JP2016194127A - Induction heating method of rotor of ipm motor and induction heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an induction heating method for locally heating only necessary portions in a short period of time for local material improvement in a rotor of an IPM motor and obtaining the rotor of the IPM motor provided with excellent magnetic characteristics and high strength, and further to provide an induction heating device.SOLUTION: Coils 32 are provided closer to a rotor 11 of an IPM motor 1 in a shape surrounding local portions (bridge portions 21) required for heat treatment, a single-phase AC power source 31 is connected to the coils 32, an AC magnetic field is generated, an eddy current is generated in the rotor 11 by the AC magnetic field, and the local portions are imparted with heat treatment effect.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an induction heating method and an induction heating apparatus for a rotor of an IPM motor using an electromagnetic steel plate.

  Main drive motors and main generator motors of electric drive vehicles such as hybrid vehicles (HEV) and electric vehicles (EV) are required to have high efficiency at a high level in order to be directly connected to fuel consumption. In addition, in order to reduce the size and weight of the motor core without lowering the motor output, further higher speed rotation is required. In recent years, a motor having an output of several tens kW and a rotation speed close to 20000 rpm is required.

  In order to increase the efficiency of IPM motors (magnet motors) used in most of the main motors of electrically driven vehicles, the magnetic fluxes from the north and south poles of the magnet of the IPM motor rotor must be coupled through the electromagnetic steel plate of the rotor. There is a need to increase the motor torque by preventing the motor. Therefore, conventionally, the bridge between the end of the opening for inserting the magnet and the side surface of the rotor is made as thin as possible to make it difficult for the magnetic flux to pass through the bridge, or the magnetic permeability of the bridge is lowered to reduce the magnetic flux. It has been considered to make it difficult to pass. On the other hand, because the main motor is required to rotate at higher speeds due to the demand for smaller size and lighter weight, the rotor material requires higher strength electrical steel sheets in addition to electromagnetic characteristics such as low iron loss. It has become. In addition, in the manufacturing process of punching and laminating electromagnetic steel sheets into a rotor shape, there is a desire to locally heat only necessary portions for local material improvement after laminating the rotor core. Furthermore, it is desirable to complete this heating in a short time from the viewpoint of improving productivity. Therefore, it is necessary to develop a technique for short-time local heating that realizes this.

  In order to increase the strength of the rotor material, solid solution strengthening, precipitation strengthening, grain refinement strengthening, dislocation strengthening, transformation strengthening, etc. of the electrical steel sheet used for the material can be considered. Since the characteristics are deteriorated, it is not preferable for the electromagnetic steel sheet. Further, solid solution strengthening has a great effect on increasing the strength, but at the same time, there are problems of increased rolling load and brittle fracture, and there is an upper limit from the viewpoint of productivity.

  The rotor material of the IPM motor does not require the low iron loss characteristics as the stator material, but the reluctance torque caused by the flow of the magnetic flux that fluctuates in the rotor is used at a certain ratio, so that the iron loss is low. The higher the motor efficiency.

  For example, Non-Patent Document 1 proposes an electrical steel sheet that achieves both high strength and low iron loss by finely dispersing a metal phase made of Cu in a size of several nanometers. Furthermore, electrical steel sheets that include a fine Cu metal phase and have both high strength and low iron loss are disclosed in, for example, Patent Document 1, Patent Document 2, and the like.

  Patent Document 3 discloses a heating device that can heat an arbitrary region in the width direction of a steel plate.

  Further, Patent Document 4 discloses a method and apparatus for magnetically annealing a motor core because the iron loss can be reduced by annealing in a magnetic field in the same direction as the excitation direction of the electromagnetic steel sheet.

  Patent Document 5 discloses an electromagnetic steel sheet that achieves both high strength and low iron loss by a fine intermetallic compound.

Japanese Patent No. 5000136 JP 2011-006721 A Japanese Patent No. 3793503 JP 2003-342637 A JP 2005-264315 A

Edited by Japan Iron and Steel Institute, Materials and Processes: CAMP-ISI Vol. 27 (2014) -467

  However, Patent Documents 1 and 2 and Non-Patent Document 1 are for depositing a metal phase made of Cu on the entire electromagnetic steel sheet, which is a material for a rotor. For this reason, there is a problem that heat treatment must be performed on the entire electromagnetic steel sheet, and a Cu phase is also deposited at a portion that does not require particularly high strength, thereby deteriorating magnetic properties.

