Motor core manufacturing method and motor core

Abstract

To provide a manufacturing method of a motor core capable of manufacturing a motor core close to a material iron loss by appropriate acid processing, and a motor core manufactured by the manufacturing method.SOLUTION: A manufacturing method of a motor core manufactures a motor core from a block core formed from laminated thin plates. The method includes: a cutting step of processing the block core into a desired motor core shape by cutting using fusion; and an acid processing step of bringing the motor core into an acid bath solution. In the acid processing step, an iron loss of the motor core is measured.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to a method for manufacturing a motor core and to a motor core. [Background technology]

[0002] In recent years, the adoption of electric vehicles has been expanding from the perspective of reducing CO2 emissions. This electrification is spreading not only to the automotive sector but also to various industries and products, and there is an increasing demand for the development of highly efficient motors. In order to achieve higher motor efficiency than conventional technology, it is necessary to repeatedly prototype and evaluate various motor designs and materials, and to search for motors with lower energy loss.

[0003] In recent years, advances in motor characteristic analysis techniques such as finite element analysis have led to a decrease in the number of trials required for motor prototype evaluation; however, prototype evaluation remains necessary. During the motor design planning stage, manufacturing molds is often impractical due to cost or delivery time considerations. For example, during the motor design planning stage, the motor core (iron core), one of the components of a motor, is frequently prototyped using laser cutting or wire electrical discharge machining.

[0004] However, in the prototype evaluation of such motor cores, there is a problem in that the inherent properties of the core material may not be realized due to the effects of processing. For example, in some cases, a motor core is manufactured by performing wire electrical discharge machining as a cutting process on a block core that has been pre-bonded and laminated with electrical steel sheets. In this case, welding may occur between the laminated electrical steel sheets at the processed end face. This causes a short circuit between the laminates, which can generate very large eddy currents when magnetic flux is generated in the motor core. The increase in eddy current loss can cause the iron loss of the motor core to be more than twice that of the material, which can lead to inaccurate motor prototyping and performance evaluation. In motor cores affected by such short circuits, even if a low-iron-loss core material is used, the iron loss in the motor may be large, and the effect of increased efficiency due to the low iron loss of the material may not be realized.

[0005] To prevent such short circuits at the end faces, one method involves clamping the block cores together and performing wire electrical discharge machining without bonding them, then peeling them off one by one after machining and bonding them together again. However, this method significantly increases the man-hours required for prototyping motor cores. In particular, electromagnetic steel sheets or amorphous materials used as core materials for high-efficiency motors are often thin, leading to a massive increase in man-hours. As a result, the manufacturing cost of prototype motors increases, and the development period for high-efficiency motors lengthens.

[0006] Another method to eliminate short circuits at the end faces of motor cores is, for example, Patent Document 1, which describes performing wire electrical discharge machining underwater on an amorphous block core that has been bonded and laminated. By machining underwater, the amorphous molten material can be thinly and uniformly deposited over almost the entire surface of the cut surface, and then almost only the amorphous molten material can be removed by etching. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2008-198898 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, the core material is not limited to amorphous materials; various thin sheet materials other than amorphous materials, such as electrical steel sheets (Fe-Si alloy), Permendur (Fe-Co alloy), and Permalloy (Fe-Ni alloy), are used. When using thin sheet materials other than amorphous materials, it is difficult to obtain the same effect as in the case of amorphous materials even if the technology described in Patent Document 1 is used. Therefore, there is a need for a technology that can eliminate the increase in iron loss due to short circuits at the end faces of the motor core, without being limited to amorphous materials.

[0009] In view of these circumstances, the purpose of this disclosure is to provide a method for manufacturing a motor core that can produce a motor core with iron loss close to that of the raw material by appropriate acid treatment, and a motor core manufactured by this method. [Means for solving the problem]

[0010] (1) A method for manufacturing a motor core according to one embodiment of the present disclosure is: A method for manufacturing a motor core from a block core formed of laminated thin plates, A cutting step in which the block core is processed into a desired motor core shape by cutting by melting, The process includes an acid treatment step in which the motor core is brought into contact with an acid bath solution, During the acid treatment process, the iron loss of the motor core is measured.

[0011] (2) As one embodiment of the present disclosure, in (1), The excitation conditions for the iron loss measurement are adjusted so that the magnetostriction of the material constituting the motor core is 3.0 ppm or more.

[0012] (3) In one embodiment of the present disclosure, in (1) or (2), The acid bath solution used in the aforementioned acid treatment process contains 15% to 90% phosphoric acid by mass fraction.

