JP2769061B2 - Extremely anisotropically oriented magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly anisotropically oriented magnet suitable for use as a permanent magnet rotor or a stator of a motor, and more particularly to cogging of a built-in motor, vibration and noise caused by the cogging, and uneven rotation. It is an object of the present invention to propose a magnet that can effectively reduce the occurrence of the occurrence.

[0002]

2. Description of the Related Art Conventionally, as a cylindrical or cylindrical permanent magnet for a motor, an isotropic magnet in which an easy axis of magnetic particles does not appear or has a random arrangement, and an easy axis of magnetic particles have a radial direction ( Radially anisotropic magnets which are oriented in the (radial direction) and polar anisotropically oriented magnets which are oriented extremely anisotropically with the peripheral surface as the working surface are known. Among the above magnets, the polar anisotropically oriented magnet can increase the magnetic flux density on the surface of the working surface and has the best magnetic properties.

By the way, when these permanent magnets are incorporated in a motor as a stator and the rotor is rotated, when the magnetic field formed by the stator is crossed, the gap magnetic flux density at the boundary greatly changes.
An adverse effect called cogging has occurred. Such cogging is not preferable because it causes delicate vibrations, noise and uneven rotation.

To solve this problem, isotropic magnets and radially oriented magnets are shown in FIGS. 2, 3, 4 and 5.
As shown in FIG. 2, magnetization is performed obliquely with respect to the generating line on the working peripheral surface (the outer peripheral surface in FIGS. 2 and 3 and the inner peripheral surface in FIGS. 4 and 5) (in the drawings, magnetic powder is used). Is shown by a solid line, and the arrangement of this orientation on the working surface is shown by a dashed line).

[0005] In the case of a highly anisotropically oriented magnet having good magnetic properties, the orientation of the axis of easy magnetization of the magnetic powder is extremely anisotropic. The direction and the magnetization direction do not match, and not only the desired magnetic characteristics cannot be obtained, but also the effect of oblique magnetization cannot be expected.

Therefore, as a countermeasure against cogging in a motor using a polar anisotropic magnet, a winding of an armature disposed opposite to the permanent magnet is obliquely wound (so-called slot skew).

However, when slot skew or the like is performed, a complicated magnetic pole shape is formed, and the winding method becomes complicated, so that the number of manufacturing steps is increased, and furthermore, the windings of the respective poles are varied, which is expensive and expensive. It was hard to say that it was industrially superior.

[0008]

In an extremely anisotropically oriented magnet, the rate of change in the rotor-stator gap magnetic flux density can be reduced without devising the armature opposed to the magnet when the magnet is incorporated into a motor, thereby reducing cogging and cogging. SUMMARY OF THE INVENTION It is an object of the present invention to propose a magnet which can effectively reduce the occurrence of vibrations and noises and rotational unevenness caused by it.

[0009]

Means for Solving the Problems According to the present invention, when the magnetic powder is oriented extremely anisotropically, the arrangement on the working surface of the extremely anisotropically oriented magnet is performed obliquely with respect to the generatrix, thereby obliquely magnetizing the magnet. Since the orientation direction of the subsequent magnetic powder and the magnetization direction match,
Cogging can be advantageously suppressed, thereby achieving the above object.

That is, according to the present invention, there is provided a magnet having a cylindrical or columnar shape, wherein the axis of easy magnetization of the magnetic powder is aligned in a very anisotropic orientation in a cross section perpendicular to the central axis so that one of the peripheral surfaces serves as a working surface. The polar anisotropically oriented magnet has a polar anisotropic orientation arranged obliquely with respect to the generatrix on the working peripheral surface.

Here, in order to improve the surface magnetic field of the magnet working surface, it is advantageous that the axis of easy magnetization of the magnetic powder is focused toward the center of the working surface in a cross section including the central axis.

FIG. 1 is a perspective view showing a pole anisotropically oriented magnet of the present invention as an example of ten poles orientation. In the figure, the orientation direction of the magnetic powder is indicated by a solid line, and the arrangement of the orientation on the operation surface is indicated by a dashed line. FIG. 1 (a) shows a cylindrical pole anisotropically oriented magnet having an outer circumferential surface as a working surface, and FIG. 1 (b) shows a cylindrical pole anisotropically oriented magnet having an inner circumferential surface as a working surface. c) is a cylindrical pole anisotropically oriented magnet whose peripheral surface is the working surface. In each of these magnets, the polar anisotropic orientation is arranged obliquely with respect to the generatrix (same as the height direction of the magnet) on the working peripheral surface.