  Further, Patent Document 3 does not realize local heating at a level of several millimeters. Further, Patent Document 4 heats the entire core, and does not realize local heating only at a portion requiring low iron loss and high strength.

  The present invention relates to an induction heating method for obtaining a rotor of an IPM motor having excellent magnetic properties and high strength by locally heating only a necessary portion for local material improvement in a short time in a rotor of an IPM motor. And it aims at providing an induction heating apparatus.

  In order to solve the above problem, the present invention provides an induction heating method for heating a local part of an IPM motor rotor that requires heat treatment, wherein a coil is provided in a shape surrounding the local part in the vicinity of the rotor, and the coil is provided in the coil. An induction heating method for a rotor of an IPM motor, wherein an AC magnetic field is generated by connecting a single-phase AC power source, an eddy current is generated in the rotor by the AC magnetic field, and a heat treatment effect is given to the local part I will provide a.

  In the induction heating method, the rotor has a plurality of local portions that require the heat treatment, and the coils are sequentially moved so that the coils surround the local portions, respectively, so that a heat treatment effect is given to the local portions. May be. Alternatively, the rotor may have a plurality of local portions that require the heat treatment, and the rotor may be rotated or moved so that the coil surrounds the plurality of local portions, respectively, thereby giving a heat treatment effect to each of the local portions. .

  Further, a magnetic flux enhancing core may be provided inside the coil. In that case, the width dimension of the magnetic flux strengthening core is 0.5 to 1.5 times the local part, or the width dimension of the magnetic flux strengthening core is 0.8 to 1.0 times the local width. It is preferable that

  The rotor has a plurality of local portions that require the heat treatment, and a coil including the magnetic flux strengthening core is disposed on the outer peripheral side of the rotor so as to surround all of the local portions at a plurality of locations, and the coils The magnetic flux reinforcing cores may be connected on the outer peripheral side of the coil. In that case, the phases of adjacent coils may be reversed.

  The excitation frequency is preferably 100 to 20 kHz.

The local part may be strengthened by partial precipitation by giving a heat treatment effect to the local part. In that case, the said local part is the mass%, C: 0.06% or less, Si: 0.2-4.0%, Mn: 0.05-2.0%, Al: 2.50% or less, Cu : 0.5 to 8.0%, a bridge portion of a rotor made of an electromagnetic steel plate made of the balance Fe and unavoidable impurities as a raw material, and the bridge portion at 400 ° C to 700 ° C for 1 second to 10 minutes In this case, fine Cu particles having an equivalent circle diameter of 10 nm or less may be deposited on the bridge portion. Moreover, the said local part is the mass%, Si: 2.0-4.0%, Al: 1.0-3.0%, Ni: 1.5-4.0%, The remainder Fe and unavoidable Of a rotor made of an electromagnetic steel plate made of mechanical impurities, the bridge portion is subjected to an aging treatment at 400 ° C. to 600 ° C., and the average value of the equivalent circle diameter is 1 to 10 nm. You may deposit 30000 pieces / micrometer ³ or more of intermetallic compounds.

  The local part is a magnet part of a rotor of an IPM motor manufactured from an electromagnetic steel sheet as cold-rolled. The magnetic part is subjected to a heat treatment effect at 700 ° C. or more for 1 second or more, and the magnet part is partially recrystallized. You may let them. The local part is a sheared part or welded part of a rotor of an IPM motor made from an electromagnetic steel sheet as cold-rolled, and gives a heat treatment effect for 1 second or longer at 400 ° C. or higher to the sheared part or welded part. The distortion of the sheared part or the welded part may be removed.

  The present invention also provides an induction heating device for heating a local part of an IPM motor rotor that requires heat treatment, a coil provided in a shape surrounding the local part in the vicinity of the rotor, and a coil connected to the coil and connected to the coil. And a single-phase AC power source for generating an AC magnetic field, and generating an eddy current in the rotor by the AC magnetic field to give a heat treatment effect to the local portion, induction heating of the rotor of the IPM motor Providing equipment.

