Demagnetizing device and demagnetizing method

Abstract

A demagnetizing device (10) demagnetizes a permanent magnet built in an electric motor (200). A demagnetization device (10) is provided with: an application circuit (12) that applies a high-frequency voltage to a winding of a motor (200); and a temperature rise control unit (114) that controls the high-frequency voltage applied to the winding by the application circuit (12) so that the temperature of the permanent magnet (232) is equal to or higher than a predetermined temperature at which the permanent magnet is demagnetized. The temperature rise control unit (114) controls the high-frequency voltage applied to the winding so as to maximize the d-axis current component of the current flowing through the winding.

Description

Technical Field

[0001] The invention relates to a demagnetization device and a demagnetization method for demagnetizing a permanent magnet of a motor. Background Art

[0002] In recent years, measures to significantly reduce waste generation have been actively developed through the prevention, reduction, recycling and reuse of waste. In order to achieve this measure, it is known that there is a technology that dismantles the motor mounted on electric vehicles, etc. by crushing, etc., and recovers and regenerates the rare metals contained in the motor. As such a technology, the following device is known, when dismantling the motor, a voltage is applied to the motor before dismantling, and the permanent magnet is heated and demagnetized so that the fragments of the permanent magnet will not adhere to the dismantling device and other crushed iron filings (for example, refer to Patent Document 1).

[0003] However, when the method of demagnetizing a motor by applying voltage to the motor as in the device described in Patent Document 1 is applied to demagnetizing a motor of an automobile, in order to suppress the movement of the vehicle caused by unexpected motor rotation, it is necessary to restrain or lift the vehicle with a jack, which is dangerous for the operator and makes it difficult to achieve efficient demagnetization work.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent document 1: Patent publication No. 3835126. Summary of the invention

[0007] A demagnetization device according to one technical solution of the present invention is a demagnetization device for demagnetizing a permanent magnet built into a motor, and includes: an application circuit that applies a high-frequency voltage to a winding of the motor; and a temperature increase control unit that controls the high-frequency voltage applied to the winding via the application circuit so that the temperature of the permanent magnet reaches a predetermined temperature or higher at which the permanent magnet is demagnetized. The temperature increase control unit controls the high-frequency voltage applied to the winding so that the d-axis current component of the current flowing through the winding is maximized.

[0008] A demagnetization method according to another technical solution of the present invention is a demagnetization method for demagnetizing a permanent magnet built into a motor, comprising: an application step, in which a high-frequency voltage is applied to a winding of the motor while the motor is mounted on a system; and a temperature increase control step, in which the high-frequency voltage applied to the winding in the application step is controlled so that the temperature of the permanent magnet reaches a predetermined temperature or higher at which the permanent magnet is demagnetized. In the temperature increase control step, the high-frequency voltage applied to the winding is controlled so that the d-axis current component of the current flowing through the winding is maximized. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The objects, features and advantages of the present invention will be further clarified through the following description of the embodiments in conjunction with the accompanying drawings.

[0010] Figure 1A This is a cross-sectional view perpendicular to the axis showing the structure of the main part of the permanent magnet synchronous motor.

[0011] Figure 1B yes Figure 1A An enlarged view of the main part.

[0012] Figure 2 This is a block diagram schematically showing a main part configuration of a demagnetization device according to an embodiment of the present invention.

[0013] Figure 3 It is schematically shown Figure 2 A block diagram of an example of the main part configuration of an ECU.

[0014] Figure 4 This is a diagram for explaining the relationship between the number of times current higher harmonics are superimposed and the magnetic loss.

[0015] Figure 5 It is shown by Figure 3 A flowchart of an example of a process executed by the ECU.

[0016] Figure 6 It is shown by Figure 3 A flowchart of another example of a process performed by the ECU.

[0017] Figure 7 It is a diagram for explaining the operation of the demagnetization device according to the embodiment of the present invention. DETAILED DESCRIPTION

[0018] Refer to the following Figure 1A to Figure 7 The demagnetization device of the embodiment of the present invention demagnetizes permanent magnets included in a permanent magnet synchronous motor used as a motor or generator for driving a hybrid vehicle or electric vehicle. Hereinafter, the permanent magnet synchronous motor is simply referred to as a motor.

