JP2001346364A - Demagnetization device, disassembling device for product having permanent magnet, demagnetization method and disassembling method for product having permanent magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a time and a labor which are necessary when a product such as a motor, etc., which has a permanent magnet is disassembled by a disassembling device because magnet bits are stuck to the respective parts of the disassembling device and smashed iron scraps and the magnet bits must be removed and to improve the recycle efficiency which is deteriorated significantly by the magnet bits stuck to the smashed scraps to be recycled. SOLUTION: A high frequency voltage is applied between at least two terminals of windings of a motor having a permanent magnet to demagnetize the permanent magnet. Further, demagnetization units which demagnetize the permanent magnets are provided at various positions of a disassembling device to demagnetize magnet bits.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a demagnetization apparatus and a demagnetization method for demagnetizing a permanent magnet of a motor such as a compressor, and a disassembly apparatus and a disassembly method of a product having a permanent magnet.

[0002]

2. Description of the Related Art Conventionally, products having permanent magnets, such as motors and compressors, were crushed by a dismantling device (crushing machine) without demagnetizing the permanent magnets while maintaining the magnetic force of the permanent magnets. Later, the magnet part was separated from the other parts.

As a method of demagnetizing a product such as a motor having a permanent magnet, the temperature of the product is set to the Curie temperature of the permanent magnet (a temperature at which the permanent magnet loses its magnetic force, ie, about 400 ° C.).
It is known to demagnetize a permanent magnet by raising the temperature to above (high temperature above). To raise the temperature of a product such as a motor, it is put in a furnace or the like to raise the temperature and demagnetize.

[0004]

Conventionally, as described above, when a product using a permanent magnet such as a motor or a compressor is crushed by a dismantling device, crushed pieces of the permanent magnet are provided at each part of the dismantling device (crushing machine). They adhered and had an adverse effect on the dismantling device, causing failure and deterioration. In particular, there are cases where the debris does not come out of the demolition device or crusher, and adheres to the various parts of the demolition device (such as the blades of the crushing unit and the storage part) and the crushed iron chips. Then, the magnet pieces attached to each part of the apparatus must be removed, which requires a great deal of labor and time. Further, even when the magnet pieces coming out of the dismantling device or the crusher are sorted, there is a problem that the magnet pieces attached to the iron scrap are collected in the same place as the iron scrap, so that the quality of the iron is deteriorated.

In the case of a product having a permanent magnet such as a motor, the permanent magnet of the product is preferably demagnetized before being crushed, but the Curie temperature of the entire product (about 460 ° C. for a ferrite magnet, In the method of demagnetizing by heating at or above 320 ° C. for an Nd—Fe—B sintered magnet, large capacity heating equipment such as a large furnace is required to raise the temperature of the product, and the equipment cost is also high. It was expensive and spent a lot of energy. Therefore, the cost for recycling is up
Had become. When the motor is housed in a closed container such as a compressor, the motor may be taken out of the closed container of the compressor and the motor itself may be heated. It had to be dismantled, for example, by cutting it, which required a great deal of time, cost and labor.

[0006] Further, in the case where a permanent magnet type motor such as a compressor is incorporated and commercialized, there may be a temperature constraint condition for parts other than the motor, and the temperature of the entire product is raised to the Curie temperature during recycling. There is a problem that is not always allowed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to reduce the cost of recycling a product having a permanent magnet. Another object of the present invention is to improve the recycling rate when recycling products having permanent magnets. Also,
An object of the present invention is to provide a method for demagnetizing a product having a permanent magnet, such as a motor or a compressor, with simple equipment. Also,
It is an object to provide equipment capable of heating only a motor when demagnetizing. It is another object of the present invention to provide a method and a demagnetizing apparatus for demagnetizing a product having a permanent magnet with a simple structure. It is another object of the present invention to provide a dismantling method and a dismantling apparatus for demagnetizing and dismantling a product having a permanent magnet with a simple structure. Another object of the present invention is to prevent crushed magnet pieces from adhering to a dismantling device or a crushing device during dismantling or crushing.

[0008]

Means for Solving the Problems The present invention has been made to solve the above-mentioned problems, and the invention according to claim 1 has a high-frequency power supply for generating a high-frequency voltage and a high-frequency voltage generated from the high-frequency power supply. Voltage applying means applied between at least two terminals of a winding of a motor having a permanent magnet, and control for controlling at least one of the magnitude of the voltage applied by the voltage applying means, the voltage frequency, and the voltage application time Means for heating the motor by applying a voltage controlled by the control means to demagnetize the permanent magnet.

According to a second aspect of the present invention, there is provided a compressor having a sealed terminal provided in a container for energizing a permanent magnet type motor housed in the container, and a container provided between at least two of the sealed terminals. A voltage application means for applying a high-frequency voltage from outside of the apparatus, and control means for controlling at least one of the magnitude of the voltage applied by the voltage application means, the frequency of the voltage, and the voltage application time. The motor is heated by applying a controlled voltage to demagnetize the permanent magnet.

The invention according to claim 3 is provided with variable frequency control means for varying the frequency of the applied voltage.

Further, the invention according to claim 4 includes temperature detecting means for detecting the temperature of the motor, and when the temperature of the motor detected by the temperature detecting means reaches a preset temperature, the application of the voltage is performed. It is designed to stop.

According to a fifth aspect of the present invention, there is provided a resistance detecting means for detecting a resistance value of a winding of a motor, and a temperature estimating means for estimating a motor temperature based on the resistance value detected by the resistance detecting means. Wherein the application of the voltage is stopped when the temperature of the motor estimated by the temperature estimating means becomes equal to or higher than a preset temperature.

According to a sixth aspect of the present invention, a crushing section for crushing a product having a permanent magnet and a crushed piece having a permanent magnet attached to the crushing section are heated to reduce the permanent magnet of the crushed piece thermally. A demagnetization unit that performs at least one of thermal demagnetization to magnetize or electric demagnetization of applying a magnetic field to a crushed piece having a permanent magnet attached to the crushed part to electrically demagnetize the permanent magnet of the crushed piece; , Is provided.

According to a seventh aspect of the present invention, there is provided a crushing section for crushing a product having a permanent magnet, an outlet for discharging crushed pieces crushed by the crushing section, and a crushed piece discharged from the outlet. A demagnetizing part for heating a crushed piece having a permanent magnet attached or contained in the containing part and thermally demagnetizing the permanent magnet of the crushed piece or a permanent magnet attached or contained in the containing part And at least one of an electric demagnetizing unit that applies a magnetic field to the crushed pieces and electrically demagnetizes the permanent magnets of the crushed pieces.

