Molding method of magnetic sheet metal

Abstract

To provide a technology capable of suppressing buckling in pressurization of a bridge part.SOLUTION: A molding method of a magnetic sheet metal comprises: a thickening process of pressurizing a boundary part between a plurality of holes for inserting magnetic materials held by the magnetic sheet metal and opening parts of the holes at a bridge part located between the adjacent holes by holding both directions in a thickness direction by using a restriction member for restricting a displacement amount of the bridge part in the thickness direction of the bridge part to be settled within a predetermined displacement range in which the bridge part does not buckle; a bending process of pressurizing a center part of the bridge part in one direction in the thickness direction to bend the center part in one direction from the magnetic sheet metal after the thickening process; and a crushing process of pressurizing the whole surface of the bridge part by holding both directions in the thickness direction to planarize the bridge part after the bending process.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 too wide, it may buckle under pressure. However, because the holes into which the magnetic material is inserted are formed by punching, it is difficult to make the bridge section narrower than the width of the pad or die. Therefore, there was a need for technology that could prevent the bridge section from buckling even when pressed. [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 forming a magnetic thin plate, the method including: a thickening step of sandwiching and pressing a boundary between a plurality of holes for inserting magnetic bodies in the magnetic thin plate, the boundary being in a bridge portion located between adjacent holes, in both directions in the thickness direction, using a limiting member that limits a displacement of the bridge portion in the thickness direction within a predetermined displacement range in which the bridge portion does not buckle; a bending step of, after the thickening step, pressing a central portion of the bridge portion in one direction in the thickness direction to bend the central portion in the one direction from the magnetic thin plate; and a crushing step of sandwiching and pressing an entire surface of the bridge portion in both directions in the thickness direction to flatten the bridge portion. According to this molding method, the displacement of the bridge portion is limited to within the displacement range by the limiting member, so that buckling of the bridge portion during the thickness increasing step can be suppressed without reducing the width of the bridge portion.

[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] FIG. 1 is an explanatory diagram showing an example of a thickness increasing device. [Figure 5] FIG. 10 is an explanatory diagram showing another example of a thickness increasing device. 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 holes 20 for inserting magnetic bodies 10, and bridge portions 30 located between adjacent holes 20. In the bridge portions 30, the direction in which the holes 20 are arranged side by side is also referred to as the width direction of the bridge portions 30.

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

[0011] FIG. 2 is a flowchart showing an example of the molding process. FIG. 3 is an explanatory diagram of the 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 formation region after temporary holes are formed in the hole formation region. After this process, holes 20 are formed in the hole formation region including the temporary holes. Hereinafter, the temporary holes will be simply referred to as holes 20, and the bridge portion formation region will be referred to as bridge portion 30.

[0012] Figure 3 shows simplified plan views of target areas of the bridge portion 30 in each step and simplified cross-sectional views of the bridge portion 30. The AA cross-sectional view shown in Figure 3 is the AA cross-sectional view of the magnetic thin plate 100 in Figure 1, which is a cross-sectional view along the width direction of the magnetic thin plate 100. The BB cross-sectional view is the BB cross-sectional view of the magnetic thin plate 100 in Figure 1, which is a cross-sectional view along the length direction of the magnetic thin plate 100. The black arrow shown in Figure 3 indicates the pressing direction.

[0013] The forming apparatus 500 includes a thickness increasing device 200, a bending device 300, and a crushing device 400. The thickness increasing device 200 includes a first pressing unit 210, a second pressing unit 220, and a limiting member 230. The bending device 300 includes a first holding unit 310, a first die 320, and a first punch unit 330. The crushing device 400 includes a second holding unit 410, a second die 420, and a second punch unit 430.

[0014] First, in step S100, the thickness increasing device 200 performs a "thickening process" in which the boundary 31 between the bridge portion 30 and the opening of the hole 20 is clamped and pressed from both sides in the thickness direction of the bridge portion 30. The boundary 31 includes two regions: a boundary region between the opening of the hole 20 located on one side in the width direction of the bridge portion 30 and the opening of the hole 20 located on the other side. Hereinafter, the boundary region between the opening of the hole 20 located on one side in the width direction of the bridge portion 30 and the opening of the hole 20 located on the other side in the width direction of the bridge portion 30 will be referred to as "one boundary 31," and the boundary region between the opening of the hole 20 located on the other side will be referred to as "other boundary 31." The thickness increasing process is performed using a limiting member 230 that limits the displacement of the bridge portion 30 in the thickness direction to within a predetermined displacement range. The displacement range is a displacement range in which the bridge portion 30 does not buckle.

[0015] FIG. 4 is an explanatory diagram showing an example of a thickness increasing device 200. FIG. 4 is a cross-sectional view taken along line AA in FIG. 1. The thickness increasing device 200 includes a first pressing section 210, a second pressing section 220, and a limiting member 230. The first pressing section 210 and the second pressing section 220 sandwich and press the boundary section 31. The first pressing section 210 presses the boundary section 31 from one direction in the thickness direction of the bridge section 30. The second pressing section 220 presses the boundary section 31 from the other direction in the thickness direction of the bridge section 30. The limiting member 230 limits the amount of displacement of the bridge section 30 to fall within a displacement range.

[0016] The first pressing portion 210 has a first pressing portion left portion 211 that presses one boundary portion 31, and a first pressing portion right portion 212 that presses the other boundary portion 31. The second pressing portion 220 has a second pressing portion left portion 221 that presses one boundary portion 31, and a second pressing portion right portion 222 that presses the other boundary portion 31. The limiting member 230 is integral with the second pressing portion left portion 221 and the second pressing portion right portion 222, and is located between the second pressing portion left portion 221 and the second pressing portion right portion 222. That is, in the thickening process, the thickening device 200 does not press a portion of the bridge portion 30 between one boundary portion 31 and the other boundary portion 31.

