PERMANENT MAGNET RECOVERY DEVICE AND PERMANENT MAGNET RECOVERY METHOD

Provided are a permanent magnet recovery device and a permanent magnet recovery method capable of recovering, without degradation of permanent magnet properties, a permanent magnet attached to a laminated steel sheet, having an insulating film, via a resin material. A permanent magnet recovery device includes a heat-treating furnace that stores a permanent magnet holder in which permanent magnets are attached thereto, having insulating films, via a resin material and a high-frequency wave absorbent is provided at each end portion of the permanent magnet holder in a lamination direction of the laminated steel sheet so as to contact at least the resin material, and a microwave generator that emits microwaves into the heat-treating furnace. In this aspect, the permanent magnet holder is a predetermined rotating electrical machine rotor, and a high-frequency wave absorbent is further provided along an outer peripheral portion of the laminated steel sheet of the rotor.

This application is based on and claims the benefit of priority from Japanese Patent Application No. 2021-214038, filed on 28 Dec. 2021, the content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a permanent magnet recovery device and a permanent magnet recovery method.

Related Art

A technique of disassembling a magnetic circuit structure including laminated steel sheets to which permanent magnets are fixed with an adhesive, such as a rotor of a rotating electrical machine, and recovering the permanent magnets has been devised (see, e.g., Japanese Unexamined Patent Application, Publication No. 2001-85223). In the technique of Japanese Unexamined Patent Application, Publication No. 2001-85223, the magnetic circuit structure is heated to a high temperature in an oil furnace to carbonize the adhesive, and thereafter, the permanent magnets are recovered. Moreover, a technique of increasing the temperature of a laminated steel sheet covered with an adhesive coating by microwave heating to enhance adhesiveness of the adhesive coating has been devised (see, e.g., Japanese Unexamined Patent Application, Publication No. H11-234972).

SUMMARY OF THE INVENTION

In the technique of Japanese Unexamined Patent Application, Publication No. 2001-85223, the magnetic circuit structure is heated to the high temperature in the oil furnace to purposely neutralize the permanent magnets. In this manner, the permanent magnets can be safely recovered. However, the expensive permanent magnets are recovered with original properties thereof degraded, and for this reason, there is a great loss in terms of reuse of resources. On the other hand, the technique of Japanese Unexamined Patent Application, Publication No. H11-234972 is a technique of strengthening bonding between layers of the laminated steel sheet. Thus, such a technique involves no concern on recovery of a particular recycle target such as a permanent magnet from a magnetic circuit structure. Thus, this technique is not suitable for a recycle purpose.

The present invention has been made in view of the above-described situation, and an object thereof is to provide a permanent magnet recovery device and a permanent magnet recovery method capable of recovering, without degradation of permanent magnet properties, a permanent magnet attached to a laminated steel sheet, having an insulating film, via a resin material. If the permanent magnet can be recovered without degradation of the properties thereof, the permanent magnet can be reused, an additional permanent magnet manufacturing process can be reduced, and a reduction in the burden on the environment, such as a reduction in carbon dioxide emissions, can be achieved.

(1) A permanent magnet recovery device (e.g., a later-described permanent magnet recovery device1) includes a heat-treating furnace (e.g., a later-described heat-treating furnace2) that stores a permanent magnet holder (e.g., a later-described permanent magnet holder5) in which a permanent magnet (e.g., a later-described permanent magnet8) is attached to a laminated steel sheet (e.g., a later-described laminated steel sheet6), having an insulating film, via a resin material (e.g., a later-described resin material7) and a high-frequency wave absorbent (e.g., a later-described high-frequency wave absorbent10) is provided at each end portion of the permanent magnet holder in a lamination direction of the laminated steel sheet so as to contact at least the resin material, and a microwave generator (e.g., a later-described microwave generator3) that emits a microwave into the heat-treating furnace.

(2) In the permanent magnet recovery device according to (1), the laminated steel sheet of the permanent magnet holder has an outer peripheral portion, and a high-frequency wave absorbent (e.g., a later-described high-frequency wave absorbent12) is further provided along the outer peripheral portion.

(3) In the permanent magnet recovery device according to (1) or (2), the permanent magnet holder is a predetermined rotating electrical machine rotor (e.g., a later-described rotor9).

(4) A permanent magnet recovery method includes a high-frequency wave absorbent attachment step (e.g., a later-described high-frequency wave absorbent attachment step S1) of attaching a high-frequency wave absorbent (e.g., a later-described high-frequency wave absorbent10) to each end portion of a permanent magnet holder (e.g., a later-described permanent magnet holder5), in which a permanent magnet (e.g., a later-described permanent magnet8) is attached to a laminated steel sheet (e.g., a later-described laminated steel sheet6), having an insulating film, via a resin material (e.g., a later-described resin material7), in a lamination direction of the laminated steel sheet such that the high-frequency wave absorbent contacts at least the resin material, and a microwave heating step (e.g., a later-described microwave heating step S2) of heating, in a microwave heating furnace (e.g., a later-described microwave heating furnace4), the permanent magnet holder to which the high-frequency wave absorbent has been attached in the high-frequency wave absorbent attachment step.