[0013]

6 and 7 show an example of a cylindrical pole anisotropically oriented magnet of the present invention having six poles, in which the working surface is an outer peripheral surface (FIG. 6) and an inner peripheral surface (FIG. 7). For comparison, FIGS. 8 and 9 show a conventional cylindrical pole anisotropically oriented magnet. As is clear from the comparison between FIGS. 6 and 8, and FIGS. 7 and 9, the present invention is characterized in that the polar anisotropic orientation is obliquely arranged on the working surface so as to coincide with the oblique magnetization.

By thus obliquely arranging, when incorporated in a motor, the rate of change of the magnetic flux density between the rotor and the stator can be reduced, and the same effect as provided by slot skew can be obtained. Therefore, the cogging of the motor and the occurrence of vibration and noise, and furthermore, the occurrence of uneven rotation can be effectively reduced without any modification to the armature.

In the cylindrical pole anisotropically oriented magnets shown in FIGS.
The optimum angle can be appropriately selected according to the number of poles and the pole width of the stator.

The oblique arrangement according to the present invention is not limited to the examples shown in FIGS. 6 and 7, but may be an arrangement pattern as shown in FIGS. 10 and 11, for example. Here, FIG. 10 shows an example of the working surface on the outer circumferential surface, and FIG. 11 shows an example of the working surface on the inner circumferential surface.
In general, when incorporated in a motor, the magnetic flux density between one pole of a polar anisotropically oriented magnet and an opposing armature gradually increases with rotation of a rotor, and gradually decreases after reaching a maximum value. If it is a proper wiring pattern, it is suitable.

Next, the magnetic circuit device of the magnetic field orientation molding die according to the present invention will be described. FIG. 12 corresponds to the case of manufacturing the cylindrical pole anisotropically oriented magnet in which the outer peripheral surface shown in FIG. 6 is the working surface. FIG. 12 (a) is a cross section taken along the line AA of FIG.
6 shows a BB section of FIG. 6, and (c) shows a CC section of FIG. In the figure, reference numeral 1a denotes a cylindrical cavity. The cylindrical cavity 1a is formed by concentrically arranging a nonmagnetic material 2 inward and an annular magnet 3 for extremely anisotropic orientation outward. You. Reference numeral 4 denotes a ferromagnetic back yoke. Fig. 12 (a), (b)
As can be seen from (c), this magnetic circuit device is characterized by a ring magnet 3 for polar anisotropic orientation,
Use a magnet whose magnetic poles gradually rotate from the B section to the CC section.

In the case of a pole-shaped anisotropic magnet, FIG.
By applying the magnetic circuit device indicated by 12, the extremely anisotropic orientation of the present invention can be imparted. In this case, the non-magnetic material 2 is unnecessary.

FIG. 13 corresponds to the case of manufacturing the cylindrical pole anisotropically oriented magnet having the inner peripheral surface shown in FIG. 7 as the working surface. FIG. 13 (a) is a sectional view taken along the line AA of FIG. ) Shows a BB cross section of FIG. 7, and (c) shows a CC cross section of FIG. In the figure, reference numeral 1b denotes a cylindrical cavity. The cylindrical cavity 1b has an annular magnet 5 for extremely anisotropic orientation inward and a nonmagnetic material 6 outward.
Are formed concentrically. Reference numeral 7 denotes a ferromagnetic back yoke. Similarly, as can be seen from FIGS. 13 (a), (b), and (c), this magnetic circuit device has a polar anisotropic orientation for the cylindrical pole anisotropic orientation magnet whose inner peripheral surface is the working surface. The magnetic pole of the annular magnet 5 is changed from AA cross section to BB cross section through CC.
The feature is to use a magnet that gradually rotates as it goes to the cross section.

FIGS. 14 and 15 show cross sections of these magnetic circuit devices.
Shown in FIG. 14 is a sectional view of FIG. FIG. 3A shows an example in which the non-magnetic material 8 is provided on both end surfaces of the cylindrical cavity 1a, and no focusing orientation is performed. FIG. 3B shows an example in which the easy axis of magnetization of the magnetic powder is focused and oriented closer to the center of the working surface in a cross section including the central axis in order to improve the surface magnetic field of the magnet working surface. For this purpose, in the magnetic circuit device shown in FIG. 3B, the central region of the outer peripheral surface is a ring magnet 3b for extremely anisotropic orientation, the end of the outer peripheral surface is made of a non-magnetic material 9, and both end surfaces are made of a ferromagnetic material 10. Therefore, it is more preferable that the inner peripheral surface is formed of a non-magnetic material in the vicinity of both ends. That is, the annular magnet b3 for extremely anisotropic orientation is arranged in the central region of the working surface of the magnet with a length shorter than the total height of the magnet to be formed, and the ferromagnetic material 10 is arranged on both end surfaces. For example, while the synthetic resin magnet material introduced into the cylindrical cavity 1a by injection molding is in a softened state, a magnetic field is applied from an annular magnet 3b disposed on the outer peripheral surface, and the material is aligned in a very anisotropic orientation. However, the magnetic field lines at the end of the cavity are ferromagnetic
It is drawn to 10 and becomes the magnetic powder orientation shown in the figure, resulting in a focused orientation at the working surface.

