JPS6150368B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to anisotropy treatment of an anisotropic magnet, and more particularly to a magnetic field orientation anisotropy treatment method for improving the surface magnetic flux density of a magnet.

A method of orienting magnetic powder having magnetic anisotropy in a magnetic field having a predetermined strength has been known for a long time. For example, anisotropic sintered ferrite
885 Publication), Anisotropic Resin Magnet (Special Publication No. 1978)
Publication No. 3321, Special Publication No. 39-28287), etc.

The purpose of the anisotropy treatment is to align the powder having magnetic anisotropy in the direction of magnetic lines of force when used as a magnet, so that it can effectively exhibit its properties as a magnet. For this purpose, it is desirable to use a magnetic field generated by a magnetic circuit that is equal to or similar to the magnetic circuit used for magnetization as an orienting magnetic field for anisotropy. This is also well known, and various efforts have been made. For example, there is a method in which magnets are arranged alternately in NS in a mold according to the magnetization distribution (Japanese Patent Publication No. 39-28287), and a method in which a mold with a coil and yoke similar to a magnetization yoke is used to achieve orientation using a pulsed magnetic field. There are two methods, including a method in which a mold having a magnetic circuit similar to the magnetizing yoke is used and a steady magnetic field is used for orientation.

If the expected effects of the above method are expressed simply and diagrammatically, expressions such as those shown in FIGS. 1 and 2 are acceptable. FIG. 1 shows the anisotropic direction of the anisotropic magnet powder, which has an axis of easy magnetization in the direction perpendicular to the wide surface of the flat powder 1 (in the direction of the arrow). FIG. 2 shows a case where the powder thus represented is arranged in an ideal manner. That is, assuming that the magnet 2 has different poles on the same surface, the surface of the powder 3 similar to that in FIG. 1 is oriented perpendicular to the direction of the preferred magnetic field lines (indicated by the broken line 4). That is the ideal.

In order to obtain the orientation shown in FIG. 2, it is necessary to apply a magnetic field having the direction of the lines of magnetic force shown by the broken line 4 when molding the anisotropic magnetic powder, and based on this, the above-mentioned Such orientation methods have been proposed.

However, there are several difficulties when attempting to actually obtain the magnetic field as described above.

The first is the strength of the magnetic field. It is said that the strength of the magnetic field is stronger than the coercive force of the oriented magnetic powder, and several times stronger than the coercive force of the oriented magnetic powder. For example, the most commonly used strontium ferrite is
It has approximately 3000 oersted in iHc, and the orientation magnetic field is 5000 oersted regardless of whether it is a sintered body or a resin magnet.
It generally requires at least 10 km oersted. On the other hand, the special public official 39-28287
It is difficult to obtain a predetermined magnetic field with the method using a magnet as shown in the publication. Therefore, in practice, the method is limited to methods using coils and ferromagnetic materials.

The second problem is the heat generated when using the coil.
In order to obtain the above-mentioned magnetic field, a magnetomotive force of about 3×10 ⁴ ampere turns is required. This typically requires several thousand turns and several tens of amperes of current. In order to obtain a large number of turns in a limited space, it is necessary to reduce the wire diameter.
When a predetermined current is applied, the amount of heat generated increases, and as a result, the wire coating becomes unbearable. In particular, if the magnet has different poles arranged alternately on the same surface, such as a magnet for a multi-pole motor, and the distance between the poles is 30 mm or less, the coils must be installed at a pitch of 30 mm or less. . In such an example, an extremely thin wire is required, the resistance value becomes extremely large, and it becomes difficult to even flow a predetermined current due to power supply limitations.

The third problem lies in the time for which the orienting magnetic field is continued. It is thought that the problem of heat generation can be solved by shortening the time during which current is passed through the coil. In other words, even if the current is about 5 × 10 ³ amperes, the pulse current should be applied for about 10 ^-2 seconds, and the time from one current to the next current should be sufficiently long (on the order of 10 ^-2 seconds). For example, by using a 1 mm diameter copper wire with a special coating, it can withstand heat generation. However, the time for which the orienting magnetic field should be maintained is much longer than this. That is, for example, in the magnetic field pressing process for sintered ferrite, the magnetic field must be continued during the pressing process until the density of the powder changes from a coarse state to a dense state, and in the injection molding process using a resin magnet. In this case, it is necessary to continue applying a magnetic field until the injection of the molten composition starts and the composition solidifies. This time is approximately several to ten-odd seconds, and sufficient orientation cannot be obtained in the pulsed magnetic field generated by the above-mentioned pulsed current because once oriented particles influence each other or are disrupted by external force.

