Manufacturing method of motor core 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] The present disclosure relates to a method for manufacturing a motor core and a motor core.

Background Art

[0002] In recent years, the popularity of electric vehicles has been expanding from the perspective of suppressing CO 2 emissions. Such electrification has spread to various industries and products not limited to the automotive field, and there is an increasing demand for the development of more efficient motors. In order to achieve a higher motor efficiency than the prior art, it is necessary to repeat prototyping and evaluation for various motor designs or materials to search for a motor with less energy loss.

[0003] In recent years, due to the progress of motor characteristic analysis technologies such as finite element method analysis, the number of trial runs for prototype evaluation of motors has been on a decreasing trend, but still, evaluation by prototyping is necessary. In the prototype evaluation at the stage of considering motor design, it is not realistic to produce a mold from the perspective of cost or delivery time. At the stage of considering motor design, for example, a motor core (iron core), which is one of the elements constituting a motor, is often prototyped by a processing method such as laser cutting (laser cutting) or wire cutting (wire electrical discharge machining).

[0004] However, in the prototype evaluation of such a motor core, there is a problem that the original characteristics of the core material may not be exhibited due to the influence of processing. For example, when manufacturing a motor core by performing wire electrical discharge machining as a cutting process on a block core in which electromagnetic steel sheets are adhesively laminated in advance, welding may occur between the electromagnetic steel sheets laminated at the machining end face. As a result, a short circuit may occur between the laminations, and when magnetic flux is generated in the motor core, a very large eddy current may be generated. Due to the increase in eddy current loss, for example, the iron loss of the motor core may be more than twice that of the material, which may cause incorrect prototype production and characteristic evaluation of the motor. In such a motor core affected by short circuit, even though a low-iron-loss core material is used, the iron loss in the motor may increase, and the effect of high efficiency due to the reduction of iron loss in the material may not be enjoyed.

[0005] As a measure to prevent such short circuit at the end face, there is a method of performing wire electrical discharge machining in a clamped state without adhesively laminating the block core, peeling off one by one after machining, and then adhesively laminating again. However, the man-hours in the prototype production of the motor core become extremely large. In particular, electromagnetic steel sheets or amorphous materials used as core materials for high-efficiency motors often have a thin plate thickness, resulting in extremely large man-hours. As a result, the manufacturing cost of the prototype motor increases, and the development period of the high-efficiency motor becomes longer.

[0006] As another method to eliminate the short circuit at the end face of the motor core, for example, Patent Document 1 performs wire electrical discharge machining in water on an adhesively laminated amorphous block core. By machining in water, the melt of the amorphous can be thinly and uniformly adhered to almost the entire cutting surface, and by etching, almost only the melt of the amorphous can be removed.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

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

[0009] In view of such circumstances, an object of the present disclosure is 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.

Means for Solving the Problems

[0010] (1) A method for manufacturing a motor core according to an embodiment of the present disclosure is a method for manufacturing a motor core from a block core formed by laminated thin plates, including a cutting step of processing the block core into a desired motor core shape by cutting with melting, and an acid treatment step of bringing the motor core into contact with an acid bath solution, and iron loss measurement of the motor core is performed in the acid treatment step.

[0011] (2) As an 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) As an embodiment of the present disclosure, in (1) or (2), the acid bath solution used in the acid treatment step contains phosphoric acid with a mass fraction of 15% to 90%.