[0013] (4) As one embodiment of the present disclosure, in any one of (1) to (3), the cutting step cuts the block core by wire electrical discharge machining.

[0014] (5) The motor core according to one embodiment of the present disclosure is a motor core manufactured by the manufacturing method of the motor core according to any one of (1) to (4), in the acid treatment step, the iron loss evaluation value at 1.0 T and 400 Hz for the single sheet of the thin plate is P (W / kg), and the iron loss of the motor core is P C (W / kg), and acid treatment is performed until 1.0 ≦ P C / P SS ≦ 1.3 is satisfied.

Advantages of the Invention

[0015] [[ID=**27**]]According to the present disclosure, it is possible to provide a method for manufacturing a motor core capable of manufacturing a motor core close to the material iron loss by appropriate acid treatment, and a motor core manufactured by the manufacturing method.

Brief Description of the Drawings

[0016] [[]END]] [Figure 1] FIG. 1 is a schematic diagram of the acid treatment step. [Figure 2] FIG. 2 is a diagram showing one motor core shape (A). [Figure 3] FIG. 3 is a diagram showing another motor core shape (B). [Figure 4] FIG. 4 is a diagram illustrating the change in iron loss due to acid treatment. [Figure 5] FIG. 5 is a diagram illustrating the comparison of iron loss before and after acid treatment. [Figure 6] FIG. 6 is a diagram for explaining λp-p, and is a diagram showing an example of the measurement result of magnetic strain.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, a motor core manufacturing method and a motor core manufactured by the manufacturing method according to one embodiment of the present disclosure will be described with reference to the drawings. The motor core manufacturing method according to this embodiment manufactures a motor core from a block core formed of laminated thin plates. The motor core manufacturing method comprises a step of processing the block core into a desired motor core shape by cutting by melting (cutting step) and a step of bringing the motor core into contact with an acid bath (acid treatment step), characterized in that the iron loss of the motor core is measured in the acid treatment step (with the acid bath applied to at least the molten surface). The configuration and steps described below are examples. The present disclosure is not limited to the configuration and steps described below. For example, similar effects can be obtained by using any equipment that can perform the necessary processing.

[0018] As described above, the method for manufacturing a motor core according to this embodiment includes a cutting step and an acid treatment step. Figure 1 shows a schematic diagram of the acid treatment step. In the acid treatment step, an acid pickling container is used in which the motor core is immersed in an acid bath solution (hereinafter sometimes simply referred to as "acid"). The material of the acid pickling container is not limited as long as it is non-magnetic and resistant to acid, but for example, vinyl ester resin FRP (a specific example being Lipoxy H-600 manufactured by Resonaq Corporation) may be used. Also, the type of acid is not limited, and for example, hydrochloric acid, nitric acid, sulfuric acid, or phosphoric acid can be used. From the viewpoint of suppressing damage to the insulating coating of the electrical steel sheet, it is preferable that the acid bath solution used in the acid treatment step contains 15% to 90% phosphoric acid by mass fraction. In order to excite the motor core, a primary winding is applied to the acid pickling container. The number of turns of the primary winding is not limited to a specific number and can be adjusted as appropriate according to the size of the motor core, the target excitation conditions, and the power supply provided. Furthermore, to evaluate the magnetic flux density of the motor core, a secondary winding is applied to the entire pickling container. The number of turns of the secondary winding should be adjusted as appropriate to ensure a voltage sufficient for the iron loss measuring instrument (oscilloscope) to measure. Here, the primary winding, secondary winding, power supply, and iron loss measuring system including the iron loss measuring instrument do not come into contact with the acid bath. As the iron loss measuring instrument, for example, a stator core magnetic property tester DAC-LST-3 (manufactured by Soken Electric Co., Ltd.) can be used.

[0019] By adjusting the excitation conditions for iron loss measurement so that the magnetostriction of the motor core material is 3.0 ppm or more at λp-p, a better acid treatment effect can be obtained. In other words, a short-time short-circuit elimination effect can be obtained. The magnetostriction of the motor core can be measured by applying current to the primary winding with a strain gauge attached to the motor core. A strain gauge such as KFN-2-35-C9-11J30C3 (non-inductive type, manufactured by Kyowa Electric Co., Ltd.) can be used. There are no restrictions on the strain gauge used; the product should be selected considering the size of the motor core or the frequency response. The strain gauge is attached to the outer circumference of the motor core. The signal indicating the change in the strain gauge is amplified by a bridge circuit, for example, and measured with an oscilloscope. Here, λp-p, which is an indicator of the magnitude of the magnetostriction of the material, is defined as the difference between the minimum and maximum values ​​of the oscillating magnetostriction. Figure 6 is a diagram to explain λp-p and shows an example of the magnetostriction measurement result.