The invention according to an eighth aspect of the present invention is directed to a method for reducing the time that a magnetic field is applied to a crushed piece of a permanent magnet attached to a crushing section by applying an AC voltage that attenuates with time to the housing or a coil provided near the housing. It has a magnetic part.

According to a ninth aspect of the present invention, the accommodating portion for accommodating the crushed pieces crushed by the crushing portion is made of a non-magnetic material.

According to a tenth aspect of the present invention, there is provided a method for applying a magnetic field to a crushed piece of a permanent magnet attached to a crushing part by applying an alternating voltage which attenuates with time to the crushing part or a coil provided near the crushing part. It has a magnetic part.

The invention according to claim 11 is a high frequency voltage applying step for applying a high frequency voltage between at least two terminals of a winding of a motor having a permanent magnet, and a high frequency voltage applying step applies the high frequency voltage to the motor. And heating the motor by heating the motor until the permanent magnet of the motor is demagnetized.

According to a twelfth aspect of the present invention, there is provided a voltage applying step for applying a high-frequency voltage from outside the container to a sealed terminal provided in the container to energize a winding of a permanent magnet type motor housed in the container. A heating step of heating the motor inside the container by applying a voltage to the sealed terminal in the voltage applying step, a resistance detecting step of detecting a resistance value of the motor winding heated by the heating step, and a resistance detecting step Temperature estimating step of estimating the temperature of the motor from the resistance value of the winding detected in,
The application time of the high-frequency voltage is controlled based on the temperature estimated in the temperature estimation step.

According to a thirteenth aspect of the present invention, there is provided a charging step of charging a product having a permanent magnet, a crushing step of crushing the product charged in the charging step, and discharging crushed pieces crushed in the crushing step. A discharging step and a housing step for housing the crushed pieces discharged by the discharging step, and a heating step of heating the crushed pieces after the crushing step and demagnetizing the permanent magnet of the crushed pieces or applying a magnetic field to the crushed pieces. And at least one of the magnetic field applying steps for demagnetizing the permanent magnets of the crushed pieces.

The invention according to claim 14 further comprises a voltage application step of applying an AC voltage that attenuates with time to a coil provided in the dismantling device, and crushing is performed by applying a voltage to the coil in the voltage application step. A magnetic field is applied to the piece to demagnetize the permanent magnet.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Figure 1 shows a typical 3
It is sectional drawing which shows an example of the structure of the motor which has a phase 4 pole permanent magnet. In the figure, reference numeral 1 denotes a cylindrical stator core provided with a plurality of slots 2a, 2b, 2c, 2d, 2e, 2f extending in the axial direction on the inner peripheral surface, and the slots 2a, 2b, 2c, 2d, 2e, The teeth 3a, 3b, 3c, 3d, 3e,
3f is formed. 4 is the teeth 3a, 3b, 3
The windings are directly wound around c, 3d, 3e and 3f. Reference numeral 5 denotes a stator having the stator core 1 and the coil 4.

Reference numeral 6 denotes a rotor shaft which is arranged on the axis of the stator 5 and is rotatable with respect to the stator 5, reference numeral 7 denotes a rotor core fixed to the rotor shaft 6, and reference numeral 8 denotes a plurality of rotor cores which are fixed to the outer peripheral surface of the rotor core 7. These permanent magnets 8 are composed mainly of ferrite or neodymium, and are magnetized and arranged so that N poles and S poles are alternately arranged in the circumferential direction. In addition, even when the rotor is driven at high speed, the permanent magnet 8 is not scattered by centrifugal force.
An SUS cylindrical holding ring 19 and the like are fixed to the outer periphery of the permanent magnet 8 by press fitting or shrink fitting. Reference numeral 9 denotes a rotor shaft 6, a rotor core 7, a permanent magnet 8, and a retaining ring 1.
9, and a gap 10 is provided between the rotor 9 and the stator 5.

FIG. 2 is a wiring diagram of the coil as viewed from the inner diameter side of the motor. In this embodiment, the windings are U-phase and V-phase.
It is composed of three phases, that is, a phase and a W phase, and a concentrated winding is provided so as to form a three-phase Y connection. FIGS. 3, 4, and 5
FIG. 3 is a cross-sectional view of another example of a rotor having a permanent magnet, and is a cross-sectional view of a rotor with embedded magnets. In the figure, 6 is a rotor shaft, 7 is a rotor core formed by punching out electromagnetic steel sheets of about 0.3 to 0.5 mm, 70 is a rivet for caulking the laminated electromagnetic steel sheets of the rotor core 7 in the axial direction, and 8 is a rotor core. 7 is a permanent magnet embedded inside.

Reference numeral 9 denotes a rotor having a rotor shaft 6, a rotor core 7 and a permanent magnet 8, which is fixed to the rotor core 7 by press fitting without having the holding ring 19 as described in FIG. These rotor structures may have various other structures depending on the shape and arrangement of the permanent magnet.
In any case, if the rotor structure is of the magnet embedded type,
In the case of FIG. 1, the surface of the rotor 9 is made of a stainless steel plate (SU).
In FIGS. 3, 4, and 5, the case of S) is an electromagnetic steel plate, and each is configured to be a material having good electrical conductivity (good conductivity).

Next, a method of demagnetizing a permanent magnet of a motor having a permanent magnet will be described with reference to FIGS. 6, 7 and 8. FIG. FIG. 6 is a cross-sectional view of a compressor including a motor having a permanent magnet according to the first embodiment. As shown in FIG. 6, a compressor 12 used in a room air conditioner, a refrigerator, and the like.
The stator 5 is fixed to the inner wall of the closed container 13 by shrink fitting or press fitting. Reference numeral 14 denotes a glass terminal (sealed terminal) provided on the closed casing 12, which is connected to the winding 4 of the stator 5 inside the closed casing 12, and enables electricity to be supplied to the winding 4 of the stator 5 from outside. . Further, the rotor 9 is fixed and integrated with the rotor shaft 6 by shrink fitting or press fitting. The rotor shaft 6 has bearing portions 15A, 15A.
B and the like.

