Motor stator recycling method

Abstract

To provide a recycling method of a motor stator for separation and recovery of a metal wire from the motor stator by a simple step and at low cost.SOLUTION: A method includes: a breaking and film removal step of breaking an iron core by a breaking medium of a breaker, separating an enamel wire from the iron core, colliding iron core broken chips formed by breaking the iron core and the breaking medium with an enamel wire, shredding the enamel wire and parting the enamel coating of the enamel wire from the metal wire; and a sorting step of sorting and recovering the iron core broken chips and the metal wire respectively.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a recycling method for a motor stator for separating and recovering a metal wire from the motor stator.

Background Art

[0002] Motors have been conventionally widely used as power sources for various industrial machines and household electrical appliances. Many motors are recovered from used automobiles, household appliances, industrial electrical equipment, etc. A motor has a component called a stator (stator, hereinafter referred to as a motor stator) that generates a rotating magnetic field. This motor stator is composed of a core in which thin plates of ferromagnetic materials such as silicon steel sheets are laminated, and a winding (coil) in which an enameled wire obtained by covering the periphery of a metal wire (copper wire, aluminum wire, steel wire) with an enamel coating is wound around this core. Further, depending on the type, there is also a type in which the core is molded with resin to improve thermal conductivity and insulation. Hereinafter, the components excluding the enameled wire from the motor stator are called the core.

[0003] For example, the copper wire widely used for metal wires is copper with a purity of 99.9 mass% or more, but since it contains an enamel coating as an insulating material, the purity of the copper wire recovered as a recycled material is handled as about 98 mass%, and most of it is used as a raw material for copper smelting. If enamel can be peeled off from the enamel-coated copper wire (enameled wire) to recover high-grade copper, it can be used with high added value, such as a raw material for drawn copper products.

[0004] Conventionally, as a method for peeling off the enamel coating from an enamel-coated copper wire, for example, Patent Document 1 discloses a method in which the enamel wire is heated to carbonize the enamel coating and then a mechanical external force is applied to peel off the carbonized enamel coating.

[0005] Further, Patent Document 2 discloses a method in which the enamel wire is immersed in an alkaline solution such as sodium hydroxide to hydrolyze the enamel coating, and then an external force is applied to remove the hydrolyzed enamel component. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 6056088 [Patent Document 2] Japanese Patent Application Publication No. 10-025523 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the method for stripping enamel from enameled wire disclosed in Patent Document 1 mentioned above has the problem of requiring a large amount of energy for heating, as it involves a step of heating the enameled wire to about 500°C to 800°C to carbonize the enamel coating. In addition, it also has the problem of high processing costs because it is necessary to treat the exhaust gas generated during the carbonization of the enamel coating. Furthermore, heating can cause oxidation of the metal wire or fusion of carbides to the metal wire, which can reduce the purity of the metal. This necessitates a subsequent chemical cleaning step to improve the purity of the metal, which also has the problem of complicating the process.

[0008] Furthermore, the method for stripping the enamel coating from enameled wire disclosed in Patent Document 2 requires a high-concentration alkaline solution to hydrolyze the enamel coating, and heating is necessary to accelerate the hydrolysis, resulting in high processing costs such as chemical and fuel costs. In addition, since the enamel coating cannot be sufficiently removed by impregnation with an alkaline solution alone, it is necessary to apply mechanical force in a subsequent step, resulting in a complex and costly process.

[0009] This invention has been made in view of the circumstances described above, and aims to provide a motor stator recycling method for separating and recovering metal wires from which the enamel coating has been stripped using a simple process and at low cost. [Means for solving the problem]

[0010] To solve the above problems, the present invention provides a motor stator recycling method for recovering metal wire from a motor stator, which is made by winding enameled wire, a metal wire with an enamel coating, around an iron core and molding it with a resin member, comprising: a crushing and coating removal step in which the iron core is crushed with a crushing medium of a crusher to separate the enameled wire and the resin member from the iron core; further, the crushed iron core fragments obtained from the crushed iron core, the crushed resin members obtained from the crushed resin member, and the crushing medium are brought into contact with the enameled wire to shred the enameled wire and peel off the enamel coating from the enameled wire to obtain thin pieces of enamel coating; and a sorting step in which the crushed iron core fragments, the metal wire, and the resin fragments are sorted and recovered separately. In the crushing and coating removal process, the crusher is a chain-type crusher, the crushing medium is a crushing chain, and the crushing and coating removal process is performed for a range of 90 seconds or more and 300 seconds or less. The sorting process is characterized by sorting and recovering the crushed iron core fragments using a magnetic separator, and then separating the metal wire and the resin fragments using an air separator.