  In the induction heating apparatus, a magnetic flux reinforcing core may be provided inside the coil. In that case, the width dimension of the magnetic flux strengthening core is 0.5 to 1.5 times the local part, or the width dimension of the magnetic flux strengthening core is 0.8 to 1.0 times the local width. It is preferable that

  A coil provided with the magnetic flux reinforcing core is arranged on the outer peripheral side of the rotor so as to surround each of the local portions at a plurality of locations, and the magnetic flux reinforcing core of each coil is connected on the outer peripheral side of the coil May be. In that case, the phases of adjacent coils may be reversed.

  The excitation frequency is preferably 100 to 20 kHz.

  According to the present invention, in a rotor of an IPM motor, only a necessary portion can be locally heated in a short time for local material improvement required for a high-speed rotation IPM motor, and excellent magnetic properties and high strength can be obtained. The rotor of the IPM motor provided with can be obtained.

It is a perspective view explaining the structure of an IPM motor. It is a top view of a rotor. It is explanatory drawing of the stress distribution at the time of high speed rotation which expanded the A section of the rotor of FIG. It is explanatory drawing which shows the example which has arrange | positioned the induction heating apparatus concerning embodiment of this invention close to the rotor. FIG. 5 is a plan view of FIG. 4. It is a perspective view which shows the example which provided the induction heating apparatus concerning different embodiment of this invention close to the rotor. FIG. 7 is a plan view of FIG. 6. It is explanatory drawing which shows the example of the heating method by the induction heating apparatus shown in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an explanatory diagram of the structure of an IPM motor 1 used as a drive motor for an electric vehicle, a hybrid electric vehicle, a fuel cell vehicle, and the like. A rotor 11 that is a rotor is inserted inside a cylindrical stator 10. The stator 10 is provided with a plurality of teeth 15 projecting toward the rotor 11 on the inner side, and the teeth 15 are radially arranged symmetrically with respect to the rotation center axis O of the rotor 11. . A coil is formed on each tooth 15 by winding a winding 16 by a concentrated winding method. The winding 16 of the teeth 15 includes a distributed winding method in addition to the concentrated winding method, and is selected by comprehensively considering cost, winding space factor, cogging characteristics, etc. It does not depend on the winding method of the teeth 15 of the stator 10.

  As shown in FIG. 2, the rotor 11 of this embodiment exemplifies an 8-pole rotor provided with eight openings 20 into which magnets are inserted. A bridge portion 21 is between the end of each opening 20 and the rotor side surface. In recent years, drive motors used in hybrid vehicles (HEV) and electric vehicles (EV) have been revolving at a high speed, but a strong centrifugal force acts on the bridge portion 21 during high-speed rotation.

  According to the simulations of the present inventors, the stress distribution of the centrifugal force acting on the rotor 11 during high-speed rotation has a result as shown in FIG. That is, in the rotor 11 during high-speed rotation, strong stress acts on the bridge portion 21, and stress concentration is particularly concentrated on a portion near the corner portion on the outer side of each opening 20 (a hatched area in FIG. 3). It has been found that deformation and fatigue failure of the rotor 11 are likely to occur.

  As described above, for example, by dispersing a metal phase composed of Cu or an intermetallic compound such as Al-Ni as precipitates having a size of several nm, it is possible to obtain an electrical steel sheet that achieves both high strength and low iron loss. It is well known. The formation of this fine precipitate requires a heat treatment at a relatively low temperature of about 500 ° C., but the high strength is required only for the bridge portion 21 of the rotor 11 where stress concentration is likely to occur. It is. Therefore, a coil is provided in a shape surrounding the bridge portion 21, a single-phase AC power supply is connected to the coil to generate an AC magnetic field, and an eddy current is generated in the rotor by the AC magnetic field, whereby only the bridge portion 21 is localized. Therefore, if the temperature is raised to a predetermined temperature, a fine precipitate having a required size can be efficiently obtained, and the strength of the bridge portion 21 can be increased. In addition, since fine precipitates are formed in the bridge portion 21, the magnetic permeability is lower than that in the non-deposition portion, the leakage magnetic flux from the bridge portion 21 is suppressed, and the magnetic coupling between adjacent magnets is achieved. The suppression effect is great, and the motor efficiency can be further increased. In this way, the present invention, for example, heats only the local area where stress concentration is likely to occur and requires high strength in the motor member, thereby depositing, for example, a fine Cu metal phase or a fine intermetallic compound only in the local area. This increases the strength and improves the performance of the motor.