[0020] Next, preferred constituent elements of the motor core manufacturing method according to this embodiment will be described. Bubbles form on the surface of the motor core immersed in acid. These bubbles prevent direct contact between the acid bath and the motor core, but when the motor core vibrates due to magnetostriction, the bubbles detach from the surface, and contact between the acid bath and the motor core is restored. Therefore, the effect of promoting acid treatment by vibration can be expected. A method of promoting acid treatment by vibrating the motor core from the outside with a vibrator or the like can also be considered, but for relatively large motor cores such as drive motors for electric vehicles, it is difficult to vibrate the entire core. By using magnetostrictive vibration, the vibration source is the motor core itself, so the entire core can be easily vibrated. In addition, since bubbles are more likely to detach from the core surface due to magnetostrictive vibration, the finished surface quality is improved. Here, there is also a method of suppressing bubbles using an antifoaming agent, but this increases the cost of the treatment liquid and there is a risk of acid penetrating between the layers. Therefore, the method of using magnetostrictive vibration is preferred. From the standpoint of preventing short circuits, a higher magnetostriction in the motor core is preferable, and for example, a λp-p of 10.0 ppm or higher is even more preferable. On the other hand, a motor core with high magnetostriction may cause increased noise when assembled into a motor. Therefore, a magnetostriction of λp-p of 40.0 ppm or lower is preferable for the motor core.

[0021] As described above, it is desirable that the acid bath solution contains 15% to 90% phosphoric acid by mass fraction. At concentrations below 15%, the processing time will be longer, and there is a risk of acid penetrating between the layers. On the other hand, phosphoric acid with a concentration of 90% or more is difficult to obtain for industrial use (for example, it needs to be obtained as a pure reagent), which increases costs. In addition, the acid bath solution may contain surfactants or pickling inhibitors to improve the properties of the finished product, and may also contain organic acids (such as sulfamic acid, citric acid, malic acid, hydroxyacetic acid, and phosphonic acid) as auxiliary agents.

[0022] After acid treatment, oxides form on the surface of the motor core. As a cleaning treatment, the surface oxides can be removed using ammonium thioglycolate or the like. Here, the cleaning treatment is a procedure to make the surface clean and does not affect the iron loss of the iron core. If the remaining oxides on the surface are acceptable, in other words, if the appearance is not a problem, the cleaning treatment may be omitted.

[0023] The process of cutting the block core into the motor core shape (cutting process) can be any method that involves melting the block core and processing it into the desired shape. Examples of processing methods include laser cutting or wire electrical discharge machining. Since both methods involve melting the end faces, welding and short circuits occur. However, the residual thermal distortion after processing is smaller with wire electrical discharge machining. Therefore, wire electrical discharge machining can suppress the negative impact on iron loss. Accordingly, in order to minimize iron loss after short circuit resolution, it is preferable to cut the block core using wire electrical discharge machining in the cutting process.

[0024] In the acid treatment of a motor core with a short-circuited end face, appropriate acid treatment conditions depend not only on the pickling properties of the core material itself but also on its surface condition. If the acid treatment time is insufficient, the welded area that is causing the short circuit between the laminated materials will not be adequately treated, and the iron loss will not be recovered. On the other hand, if the acid treatment time is excessive, the dimensional changes of the motor core may occur, or the acid may penetrate between the laminates and damage the insulating coating of the laminated material. There is also a risk that the adhesive strength of the motor core will decrease. To solve these problems, the acid treatment may be performed as follows.

[0025] The motor core is regarded as a ring core to form a magnetic circuit, and a primary winding and a secondary winding are applied. During the acid treatment, the iron loss is measured in real time. If a short circuit occurs on the end face, an increase in eddy current loss occurs, resulting in a larger iron loss compared to the iron loss evaluation result of the material by the Epstein test (JIS C2550-1). The increase in iron loss due to the short circuit on the end face is mainly due to the increase in eddy current loss. As a method of separating the iron loss into hysteresis loss and eddy current loss, the so-called two-frequency method can be used. For example, by measuring the iron losses at 50 Hz and 200 Hz and specifying the value of the coefficient k using the following formula (1), the losses at any frequency can be separated.