[0013] (4) As one embodiment of the present disclosure, in any one of (1) to (3), In the cutting step, the block core is cut 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 SS (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] According to the present disclosure, it is possible to provide a manufacturing method of 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]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0017] Hereinafter, a method for manufacturing a motor core according to an embodiment of the present disclosure and a motor core manufactured by the manufacturing method will be described with reference to the drawings. The method for manufacturing a motor core according to this embodiment manufactures a motor core from a block core formed of laminated thin plates. The method for manufacturing a motor core includes a step of processing the block core into a desired motor core shape by cutting with melting (cutting step), and a step of bringing the motor core into contact with an acid bath solution (acid treatment step). In the acid treatment step, iron loss measurement of the motor core is performed (at least in a state where the acid bath solution is applied to the cut surface). The configurations and steps described below are examples. The present disclosure is not limited to the configurations and steps described below. For example, the same effect can be obtained using any instrument as long as it can execute 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. FIG. 1 shows a schematic diagram of the acid treatment step. In the acid treatment step, a pickling container in which an acid bath solution (hereinafter sometimes simply referred to as "acid") is stored and the motor core is immersed is used. The material of the pickling container is not limited as long as it is non-magnetic and resistant to acid. For example, vinyl ester resin FRP (specific example: Lipoxy H-600 manufactured by Resona Co., Ltd.) 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 film of the electromagnetic steel sheet, it is preferable that the acid bath solution used in the acid treatment step contains phosphoric acid with a mass fraction of 15% to 90%. In order to excite the motor core, a primary winding is applied to the pickling container as a whole. The number of turns of the primary winding is not limited to a specific number, and may be appropriately adjusted according to the size of the motor core, the target excitation conditions, and the power supply prepared. Also, in order to evaluate the magnetic flux density of the motor core, a secondary winding is applied to the pickling container as a whole. Regarding the number of turns of the secondary winding, appropriate adjustment may be made to ensure a voltage sufficient for voltage measurement by an iron loss measuring instrument (oscilloscope). Here, the iron loss measurement system including the primary winding, secondary winding, power supply, and iron loss measuring instrument does not come into contact with the acid bath solution. Here, as the iron loss measuring instrument, for example, a stator core magnetic characteristic test device 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 material constituting the motor core is 3.0 ppm or more in terms of λp-p, a better acid treatment effect can be obtained. That is, a short-circuit elimination effect in a short time can be obtained. The magnetostriction of the motor core can be measured by energizing the primary winding with a strain gauge attached to the motor core. As the strain gauge, for example, KFN-2-35-C9-11J30C3 (non-inductive type, manufactured by Kyowa Electronic Instruments Co., Ltd.) can be used. There is no restriction on the strain gauge to be used, and the product may be selected in consideration of the size of the motor core or the frequency responsiveness. The strain gauge is attached to the outer peripheral portion of the motor core. A signal indicating a change in the strain gauge is amplified by, for example, a bridge circuit and measured with an oscilloscope. Here, λp-p, which is an index of the magnitude of the magnetostriction of the material, is defined as the difference between the minimum value and the maximum value of the vibrating magnetostriction. FIG. 6 is a diagram for explaining λp-p and shows an example of the measurement result of magnetostriction.

[0020] Next, the preferable constituent requirements in the manufacturing method of the motor core according to the present embodiment will be described. Bubbles are generated on the surface of the motor core immersed in the acid. The bubbles prevent direct contact between the acid bath solution and the motor core. However, when the motor core vibrates due to magnetostriction, the bubbles deviate from the surface, and the contact between the acid bath solution and the motor core is restored. Therefore, the effect of promoting the acid treatment by vibration can be expected. Although a method of vibrating the motor core by an external vibrator or the like to promote the acid treatment can be considered, it is difficult to vibrate the entire core in a relatively large motor core such as a drive motor for an electric vehicle. By using magnetostrictive vibration, since the vibration source is the motor core itself, the entire core can be easily vibrated. In addition, since the bubbles are likely to separate from the core surface due to magnetostrictive vibration, the surface quality of the finish is improved. Here, there is also a method of suppressing bubbles using an antifoaming agent, but the cost of the treatment liquid increases, and there is a risk that acid may penetrate between the layers. Therefore, the method using magnetostrictive vibration is preferable. From the viewpoint of the short-circuit treatment, the larger the magnetostriction of the motor core, the more preferable it is. For example, it is more preferable that λp-p is 10.0 ppm or more. On the other hand, there is a concern that a motor core with large magnetostriction may generate more noise when assembled as a motor. Therefore, the magnetostriction of the motor core is preferably 40.0 ppm or less in terms of λp-p.

[0021] As described above, it is desirable that the acid bath solution contains phosphoric acid with a mass fraction of 15% to 90%. When the concentration is 15% or less, the treatment time becomes long, and there is a risk that acid may penetrate between the layers. On the other hand, phosphoric acid with 90% or more is difficult to obtain industrially (for example, it is necessary to obtain it as a pure reagent), resulting in an increase in cost. In addition, the acid bath solution may contain a surfactant or an acid pickling inhibitor in order to improve the properties of the finish, and may additionally contain an organic acid (such as sulfamic acid, citric acid, malic acid, hydroxyacetic acid, phosphonic acid).

[0022] After the acid treatment, an oxide is formed on the surface of the motor core. As a cleaning treatment, the surface oxide can be removed with ammonium thioglycolate or the like. Here, the cleaning treatment is a process for finishing the surface neatly and does not affect the iron loss of the core. If the remaining oxide on the surface can be tolerated, in other words, if the appearance is not a problem, the cleaning treatment may be omitted.