FIG. 15 is a sectional view of FIG. FIG. 3A shows an example in which the non-magnetic material 11 is provided on both end surfaces of the cylindrical cavity 1a, and no focusing orientation is performed. FIG. 2 (b) shows that the axis of easy magnetization of the magnetic powder is changed to improve the surface magnetic field of the magnet working surface.
This is an example of focusing and orienting toward the center of the working surface in a cross section including the central axis. For this purpose, in the magnetic circuit device shown in FIG. 1B, the central region of the inner peripheral surface is formed into a ring magnet 5b for extremely anisotropic orientation.
The end of the inner peripheral surface is made of a non-magnetic material 12, and both end surfaces are made of a ferromagnetic
Therefore, it is more preferable that the inner peripheral surface is formed of a non-magnetic material in the vicinity of both ends. That is, by arranging the annular magnet 5b for extremely anisotropic orientation with a length shorter than the total height of the magnet to be formed, in the center region of the working surface of the magnet, and arranging the ferromagnetic material 13 on both end surfaces, for example, While the synthetic resin magnet material introduced into the cylindrical cavity 1b by injection molding is in a softened state, a magnetic field is applied from an annular magnet 5b disposed on the outer peripheral surface, and the material is aligned in a very anisotropic orientation. However, at this time, at the end of the cavity, the lines of magnetic force are attracted to the ferromagnetic material 13 and become the magnetic powder orientation shown in the figure, and as a result, the focused orientation on the working surface is formed.

As shown in FIGS. 14 (b) and 15 (b), the easy axis of the magnetic powder is focused and oriented toward the center of the working surface in a cross section including the central axis, so that the surface magnetic field on the working surface is reduced. The reason for the improvement will be described.

FIG. 16 shows a cross section of a motor using a polar anisotropic magnet for the stator, comparing the magnet of the present invention (FIG. 16A) with the conventional magnet (FIG. 16B). 14a and 14b in the figure
Is a cylindrical magnet, 15 is a motor case, 16 is a rotor magnetic pole, 17 is a rotor excitation coil, 18 is a rotor shaft, 19 is a brush,
Reference numeral 20 denotes a lead wire for conducting the brush, 21 denotes a bearing of the rotor shaft 18, 22 denotes a leaf spring, and 23 denotes a washer. Figure
As is clear from Fig. 16 (a), the actual working area facing the rotor is near the center of the magnet, and the end is only facing the exciting coil and brush arranged in the motor, and the useless magnetic flux Is caused.

On the other hand, as shown in FIGS. 14 (b) and 15 (b), in the cross section including the central axis of the polar anisotropically oriented magnet,
When the orientation of the axis of easy magnetization of the magnetic powder is focused near the center of the working surface (actual working area), substantially all of the magnetic flux converges to the working area. The surface magnetic field in the actual working area can be substantially improved, and a motor with a large torque can be obtained.

As the magnet material of the present invention, both a sintered magnet and a synthetic resin magnet can be used. Synthetic resin magnets do not sinter at high temperatures unlike sintered magnets, so there is no distortion in the magnet product, and the presence of the binder reduces the rate of cracking and chipping of the magnet product, enabling high-yield production. This is advantageous in that it can be integrally formed with the cup or the cup.

As the magnetic powder in the sintered magnet and the synthetic resin magnet, any of magnetic powders such as ferrite, alnico, samarium-cobalt, and neodymium-iron-boron can be used. Also, the average particle size of the magnetic powder particles can be used within a known range.
For example, 1.5μm for ferrite, 10 ~
50 μm is common. Conventionally known synthetic resins can also be used. For example, polyamide-based synthetic resins such as polyamide 12 and polyamide 6, polyvinyl chloride, its vinyl acetate copolymer, MMA, PS, PPS,
Single or copolymerized vinyl synthetic resin such as PE, PP, urethane, silicone, polycarbonate, PB
A synthetic resin such as T, PET, PEEK, CPE, Hypalon, neoprene, SBR, NBR, or a thermosetting synthetic resin such as an epoxy-based or phenol-based resin can be used.