  Hereinafter, as an example according to the embodiment of the present invention, a case where fine Cu particles are precipitated only locally by induction heating will be described. In this embodiment, the local part that requires heat treatment is the bridge part of the rotor of the IPM motor.

  The magnetic steel sheet used as the material of the rotor of the IPM motor in the present embodiment is, for example, mass%, C: 0.06% or less, Si: 0.2 to 4.0%, Mn: 0.05 to 2.0. %, Al: 2.50% or less, Cu: 0.5 to 8.0%, and the balance is Fe and inevitable impurities.

  C not only deteriorates the magnetic properties, but also induces martensitic transformation in the heat treatment to deteriorate the magnetic properties, so 0.06% or less. From the viewpoint of production cost, it is advantageous to reduce the amount of C by degassing equipment at the molten steel stage, and if it is 0.003% or less, the effect of suppressing magnetic aging and the effect of avoiding martensitic transformation are remarkable, and high strength In the present invention in which non-metal precipitates such as carbides are not used as the main means of conversion, the content is more preferably 0.002% or less, and further preferably 0.0015% or less. It may be 0%.

  Si increases the specific resistance of steel to reduce eddy current and iron loss, and increases the tensile strength. However, the effect is small when the addition amount is less than 0.2%. If the Si content is increased, it is possible to increase the strength while reducing the iron loss. Therefore, the Si content is preferably 1.0% or more, and more preferably 2.0% or more. Further, if it exceeds 4.0%, the steel is embrittled and further the magnetic flux density of the product is deteriorated, so 4.0% or less, preferably 3.5% or less. In order to further reduce the fear of embrittlement, it is preferably 3.2% or less, and if it is 2.8% or less, there is a balance with the amount of other elements, but there is almost no need to consider the embrittlement.

  Mn may be positively added to increase the strength of the steel, but is not particularly required for this purpose in the present invention in which Cu particles are utilized as the main means for increasing the strength. It is added for the purpose of reducing iron loss by increasing the specific resistance or coarsening the sulfide to promote crystal grain growth. However, excessive addition deteriorates the magnetic flux density, so 0.05 to 2.0%. To do. Preferably, it is 0.5% to 1.2%.

  Al is usually added as a deoxidizing agent, but it is also possible to suppress the addition of Al and deoxidize with Si. In particular, in the case of non-oriented electrical steel sheets, Si deoxidized steel having an Al content of about 0.005% or less has an effect of reducing iron loss because AlN is not generated. On the contrary, it can be actively added to promote the coarsening of AlN and the iron loss can be reduced by increasing the specific resistance. However, if it exceeds 2.50%, embrittlement becomes a problem. To do.

  Cu is limited to 0.5 to 8.0% as a range for forming a metal phase mainly composed of Cu at a desired location in the steel plate and increasing the strength within a range that does not adversely affect the magnetic properties. . When the Cu content is low, the effect of increasing the strength is reduced, and the heat treatment conditions for obtaining the effect of increasing the strength are limited to a narrow range, and the degree of freedom in management of production conditions and production adjustment is reduced. Further, when the Cu content is high, the influence on the magnetic properties is increased, and not only the magnetic flux density is particularly lowered, but there is a concern that cracking and wrinkling of the steel sheet during hot rolling become severe. In particular, Cu exceeding the solid solubility limit in steel contributes to high strength as precipitated Cu, but the efficiency becomes lower than that of the Cu phase, which is the main purpose of the present invention. Further, excessive Cu forms a metal phase in the steel in an undesired process depending on the heat history, for example, a relatively coarse Cu metal phase at a high temperature during hot rolling, and the subsequent fine metal phase. It may act unfavorably in the formation of, and may adversely affect the magnetic properties. Preferably it is 0.7 to 4.0%, more preferably 0.8 to 3.5%.