[0011] According to the present invention, simply by feeding the motor stator into a crusher, the enameled wire is separated from the iron core of the motor stator. Furthermore, repeated collisions between the crushed iron core pieces and the enameled wire remove the enamel coating from the surface of the enameled wire, exposing the metal wire. This makes it possible to obtain metal wire with the enamel coating removed from the motor stator in a simple process and at low cost.

[0016] Furthermore, in the present invention, the iron core may contain silicon steel. [Effects of the Invention]

[0017] According to the present invention, a method for recycling motor stators can be provided for separating and recovering metal wires from which the enamel coating has been stripped using a simple process and at low cost. [Brief explanation of the drawing]

[0018] [Figure 1] This is a flowchart illustrating the motor stator recycling method of the present invention in a step-by-step manner. [Figure 2] This is a schematic configuration diagram showing the equipment flow used in the recycling method of the motor stator of the present invention. [Figure 3] This is a photograph showing an example of the copper wire recovered from the motor stator according to this embodiment. [Figure 4] This is a photograph showing the motor stator A in the example. [Figure 5] This is a microscopic photograph showing the state of the cross-section of the motor stator A before and after processing. [Figure 6] This is a microscopic photograph showing the state of the cross-section of the motor stator B before and after processing. [Figure 7] This is a microscopic photograph showing the state of the cross-section of the motor stator C before and after processing. [Figure 8] This is a microscopic photograph showing the state of the cross-section of the motor stator D before and after processing.

Mode for Carrying Out the Invention

[0019] Hereinafter, with reference to the drawings, a method for recycling a motor stator according to an embodiment of the present invention will be described. Each of the embodiments shown below is specifically described to better understand the gist of the invention, and does not limit the present invention unless otherwise specified.

[0020] FIG. 1 is a flowchart showing the recycling method of the motor stator of the present invention step by step. FIG. 2 is a schematic configuration diagram showing the equipment flow used in the recycling method of the motor stator of the present invention. First, the motor stator is taken out from various discarded motors. The motor stator has, for example, a cylindrical cavity for accommodating a rotor inside, and has a core and enameled wire wound around the core in a coil shape.

[0021] Generally, silicon steel, which is a silicon-containing steel material, is used for the iron core. The iron core may be formed integrally from such silicon steel in a block shape, or may be formed by laminating a plurality of silicon steel sheets. Note that, in addition to silicon steel, any ferromagnetic metal material can be used for the iron core.

[0022] On the other hand, for the resin member that molds the motor stator, an insulating polymer material, such as epoxy resin, can be used.

[0023] An enameled wire is formed by forming an enamel coating, which is an insulating layer, around a core material such as a copper wire or an aluminum wire, which is a metal component. Examples of the components of the enamel coating include polyurethane resin, polyester resin, polyesterimide resin, polyamideimide resin, polyimide resin, and the like.

[0024] In this embodiment, such a motor stator is put into a crusher (crushing and coating removal step S1) with the coil wound with enameled wire attached. As the crusher, a chain-type crusher, for example, a cross-flow shredder is used. The cross-flow shredder rotates a crushing chain, which is a crushing medium, at high speed at the bottom of, for example, a cylindrical shredder housing, and crushes the input material to about several millimeters by this rotating crushing chain.

[0025] In the crushing and coating removal step S1, when the motor stator is put into the cross-flow shredder, at an initial stage, the iron core is crushed by collision with the crushing chain (crushing medium), and the coiled enameled wire is separated from the iron core crushed pieces. The motor stator may have a resin member in addition to the iron core and the enameled wire. Due to the crushing of the motor stator, iron core crushed pieces and resin pieces obtained by crushing the resin member are generated. In the following description, the case where a silicon steel sheet is used as the iron core material is exemplified, and the iron core crushed pieces generated by the crushing of the iron core are referred to as silicon steel pieces.

[0026] In the crushing and coating removal process S1, silicon steel pieces, resin pieces, and enameled wire are generated. Further rotation of the crushing chain causes the silicon steel pieces and resin pieces to repeatedly collide with the enameled wire. The particularly hard silicon steel pieces scrape off the enamel coating on the surface of the enameled wire, forming shredded metal wire and thin flakes of the enamel coating.