[0019] Figure 1A 1 is a cross-sectional view perpendicular to the axis CL0 showing the main structure of the motor. Figure 1A As shown, the electric motor 200 includes a rotor 201 that rotates around an axis CL0 and a stator 202 that is arranged to surround an outer peripheral surface 201 a of the rotor 201 .

[0020] The rotor 201 has a rotor core 210 having a substantially annular shape centered on the axis CL0 and a plurality of magnetic pole portions 230 formed on the rotor core 210 along the circumferential direction of the rotor core 210. For example, a rotor shaft (not shown) constituting the output shaft of the motor 200 is engaged with the inner peripheral surface 210a of the rotor core 210, and the rotor 201 rotates integrally with the rotor shaft. The outer peripheral surface 201a of the rotor 201 corresponds to the outer peripheral surface of the rotor core 210. The rotor core 210 is formed by stacking a plurality of electromagnetic steel plates made of metal as a magnetic body in the axial direction.

[0021] A plurality of magnetic pole portions 230 are arranged at equal intervals along the circumferential direction. Figure 1A In the example of FIG. 1 , eight magnetic pole portions 230 are provided in units of 45°. Each magnetic pole portion 230 has a plurality of (three in the figure) magnet receiving holes 231 formed in the rotor core 210 and permanent magnets 232 received in the magnet receiving holes 231. A single or a plurality of permanent magnets 232 can be received in each magnet receiving hole 231.

[0022] Note that in this embodiment, an axis extending radially at the circumferential center of magnetic pole portion 230 , that is, in the direction of the magnetic flux generated by permanent magnet 232 , is defined as a d-axis, and an axis spaced 90 degrees apart in electrical angle from the d-axis is defined as a q-axis.

[0023] The stator 202 includes a stator core 220 of a substantially annular shape centered on the axis CL0 and arranged at a predetermined interval in the radial direction from the outer peripheral surface 201a of the rotor 201, and a coil 221 mounted on the stator core 220. The stator core 220 is formed by stacking a plurality of electromagnetic steel plates made of metal as a magnetic body. A plurality of teeth 222 are provided on the inner peripheral surface of the stator core 220 so as to protrude radially inward in the circumferential direction, and slots are formed between adjacent teeth 222. The coil 221 is composed of a winding wound around the teeth 222.

[0024] When current flows through coil 221, a magnetic field is generated in stator 202. By the interaction of this magnetic field with the magnetic field generated by permanent magnets 232 of magnetic pole portions 230 of rotor 201, rotor 201 rotates.

[0025] Figure 1B yes Figure 1A , which is an enlarged view of the main part, is a diagram showing the structure of a single magnetic pole portion 230. Figure 1B As shown, the three magnet receiving holes 231 in the magnetic pole portion 230 are symmetrically arranged with respect to the d axis. The three permanent magnets 232 are respectively received in the magnet receiving holes 231. The permanent magnets 232 are of the same shape, which correspond to the shapes of the magnet receiving holes 231, respectively, and the cross-section observed from the axial direction is roughly rectangular, and is formed into a flat plate extending in the axial direction. The permanent magnets 232 can use various magnets such as neodymium magnets or ferrite magnets.

[0026] The permanent magnet 232 is configured as a whole to be symmetrical relative to the center line CL1 extending in the thickness direction (short side direction) through the center of its width direction (long side direction). The three permanent magnets 232 are all magnetized in the thickness direction. For example, the outer side surface (the side surface on the outer peripheral surface 201a side) of the permanent magnet 232 is magnetized to the N pole, and the inner side surface (the side surface on the inner peripheral surface 210a side) is magnetized to the S pole. The dotted arrows in the figure schematically show the magnetization direction of each of the three permanent magnets 232. It should be noted that the magnetization directions of the circumferentially adjacent magnetic pole portions 230 are opposite.

[0027] A magnetic flux barrier 233 is formed in the magnet receiving hole 231. The magnetic flux barrier 233 is an air layer and has a greater magnetic resistance than the rotor core 210. By providing the magnetic flux barrier 233, it is possible to suppress magnetic short circuiting of the magnetic flux generated by the permanent magnet 232 on the rotor side. The magnetic flux barrier 233 may be filled with a resin having a lower magnetic permeability than the rotor core 210, and the magnetic flux barrier 233 may be made into a resin layer.