FIG. 7 is a connection diagram when a voltage is applied to a three-phase Y-connected motor to perform demagnetization, and FIG. 8 is a diagram illustrating an example of a voltage waveform to be applied. In FIG. 7, 1
1 is a single-phase power supply, 111 is control means for controlling the magnitude, frequency, application time, and the like of the applied voltage to predetermined values, 11A and 11B are connection terminals of the power supply 11, and 16 is the winding of the stator 5. A U-phase terminal, 17 is a V-phase terminal, and 18 is a W-phase terminal. The stator of the present embodiment is Y-connected as shown in the figure. In FIG. 8, the horizontal axis represents the applied time, and the vertical axis represents the magnitude of the applied voltage.

Here, in order to demagnetize the permanent magnet of the motor having the permanent magnet provided in the compressor, first, the U-phase terminal 16 is connected to the terminal 11 A of the single-phase power supply 11,
Phase terminal and the W-phase terminal are connected to the other terminal 11 of the power supply 11.
Connect to B. Next, each terminal 11 of the motor is
A, 11B, several kHz to several hundred kHz as shown in FIG.
A high frequency voltage of about several hundred volts is applied. As a result, an induced current flows through an iron portion such as a SUS holding ring or an electromagnetic steel plate on the surface of the rotor 9 to generate Joule heat and generate heat on the surface of the rotor. This heat is transmitted from the rotor surface to the permanent magnet and heats the permanent magnet, and the temperature of the permanent magnet reaches the Curie temperature to demagnetize the permanent magnet. After the permanent magnet is demagnetized in this way, the motor is crushed in a state where it is incorporated in the compressor and recycled. At this time, the rotor is in a restrained state and does not rotate.

Here, the magnitude, frequency, application time and the like of the voltage applied to the motor are optimally controlled by the control means 111. The magnitude, frequency, application time, and the like of the voltage applied to the motor may be determined in advance through experimentation or the like and input to the control unit 111 after obtaining the optimal values.

FIG. 9 shows an embodiment of a motor having a permanent magnet used other than the compressor. FIG. 9 is another sectional view of a motor having a permanent magnet according to the present embodiment. In the figure, the same parts as those in FIG. As shown in FIG. 9, in the present embodiment, there is no conductive metal holding member 19 for holding the permanent magnet 8 on the surface of the rotor 9 as shown in FIG. In such a rotor, the permanent magnet 8 is fixed to the rotor core 7 with an adhesive or a screw.

In such a rotor having no holding member 19 for the permanent magnet 8, the conductivity varies depending on the material of the permanent magnet. In the case of an iron-based permanent magnet, the conductivity is good. An induced current flows and the permanent magnet of the rotor can be heated by Joule heat. However, in the case of ferrite-based permanent magnets, the conductivity is poor and there is no material with good conductivity on the rotor surface.
By applying a high-frequency voltage having a frequency of about several tens of MHz, which is higher than several kHz to several hundred kHz, each molecule constituting the permanent magnet is in the order of tens of millions of times per second due to the electric field effect of high-frequency energy. The permanent magnet generates heat by intense motion such as rotation, collision, vibration, friction, etc.
The temperature of the permanent magnet rises to the Curie temperature or higher, and the magnet can be thermally demagnetized.

When different rotor structures are mixed, for example, with and without a magnet holding ring, the control means 111 is provided with a variable frequency control unit capable of continuously varying the frequency, so The frequency of the voltage
The frequency may be varied in a range from Hz to several tens of MHz.
Here, FIG. 10 shows an example of the applied voltage waveform when the frequency of the voltage applied to the motor is made variable. In the figure, the horizontal axis represents the application time, and the vertical axis represents the magnitude of the applied voltage. As shown in the figure, the frequency of the applied voltage changes continuously with time. here,
The frequency continuously changes with time from several kHz to several tens MHz. By applying a voltage having a frequency that changes continuously with time, the rotor temperature can be raised to a temperature at which the permanent magnet can be demagnetized, regardless of the rotor structure as described above. The permanent magnet can be securely demagnetized. At this time, the insulating paper of the motor may be burned out due to the rise in the temperature of the rotor, but this does not cause any problem during recycling.

As described above, by applying a high-frequency voltage between the predetermined terminals of the winding 4 of the stator 5, the motor 1 is not taken out of the sealed container 13 of the compressor 12,
The permanent magnet can be easily demagnetized with only one simple facility. Further, at the time of crushing, it is possible to prevent the crushing machine from being broken or deteriorated due to crushed pieces having permanent magnets adhering to the blades of the crushing machine or various parts of the crushing device.

It should be noted that in the present embodiment, four slots are used for six slots.
Although a motor having a concentrated winding of poles has been described as an example, the combination of the number of slots and the number of poles can be applied to all motors.
Further, in the present embodiment, the concentrated winding in which the winding is wound directly on the teeth has been described as an example, but the same effect can be obtained by using a distributed winding instead of the concentrated winding. Also, the connection of the windings has been described with respect to the Y connection, but the same effect can be obtained with a Δ connection. In addition, when the compressor is demagnetized, it is preferable that the compressor be fixed because the rotor may rattle or move when a voltage is applied. If the heat of the rotor escapes to the outside and the temperature of the rotor hardly rises, an enclosure may be provided around the motor.

In this embodiment, the compressor motor used in a room air conditioner or a refrigerator has been described as an example. However, other examples include a motor for driving a washing machine, a fan motor, a cleaner, an FDD, and an electric vehicle. It goes without saying that the present invention can be applied to all products equipped with a motor having a permanent magnet, such as a drive motor. When the motor alone is demagnetized, the stator 5 and the rotor 9 can be set as a set and demagnetized by applying the above-described high-frequency voltage to predetermined terminals of the winding 4.

FIG. 11 is a view showing a state in which a temperature sensor for detecting a temperature is directly attached to the motor. In the figure, 100 is a holding portion for holding a motor, 4 is a winding of a stator 5, 6 is a rotor shaft, and 7 is a rotor core. 103, 1
Reference numeral 04 denotes a temperature detecting means such as a temperature detecting sensor or a thermocouple for detecting the temperature.
Attached to the surface. Therefore, when the motor alone or the motor is exposed to the outside, if the temperature detecting means 103 and 104 such as a thermocouple and a temperature sensor are directly attached to the motor as shown in FIG. Based on the detected temperature, the time for applying the voltage to the motor can be determined, for example, by stopping the application of the voltage to the motor.