  The electrical steel sheet (material) used for manufacturing the high-strength member for a motor according to this embodiment is based on the above component composition, and consists of the remaining Fe and unavoidable impurities. In addition, said component composition is one Embodiment with which this invention is applied, Application of this invention is not limited to the rotor which uses the electromagnetic steel plate of this component composition as a raw material.

  The non-oriented electrical steel sheet (material) used for the manufacture of the rotor of the IPM motor is made by melting the steel containing the above-mentioned components into a steel slab by continuous casting, followed by hot rolling, cold rolling and annealing. can get. Further, in addition to these steps, an insulating film formation or a decarburization step may be performed.

  The non-oriented electrical steel sheet containing Cu thus obtained is formed into a predetermined shape necessary as a rotor of an IPM motor by a method such as punching. In this case, the electromagnetic steel sheet is still soft at the material stage, and can be easily processed into the shape of the rotor.

Next, as shown in FIGS. 4 and 5, an induction heating device 30 is provided around a local area where high strength is required, for example, the bridge portion 21. The induction heating device 30 has a coil 32 connected to a single-phase AC power supply 31. The coil 32 is provided in a shape that surrounds the bridge portion 21 when viewed from the side of the rotor 11 in the vicinity of the outer peripheral side of the rotor 11, and a magnetic flux reinforcing core 33 is provided inside the coil 32. As the coil 32, a winding coil obtained by spirally winding a copper wire or a water-cooled drum pipe is used. The magnetic flux strengthening core 33 is made of, for example, laminated electromagnetic steel sheets. If the width dimension Wc in the circumferential direction of the rotor 11 is too small with respect to the width dimension Wb of the bridge portion, a heat treatment effect within a necessary range is obtained. However, if it is too large, it will heat outside the necessary range, so it is 0.5 to 1.5 times, preferably 0.8 to 1.0 times Wb. In addition, the width | variety of a bridge | bridging part refers to the distance between the bridge | bridging part 21 between the adjacent opening parts 20, and the bridge | bridging part 21, as shown in FIG. An alternating magnetic field is generated in the coil 32 by the alternating current power source 31 and an eddy current is generated in the rotor 11 by the alternating magnetic field, so that the bridge portion 21 has a heat treatment effect of, for example, 400 ° C. to 700 ° C. for 1 second to 10 minutes. give. The excitation frequency is appropriately set according to the material of the magnetic steel sheet, the local size, and the like. This is because if the frequency is too low, it becomes difficult to raise the temperature within a predetermined time by heating efficiency, and if the frequency is too high, the heating is limited to a local area and the temperature rises due to heat conduction in the electrical steel sheet. This is because even if the temperature effect is included, a heat treatment effect in a necessary range cannot be obtained. For example, when the skin depth is determined from the relative magnetic permeability 160 of steel type 50H470 at an electrical resistivity of 39 × 10 ⁻⁸ [Ω · m] and a magnetic flux density of about 1.8 T, it is about 5.5 mm at 20 Hz and about 2. at 100 Hz. It is about 0.8 mm at 5 mm and 1 kHz, about 0.45 mm at 3 kHz, and about 0.25 mm at 20 kHz. When the thickness of the bridge portion of the rotor 11 using this steel type is about 1 to 5 mm, it is about 20 to 1 kHz in order to obtain an excitation frequency equivalent to the skin depth. Therefore, the frequency regulation is set to 100 to 20 kHz. More preferably, in order to make the skin depth equal to or less than the minimum thickness of the bridge portion, the depth is set to 1 to 3 kHz.

  Thereby, the material of a heating part and a non-heating part is made into a different material optimal for each site | part in the rotor 11. FIG. For example, in the present embodiment, only the bridge portion 21 of the rotor 11 made of an electromagnetic steel sheet containing Cu is locally heated by induction heating, and the bridge portion 21 alone is several nm in size (equivalent circle diameter is 10 nm or less). The fine Cu particles are deposited to increase the strength. Since the rotor 11 other than the bridge portion 21 does not have a heat treatment effect, there is no precipitation of Cu particles, and good iron loss characteristics can be maintained. That is, the strength of the rotor 11 is improved without deteriorating the magnetic characteristics, the efficiency of the IPM motor 1 is improved, and the rotor 11 is used as a rotor 11 that can withstand high-speed rotation aimed at downsizing a main motor such as an electric drive vehicle. Can do.