[0028] However, when the permanent magnet 232 built into the motor 200 is demagnetized, an alternating current is passed through the stator core 220 of the motor 200 to generate a magnetic field fluctuation, and a current is induced inside the rotor 201. When this current (eddy current) flows inside the rotor 201, Joule heat is generated due to the internal resistance of the rotor 201, and the permanent magnet 232 built into the rotor 201 is heated.

[0029] On the other hand, when an alternating current flows through the stator core 220, the rotor core 210 rotates. Therefore, in the above-mentioned demagnetization method, when demagnetization is performed in a state where the motor 200 is mounted on a vehicle, the drive wheels of the vehicle may rotate. Therefore, in order to prevent the vehicle from moving forward or backward, it is necessary to perform operations such as lifting with a jack or disassembling the wheels, and restraining the rotor core 210 in advance. Therefore, in order to cope with such a problem, in this embodiment, a demagnetization device is configured as follows.

[0030] Figure 2 1 is a block diagram schematically showing the main structure of the demagnetization device according to the embodiment of the present invention. The demagnetization device 10 includes an electronic control unit (ECU) 100, an inverter circuit (hereinafter also referred to as an AC current application circuit or simply an application circuit) 12, a capacitor 11, a current detector 13, a rotor position detector 14, a voltage detector 15, and a communication unit 16. The battery BT is a high-voltage battery used as a driving battery for hybrid vehicles and electric vehicles. Figure 3 As shown, the positive (plus) and negative (minus) output terminals of the battery BT are connected to the inverter circuit 12 via the capacitor 11. The communication unit 16 can communicate with an external device via a network (a wireless communication network and a wired communication network) not shown.

[0031] The current detector 13 detects the current flowing to the motor 200. Specifically, the current detector 13 obtains the current values ​​IU, IV, and IW of the U phase, V phase, and W phase, respectively. Since the sum of the current values ​​(instantaneous values) of each phase is 0, the current detector 13 first detects the current of two phases (at the time of the current sensor) among the three phases obtained by the current sensor (not shown). Figure 2 The detection values ​​(analog values) of the U phase, the V phase, and the W phase in the example are analog-to-digital converted to obtain the current values ​​(digital values) of the above two phases. Then, the current value of the remaining 1 phase is calculated based on the current values ​​of the above two phases. The current detector 13 outputs the obtained current values ​​IU, IV, and IW of each phase to the ECU 100. It should be noted that the current detector 13 can also perform analog-to-digital conversion on the detection values ​​of the U phase, the V phase, and the W phase obtained by the current sensor to obtain the current values ​​of each phase respectively. The voltage detector 15 detects the DC voltage between the positive and negative terminals of the capacitor 11.

[0032] The rotor position detector 14 detects the rotation angle θ of the rotating shaft of the motor 200. Specifically, the rotor position detector 14 performs analog-to-digital conversion on the sensor value of the angular displacement sensor that detects the rotation displacement of the rotating shaft of the motor 200 to obtain the rotation angle θ. The angular displacement sensor is, for example, a resolver, a magnetic encoder, or an optical encoder. The rotor position detector 14 outputs the obtained rotation angle θ to the ECU 100.

[0033] The inverter circuit 12 converts the DC current supplied from the battery BT into AC current and outputs it to the motor 200. The inverter circuit 12 has three groups of upper and lower switching elements 121 (121U, 121V, 121W, 121X, 121Y, 121Z). The switching element 121 includes an IGBT (Integrated Gate Bipolar Transistor) and a thyristor connected in parallel therewith. It should be noted that the structure of the switching element 121 is not limited to this. The inverter circuit 12 switches the switching element 121 on and off according to the control signals GU, GV, GW, GX, GY, GZ from the ECU 100. As a result, the DC current supplied from the battery BT via the capacitor 11 is converted into AC current and output to the motor 200.