[0023] The step of cutting into the motor core shape (cutting step) may be any method of melting the block core and processing it into a desired shape. Examples of the processing method include laser cutting or wire electrical discharge machining. Since both are processes that melt the end face, welding and short circuits occur. Here, the residual thermal strain after processing is smaller in wire electrical discharge machining. Therefore, wire electrical discharge machining can suppress the adverse effect on iron loss. Therefore, in order to reduce the iron loss after eliminating the short circuit, it is preferable to cut the block core by wire electrical discharge machining in the cutting step.

[0024] Here, in the acid treatment of the motor core with a short-circuited end face, appropriate acid treatment conditions depend not only on the pickling property of the core material itself but also on the surface state. If the acid treatment time is insufficient, sufficient treatment of the welded part short-circuiting between the laminated materials is not performed, and the iron loss does not recover. On the other hand, if the acid treatment time becomes excessive, there is a risk that the dimensions of the motor core will change, or that acid will penetrate between the laminations and damage the insulating film of the laminated material. There is also a risk that the adhesive strength of the motor core will decrease. To solve such problems, the acid treatment may be performed as follows.

[0025] Regarding the motor core as a ring core to form a magnetic circuit, a primary winding and a secondary winding are provided, and iron loss is measured in real time during acid treatment. When a short circuit occurs at the end face, since an increase in eddy current loss occurs, the iron loss is large when compared with 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 at the end face is mainly due to the increase in eddy current loss. As a method for separating iron loss into hysteresis loss and eddy current loss, the so-called two-frequency method can be used. For example, by measuring the iron loss at 50 Hz and 200 Hz and specifying the value of the coefficient k using the following formula (1), the loss at an arbitrary frequency can be separated.

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

[0027] Here, P is all the 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, since the above-mentioned magnetic strain λp-p is dominated by the magnetic flux density condition rather than the excitation frequency, it is desirable to excite under a high magnetic flux density condition from the viewpoint of ensuring the magnetic strain λp-p. However, when exciting at an excessively high magnetic flux density, the number of turns of the primary winding is set large, 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 SSThe acid treatment is carried out until it satisfies ≦1.3. By carrying out such acid treatment, the motor loss due to short - circuit can be suppressed, and the intrusion of acid between laminations can also be suppressed, thereby achieving high efficiency of the motor. Here, P C (W / kg) is the theoretical lower limit value, which is the iron loss evaluation value P SS (W / kg). Therefore, the above formula can be replaced with 1.0 ≦ P C / P SS ≦1.3.

[0029] Hereinafter, the effects of the present disclosure will be specifically described based on examples, but the present disclosure is not limited to these examples.

[0030] (Example 1) Using various thin - plate - shaped soft magnetic materials, motor cores with the dimensional shapes shown in FIGS. 2 and 3 were fabricated. FIG. 2 shows the motor core shape "A". Also, FIG. 3 shows the motor core shape "B". The lamination thickness of both motor core shapes is 14 mm. First, thin plates of the soft magnetic material were laminated, and a block core was formed by lamination adhesion. Next, cutting processes for each motor core shape were performed in two ways. The first processing method is wire - cut electrical discharge machining, where the end faces were welded and then cut by wire - cut electrical discharge machining. The second processing method is laser cutting, which was cut by a fiber laser (1000 W).

[0031] However, for K - MP11 (Permendur) among the soft magnetic materials, before the block core was fabricated by lamination adhesion, stress - relieving annealing was carried out at 850 °C for 2 hours in a dry H 2 atmosphere.

[0032] Table 1 shows each manufactured motor core and includes the result of measuring the iron loss of the stator core immediately after cutting (the "iron loss immediately after processing"). The "iron loss immediately after processing" showed an alternation between the material iron loss (the "iron loss evaluation value for a single plate"), but the value of the "iron loss immediately after processing" was about twice as large as the "iron loss evaluation value for a single plate". Also, the rate of increase in iron loss due to processing the motor core was not constant, and the manner of change also differed depending on the motor core shape and material.

[0033]

Table 1

[0034] Subsequently, acid treatment was carried out as shown in FIG. 1 using various acids. FIG. 4 shows the change in the motor core iron loss (the "iron loss after acid treatment") when the motor core No. 4 in Table 1 was acid-treated. The motor core iron loss (W 10 / 400 ) immediately after wire electrical discharge machining was 27.1 W / kg, but the iron loss decreased by immersing it in acid, showing a behavior approaching the iron loss evaluation value for a single plate. FIG. 5 shows the result of separating the loss by the two-frequency method for the motor core iron loss before and after acid treatment. Before acid treatment, out of the 27.1 W / kg of the motor core iron loss (W 10 / 400 ), the eddy current loss was as large as 20.7 W / kg. On the other hand, after acid treatment, the eddy current loss was reduced to 5.2 W / kg, and it is considered that the short circuit due to wire electrical discharge machining was eliminated.

