Method of forming magnetic sheet

Abstract

To provide a technique capable of suppressing buckling in pressing a bridge part.SOLUTION: A method of forming a magnetic body sheet having a plurality of openings for inserting a magnetic body and having a bridge portion located between adjacent first openings and second openings includes a first thickening step of sandwiching and pressing a first boundary portion on the first opening side of the bridge portion and a second boundary portion on the second opening side of the bridge portion in the thickness direction of the magnetic body sheet, a second thickening step of sandwiching and pressing a third boundary portion on the first opening side smaller than the first boundary portion and a fourth boundary portion on the second opening side smaller than the second boundary portion after the first thickening step, and a center portion of the bridge portion is pressed in one direction in the thickness direction after the second thickening step. The method includes a bending step of bending the center part of the magnetic thin plate in one direction, and a crushing step of flattening the bridge part by holding the entire surface of the bridge part and pressing it in the thickness direction after the bending step.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a method for forming a magnetic thin plate. [Background technology]

[0002] There are known techniques for forming magnetic thin plates used in motor rotor cores. Patent Document 1 describes a technique for work-hardening by pressing bridge portions provided between magnet holes into which magnets are inserted. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-085776 Summary of the Invention [Problem to be solved by the invention]

[0004] If the bridge section is wide, there is a risk of it buckling due to pressure. Therefore, there has been a demand for technology that can increase the thickness of a wide area of ​​the bridge section while suppressing buckling. [Means for solving the problem]

[0005] The present disclosure has been made to solve the above-mentioned problems, and can be realized in the following forms.

[0006] According to an embodiment of the present disclosure, there is provided a method for molding a magnetic thin plate having a plurality of openings for inserting a magnetic material, the magnetic thin plate having a bridge portion located between adjacent first and second openings, the molding method including: a first thickening step of clamping a first boundary of the bridge portion on the first opening side and a second boundary of the bridge portion on the second opening side and pressing them in the thickness direction of the magnetic thin plate; a second thickening step of clamping a third boundary of the bridge portion on the first opening side, which has an area smaller than the first boundary, and a fourth boundary of the bridge portion on the second opening side, which has an area smaller than the second boundary, and pressing them in the thickness direction; a bending step of pressing a center of the bridge portion in one direction in the thickness direction to bend the center portion from the magnetic thin plate in the one direction after the second thickening step; and a crushing step of clamping an entire surface of the bridge portion and pressing it in the thickness direction to flatten the bridge portion. According to this form of molding method, the plate thickness is increased by the first thickening step, making it less likely to buckle, so that in the second thickening step, a wider area of ​​the bridge portion can be thickened than in the case where there is only one thickening step.

[0007] The present disclosure can be realized in various forms, for example, as a method for increasing the thickness of a magnetic thin plate. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram showing a schematic configuration of a magnetic thin plate. [Figure 2] 10 is a flowchart illustrating an example of a molding process. [Figure 3] FIG. [Figure 4] 10A and 10B are explanatory diagrams of a bending process and a crushing process. DETAILED DESCRIPTION OF THE INVENTION

[0009] A. Implementation: 1 is a diagram showing a schematic configuration of a magnetic thin plate 100 in this embodiment. The magnetic thin plate 100 is used, for example, in a rotor core of a motor. The magnetic thin plate 100 has a plurality of openings 20 for inserting magnetic bodies 10, and bridge portions 30 located between adjacent openings 20. The direction in which the openings 20 are aligned in the bridge portion 30 is also referred to as the width direction of the bridge portion 30.

[0010] In the present disclosure, the opening 20 includes a hole formation region where an opening for inserting the magnetic body 10 is formed. Also, the bridge portion 30 includes a bridge portion formation region located between the hole formation regions.

[0011] 2 is a flowchart showing an example of a molding process. The molding process is a process in which the bridge portion 30 is pressed by a molding device 500 to work-harden it. In this embodiment, this process is performed on the bridge portion forming region after temporary openings are formed in the hole forming region. After this process, openings 20 are formed in the hole forming region including the temporary openings. Hereinafter, the temporary openings will be simply referred to as openings 20, and the bridge portion forming region will be referred to as bridge portion 30.