Further, the mixing ratio of the magnetic powder and the synthetic resin as a binder depends on the application, but generally the magnetic powder is 40 to 70 v.
ol% is desirable. In addition, it goes without saying that appropriate amounts of conventionally used plasticizers, lubricants, antioxidants, surface treatment agents and the like can be used according to the purpose.

The above ferromagnetic materials 4, 7, 10 and 13
Is made of carbon steel such as S55C, S50C, S40C, SKD11, SKD61
Die steel, permendur, pure iron, etc. are used. Applying a surface hardening treatment to improve wear resistance
More advantageous. The materials of the nonmagnetic materials 2, 6, 8, 9 and 12 are austenitic stainless steel such as SUS 304, high manganese steel such as YHD50, copper beryllium alloy, bronze, brass and nonmagnetic cemented carbide N-7. Are used.
Known magnets can be used for the ring magnets 3a, 3b, 5a, and 5b. For example, a permanent magnet such as a samarium-cobalt magnet, or an electromagnet in which an exciting coil is made of a ferromagnetic material can be used.

As the molding method in a magnetic field, known molding methods can be used, and examples thereof include magnetic field orientation injection molding, magnetic field orientation compression molding, and magnetic field orientation RIM molding.

When a rare earth magnetic powder is used, it is desirable to apply a pulsed high magnetic field in advance or immediately after the rare earth magnetic powder is introduced, and to perform a pretreatment for equalizing the magnetic moment.

FIG. 17 shows an example in which a synthetic resin magnet is integrally formed with a shaft or a cup.

[0032]

EXAMPLE Using the mold magnetic circuit shown in FIGS. 12, 13, 14 and 15, the cylindrical pole anisotropically oriented magnet shown in FIGS. 18 and 19 was subjected to magnetic field orientation injection molding and magnetic field orientation compression molding. It was manufactured by the method. Each of the magnets in FIGS. 18 and 19 has an inner diameter of 16 mm and an outer diameter of 32.
mm, the height was 30 mm, and the polar anisotropic orientation was 8 poles, and the angle θ with respect to the obliquely generated bus was 6 °. Further, when focusing on the central area of the working surface in a cross section including the central axis as shown in FIGS. 14 (b) and 15 (b), the length of the central area is 24.
mm.

The following two types of magnetic powder were used. Magnetic powder A: Ferrite magnetic powder (magnet plumbite-based strontium-based ferrite having an average particle size of 1.5 μm) Magnetic powder B: Samarium-cobalt magnetic powder (Sm ₂ Co _17- based, average particle size of 15 μm)

The following raw materials were used for the mixture of the synthetic resin magnet and the sintered magnet. Formulation A (compound of synthetic resin magnet) Magnetic powder: 63 vol%, Polyamide 12: 36 vol%, Aminosilane A-1100: 1 vol% Formulation B (compound of sintered magnet) Magnetic powder: 50 wt%, water 50 wt%

The molding conditions were one of the following conditions for the synthetic resin magnet and the sintered magnet, respectively. Molding condition A (synthetic resin magnet) Pellet blending used: blending A Molding machine: Built-in coil type magnetic field injection molding machine Injection cylinder temperature: 300 ° C Mold temperature: 100 ° C Injection pressure: 1500kgf / cm ² Excitation time for orientation: 15 Second Cooling time: 20 seconds Injection cycle: 40 seconds Molding condition B (sintered magnet) Slurry: Compounding B Molding machine: Coil-mounted magnetic orientation compression molding machine Draining method: Injection method Excitation direction: Vertical magnetic field Molding temperature: 20 ℃ Firing temperature ： 1250 ℃

Tables 1 to 4 show the measurement results of the surface magnetic flux density on the working surface of the magnet thus obtained, the cogging phenomenon when the stator is incorporated in the motor, and the motor holding torque value. For comparison, magnets (Comparative Examples 1 and 4) whose polar anisotropic orientation is parallel to the generatrix of the working surface, isotropic magnets (Comparative Examples 2 and 5), and radially oriented magnets (Comparative Examples 3 and 6) ) And the measurement results for a magnet whose magnetization is inclined at the working peripheral surface with respect to the bus bar are also shown. The cogging phenomenon was evaluated relative to the comparative example (defective). The surface magnetic flux density was measured with a Gauss meter using a 70 μm square gallium arsenide Hall element. DC reduced to 16
The results are shown by relative evaluation based on a comparative example when used for a motor.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Table 3]

[0040]

[Table 4]

As is evident from the results of Tables 1 to 4, the embodiment in which the cylindrical pole anisotropically oriented magnets are arranged obliquely with respect to the bus in the working surface according to the present invention is a comparative example parallel to the bus. In addition, the cogging phenomenon is reduced, and the surface magnetic flux density and the motor holding torque are larger than those of the isotropic or radially oriented magnet. Further, in Examples 3, 6, 9, and 12 in which the focusing is performed in a cross section including the central axis so as to focus the short magnetic flux on the actual working area of the working surface, the surface magnetic flux density and the motor holding torque are increased.

