Method for recycling motor

Abstract

To provide a motor recycling method capable of removing reusable components while reducing man-hours.SOLUTION: The motor recycling method includes a crushing step (S3) of crushing a motor, and a cooling step (S2) of cooling a motor iron core by passing a liquid or gas refrigerant through a refrigerant flow path of the motor before the crushing step. In the motor recycling method, the motor may have a configuration in which the motor iron core is shrink-fitted and fixed to the casing.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a method for recycling a motor. [Background technology]

[0002] In recent years, the widespread use of electric vehicles has led to increased motor production in order to reduce CO2 emissions. This has led to challenges such as shortages of motor materials and the need to realize a recycling-oriented society. For example, rare earth elements such as copper, which is used to make motor windings, and neodymium (Nd) and dysprosium (Dy), which are used to make magnets, are attracting attention as valuable metal resources, and a system for recovering these materials from motors once they have been released onto the market is needed. Furthermore, the production of electrical steel sheets, a key component of motors, requires reducing the environmental impact, such as CO2 emissions. While electric furnace manufacturing processes using recovered scrap have been considered, the degradation of magnetic properties due to impurities remains an issue. If scrap derived from electrical steel sheets could be isolated and recovered, it would be possible to avoid the introduction of impurities that harm magnetic properties and relatively easily produce electrical steel sheets with excellent properties using an electric furnace manufacturing process.

[0003] While separating and recovering the materials that make up a motor is meaningful, the high cost of separation and recovery makes it difficult to achieve. For example, the labor required to dismantle an automobile drive motor is known to require six man-hours. It has been pointed out that mechanization of the process of removing the motor core is particularly necessary to reduce labor. For example, Patent Document 1 discloses a technology for efficiently separating and recovering the motor core and the copper winding material by cooling the motor to the brittle temperature range of ferrous metals. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-192069 Summary of the Invention [Problem to be solved by the invention]

[0005] Here, conventional motor cooling using refrigerants involves thermal contact with the motor surface, such as immersion, and requires a large amount of refrigerant to sufficiently cool the iron to cause low-temperature embrittlement, resulting in high processing costs. Furthermore, in conventional technologies such as those described in Patent Document 1, the motors targeted for separation and recovery are small motors, such as those used in household electrical appliances. However, drive motors for electric vehicles, for example, are large motors with outputs exceeding 200 kW. When large motors are targeted for separation and recovery, the increase in processing costs becomes even more pronounced. Furthermore, larger equipment, such as crushers, is required, resulting in issues of increased initial investment and running costs.

[0006] In view of the above circumstances, an object of the present disclosure is to provide a motor recycling method that enables removal of reusable parts while reducing the number of steps. [Means for solving the problem]

[0007] (1) A motor recycling method according to an embodiment of the present disclosure includes: a crushing step of crushing the motor; The method includes a cooling step, which is performed before the crushing step, of cooling the motor core by passing a liquid or gaseous coolant through a coolant flow path of the motor.

[0008] (2) As one embodiment of the present disclosure, in (1), The motor has a configuration in which the motor core is fixed to a casing by shrink fitting.

[0009] (3) As an embodiment of the present disclosure, in (1) or (2), The electromagnetic steel sheet used in the motor core has a layer containing 3.6% or more of Si by mass from the surface layer to a depth of 1 / 4 of the entire sheet thickness.

[0010] (4) As an embodiment of the present disclosure, in any one of (1) to (3), The outer periphery of the motor core is joined by welding. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to provide a motor recycling method that enables removal of reusable parts while reducing the number of steps. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating the structure of a motor that is a target of a motor recycling method according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is another view of the motor of FIG. [Figure 3] FIG. 3 is a flowchart showing the process of a motor recycling method according to an embodiment of the present disclosure. [Figure 4] FIG. 4 is a diagram for explaining the crushing of the motor core. [Figure 5] FIG. 5 is a diagram showing the dimensions and shape of the motor core of the embodiment. [Figure 6] FIG. 6 is a diagram showing another example of the shape of the motor core of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, a motor recycling method according to an embodiment of the present disclosure will be described with reference to the drawings.

[0014] FIG. 1 is a diagram illustrating the structure of a motor targeted by the motor recycling method according to this embodiment. In the following description, the motor targeted by the motor recycling method according to this embodiment will be simply referred to as the "target motor." The target motor has a refrigerant flow path. The refrigerant flow path is a flow path through which a liquid or gaseous refrigerant flows during use of the motor to increase the motor's thermal tolerance. In other words, the target motor is a motor that can be cooled by a refrigerant during use, including water-cooled motors and air-cooled motors. For example, relatively large motors, such as automobile drive motors, are structured with a refrigerant flow path to ensure stable operation of the automobile. Furthermore, for example, if the target motor is a water-cooled motor, the refrigerant flow path is a cooling water channel. The motor recycling method according to this embodiment includes a crushing process in which the target motor is crushed, and a cooling process, which occurs before the crushing process, in which a liquid or gaseous refrigerant flows through the refrigerant flow path of the target motor to cool the motor's iron core.