Due to the above-mentioned problems, the ideal orientation shown in Figure 2 is not achieved using the magnetic field orientation method, and in reality, the apparatus shown in Figure 3 is used to achieve the ideal orientation.
It is common practice to perform the orientation shown in FIG. 4 and the magnetization shown in FIG. 5.

Figure 3 shows a cross section of the magnetic field orientation device.
Coils 7 and 8 are made of magnetic material, 9 and 10 are made of non-magnetic material, and 11 is a cavity space in which a magnet is formed. A magnetic field sufficient for orientation can be generated in the cavity 11, the direction of the magnetic lines of force is the direction connecting the magnetic bodies 7 and 8, and the density of the magnetic flux is approximately uniform everywhere.

FIG. 4 is a partial sectional view simulating the orientation state of the magnet obtained from the apparatus of FIG. 3.
The individual anisotropic magnet powders 13 constituting the magnet 12 are oriented in the same direction, and if one side of the magnet is the north pole, the back side is the south pole.

FIG. 5 is a partial sectional view schematically showing a magnetic circuit in a state in which the magnet shown in FIG. 4 is once demagnetized, a shield plate is bonded to the magnet, and the magnet is further magnetized.
By performing a magnetizing operation such that N and S poles are alternately provided on the same surface of the magnet 12, the lines of magnetic force passing through the inside of the magnet 12 are mainly concentrated on the back surface and then transferred to the adjacent magnet via the shield plate 14. It is understood that it shows a distribution that is connected to different poles.

As can be easily seen by comparing FIG. 2, this anisotropic magnet has a portion 13' between the poles that does not function effectively as a magnet, so the efficiency of the magnetic circuit is poor, and as a result, the magnetic flux is taken out to the pole surface. The amount decreases, and the magnetic flux density decreases compared to the ideal state. This means that the performance as a magnet is low, and the torque of a motor is small and the electromotive force of a dynamo is small.

The decrease in efficiency in the magnetic circuit illustrated in Figure 5 becomes more pronounced as the orientation rate of the anisotropic magnetic powder increases, and the improvement in magnetic properties in the orientation direction observed due to the increase in orientation rate (Br and BHmax ) can achieve only a practical effect that is far removed from that. For example, in a strontium ferrite resin magnet, the surface magnetic flux density was 840G when using a magnet with an orientation ratio of Br/Bs=0.87 and a BHmax of 1.2MGOe, whereas when Br/Bs=0.9, β
The one with the characteristic of Hmax1.6MGOe only improves to 880G. In this example, the value that can be expected proportionally is about 920G, and it is expected that a higher magnetic flux density can be obtained if more ideal orientation is performed.

The present invention provides a method for reducing the loss in such a magnetic circuit and providing a highly efficient magnetic circuit, and as described above, it is not an unrealistic method but can be fully put into practical use, and has a wide range of applications. This is a method that has a range.

That is, the present invention provides a highly efficient magnet by performing orientation in a magnetic field having density and density so that the magnetic field at the pole portion becomes stronger depending on the arrangement of the poles to be provided on the magnet surface. .

In order to deepen the understanding of the present invention, a simulated orientation model according to the present invention, which corresponds to FIGS. 2 and 4, is shown in FIG. 6. FIG. 6 shows the state after orientation, and the magnet 15 as a whole has poles such that one side is a N pole and the other side is an S pole. Powder 16 is pulled by a strong magnetic field and is facing toward the strong magnetic field, powder 17 is facing in the direction of the average magnetic field, and the anisotropy process has not been completed completely due to the weak magnetic field. It is understood that powders 18 oriented in a direction different from the overall orientation appear depending on the strength of the magnetic field.

FIG. 7 shows the direction of the lines of magnetic force when the magnet shown in FIG. 6 is demagnetized, a pole is provided in the strong magnetic field part, and the magnet is magnetized so that different poles are formed on the same surface. Area 19 consisting of averagely oriented powder, such as powder 17 in FIG.
If we characterize them as a region 20 consisting of strongly oriented powder such as powder 18, and a region 21 consisting of less oriented powder such as powder 18, the magnetic field lines A mainly pass through the region 21, as shown in FIG. Although the efficiency is lower than the ideal model, since the degree of anisotropy is low, the efficiency is higher than the orientation model shown in FIG. In addition, regarding magnetic field lines B, it is considered to be equivalent to the ideal model,
This is better than the model shown in Figure 5. Regarding the magnetic field lines C, both are considered to be equivalent. Therefore, as a whole, this method is superior to the conventional method and exhibits an orientation close to the ideal state.

Figures 6 and 7 are models for better understanding and are not exact.