[0042]

The pole anisotropically oriented magnet of the present invention has a pole anisotropic orientation which is arranged obliquely with respect to the generatrix on the working peripheral surface. The rate of change in density can be reduced, and the same effect as that of providing slot skew can be obtained.Therefore, motor cogging and the resulting vibration and noise, as well as rotation, can be achieved without any modification to the armature. The occurrence of unevenness can be effectively reduced.

Further, since the axis of easy magnetization of the magnetic powder is focused and oriented toward the center of the working surface in the cross section including the central axis, the surface magnetic field on the working surface of the magnet can be advantageously improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a pole anisotropically oriented magnet of the present invention as an example of ten poles orientation.

FIG. 2 is an explanatory diagram of an isotropic magnet having an outer peripheral surface as a working surface.

FIG. 3 is an explanatory diagram of a radially oriented magnet having an outer peripheral surface as an action surface.

FIG. 4 is an explanatory diagram of an isotropic magnet having an inner peripheral surface as a working surface.

FIG. 5 is an explanatory diagram of a radially oriented magnet having an inner peripheral surface as a working surface.

FIG. 6 is an explanatory diagram of a pole-oriented anisotropic magnet of the present invention having an outer peripheral surface as a working surface.

FIG. 7 is an explanatory view of a pole-anisotropically oriented magnet of the present invention having an inner peripheral surface as a working surface.

FIG. 8 is an explanatory view of a conventional extremely anisotropically oriented magnet having an outer peripheral surface as a working surface.

FIG. 9 is an explanatory view of a conventional extremely anisotropically oriented magnet having an inner peripheral surface as a working surface.

FIG. 10 is an explanatory diagram showing an example of an extremely anisotropic orientation array pattern of the magnet of the present invention.

FIG. 11 is an explanatory diagram showing an example of an arrangement pattern of the magnet of the present invention in a very anisotropic orientation.

FIG. 12 is an explanatory diagram of a molding die magnetic circuit of a cylindrical pole anisotropically oriented magnet whose outer peripheral surface is an action surface.

FIG. 13 is an explanatory view of a molding die magnetic circuit of a cylindrical pole anisotropically oriented magnet having an inner peripheral surface serving as a working surface.

FIG. 14 is a cross-sectional view of FIG.

FIG. 15 is a sectional view of FIG. 13;

FIG. 16 is a cross-sectional view of a motor using a polar anisotropically oriented magnet for a stator.

FIG. 17 is a view showing an example in which a shaft and a cup are integrally formed using a synthetic resin magnet.

FIG. 18 is an explanatory diagram of the dimensions and shape of the magnet created in the example.

FIG. 19 is an explanatory diagram of the dimensions and shape of the magnet created in the example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylindrical cavity 2 Non-magnetic substance 3 Annular magnet 4 Back yoke 5 Annular magnet 6 Non-magnetic substance 7 Back yoke 8 Non-magnetic substance 9 Non-magnetic substance 10 Ferromagnetic substance 11 Non-magnetic substance 12 Non-magnetic substance 13 Ferromagnetic substance

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takahiro Kikuchi 1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Corporation Research and Development Headquarters (72) Inventor Akira Yasuda 2-3-2 Uchisaiwaicho, Chiyoda-ku, Tokyo Kawasaki (58) Fields surveyed (Int.Cl. ⁶ , DB name) H01F 7/02

Claims (2)

(57) [Claims] 1. A magnet having a cylindrical or columnar shape, wherein the axis of easy magnetization of magnetic powder is aligned in a very anisotropic orientation in a cross section orthogonal to a central axis so that one of the peripheral surfaces serves as a working surface. An extremely anisotropically oriented magnet whose orientation is arranged obliquely to the generatrix on the working surface. 2. An extremely anisotropically oriented magnet according to claim 1, wherein the axis of easy magnetization of the magnetic powder is focused and oriented toward the center of the working surface in a cross section including the central axis.