Molding apparatus and arched magnet

Abstract

To provide a forming device which further can improve releasing property when taking out a bow-shaped compact from the forming device.SOLUTION: A forming device includes a die, and upper punches and lower punches, pressurizes magnetic powder within a cavity formed with the die, and the upper punches and the lower punches, and manufactures a bow-shaped formed body which has an outer-peripheral surface, an inner-peripheral surface, and a circumferential direction end face and an axial direction end surface. Therein, the upper punches and the lower punches have projection-shaped curved faces for forming the inner peripheral surface and a flat plane for forming a part or the whole part of the circumferential direction end face, and surface roughness Ra of at least a part of the flat plane is larger than surface roughness Ra of the projection-shaped curved faces.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a molding apparatus and an arcuate magnet.

Background Art

[0002] In a powder pressing apparatus for obtaining an arcuate molded body by filling and pressing powder in a cavity formed by an upper punch, a lower punch, and a die, a powder pressing apparatus having a groove on at least one contact surface of the upper punch or the lower punch that contacts the arcuate molded body is described in Patent Document 1.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0004] In the powder pressing apparatus of Patent Document 1, as shown in FIG. 3 of Patent Document 1, grooves are formed on the convex curved surface (the surface for forming the inner peripheral surface of the arcuate molded body) of the upper punch or the lower punch. This groove improves the mold release property when taking out the arcuate molded body from the powder pressing apparatus.

[0005] However, even in the powder pressing apparatus of Patent Document 1, depending on the shape and size of the molded body, it may be difficult to take out the molded body, and the mold release property cannot be said to be sufficient. In addition, groove marks are formed on the inner peripheral surface of the obtained molded body, and these groove marks also remain on the sintered body after sintering. Therefore, in the processing step of the sintered body in the subsequent process, problems such as time required to remove the groove marks and poor yield may occur.

Summary of the Invention

Problems to be Solved by the Invention

[0006] Embodiments of this disclosure enable the provision of a molding apparatus that can further improve the release properties when removing a bow-shaped molded body from the molding apparatus.

[0007] Furthermore, the embodiments of this disclosure enable the provision of a curved magnet that is easy to process in the processing step of a sintered body. [Means for solving the problem]

[0008] Exemplary molding apparatuses not limited to this disclosure include: A molding apparatus comprising a die, an upper punch, and a lower punch, wherein magnetic powder in a cavity formed by the die, the upper punch, and the lower punch is pressurized to produce an arch-shaped form having an outer surface, an inner surface, a circumferential end surface, and an axial end surface, The upper punch or the lower punch has a convex curved surface for forming the inner circumferential surface, It has a plane for forming part or all of the circumferential end face, The surface roughness Ra of at least a portion of the plane is greater than the surface roughness Ra of the convex curved surface.

[0009] In one embodiment, the surface roughness Ra of the plane is 0.1 μm or more, and the surface roughness Ra of the convex curved surface is less than 0.1.

[0010] In one embodiment, the convex curved surface is provided with a coating layer of 1 μm or less in thickness.

[0011] Examples of arc-shaped magnets not limited to this disclosure include: An arc-shaped magnet having an outer circumferential surface, an inner circumferential surface, a circumferential end surface and an axial end surface, In the sintered body before grinding, the surface roughness Ra of at least a portion of the circumferential end face is greater than the surface roughness Ra of the inner circumferential face.

[0012] In one embodiment, the curved magnet is a ferrite sintered magnet. [Effects of the Invention]

[0013] According to the embodiments of this disclosure, it is possible to provide a molding apparatus that can further improve the release properties when removing a bow-shaped molded body from the molding apparatus.

