Methods and systems for demagnetizing permanent magnets in rotating electrical machines and methods for removing the rotor.

Abstract

This invention provides a method for demagnetizing the permanent magnet of a rotating electric motor, a system for demagnetizing the permanent magnet of a rotating electric motor, and a method for removing the rotor, all of which improve the ease of disassembly of the rotating electric motor. The method for demagnetizing the permanent magnet of a rotating electric motor includes: a step of detecting the circumferential position of the rotor (21); and a step of heating the permanent magnet (22). This method demagnetizes the permanent magnet (22) of a rotating electric motor (20) having a rotor (21) with a permanent magnet (22) and a winding (24) into which a power supply is applied. In the step of heating the permanent magnet (22), based on the circumferential position of the rotor (21) detected in the step of detecting the circumferential position of the rotor (21), an alternating current is applied to the winding (24) such that the direction of the resultant magnetic field of the winding (24) is aligned with the d-axis of the permanent magnet (22) of the rotor (21).

Description

Technical Field

[0001] This invention relates to a method for demagnetizing permanent magnets in a rotating electric motor mounted in an electric vehicle or the like, a system for demagnetizing permanent magnets in a rotating electric motor, and a method for removing the rotor. Background Technology

[0002] In recent years, from the perspective of global environmental protection and as an effort to achieve a low-carbon society, the electrification of power sources has been developing rapidly. For example, in the field of automobiles, electric vehicles equipped with batteries and powered by rotating motors driven by electricity stored in the batteries are becoming increasingly common.

[0003] On the other hand, in order to promote inclusive and sustainable industrialization, it is necessary to improve the efficiency of resource utilization and expand the introduction of clean technologies and environmentally friendly technologies and industrial processes. For rotating electric machines, it is also necessary to consider the 3Rs (Reduce, Reuse, Recycle) in the design stage.

[0004] Typically, the permanent magnets of the rotor of a rotating electric machine are permanent magnets with strong magnetic force. Therefore, when the rotor is removed from the rotating electric machine by sliding it axially relative to the stator, if the rotor is offset radially, the rotor will be strongly attached to the stator by the magnetic force of the permanent magnets, making it difficult to slide the rotor axially relative to the stator to remove it from the rotating electric machine.

[0005] Therefore, in the past, to remove the rotor from a rotating electric machine, it was necessary to use considerable force to overcome the strong magnetic force of the rotor's permanent magnets while preventing radial displacement, thus allowing the rotor to slide axially relative to the stator. This required specialized tools and equipment to overcome the strong magnetic force of the rotor's permanent magnets and allow the rotor to slide axially relative to the stator while preventing radial displacement. In limited locations without such specialized tools and equipment, it was impossible to remove the rotor from the rotating electric machine, resulting in poor disassembly convenience and increased disassembly costs.

[0006] As one of the technologies used to solve this problem, Patent Document 1 describes a method in which, when removing the rotor from a rotating electric machine, a high-frequency current (and, depending on the situation, a demagnetizing current) is passed through the stator coils to demagnetize the permanent magnets, and then the rotor is removed from the rotating electric machine. In the rotor removal method described in Patent Document 1, the rotor is removed from the rotating electric machine while the permanent magnets are demagnetized and the magnetic force is weak, thus making it easier to remove the rotor from the rotating electric machine and improving the convenience of disassembly.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent No. 5298548 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, in the rotor removal method described in Patent Document 1, when demagnetizing the permanent magnet, if a high-frequency current for heating the permanent magnet and a demagnetizing current for demagnetizing the permanent magnet are flowing through the stator coils, torque may sometimes be generated in the rotor. If torque is generated in the rotor when heating or demagnetizing the permanent magnet, it may place a large load on the device that transmits the rotor's rotational power. Furthermore, in the rotor removal method described in Patent Document 1, an induction heating device capable of flowing high-frequency current needs to be placed near the rotor containing the permanent magnet.

[0012] Therefore, the rotor removal method described in Patent Document 1 has room for improvement in terms of the ease of disassembly of the rotating electric motor and the cost of disassembly of the rotating electric motor.

[0013] This invention provides a method for demagnetizing the permanent magnet of a rotating electric motor, a system for demagnetizing the permanent magnet of a rotating electric motor, and a method for removing the rotor, which can improve the ease of disassembly of a rotating electric motor.

[0014] Methods for solving problems

[0015] The first aspect of the present invention is a method for demagnetizing the permanent magnet of a rotating electric machine, which is used to demagnetize the permanent magnet of a rotating electric machine having a rotor having a permanent magnet and windings into which a power supply is applied, wherein,

[0016] The method for demagnetizing the permanent magnets of the rotary electric motor includes:

[0017] The step of detecting the circumferential position of the rotor; and

[0018] The step of heating the permanent magnet.

[0019] In the step of heating the permanent magnet, based on the circumferential position of the rotor detected in the step of detecting the circumferential position of the rotor, an alternating current is passed into the winding such that the direction of the resultant magnetic field of the winding is aligned with the d-axis of the permanent magnet of the rotor.

[0020] A second aspect of the present invention is a permanent magnet demagnetizing system for a rotating electric motor, comprising:

[0021] A rotating electric motor having a rotor with permanent magnets and windings through which power is supplied;

[0022] A power supply device that provides power to the winding; and

[0023] Control device, which controls the power supply device

[0024] The permanent magnet demagnetization system of the rotary electric machine is used to demagnetize the permanent magnets of the rotary electric machine.

[0025] in,

[0026] The control device detects the circumferential position of the rotor and, based on the detected circumferential position of the rotor, supplies an alternating current to the winding so that the direction of the resultant magnetic field of the winding is aligned with the d-axis of the permanent magnet of the rotor, thereby heating the permanent magnet.

[0027] A third aspect of the invention is a method for removing a rotor from a vehicle, the vehicle comprising: a rotary motor having the rotor having permanent magnets and windings through which power is supplied; a power supply device for supplying power to the windings; a power source connected to the power supply device; and a control device for controlling the power supply device, wherein...

[0028] The method for removing the rotor includes:

[0029] The step of determining whether permanent magnet demagnetization control for demagnetizing the permanent magnet of the rotor is performed in the control device;

[0030] The steps of performing the permanent magnet demagnetization control; and

[0031] The step of removing the rotor from the rotating motor

[0032] The permanent magnet demagnetization control includes the step of: the control device controlling the power supply device to supply alternating current from the power source to the winding via the power supply device, thereby heating the permanent magnet.

[0033] If it is determined that the permanent magnet demagnetization control should be executed, then the step of executing the permanent magnet demagnetization control shall be performed.

[0034] After performing the permanent magnet demagnetization control step, the rotor is removed from the rotating motor.

[0035] Invention Effects

[0036] According to the present invention, the ease of disassembling a rotary electric motor can be improved. Attached Figure Description

[0037] Figure 1 This is a block diagram illustrating a permanent magnet demagnetization system mounted on a vehicle according to one embodiment of the present invention.

[0038] Figure 2 yes Figure 1 A schematic diagram of a rotating motor in a permanent magnet demagnetization system.