[0034] Figure 3 It is schematically shown Figure 2 A block diagram of an example of the main structure of ECU 100. Figure 3As shown in FIG. 1 , the ECU 100 includes a computer including a computing unit 110 such as a CPU (central processing unit), a storage unit 120 such as a ROM (read only memory) and a RAM (random access memory), and other peripheral circuits. The current detector 13, the rotor position detector 14, the voltage detector 15, and the communication unit 16 are connected to the ECU 100, respectively. The storage unit 120 stores various information processed by the computing unit 110. In addition, the storage unit 120 stores an identifier of the motor 200.

[0035] The ECU 100 includes a destruction command input unit 111, a rotor position acquisition unit 112, a current value acquisition unit 113, and a demagnetization control unit 114 as a calculation unit 110 ( Figure 3 ) undertakes the functional structure.

[0036] The destruction command input unit 111 inputs a destruction command (hereinafter also referred to as a demagnetization command) from a diagnostic machine described later via the communication unit 16 .

[0037] When the destruction instruction input unit 111 receives the destruction instruction for the motor 200, that is, when the destruction of the motor 200 is allowed, it reports the start of demagnetization of the permanent magnet 232. Specifically, the destruction instruction input unit 111 outputs a sounding instruction to the control ECU (not shown) of the vehicle via the communication unit 16, so that the alarm (not shown) of the vehicle equipped with the motor 200 sounds a predetermined number of times (for example, once). It should be noted that the report of the start of demagnetization can also be performed by outputting information (display information, sound information) indicating the start of demagnetization to an output device (display, speaker, etc.) of the vehicle equipped with the motor 200.

[0038] The rotor position acquisition unit 112 acquires the rotation angle θ output from the rotor position detector 14. The current value acquisition unit 113 acquires the current values ​​IU, IV, and IW output from the current detector 13.

[0039] When the destruction of the motor 200 is permitted by the destruction command input unit 111, the demagnetization control unit 114 starts demagnetization of the permanent magnet 232. Specifically, the demagnetization control unit 114 controls the inverter circuit 12 to flow an alternating current to the stator core 220 of the motor 200, and heats the permanent magnet 232 built into the rotor 201 so that the permanent magnet 232 reaches a predetermined temperature or higher. The predetermined temperature is a temperature at which the permanent magnet 232 is demagnetized.

[0040] Here, the control of the inverter circuit 12 by the demagnetization control unit 114 is described. First, the demagnetization control unit 114 performs phase conversion (phase conversion from three phases to two phases) on the current values ​​(current values ​​of the three-phase stationary coordinate system) IU, IV, and IW obtained by the current value acquisition unit 113, and calculates the current value of the two-phase stationary coordinate system. The demagnetization control unit 114 performs a rotating coordinate conversion on the calculated current value of the two-phase stationary coordinate system according to the rotation angle θ included in the rotation position information obtained by the rotor position acquisition unit 112, and calculates the current value (d-axis current value and q-axis current value) of the dq rotating coordinate system. In this way, the d-axis current value and the q-axis current value applied to the motor 200 are calculated. It should be noted that the d-axis current is a current component that generates magnetic flux. This magnetic flux acts as a countermagnetic force to the magnetic force of the permanent magnet 232 of the rotor 201. The q-axis current is a current component corresponding to the rotation torque of the rotor 201.

[0041] Next, the demagnetization control unit 114 determines the command value of the d-axis current (hereinafter referred to as the d-axis current command value) and the command value of the q-axis current (hereinafter referred to as the q-axis current command value). The demagnetization control unit 114 sets the d-axis current command value so that the d-axis current value is maximized, and sets the q-axis current command value so that the rotor 201 does not rotate even when the motor 200 vibrates or slightly moves due to the d-axis current, that is, so that the rotation speed returns to zero. At this time, the demagnetization control unit 114 performs a high-order harmonic superimposed current addition process on the d-axis current command value so that the high-order harmonics are superimposed on the d-axis current.

