. 8 shows the stator core component 320 manufactured by press working. The stator core component 320 consists of a thin plate ring 321, has teeth 322 around which the field coil is wound, and slots 323 are punched out to form voids.

[0063] <Process 208> This is a heat treatment process in which the stator core component is subjected to recrystallization heat treatment at 600°C to 850°C, preferably 500°C to 700°C, to make it isotropic soft magnetic with a ferrite structure. As a result, the function as a stator can be exhibited, and it will be comparable to the electromagnetic steel sheet used in the conventional inner-embedded magnet type synchronous machine.

[0064] <Process 209> This is a process of laminating stator core components having isotropic soft magnetic characteristics by a heat treatment process and making them into a cylindrical stator core.

[0065] From the above manufacturing methods 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 (rotor core), and 2) For the stator core (stator core), the same material as the chemical composition of the rotor core can be used, thereby significantly reducing costs.

Example

[0066] An embodiment of the interior permanent magnet synchronous machine according to the present invention will be described with reference to FIGS. 1 to 10, using an 18Cr-8Ni series stainless steel composed of a non-magnetic austenite structure as a base material. FIG. 1 shows a cross-sectional view of a main part of a synchronous motor SM. FIG. 2 shows a plan view of a semi-hard magnetic material, an inner part, and a non-magnetic part that constitute a rotor preform. FIG. 3 shows a plan view of an induced transformation type magnet, a permanent magnet, and a non-magnetic part that constitute a rotor. FIG. 4 is a partial view of the rotor preform of FIG. 3, showing a plan view of (a) a punched material forming an inner part, (b) a non-magnetic part in a magnet end region, and (c) a non-magnetic part in a region on the outer peripheral side of a magnet end. FIG. 5 shows a flowchart of a manufacturing process of a rotor core and a stator core. FIG. 6 shows a semi-hard magnetic plate and shows a method of simultaneously punching a rotor core and a stator core from the semi-hard magnetic plate. FIG. 7 shows a plan view of a rotor core component manufactured by punching. FIG. 8 shows a plan view of a stator core component manufactured by punching. FIG. 10 shows a plan view of a rotor core component manufactured by punching. FIG. 12 shows a stacking method of a rotor core having radial anisotropy. FIG. 14 shows a perspective view of a stacked state of a rotor core. FIG. 8 shows a plan view of a stator core component manufactured by punching. FIG. 9 shows a stacking method of a rotor core having radial anisotropy. FIG. 14 shows a perspective view of a stacked state of a rotor core. The synchronous motor SM shown in FIG. 1 is of a 6-pole 18-slot type. The synchronous motor SM shown in FIG. 1 is of a 6-pole 18-slot type. Hereinafter, the stator S and the rotor 1 will be described in detail.

[0067] (1) Stator As shown in FIG. 1, the stator S is composed of a laminated steel sheet made of an 18Cr-8Ni series stainless steel ferrite structure, and includes an annular yoke Sa, teeth Sb protruding evenly from the yoke Sa toward the center direction, and slots Sc formed between adjacent teeth Sb. In each slot Sc, an electromagnetic coil (not shown) wound around the teeth Sb is accommodated. By supplying inverter-controlled three-phase alternating current to each electromagnetic coil, a rotating magnetic field with a synchronous speed corresponding to its frequency and number of poles is generated in the stator S.

[0068] (2) Rotor core component As shown in Fig. 2, the rotor core component 110 has a disk-shaped semi-rigid magnetic material 111 having a central hole 151 and inclusion portions 121 to 126 formed by equally spaced, axially symmetrically arranged, inwardly curved (convex-shaped) equal-width long grooves penetrating around the center. The semi-rigid magnetic material 111 is laminated (Figs. 9 and 10) by rotating by an angle corresponding to the number of inclusion portions. By laminating this semi-rigid magnetic material 111, a rotor core 110 having radial anisotropy is formed. The inclusion portions 121 to 126 formed by the long grooves become penetrating inclusion 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 fitted.