[0039] Figure 3 It shows the use of Figure 1 The flowchart illustrates a series of processes by which a permanent magnet demagnetizing system demagnetizes the permanent magnets of a rotor and removes the rotor from a rotating electric motor.

[0040] Figure 4 It is shown in Figure 2 A schematic diagram of a rotating electric motor in which the d-axis of the permanent magnet of the rotor is aligned with the magnetic center line of the U-phase winding when current is applied to the winding.

[0041] Figure 5 It is shown in Figure 2 A schematic diagram of a rotating motor in which the d-axis of the permanent magnet of the rotor is not aligned with the magnetic centerline of the U-phase winding when current is applied to the winding.

[0042] Figure 6 Is Figure 2 A schematic diagram of a rotating electric motor performing permanent magnet heat treatment, and a graph showing the current values ​​flowing in the U-phase winding, V-phase winding and W-phase winding during permanent magnet heat treatment.

[0043] Figure 7 Is Figure 2 A schematic diagram of a rotary motor performing permanent magnet demagnetization.

[0044] Figure 8 It shows that it is mounted on Figure 1 A diagram showing the main components of a vehicle's parking lock mechanism.

[0045] Explanation of reference numerals in the attached figures:

[0046] 1: Permanent magnet demagnetization system

[0047] 20: Rotary motor

[0048] 21: Rotor

[0049] 22: Permanent magnet

[0050] 24: Winding

[0051] 30: Power supply device

[0052] 40: Control device

[0053] 50: Storage battery (power source)

[0054] 70: Parking lock mechanism

[0055] 71: Parking Gear

[0056] V: Vehicle Detailed Implementation

[0057] Hereinafter, one embodiment of the permanent magnet demagnetizing system for a rotating electric machine according to the present invention will be described with reference to the accompanying drawings. Furthermore, the drawings are viewed from the direction indicated by the reference numerals.

[0058] like Figure 1 As shown, in this embodiment, the permanent magnet demagnetizing system 1 of the rotary motor is mounted on the vehicle V. The permanent magnet demagnetizing system 1 includes: a drive unit 10, which has a rotary motor 20 and a power supply unit 30; and a control unit 40, which controls the drive unit 10.

[0059] The vehicle V also includes: a battery 50 that supplies power to the power supply unit 30 of the drive unit 10; and a transmission 60 that changes the rotational power output from the rotary motor 20 of the drive unit 10. The transmission 60 has a parking lock mechanism 70.

[0060] Furthermore, the vehicle V uses the electricity stored in the battery 50 to drive the drive unit 10, and uses the transmission 60 to change the rotational power output from the rotary motor 20 of the drive unit 10 and transmit it from the axle 80 to the wheel WH to drive the wheel WH.

[0061] like Figure 8 As shown, the parking lock mechanism 70 includes a parking gear 71 that rotates integrally with the rotation shaft 61 of the transmission 60 and a parking pawl 72. On the outer circumferential surface of the parking gear 71, recesses 71a and protrusions 71b are alternately formed in the circumferential direction. The parking pawl 72 has a pawl 72a that can engage with the recess 71a of the parking gear 71. The parking pawl 72 can move to a locked position where the pawl 72a engages with the recess 71a of the parking gear 71 and to an unlocked position where the pawl 72a is not engaged with the recess 71a of the parking gear 71. When the parking pawl 72 is in the locked position, the recess 71a of the parking gear 71 engages with the pawl 72a of the parking pawl 72, and the parking lock mechanism 70 is in a parking locked state where the parking gear 71 cannot rotate. When the parking pawl 72 is in the unlocked position, the recess 71a of the parking gear 71 is not engaged with the pawl 72a of the parking pawl 72, and the parking locking mechanism 70 is in the unlocked state where the parking gear 71 can rotate freely. In this way, the parking locking mechanism 70 can switch between the parking locked state where the parking gear 71 cannot rotate and the unlocked state where the parking gear 71 can rotate freely.

[0062] like Figure 2 As shown, the rotary motor 20 includes: a rotor 21 having a permanent magnet 22; and a stator 23 having a winding 24 into which a power supply is supplied.

[0063] In this embodiment, for simplicity and clarity, a three-phase two-pole rotary motor 20 will be described. In this motor 20, the rotor 21 has two poles, and the stator 23 has windings 24 including a U-phase winding 24U, a V-phase winding 24V, and a W-phase winding 24W, which are arranged at equal intervals in the circumferential direction. Therefore, the rotor 21 of this embodiment has a permanent magnet 22 with N and S poles. A permanent magnet with strong magnetic force, such as a neodymium magnet, is used in the permanent magnet 22 of the rotor 21.

[0064] return Figure 1 The power supply device 30 is a device that converts the power stored in the battery 50 and supplies it to the windings 24 of the rotating motor 20. In this embodiment, it is, for example, an inverter device. The power supply device 30 may also have a converter capable of stepping up or down the power stored in the battery 50.

[0065] The control device 40 is an ECU (Electronic Control Unit) that performs comprehensive control of the vehicle V and controls the drive unit 10 and auxiliary equipment of the vehicle V.

[0066] Storage batteries 50 include, for example, lithium-ion batteries, nickel-metal hydride batteries, all-solid-state batteries, and other secondary batteries.

[0067] Next, refer to Figure 3 This describes a series of procedures for demagnetizing the permanent magnet 22 of rotor 21 and removing rotor 21 from rotating motor 20.

[0068] When the vehicle V's control device 40 receives an instruction from the outside to switch to the permanent magnet demagnetization mode, it first executes the permanent magnet demagnetization preparation control. When it is determined in the permanent magnet demagnetization preparation control to execute the permanent magnet demagnetization control, it then executes the permanent magnet demagnetization control.

[0069] <Demagnetization Preparation Control for Permanent Magnets>

[0070] In the demagnetization preparation control of the permanent magnet, the control device 40 first determines whether the speed of vehicle V is zero (step S110). If the speed of vehicle V is not zero, it remains in standby mode until the speed of vehicle V becomes zero (step S110: loop if no).

[0071] When the control device 40 determines in step S110 that the vehicle speed of the vehicle V is zero (step S110: Yes), it proceeds to step S120 to obtain the circumferential position (rotational position) of the rotor 21.

[0072] Next, the control device 40 enters step S130, and based on the circumferential position (rotational position) of the rotor 21 obtained in step S120, determines whether the circumferential position (rotational position) of the rotor 21 is a position where the magnetic permeability distribution is symmetrical with respect to the d-axis of the permanent magnet 22 of the rotor 21 when current is applied to the winding 24.