[0015] In the example shown in FIG. 1, the motor's refrigerant flow path is provided in a casing (housing) that houses the motor core. The motor core includes a rotor and a stator. In a motor with this structure, the motor core is cooled by the refrigerant cooling the casing. Therefore, welding the outer periphery of the motor core is preferable because it cools the motor core more effectively. The motor in question is not particularly limited in structure as long as it has a refrigerant flow path. In the example shown in FIG. 1, however, the motor is configured with magnetic steel sheets laminated by caulking or adhesive. The refrigerant flow path has an inlet and an outlet. FIG. 2 is a front view of the entire motor shown in FIG. 1. As shown in FIG. 2, the refrigerant introduced into the refrigerant flow path from the inlet passes through the casing and exits from the outlet. The refrigerant may loop around the casing one or more times. In the motor recycling method according to this embodiment, the refrigerant used to cool a motor can be recovered from the outlet of the refrigerant flow path and reused. If the motor in question is an interior permanent magnet synchronous motor (IPMSM), it is desirable to demagnetize the magnets in advance using a known method. For example, demagnetization can be achieved by maintaining the motor at a temperature of 300°C. For example, the time it takes for the magnets in the rotor to be sufficiently heated varies depending on the motor's size and thermal conductivity. Therefore, the demagnetization maintenance time can be adjusted depending on the motor's size and thermal conductivity.

[0016] In the motor recycling method according to this embodiment, the shredding process may be performed by introducing the refrigerant into the refrigerant flow path and then placing the motor in a crusher. A rotary hammer-type crusher is preferably used in the shredding process. However, as mentioned above, due to the increased initial investment and running costs, it may not be possible to use large-scale facilities equipped with a crusher capable of handling large motors. In such cases, the motor core must be crushed and downsized before being placed in the crusher. The crushing of the motor core before being placed in the crusher is hereinafter referred to as "pre-crushing." In pre-crushing, the motor core is crushed and downsized by applying impact force in the radial direction of the motor core. Here, the motor casing is often made of an aluminum alloy. The casing does not become embrittled due to a decrease in temperature, so it remains unshattered. However, the casing from which the motor core has been removed can be easily crushed. The materials after crushing may be separated using known methods. For example, separation may be performed based on differences in magnetic properties or specific gravity.

[0017] In this embodiment, a portion of the refrigerant flow path is in contact with the outer periphery of the motor core, and the refrigerant flow path is used to effectively cool the outer periphery of the motor core. Here, it is sufficient for the motor core to be cooled and crushed to a degree that allows it to be fed into a crusher. Therefore, it is not necessary to cool the motor core all the way to the tips of the teeth, which reduces the amount of refrigerant required for cooling.

[0018] 3 is a flowchart showing the processing of the motor recycling method according to this embodiment. A motor is removed from an electrical appliance, an automobile, or the like by a sorting machine in a recycling facility (step S1). In step S1, motors to be subjected to the motor recycling method according to this embodiment may be selected. That is, only motors having a refrigerant flow path may be selected by a known method (for example, an identification method based on photographed images), and the processing from step S2 onward may be performed on the selected motors. In selecting motors, motors having welded outer peripheries of the motor cores, motors in which the motor cores are fixed by shrink fitting, or types with a Si content equal to or greater than a predetermined value may be selected.

[0019] The motor removed in step S1 is cooled with a refrigerant through the refrigerant flow path (step S2, cooling process). Cooling is performed with the required amount of refrigerant for the required time so that the temperature of the motor core decreases and embrittles. The required amount of refrigerant and the required time may vary depending on the type of motor, and may be determined, for example, through experiments conducted in advance on multiple types of motors. The refrigerant is not limited to a specific type as long as it can cool the motor core. However, nitrogen (liquid nitrogen), which is inert and inexpensive, is preferred. The ultimate cooling temperature required to induce brittle fracture depends on the material of the motor core and the characteristics of the crusher. However, for example, cooling the yoke portion of the motor core to a temperature of -100°C is sufficient for crushing in a crusher. From the perspective of crushability, a lower ultimate cooling temperature is preferable, but the amount of refrigerant increases. Therefore, the required cooling temperature may be adjusted based on experimental results, as described above.

[0020] The motor whose core has been cooled in step S2 is then mechanically crushed (step S3, crushing step). The crushing step includes crushing the motor by placing it in a crusher. The crushing step may also include the preliminary crushing step described above.

[0021] After crushing in step S3, each material is sorted and separated for recovery (step S4). This type of recycling process can be at least partially mechanized, and does not require many steps, such as manually separating the wire from the recyclable material, reducing the number of steps compared to conventional techniques.