[0012] 3 and 4 show simplified plan views of the target areas of the bridge portion 30 in each step of the molding process and simplified cross-sectional views of the bridge portion 30. The AA cross-sectional view shown in FIG. 3 is the AA cross-sectional view of the magnetic thin plate 100 in FIG. 1, and is a cross-sectional view along the width direction of the magnetic thin plate 100. The BB cross-sectional view shown in FIG. 4 is the BB cross-sectional view of the magnetic thin plate 100 in FIG. 1, and is a cross-sectional view along the length direction of the magnetic thin plate 100. The black arrows shown in FIGS. 3 and 4 indicate the pressing direction.

[0013] The forming apparatus 500 includes a thickness increasing apparatus 200, a bending apparatus 300, and a crushing apparatus 400. The thickness increasing apparatus 200 includes a first pressing section 210, a second pressing section 220, a third pressing section 230, and a fourth pressing section 240. The bending apparatus 300 includes a first pressing section 310, a first die 320, and a first punch section 330. The crushing apparatus 400 includes a second pressing section 410, a second die 420, and a second punch section 430.

[0014] First, in step S100, the thickness increasing device 200 performs a "first thickness increasing step" in which the first boundary 31 and the second boundary 32 of the bridge portion 30 are clamped and pressed from both sides in the thickness direction of the bridge portion 30, as shown in FIG. 3A. The first boundary 31 is a region of the bridge portion 30 on the side of the first opening 21 located on one side of the width direction of the bridge portion 30, and includes a region between the bridge portion 30 and the first opening 21. The second boundary 32 is a region of the bridge portion 30 on the side of the second opening 22 located on the other side of the width direction of the bridge portion 30, and includes a region between the bridge portion 30 and the second opening 22. A first distance L1 between the boundary of the first boundary 31 on the side of the second boundary 32 and the boundary of the second boundary 32 on the side of the first boundary 31 is set to a size such that the displacement of the bridge portion 30 falls within a displacement range in which the bridge portion 30 does not buckle.

[0015] The first pressing unit 210 clamps the first boundary 31 and presses the magnetic thin plate 100 in the thickness direction. The second pressing unit 220 clamps the second boundary 32 and presses the magnetic thin plate 100 in the thickness direction. That is, in the first thickening step, the thickening device 200 does not press the portion of the bridge portion 30 between the first boundary 31 and the second boundary 32.

[0016] In step S110 (see FIG. 2), the thickness increasing device 200 performs a "second thickness increasing process" in which the third boundary 33 and the fourth boundary 34 of the bridge portion 30 are clamped and pressed from both sides in the thickness direction of the bridge portion 30, as shown in FIG. 3B. Note that steps S100 and S110 are collectively referred to as the "thickness increasing process."

[0017] The third boundary 33 is a region on the first opening 21 side of the bridge portion 30, and is a region that includes the boundary between the bridge portion 30 and the first opening 21. The third boundary 33 is a region that has a smaller area than the first boundary 31. The fourth boundary 34 is a region on the second opening 22 side of the bridge portion 30, and is a region that includes the boundary between the bridge portion 30 and the second opening 22. The fourth boundary 34 is a region that has a smaller area than the second boundary 32.

[0018] The second distance L2 between the boundary of the third boundary 33 on the fourth boundary 34 side and the boundary of the fourth boundary 34 on the third boundary 33 side is set so that the displacement of the bridge portion 30 falls within the displacement range. The second distance L2 is also larger than the first distance L1.

[0019] The third pressing portion 230 holds the third boundary portion 33 and presses the magnetic thin plate 100 in the thickness direction. The fourth pressing portion 240 holds the fourth boundary portion 34 and presses the magnetic thin plate 100 in the thickness direction.

[0020] In step S120 (see FIG. 2), the bending device 300 performs a "bending process" in which, as shown in FIG. 4C, the bending device 300 presses the central portion 36 in the length direction of the bridge portion 30 in one direction in the thickness direction to bend the central portion 36 from the magnetic thin plate 100 in one direction. More specifically, the first pressing unit 310 and the first die 320 clamp both ends of the bridge portion 30 in the length direction. The central portion 36 of the bridge portion 30 that is not clamped between the first pressing unit 310 and the first die 320 is not in contact with the first die 320. The first punch unit 330 presses the central portion 36 in one direction in the thickness direction to cause it to protrude.