[0026] P = Ph + Pe = kh×f + ke×f 2 Formula (1)

[0027] Here, P is the total iron loss. Ph is the hysteresis loss, and Pe is the eddy current loss. The coefficient k includes the coefficient kh for the hysteresis loss and the coefficient ke for the eddy current loss. f is the excitation frequency. The measurement of iron loss in acid can, in principle, be carried out under any conditions of frequency and magnetic flux density. However, since the eddy current loss is determined by the square of the excitation frequency, it is easier to capture the change in iron loss due to acid treatment under higher frequency conditions. For example, the measurement of iron loss at 400 Hz can be adopted. On the other hand, regarding the above-mentioned magnetic strain λp-p, the magnetic flux density condition is more dominant than the excitation frequency. Therefore, from the perspective of ensuring the magnetic strain λp-p, it is desirable to excite under a high magnetic flux density condition. However, when exciting at an excessively high magnetic flux density, a large number of turns of the primary winding needs to be set, and an excitation current due to a high voltage is required. Therefore, it is preferably set to 1.5 T or less as the magnetic flux density condition.

[0028] Regarding the iron loss evaluation value P SS (W / kg) at 1.0 T and 400 Hz in a single sheet of the thin plate constituting the motor core, the iron loss P C (W / kg) of the motor core is P C / P SSAcid treatment is performed until ≤1.3 is satisfied. By performing acid treatment in this way, motor losses due to short circuits are suppressed, and the penetration of acid between the layers is also suppressed, thereby achieving high efficiency of the motor. Here, P C The theoretical lower limit of (W / kg) is the iron loss evaluation value P SS (W / kg). Therefore, the above formula is 1.0 ≤ P C / P SS This can be replaced with ≤1.3.

[0029] The effects of this disclosure will be described in detail below based on examples, but this disclosure is not limited to these examples.

[0030] (Example 1) Motor cores with the dimensions and shapes shown in Figures 2 and 3 were fabricated using various thin sheet shapes of soft magnetic material. Figure 2 shows motor core shape "A," and Figure 3 shows motor core shape "B." Both motor core shapes have a laminate thickness of 14 mm. First, thin sheets of soft magnetic material were laminated and bonded to form a block core. Next, cutting was performed into each motor core shape using two methods. The first method was wire electrical discharge machining, where the end faces were welded and then cut by wire electrical discharge machining. The second method was laser cutting, where cutting was performed using a fiber laser (1000 W).

[0031] However, for K-MP11 (Permendur), one of the soft magnetic materials, stress-relieving annealing was performed at 850°C for 2 hours in a dry H2 atmosphere before the block core was fabricated by lamination bonding.

[0032] Table 1 shows the results of measuring the iron loss of the stator core immediately after cutting ("Iron Loss Immediately After Processing"). Although there was a correlation between the "Iron Loss Immediately After Processing" and the raw material iron loss ("Iron Loss Evaluation Value for Single Sheets"), the value of "Iron Loss Immediately After Processing" was about twice as large as the "Iron Loss Evaluation Value for Single Sheets". Furthermore, the rate of increase in iron loss due to processing into a motor core was not constant, and the way it changed differed depending on the motor core shape and material.

[0033] [Table 1]

[0034] Next, acid treatment was performed using various acids as shown in Figure 1. Figure 4 shows the change in motor core iron loss ("iron loss after acid treatment") when motor core number 4 in Table 1 was acid-treated. Motor core iron loss (W) immediately after wire electrical discharge machining. 10 / 400 The iron loss was 27.1 W / kg, but immersion in acid reduced the iron loss, showing behavior that asymptotically approached the iron loss evaluation value for a single sheet. Figure 5 shows the results of loss separation of the motor core iron loss before and after acid treatment using the two-frequency method. Before acid treatment, the motor core iron loss (W 10 / 400 Of the 27.1 W / kg of power loss, eddy current loss accounted for a significant 20.7 W / kg. However, after acid treatment, eddy current loss was reduced to 5.2 W / kg, suggesting that the short circuit caused by wire electrical discharge machining was eliminated.

[0035] Here, by monitoring the change in motor core iron loss as shown in Figure 4, the acid treatment can be performed with the appropriate acid treatment time to eliminate short circuits. The iron loss evaluation value of a single sheet of thin plate constituting the motor core at 1.0T and 400Hz is P SS P is the iron loss of the motor core, expressed as (W / kg). C (W / kg) is P C / P SS The process was carried out until the value became ≤1.3. By performing acid treatment for such a short time, it is possible to manufacture a motor core that eliminates the effects of short circuits at the end faces. Here, P C / P SS The value of may be less than 1.3, and the acid treatment time may be extended as needed until the reduction in iron loss saturates.