[0042] Next, the demagnetization control unit 114 calculates the voltage values ​​Vd and Vq to be applied to the d-axis and q-axis of the motor 200 in such a manner that the difference between the d-axis current command value and the d-axis current value and the difference between the q-axis current command value and the q-axis current value become smaller, respectively. It should be noted that feedback control such as PID control is used in the calculation of the voltage values ​​Vd and Vq. It should be noted that feedforward control may also be used instead of feedback control. The demagnetization control unit 114 performs coordinate conversion and phase conversion (phase conversion from two phases to three phases) on the calculated voltage values ​​Vd and Vq from a rotating coordinate system to a stationary coordinate system, and converts the voltage values ​​Vd and Vq into voltage values ​​VU, VV, and VW of three phases (U, V, and W phases).

[0043] Figure 4 This is a diagram for explaining the relationship between the number of times current higher harmonics are superimposed and the magnetic loss. Figure 4 The simulation results of the magnet loss (Joule loss) [W] per unit time of the motor 200 when a high-order harmonic superimposed current is applied to the motor are shown. Figure 4The graphs of FIG. 1 and FIG. 2 respectively depict the simulation results of the magnet loss when the 5th to 9th harmonics are superimposed on the AC voltage applied to the motor 200, that is, when the 5th to 9th harmonics are superimposed on the AC current flowing through the motor 200. The frequency of the nth harmonic is the frequency of the fundamental wave × n. Figure 4 As shown, the higher the number of superposition of current harmonics, that is, the greater the frequency of current harmonics, the greater the magnet loss. In addition, when magnet loss exceeds a specified level, the permanent magnet 232 in the rotor 201 is heated, and then demagnetized by the demagnetization field, and finally demagnetized. Considering the relationship between the number of superposition of current harmonics and magnet loss, the demagnetization control unit 114 superimposes, for example, 5th or higher harmonics on the d-axis current command value.

[0044] Finally, the demagnetization control unit 114 generates control signals (pulse width modulation signals) GU, GV, GW, GX, GY, GZ corresponding to the voltage values ​​VU, VV, VW superimposed with harmonics using space vector modulation. The switching element 121 of the inverter circuit 12 is turned on / off controlled according to the control signal.

[0045] When a predetermined time has passed since the demagnetization of the permanent magnet 232 has started, the demagnetization control unit 114 generates a control signal to disconnect the switch element 121 and outputs it to the inverter circuit 12, thereby stopping the application of the alternating current to the stator core 220 of the motor 200. It should be noted that the method of stopping the application of the alternating current is not limited to this. When the application of the alternating current is stopped, the demagnetization (heating) of the permanent magnet 232 is completed. It should be noted that for each model (vehicle) equipped with the motor 200, a variable (a table value relative to the external temperature) suitable for the optimal demagnetization time is stored in a storage unit (EEP-ROM) not shown in the figure of the motor 200, and the demagnetization control unit 114 reads the variable from the storage unit to determine the above-mentioned predetermined time. In determining the above-mentioned predetermined time, simulation and experimental values ​​are used. In addition, the demagnetization time can also be corrected by calculation based on an experimental statistical model or a physical model, using the external air temperature at the start of demagnetization and the thermistor temperature at the stator end (the temperature detected by a thermistor not shown at the end of the stator 202).

[0046] Figure 5 It is shown by Figure 3 A flowchart of an example of a process executed by ECU 100. Figure 5 The process is shown until ECU 100 starts demagnetization based on a command to destroy electric motor 200 from the diagnostic machine. Figure 5 The processing shown is repeatedly performed at a predetermined cycle during the startup of the demagnetization device 10 .

[0047] First, in step S11, it is determined whether a destruction command for the motor 200 is input from a diagnostic machine described later via the communication unit 16. When step S11 is negative (S11: No), the process ends. When step S11 is positive (S11: Yes), in step S12, it is reported that the demagnetization of the permanent magnet 232 has started, and in step S13, the demagnetization of the permanent magnet 232 starts. Specifically, the control of the inverter circuit 12 starts.

[0048] Figure 6 It is shown by Figure 3 A flowchart of another example of the processing executed by ECU 100. Figure 6 The flowchart shows the process from the start of demagnetization to the end of demagnetization by the ECU 100 . Figure 6 The processing shown is repeatedly performed at a predetermined cycle after the demagnetization device 10 starts demagnetization.

