JPH05175038A - Anisotropic cylindrical magnet - Google Patents

Abstract

PURPOSE:To distinctively improve surface magnetic flux density at the substantial effectuating surface of a cylindrical magnet or moreover a motor holding torque by directing the axes of easy magnetization of magnetic particles in the boundary regions of respective sections toward the proximity effectuating surface at the section in the longitudinal direction of the magnet. CONSTITUTION:Length of a permanent magnet 3 is set to almost the same length as the substantial effectuating surface of respective divided sections and the external circumference of cavity 1 is alternately surrounded by the poles N and S. Moreover, a ferromagnetic body 4 is arranged at the center of a center core 2. That is, the axes of easy magnetization of the magnetic particles in these boundary regions are arranged toward the proximity effectuating surfaces. Thereby, the magnetic particles in the boundary regions of respective divided sections can be effectively utilized and the surface magnetic flux density at the substantial effectuating surface or moreover a motor holding torque can be remarkably improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polar anisotropic cylindrical magnet suitable for use in a rotor of a PM type stepping motor, etc., and particularly to an advantageous improvement of the surface magnetic field on the working surface and hence the torque. Is.

[0002]

2. Description of the Related Art Conventionally, isotropic or radial anisotropic or polar anisotropic magnets have been known as cylindrical magnets used in PM type stepping motors. A polar anisotropic magnet has the best magnetic properties, but it is still not sufficient, and its improvement has been desired.

FIG. 1A shows a conventional polar anisotropic cylindrical magnet M.
Shows a cross section when the rotor is incorporated into a PM type stepping motor. As shown in the figure, the magnetized surface of the cylindrical magnet M is wider than the substantially working surface of the stator S, and the entire magnetized surface is Was not used effectively. In particular, since the central portion in the axial direction of the rotor structurally faces the non-acting surface of the stator S, it does not contribute to torque or other motor characteristics at all. .

[0004]

SUMMARY OF THE INVENTION The present invention advantageously solves the above problems and increases the surface magnetic field on the effective working surface of a cylindrical magnet, for example when used in stepping motors, especially two-phase motors. The purpose is to propose a polar anisotropic cylindrical magnet that can be expected to improve torque.

[0005]

That is, according to the present invention, either the inner peripheral surface or the outer peripheral surface of a cylinder having an O-shaped cross section is used as a working surface, and the working surface is at least in the axial direction of the cylinder. A polar anisotropic cylindrical magnet divided into two sections,
The orientation direction of the magnetic powder particles in the boundary region of each section is a polar anisotropic cylindrical magnet that is focused on the proximity action surface side in the longitudinal cross section of the magnet.

The present invention will be specifically described below. Figure 2
(A) and (b) show cross-sectional views of a preferred example of the polar anisotropic cylindrical magnet according to the present invention in which the outer peripheral surface or the inner peripheral surface is used as a working surface, and the working surface is divided into two in the axial direction. In the figure, the arrow indicates the orientation direction of the easy axis of magnetization. As shown in the figure, in the magnet of the present invention, the easy axis of magnetization of the magnetic particles in the boundary region of each divided area is focused and oriented on the proximity action surface side.
As shown in (b), there is no waste of all the magnetic flux, and therefore at least that much higher surface magnetic field and thus higher torque than before can be obtained. It should be noted that FIG. 2C shows the orientation state of the magnetic powder particles of the conventional polar anisotropic cylindrical magnet.

[0007]

The magnet material of the present invention may be either a sintered magnet or a synthetic resin magnet. For example, as a magnetic powder in a sintered magnet and a synthetic resin magnet, a ferrite-based material,
Alnico-based, samarium-cobalt-based, neodymium-iron-boron-based, or any other known material can be used. Also, the average particle size of the magnetic powder particles can be used within a known range. For example, it is generally 1.5 μm for ferrite type and 10 to 50 μm for rare earth type.

Also, as the synthetic resin, a conventionally known one can be used. For example, polyamide-based synthetic resins such as polyamide 12 and polyamide 6, polyvinyl chloride, vinyl acetate copolymer thereof, homo- or copolymerized vinyl-based synthetic resins such as MMA, PS, PPS, PE and PP, urethane,
Silicone, Polycarbonate, PBT, PET, PE
EK, CPE, Hypalon, Neoprene, SBR, NB
A synthetic resin such as R or a thermosetting synthetic resin such as an epoxy resin or a phenol resin can be used. Further, the compounding ratio of the magnetic powder and the synthetic resin as the binder depends on the application, but it is generally desirable to set the magnetic powder to 40 to 70 vol%. In addition, it goes without saying that appropriate amounts of conventional plasticizers, lubricants, antioxidants, surface treatment agents and the like can be used according to the purpose.

When applied to a plastic magnet, it is not necessary to fire it at a high temperature unlike a sintered magnet, and therefore, there are few chipping cracks, which is advantageous in that the yield is improved.
Further, as shown in FIG. 3, it is advantageous in that the entire structure can be formed of the plastic mag composition P and can be integrally molded with the shaft Sh, and any of them contributes to cost reduction.

Next, FIG. 4 illustrates a magnetic circuit device of a magnetic field orientation molding die suitable for manufacturing the magnet of the present invention. In the figure, number 1 is a center core 2 made of a non-magnetic material.
The cavities 3 provided in 1 are permanent magnets. The length of the permanent magnet 3 is set to be substantially the same as the substantially working surface of each of the divided areas, and the outer periphery of the cavity 1 is alternated between the N pole and the S pole as shown in FIG. It is arranged to surround it. Further, 4 is a ferromagnetic material portion arranged in the central portion of the center core 2. By arranging this ferromagnetic material portion 4 in the central portion on the non-acting surface side, the easy axis of magnetization of the magnetic powder particles is focused according to the present invention. It can be oriented.
That is, by arranging the ferromagnetic material on the non-acting surface side of the boundary area of the divided area, the easy axis of magnetization of the magnetic powder particles in this boundary area can be focused and oriented on the close acting surface side. Reference numeral 5 is a yoke made of a ferromagnetic material.