  In the said embodiment, although the example which partially precipitates fine Cu particle | grains and heightened was described, the bridge | bridging part 21 of the rotor 11 produced with the electromagnetic steel plate containing intermetallic compound formation elements, such as Al and Ni, for example was described. May be locally heated by induction heating, and fine intermetallic compound particles made of Al, Ni or the like having a size of several nm may be deposited only on the bridge portion 21.

  In this case, the electrical steel sheet used as the material of the rotor of the IPM motor is, for example, mass%, Si: 2.0 to 4.0%, Al: 1.0 to 3.0%, Ni: 1.5 to 4 0.0%, and the balance is Fe and inevitable impurities. In order to avoid martensitic transformation, a higher Si content is convenient, and the Si content is set to 2.0 to 4.0%. Al contains at least 1.0% in order to obtain the effect of precipitation strengthening of the intermetallic compound. Ni is contained in order to form an intermetallic compound with Al and develop precipitation strengthening by the intermetallic compound of Al-Ni. In order to develop precipitation strengthening by the intermetallic compound of Al—Ni, 1.5% or more of Ni is necessary. On the other hand, excessive addition deteriorates the ductility of the steel sheet and lowers the sheet-passability. In addition, the magnetic flux density is lowered and it is sometimes difficult to suppress preferable formation of intermetallic compounds in the production process. In particular, Ni is an austenite stabilizing element, and in order to easily cause martensitic transformation to be avoided in this embodiment, the upper limit is set to 4.0% considering the addition cost.

Furthermore, after applying plastic deformation with a dislocation density of 10 ¹⁴ / m ² or more to the bridge portion, an aging treatment is performed at 400 ° C. to 600 ° C., and the average value of the equivalent circle diameter is 1 to 10 nm. 30000 / μm ³ or more of the intermetallic compound is deposited. The dislocation density of the steel sheet is 10 ¹⁴ / m ² or more because the dislocation is sufficiently generated in the steel sheet by plastic working after annealing, and the dislocation is used as a precipitation site to make the size of the steel sheet as uniform as possible. This is because the Ni intermetallic compound is dispersed and precipitated. If the dislocation density is less than 10 ¹⁴ / m ² , the intermetallic compound precipitation sites are insufficient, and an Al—Ni intermetallic compound having a number density of 30000 / μm ³ or more cannot be obtained after aging. Further, when the number density of the Al—Ni intermetallic compound is small, the average value of the equivalent circle diameter of the intermetallic compound is larger than 10 nm, and the variation in the size of each intermetallic compound is also increased. The reason why the aging treatment is performed at 400 to 600 ° C. is that when the temperature is lower than 400 ° C., a sufficient intermetallic compound cannot be obtained, and when the temperature exceeds 600 ° C., the formed intermetallic compound becomes coarse.

  For example, as shown in FIG. 4, when one coil 32 is provided and heat treatment is performed, the position of the coil 32 is sequentially moved so as to surround the bridge portions 21 at a plurality of locations, and each bridge portion 21 is heat treated. Alternatively, each bridge portion 21 may be heat-treated by rotating or moving the rotor 11 so that the position of the coil 32 becomes a position that sequentially surrounds the plurality of bridge portions 21.

  6 and 7 are different examples of the induction heating device 40 according to the embodiment of the present invention, FIG. 6 is a perspective view, and FIG. 7 is a plan view. In this induction heating device 40, the coil 32 provided with the magnetic flux reinforcing core 33 is disposed so as to be close to the outer peripheral side of the rotor 11 so as to surround each of the plurality of bridge portions 21 of the rotor 11, Each magnetic flux reinforcing core 33 is connected on the outer peripheral side of the coil 32. In this case, as shown in FIG. 8, heating can be performed more efficiently by inverting the phase of the adjacent coils 32.

  In addition, as an example, although the form which applied this invention was demonstrated about the case where the local part which requires heat processing is the bridge part 21 of the rotor 11 of the IPM motor 1, application of this invention is not limited to this form. For example, only the magnet part of an IPM rotor made of an electromagnetic steel sheet as cold-rolled is locally heated by an induction heating device, so that the magnet part has high magnetic permeability and the bridge part 21 has high strength and low magnetic permeability. Can be maintained. In this case, the magnet part can be partially recrystallized by giving the magnet part a heat treatment effect at 700 ° C. or higher for 1 second or longer.