[0049] First, in step S21, it is determined whether a predetermined time has passed since the start of demagnetization. When step S21 is negative (S21: No), the process ends. When step S21 is positive (S21: Yes), demagnetization ends in step S22. In step S23, the management information stored in the management server is updated. Specifically, the information indicating that demagnetization of the permanent magnet 232 of the motor 200 is completed is recorded in association with the VIN (vehicle identification number) of the vehicle equipped with the motor 200.

[0050] The operation of the demagnetization device of this embodiment is summarized as follows. Figure 7 It is a diagram for explaining the operation of the demagnetization device. Figure 7 The figure shows the situation when the motor 200 is mounted on the vehicle EV and the user, specifically a designated maintenance company (dealer) or a person engaged in the automobile dismantling industry, demagnetizes the motor 200. The PDU (power drive unit) 300 supplies power from the battery BT to the motor 200 to drive the motor 200. The PDU 300 includes an inverter circuit, an ECU, and a capacitor. The motor 200 supplies the power energy obtained by converting the supplied power from the PDU (power drive unit) 300 to the power transmission mechanism 400 including a gear box, a differential, etc. In this way, the motor 200, the PDU 300, and the power transmission mechanism 400 function as a drive system 500 that drives the front wheels or rear wheels of the vehicle EV using the power supplied from the motor 200. It should be noted that the demagnetization device 10 constitutes a part of the PDU 300.

[0051] When deciding to replace or discard the motor 200, the user first submits a destruction request for the motor 200 through a communication terminal TM such as a personal computer. The user is, for example, a repairman or a seller who performs maintenance on a vehicle EV equipped with the motor 200. The destruction request is made by sending the user's identifier (user ID), password, and the identifier of the motor 200 to be destroyed to the management server MS of the merchant who manages the motor 200 (for example, the manufacturer of the vehicle). The management server MS has a storage unit (not shown), and the user ID and password received from the communication terminal TM are registered in association with the identifier of the motor 200 in the management table stored in the storage unit.

[0052] When the user demagnetizes the permanent magnet 232 of the motor 200, the user first connects the diagnostic machine OB to the PDU 300 (demagnetization device 10). When the drive system 500 is mounted on the vehicle, the user connects the diagnostic machine OB to a diagnostic connector such as a DLC (data link coupler) provided on the vehicle through a dedicated cable. The communication unit 16 of the demagnetization device 10 can transmit and receive data with the diagnostic machine OB through CAN (Controller Area Network) communication via a dedicated cable. It should be noted that the connection method and communication method between the demagnetization device 10 and the diagnostic machine OB are not limited to this. Next, the user inputs a user ID and a password and an identifier of the motor 200 through the operation unit KP of the diagnostic machine OB. The diagnostic machine OB sends the information input by the user to the management server MS as authentication information. It should be noted that when the identification information of the motor 200 is stored in the demagnetization device 10, the vehicle EV's onboard ECU, etc. (not shown), the diagnostic machine OB can also communicate with them to obtain the identification information of the motor 200 and send it to the management server MS. The management server MS performs user authentication based on the information received from the diagnostic machine OB. Specifically, the management server MS determines whether the user ID and password received from the diagnostic machine OB are associated with the identifier of the motor 200 and registered in the management table. When registered in the management table, the management server MS allows the user to destroy the motor 200. Specifically, a signal indicating that destruction is allowed (hereinafter referred to as the permission signal) is sent to the diagnostic machine OB. On the other hand, when it is not registered in the management table, the management server MS prohibits the user from destroying the motor 200. Specifically, a signal indicating that destruction is prohibited (hereinafter referred to as the prohibition signal) is sent to the diagnostic machine OB.

[0053] When the diagnostic machine OB receives a permission signal from the management server MS, it sends a destruction instruction to the demagnetization device 10. On the other hand, when a prohibition signal is received from the management server MS, the diagnostic machine OB does not send a destruction instruction, but outputs a display message indicating that it is not destructible to the display LD and the speaker (not shown). It should be noted that the sound information indicating that it is not destructible can also be output to the speaker (not shown).

[0054] The following effects can be achieved by adopting the embodiments of the present invention.