[0073] like Figure 4 and Figure 5 As shown, in this embodiment, in step S130, whether the circumferential position (rotational position) of the rotor 21 is symmetrical about the magnetic permeability distribution relative to the d-axis of the permanent magnet 22 of the rotor 21 when current is supplied to the winding 24 is determined based on whether the d-axis of the permanent magnet 22 of the rotor 21 is aligned with the magnetic center line LU of the U-phase winding 24U when current is supplied to the winding 24 in the circumferential direction of the rotating motor 20. Specifically, as... Figure 4 As shown, when the d-axis of the permanent magnet 22 of the rotor 21 coincides with the magnetic center line LU of the U-phase winding 24U when current is supplied to the winding 24 in the circumferential direction of the rotating motor 20, it is determined that the circumferential position (rotational position) of the rotor 21 is symmetrical with respect to the d-axis of the permanent magnet 22 of the rotor 21 when current is supplied to the winding 24 (step S130: Yes). Figure 5 As shown, when the d-axis of the permanent magnet 22 of the rotor 21 is not aligned with the magnetic center line LU of the U-phase winding 24U when current is supplied to the winding 24 in the circumferential direction of the rotating motor 20, it is determined that the circumferential position (rotational position) of the rotor 21 is not symmetrical with respect to the d-axis of the permanent magnet 22 of the rotor 21 when current is supplied to the winding 24 (step S130: No). Furthermore, in step S130, whether the circumferential position (rotational position) of the rotor 21 is symmetrical with respect to the d-axis of the permanent magnet 22 of the rotor 21 when current is supplied to the winding 24 can be determined based on whether the d-axis of the permanent magnet 22 of the rotor 21 is aligned with the magnetic center line of the V-phase winding 24V when current is supplied to the winding 24 in the circumferential direction of the rotating motor 20, or whether the d-axis of the permanent magnet 22 of the rotor 21 is aligned with the magnetic center line of the W-phase winding 24W when current is supplied to the winding 24 in the circumferential direction of the rotating motor 20.

[0074] return Figure 3 When the d-axis of the permanent magnet 22 of the rotor 21 is not aligned with the magnetic center line LU of the U-phase winding 24U when current is supplied to the winding 24 (refer to...) Figure 5If the control device 40 determines that the circumferential position (rotational position) of the rotor 21 is not symmetrical with respect to the d-axis of the permanent magnet 22 of the rotor 21 when current is supplied to the winding 24 (step S130: No), it proceeds to step S140. In step S140, the control device 40 controls the power supply device 30 to supply a specified amount of power from the battery 50 to the winding 24, and rotates the rotor 21 such that the d-axis of the permanent magnet 22 of the rotor 21 coincides with the magnetic center line LU of the U-phase winding 24U when current is supplied to the winding 24. Then, it returns to step S130.

[0075] When the d-axis of the permanent magnet 22 of the rotor 21 coincides with the magnetic center line LU of the U-phase winding 24U when current is supplied to the winding 24 in the circumferential direction of the rotating motor 20 (refer to...) Figure 4 If the control device 40 determines that the circumferential position (rotational position) of the rotor 21 is symmetrical with respect to the d-axis of the permanent magnet 22 of the rotor 21 when current is supplied to the winding 24 (step S130: Yes), then proceeds to step S150. In step S150, the control device 40 moves the parking pawl 72 of the parking locking mechanism 70 to a locking position where the pawl 72a engages with the recess 71a of the parking gear 71, thus converting the parking locking mechanism 70 to a parking locked state. Therefore, the circumferential position (rotational position) of the rotor 21 is fixed at a position symmetrical with respect to the d-axis of the permanent magnet 22 of the rotor 21 when current is supplied to the winding 24. Then, the control device 40 proceeds to step S160, determining that permanent magnet demagnetization control should be performed.

[0076] Thus, in the permanent magnet demagnetization preparation control in steps S110 to S150, the control device 40 determines whether to perform permanent magnet demagnetization control. Moreover, when the vehicle speed V is zero and the circumferential position (rotational position) of the rotor 21 is symmetrical about the magnetic permeability distribution relative to the d-axis of the permanent magnet 22 of the rotor 21 when current is supplied to the winding 24, the control device 40 switches the parking lock mechanism 70 to the parking lock state to fix the circumferential position (rotational position) of the rotor 21, and determines that permanent magnet demagnetization control should be performed.

[0077] Then, when the control device 40 determines that permanent magnet demagnetization preparation control is to be executed during the permanent magnet demagnetization preparation control, it ends the permanent magnet demagnetization preparation control and enters the permanent magnet demagnetization control. In the permanent magnet demagnetization control, the permanent magnet 22 of the rotor 21 is demagnetized.

[0078] <Permanent Magnet Demagnetization Control>

[0079] In the demagnetization control of permanent magnets, the control device 40 first performs a heating treatment on the permanent magnets.

[0080] In the permanent magnet heating process, the control device 40 first controls the power supply device 30 to supply a high-order harmonic alternating current from the battery 50 to the winding 24 (step S210). This generates eddy currents in the permanent magnet 22, causing its temperature to rise. In step S210, the control device 40 heats the permanent magnet 22 by supplying a high-order harmonic alternating current from the battery 50 to the winding 24 such that the direction of the resultant magnetic field of the winding 24 is aligned with the d-axis of the permanent magnet 22 of the rotor 21. For example, in step S210, the control device 40 controls the power supply device 30 to supply a 1500 Hz alternating current from the battery 50 to the winding 24.

[0081] Therefore, when the circumferential position of the rotor 21 is such that the magnetic permeability distribution is symmetrical with respect to the d-axis of the permanent magnet 22 of the rotor 21 when current is supplied to the winding 24, the control device 40 performs step S210 to heat the permanent magnet 22.

[0082] In this embodiment, such as Figure 6 As shown, a high-harmonic alternating current is supplied from the battery 50 to the winding 24 in such a manner that the current flowing through the V-phase winding 24V and the W-phase winding 24W is half the magnitude of the current flowing through the U-phase winding 24U and the direction is opposite to the direction of the current flowing through the U-phase winding 24U. For example, in step S210, the control device 40 controls the power supply device 30 to supply a current of 200 Apeak to the U-phase winding 24U and a current of 100 Apeak to the V-phase winding 24V and the W-phase winding 24W. When this high-harmonic alternating current is supplied to the winding 24, the direction of the resultant magnetic field of the winding 24 is aligned with the magnetic center line LU of the U-phase winding 24U. Furthermore, in the circumferential direction of the rotating motor 20, the d-axis of the permanent magnet 22 of the rotor 21 coincides with the magnetic center line LU of the U-phase winding 24U. Therefore, when a high-order harmonic alternating current is supplied from the battery 50 to the winding 24 in a manner where the magnitude of the current flowing through the V-phase winding 24V and the W-phase winding 24W is half that of the current flowing through the U-phase winding 24U and the direction is opposite to that of the current flowing through the U-phase winding 24U, the direction of the resultant magnetic field of the winding 24 is aligned with the d-axis of the permanent magnet 22 of the rotor 21. Therefore, when a high-order harmonic alternating current is supplied from the battery 50 to the winding 24 in a manner where the magnitude of the current flowing through the V-phase winding 24V and the W-phase winding 24W is half that of the current flowing through the U-phase winding 24U and the direction is opposite to that of the current flowing through the U-phase winding 24U, eddy currents are generated in the permanent magnet 22, causing the temperature of the permanent magnet 22 to rise, while almost no torque is generated in the rotor 21.

[0083] In this way, the control device 40 controls the power supply device 30 to supply a high-order harmonic alternating current from the battery 50 to the winding 24, such that the direction of the resultant magnetic field of the winding 24 is aligned with the d-axis of the permanent magnet 22 of the rotor 21, thereby heating the permanent magnet 22. Therefore, when demagnetizing the permanent magnet 22, the generation of torque in the rotor 21 can be suppressed, and the permanent magnet 22 can be heated. As a result, when demagnetizing the permanent magnet 22, it is possible to suppress the excessive load on devices that transmit the rotational power of the rotor 21, such as the parking lock mechanism 70, and to suppress vehicle V movement. Therefore, the ease of disassembly of the rotary motor 20 can be improved.