In order to provide the above-mentioned orientation state, the orientation apparatus shown in FIG. 3 requires some ingenuity. This point is also one of the points of the present invention. That is, making it difficult for the magnetic lines of force that provide the orienting magnetic field to pass through, resulting in uneven magnetic flux density on the cavity surface;
In other words, a strong magnetic field section and a weak magnetic field section are provided.

In order to adjust the ease with which the lines of magnetic force pass, the present invention makes it possible by using a mold in which a weak magnetic material is placed in a ferromagnetic material near the cavity at a location where a weak magnetic field is required.

In order to deepen the understanding of the present invention, an example will be used to explain the present invention. FIG. 8 is a sectional view showing a mold apparatus for implementing the present invention. This device is a device for molding a resin magnet by injection molding and simultaneously performing magnetic field orientation. Coils 22, 23, magnetic material 24, on the fixed side and movable side, respectively.
25, non-magnetic materials 26 and 27 are provided, and a sprue hole 28 and a runner groove 29 are provided in the magnetic material on the fixed side. Further, a cavity 30 is provided between the magnetic body 24 and the magnetic body 25. Further, a non-magnetic material 32 is provided on the cavity surface of the magnetic body 25, and a non-magnetic material 31 is provided on the runner portion. By using such a mold, it is possible to generate a magnetic field of arbitrary strength or weakness in the cavity space by energizing the coil, depending on how the non-magnetic material is arranged. Thereafter, by injecting the resin magnet composition in a heated and molten state from a nozzle (not shown) of an injection molding machine into the cavity 30 through the sprue hole 28 and the runner 29, a predetermined orientation state can be obtained. After the resin in the cavity is cooled and solidified, the current to the coil is cut off and the mold is opened, thereby making it possible to obtain an oriented resin magnet molded product.

The ferromagnetic material referred to in this invention has a saturation magnetic flux density.
This refers to items over 10KG, and specific examples include:
There are commonly used steel materials such as SS41, S45C, S55C, SK3, SKD11, and SKD61. Of course, good magnetic materials with trade names such as Permendial, Sendust, and Permalloy are also ferromagnetic materials.

In addition, weakly magnetic materials include so-called non-magnetic materials such as stainless steel and Be-Cu alloy stainless steel SUS304, as well as ferrotic materials and cemented carbide steels, which exhibit a low saturation magnetic flux density of 10 KG or less depending on the processing method. Also included are solids and alloys.

FIG. 9 is an external view showing a molded product obtained by the mold shown in FIG. 8, and is drawn upside down from FIG. 8. On one surface of the molded product 33, regions 34 molded in contact with a ferromagnetic material and regions 35 molded in contact with a nonmagnetic material are alternately arranged. After once demagnetizing the obtained molded product, area 35
By magnetizing so that S and N poles are formed alternately, a magnet with excellent surface magnetic flux density can be obtained.

FIG. 10 shows a disk-shaped magnet obtained in the same manner, in which a magnet 36 and a shield plate 38 are bonded together, and a region 37 formed by contact with a ferromagnetic material is formed on a plane opposite to the bonded surface. There are 12 locations, and finally 6 N poles and 6 S poles are alternately provided. The magnetic flux density distribution of the magnet thus obtained is shown in FIGS. 11 and 12. FIG. 11 shows the distribution of the magnetic flux density on the plane after orientation in the circumferential direction as a comparison between the method of the present invention and the conventional method using a uniform magnetic field.

The magnetic flux density distribution according to the present invention is shown by curve A (solid line), and the magnetic flux density distribution according to the conventional method is shown by curve B (broken line). A magnet having such a magnetic flux density distribution can be used as it is as a magnet for detecting the number of rotations and the direction of rotation.

FIG. 12 shows the magnetic flux distribution after magnetization; similarly to FIG. 11, curve A shows the distribution according to the present invention, and curve B shows the distribution according to the conventional method. In this case, the maximum surface magnetic flux density was improved by about 20%.

FIG. 13 is a plan view showing a mold structure when the present invention is applied to a ring-shaped magnet. core 3
9 and the cavity plate 40 are made of ferromagnetic material, and the core 39 has six non-magnetic materials 4 around it.
2 are integrated. In such a configuration, if the coil and magnetic body according to the above-described configuration are arranged so that a magnetic field is generated between the core 39 and the cavity plate 40, the cavity space 41 will have a broken line 4
If the direction of the magnetic lines of force shown by 3 is obtained, and a resin magnet is molded in the same manner as in the previous example, a magnet that has been subjected to a predetermined anisotropic treatment can be obtained.

FIG. 14 is a partial sectional view of a mold showing another embodiment of the present invention. A non-magnetic body 46 is provided on each of the magnetic bodies 44 and 45 on the fixed side and the movable side,
The non-magnetic material 46 is arranged at the same pitch on the fixed side and the movable side, but the positions are shifted from each other, so that the lines of magnetic force 47 mainly occur obliquely.