[0022] FIG. 4 is a diagram illustrating the crushing (particularly preliminary crushing) of a motor core. In the example of FIG. 4, a motor core made of an aluminum alloy (A5056) and fixed by shrink fitting is cooled by introducing 1.0 L of liquid nitrogen into the coolant flow path, and an impact force is applied to the outer periphery, crushing the yoke portion. In the motor recycling method according to this embodiment, it is preferable that the yoke portion is cooled preferentially over other portions in the cooling process. By sufficiently cooling the yoke portion and crushing the motor core through brittle fracture of the yoke portion, efficient miniaturization is achieved. As shown in FIG. 4, once the motor is crushed to a certain size, it can be easily processed using a relatively small crusher. Here, it is preferable that the target motor has a configuration in which the motor core is fixed to the casing by shrink fitting. This is because the impact force required for preliminary crushing is small. In other words, the shrink fit applies greater stress to the material, making it possible to perform preliminary crushing with a smaller impact force. For efficient processing, for example, in step S1, a motor having a configuration in which a motor core is fixed to a casing by shrink fitting may be selected as the target motor.

[0023] Furthermore, the electromagnetic steel sheet used in the motor core may have a layer containing 3.6% or more Si, by mass, from the surface layer to a depth of 1 / 4 of the total thickness. Motors including motor cores made of such electromagnetic steel sheets are particularly suitable for the motor recycling method according to this embodiment, since embrittlement is effectively promoted by the cooling process. More preferably, the electromagnetic steel sheet has a layer containing 4.0% or more Si. Furthermore, the electromagnetic steel sheet has a layer containing 6.5% or more Si. Suitable electromagnetic steel sheets having a Si gradient in the thickness direction include JNHF (registered trademark, manufactured by JFE Steel) and JNRF (registered trademark, manufactured by JFE Steel). The difference between the average Si content from the surface layer to a depth of 1 / 4 of the total thickness of the motor core and the average Si content at the center of the thickness (i.e., the lattice constant difference) promotes fracture due to internal stress in the material. Therefore, motor core materials having a Si gradient exhibit good fracture resistance regardless of their manufacturing process. For example, a gradient in the Si concentration distribution in the sheet thickness direction may be achieved by siliconizing using a CVD method, or a steel sheet with a different Si concentration may be obtained by a cladding method. Here, the Si gradient refers to the gradient of the Si concentration distribution. The sheet thickness center refers to the center of the motor core in the sheet thickness direction. The average Si content at the sheet thickness center is obtained by averaging the Si content from the surface layer to a depth of 1 / 4 to 3 / 4 of the entire motor core in the sheet thickness direction. In contrast, the average Si content from the surface layer to a depth of 1 / 4 of the entire motor core in the sheet thickness direction is hereinafter referred to as the average Si content in the surface layer. The Si content is determined by the Si content per unit mass of the electrical steel sheet, i.e., the Si concentration. There are no restrictions on the contained elements other than Si. For example, the presence or absence of an insulating coating on the surface does not affect the effectiveness of the motor recycling method according to this embodiment. The difference between the average Si content in the surface layer and the average Si content at the sheet thickness center is preferably 1.0% or more. More preferably, this difference is 1.5% or more. Here, even if elements are added to the electrical steel sheet unavoidably or for the purpose of improving the magnetic properties or mechanical properties, the effects of the present invention can be obtained as long as the above requirements are met.

[0024] As described above, the motor recycling method according to this embodiment makes it possible to remove reusable parts while reducing the number of steps compared to conventional techniques. Furthermore, the motor recycling method according to this embodiment can be implemented without introducing large-scale crushing equipment, making it possible to suppress increases in initial investment and running costs.

[0025] The effects of the present disclosure will be specifically explained below based on examples (experimental examples), but the present disclosure is not limited to these examples.

[0026] Example 1 Example 1 shows an example of processing and motor structure. A motor with the dimensions shown in Figure 5 was prototyped under the conditions shown in Table 1, and the crushability of the prototype motor was evaluated using various methods. Of numbers 1 to 6, numbers 1 and 2 are comparative examples based on conventional technology, and numbers 3 to 6 are examples of the invention using the method of this embodiment.