[0084] Furthermore, when the circumferential position of the rotor 21 is such that the magnetic permeability distribution is symmetrical with respect to the d-axis of the permanent magnet 22 of the rotor 21 when current is supplied to the winding 24, the control device 40 heats the permanent magnet 22 by supplying a high-order harmonic alternating current from the battery 50 to the winding 24 such that the direction of the resultant magnetic field of the winding 24 is aligned with the d-axis of the permanent magnet 22 of the rotor 21. Therefore, in the control device 40, it is possible to facilitate the control of supplying a high-order harmonic alternating current such that the direction of the resultant magnetic field of the winding 24 is aligned with the d-axis of the permanent magnet 22 of the rotor 21.

[0085] Furthermore, when the circumferential position of the rotor 21 is not symmetrical with respect to the d-axis of the permanent magnet 22 of the rotor 21 when current is supplied to the winding 24, the control device 40 controls the power supply device 30 to supply a specified power from the battery 50 to the winding 24, and rotates the rotor 21 in such a way that the d-axis of the permanent magnet 22 of the rotor 21 is aligned with the magnetic center line LU of the U-phase winding 24U when current is supplied to the winding 24. Therefore, even if the circumferential position of the rotor 21 is not symmetrical with respect to the d-axis of the permanent magnet 22 of the rotor 21 when current is supplied to the winding 24, the rotor 21 can be rotated in such a way that the d-axis of the permanent magnet 22 of the rotor 21 is aligned with the magnetic center line LU of the U-phase winding 24U when current is supplied to the winding 24. This makes the circumferential position of the rotor 21 symmetrical with respect to the d-axis of the permanent magnet 22 of the rotor 21 when current is supplied to the winding 24. Furthermore, the permanent magnet 22 is heated by supplying a high-order harmonic alternating current from the battery 50 to the winding 24, such that the direction of the resultant magnetic field of the winding 24 is aligned with the d-axis of the permanent magnet 22 of the rotor 21.

[0086] return Figure 3If step S210 is executed, the control device 40 proceeds to step S220 to determine whether the magnet temperature Tm of the permanent magnet 22 is above the specified temperature Tset. The specified temperature Tset is, for example, 180°C. When the magnet temperature Tm of the permanent magnet 22 is less than the specified temperature Tset (step S220: No), step S210 continues, and a high-order harmonic alternating current is supplied from the battery 50 to the winding 24 to raise the temperature of the permanent magnet 22.

[0087] When the magnet temperature Tm of the permanent magnet 22 reaches or exceeds the specified temperature Tset (step S220: Yes), the control device 40 stops supplying the high-order harmonic alternating current from the battery 50 to the winding 24 (step S230). Thus, the permanent magnet heating treatment ends, and the control device 40 then performs the permanent magnet demagnetization treatment.

[0088] In the permanent magnet demagnetization process, the control device 40 controls the power supply device 30 to supply a large current for a specified time to the winding 24 in such a way that the direction of the resultant magnetic field of the winding 24 is consistent with the d-axis of the permanent magnet 22 of the rotor 21 and the direction is opposite to the direction of the magnetic field of the permanent magnet 22 of the rotor 21 (step S310).

[0089] In this embodiment, the control device 40 controls the power supply device 30 to supply a large demagnetizing current from the battery 50 to the windings 24. This demagnetizing current flows through the U-phase winding 24U in a direction opposite to the magnetic field direction of the permanent magnet 22 of the rotor 21, and through the V-phase winding 24V and the W-phase winding 24W in a direction half the magnitude of the current flowing through the U-phase winding 24U and opposite to the direction of the current flowing through the U-phase winding 24U. The demagnetizing current is a larger current than the high-order harmonic alternating current supplied to the windings 24 in step S210.

[0090] like Figure 7As shown, for example, when the circumferential position (rotational position) of rotor 21 is such that the N pole of the permanent magnet 22 of rotor 21 is opposite to the U-phase winding 24U and the d-axis of the permanent magnet 22 of rotor 21 coincides with the magnetic center line LU of the U-phase winding 24U, in step S310, control device 40 controls power supply device 30 to supply demagnetizing current from battery 50 to winding 24 in such a way that a current of 600 [Arms] flows counterclockwise in U-phase winding 24U when viewed from the center of rotor 21, and a current of 300 [Arms] flows clockwise in V-phase winding 24V and W-phase winding 24W when viewed from the center of rotor 21. When such a large current is supplied to winding 24, the direction of the resultant magnetic field of winding 24 coincides with the magnetic center line LU of U-phase winding 24U, therefore, almost no torque is generated in rotor 21. Furthermore, when such a large current is applied to the winding 24, the direction of the combined magnetic field of the winding 24 is opposite to the direction of the magnetic field of the permanent magnet 22 of the rotor 21. Therefore, the permanent magnet 22 of the rotor 21 is subjected to the combined magnetic field of the winding 24, which is opposite to the direction of the magnetic field of the permanent magnet 22 of the rotor 21, at a temperature above a specified temperature Tset, and demagnetizes.

[0091] Thus, in this embodiment, after step S210 of heating the permanent magnet 22 of the rotor 21, the control device 40 executes step S310 of demagnetizing the permanent magnet 22 of the rotor 21 by passing a demagnetizing current through the winding 24. Therefore, even if the temperature of the permanent magnet 22 is not raised to the temperature at which the required rate of decrease in induced voltage is obtained in step S210 of heating the permanent magnet 22 of the rotor 21, demagnetization of the permanent magnet 22 can still be performed in step S310. Therefore, in step S210 of heating the permanent magnet 22 of the rotor 21, the predetermined temperature Tset can be set to a temperature lower than the temperature at which the required rate of decrease in induced voltage is obtained, enabling more efficient demagnetization of the permanent magnet 22.

[0092] Furthermore, the required rate of reduction of induced voltage is only required to reduce the induced voltage of the permanent magnet 22 to the point that the rotor 21 can be easily removed from the rotating motor 20. The temperature at which the required rate of reduction of induced voltage can be obtained can be lower than the Curie temperature of the permanent magnet 22.

[0093] Furthermore, in step S150, when the circumferential position of the rotor 21 is such that the magnetic permeability distribution when current is supplied to the winding 24 is symmetrical with respect to the d-axis of the permanent magnet 22 of the rotor 21, the control device 40 controls the parking locking mechanism 70 to enter the parking locking state. Therefore, it is possible to supply high-order harmonic alternating current and demagnetizing current to the winding 24 while fixing the circumferential position (rotational position) of the rotor 21 in a position where the magnetic permeability distribution when current is supplied to the winding 24 is symmetrical with respect to the d-axis of the permanent magnet 22 of the rotor 21. Thus, even when the circumferential position (rotational position) of the rotor 21 is fixed such that almost no torque is generated when current is supplied to the winding 24, it is possible to heat and demagnetize the permanent magnet 22 of the rotor 21.