In this case, the temperature detecting means is preferably located near the permanent magnet, and is preferably mounted on the rotor 9. When mounting on a stator, the correlation between the temperature detection means and the temperature of the permanent magnet section may be measured in advance. Therefore, according to this method, the temperature of the motor can be directly detected, so that the demagnetization can be surely performed, and the demagnetization time can be shortened because there is no need to take a margin. Further, since the voltage application time can be shortened, the electricity bill can be reduced.

When the motor is housed in a closed container or the like and the motor is not exposed to the outside or when it is difficult to attach the temperature detecting means, the resistance detecting means detects the resistance of the winding of the stator. If means is provided and the winding resistance of the stator is detected, the temperature of the winding can be estimated from the resistance of the winding, and the temperature of the motor can be estimated from the temperature of the winding. Therefore, the time for applying the voltage to the motor can be determined based on the temperature of the motor estimated from the resistance of the winding. Therefore, according to this method, since the temperature of the motor can be estimated, the demagnetization can be surely performed, and there is no need to uselessly apply voltage.

Further, the temperature information from the temperature detecting means or the resistance information from the resistance detecting means is transmitted to the control means 111.
The control means 111 can control the voltage application time to the motor based on the input information. FIG. 12 is a flowchart in the case where the voltage application time is controlled based on the temperature detecting means. In the figure, S
T11 is a start, ST12 is a voltage application step for applying a voltage to the motor, ST13 is a frequency control step for controlling the frequency and magnitude of the applied voltage, ST14 is a motor heating step for heating the motor, and ST15 is a motor temperature step. A motor temperature detecting step for detecting or estimating, ST16 is a temperature judging step for judging whether or not the motor temperature is equal to or lower than a preset temperature, and ST17 is ST
A voltage application stop step of stopping voltage application when the motor temperature becomes higher than the set temperature based on the temperature information determined by step 16, and ST18 is an end.

In ST12, a voltage is applied to a predetermined phase of the motor. In ST13, the frequency of the applied voltage, the magnitude of the voltage,
The voltage is applied while controlling the application time and the like to a set value. Here, as the magnitude of the voltage increases, the larger the current flows, the shorter the heating time can be.However, there is a risk that the motor may break down, so the relationship between the magnitude and frequency of the voltage and the temperature rise of the motor must be determined in advance. It is desirable to grasp it through experiments. Then, by applying the voltage, the motor is heated in ST14. And
In step ST15, the motor temperature is detected by the temperature detecting means 103 or 104, or the voltage application is temporarily stopped to measure the winding resistance and estimate the temperature from the winding resistance to grasp the temperature of the rotor having the permanent magnet. I do. ST16
If the temperature of the rotor grasped in the above becomes higher than a preset temperature (a temperature at which the permanent magnet can be demagnetized), ST1
At 7, the application of the voltage is stopped. If the temperature of the rotor grasped in ST16 is lower than the preset temperature, ST13
And the voltage application is continued.

Therefore, when the detected or estimated motor temperature reaches a preset temperature (a temperature at which the permanent magnet can be demagnetized), the application of the voltage is stopped, so that the motor temperature can be grasped by simple means. In addition, the demagnetization can be reliably performed even if the type of the motor is changed with low-cost equipment. Further, since the temperature is detected and the application of the voltage is stopped, it is not necessary to uselessly apply the voltage, and the electricity bill can be reduced. If the temperature of the motor or the resistance of the winding cannot be detected at all times, the degree of temperature rise is estimated from information on the temperature and resistance at several points measured at a certain time, and the voltage application time is determined. May be performed.

FIG. 13 is a flowchart for controlling the voltage application time based on the temperature detecting means. In the figure, ST111 is a start, ST112 is a voltage application step of applying a voltage to the motor, ST113 is a frequency control step of controlling the frequency of the applied voltage and the magnitude of the voltage, ST114 is a motor heating step of heating the motor, and ST115 is a ST116 is a motor temperature detecting step of detecting or estimating the temperature of the motor, and ST117 is a method of predicting the degree of increase in the temperature of the motor by determining whether or not it is time to detect the set temperature or resistance value. A voltage application time setting step of estimating a time when the temperature becomes equal to or lower than the set temperature and setting the estimated time as a voltage application stop time.
A voltage application time determination step for determining whether or not the voltage application stop time set in step 17 has been reached. ST119 is a voltage application for stopping voltage application when the voltage application stop time has been reached in the voltage application time determination step ST118. The stop step, ST119, is an end.

In ST112, a voltage is applied to a predetermined phase of the motor, and in ST113, the frequency and magnitude of the applied voltage are controlled so as to be set values. The motor is heated by.
Then, in ST115, it is determined whether or not it is time to detect a preset motor temperature or winding resistance. If the detection time has come, the motor temperature is detected in ST116 by the temperature detecting means 103 or The winding resistance is measured by detecting by 104 or temporarily stopping the voltage application, and the temperature is estimated from the winding resistance to grasp the temperature of the portion having the permanent magnet.

Then, the time required to reach a preset temperature (the temperature at which the permanent magnet can be demagnetized) is estimated from the temperature grasped in ST117, and the voltage application time is reset to the time from the measurement point and set. . When estimating time,
The detection may be performed at least twice, and the estimation accuracy may be increased each time the number of detections increases. S in ST118
It is determined whether or not the voltage application stop time set in T117 has been reached.
At 119, the application of the voltage is stopped. If the voltage stop time has not elapsed in ST118, the process returns to ST113, and the application of the voltage is continued.

Therefore, it is not necessary to constantly monitor the temperature and the resistance value. Instead, the application of the voltage may be temporarily stopped, the temperature may be measured instantaneously, and the application of the voltage may be restarted. During this operation, the time for stopping the voltage application is short, and the voltage application and the temperature measurement can be performed efficiently.
In addition, since the permanent magnet type motor inside the sealed container can be demagnetized without removing the motor from the sealed container, the time for disassembling the sealed container can be shortened, and the labor and cost for disassembly can be reduced. Therefore, the cost UP at the time of recycling can also be suppressed.

In this embodiment, the hermetic compressor constituted by the hermetic container has been described. However, the hermetic compressor does not need to be separately provided, and can be disassembled by bolts or the like. Even if the present invention is applied, demagnetization can be performed without removing the motor by taking out bolts and the like, so that the labor and time required for disassembly can be reduced.

