JP2024051230A - Molding device and arc-shaped magnet - Google Patents

Abstract

The present invention provides a molding apparatus capable of further improving the releasability when removing an arch-shaped molded body from the molding apparatus.
[Solution] A molding device that 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 body having an outer surface, an inner surface, a circumferential end surface, and an axial end surface, wherein the upper punch or the lower punch has a convex curved surface for forming the inner surface and a flat surface for forming part or all of the circumferential end surface, 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.
[Selected Figure] Figure 1

Description

The present disclosure relates to a molding device and an arc-shaped magnet.

Patent Document 1 describes a powder press device that obtains a bow-shaped compact by filling a cavity formed by an upper punch, a lower punch, and a die with powder and pressing it, and that has a groove on the contact surface of at least one of the upper punch or the lower punch that contacts the bow-shaped compact.

JP 2000-197998 A

In the powder pressing device of Patent Document 1, as shown in FIG. 3 of Patent Document 1, a groove is formed in the convex curved surface (the surface for forming the inner peripheral surface of the arch-shaped compact) of the upper punch or the lower punch. This groove improves the releasability when removing the arch-shaped compact from the powder pressing device.

However, even with the powder pressing device of Patent Document 1, it may be difficult to remove the molded body depending on its shape and size, and it cannot be said that the releasability is sufficient. In addition, groove marks are formed on the inner peripheral surface of the obtained molded body, and these groove marks remain in the sintered body after sintering, which can cause problems such as time required to remove the groove marks and reduced yield in the subsequent processing step of the sintered body.

Embodiments of the present disclosure make it possible to provide a molding device that can further improve the releasability when removing a bow-shaped molded body from the molding device.

Furthermore, the embodiments of the present disclosure make it possible to provide an arc-shaped magnet that is easy to process during the processing of the sintered body.

Non-limiting exemplary molding apparatus of the present disclosure include:
A molding apparatus including a die, an upper punch, and a lower punch, which pressurizes magnetic powder in a cavity formed by the die, the upper punch, and the lower punch to manufacture a bow-shaped body having an outer peripheral surface, an inner peripheral 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,
a flat surface for forming a part or the whole of the circumferential end surface;
The surface roughness Ra of at least a portion of the flat surface is greater than the surface roughness Ra of the convexly curved surface.

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

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

Non-limiting exemplary arcuate magnets of the present disclosure include:
An arcuate magnet having an outer peripheral surface, an inner peripheral surface, a circumferential end surface, and an axial end surface,
In the sintered body before grinding, the surface roughness Ra of at least a part of the circumferential end face is larger than the surface roughness Ra of the inner circumferential face.

In one embodiment, the arcuate magnet is a sintered ferrite magnet.

According to an embodiment of the present disclosure, it is possible to provide a molding device that can further improve the releasability when removing a bow-shaped molded body from the molding device.

Furthermore, according to the embodiment of the present disclosure, it is possible to provide an arc-shaped magnet that is easy to process during the processing of the sintered body.

FIG. 2 is a perspective view showing an upper punch or a lower punch of the embodiment.

The molding device 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 body having an outer peripheral surface, an inner peripheral surface, a circumferential end surface, and an axial end surface, wherein the upper punch or the lower punch has a convex curved surface for forming the inner peripheral surface and a flat surface for forming part or all of the circumferential end surface, 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.

That is, instead of forming a groove in the convex curved surface of the upper punch or lower punch to form the inner peripheral surface of the bow-shaped formed body as in Patent Document 1, as shown in FIG. 1, the surface roughness Ra of at least a part of the plane 2 (the shaded area in FIG. 1) for forming a part or all of the circumferential end surface of the bow-shaped formed body in the upper punch or lower punch 1 is made larger than the surface roughness Ra of the convex curved surface 3. This can further improve the releasability when removing the bow-shaped formed body from the molding device.

In the 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, but depending on the method of processing or treatment, it is possible that the surface roughness Ra may differ partially. However, even in this case, if the surface roughness Ra of at least a part of the flat surface, preferably at least about 50% by area, is greater than the surface roughness Ra of the convex curved surface, releasability can be improved.

The surface roughness Ra of the flat surface is desirably 0.1 μm or more, and the surface roughness Ra of the convexly curved surface is desirably 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 convexly curved surface less than 0.1, the following methods can be adopted, but are not limited to these.
(a) The convexly curved surface and the flat surface of the upper punch or the lower punch are separately machined to machine the convexly curved surface to an Ra of less than 0.1 μm and the flat surface to an Ra of 0.1 μm or more.
(b) After machining the lower surface of the upper punch or the upper surface of the lower punch including the convex curved surface and the flat surface to an Ra of 0.1 μm or more, only the convex curved surface is machined to an Ra of 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 machined to have a roughness Ra of less than 0.1, and then only the flat surface is machined to have a roughness Ra of 0.1 μm or more.
(d) After machining the lower surface of the upper punch or the upper surface of the lower punch including the convex curved surface and the flat surface to an Ra of 0.1 μm or more, a coating layer is provided only on the convex curved surface to an Ra of 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 an Ra of less than 0.1 μm, and then only the flat surface is machined so as to have an Ra of 0.1 μm or more.