[0027] [Table 1]

[0028] The motor core had a stack thickness of 150 mm. The motor core was shrink-fitted into an aluminum alloy casing. The treated motor had a water jacket cooling mechanism (i.e., a cooling water channel) using cooling water. The motor core used an electromagnetic steel sheet containing 3.31% Si by mass. The motor core was punched and crimped. The motor was crushed under the processing conditions listed in Table 1, and the average weight of the fragments from the motor core was evaluated. The smaller this value, the finer the motor core was crushed, indicating that subsequent separation and recovery was easier. As shown in Table 1, when crushing was performed without cooling with a refrigerant (No. 1), it was difficult to separate and recover each material. On the other hand, when cooling was performed with liquid nitrogen refrigerant (Nos. 2 to 6), the motor core was crushed sufficiently finely and separated from the copper windings. Here, in the comparative example (No. 2), in which the entire motor was simply immersed in liquid nitrogen, a large amount of liquid nitrogen was required to crush the motor. In contrast, in the invention examples (Nos. 3 to 6), in which the crushing process was performed using the motor's refrigerant flow path, the motor core was crushed into sufficiently small pieces compared to conventional techniques while reducing the amount of liquid nitrogen used. The motor No. 5, which was the subject of the study, had a welded joint on the outer periphery of the motor core. In No. 5, the welding is thought to have promoted thermal conduction between the laminated electromagnetic steel sheets, confirming good crushability with a smaller amount of liquid nitrogen used. Comparing No. 3 and No. 6, it was confirmed that the motor core could be effectively crushed with a smaller amount of liquid nitrogen when the motor core was fixed to the casing by shrink-fitting rather than bolting. Here, the motor core fixed by bolts was a so-called motor core with lugs, as shown in Figure 6. Furthermore, in No. 4, a preliminary crushing process was performed by applying a striking force in the radial direction of the motor after cooling with a refrigerant, and the motor core was crushed using a small crusher. The preliminary crushing force was applied using a hammer. The average weight of the crushed pieces in No. 4 confirmed that the motor core could be crushed into sufficiently small pieces without using a large crusher. In this way, it was confirmed that by using the method of this embodiment, it is possible to remove reusable parts without requiring many steps, such as manually separating them from the windings.

[0029] Example 2 Example 2 shows an example of an electromagnetic steel sheet. In Example 2, electromagnetic steel sheets used as motor core materials were evaluated. Motors of the same shape as Example 1 (FIG. 5) were manufactured using electromagnetic steel sheets of different grades. The electromagnetic steel sheets having a silicon gradient in the thickness direction were siliconized to obtain the properties shown in Table 2 (the average silicon content in the surface layer and the average silicon content in the thickness center). The average silicon content in the surface layer and the average silicon content in the thickness center were evaluated by EPMA analysis. The motor cores were punched and crimped. As shown in Table 2, for motors Nos. 7 to 14, liquid nitrogen was introduced into the refrigerant flow path, and then the motors were crushed by placing them in a large crusher, and evaluated in the same way as Example 1. Nos. 7 to 14 are all examples of the invention using the method of this embodiment, but differ in the silicon content of the electromagnetic steel sheets and whether or not they have a silicon gradient.

[0030] [Table 2]

[0031] It was observed that the greater the Si content in the electrical steel sheet, the finer the crushed pieces tended to be. Here, the Si content of the electrical steel sheet in Table 2 is the average Si concentration (mass%) across the entire sheet thickness. For materials with a Si concentration distribution in the sheet thickness direction (materials with a "Si gradient" in the "Yes" column), the average Si concentration across the entire sheet thickness, as well as the average Si concentrations at the surface and the center of the sheet thickness, are shown. Comparing the average weight of crushed pieces for Nos. 7-9 and Nos. 10-12 in Table 2, it was confirmed that significantly higher crushability was achieved when the Si content was 3.6% or higher. Furthermore, materials with a Si gradient in the thickness direction of the electrical steel sheet (Nos. 13 and 14) exhibited better crushability than materials without a Si gradient. Comparing Nos. 9 and 13, which have the same Si content, the material with a Si gradient in the thickness direction exhibited significantly higher crushability.

[0032] According to the present disclosure, it is possible to realize a motor recycling method for separating and recovering the constituent materials of relatively large motors such as automobile drive motors, without necessarily introducing a large crusher or requiring a large amount of refrigerant. This motor recycling method can achieve highly efficient separation and recovery at low cost, and is highly useful industrially, particularly for relatively large motors (e.g., motors with an output of over 200 kW) used for driving automobiles.

[0033] Although the embodiments of the present disclosure have been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications or alterations based on the present disclosure, and therefore, it should be noted that these modifications and alterations are included within the scope of the present disclosure.

Claims

1. a crushing step of crushing the motor; a cooling step of cooling the motor core by passing a liquid or gaseous refrigerant through a refrigerant flow path of the motor before the crushing step.

2. 2. The motor recycling method according to claim 1, wherein the motor has a configuration in which the motor core is fixed to a casing by shrink-fitting.

3. 3. The motor recycling method according to claim 1, wherein the electromagnetic steel sheet used for the motor core has a layer containing 3.6% or more Si, in mass %, from the surface layer to a depth of one-quarter of the total thickness in the sheet thickness direction.

4. 3. The motor recycling method according to claim 1, wherein the outer periphery of the motor core is joined by welding.

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