[0027] Thus, in the crushing and coating removal process S1, the enamel wire collides not only with the crushing chain, which is the crushing medium, but also with the silicon steel pieces and resin pieces of the iron core that are fed in to be processed. As a result, the enamel coating is scraped off the enamel wire, separating it into a metal wire and an enamel coating. In this process, the length of the metal wire is shortened, but the cross-section does not become flattened or crushed, and remains almost circular.

[0028] The shredding time using the cross-flow shredder in the crushing and coating removal step S1 may be, for example, 30 seconds or more and 300 seconds or less, preferably 60 seconds or more and 120 seconds or less. By setting the shredding time within this range, the enamel wire is separated from the iron core, and the enamel coating on the enamel wire is almost completely removed, while preventing excessive fragmentation.

[0029] Furthermore, the small amount of dust generated during shredding by the cross-flow shredder can be removed using dust collection devices such as cyclones, electrostatic precipitators, or bag filters.

[0030] Next, the crushed material consisting of silicon steel fragments and resin fragments from the iron core separated and crushed in the crushing and coating removal process S1, as well as metal wires after the enamel coating has been removed, is sorted according to the type of material (sorting process S2).

[0031] In the sorting process S2, the crushed material (silicon steel pieces, resin pieces, and metal wires after the enamel coating has been removed) generated in the crushing and coating removal process S1 is sorted using a sieving device, a magnetic separator, an air separator, etc. Since silicon steel pieces are ferromagnetic, they can be sorted by magnetic separation, for example, and since resin has a lower specific gravity compared to metal wires and silicon steel pieces, it can be sorted by an air separator or a specific gravity separator, for example.

[0032] For example, in this embodiment, the crushed material discharged from the cross-flow shredder (crusher) in the crushing and coating removal process S1 is first separated into coarse particles (upper sieve) and fine particles (lower sieve) using a vibrating screen device. The coarse particles (upper sieve) separated by the vibrating screen device are then separated and recovered as magnetically attached silicon steel pieces using a magnetic separator, and the remaining coarse particles are fed back into the crusher for further crushing.

[0033] Meanwhile, the fine particles separated by the vibrating screen (below the screen) are separated and recovered as magnetically attached silicon steel pieces using a magnetic separator, and then separated into heavy products (metal wires) and light products (resin) using an air separator.

[0034] While air separators and gravity separators utilize differences in specific gravity to separate materials, their sorting accuracy can be further improved by standardizing particle size beforehand using vibrating screens or similar methods. Furthermore, since metal wires and silicon steel pieces have similar specific gravities, separating the non-magnetic metal wires from the magnetic silicon steel pieces using magnetic separation before using air separators or gravity separators allows for even more efficient sorting. Additionally, when copper and aluminum wires are mixed, they can be separated from each other using gravity separators or color sorters.

[0035] As a result, the crushed material discharged in the crushing and coating removal process S1 is separated into silicon steel fragments and resin fragments that constituted the iron core, and metal wires from which the enamel coating has been scraped off the enameled wire, and can be recovered separately for each material.

[0036] Figure 3 shows a photograph of an example of copper wire recovered from a motor stator using this embodiment. As can be seen in Figure 3, no enamel coating is found on any of the copper wires, confirming that the enamel coating has been almost completely removed from the enamel-coated copper wires.

[0037] As described above, according to the motor stator recycling method of this embodiment, by simply feeding the motor stator into a shredder, such as a cross-flow shredder, the iron core is separated into iron core fragments and enameled wire. Furthermore, the iron core fragments and enameled wire repeatedly collide with each other, scraping off the enamel coating on the surface of the enameled wire. As a result, metal wire with the enamel coating removed can be obtained from the motor stator in a simple process and at low cost.

[0038] Although embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Examples]

[0039] The effectiveness of the motor stator recycling method of the present invention was verified. The motor stators were extracted from motors in used home appliances. The following four types were used: Motor stator A: The coating material of the enameled wire is polyester-nylon, and the carbon (C) concentration in the enameled wire is 1.6% by mass. Motor stator B: The coating material of the enameled wire is nylon, and the carbon concentration in the enameled wire is 1.4% by mass. Motor stator carbon (C): The coating material of the enameled wire is nylon, and the carbon concentration in the enameled wire is 1.6% by mass. Motor stator D: The enameled wire coating is made of nylon, and the carbon concentration in the enameled wire is 1.4% by mass. The material of the enamel wire coating was analyzed by FT-IR, and the carbon concentration of the coating was measured by combustion-infrared absorption spectroscopy. For reference, a photograph of motor stator A is shown in Figure 4.