[0094] Return to Figure 3 When the permanent magnet demagnetization control shown in steps S210 to S310 ends, the rotary motor 20 is removed from the vehicle V to remove the rotary motor 20 out of the vehicle V (step S410).

[0095] Then, the rotor 21 is axially slid relative to the stator 23 to remove the rotor 21 from the rotary motor 20 (step S420).

[0096] Thus, rotor 21 is removed from rotary motor 20, and the series of processes ends.

[0097] The permanent magnet 22 of the rotor 21 is a permanent magnet with strong magnetic force, such as a neodymium magnet. Therefore, if the rotor 21 is offset radially when it slides axially relative to the stator 23 without demagnetizing the permanent magnet 22, the rotor 21 will be strongly attached to the stator 23 due to the magnetic force of the permanent magnet 22, making it difficult to slide axially relative to the stator 23 to remove the rotor 21 from the rotating motor 20.

[0098] Therefore, in the past, in order to remove the rotor 21 from the rotating electric motor 20, it was necessary to use a large force to overcome the strong magnetic force of the permanent magnet 22 of the rotor 21 while preventing the rotor 21 from shifting radially, so that the rotor 21 could slide axially relative to the stator 23. Therefore, special tools and special equipment were needed to overcome the strong magnetic force of the permanent magnet 22 of the rotor 21 while preventing the rotor 21 from shifting radially, so that the rotor 21 could slide axially relative to the stator 23. If such special tools and special equipment were not available in a limited location, it would be impossible to remove the rotor 21 from the rotating electric motor 20, resulting in poor disassembly convenience of the rotating electric motor 20 and high disassembly costs.

[0099] On the other hand, in this embodiment, after step S210 of heating the permanent magnet 22 by passing an alternating current of high-order harmonics to the winding 24 and step S310 of demagnetizing the permanent magnet 22 of the rotor 21 by passing a demagnetizing current to the winding 24, step S410 of removing the rotary motor 20 from the vehicle V and step S420 of removing the rotor 21 from the rotary motor 20 are performed.

[0100] Therefore, in the state where the permanent magnet 22 of the rotor 21 is demagnetized, step S420 of removing the rotor 21 from the rotary motor 20 is performed. Thus, the rotor 21 can be axially slid relative to the stator 23 with a small force, and the rotor 21 can be removed from the rotary motor 20 with a small force. Therefore, it is easy to slide the rotor 21 axially relative to the stator 23 while preventing radial displacement of the rotor 21. As a result, the ease of disassembling the rotary motor 20 is improved, and the disassembly cost of the rotary motor 20 can be reduced.

[0101] Furthermore, in this embodiment, in step S210, the control device 40 controls the power supply device 30 to heat the permanent magnet 22 by supplying alternating current from the battery 50 to the winding 24 via the power supply device 30. Therefore, the permanent magnet 22 can be heated while the rotary motor 20 is mounted on the vehicle V. As a result, the permanent magnet 22 can be heated without the need for special equipment for heating the permanent magnet 22, thus improving the ease of disassembly of the rotary motor 20 and reducing the disassembly cost of the rotary motor 20.

[0102] Furthermore, in this embodiment, in step S310, the control device 40 controls the power supply device 30 to supply a demagnetizing current from the battery 50 to the winding 24 via the power supply device 30, thereby demagnetizing the permanent magnet 22. Therefore, the permanent magnet 22 can be demagnetized while the rotary motor 20 is mounted on the vehicle V. Thus, the permanent magnet 22 can be demagnetized without the need for specialized equipment for demagnetizing it, thereby improving the ease of disassembling the rotary motor 20 and reducing the disassembly cost.

[0103] In addition, in this embodiment, after the permanent magnet demagnetization control is performed, in step S410, the rotary motor 20 is removed from the vehicle V, and after step S410, in step S420, the rotor 21 is removed from the rotary motor 20.

[0104] Therefore, the permanent magnet 22 can be demagnetized without the need for a special device for demagnetizing the permanent magnet 22. In addition, by removing the rotor 21 from the rotary motor 20 after removing it from the vehicle V, the rotor 21 can be removed from the rotary motor 20 from outside the vehicle V without the rotary motor 20 being installed in the vehicle V. Therefore, it is easy to remove the rotor 21 from the rotary motor 20.

[0105] Thus, with the permanent magnet demagnetizing system 1 mounted on the vehicle V, the permanent magnet 22 of the rotor 21 of the rotary motor 20 can be heated and demagnetized without the need for additional specialized equipment, even when the rotary motor 20 is mounted on the vehicle V. This improves the ease of disassembly of the rotary motor 20 and reduces its disassembly cost.

[0106] Then, the permanent magnet 22 is removed from the rotor 21 and recycled.

[0107] The present invention has been described above with reference to the accompanying drawings, but the present invention is not limited to this embodiment. Obviously, those skilled in the art will be able to conceive of various modifications or alterations within the scope of the technical solutions described, and these modifications or alterations should also be understood to fall within the technical scope of the present invention. Furthermore, the constituent elements in the above embodiments can be arbitrarily combined without departing from the spirit of the present invention.

[0108] For example, in this embodiment, a three-phase two-pole rotary motor 20 is described. In this motor 20, the rotor 21 has 2 poles, and the stator 23 has a U-phase winding 24U, a V-phase winding 24V, and a W-phase winding 24W. The U-phase winding 24U, V-phase winding 24V, and W-phase winding 24W are arranged at equal intervals in the circumferential direction. However, the number of poles of the rotor 21 can also be 4, 6, 8, 12, etc. (2×n, where n is any natural number). The windings 24 of the stator 23 can correspond to the number of poles of the rotor 21. When the number of poles of the rotor 21 is set to 2×n (where n is any natural number), the windings 24 of the stator 23 have n U-phase windings 24U, n V-phase windings 24V, and n W-phase windings 24W.

[0109] Alternatively, for example, in this embodiment, after performing step S210, the control device 40 performs step S310 to demagnetize the permanent magnet 22 of the rotor 21 by passing a demagnetizing current through the winding 24, but step S310 may be omitted. In this case, preferably, the control device 40 sets the predetermined temperature Tset in step S210 to a temperature above the temperature at which the required rate of decrease in induced voltage can be obtained. Thus, even if step S310 is omitted, the permanent magnet 22 can be demagnetized in step S210 to the point that the rotor 21 can be easily removed from the rotating motor 20.

[0110] Alternatively, for example, in this embodiment, the control device 40 is an ECU (Electronic Control Unit) that performs comprehensive control of the vehicle V, but the control device 40 may also be set separately from the ECU that performs comprehensive control of the vehicle V.

[0111] At least the following items are described in this specification. Examples of corresponding components in the above embodiments are shown in parentheses, but the present invention is not limited thereto.

[0112] (1) A method for demagnetizing the permanent magnet of a rotating electric machine, used to demagnetize the permanent magnet of a rotating electric machine (rotor 20) having a rotor (rotor 21) having a permanent magnet (permanent magnet 22) and a winding (winding 24) into which power is supplied, wherein,

[0113] The method for demagnetizing the permanent magnets of the rotary electric motor includes:

[0114] The step of detecting the circumferential position of the rotor; and

[0115] The step of heating the permanent magnet.