[0055] (1) The demagnetization device 10 demagnetizes the permanent magnet 232 built into the motor 200 which is a permanent magnet synchronous motor. The demagnetization device 10 includes: an inverter circuit 12 which applies a high-frequency voltage to the winding of the motor 200; and a demagnetization control unit 114 which controls the high-frequency voltage applied to the winding of the motor 200 via the inverter circuit 12 so that the temperature of the permanent magnet 232 reaches or exceeds a predetermined temperature at which the permanent magnet 232 is demagnetized. The demagnetization control unit 114 controls the high-frequency voltage applied to the winding of the motor 200 so that the d-axis current component of the current flowing through the winding of the motor 200 is maximized. In addition, the demagnetization control unit 114 controls the high-frequency voltage applied to the winding so that the rotation speed of the motor 200 caused by the d-axis current component is returned to zero by using the q-axis current component of the current flowing through the winding. Furthermore, the demagnetization control unit 114 superimposes higher harmonics on the high-frequency voltage applied to the winding of the motor 200 so that a high-frequency current having a frequency higher than a predetermined frequency flows through the winding of the motor 200. Thus, even when the motor 200 is mounted on a vehicle, the permanent magnets 232 can be demagnetized without rotating the rotor 201. Therefore, there is no need to perform work for restraining the rotor 201, and the permanent magnets built into the motor can be effectively demagnetized.

[0056] In addition, in the above embodiment, the management server MS performs user authentication based on the information received from the diagnostic machine OB, and when the user authentication is permitted, the diagnostic machine OB sends a destruction instruction to the demagnetization device 10 ( Figure 7). However, the diagnostic machine OB may send a destruction instruction and authentication information (user ID and password and the identifier of the motor 200) to the demagnetization device 10 according to the user operation, and the demagnetization device 10 performs user authentication according to the received authentication information and determines whether to allow the destruction instruction of the motor 200 from the user. Specifically, the operation unit 110 may also function as an instruction input unit that inputs the destruction instruction from the user via the communication unit 16 and an authentication unit that determines whether to allow the demagnetization of the permanent magnet 232 according to the authentication information of the user attached to the destruction instruction input to the instruction input unit. In this case, the authentication unit accesses the management table of the management server MS and determines whether the user ID and password received from the diagnostic machine OB and the identifier of the motor 200 are associated with the management table of the management server MS and are registered. When there is registration, the authentication unit allows the user to destroy the motor 200. On the other hand, when there is no registration, the authentication unit prohibits the user from destroying the motor 200. When the authentication unit allows the demagnetization of the permanent magnet 232, the demagnetization control unit 114 starts to apply a high-frequency voltage to the winding of the motor 200 via the inverter circuit 12. Thus, even when the diagnostic machine OB does not have a user authentication function, user authentication can be performed on the demagnetization device 10 side, and damage to the motor 200 by a third party via the diagnostic machine OB can be suppressed.

[0057] In addition, in the above-mentioned embodiment, the demagnetization control unit 114 as the temperature increase control unit controls the inverter circuit 12 to flow the AC current to the stator core 220 of the motor 200, demagnetizes (heats) the permanent magnet 232 built into the rotor 201, and ends the demagnetization when a predetermined time has passed since the start of the demagnetization. However, the temperature increase control unit may end the demagnetization when the permanent magnet 232 reaches the Curie temperature or above. For example, when a temperature detector (thermistor, etc.) is installed on the winding of the stator core 220, the temperature increase control unit can determine whether the permanent magnet 232 has reached the Curie temperature or above based on the temperature detected by the detector.

[0058] In addition, in the above embodiment, an example is shown in which the user demagnetizes the motor 200 while the motor 200 is mounted on the vehicle EV. Figure 7 As shown, the motor 200, PDU 300 and power transmission mechanism 400 are integrated as a drive system 500. When the drive system 500 can be removed from the vehicle EV, the user can also send a destruction command of the motor 200 to the drive system 500 removed from the vehicle EV via the diagnostic machine OB. In this way, the motor 200 can be demagnetized using the drive system 500 alone.