Embodiment 2 FIG. 14 is a simplified view of a dismantling (crushing) apparatus for crushing a product having a permanent magnet according to a second embodiment of the present invention.
In the figure, reference numeral 21 denotes an input port for inputting a product such as a compressor, 22 denotes a roller-shaped crushing section having a blade portion for crushing and crushing the product input into the input port 21, and 23 denotes a crushing section 22. An outlet for discharging the crushed pieces crushed by
24 is a storage section for storing the discharged crushed pieces, 25a
Is a first coil mounted near the crushing section 22 near the crushing section 22 for applying a magnetic field in a direction substantially perpendicular to the crushing section 22, for example. A second coil, which is attached and applies a magnetic field in a direction substantially orthogonal to the housing, is connected to each terminal of the coils 25a and 25b to supply power, and 112 is a power supply to each terminal. Control means for controlling the frequency and the application time, 20 is disassembly (crushing)
The apparatus is composed of an inlet 21, a crusher 22, an outlet 23, a housing 24, coils 25a and 25b, a power supply 11, and the like.

Next, the operation of the dismantling (crushing) apparatus will be described with reference to FIG. FIG. 15 is a flowchart showing the operation of the dismantling (crushing) device. In the figure, ST21 is a start, ST22 is a charging step of charging a workpiece such as a product, ST23 is a crushing step of crushing the workpiece, S
T24 is a discharge step of discharging crushed pieces of the work crushed in the crushing step, ST25 is a storage step of storing the crushed pieces in the storage section, and ST26 is an end.

In step ST27, the crushed pieces attached to the crushed portion are heated to demagnetize the permanent magnets thermally, or a magnetic field is applied to the crushed pieces attached to the crushed portion to electrically demagnetize the permanent magnets. ST28 is a thermal demagnetization step of heating the crushed pieces attached to the outlet and thermally demagnetizing the permanent magnet, or the crushed pieces attached to the outlet. A demagnetization step for performing one of electric demagnetization of applying a magnetic field to the permanent magnet to electrically demagnetize the permanent magnet. ST29 heats the crushed pieces adhered to the housing portion to thermally reduce the permanent magnet. This is a housing demagnetization step of performing one of thermal demagnetization to magnetize and electric demagnetization of applying a magnetic field to the crushed pieces attached to the housing to electrically demagnetize the permanent magnet.

First, a product such as a compressor having a permanent magnet in the charging step ST22 is charged from the charging port 21 of the disassembling (crushing) device 20, and the workpiece charged in the crushing step ST23 is guided to the crushing section 22. The work is crushed into crushed pieces by the crushing unit 22 having a blade portion. Next, the crushed pieces crushed in the discharge step ST24 are discharged from the discharge port 23, and are stored in the storage section 24 in the storage step ST25. Here, the crushed pieces of the permanent magnet adhere to the crushing portion 22 and the discharge port 23 made of a ferromagnetic material. Further, the permanent magnet pieces that have passed through the discharge port 23 are simultaneously stored in the storage unit 24 while being attached to crushed iron chips and the like. When the housing 24 is made of a ferromagnetic material, the housing 24
Fragments of the permanent magnet will adhere to the wall of the device.

Therefore, in the present embodiment, the crushing step S
During the crushing of the work in T23 or after the crushing of the work in the crushing step ST23 is completed, in the crushing part demagnetization step ST27, a heater or a burner provided in the crushing part 22 or in the vicinity of the crushing part 22 is used. The crushed piece having the permanent magnet attached to the crushing section 22 is heated by a heating section (not shown) of the crushing section 22 and is heated to a demagnetizable temperature to thermally demagnetize, or the crushing section 22 or the crushing section Demagnetization was performed by applying a magnetic field to a crushed piece having a permanent magnet attached to the crushing portion 22 by applying a current to a coil 25a provided near the crushing portion 22 to electrically demagnetize the crushed piece. Thereafter, the process proceeds to the discharge step ST24.

Similarly, during the discharge of the crushed pieces in the discharge step ST24 or after the discharge of the crushed pieces in the discharge step ST24 is completed, the discharge port demagnetization step S is performed.
At T28, the crushed pieces having the permanent magnets attached to the outlet 23 are heated by a heating unit (not shown) such as a heater provided near the outlet 23 or the outlet 23 and heated to a temperature at which demagnetization is possible. The magnetic field is applied to the crushed pieces having the permanent magnet attached to the discharge port 23 by applying heat to the discharge port 23 or a coil 25a provided in the vicinity of the discharge port 23 to thermally demagnetize the magnetic material. After the demagnetization is performed by either of the methods, the process proceeds to the housing step ST25.

Further, while the crushed pieces are stored in the storage step ST25 or after the storage of the crushed pieces in the storage step ST25 is completed, the storage section demagnetization step S is performed.
At T29, the crushed pieces having the permanent magnets attached to the housing portion 24 are heated by the housing portion 24 or the heating portion 25b provided in the vicinity of the housing portion to increase the temperature to a temperature at which demagnetization is possible, and thermally demagnetize. Or by applying a magnetic field to a crushed piece having a permanent magnet attached to the housing portion 24 by energizing the housing portion 24 or a coil 25a provided near the housing portion 24 to electrically demagnetize the crushed piece. After the demagnetization is performed by either of the methods, a series of steps is terminated. Therefore, the crushing unit 22 of the crushing device 20,
Fragments having a permanent magnet can be prevented from adhering to the discharge port 23 or the accommodating portion 24, and failure or deterioration of the device can be prevented. Here, the crushing part demagnetization step ST27, the discharge port demagnetization step ST28, and the housing part demagnetization step ST29
You do not need to perform all three steps,
Since the demagnetization can be performed by performing two steps, the same effect can be obtained.

Here, an example of the voltage applied to the coils 25a and 25b will be described with reference to FIG. FIG. 16 is a diagram illustrating an example of a voltage waveform applied in the present embodiment. In the figure, the horizontal axis represents the applied time, and the vertical axis represents the magnitude of the applied voltage. Using the power supply 11 having the control means 112, the coils 25a and 25b are
Several tens Hz and several k that attenuate over time as shown in
An AC voltage of about V is applied for an instant to several minutes. As a result, an alternating magnetic field whose amplitude gradually decreases is applied to the permanent magnet, so that the orientation of the magnetic moment in the permanent magnet is averaged, the residual magnetism due to the hysteresis phenomenon is gradually reduced, and the strength of the AC magnetic field is increased. Reaches zero, debris having a permanent magnet can be demagnetized. Also, the coil 25a,
A voltage may be applied to the coil 25b at the same time, or a voltage may be separately applied.