[0116] In the step of heating the permanent magnet, based on the circumferential position of the rotor detected in the step of detecting the circumferential position of the rotor, an alternating current is passed into the winding such that the direction of the resultant magnetic field of the winding is aligned with the d-axis of the permanent magnet of the rotor.

[0117] According to (1), based on the circumferential position of the rotor detected in the step of detecting the circumferential position of the rotor, the permanent magnet is heated by passing an alternating current through the winding so that the direction of the resultant magnetic field of the winding is consistent with the d-axis of the permanent magnet of the rotor. Therefore, when demagnetizing the permanent magnet, the torque generated in the rotor can be suppressed and the permanent magnet can be heated, which can improve the ease of disassembly of the rotating motor.

[0118] (2) The method for demagnetizing the permanent magnet of the rotating electric machine according to (1), wherein,

[0119] The method for demagnetizing the permanent magnet of the rotating electric machine further includes: after heating the permanent magnet, passing a demagnetizing current through the winding to demagnetize the permanent magnet.

[0120] According to (2), by performing a demagnetizing step of passing a demagnetizing current through the winding after heating the permanent magnet, the permanent magnet can be demagnetized by passing a demagnetizing current through the winding even without raising the temperature of the permanent magnet to a temperature at which the required rate of decrease in induced voltage can be obtained. Therefore, in the step of heating the permanent magnet of the rotor, the temperature only needs to be raised to a temperature lower than the temperature at which the required rate of decrease in induced voltage can be obtained, thus enabling more efficient demagnetization of the permanent magnet.

[0121] (3) The method for demagnetizing the permanent magnet of a rotating electric machine according to (1) or (2), wherein,

[0122] The method for demagnetizing the permanent magnet of the rotating electric machine further includes, before the step of heating the permanent magnet, a step of determining whether the circumferential position of the rotor is symmetrical with respect to the d-axis of the permanent magnet of the rotor based on the circumferential position of the rotor detected in the step of detecting the circumferential position of the rotor.

[0123] When the circumferential position of the rotor is such that the magnetic permeability distribution is symmetrical with respect to the d-axis of the permanent magnet of the rotor when current is applied to the winding, the step of heating the permanent magnet is performed.

[0124] According to (3), when the circumferential position of the rotor is such that the magnetic permeability distribution is symmetrical with respect to the d-axis of the permanent magnet of the rotor when current is applied to the winding, the step of heating the permanent magnet is performed. Therefore, it is possible to facilitate the control of the current that is applied so that the direction of the combined magnetic field of the winding is consistent with the d-axis of the permanent magnet of the rotor.

[0125] (4) The method for demagnetizing the permanent magnet of the rotating electric machine according to (3), wherein

[0126] The method for demagnetizing the permanent magnet of the rotating electric motor further includes the step of rotating the rotor so that, when the circumferential position of the rotor is not symmetrical with respect to the d-axis of the permanent magnet of the rotor when the magnetic permeability distribution is symmetrical with respect to the d-axis of the permanent magnet of the rotor, the circumferential position of the rotor becomes symmetrical with respect to the d-axis of the permanent magnet of the rotor when the current is supplied to the winding.

[0127] According to (4), it also includes the step of rotating the rotor so that the circumferential position of the rotor is not symmetrical with respect to the d-axis of the permanent magnet of the rotor when the magnetic permeability distribution of the rotor is symmetrical with respect to the d-axis of the permanent magnet of the rotor when the current is supplied to the winding. Therefore, even if the circumferential position of the rotor is not symmetrical with respect to the d-axis of the permanent magnet of the rotor when the current is supplied to the winding, the rotor can be rotated so that the circumferential position of the rotor is symmetrical with respect to the d-axis of the permanent magnet of the rotor when the current is supplied to the winding, and the permanent magnet is heated by supplying a high-order harmonic alternating current to the winding so that the direction of the resultant magnetic field of the winding is consistent with the d-axis of the permanent magnet of the rotor.

[0128] (5) A permanent magnet demagnetizing system for a rotating electric machine (permanent magnet demagnetizing system 1), comprising:

[0129] A rotary electric machine (rotary electric machine 20) has a rotor (rotor 21) with a permanent magnet (permanent magnet 22) and a winding (winding 24) through which power is supplied.

[0130] Power supply device (power supply device 30) that provides power to the winding; and

[0131] Control device (control device 40), which controls the power supply device,

[0132] The permanent magnet demagnetization system of the rotary electric machine is used to demagnetize the permanent magnets of the rotary electric machine.

[0133] in,

[0134] The control device detects the circumferential position of the rotor and, based on the detected circumferential position of the rotor, supplies an alternating current to the winding so that the direction of the resultant magnetic field of the winding is aligned with the d-axis of the permanent magnet of the rotor, thereby heating the permanent magnet.

[0135] According to (5), the control device heats the permanent magnet by passing an alternating current through the winding so that the direction of the combined magnetic field of the winding is consistent with the d-axis of the permanent magnet of the rotor, based on the detected circumferential position of the rotor. Therefore, when demagnetizing the permanent magnet, it can suppress the generation of torque in the rotor and heat the permanent magnet, thereby improving the ease of disassembly of the rotating motor.

[0136] (6) The permanent magnet demagnetization system for the rotating electric machine according to (5), wherein,

[0137] After heating the permanent magnet, the control device controls the power supply device to supply a demagnetizing current to the winding, thereby demagnetizing the permanent magnet.

[0138] According to (6), after heating the permanent magnet, the control device controls the power supply device to supply a demagnetizing current to the winding, thereby demagnetizing the permanent magnet. Therefore, when heating the permanent magnet, even without raising its temperature to a temperature that yields the required rate of decrease in induced voltage, a demagnetizing current can be supplied to the winding to demagnetize the permanent magnet. Thus, when heating the permanent magnet of the rotor, the temperature only needs to be raised to a temperature lower than the temperature at which the required rate of decrease in induced voltage is obtained, thereby demagnetizing the permanent magnet more efficiently.

[0139] (7) The permanent magnet demagnetization system for a rotating electric machine according to (5) or (6), wherein,

[0140] Based on the detected circumferential position of the rotor, the control device determines whether the circumferential position of the rotor is symmetrical with respect to the d-axis of the permanent magnet of the rotor when current is applied to the winding; and

[0141] When the circumferential position of the rotor is such that the magnetic permeability distribution is symmetrical with respect to the d-axis of the permanent magnet of the rotor when current is supplied to the winding, the control device controls the power supply device to supply an alternating current to the winding so that the direction of the resultant magnetic field of the winding is consistent with the d-axis of the permanent magnet of the rotor, thereby heating the permanent magnet.

[0142] According to (7), when the circumferential position of the rotor is such that the magnetic permeability distribution is symmetrical with respect to the d-axis of the permanent magnet of the rotor when current is supplied to the winding, heating the permanent magnet makes it easy to control the supply of alternating current to the winding so that the direction of the combined magnetic field of the winding is consistent with the d-axis of the permanent magnet of the rotor.