[0059] In addition, in the above embodiment, an example is shown in which the capacitor 11 is directly connected to the positive and negative terminals of the battery BT ( Figure 2), but a boost circuit may be provided between the positive and negative terminals of the battery BT and the capacitor 11. For example, when the detection value of the voltage detector 15 (the voltage value between the positive and negative terminals of the capacitor 11) is less than a predetermined value, the demagnetization control unit 114 may determine that the desired power supply cannot be obtained from the battery BT, and operate the boost circuit.

[0060] The present invention is a demagnetization method for demagnetizing a permanent magnet 232 built into a motor 200, including an application step of applying a high-frequency voltage to a winding of the motor 200 mounted on the system and a temperature increase control step of controlling the high-frequency voltage applied to the winding in the application step so that the temperature of the permanent magnet 232 reaches a predetermined temperature above which the permanent magnet 232 is demagnetized. More specifically, the present invention can be used as a demagnetization method in which the high-frequency voltage applied to the winding of the motor 200 is controlled in the temperature increase control step so that the d-axis current component of the current flowing through the winding of the motor 200 is maximized. The above-mentioned system is, for example, a vehicle drive system that drives the front wheels or rear wheels or both the front wheels and rear wheels of the vehicle using power supplied from the motor 200.

[0061] The above description is only an example, and the present invention is not limited to the above embodiments and modifications as long as the features of the present invention are not impaired. One or more of the above embodiments and modifications may be arbitrarily combined, and modifications may be combined with each other.

[0062] By adopting the present invention, the permanent magnet can be effectively demagnetized.

[0063] The present invention has been described above in conjunction with preferred embodiments, and it should be understood by those skilled in the art that various modifications and changes can be made without departing from the scope of the disclosure of the claims set forth below.

Claims

1. A demagnetization device, a demagnetization device (10) for demagnetizing a permanent magnet (232) built into an electric motor (200), characterized in that: have: an application circuit (12) that applies a high-frequency voltage to a winding of the motor (200); and A temperature increase control unit (114) controls the high frequency voltage applied to the winding via the application circuit (12) so that the temperature of the permanent magnet (232) reaches a temperature above a predetermined temperature at which the permanent magnet (232) is demagnetized. The temperature increase control unit (114) controls the high-frequency voltage applied to the winding so as to maximize the d-axis current component of the current flowing through the winding.

2. The demagnetization device according to claim 1, characterized in that: The temperature increase control unit (114) controls the high frequency voltage applied to the winding so as to return the rotation speed of the motor (200) generated by the d-axis current component to zero by using the q-axis current component of the current flowing through the winding.

3. The demagnetization device according to claim 1, characterized in that: The temperature increase control unit (114) superimposes higher harmonics on the high-frequency voltage applied to the winding so that a high-frequency current having a frequency higher than a predetermined frequency flows through the winding.

4. The demagnetization device according to any one of claims 1 to 3, characterized in that: Also includes: an instruction input unit (111) for inputting a demagnetization instruction from a user; and an authentication unit that determines whether to allow demagnetization of the permanent magnet (232) based on an identifier of the user attached to the demagnetization command input into the command input unit (111); When demagnetization of the permanent magnet is permitted by the authentication unit, the temperature increase control unit (114) starts applying the high-frequency voltage to the winding through the application circuit (12).

5. A demagnetization method for demagnetizing a permanent magnet (232) built into an electric motor (200), characterized in that: include: an applying step, in which a high-frequency voltage is applied to a winding of the motor (200) while the motor (200) is mounted on the system; and a temperature increase control step, in which the high frequency voltage applied to the winding in the applying step is controlled so that the temperature of the permanent magnet (232) reaches or exceeds a predetermined temperature at which the permanent magnet (232) is demagnetized, In the temperature increase control step, the high frequency voltage applied to the winding is controlled so that a d-axis current component of a current flowing through the winding is maximized.

6. The demagnetization method according to claim 5, characterized in that: In the temperature increase control step, the high frequency voltage applied to the winding is controlled so that the rotation speed of the motor (200) caused by the d-axis current component is returned to zero by using the q-axis current component of the current flowing through the winding.

7. The demagnetization method according to claim 5 or 6, characterized in that: The system is a driving system (500) of the vehicle that drives the front wheels or the rear wheels or the front wheels and the rear wheels of the vehicle using the power supplied from the electric motor (200).

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