Therefore, it is possible to remove the crushed pieces of the permanent magnet adhered to the crushing section and the wall of the storage section with simple equipment, and to remove the crushed pieces attached to the apparatus from the apparatus by disassembling the apparatus. And time can be shortened. Further, since the permanent magnet attached to the iron scrap can be separated, it is not necessary to separate the permanent magnet, so that the time can be shortened and the cost for separation can be reduced. Further, in this method, a magnetic field is applied, so that it is not necessary to raise the temperature of the crushed pieces having the permanent magnet to the Curie temperature or higher. Therefore,
When the temperature is raised to the Curie temperature, parts that cannot be used at the time of recycling because the temperature exceeds the allowable temperature do not occur, and there is no need to sort unusable parts. Further, since the temperature is not raised to a temperature higher than the Curie point, energy saving and improvement of the recycling rate can be achieved, and the recycling cost can be reduced. Further, even if the applied voltage is a high frequency voltage of several kHz to several tens MHz as shown in FIG. 10 described in the first embodiment, demagnetization can be similarly performed.

FIG. 17 shows a demagnetization curve of the ferrite magnet. FIG. 18 shows a demagnetization curve of a rare-earth magnet composed mainly of neodymium, iron, boron, and the like. In the figure, the horizontal axis indicates the holding force, and indicates that the smaller the holding force, the more the demagnetization of the permanent magnet can be performed with a small demagnetizing field (small current). The vertical axis is the magnetic flux density,
The higher the self-foot density, the higher the magnetic force of the magnet. From the figure, it can be seen that the ferrite magnet has a characteristic that the coercive force (current value that can be demagnetized) decreases as the temperature decreases. For rare earth magnets,
Conversely, it can be seen that the coercive force (current value at which demagnetization can occur) decreases as the temperature increases.

Therefore, the demagnetization characteristics of the permanent magnet differ depending on the material constituting the permanent magnet. When the material of the permanent magnet is mainly composed of ferrite, the temperature of the permanent magnet is set to a temperature lower than room temperature, In addition, when the material of the permanent magnet is composed mainly of neodymium, iron, boron, etc., the temperature of the permanent magnet is set to a temperature higher than room temperature, and then the demagnetizing current is applied, so that the Curie is applied. The demagnetization can be performed with a smaller current than at room temperature without raising the temperature of the permanent magnet to a point or more, and demagnetization with high reliability and low electricity cost can be reliably performed.

As described above, by applying a voltage to the coils 25a and 25b to apply a magnetic field to the crushed pieces, the crushed pieces having the permanent magnet adhered to the crushing portion 22 and the wall surface of the storage section and the iron swarf can be easily formed. As a result, the recovery rate of the permanent magnet material can be improved. Further, the crushed pieces having the permanent magnet do not adhere to the iron scraps, and the quality of the collected iron can be improved. In addition, if the accommodating portion is made of a non-magnetic material in advance, the crushed pieces having the permanent magnet will not adhere to the wall surface of the accommodating portion, and the recovery rate of the permanent magnet pieces can be further improved.

Further, instead of an electric demagnetization method in which a high-frequency magnetic field is applied to a coil, there is a method in which a crushed piece having a permanent magnet is heated to a temperature equal to or higher than the Curie temperature to be demagnetized. The same effect can be obtained by a thermal demagnetization method in which the crushed pieces are forcibly heated. As a heating method, any method can be used as long as it can be heated to a Curie temperature or higher and thermally demagnetized, such as a nichrome wire heater, a heating wire, direct heating by burning flame or hot air.

[0060]

As described above, the invention according to claim 1 is
A high-frequency power supply for generating a high-frequency voltage, voltage applying means for applying a high-frequency voltage generated from the high-frequency power supply between at least two terminals of a stator winding of a motor having a permanent magnet, Control means for controlling at least one of the magnitude or the frequency of the voltage or the voltage application time, and heating the motor by applying the voltage controlled by the control means to demagnetize the permanent magnet. Therefore, it is possible to obtain a demagnetization device that can easily perform demagnetization of the permanent magnet with only simple equipment including only a power supply.

According to a second aspect of the present invention, there is provided a compressor having a sealed terminal provided in a container for energizing a permanent magnet type motor housed in the container, and a container between at least two of the sealed terminals. A voltage application means for applying a high-frequency voltage from outside of the apparatus, and control means for controlling at least one of the magnitude of the voltage applied by the voltage application means, the frequency of the voltage, and the voltage application time. To obtain a demagnetization device that can easily demagnetize the permanent magnet without removing the motor from the container because the motor is heated by applying a controlled voltage to demagnetize the permanent magnet. Can be.

According to the third aspect of the present invention, since the variable frequency control means for varying the frequency of the applied voltage is provided, the permanent magnet can be reduced without depending on the rotor structure or the material of the motor having the permanent magnet. A demagnetization device capable of magnetizing can be obtained.

Further, the invention according to claim 4 is provided with temperature detecting means for detecting the temperature of the motor, and when the temperature of the motor detected by the temperature detecting means reaches a preset temperature, the application of the voltage is performed. Since the motor is stopped, the time for applying a voltage to the motor can be determined based on the temperature detected by the temperature detecting means. Further, since the motor temperature can be directly detected, the number of motors that can be surely demagnetized can be reduced. A magnetic device can be obtained.

According to a fifth aspect of the present invention, there is provided a resistance detecting means for detecting a resistance value of a winding of a motor, and a temperature estimating means for estimating a motor temperature based on the resistance value detected by the resistance detecting means. When the temperature of the motor estimated by the temperature estimating means is equal to or higher than a preset temperature, the application of the voltage is stopped, so that based on the motor temperature estimated from the winding resistance, Thus, it is possible to determine the time for applying the voltage to the motor, and it is possible to obtain a low-cost demagnetizing device which does not require a separate temperature detecting means.