[0035] Here, by monitoring the change in the motor core iron loss as shown in FIG. 4, acid treatment can be performed with an acid treatment time that eliminates short circuits without excess or deficiency. Taking the iron loss evaluation value at 1.0 T and 400 Hz for a single plate of the thin plate constituting the motor core as P SS (W / kg), the iron loss of the motor core, P C (W / kg), was processed until P C / P SS ≦1.3. By performing acid treatment for such an acid treatment time, a motor core in which the influence of short circuits at the end faces is eliminated can be manufactured. Here, P C / PSS The value may be well below 1.3, and the acid treatment time may be extended as necessary until the reduction of iron loss saturates.

[0036] Table 1 shows the iron loss after acid treatment under each condition as described above. For any of the 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 could be suppressed to 1.3 times or less compared to the iron loss evaluation value of a single plate. It was confirmed that a motor core with low iron loss can be manufactured by the method of acid treatment of the present disclosure.

[0037] Furthermore, it was found that when the acid bath solution used in the acid treatment step contains 15% to 90% phosphoric acid by mass fraction, the iron loss achievable by acid immersion is low. For example, in Table 1, numbers 14 to 16 only differ in the concentration condition of phosphoric acid. Compared with 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. When the acid is too dilute, the acid treatment takes a long time, and it is considered that the acid that has penetrated between the laminations damages the insulating film. Also, when the acid concentration is too high, the reactivity of the acid increases, and it is also considered that the insulating film is damaged and the achievable iron loss deteriorates.

[0038] (Example 2) Six motor cores were manufactured under the same conditions as No. 4 in Table 1 (material: 20JNEH1200, core shape: A, processing method: wire electrical discharge machining). The first motor core corresponds to Nos. 4a and 4b. The second motor core corresponds to Nos. 4c and 4d. Similarly hereinafter, two numbers correspond to one motor core. Table 2 shows the iron loss of each motor core after processing. The excitation condition of the motor core during acid treatment ("excitation condition of acid treatment") was changed as shown in Table 2, and the motor core was immersed in an acid bath solution 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 with a strain gauge before acid treatment. Also, in any acid treatment condition, when the iron loss of the motor core reached 11.3 W / kg, it was judged that the short circuit at the end face was removed, and the treatment time was evaluated ("acid treatment time"). When the magnetostriction exceeded 3.0 ppm, the acid treatment time became shorter. It is considered that the bubbles that inhibit acid treatment were peeled off from the motor core by magnetostriction vibration, acid treatment was promoted, and short circuit removal in a short time became possible. As described above, by exciting under the condition that the magnetostriction of the motor core becomes large, short circuit removal in a short time becomes possible.

[0039]

Table 2

[0040] As described in the examples, the method for manufacturing a motor core according to the present embodiment can suppress an increase in iron loss due to a short circuit at the end face caused by processing the motor core shape by acid treatment with little excess or deficiency in a relatively short time. Therefore, a motor core with reduced iron loss can be manufactured. In addition, the method for manufacturing a motor core according to the present embodiment can be applied to the development or mass production of high-efficiency motors, so it has high industrial application value.

[0041] 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 corrections based on the present disclosure. Therefore, it should be noted that these modifications or corrections are included in the scope of the present disclosure. For example, the functions included in each component or each step, etc. can be rearranged so as not to be logically contradictory, and it is possible to combine or divide a plurality of components or steps, etc. into one. The embodiments according to the present disclosure can also be realized as a program executed by a processor included in the device or a storage medium recording the program. It should be understood that these are also included in the scope of the present disclosure.

Claims

1. A method for manufacturing a motor core from a block core formed by stacking thin plates, comprising the steps of: a cutting step of processing the block core into a desired motor core shape by cutting through melting; and an acid treatment step of contacting the motor core with an acid bath liquid, A method for manufacturing a motor core, wherein iron loss measurement of the motor core is performed in the acid treatment step.

2. The method for manufacturing a motor core according to claim 1 , wherein excitation conditions for measuring the iron loss are adjusted so that the magnetostriction of a material constituting the motor core is 3.0 ppm or more.

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

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

5. A motor core manufactured by the method for manufacturing a motor core according to claim 1 or 2, In the acid treatment step, the iron loss evaluation value of the single thin plate at 1.0 T and 400 Hz is P ＳＳ (W / kg), the iron loss of the motor core, P Ｃ (W / kg) is 1.0 or less Ｃ / P ＳＳ A motor core that is acid-treated until it meets the following criteria:

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