Although the case where the outer peripheral surface of the cylindrical magnet is used as the working surface has been described above with reference to FIG. 4, a suitable magnetic circuit device in the case where the inner peripheral surface is used as the working surface is disclosed as shown in FIG. .

As the ferromagnetic material, S55C, S50C, S4
Carbon steel such as 5C, die steel such as SKD11, pamenjour, pure iron and the like can be used, but it is more advantageous to apply a surface hardening treatment to improve wear resistance. As non-magnetic material, austenitic stainless steel such as SUS 304,
High manganese steel such as YHD 50, copper beryllium alloy and N-
A non-magnetic cemented carbide such as No. 7 is used. Further, as the magnet of the magnetomotive force portion, a known magnet can be used, and a permanent magnet such as a samarium-cobalt magnet is particularly advantageous. In addition, an electromagnet in which an exciting coil is wound around a ferromagnetic material can be used.

[0013]

EXAMPLES Using a mold incorporating the magnetic circuit device shown in FIG. 4 above, a cylindrical magnet having the shape and dimensions shown in FIG. 6 was manufactured under the conditions shown in Tables 1 to 3 below. When rare earth magnetic powder is used, pulsed high magnetic field treatment was performed immediately before the introduction into the cavity in order to align the magnetic moment in the easy axis of magnetization in advance.

[0014]

[Table 1] Raw magnetic powder A: Ferrite magnetic powder (magnetoplumbite strontium ferrite with an average particle size of 1.5 μm) Magnetic powder B: samarium-cobalt magnetic powder (2-17 system; average particle size 15 μm)

[0015]

TABLE 2 - formulation formulation A (plastic magnet formulation) magnetic powder: 63 vol% Polyamide 12: 36 vol% aminosilane A-1100: 1 vol% formulation B (sintered orientation) magnetic powder: 50 wt% Water: 50 wt%

[0016]

[Table 3] Molding method A: Plamag injection molding conditions Pellets used: Mixing A Molding machine: Magnetic field orientation injection molding machine with built-in coil Injection cylinder temperature: 300 ℃ Mold temperature: 100 ℃ Injection pressure: 1500 kg / cm ² Excitation Time: 15 seconds Cooling time: 20 seconds Injection cycle: 40 seconds ・ Molding method B: Sintered magnet making conditions Slurry used: Mixing B Molding machine: Coil-mounted magnetic field orientation compression molding machine Draining method: Injection method Excitation direction: Vertical Magnetic field Molding temperature: 20 ℃ Firing temperature: 1250 ℃ ・ Hall element 70μm square gallium-arsenic is used

The surface magnetic flux density on the effective working surface of the thus obtained polar anisotropic cylindrical magnet and the obtained cylindrical magnet are P
Table 4 shows the measurement results of the holding torque when used as the rotor of the M-type stepping motor.

[0018]

[Table 4]

As is clear from the table, the cylindrical magnet according to the present invention has a substantially improved surface magnetic flux density on the substantially working surface, and accordingly a holding torque.

[0020]

As described above, according to the present invention, it is possible to effectively utilize the magnetic powder particles in the boundary region of the divided areas, which has not been effectively utilized in the related art, and therefore, the surface magnetic flux density on the substantial working surface and thus the motor. It is possible to significantly improve the holding torque.

[Brief description of drawings]

FIG. 1A is a cross-sectional view of a stepping motor incorporating a conventional cylindrical magnet. (B) is a sectional view of a stepping motor incorporating a cylindrical magnet according to the present invention.

FIG. 2 is a sectional view showing an orientation direction of an easy axis of magnetization of magnetic powder particles of a cylindrical magnet.

FIG. 3 is a schematic view of a cylindrical magnet integrally formed with a shaft.

FIG. 4 is a diagram showing a magnetic circuit device suitable for use in manufacturing a cylindrical magnet according to the present invention having a cylinder outer periphery as a working surface.

FIG. 5 is a diagram showing a magnetic circuit device suitable for use in manufacturing a cylindrical magnet according to the present invention having an inner circumference as a working surface.

FIG. 6 is a diagram showing dimensions and shapes of a cylindrical magnet manufactured in an example.

[Explanation of symbols]

 M Anisotropic cylindrical magnet S Stator Sh Shaft P Flamag composition 1 Cavity 2 Center core 3 Permanent magnet 4 Ferromagnetic part of center core 5 Yoke

Front Page Continuation (72) Inventor Koichi Daiichi Kawasaki-cho, Chiba City, Chiba Prefecture, Kawasaki Steel Co., Ltd. Technical Research Division (72) Inventor Takahiro Kikuchi, Kawasaki-machi, Chiba City, Chiba Prefecture Kawasaki Steel Co., Ltd. Technical Research Division (72) Inventor Akira Yasuda 2-3-3 Uchisaiwaicho, Chiyoda-ku, Tokyo Kawasaki Steel Co., Ltd. Tokyo head office

Claims (1)

[Claims] 1. A polar anisotropic cylinder in which either the inner peripheral surface or the outer peripheral surface of a cylinder having an O-shaped cross section is used as a working surface, and the working surface is divided into at least two areas in the axial direction of the cylinder. -Shaped magnet, the orientation direction of the magnetic powder particles in the boundary region of each area, in the longitudinal cross section of the magnet,
A polar anisotropic cylindrical magnet characterized by focusing on the proximity action surface side.