The invention according to claim 6 provides a crushing section for crushing a product having a permanent magnet and a crushed piece having a permanent magnet attached to the crushing section to thermally reduce the permanent magnet of the crushed piece. A demagnetization unit that performs at least one of thermal demagnetization to magnetize or electric demagnetization of applying a magnetic field to a crushed piece having a permanent magnet attached to the crushed part to electrically demagnetize the permanent magnet of the crushed piece; Therefore, it is possible to prevent the crushed pieces having the permanent magnet from adhering to the crushing portion of the crushing device, and to obtain a dismantling device of the product having the permanent magnet, which can prevent the failure and the deterioration of the device.

The invention according to claim 7 is a crushing section for crushing a product having a permanent magnet, a discharge port for discharging crushed pieces crushed by the crushing section, and a crushed piece discharged from the discharge port. A demagnetizing part for heating a crushed piece having a permanent magnet attached or contained in the containing part and thermally demagnetizing the permanent magnet of the crushed piece or a permanent magnet attached or contained in the containing part At least one of an electric demagnetizing portion that applies a magnetic field to the crushed pieces and electrically demagnetizes the permanent magnets of the crushed pieces, so that the permanent magnet adhered to the iron swarf housed in the housing section It is possible to obtain a low-cost and low-cost dismantling apparatus for a product having a permanent magnet, which can reduce the time required for separation and reduce the cost for separation.

The invention according to claim 8 is characterized in that an alternating voltage that attenuates with time is applied to the housing or a coil provided near the housing to apply a magnetic field to the crushed pieces of the permanent magnet attached to the crushing section. Permanent magnet that has a magnetic part that can remove the crushed pieces of permanent magnet attached to the housing with simple equipment and in a short time, and reduce the time and effort to remove the crushed pieces attached to the housing from the device. Can be obtained.

According to the ninth aspect of the present invention, since the accommodating portion for accommodating the crushed pieces crushed in the crushing section is made of a non-magnetic material, the crushed pieces having the permanent magnet adhere to the wall surface of the accommodating section. Therefore, it is possible to obtain an apparatus for dismantling a product having a highly recyclable permanent magnet, which can further improve the recovery rate of the permanent magnet pieces.

The invention according to claim 10 is a method for applying a magnetic field to a crushed piece of a permanent magnet adhered to a crushing portion by applying an alternating voltage that attenuates with time to the crushing portion or a coil provided near the crushing portion. Disassembly of products with highly reliable permanent magnets, which have a magnetic part, can remove crushed pieces of permanent magnets attached to the crushing part with simple equipment and in a short time, and prevent equipment failure and deterioration. A device can be obtained.

The invention according to claim 11 is a high frequency voltage applying step for applying a high frequency voltage between at least two terminals of a winding of a motor having a permanent magnet, and a high frequency voltage applying step applies the high frequency voltage to the motor. And a motor heating step of heating the motor by heating the motor until the permanent magnet of the motor is demagnetized. It is possible to obtain a demagnetizing method that can easily perform magnetizing.

According to a twelfth aspect of the present invention, there is provided a voltage applying step for applying a high-frequency voltage from outside the container to a sealed terminal provided in the container to energize a winding of a permanent magnet type motor housed in the container. A heating step of heating the motor inside the container by applying a voltage to the sealed terminal in the voltage applying step, a resistance detecting step of detecting a resistance value of the motor winding heated by the heating step, and a resistance detecting step Temperature estimating step of estimating the temperature of the motor from the resistance value of the winding detected in,
Since the application time of the high-frequency voltage is controlled based on the temperature estimated in the temperature estimation step, there is no need to constantly monitor the temperature and the resistance value, and the demagnetization that can determine the voltage application time efficiently You can get the way.

According to a thirteenth aspect of the present invention, there is provided a charging step for charging a product having a permanent magnet, a crushing step for crushing the product charged in the charging step, and discharging crushed pieces crushed in the crushing step. A discharging step and a housing step for housing the crushed pieces discharged by the discharging step, and a heating step of heating the crushed pieces after the crushing step and demagnetizing the permanent magnet of the crushed pieces or applying a magnetic field to the crushed pieces. At least one of the steps of applying a magnetic field to demagnetize the permanent magnets of the crushed pieces, so that the crushed pieces having the permanent magnets can be prevented from adhering to the respective parts of the crushing apparatus, thereby preventing failure and deterioration of the apparatus. It is possible to obtain a product dismantling device having a highly reliable permanent magnet.

Further, the invention according to claim 14 includes a voltage application step of applying an AC voltage that attenuates with time to a coil provided in the dismantling apparatus, and crushing is performed by applying a voltage to the coil in the voltage application step. Since the permanent magnet is demagnetized by applying a magnetic field to the piece, it is possible to demagnetize the crushed piece having the permanent magnet attached to each part of the device and iron scrap without raising the Curie temperature with simple equipment. In addition, it is possible to obtain a dismantling device for a product having a highly recyclable permanent magnet capable of improving the recovery rate of the permanent magnet material.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a structure of a motor having a general three-phase four-pole permanent magnet, representing a first embodiment.

FIG. 2 is a connection diagram of a coil that is developed from the inner diameter side of the motor according to the first embodiment.

FIG. 3 is a cross-sectional view of a rotor that represents another example of the motor having the permanent magnet according to the first embodiment.

FIG. 4 is a sectional view of a rotor representing another example of the motor having the permanent magnet of the first embodiment.

FIG. 5 is a cross-sectional view of a rotor that represents another example of the motor having the permanent magnet according to the first embodiment.

FIG. 6 is a cross-sectional view of a compressor including a motor having a permanent magnet according to the first embodiment.

FIG. 7 is a connection diagram when a voltage is applied to a three-phase Y-connected motor representing the first embodiment to perform demagnetization;

FIG. 8 is a diagram illustrating an example of a voltage waveform applied according to the first embodiment;

FIG. 9 is another cross-sectional view of the motor having the permanent magnet according to the present embodiment.

FIG. 10 is an example of an applied voltage waveform when the frequency of the voltage applied to the motor is made variable.

FIG. 11 is a diagram illustrating a state where the temperature sensor for detecting the temperature according to the first embodiment is directly attached to the motor.

FIG. 12 is a flowchart illustrating the case where the application of a voltage is stopped according to the first embodiment.

FIG. 13 is a flowchart in the case of controlling the voltage application time according to the first embodiment.

FIG. 14 is a simplified diagram of a crusher for crushing a product having a permanent magnet according to the second embodiment.