[0036] Table 1 shows the iron loss after acid treatment under each condition, as described above. For all materials, motor core shapes, and acid treatment conditions in Table 1, the iron loss of the motor core was improved compared to before acid treatment, and it was possible to keep it to 1.3 times or less compared to the iron loss evaluation value of the single sheet. It was confirmed that a motor core with low iron loss can be manufactured by the acid treatment method disclosed in this disclosure.

[0037] Furthermore, it was found that under conditions where the acid bath solution used in the acid treatment process contained 15% to 90% phosphoric acid by mass fraction, the achievable iron loss by acid immersion was low. For example, numbers 14 to 16 in Table 1 differ only in the phosphoric acid concentration. Compared to number 14 in Table 1, whether the acid concentration is high or low (low numbers 15 and 16), the iron loss ratio increases, and the achievable iron loss deteriorates. If the acid is too low, the acid treatment is prolonged, and it is thought that the acid that penetrates between the layers damages the insulating film. Also, if the acid concentration is too high, the reactivity of the acid increases, which also damages the insulating film, and the achievable iron loss deteriorates.

[0038] (Example 2) Six motor cores were manufactured under the same conditions as number 4 in Table 1 (material: 20JNEH1200, core shape: A, processing method: wire electrical discharge machining). The first motor core corresponds to numbers 4a and 4b. The second motor core corresponds to numbers 4c and 4d. Similarly, two numbers correspond to each motor core. Table 2 shows the iron loss after processing for each motor core. The excitation conditions of the motor cores during acid treatment ("excitation conditions for acid treatment") were changed as shown in Table 2, and the motor cores were immersed in an acid bath containing 75% phosphoric acid by mass fraction for acid treatment. Also, as shown in Table 2, for each excitation condition, the magnetostriction of the motor core was measured in advance using a strain gauge before acid treatment. Furthermore, for all acid treatment conditions, the short circuit at the end face was considered to have been removed when the iron loss of the motor core after acid treatment reached 11.3 W / kg, and the treatment time was evaluated ("acid treatment time"). When the magnetostriction exceeded 3.0 ppm, the acid treatment time was shortened. It is thought that bubbles that inhibit the acid treatment were detached from the motor core by magnetostrictive vibration, accelerating the acid treatment and enabling short-circuit removal in a short time. As described above, short-circuit removal in a short time is possible by exciting the motor core under conditions where the magnetostriction is large.

[0039] [Table 2]

[0040] As described in the examples, the motor core manufacturing method according to this embodiment can suppress the increase in iron loss due to short circuits at the end faces that occur during the processing of the motor core shape by performing an appropriate acid treatment in a relatively short time. Therefore, it is possible to manufacture a motor core with reduced iron loss. Furthermore, the motor core manufacturing method according to this embodiment has high industrial application value because it can be applied to the development or mass production of high-efficiency motors.

[0041] While embodiments of this disclosure have been described based on the drawings and examples, it should be noted that those skilled in the art will find it easy to make various modifications or alterations based on this disclosure. Therefore, it should be noted that these modifications or alterations are included within the scope of this disclosure. For example, the functions included in each component or step can be rearranged in a logically consistent manner, and multiple components or steps can be combined into one or divided. Embodiments relating to this disclosure can also be realized as programs executed by a processor in the device or as storage media recording such programs. These should also be understood to be included within the scope of this disclosure.

Claims

1. A method for manufacturing a motor core from a block core formed of laminated thin plates, A cutting step in which the block core is processed into a desired motor core shape by cutting by melting, The process includes an acid treatment step in which the motor core is brought into contact with an acid bath solution, In the aforementioned acid treatment process, the iron loss of the motor core is measured. A method for manufacturing a motor core, wherein the excitation conditions for measuring iron loss are adjusted so that the magnetostriction of the material constituting the motor core is 3.5 ppm or more and 12.6 ppm or less in λp-p, which is defined as the difference between the minimum and maximum values ​​of the oscillating magnetostriction.

2. The method for producing a motor core according to claim 1, wherein the acid bath solution used in the acid treatment step contains 15% to 90% phosphoric acid by mass fraction.

3. The method for manufacturing a motor core according to claim 1 or 2, wherein the cutting step involves cutting the block core by wire electrical discharge machining.

4. A motor core manufactured by the motor core manufacturing method described in claim 1 or 2, In the acid treatment process, the iron loss evaluation value of the single sheet of the thin plate at 1.0T and 400Hz is P ＳＳ P is the iron loss of the motor core, expressed as (W / kg). Ｃ (W / kg) is 1.0 ≤ P Ｃ / P ＳＳ A motor core that is acid-treated until the temperature is ≤ 1.3.

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