[0069] The ends of the inclusion portions are modified portions 141 to 146 (non-magnetic portions) obtained by modifying the outer peripheral ends of the preliminary body 110 made of a semi-rigid magnetic material into a non-magnetic austenite structure. This modification treatment was performed by locally heating the outer peripheral region of the preliminary body 110, which is the treatment target portion, with a laser to 900 °C or higher.

[0070] (2) Rotor Permanent magnets M made of rare-earth anisotropic bonded magnets were formed by injection molding in a magnetic field in the inclusion portions 12 (121 to 126) having the modified portions 141 to 146 on the outer peripheral sides of both ends. Specifically, first, the preliminary body 110 is set in an injection filling device in a magnetic field (not shown), and an orientation magnetic field with alternately different polarities is applied between adjacent inclusion portions 12 toward the inclusion portions 12. Furthermore, while forming the permanent magnets M (121M to 126M), the preliminary body made of a semi-rigid non-magnetic material was saturated magnetized to form an induced transformation type 18Cr-8Ni series stainless steel magnet. Thus, the rotor body 11 was manufactured.

[0071] That is, a pellet composed of Nd-Fe-B-based anisotropic magnet powder, Sm-Fe-N-based magnet powder, and polyphenylene sulfide resin (binder resin) is injection-filled into these inner portions 12 with a molten mixture obtained by heating and melting. Thereafter, the molten mixture in the inner portion 12 is solidified by being cooled in the mold of the in-magnetic-field injection filling device, and a permanent magnet M integrally formed in the inner portion 12 is formed. Thus, a rotor 1 in which the permanent magnet M curved on the inner peripheral side is annularly and evenly encapsulated is obtained.

[0072] In this embodiment, an orientation magnetic field was applied to the slot 12 from the start to the end of the filling of the molten mixture. At this time, the orientation 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.

[0073] As a result, the magnet particles in the permanent magnet M not only orient during the in-magnetic-field injection molding but are also magnetized simultaneously, and the permanent magnet M was already in a state of exhibiting a high magnetic flux density. Therefore, in this embodiment, it was not necessary to perform post-magnetization.

[0074] The stator core is press-worked and punched out simultaneously with the rotor core from the magnet material plate of the above-described induced transformation type. Thereby, the material yield of the stator core and the rotor core material was improved. Next, it was made into a ferrite recrystallized structure having soft magnetic characteristics by annealing heat treatment at 650 °C for 30 minutes. It was laminated to form a stator core. A field coil was attached to a predetermined position of the stator core to manufacture a stator. A stator and a rotor were combined to manufacture an encapsulated magnet type synchronous machine.

[0075] (3) Motor A shaft (not shown) is inserted and attached to the shaft hole 19 of the rotor 1 that encapsulates the permanent magnet M. This rotor 1 is rotatably disposed in the stator S. At this time, the gap formed between the outer peripheral end surface of the rotor 1 and the inner end surface of the teeth Sb was made constant. Thus, this synchronous motor SM was 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 therewith.

[0076] 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 larger than the inductance Ld1 in the d-axis direction passing through the center of the permanent magnet M. Therefore, in the synchronous motor SM1, not only the magnet torque Tm1 by the permanent magnet M1 but also the reluctance torque Tr1 based on the inductance difference (Lq1 - Ld1) is generated in the same direction as the magnet torque Tm1. Accordingly, the synchronous motor SM1 exhibits a larger output. Also, the cogging torque is reduced. In the following embodiments, the definitions of the d-axis and q-axis are the same.

Industrial Applicability

[0077] It can be widely used, such as in vehicle drive motors used in electric vehicles, hybrid vehicles, or railway vehicles, home appliance motors used in air conditioners, refrigerators, or washing machines, and drive motors for various robotic devices.