[0017] The distance L1 between the first pressing portion left portion 211 and the first pressing portion right portion 212 is smaller than the distance L2 between the second pressing portion left portion 221 and the second pressing portion right portion 222. Therefore, the bridge portion 30 is displaced toward the second pressing portion 220, which has a larger distance between the pressing portions. The displacement of the bridge portion 30 is limited by the limiting member 230 located in the displacement direction of the bridge portion 30, so the bridge portion 30 is prevented from displacing to a degree that would cause it to buckle.

[0018] In step S110 (see FIG. 2), the bending device 300 performs a "bending process" in which the central portion 32 in the length direction of the bridge portion 30 is pressed in one direction in the thickness direction to bend the central portion 32 from the magnetic thin plate 100 in one direction. More specifically, as shown in FIG. 3B, the first pressing portion 310 and the first die 320 hold both ends of the bridge portion 30 in the length direction. The central portion 32 of the bridge portion 30 that is not held between the first pressing portion 310 and the first die 320 is not in contact with the first die 320. The first punch portion 330 presses the central portion 32 in one direction in the thickness direction to cause it to protrude.

[0019] In step S120, the crushing device 400 performs a "crushing process" in which the entire surface 33 of the bridge portion 30 is clamped and pressed from both thickness directions to flatten the bridge portion 30. More specifically, as shown in FIG. 3C, both longitudinal ends of the bridge portion 30 are clamped between a second pressing unit 410 and a second die 420. The entire surface 33 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 that 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 process in step S100 and the bending process in step S110, 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 in step S110.

[0020] According to the molding method of this embodiment described above, the displacement amount of the bridge portion 30 is limited to within a displacement range by the limiting member 230 positioned in the displacement direction of the bridge portion 30. Therefore, buckling of the bridge portion 30 can be suppressed during the thickness increasing process without reducing the width of the bridge portion 30. Furthermore, because the limiting member 230 is positioned on one side of the bridge portion 30 in the thickness direction, it is possible to prevent the magnetic thin plate 100 from filling the space in the thickness increasing device 200 and causing an excessive increase in the surface pressure of the thickness increasing device 200, thereby preventing damage to the thickness increasing device 200 and a shortened lifespan.

[0021] B. Other Embodiments: (B1) In the above-described embodiment, the molding process is performed on the bridge portion formation region after the temporary holes are formed in the hole formation region. However, the molding process is not limited to this, and may be performed on the bridge portion 30 after the holes 20 are formed.

[0022] (B2) In the above-described embodiment, the restricting member 230 is provided between the second pressing portion left portion 221 and the second pressing portion right portion 222. However, the present invention is not limited to this, and the restricting member 230 may also be provided between the first pressing portion left portion 211 and the first pressing portion right portion 212.

[0023] (B3) In the above-described embodiment, the intervals L1 and L2 of the thickness increasing device 200 are different lengths. This is not a limitation, and the intervals L1 and L2 may be the same length. FIG. 5 is an explanatory diagram showing another example of a thickness increasing device 200B. The radius of curvature R1 of the portion of the first pressing portion 210B that contacts the bridge portion 30 is smaller than the radius of curvature R2 of the portion of the second pressing portion 220B that contacts the hole portion 20. Since the magnetic thin plate 100 is displaced toward the second pressing portion 220B, which has the larger radius of curvature R1, the thickness increasing device 200B can prevent the bridge portion 30 from buckling.

[0024] (B4) In the above-described embodiment, the limiting member 230 is integral with the second pressing portion 220. However, the limiting member 230 may be separate from the second pressing portion 220. For example, the limiting member 230 may be composed of pad members provided between the first pressing portion left portion 211 and the first pressing portion right portion 212 and between the second pressing portion left portion 221 and the second pressing portion right portion 222, respectively, and an elastic member that presses the pad members against the bridge portion 30. In this case, in the thickening process, the elastic members are used to press the pad members against the bridge portion 30 from both thickness directions of the bridge portion 30. The pad members can prevent the bridge portion 30 from buckling. Furthermore, because the elastic members bend, an excessive increase in punch surface pressure due to blockage of material in the die can be prevented, thereby preventing damage and a shortened lifespan. Alternatively, a cylinder mechanism may be used to press the pad members instead of the elastic members.

[0025] (B5) 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.

[0026] 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]

[0027] 10...magnetic material, 20...hole portion, 30...bridge portion, 31...boundary portion, 32...center portion, 33...entire surface, 100...magnetic material thin plate, 200, 200B...thickening device, 210, 210B...first pressing portion, 211...left portion of first pressing portion, 212...right portion of first pressing portion, 220, 220B...second pressing portion, 221...left portion of second pressing portion, 222...right portion of second pressing portion, 230...limiting member, 300...bending device, 310...first pressing portion, 320...first die, 330...first punch portion, 400...crushing 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, comprising: a thickness-increasing process in which a boundary between a plurality of holes for inserting magnetic bodies in the magnetic thin plate and an opening of a bridge portion located between adjacent holes is clamped and pressed in both directions in the thickness direction using a limiting member that limits the displacement of the bridge portion in the thickness direction so that the amount of displacement of the bridge portion in the thickness direction falls within a predetermined displacement range in which the bridge portion does not buckle; a bending process after the 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 and pressing the entire surface of the bridge portion in both directions in the thickness direction to flatten the bridge portion.

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