[0040] Using motor stators A to D, 8 kg of material from each motor stator was fed into a chain-type shredder (cross-flow shredder) for shredding and enamel wire removal. The shredding time was 90 seconds. The recovered shredded material was subjected to primary sorting using a vibrating screen with an 8 mm mesh size to separate it into coarse particles (upper screen) and fine particles (lower screen). Dust generated during shredding and sieving was collected using dust collection devices such as separators and cyclones. The coarse particles were magnetically separated using a magnetic separator with a magnetic force of 500 gauss to magnetize the shredded silicon steel sheets, and the remaining non-magnetic coarse particles were fed back into the chain-type shredder.

[0041] Meanwhile, the fine-grained material was separated into heavy and light products using a magnetic separator with a magnetic force of 500 gauss, after which the fragments of silicon steel sheets were magnetically attached. The non-magnetic material was then separated into heavy and light products using a wind separator. The heavy products were further magnetically attached to the fragments of silicon steel sheets using a magnetic separator with a magnetic force of 8000 gauss, and high-purity copper wire with the enamel coating removed was recovered as the non-magnetic material (see Figure 3).

[0042] Tables 1-4 show the composition of the enameled wires of motor stators A-D before and after treatment. Figures 5-8 show cross-sectional microscopic images of the enameled wires in motor stators A-D. The carbon (C) concentration was measured by combustion-infrared absorption spectroscopy, while other components were measured by ICP emission spectroscopy after acid dissolution. Since the carbon (C) concentration corresponds to the component concentration of the enamel coating, the degree of enamel peeling was evaluated by the decrease in carbon (C) concentration. Cross-sectional observation of the enameled wires was performed using a metallurgical microscope.

[0043] [Table 1]

[0044] [Table 2]

[0045] [Table 3]

[0046] [Table 4]

[0047] According to Table 1, crushing and peeling reduced the enamel content of motor stator A to 1 / 4, while improving the copper quality from 97.2% by mass to 99.0% by mass. According to Table 2, crushing and peeling reduced the enamel content of motor stator B to one-quarter, while improving the copper quality from 98.4% by mass to 99.2% by mass. According to Table 3, crushing and peeling reduced the enamel content of the motor stator C to 1 / 2.5, while improving the copper quality from 98.6% by mass to 99.8% by mass. According to Table 4, crushing and peeling reduced the enamel content of the motor stator D to 1 / 2.5, while improving the copper quality from 98.5% by mass to 99.4% by mass.

[0048] Furthermore, as shown in Figures 5-8, the enameled wires constituting motor stators A-D had a uniform enamel coating around the copper wire before processing, whereas after processing, it was observed that the enamel coating had peeled off in most areas that were slightly indented due to impact and abrasion. In other words, it was confirmed that the enamel coating could be removed by crushing with a crusher. [Industrial applicability]

[0049] The motor stator recycling method of the present invention makes it possible to remove the enamel coating from the enameled wires contained in various used motors and recover only the metal wires. This allows for high-quality separation and recovery of the metal wires contained in various used motors. Therefore, it has industrial applicability.

Claims

1. A motor stator recycling method for recovering metal wire from a motor stator, which is made by winding enameled wire (metal wire coated with enamel) around an iron core and molding it with a resin component, A crushing and coating removal step is performed in which the iron core is crushed by the crushing medium of the crusher, separating the enamel wire and the resin member from the iron core, and further impacting the enamel wire with the crushed iron core fragments, the crushed resin member fragments, and the crushing medium to shred the enamel wire and peel off the enamel coating from the metal wire to obtain thin pieces of the enamel coating. The system includes a sorting step for sorting and recovering the iron core fragments, the metal wires, and the resin fragments, respectively. In the crushing and coating removal process, the crusher is a chain-type crusher, and the crushing medium is a crushing chain. The crushing and coating removal process is performed for a period of 90 seconds or more and 300 seconds or less. A method for recycling a motor stator, characterized in that, in the sorting step, the crushed iron core fragments are sorted and recovered by a magnetic separator, and then the metal wires and resin fragments are separated by an air separator.

2. The motor stator recycling method according to claim 1, characterized in that the iron core contains silicon steel.

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