(5) In the permanent magnet recovery method according to (4), the laminated steel sheet of the permanent magnet holder has an outer peripheral portion, and a high-frequency wave absorbent (e.g., a later-described high-frequency wave absorbent12) is further provided along the outer peripheral portion in the high-frequency wave absorbent attachment step.

(6) In the permanent magnet recovery method according to (4) or (5), in which the permanent magnet holder is a predetermined rotating electrical machine rotor (e.g., a later-described rotor9).

In the permanent magnet recovery device according to (1), the high-frequency wave absorbent is provided at each end portion of the permanent magnet holder in the lamination direction of the laminated steel sheet so as to contact the resin material, and therefore, the end portions, which are difficult to be heated with microwaves, of the laminated steel sheet can be efficiently heated and a heating time necessary for permanent magnet recovery can be shortened. Consequently, the permanent magnet can be recovered without degradation of the properties thereof, an additional permanent magnet manufacturing process can be reduced, and a reduction in the burden on the environment, such as a reduction in carbon dioxide emissions, can be achieved.

In the permanent magnet recovery device according to (2), the high-frequency wave absorbent is further provided along the outer peripheral portion of the laminated steel sheet, and therefore, heat can also be transmitted to the resin material from the outer peripheral side and heating can be more efficiently performed.

In the permanent magnet recovery device according to (3), the permanent magnets can be, without degradation of the properties thereof, recovered from the rotating electrical machine rotor for which many high-performance permanent magnets are used, and therefore, the recovered permanent magnets are suitable for a reuse purpose.

In the permanent magnet recovery method according to (4), the high-frequency wave absorbent is provided at each end portion of the permanent magnet holder in the lamination direction of the laminated steel sheet so as to contact the resin material, and therefore, the end portions, which are difficult to be heated with microwaves, of the laminated steel sheet can be efficiently heated and the heating time necessary for permanent magnet recovery can be shortened. Consequently, the permanent magnet can be recovered without degradation of the properties thereof, an additional permanent magnet manufacturing process can be reduced, and a reduction in the burden on the environment, such as a reduction in carbon dioxide emissions, can be achieved.

In the permanent magnet recovery method according to (5), the high-frequency wave absorbent is further provided along the outer peripheral portion of the laminated steel sheet, and therefore, heat can also be transmitted to the resin material from the outer peripheral side and heating can be more efficiently performed.

In the permanent magnet recovery method according to (6), the permanent magnets can be, without degradation of the properties thereof, recovered from the rotating electrical machine rotor for which many high-performance permanent magnets are used, and therefore, the recovered permanent magnets are suitable for a reuse purpose.

DETAILED DESCRIPTION OF THE INVENTION

Next, an embodiment of the present invention will be described with reference to the drawings. In each figure described below, the same reference numerals are used to represent the same elements or corresponding elements.FIG.1is a conceptual diagram showing a permanent magnet recovery device1according to the embodiment of the present invention.FIG.2is a view for describing a high-frequency wave absorbent attachment step in a permanent magnet recovery method according to the embodiment of the present invention.FIG.3is a flowchart of the permanent magnet recovery method according to the embodiment of the present invention.

The permanent magnet recovery device1according to the embodiment of the present invention has a heat-treating furnace2that heats a treatment target and a microwave generator3that emits microwaves into the heat-treating furnace2. The microwave generator3includes a magnetron, a waveguide, etc. The heat-treating furnace2and the microwave generator3form a microwave heating furnace4. The permanent magnet recovery device1is in such a form that a particular permanent magnet holder5as the treatment target which is a target for heating is stored in the heat-treating furnace2of the microwave heating furnace4.

The permanent magnet holder5is configured such that permanent magnets8are attached to a laminated steel sheet6, having insulating films, via a resin material7, and for example, is a disassembled rotating electrical machine rotor9. The rotor9of this type is a permanent magnet embedded rotor, and is also called an interior permanent magnet (IPM) rotor. In the IPM rotor, many expensive high-performance rare-earth magnets are held.

As inFIG.2, high-frequency wave absorbents10are attached to predetermined portions of the rotor9as the permanent magnet holder5. In this example, the high-frequency wave absorbent10is attached to each end portion of the permanent magnet holder5in a lamination direction of the laminated steel sheet6so as to contact at least the resin material7. As a result, the rotor9is in a first form of a treatment target11in which the high-frequency wave absorbents10are each attached to peripheral edge regions of the rotor9at both end surfaces in an axial direction of the rotor9.