[0014] Furthermore, according to the embodiments of this disclosure, it becomes possible to provide a bow-shaped magnet that is easy to process in the processing step of the sintered body. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic perspective view showing the upper or lower punch of an embodiment. [Modes for carrying out the invention]

[0016] A molding apparatus according to an embodiment of the present disclosure includes a die, an upper punch, and a lower punch, and pressurizes magnetic powder in a cavity formed by the die, the upper punch, and the lower punch to produce a bow-shaped form having an outer circumferential surface, an inner circumferential surface, a circumferential end face, and an axial end face, wherein the upper punch or the lower punch has a convex curved surface for forming the inner circumferential surface and a flat surface for forming part or all of the circumferential end face, and the surface roughness Ra of at least a part of the flat surface is greater than the surface roughness Ra of the convex curved surface.

[0017] In other words, as described in Patent Document 1, instead of forming grooves on the convex curved surface of the upper or lower punch to form the inner circumferential surface of the arch-shaped molded body, the surface roughness Ra of at least a portion of the plane 2 (shaded portion in Figure 1) that forms part or all of the circumferential end face of the arch-shaped form of the upper or lower punch 1 is made greater than the surface roughness Ra of the convex curved surface 3, as shown in Figure 1. This further improves the release properties when removing the arch-shaped molded body from the molding apparatus.

[0018] In an embodiment of the present disclosure, it is preferable that the surface roughness Ra of the flat surface is the same over the entire flat surface. However, depending on the processing and treatment methods, it is also conceivable that the surface roughness Ra may be partially different. However, even in this case, if the surface roughness Ra of at least a part of the flat surface, preferably at least about 50% or more in terms of area ratio, is greater than the surface roughness Ra of the convex curved surface, the mold release property can be improved.

[0019] It is desirable that the surface roughness Ra of the flat surface is 0.1 μm or more, and it is desirable that the surface roughness Ra of the convex curved surface is less than 0.1. To make the surface roughness Ra of the flat surface 0.1 μm or more and the surface roughness Ra of the convex curved surface less than 0.1, the following methods can be adopted, but are not limited thereto. (a) The convex curved surface and the flat surface of the upper punch or the lower punch are processed separately so that the convex curved surface is processed to Ra less than 0.1 and the flat surface is processed to Ra 0.1 μm or more. (b) The lower surface of the upper punch or the upper surface of the lower punch including the convex curved surface and the flat surface is processed so as to have Ra 0.1 μm or more, and then only the convex curved surface is processed so as to have Ra less than 0.1. (c) The lower surface of the upper punch or the upper surface of the lower punch including the convex curved surface and the flat surface is processed so as to have Ra less than 0.1, and then only the flat surface is processed so as to have Ra 0.1 μm or more. (d) The lower surface of the upper punch or the upper surface of the lower punch including the convex curved surface and the flat surface is processed so as to have Ra 0.1 μm or more, and then a coating layer is provided on only the convex curved surface so as to have Ra less than 1 μm. (e) A coating layer is provided on the lower surface of the upper punch or the upper surface of the lower punch including the convex curved surface and the flat surface so as to have Ra less than 0.1 μm, and then only the flat surface is processed so as to have Ra 0.1 μm or more.

[0020] For the coating, known coatings such as, for example, PVD·CVD coatings, TiN·TiC coatings, hard chromium coatings, nickel coatings, ceramic coatings, DLC coatings, etc. may be adopted.

[0021] In the embodiment of the present disclosure, the reason for using a part or all of the plane for forming the circumferential end face is that when the entire circumferential end face of the arcuate formed body is formed by the plane of the shaded portion in FIG. 1, and when a part of the circumferential end face of the arcuate formed body is formed by the plane of the shaded portion in FIG. 1 and the other part is formed by the inner surface of the die (when the circumferential end face of the arcuate formed body is in a "く" shape in the axial cross-sectional view).

[0022] According to the forming device according to the embodiment of the present disclosure, unlike the powder pressing device described in Patent Document 1, even if grooves are not formed on the convex curved surface having a relatively large area (without groove processing), by performing processing only on the plane having a relatively small area, the mold release property can be improved, so that the processing cost of the lower surface of the upper punch or the upper surface (forming surface) of the lower punch can be reduced.