[0143] (8) The permanent magnet demagnetization system for the rotating electric machine according to (7), wherein,

[0144] When the circumferential position of the rotor is not symmetrical with respect to the d-axis of the permanent magnet of the rotor when current is supplied to the winding, the control device controls the power supply device to rotate the rotor so that the circumferential position of the rotor is symmetrical with respect to the d-axis of the permanent magnet of the rotor when current is supplied to the winding.

[0145] According to (8), when the circumferential position of the rotor is not symmetrical with respect to the d-axis of the permanent magnet of the rotor when current is supplied to the winding, the rotor is rotated so that the circumferential position of the rotor becomes symmetrical with respect to the d-axis of the permanent magnet of the rotor when current is supplied to the winding. Therefore, even when the circumferential position of the rotor is not symmetrical with respect to the d-axis of the permanent magnet of the rotor when current is supplied to the winding, the rotor can be rotated so that the circumferential position of the rotor becomes symmetrical with respect to the d-axis of the permanent magnet of the rotor when current is supplied to the winding. Furthermore, the permanent magnet is heated by supplying a high-order harmonic alternating current to the winding so that the direction of the resultant magnetic field of the winding is consistent with the d-axis of the permanent magnet of the rotor.

[0146] (9) A permanent magnet demagnetizing system for a rotating electrical machine according to any one of (5) to (8), wherein,

[0147] The permanent magnet demagnetization system is mounted on the vehicle (vehicle V).

[0148] According to (9), the permanent magnet demagnetization system is mounted on the vehicle. Therefore, when the rotary motor is mounted on the vehicle, the permanent magnets of the rotor of the rotary motor can be heated and demagnetized without the need for additional special equipment. As a result, the ease of disassembling the rotary motor is improved, and the disassembly cost of the rotary motor can be reduced.

[0149] (10) The permanent magnet demagnetization system for the rotating electric machine according to (9), wherein,

[0150] The vehicle is equipped with a parking lock mechanism (parking lock mechanism 70) having a parking gear (parking gear 71).

[0151] The parking locking mechanism can switch between a parking locked state where the parking gear cannot rotate and an unlocked state where the parking gear can rotate freely.

[0152] When the circumferential position of the rotor is such that the magnetic permeability distribution is symmetrical with respect to the d-axis of the permanent magnet of the rotor, the control device controls the parking locking mechanism to enter the parking locking state.

[0153] According to (10), when the circumferential position of the rotor is such that the magnetic permeability distribution when current is applied to the winding is symmetrical with respect to the d-axis of the rotor's permanent magnet, controlling the parking lock mechanism to enter the parking lock state allows alternating current and demagnetizing current to be applied to the winding while the circumferential position of the rotor is fixed in a position where the magnetic permeability distribution when current is applied to the winding is symmetrical with respect to the d-axis of the rotor's permanent magnet. Thus, the circumferential position of the rotor can be fixed in a state where almost no torque is generated in the rotor even when current is applied to the winding, thereby heating and demagnetizing the rotor's permanent magnet.

[0154] (11) A method for removing a rotor from a vehicle (vehicle V), the vehicle comprising: a rotary motor (rotor motor 20) having the rotor (rotor 21) having a permanent magnet (permanent magnet 22) and a winding (winding 24) through which power is supplied; a power supply device (power supply device 30) supplying power to the winding; a power source (battery 50) connected to the power supply device; and a control device (control device 40) controlling the power supply device.

[0155] in,

[0156] The method for removing the rotor includes:

[0157] The control device determines whether to perform a permanent magnet demagnetization control step to demagnetize the permanent magnet of the rotor;

[0158] The steps of performing the permanent magnet demagnetization control; and

[0159] The step of removing the rotor from the rotating motor

[0160] The permanent magnet demagnetization control includes the step of: the control device controlling the power supply device to supply alternating current from the power source to the winding via the power supply device, thereby heating the permanent magnet.

[0161] If it is determined that the permanent magnet demagnetization control should be executed, then the step of executing the permanent magnet demagnetization control shall be performed.

[0162] After performing the permanent magnet demagnetization control step, the rotor is removed from the rotating motor.

[0163] According to (11), the control device of the vehicle controls the power supply device to supply alternating current from the battery to the windings through the power supply device, thereby heating the permanent magnet. Therefore, the permanent magnet can be heated while the rotating motor is mounted on the vehicle. As a result, the permanent magnet can be heated without the need for special equipment for heating the permanent magnet, thus improving the ease of disassembly of the rotating motor and reducing the disassembly cost of the rotating motor.

[0164] (12) The rotor removal method according to (11), wherein,

[0165] The permanent magnet demagnetization control further includes: after heating the permanent magnet, the control device controls the power supply device to supply a demagnetizing current from the power source to the winding, thereby demagnetizing the permanent magnet.

[0166] After performing the permanent magnet demagnetization control step, the rotor is removed from the rotating motor.

[0167] According to (12), after the steps of heating the permanent magnet and demagnetizing the permanent magnet, the step of removing the rotor from the rotating motor is performed, so the rotor can be removed from the rotating motor with less force. Therefore, it is easy to make the rotor slide axially relative to the stator while preventing radial displacement of the rotor, thus improving the ease of disassembly of the rotating motor and reducing the disassembly cost of the rotating motor.

[0168] Furthermore, the vehicle's control device controls the power supply to supply a demagnetizing current to the windings via the power supply device, thereby demagnetizing the permanent magnets. Therefore, the permanent magnets can be demagnetized while the rotating motor is mounted on the vehicle. This eliminates the need for specialized equipment for demagnetizing permanent magnets, thus improving the ease of disassembly of the rotating motor and reducing disassembly costs.

[0169] Furthermore, after the steps of heating the permanent magnet and demagnetizing it by passing a demagnetizing current through the winding, the rotor is removed from the rotating machine. Therefore, in the step of heating the permanent magnet, even if the temperature of the permanent magnet is not raised to a temperature at which the required rate of decrease in induced voltage is obtained, the permanent magnet can still be demagnetized by passing a demagnetizing current through the winding. Thus, in the step of heating the permanent magnet of the rotor, the temperature only needs to be raised to a temperature lower than the temperature at which the required rate of decrease in induced voltage is obtained, thereby demagnetizing the permanent magnet more efficiently.

[0170] (13) The method for removing the rotor according to (11) or (12), wherein,

[0171] The method for removing the rotor further includes the step of removing the rotary motor from the vehicle.

[0172] After performing the permanent magnet demagnetization control step, the rotary motor is removed from the vehicle.

[0173] After the step of removing the rotary motor from the vehicle, the step of removing the rotor from the rotary motor is performed.

[0174] According to (13), permanent magnets can be demagnetized without the need for special equipment for demagnetizing permanent magnets. In addition, the rotor can be removed from the rotating motor after it is removed from the vehicle, so it is not necessary to remove the rotor from the rotating motor while it is installed in the vehicle. The rotor can be removed from the rotating motor from outside the vehicle, so it is easy to remove the rotor from the rotating motor.