The permanent magnet recovery method according to the embodiment of the present invention includes a high-frequency wave absorbent attachment step S1and a microwave heating step S2, as shown inFIG.3. The high-frequency wave absorbent attachment step S1is a step of forming the rotor9ofFIG.2into the first form of the treatment target11. Subsequently, in the microwave heating step S2, the treatment target11in the first form is stored in the heat-treating furnace2of the microwave heating furnace4, and is heated with the microwaves from the microwave generator3.

In the high-frequency wave absorbent attachment step S1, the treatment target11in the first form may be formed into a second form of a treatment target13in such a manner that a cylindrical high-frequency wave absorbent12is further attached so as to surround an outer peripheral portion of the laminated steel sheet6of the treatment target11in the first form. Note that in the high-frequency wave absorbent attachment step S1, a treatment target15in a third form may be formed in such a manner that a plurality of plate-shaped high-frequency wave absorbents14is attached so as to surround the outer peripheral portion of the laminated steel sheet6of the treatment target11in the first form.

FIG.5is a schematic view showing a process of heating a treatment target in the heat-treating furnace2of the microwave heating furnace4. The treatment target assumed inFIG.5is a portion of a rotating electrical machine rotor9including a laminated steel sheet6having insulating films and a resin material7holding permanent magnets8. InFIG.5, a reference numeral16is assigned to the treatment target assumed as described above. In the treatment target16, a laminated body19in which magnetic steel sheets18are stacked on each other via insulating layers17is formed corresponding to the laminated steel sheet6of the rotor9. An adhesive20corresponding to the resin material7holding the permanent magnets8in the rotating electrical machine rotor9adheres to a side end portion of the laminated body19along a lamination direction. The treatment target16is irradiated with microwaves21.

In an initial first phase P1in which irradiation of the treatment target16with the microwaves21is started, the microwaves21are reflected on the magnetic steel sheets18which are metal sheets, but propagate to the adhesive20through the insulating layers17. In a subsequent second phase P2, a high-temperature region22temperature-increased by the microwaves21starts expanding from a center portion in the adhesive20. That is, the adhesive20is heated starting from the center portion.

After the adhesive20has been further temperature-increased, the adhesive20is softened and expanded. Accordingly, a third phase P3is brought, in which each gap23between the magnetic steel sheets18is expanded. In the third phase P3, there is a great potential difference in the gap23, and eventually, electrical breakdown occurs in the gap23. Accordingly, the state of a fourth phase P4is brought, in which sparks24fly. In the fourth phase P4, the magnetic steel sheets18are heated by the sparks24.

In the fourth phase P4, even if the high-temperature region22appears in the central portion, the temperature does not rise to peripheral regions near both ends in the stacking direction of the electromagnetic steel sheets18. If the high-frequency wave absorbent10is attached to each end portion, which includes a portion of the adhesive20, of the treatment target16in the lamination direction of the magnetic steel sheets18, the high-frequency wave absorbents10are heated with the microwaves21, and such heat is transmitted to the adhesive20. Accordingly, the high-temperature region22expands across the substantially entire region in the adhesive20, and an optimal phase Pm in which optimal heating can be performed is brought. In the optimal phase Pm, the portions of the adhesive20as local regions of the treatment target16are selectively temperature-increased, and adhesive force of such an adhesive20is neutralized. Thus, the permanent magnets can be easily taken out. In this case, the permanent magnets are not temperature-increased much, and therefore, can be recovered without degradation of permanent magnet properties.

Next, results of experiment conducted for checking the action depicted inFIG.5will be described with reference toFIGS.6and7.FIG.6shows a test piece25used for this experiment. The test piece25is a replica of part of a rotating electrical machine rotor. The test piece25is configured such that silicon carbide (SiC) plate-shaped bodies as high-frequency wave absorbents10are attached to upper and lower end surfaces of a laminated body19in a lamination direction thereof, the laminated body19being a replica of a rotor body portion and being configured such that magnetic steel sheets18are stacked on each other via insulating layers17.