[0021] In step S130 (see FIG. 2), the crushing device 400 performs a "crushing process" in which the entire surface 37 of the bridge portion 30 is clamped and pressed from both thickness directions, as shown in FIG. 4D, to flatten the bridge portion 30. More specifically, the second pressing unit 410 and the second die 420 clamp both longitudinal ends of the bridge portion 30. The entire surface 37 of the bridge portion 30 is placed on the second die 420. The second punch unit 430 presses the central portion of the bridge portion 30, which is not clamped between the second pressing unit 410 and the second die 420, in the thickness direction. The crushing process preferably restores the thickness of the bridge portion 30, which was increased by the thickness increasing processes of steps S100 and S110 and the bending process of step S120, to its original thickness. Furthermore, in the crushing process, the bridge portion 30 is preferably pressed from the direction opposite to the direction in which it was pressed in the bending process of step S120.

[0022] According to the molding method of this embodiment described above, the bridge portion 30, which has been thickened in the first thickening step, is thickened in the second thickening step. Because the first thickening step increases the plate thickness and makes the bridge portion 30 less likely to buckle, the second thickening step can thicken a wider area of ​​the bridge portion 30 than if there was only one thickening step. Furthermore, the second distance L2, which is the distance between the third pressing portion 230 and the fourth pressing portion 240, can be widened without the bridge portion 30 buckling. Furthermore, because the bridge portion 30 can be thickened in a wider area, when forming the opening 20 in the hole formation region using a punching device after the molding process, the cumbersome task of providing a step in the pad of the punching device can be omitted.

[0023] B. Other Embodiments: (B1) In the above-described embodiment, the molding process is performed on the bridge portion forming region after the temporary openings are formed in the hole forming region. However, the molding process is not limited to this, and may be performed on the bridge portion 30 after the openings 20 are formed.

[0024] (B2) In the above-described embodiment, the molding process is divided into two steps, a first thickening step and a second thickening step, to thicken the bridge portion 30. However, the thickness increasing step may be divided into three or more steps.

[0025] (B3) In the second thickening step in the above-described embodiment, in addition to the third boundary 33 and the fourth boundary 34 in the bridge portion 30, the intermediate portion, which is the region located between the third boundary 33 and the fourth boundary 34 in the bridge portion 30, may be clamped and pressed from both thickness directions of the bridge portion 30. The distance between the third boundary 33 and the intermediate portion and the distance between the fourth boundary 34 and the intermediate portion are each sized so that the displacement amount of the bridge portion 30 falls within the displacement range.

[0026] (B4) In the above-described embodiment, the bending device 300 and the crushing device 400 may be the same device. Also, the first pressing unit 310 and the second pressing unit 410 may be the same device, the first die 320 and the second die 420 may be the same device, and the first punch unit 330 and the second punch unit 430 may be the same device.

[0027] The present disclosure is not limited to the above-described embodiments and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted. [Explanation of symbols]

[0028] 10...magnetic material, 20...opening, 21...first opening, 22...second opening, 30...bridge portion, 31...first boundary portion, 32...second boundary portion, 33...third boundary portion, 34...fourth boundary portion, 36...central portion, 37...entire surface, 100...magnetic material thin plate, 200...thickening device, 210...first pressing portion, 220...second pressing portion, 230...third pressing portion, 240...fourth pressing portion, 300...bending device, 310...first pressing portion, 320...first die, 330...first punch portion, 400...pressing device, 410...second pressing portion, 420...second die, 430...second punch portion, 500...forming device

Claims

[Claim 1] A method for forming a magnetic thin plate having a plurality of openings for inserting magnetic material, the magnetic thin plate having a bridge portion located between adjacent first and second openings, the method comprising: a first thickness increasing step of sandwiching and pressing a first boundary portion of the bridge portion on the first opening side and a second boundary portion of the bridge portion on the second opening side in a thickness direction of the magnetic thin plate; a second thickening step of clamping and pressing a third boundary portion on the first opening side of the bridge portion, which has an area smaller than that of the first boundary portion, and a fourth boundary portion on the second opening side of the bridge portion, which has an area smaller than that of the second boundary portion, in the thickness direction after the first thickening step; a bending process, after the second thickening process, in which a central portion of the bridge portion is pressed in one direction in the thickness direction to bend the central portion from the magnetic thin plate in the one direction; a crushing step, after the bending step, of clamping the entire surface of the bridge portion and pressing it in the thickness direction to flatten the bridge portion.

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