JPH0719710B2 - Resin magnet manufacturing method - Google Patents

Description

The present invention relates to a method for producing a multipolar anisotropic resin magnet having excellent magnetic properties, using a mold for compacting and orienting which has been miniaturized. Regarding

[Conventional technology]

Conventionally, various molds for manufacturing resin magnets have been devised, but recently, with the miniaturization of stepping motors and the like in which resin magnets are mounted, resin magnets with a particularly small size and a large number of poles are required. As a mold for producing such a resin magnet, for example, as described in JP-A-57-170501, magnetic yokes and non-magnetic spacers alternate so as to surround a molding space. A mold in which a coil is arranged outside and a mold in which a conductive wire is provided in an orientation yoke having a magnetic pole portion around the molding space as described in JP-A-60-37112. Is commonly known.

[Problems to be solved by the invention]

However, the mold described in Japanese Patent Laid-Open No. 57-170501 uses a large-voltage and low-current power source, and therefore, when the magnetomotive force is increased, it is necessary to increase the number of turns of the coil, and the space for accommodating the coil is small. There is a problem that the device becomes large and the device becomes large. Also, as shown in the schematic cross-sectional view of Fig. 3, the magnetic path 1p passing through the non-magnetic spacer has a larger permeance than the magnetic path 2p passing through the molding space, so a considerable part of the magnetic flux generated from the coil Was leaked to the magnetic path 1p and did not contribute to the polar orientation. Further, the die described in JP-A-60-37112 has a very limited space for mounting the coil, and therefore, as the size and the number of poles are increased, it is necessary to use a thin conductive wire. The number should also be small. Therefore, there is a problem in that even when a large current of only a few thousand amps is instantaneously generated, considerable heat is generated, and it is difficult to generate a magnetic field sufficient to orient the resin magnet.

The present invention has been made in view of the above conventional problems,
It is an object of the present invention to provide a method capable of molding using a mold orientation mold that is smaller than the conventional one, and a method of manufacturing a resin magnet having multiple poles and excellent magnetic characteristics.

[Means for solving problems]

The above object of the present invention is to arrange a plurality of magnetic pole portions and a coil member for generating a magnetic flux in the magnetic pole portions on the outer periphery of a molding die for molding a resin magnet composition containing magnetic powder, An eddy current generating member is disposed between the magnetic pole portion and the magnetic pole portion, the composition is injected into the cavity of the mold to orient the magnetic powder to polar anisotropy by the magnetic flux, and between the magnetic pole portions. The leakage magnetic flux is canceled by the magnetic flux generated by the eddy current generated by the eddy current generating member.

Hereinafter, the production method of the present invention will be described with reference to embodiments.

FIG. 1 is a cross-sectional view of one embodiment of the present invention, in which 1 is a molding space, 2 is a spacer made of a good conductor, 3 is a magnetic pole portion made of a ferromagnetic material with high efficiency, 4 is a yoke portion, and 5 is a coil. Thus, the spacers 2 and the magnetic pole portions 3 are alternately arranged on the outer peripheral surface of the molding space 1. When this mold is energized,
A magnetic field is generated in the magnetic pole portion by the coil, and an eddy current is generated in the spacer 2.

When a single or multiple pulsed current is applied to the coil 5,
As shown in the enlarged view of FIG. 2, a magnetic flux flow in the molding space direction (longitudinal direction) as shown by the solid line and a lateral magnetic flux flow as shown by the broken line tend to occur in the magnetic pole portion. However, at this time, an eddy current is generated in the spacer 2 and a magnetic field is generated by this eddy current, so that the flow of the magnetic flux in the lateral direction indicated by the broken line is canceled and all the magnetic flux flows into the molding space. That is, the spacer 2 plays a role of confining magnetism and prevents magnetic flux leakage.

Various ferrites are used as the material forming the magnetic pole portion made of the strong magnetic pole body of the multi-pole molding orientation die of the present invention, and particularly Ni is used.
A system ferrite, a Mg system ferrite, etc. are used suitably.

As a material forming the spacer 2 for confining magnetism, a material having a low electric resistance such as copper is preferably used.

In the manufacturing method of the present invention, since magnetic flux leakage does not occur between the magnetic pole portions, it can be applied to a mold for manufacturing a resin magnet having a smaller distance between the magnetic pole portions and a smaller size and a larger number of poles. .

Further, since the coil can be installed in the outer peripheral portion which is separated from the molding space, there is a space in the space and it is possible to increase the number of turns of the coil and generate a strong magnetic field. At the same time, the conductive wire used for the coil can be made thick by bundling thin wires, and heat generation can be reduced.

The magnetic pole portion of the multi-pole molding orientation die used in the method of the present invention has a small amount of magnetic flux passing through the inside of the magnetic pole member due to the skin effect of the magnetic flux. A laminate is preferably used.

〔The invention's effect〕

As described above, in the manufacturing method of the present invention, it is possible to obtain a small resin magnet having a large number of poles without deteriorating the magnetic characteristics, and it is possible to save the applied current because there is no magnetic flux leakage, It is also possible to prevent the harmful effect of heat generation of the coil.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an example of a multipolar molding orientation die used in the method of the present invention, FIG. 2 is a partially enlarged view of FIG. 1, and FIG. 3 is a conventional multipolar molding. It is a partially expanded view explaining the problem of an orientation metal mold. 1: Molding space 1p: Flow of magnetic flux (leakage) 2: Spacer made of good conductor 2p: Flow of magnetic flux 3: Magnetic pole part made of ferromagnetic material 4: Yoke part 5: Coil 6: Nonmagnetic spacer

Claims (1)

[Claims] 1. A plurality of magnetic pole portions and a coil member for generating a magnetic flux in the magnetic pole portion are arranged on the outer periphery of a molding die for molding a resin magnet composition containing magnetic powder, and the magnetic pole portion and An eddy current generating member is arranged between the magnetic pole portions, and the composition is injected into the cavity of the mold to orient the magnetic powder to polar anisotropy due to the magnetic flux, and the leakage magnetic flux between the magnetic pole portions. Is canceled by a magnetic flux generated by the eddy current generated by the eddy current generating member.