FIG. 15 shows a practical form of the magnet obtained with the mold shown in FIG. 14, where 48 is a magnet, 49 is a shield plate, and the strongly oriented portion of the magnet 48 is shown as a short bar 50. It is shown in This strongly oriented portion corresponds to the portion where the lines of magnetic force 47 in FIG. 14 occur.

According to this method, it is possible to use the front side and the back side without distinction, so that it can be assembled with a shield plate without using a special detection device, and both sides can be used at the same time.

FIG. 16 is a partial sectional view showing another example of a mold for implementing the present invention, in which a cavity space 53 is arranged between a fixed magnetic body 51 and a movable magnetic body 52,
By providing a non-magnetic material 54 that does not appear on the cavity surface inside the movable magnetic material 52 near the cavity, a predetermined strength of the orientation magnetic field can be obtained. According to this embodiment, the complexity of mold assembly is removed, and even if non-magnetic materials with low wear resistance (for example, Be-Cu, Shinchiyu, SUS304, etc.) are used, extreme wear due to ferrite powder can be avoided. can be avoided.

Although many examples of resin magnets have been used in the embodiments of the present invention, the present invention is not limited thereto, and may also be implemented by an oriented pressing method in a sintering method.

In the embodiments of the present invention, what is mainly called a non-magnetic material is used as the weakly magnetic material, but as mentioned in the text, it is also possible to use a material with a low saturation magnetic flux density.

The effect of the present invention is mainly to improve the surface magnetic flux density of an anisotropic magnet, and its features include: 1. It employs a mold structure that can be extremely practically used.

2. The orientation form suitable for the product's magnetic circuit can be selected.

3. A magnetic circuit close to the ideal orientation state can be obtained.

Further, the present invention has the following unique effects.

(1) Since the polarity of the magnetic pole surface of the orienting device that comes into contact with the surface on which the magnetic poles of the magnet to be anisotropically treated is the same within that plane, the magnet can be A plurality of sets of orientations can be generated, and therefore, there is no need to increase the number of coils and magnetic poles for orientation according to the number of poles provided on the magnet, and the orientation device becomes simpler.

(2) At the time of magnetic field orientation, a magnetic field is generated between opposing magnetic poles in a form that traverses the inside of the magnet, so even if the magnetic permeability of the magnet is low, it is possible to suppress the deterioration of the function as an orientation device.

[Brief explanation of the drawing]

Fig. 1 is a model diagram explaining the anisotropy of anisotropic magnet powder, Fig. 2 is a model diagram explaining the ideal orientation state, and Fig. 3 is a cross-sectional view of a conventional anisotropy processing device. Fig. 4 is a model diagram showing the orientation state of the magnet obtained from Fig. 3, Fig. 5 is a model diagram showing the direction of the lines of magnetic force when the magnet is magnetized with the orientation shown in Fig. A model diagram showing the orientation form of the invention, FIG. 7 is a model diagram for explaining the form when magnetized in the orientation form of FIG. 6,
FIG. 8 is a sectional view of a mold according to an embodiment of the present invention, and FIG.
The figure shows an external view of a magnet obtained from the mold shown in Fig. 8, Fig. 10 shows an external view of a magnet according to another embodiment of the present invention, and Figs. 11 and 12 show the magnet in the shape of the magnet shown in Fig. A graph explaining the magnetic flux density distribution in the circumferential direction, FIG. 13 is a plan view of a mold according to another embodiment of the present invention, and FIG. 14 is a partial cross-sectional view of a mold according to yet another embodiment of the present invention. Figure 15 is the 14th
FIG. 16 is a sectional view showing a state in which a magnet obtained by the mold shown in the figure is used, and FIG. 16 is a partial sectional view of a mold showing still another embodiment of the present invention.

Claims (1)

[Scope of Claims] 1. In a method for producing a magnet in which anisotropic treatment is performed using a magnetic field orientation method, and then a plurality of poles are provided on the same surface, the magnet is The anisotropic treatment is performed using an orientation device in which the pole-corresponding parts are made of a ferromagnetic material and the inter-pole corresponding parts are made of a weakly magnetic material so that the polarities are the same and the strength of the magnetic field is determined according to the arrangement of the poles. The manufacturing method of the anisotropic magnet. 2. A patent characterized in that a magnet subjected to anisotropy treatment is further magnetically treated so that at least one of the plurality of poles is made different from the others when the ferromagnetic material equivalent portion is made into a pole. A method for manufacturing an anisotropic magnet according to claim 1.