The coating may be a known coating such as a PVD/CVD coating, a TiN/TiC coating, a hard chrome coating, a nickel coating, a ceramic coating, or a DLC coating.

In the embodiment of the present disclosure, the plane for forming the circumferential end surface is a partial or complete plane because there are cases where the entire circumferential end surface of the bow-forming body is formed by the plane of the shaded portion in FIG. 1, and cases where a portion of the circumferential end surface of the bow-forming body is formed by the plane of the shaded portion in FIG. 1 and the other portion is formed by the inner surface of the die (when the circumferential end surface of the bow-forming body is "L" shaped in axial cross section).

According to the molding device according to the embodiment of the present disclosure, unlike the powder press device described in Patent Document 1, it is possible to improve demolding properties by performing processing only on the flat surface, which has a relatively small area, without forming grooves on the convex curved surface, which has a relatively large area (without performing groove processing), thereby reducing the processing costs of the lower surface of the upper punch or the upper surface (molding surface) of the lower punch.

In addition, in the powder pressing device described in Patent Document 1, the convex curved surface has grooves to improve demolding properties, but as mentioned above, the convex curved surface has a relatively large area, and depending on the shape and size of the molded body, the effect of the grooves may be reduced, making it difficult to remove the molded body. On the other hand, according to the molding device of the embodiment of the present disclosure, excellent demolding properties can be obtained regardless of the shape and size of the molded body by simply making the surface roughness Ra of the flat surface larger than the surface roughness Ra of the convex curved surface. In other words, demolding properties can be further improved.

By sintering (firing) the arch-shaped body formed by the forming device according to the embodiment of the present disclosure, an arch-shaped magnet having an outer peripheral surface, an inner peripheral surface, a circumferential end surface, and an axial end surface is obtained, in which, in the sintered body before grinding, the surface roughness Ra of at least a portion of the circumferential end surface is greater than the surface roughness Ra of the inner peripheral surface.

The arc-shaped magnet according to the embodiment of the present disclosure does not have groove marks on the inner circumferential surface, unlike the arc-shaped compact obtained by the powder pressing device of Patent Document 1. Therefore, in the subsequent processing step of the sintered body, problems such as time required to remove the groove marks remaining in the sintered body or reduced yield are unlikely to occur, and the magnet is easy to process.

The bow-shaped magnet may be a ferrite sintered magnet or a rare earth sintered magnet such as an R-T-B sintered magnet, but the above effect is more pronounced when the magnet is a ferrite sintered magnet, which has a smaller average crystal grain size than a rare earth sintered magnet.

When the arcuate magnet according to the embodiment of the present disclosure is a sintered ferrite magnet, it can be obtained, for example, by a manufacturing method having the following steps.
A raw material powder mixing process for mixing raw material powders such as Fe ₂ O ₃ to obtain a mixed raw material powder;
a calcination step of calcining the mixed raw material powder to obtain a calcined body;
A grinding step of grinding the calcined body to obtain a powder of the calcined body;
a molding step of molding the powder of the calcined body by the above-mentioned molding device to obtain a molded body;
A sintering step of sintering the molded body to obtain a sintered body.
The conditions in each step may be those of a known production method.

The molding device and the arched magnet according to the embodiments of the present disclosure have industrial applicability in that it is possible to provide a molding device that can further improve the demolding properties when removing an arched shaped compact from the molding device, and in that it is possible to provide an arched magnet that is easy to process in the processing step of the sintered compact.

1 Upper punch or lower punch 2 Flat surface 3 Convex curved surface

Claims (5)

A molding apparatus including a die, an upper punch, and a lower punch, which pressurizes magnetic powder in a cavity formed by the die, the upper punch, and the lower punch to manufacture a bow-shaped body having an outer peripheral surface, an inner peripheral 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,
a flat surface for forming a part or the whole of the circumferential end surface;
A molding apparatus characterized in that the surface roughness Ra of at least a portion of the flat surface is greater than the surface roughness Ra of the convexly curved surface. The molding device described in claim 1, characterized in that the surface roughness Ra of the flat surface is 0.1 μm or more, and the surface roughness Ra of the convex curved surface is less than 0.1. The molding device according to claim 2, characterized in that the convex curved surface is provided with a coating layer of 1 μm or less. An arcuate magnet having an outer peripheral surface, an inner peripheral surface, a circumferential end surface, and an axial end surface,
An arched magnet, characterized in that, in a 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. The arc-shaped magnet according to claim 4, characterized in that the arc-shaped magnet is a sintered ferrite magnet.

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