FIG.7is a table showing an overview of a state when temperature distribution in the laminated body19in association with irradiation with microwaves is observed over time in comparison between a case where the high-frequency wave absorbents10of the test piece25ofFIG.6are detached and a case where the high-frequency wave absorbents10are attached. InFIG.7, the higher the dot density, the higher the temperature. An elapsed time in irradiation with the microwaves in time-series observation inFIG.7is in a relationship of t1<t2<t3. As seen fromFIG.7, the internal temperature of the laminated body19increases in both the case of attaching the SiC plate-shaped bodies and the case of not attaching the SiC plate-shaped bodies as the elapsed time in irradiation with the microwaves increases. However, the case of not attaching the SiC plate-shaped bodies shows such temperature distribution that even when the elapsed time in irradiation with the microwaves reaches t3, the center portion in the laminated body19is temperature-increased, but the peripheral portion is not temperature-increased much. On the other hand, in the case of attaching the SiC plate-shaped bodies, when the elapsed time in irradiation with the microwaves reaches t3, the inside of the laminated body19is uniformly temperature-increased from the center portion to the peripheral portion. These experimental results show effectiveness of attachment of the SiC plate-shaped body as the high-frequency wave absorbent10to each end portion in the lamination direction of the magnetic steel sheets18for recovering the permanent magnets8from the rotating electrical machine rotor9which is the permanent magnet holder5holding the permanent magnets8on the laminated steel sheet6in which the magnetic steel sheets18are stacked on each other via the insulating layers17.

According to the permanent magnet recovery device and the permanent magnet recovery method of the present embodiment, the following advantageous effects are produced.

The permanent magnet recovery device1according to (1) includes the heat-treating furnace2that stores the permanent magnet holder5in which the permanent magnets8are attached to the laminated steel sheet6, having the insulating films, via the resin material7and the high-frequency wave absorbent10is provided at each end portion of the permanent magnet holder5in the lamination direction of the laminated steel sheet6so as to contact at least the resin material7, and the microwave generator3that emits the microwaves into the heat-treating furnace2. With this configuration, the end portions, which are difficult to be heated with the microwaves, of the laminated steel sheet can be efficiently heated, and a heating time necessary for permanent magnet recovery can be shortened. Consequently, the permanent magnets can be recovered without degradation of the properties thereof, an additional permanent magnet manufacturing process can be reduced, and a reduction in the burden on the environment, such as a reduction in carbon dioxide emissions, can be achieved.

In the permanent magnet recovery device according to (2), the laminated steel sheet6of the permanent magnet holder5has the outer peripheral portion, and the high-frequency wave absorbent12is further provided along the outer peripheral portion. With this configuration, heat can also be transmitted to the resin material7from the outer peripheral side, and heating can be more efficiently performed.

In the permanent magnet recovery device according to (3), the permanent magnet holder5is the predetermined rotating electrical machine rotor9. The permanent magnets8can be, without degradation of the properties thereof, recovered from the rotating electrical machine rotor9for which many high-performance permanent magnets8are used, and therefore, the recovered permanent magnets are suitable for a reuse purpose.

The permanent magnet recovery method according to (4) includes the high-frequency wave absorbent attachment step S1of attaching the high-frequency wave absorbent10to each end portion of the permanent magnet holder5, in which the permanent magnets8are attached to the laminated steel sheet6, having the insulating films, via the resin material7, in the lamination direction of the laminated steel sheet6such that the high-frequency wave absorbent10contacts at least the resin material7, and the microwave heating step S2of heating, in the microwave heating furnace4, the permanent magnet holder5to which the high-frequency wave absorbent10has been attached in the high-frequency wave absorbent attachment step S1. With this configuration, the end portions, which are difficult to be heated with the microwaves, of the laminated steel sheet6can be efficiently heated, and the heating time necessary for recovery of the permanent magnets8can be shortened. Consequently, the permanent magnets8can be recovered without degradation of the properties thereof, an additional permanent magnet manufacturing process can be reduced, and a reduction in the burden on the environment, such as a reduction in carbon dioxide emissions, can be achieved.

In the permanent magnet recovery method according to (5), the laminated steel sheet6of the permanent magnet holder5has the outer peripheral portion, and the high-frequency wave absorbent12is further provided along the outer peripheral portion in the high-frequency wave absorbent attachment step S1. With this configuration, heat can also be transmitted to the resin material7from the outer peripheral side of the laminated steel sheet6, and heating can be more efficiently performed.

In the permanent magnet recovery method according to (6), the permanent magnet holder5is the predetermined rotating electrical machine rotor9. The permanent magnets8can be, without degradation of the properties thereof, recovered from the rotating electrical machine rotor9for which many high-performance permanent magnets8are used, and therefore, the recovered permanent magnets are suitable for a reuse purpose.

The embodiment of the present invention has been described above, but the present invention is not limited to above. Details may be changed as necessary within the scope of the gist of the present invention. For example, in description above, the example where the permanent magnet holder is a rotating electrical machine rotor and the permanent magnets are recovered from such a rotor has been described. However, the present invention may be applied to a case where a permanent magnet holder is a medical tool using permanent magnets and the permanent magnets are recovered from such a medical tool.

EXPLANATION OF REFERENCE NUMERALS

1Permanent Magnet Recovery Device

6Laminated Steel Sheet

11Treatment Target in First Form

13Treatment Target in Second Form

15Treatment Target in Third Form

18Magnetic Steel Sheet