  Furthermore, the sheared portion where the processing strain has occurred during the production of the rotor 11 of the IPM motor 1 and the welded portion where the welding strain has occurred are locally heated by the induction heating device to remove the strain and increase the magnetic permeability. In this case, the present invention can be applied. In this case, it is preferable to give a heat treatment effect at 400 ° C. or higher for 1 second or longer at a local portion formed of a sheared portion or a welded portion. The heat treatment of the shearing portion may be part of the shearing portion.

  The partial heating method that can realize partial strength enhancement as in the present invention is not only high strength, but also partial heating of the rotor, for example, partially softening the rotor, and further changing by heat. It can also be widely applied to the purpose of partially controlling a known material.

  In mass%, C: 0.004%, Si: 2.8%, Mn: 0.3%, Al: 0.65%, Cu: 1.6%, balance Fe and 0.35mm consisting of inevitable impurities Using a thick electromagnetic steel sheet as a material, two rotors were produced by punching into the shape of a rotor of an IPM motor and stacking them. Heat treatment was applied to one rotor bridge portion of the rotor. Specifically, since the width Wb of the bridge portion is 3.0 mm, the width dimension Wc in the circumferential direction of the magnetic flux reinforcing core 33 is 2.5 mm, and the coil 32 is formed by winding 40 turns of a copper wire. Then, a single-phase AC power source with a frequency of 3 kHz was connected to the coil and heated at an output of 2 kW. As a result, the bridge portion was heated to about 650 ° C. in about 5 minutes from the start of heating, and was cooled after maintaining this state for 10 seconds. Table 1 shows the motor efficiency of the IPM motor incorporating this rotor core and the rotor revolution speed.

  As shown in Table 1, it was found that by giving a heat treatment effect by induction heating, the fracture strength of the rotor is improved and at the same time the motor efficiency is improved.

  Table 2 shows the time required to raise the temperature to 650 ° C. when the frequency of the single-phase AC power supply is changed. At a frequency of 50 Hz, the temperature could not be increased to 650 ° C. Further, at a high frequency of 20 kHz, the temperature reached 650 ° C. in about 1 minute.

  In addition to the local heating of the rotor of the IPM motor, the present invention is a material that is locally softened by local heating of intermetallic compound type high-strength steel or full-hard type high-strength steel, and is further known to change due to heat. The same can be applied to the purpose of partially controlling.

DESCRIPTION OF SYMBOLS 1 IPM motor 10 Stator 11 Rotor 15 Teeth 16 Winding 20 Opening part 21 Bridge part 30, 40 Induction heating apparatus 31 AC power supply 32 Coil 33 Core for magnetic flux reinforcement

Claims (21)