FIG. 15 is a flowchart illustrating an operation of the crushing apparatus according to the second embodiment.

FIG. 16 is a diagram illustrating an example of a voltage waveform applied in the present embodiment.

FIG. 17 is a demagnetization curve of a ferrite magnet.

FIG. 18 is a demagnetization curve of a rare earth magnet.

[Explanation of symbols]

1 stator core, 2a, 2b, 2c, 2d, 2e, 2
f slot, 3a, 3b, 3c, 3d, 3e, 3f
Teeth, 4 windings, 5 stators, 6 rotor shafts,
7 rotor core, 8 permanent magnet, 9 rotor, 10 air gap, 11 power supply, 11A, 11B connection terminal, 12 compressor, 13 sealed container, 14 glass terminal, 15A, 1
5B bearing, 16 U-phase terminal, 17 V-phase terminal, 1
8 W-phase terminal, 19 retaining ring, 20 dismantling device, 2
1 inlet, 22 crushing section, 23 outlet, 24 housing section, 25a first coil, 25b second coil, 10
0, holding unit, 103, 104 temperature detecting means, 111,
112 control means.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) H02K 21/16 H02K 21/16 MF term (reference) 3H003 AA05 AB04 AC03 CE03 CF05 4D067 CG06 DD02 DD06 DD14 EE32 GA10 GB05 5H621 BB10 HH01 JK05 5H622 CA02 CA13 CB01 PP03 PP10

Claims (14)

[Claims] A high-frequency power supply for generating a high-frequency voltage;
Voltage applying means for applying a high-frequency voltage generated from the high-frequency power source between at least two terminals of a motor winding having a permanent magnet, and a magnitude, frequency or voltage of the voltage applied by the voltage applying means Control means for controlling at least one of time,
A demagnetization device characterized in that the motor is heated by applying a voltage controlled by the control means to demagnetize the permanent magnet. 2. A compressor having a sealed terminal provided on said container for energizing a permanent magnet type motor housed inside the container, and a high-frequency voltage between at least two of said sealed terminals from outside the container. Voltage applying means for applying the voltage, the magnitude of the voltage applied by the voltage applying means,
Control means for controlling at least one of a frequency of a voltage and a voltage application time, and heating the motor by applying a voltage controlled by the control means to demagnetize the permanent magnet. A demagnetization device characterized by the following. 3. The demagnetization device according to claim 1, further comprising a variable frequency control means for varying a frequency of the applied voltage. 4. A temperature detecting device for detecting a temperature of a motor, wherein the application of the voltage is stopped when the temperature of the motor detected by the temperature detecting device reaches a preset temperature. Claims 1 to 3 characterized in that:
The demagnetization device according to claim 1. 5. A resistance detecting means for detecting a resistance value of a winding of a motor, and a temperature estimating means for estimating a temperature of the motor based on the resistance value detected by the resistance detecting means; The voltage application is stopped when the temperature of the motor estimated by the estimating means becomes equal to or higher than a preset temperature. Demagnetizer. 6. A crushing unit for crushing a product having a permanent magnet, and a thermal demagnetization method for heating a crushed piece having a permanent magnet attached to the crushing unit to thermally demagnetize the permanent magnet of the crushed piece. A demagnetization unit that applies a magnetic field to a crushed piece having a permanent magnet attached to the crushed part and performs at least one of electric demagnetization to electrically demagnetize the permanent magnet of the crushed piece. Dismantling apparatus for a product having a permanent magnet. 7. A crushing unit for crushing a product having a permanent magnet, an outlet for discharging crushed pieces crushed by the crushing unit, a storage unit for storing crushed pieces discharged from the outlet, A heat demagnetizing unit for heating a crushed piece having a permanent magnet attached or accommodated in a housing to thermally demagnetize the permanent magnet of the crushed piece, or a crushing machine having a permanent magnet attached or housed in the housing. A disassembly apparatus for a product having a permanent magnet, comprising: at least one of an electric demagnetizing unit that applies a magnetic field to the piece to electrically demagnetize the permanent magnet of the crushed piece. 8. A demagnetizing section for applying a magnetic field to a crushed piece of the permanent magnet attached to the crushing section by applying an AC voltage that attenuates with time to a housing section or a coil provided near the housing section. An apparatus for dismantling a product having a permanent magnet according to claim 7. 9. The storage section for storing crushed pieces crushed by the crushing section is made of a non-magnetic material.
An apparatus for dismantling a product having the permanent magnet according to claim 8. 10. A demagnetization section for applying a magnetic field to a crushed piece of the permanent magnet attached to the crushing section by applying an AC voltage that attenuates with time to a crushing section or a coil provided near the crushing section. An apparatus for dismantling a product having a permanent magnet according to any one of claims 6 to 9, characterized in that: 11. A high frequency voltage applying step of applying a high frequency voltage between at least two terminals of a winding of a motor having a permanent magnet, and applying the high frequency voltage to the motor by the high frequency voltage applying step. A motor heating step of heating, wherein the motor is heated until the permanent magnet of the motor is demagnetized. 12. A voltage applying step of applying a high-frequency voltage from outside the container to a sealed terminal provided in the container to energize a winding of a permanent magnet type motor housed in the container, and the voltage applying step. A heating step of heating the motor inside the container by applying a voltage to the sealed terminal, a resistance detection step of detecting a resistance value of a winding of the motor heated by the heating step, and the resistance detection step A temperature estimating step of estimating the temperature of the motor from the resistance value of the winding detected in the step (a), wherein the application time of the high-frequency voltage is controlled based on the temperature estimated by the temperature estimating step. Demagnetization method. 13. A charging step of charging a product having a permanent magnet, a crushing step of crushing the product charged by the charging step, a discharging step of discharging crushed pieces crushed by the crushing step, and the discharging A housing step of housing the crushed pieces discharged by the step, and heating the crushed pieces after the crushing step to demagnetize the permanent magnet of the crushed pieces or applying a magnetic field to the crushed pieces. A method of disassembling a product having a permanent magnet, comprising at least one of a magnetic field applying step of demagnetizing the permanent magnet of the crushed piece. 14. A voltage applying step of applying an AC voltage that attenuates with time to a coil provided in the dismantling device, wherein a magnetic field is applied to the crushed pieces by applying a voltage to the coil in the voltage applying step. 14. The method for dismantling a product having a permanent magnet according to claim 13, wherein the permanent magnet is demagnetized.