Explanation of Symbols

[0078] SM: Synchronous motor (interior permanent magnet synchronous machine) 1: Rotor 10: Induced transformation type magnet (plate), 12: Interior 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: Slots

[0079] 110: Rotor preform (preliminary body) 111: Semi-rigid magnetic material, 121 - 126: Interior parts, 141 - 146: Non-magnetic parts 151: Shaft hole

[0080] 11: Rotor (body) 10: Induced transformation type magnet (induced transformation type magnet part) 110: Outer peripheral end of the body 121M to 126M: Permanent magnet 121Ma: One end of the permanent magnet 122Mb: The other end of the permanent magnet 141 to 146: Non-magnetic part 151: Shaft hole

[0081] 30: Semi-hard magnetic material with an inner part punched out 111: Semi-hard magnetic material (preliminary body) 111e: Outer peripheral end of the preliminary body 121 to 122: Inner part 121a: One end of the inner part 121 121am: Magnet end region of the inner part 121 121b: The other end of the inner part 121 122a: One end of the inner part 122 122b: The other end of the inner part 122 30A: Non-magnetic part of the magnet end region 121 to 122: Inner part 141a: Non-magnetic part obtained by modifying the magnet end region 121am 141b: Non-magnetic part obtained by modifying the magnet end region 121bm (not shown in the figure) 142a: Non-magnetic part obtained by modifying the magnet end region 122am (not shown in the figure) 142b: Non-magnetic part obtained by modifying the magnet end region 122bm (not shown in the figure) 30B: Non-magnetic part of the outer peripheral side region of the magnet end region 121 to 122: Inner part 141: Outer peripheral side region of the magnet end region (121am, 122bm and the connecting region between them) Non-magnetic part 142: Non-magnetic part of the outer peripheral side region of the magnet end region 146: Non-magnetic part of the outer peripheral side region of the magnet end region

[0082] 300: Simultaneous punching process of the rotor core and the stator core 301: Tension heat-treated semi-hard magnetic plate member 302: Rolling direction (dashed line) 310: Rotor core component 311: Thin plate disk 312: Inner packaging part 313: Central hole 320: Stator core component 321: Thin plate ring 322: Teeth 323: Slots 400: Rotor core (radially laminated in a cylindrical shape)

Claims

1. The rotor of the interior permanent magnet synchronous machine comprises a rotor core and permanent magnets, wherein the rotor core consists of a laminate of rotor core components made of a magnet of an induced transformation martensite structure, has an even number of inclusion parts each consisting of a void axially symmetrically arranged around the rotation center axis, and has radial anisotropy, wherein an even number of the permanent magnets are disposed in the inclusion parts and each permanent magnet consists of a rare earth anisotropic bonded magnet injection-molded within the inclusion part with an orientation magnetic field applied thereto, and a magnet end region from an end of the permanent magnet to an outer peripheral end of the rotor core is a non-magnetic part. A rotor characterized by this.

2. In Claim 1, a magnet end outer peripheral side region including a magnet end region from one end of the permanent magnet to an outer peripheral end of the rotor core, a magnet end region from the other end of another permanent magnet adjacent to the permanent magnet to an outer peripheral end of the rotor core, and a connection region connecting the magnet end regions is made of a non-magnetic part. A rotor characterized by this.

3. In the stator of the interior permanent magnet synchronous machine, the stator core of the stator has the same chemical composition as the rotor core described in Claim 1, and consists of a laminate of heat-treated stator core components. A stator characterized by this.

4. An interior permanent magnet synchronous machine characterized by comprising the rotor described in Claim 1 or Claim 2 and a stator.

5. In a method for manufacturing a rotor core of a rotor and a stator core of a stator constituting an interior permanent magnet synchronous machine, (1) A plate member of an Fe-based alloy having a non-magnetic austenite structure is cold-rolled at a low temperature to induce a martensite structure of 80% or more to obtain a semi-hard magnetic plate member, (2) Heat treatment is performed by applying a tension along a fiber structure formed and stretched in the rolling direction, (3) By press working, a rotor core component and a stator core component are punched out from the plate member with a common axis, (4) The rotor core is formed by laminating rotor core components made of a magnet having uniaxial anisotropy as a whole core at an angle so as to have radial anisotropy characteristics to form a cylindrical shape having radial anisotropy, (5) The stator core is formed by making the stator core component into an isotropic soft magnetic ferrite structure by recrystallization heat treatment and then laminating it into a cylindrical shape, A manufacturing method characterized by manufacturing the rotor core and the stator core.

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