An induction heating method for heating a portion of an IPM motor rotor that requires heat treatment,
A coil is provided in a shape surrounding the local portion in the vicinity of the rotor, a single-phase alternating current power source is connected to the coil to generate an alternating magnetic field, an eddy current is generated in the rotor by the alternating magnetic field, and the local portion A method for induction heating of a rotor of an IPM motor, wherein a heat treatment effect is imparted to the rotor.   The rotor has a plurality of local portions that require the heat treatment, and the coils are sequentially moved so that the coils surround the local portions, respectively, and a heat treatment effect is imparted to each of the local portions, The induction heating method of the rotor of the IPM motor according to claim 1.   The rotor has a plurality of local portions that require the heat treatment, and the rotor is rotated or moved so as to surround the plurality of local portions, respectively, and a heat treatment effect is given to each of the local portions. The induction heating method of the rotor of the IPM motor according to claim 1.   The induction heating method for a rotor of an IPM motor according to any one of claims 1 to 3, wherein a core for magnetic flux enhancement is provided inside the coil.   5. The method of induction heating a rotor of an IPM motor according to claim 4, wherein a width dimension of the magnetic flux enhancing core is 0.5 to 1.5 times the local part.   5. The induction heating method for a rotor of an IPM motor according to claim 4, wherein a width dimension of the magnetic flux enhancing core is 0.8 to 1.0 times a width of the local portion.   The rotor has a plurality of local portions that require the heat treatment, and a coil including the magnetic flux strengthening core is disposed on the outer peripheral side of the rotor so as to surround all of the local portions at a plurality of locations, and the coils The method for induction heating of a rotor of an IPM motor according to any one of claims 4 to 6, wherein the magnetic flux reinforcing cores are connected on the outer peripheral side of the coil.   The induction heating method for a rotor of an IPM motor according to claim 7, wherein the phases of adjacent coils are reversed.   The induction heating method for a rotor of an IPM motor according to any one of claims 1 to 8, wherein the excitation frequency is 100 to 20 kHz.   The induction heating method for a rotor of an IPM motor according to any one of claims 1 to 9, wherein the local part is subjected to a heat treatment effect to strengthen the local precipitation partly.   The local parts are in mass%, C: 0.06% or less, Si: 0.2-4.0%, Mn: 0.05-2.0%, Al: 2.50% or less, Cu: 0.00. It is a bridge portion of a rotor made of a magnetic steel plate made of 5 to 8.0%, the remainder Fe and inevitable impurities, and the bridge portion has a heat treatment effect at 400 ° C. to 700 ° C. for 1 second to 10 minutes. 11. The induction heating method for a rotor of an IPM motor according to claim 10, wherein fine Cu particles having an equivalent circle diameter of 10 nm or less are deposited on the bridge portion. The local part contains, by mass%, Si: 2.0 to 4.0%, Al: 1.0 to 3.0%, Ni: 1.5 to 4.0%, and the balance Fe and inevitable impurities A bridge portion of a rotor made of an electromagnetic steel plate made of a material, and the bridge portion is subjected to an aging treatment at 400 ° C. to 600 ° C., and an average circle equivalent diameter is between 1 and 10 nm. The method for induction heating of a rotor of an IPM motor according to claim 10, wherein 30000 compounds / μm ³ or more are deposited.   The local part is a magnet part of a rotor of an IPM motor manufactured from an electromagnetic steel sheet as cold-rolled, and the magnet part is subjected to a heat treatment effect at 700 ° C. or more for 1 second or more to partially recrystallize the magnet part. The method for induction heating of a rotor of an IPM motor according to any one of claims 1 to 9, wherein:   The local part is a sheared part or welded part of a rotor of an IPM motor made from an electromagnetic steel sheet as cold-rolled, and gives a heat treatment effect at 400 ° C. or higher for 1 second or longer to the sheared part or welded part, The induction heating method for a rotor of an IPM motor according to any one of claims 1 to 9, wherein distortion of the sheared portion or the welded portion is removed. An induction heating device that heats a portion of an IPM motor rotor that requires heat treatment,
A coil provided in a shape surrounding the local portion in the vicinity of the rotor, and a single-phase AC power source connected to the coil and generating an AC magnetic field in the coil, and eddy current is generated in the rotor by the AC magnetic field. An induction heating device for a rotor of an IPM motor, characterized in that the heat treatment effect is generated on the local part.   The induction heating apparatus for a rotor of an IPM motor according to claim 15, wherein a magnetic flux enhancing core is provided inside the coil.   17. The induction heating apparatus for an IPM motor rotor according to claim 16, wherein a width dimension of the magnetic flux strengthening core is 0.5 to 1.5 times the local part.   17. The induction heating apparatus for a rotor of an IPM motor according to claim 16, wherein a width dimension of the magnetic flux strengthening core is 0.8 to 1.0 times a width of the local portion.   A coil provided with the magnetic flux reinforcing core is arranged on the outer peripheral side of the rotor so as to surround each of the local portions at a plurality of locations, and the magnetic flux reinforcing core of each coil is connected on the outer peripheral side of the coil The induction heating device for a rotor of an IPM motor according to any one of claims 16 to 18, wherein the induction heating device is a rotor.   20. The induction heating apparatus for a rotor of an IPM motor according to claim 19, wherein the phases of adjacent coils are reversed.   The induction heating method for a rotor of an IPM motor according to any one of claims 15 to 20, wherein the excitation frequency is 100 to 20 kHz.