[0023] Also, in the powder pressing device described in Patent Document 1, the mold release property is improved by having grooves on the convex curved surface. However, as described above, the convex curved surface has a relatively large area, and depending on the shape and size of the formed body, the effect of the grooves may decrease, making it difficult to take out the formed body. On the other hand, according to the forming device according to the embodiment of the present disclosure, by simply making the surface roughness Ra of the plane larger than the surface roughness Ra of the convex curved surface, excellent mold release property can be obtained regardless of the shape and size of the formed body. That is, the mold release property can be further improved.

[0024] By sintering (firing) the arcuate formed body formed by the forming device according to the embodiment of the present disclosure, an arcuate magnet having an outer peripheral surface, an inner peripheral surface, a circumferential end face, and an axial end face is obtained. In the sintered body before grinding, an arcuate magnet according to the embodiment of the present disclosure in which the surface roughness Ra of at least a part of the circumferential end face is larger than the surface roughness Ra of the inner peripheral surface is obtained.

[0025] The curved magnet according to the embodiment of this disclosure does not have groove marks formed on its inner circumferential surface, unlike the curved molded body obtained by the powder press apparatus of Patent Document 1. Therefore, in the subsequent sintered body processing process, problems such as requiring time to remove the groove marks remaining on the sintered body or poor yield are less likely to occur, and processing is easier.

[0026] The aforementioned arc-shaped magnet may be a ferrite sintered magnet or a rare-earth sintered magnet such as an RTB-type sintered magnet, but the effect is particularly pronounced when it is a ferrite sintered magnet with a smaller average crystal grain size than a rare-earth sintered magnet.

[0027] If the arched magnet according to the embodiment of this disclosure is a ferrite sintered magnet, it can be obtained, for example, by a manufacturing method having the following steps. A raw material powder mixing process in which raw material powders such as Fe2O3 are mixed to obtain a mixed raw material powder, A calcination step in which the mixed raw material powder is calcined to obtain a calcined body, A grinding step to pulverize the calcined body and obtain powder from the calcined body, A molding process in which the powder of the calcined body is molded using the molding apparatus described above to obtain a molded body, A firing step in which the molded body is fired to obtain a sintered body. The conditions in each process can be those of known manufacturing methods. [Industrial applicability]

[0028] The molding apparatus and arched magnet according to the embodiments of this disclosure have industrial applicability in that they can provide a molding apparatus that can further improve the release properties when removing an arched molded body from the molding apparatus, and they can provide an arched magnet that is easy to process in the processing of a sintered body. [Explanation of Symbols]

[0029] 1. Upper punch or lower punch 2 planes 3. Convex curved surface

Claims

1. A molding apparatus comprising a die, an upper punch, and a lower punch, wherein magnetic powder in a cavity formed by the die, the upper punch, and the lower punch is pressurized to produce an arch-shaped form having an outer surface, an inner surface, a circumferential end surface, and an axial end surface, The upper punch or the lower punch has a convex curved surface for forming the inner circumferential surface, It has a plane for forming part or all of the circumferential end face, A molding apparatus characterized in that the surface roughness Ra of at least a portion of the plane is greater than the surface roughness Ra of the convex curved surface.

2. The molding apparatus according to claim 1, characterized in that the surface roughness Ra of the plane is 0.1 μm or more, and the surface roughness Ra of the convex curved surface is less than 0.

1.

3. The molding apparatus according to claim 2, characterized in that the convex curved surface is provided with a coating layer of 1 μm or less.

4. An arc-shaped magnet having an outer circumferential surface, an inner circumferential surface, a circumferential end surface and an axial end surface, An arc-shaped magnet characterized in that, in the sintered body before grinding, the surface roughness Ra of at least a portion of the circumferential end face is greater than the surface roughness Ra of the inner circumferential face.

5. The arched magnet according to claim 4, characterized in that the arched magnet is a ferrite sintered magnet.

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