Claims

1. A permanent magnet demagnetization method of a rotary electric machine for demagnetizing a permanent magnet of a rotary electric machine having a rotor having the permanent magnet and a winding through which a current is passed, wherein the permanent magnet demagnetization method of the rotary electric machine comprises: a step of detecting a circumferential position of the rotor; and a step of heating the permanent magnet, the permanent magnet demagnetization method of the rotary electric machine further comprising: a step of determining, before the step of heating the permanent magnet, whether the circumferential position of the rotor is a position at which a magnetic permeability distribution when the current is passed through the winding is symmetrical with respect to a d-axis of the permanent magnet of the rotor, on the basis of the circumferential position of the rotor detected in the step of detecting the circumferential position of the rotor, the step of heating the permanent magnet being performed in a case where the circumferential position of the rotor is the position at which the magnetic permeability distribution when the current is passed through the winding is symmetrical with respect to the d-axis of the permanent magnet of the rotor, in the step of heating the permanent magnet, an alternating current is passed through the winding such that a direction of a resultant magnetic field of the winding coincides with the d-axis of the permanent magnet of the rotor, on the basis of the circumferential position of the rotor detected in the step of detecting the circumferential position of the rotor.

2. The permanent magnet demagnetization method of the rotary electric machine according to claim 1, wherein the permanent magnet demagnetization method of the rotary electric machine further comprises: a step of passing a demagnetizing current through the winding to demagnetize the permanent magnet, after the step of heating the permanent magnet.

3. The permanent magnet demagnetization method of the rotary electric machine according to claim 1 or 2, wherein the permanent magnet demagnetization method of the rotary electric machine further comprises: a step of rotating the rotor such that the circumferential position of the rotor becomes the position at which the magnetic permeability distribution when the current is passed through the winding is symmetrical with respect to the d-axis of the permanent magnet of the rotor, in a case where the circumferential position of the rotor is not the position at which the magnetic permeability distribution when the current is passed through the winding is symmetrical with respect to the d-axis of the permanent magnet of the rotor.

4. A permanent magnet demagnetization system of a rotary electric machine, comprising: a rotary electric machine having a rotor having a permanent magnet and a winding through which a current is passed; a power supply device that supplies electric power to the winding; and a control device that controls the power supply device, the permanent magnet demagnetization system being for demagnetizing the permanent magnet of the rotary electric machine, wherein the control device detects a circumferential position of the rotor, and determines whether the circumferential position of the rotor is a position at which a magnetic permeability distribution when the current is passed through the winding is symmetrical with respect to a d-axis of the permanent magnet of the rotor, on the basis of the detected circumferential position of the rotor, and controls the power supply device to pass an alternating current through the winding such that a direction of a resultant magnetic field of the winding coincides with the d-axis of the permanent magnet of the rotor, thereby heating the permanent magnet, in a case where the circumferential position of the rotor is the position at which the magnetic permeability distribution when the current is passed through the winding is symmetrical with respect to the d-axis of the permanent magnet of the rotor. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 5. The permanent magnet demagnetization system of a rotary electric machine according to claim 4, wherein the control device controls the power supply device to pass a demagnetizing current to the winding after heating the permanent magnet.

6. The permanent magnet demagnetization system of a rotary electric machine according to claim 4 or 5, wherein the control device controls the power supply device to rotate the rotor so that the circumferential position of the rotor becomes a position at which the magnetic permeability distribution when a current is passed to the winding is symmetrical with respect to the d-axis of the permanent magnet of the rotor, in a case where the circumferential position of the rotor is not the position at which the magnetic permeability distribution when a current is passed to the winding is symmetrical with respect to the d-axis of the permanent magnet of the rotor.

7. The permanent magnet demagnetization system of a rotary electric machine according to claim 4 or 5, wherein the permanent magnet demagnetization system is mounted on a vehicle.

8. A permanent magnet demagnetization system of a rotary electric machine, wherein the permanent magnet demagnetization system of a rotary electric machine comprises: a rotary electric machine including a rotor having a permanent magnet and a winding through which a current is passed; a power supply device that supplies electric power to the winding; and a control device that controls the power supply device, the permanent magnet demagnetization system of a rotary electric machine is used to demagnetize the permanent magnet of the rotary electric machine, wherein the permanent magnet demagnetization system is mounted on a vehicle, the vehicle includes a parking lock mechanism including a parking gear, the parking lock mechanism is capable of switching between a parking lock state in which the parking gear cannot rotate and an unlock state in which the parking gear can freely rotate, the control device detects the circumferential position of the rotor, and based on the detected circumferential position of the rotor, passes an alternating current to the winding so that the direction of the resultant magnetic field of the winding coincides with the d-axis of the permanent magnet of the rotor, thereby heating the permanent magnet, and in a case where the circumferential position of the rotor is a position at which the magnetic permeability distribution when a current is passed to the winding is symmetrical with respect to the d-axis of the permanent magnet of the rotor, controls the parking lock mechanism so that the parking lock mechanism becomes the parking lock state.

9. A method of removing a rotor from a vehicle, the vehicle having: an electric rotating machine having the rotor with a permanent magnet and a winding through which a current is passed; a power supply device that supplies electric power to the winding; and a power source connected to the power supply device. and a control device that controls the power supply device, wherein the method of extracting the rotor includes: a step of determining in the control device whether to perform permanent magnet demagnetization control for demagnetizing the permanent magnet of the rotor; a step of performing the permanent magnet demagnetization control; and a step of extracting the rotor from the rotary electric machine, the step of determining whether to perform the permanent magnet demagnetization control includes: a step of detecting the circumferential position of the rotor; a step of determining, before the step of performing the permanent magnet demagnetization control, whether the circumferential position of the rotor is a position at which the magnetic permeability distribution when a current is passed to the winding is symmetrical with respect to the d-axis of the permanent magnet of the rotor, based on the circumferential position of the rotor detected in the step of detecting the circumferential position of the rotor; and a step of controlling the power supply device to pass an alternating current to the winding so that the direction of the resultant magnetic field of the winding coincides with the d-axis of the permanent magnet of the rotor, thereby heating the permanent magnet, in a case where the circumferential position of the rotor is the position at which the magnetic permeability distribution when a current is passed to the winding is symmetrical with respect to the d-axis of the permanent magnet of the rotor. the step of determining that the permanent magnet demagnetization control is executed, the permanent magnet demagnetization control includes the step of the control device controlling the power supply device to pass an alternating current from the power supply to the winding via the power supply device, thereby heating the permanent magnet, the step of executing the permanent magnet demagnetization control is executed when it is determined that the permanent magnet demagnetization control is executed, the step of taking out the rotor from the rotary electric machine is executed after the step of executing the permanent magnet demagnetization control.

10. The rotor taking-out method according to claim 9, wherein the permanent magnet demagnetization control further includes the step of the control device controlling the power supply device to pass a demagnetization current from the power supply to the winding via the power supply device, thereby demagnetizing the permanent magnet, after the step of heating the permanent magnet, the step of taking out the rotor from the rotary electric machine is executed after the step of executing the permanent magnet demagnetization control.

11. The rotor taking-out method according to claim 9 or 10, wherein the rotor taking-out method further includes the step of taking out the rotary electric machine from the vehicle, the step of taking out the rotary electric machine from the vehicle is executed after the step of executing the permanent magnet demagnetization control, the step of taking out the rotor from the rotary electric machine is executed after the step of taking out the rotary electric machine from the vehicle.

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