JP2000040611A - Resin coupled permanent magnet material and magnetization thereof as well as encoder using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the magnetization in the lower magnetic field also displaying extremely high coersive force once magnetized, by a method wherein, in the material containing MnBi magnetic powder in a specific particle size and a resin binder, the coersive force acquired by impressing a magnetic field in a specific condition is specified. SOLUTION: This permanent magnet material is composed of a mixture of MnBi in the mean particle size of 0.1-20 μm and a resin binder. Desirably, the content of the resin binder is set up to be 0.3-20 wt.% to 100 wt.% of the MnBi. As for the magnetic powder, it is recommemded that the MnBi magnetic powder is applied with the coersive force measured by impressing the magnetic field of 16 KOe within the range of 500 Oe-16000 Oe. In such a constitution, when this magnetic powder is mixed with the resin binder to be compression- molded in the magnetic field making a specific shape and then initiated, the mixture can be easily magnetized at room temperature. Furthermore, the mixture once magnetized can display the extremely high coersive force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a resin-bonded permanent magnet material using MnBi magnetic powder, an encoder using the same, and a method of magnetizing the resin-bonded permanent magnet material. The resin-bonded permanent magnet material of the present invention is suitable for an encoder used as a control means of, for example, a stepping motor or a servomotor.

[0002]

2. Description of the Related Art Resin-bonded permanent magnet materials require high dimensional accuracy because of their high dimensional accuracy, complex shapes, and good uniformity of quality and performance. It is frequently used in equipment and the like. Conventionally, as this type of magnetic powder for a resin-bonded permanent magnet material, a Sm-Co-based or Nd-Fe-B-based magnetic powder having a normally high coercive force,
Magnetic powders such as Ba ferrite and Sr ferrite are used.

The performance of a permanent magnet is generally represented by the product of a coercive force and a residual magnetic flux, and the larger the value, the higher the performance of the magnet. On the other hand, in order to make the above magnetic powder having a large magnetic anisotropy into a permanent magnet material,
After molding into a permanent magnet having a predetermined shape, it is necessary to apply a magnetic field larger than the coercive force of the magnetic powder in a specific direction to perform magnetization. When it is sufficient to simply magnetize in one direction as in the simplest permanent magnet, the magnet can be magnetized by applying a uniform pulse magnetic field larger than the coercive force to obtain a permanent magnet material.

[0004]

However, permanent magnets for motors used in small electronic equipment, rotary encoders used for controlling the rotation of motors such as stepping motors and servomotors, and position control of driving parts In a linear encoder and the like used in the above, more delicate operation control is required, and therefore, it is required to form a more minute magnetized pattern inside the permanent magnet material. In such an application, it is difficult to magnetize with the above-described uniform pulse magnetic field, and it is necessary to locally apply a magnetic field to a specific portion of the magnet using a magnetic head or the like to form an arbitrary magnetized pattern. . In this case, since there is a limit to the magnetic field that can be generated by the magnetic head or the like, the coercive force of the magnetic powder used is naturally limited.

Therefore, it is desirable to use a high coercivity Sm-Co or Nd-Fe-B magnetic powder as a permanent magnet material. However, in the above-mentioned applications, a high coercivity magnetic powder is used. Since it cannot be used, it is at most 3000 as a magnetic powder for a resin-bonded permanent magnet material.
At present, it is limited to magnetic powder such as Ba ferrite or Sr ferrite of about Oe.

Also, when a permanent magnet using a magnetic powder having a coercive force of about 3000 Oe as a material as described above is magnetized by a magnetic head, a magnetic field larger than the coercive force of the magnet is applied as described above. This necessitates a large head gap of the magnetic head, which makes it difficult to record a magnetized pattern at a high recording density.

Further, in applications such as encoders,
In order to obtain high detection sensitivity, it is necessary to increase the performance as a permanent magnet as much as possible, and for that purpose, it is necessary to increase the coercive force as much as possible simultaneously with the residual magnetic flux as described above. In addition, when the encoder is used to control the rotation of a motor, a permanent magnet with a high coercive force may be installed near the motor, and the encoder is reduced due to the leakage magnetic field of the permanent magnet. There is a problem that it is easily magnetized and the detection sensitivity is easily lowered.

An object of the present invention is to provide a permanent magnet material that is optimal for applications such as an encoder and the like, which can be easily magnetized with a low magnetic field by a magnetic field applying means such as a normal magnetic head, and that once magnetized, an extremely large coercive force is obtained. To provide a resin-bonded permanent magnet material having high magnetic energy,
And an encoder using the same and a method of magnetizing the magnet material.

[0009]

That is, the resin-bonded permanent magnet material of the present invention contains MnBi magnetic powder having an average particle size of 0.1 μm or more and 20 μm or less, and a resin binder. The coercive force measured by applying a magnetic field is 3000 Oe or more and 16000 Oe or less. Preferably, the content of the resin binder is 0.3 to 100 parts by weight of the MnBi magnetic powder.
Set to ~ 20 parts by weight.

The encoder of the present invention uses the above-mentioned resin-bonded permanent magnet material, has a permanent magnet material as a constituent member, and the permanent magnet material is made of the resin-bonded permanent magnet material. It is characterized by being.

Further, the method of magnetizing a resin-bonded permanent magnet material of the present invention is a method of forming a predetermined magnetization pattern on a resin-bonded permanent magnet material containing MnBi magnetic powder and a resin binder. Wherein the resin-bonded magnet material is formed into a desired shape in a magnetic field, cooled to a low temperature to be in a demagnetized state, and magnetized by applying an external magnetic field at room temperature. In this case, as the means for applying the external magnetic field, an electromagnet, a permanent magnet, a magnetic head, or the like can be used.

As a characteristic required of the resin-bonded permanent magnet material, a large coercive force and a large residual magnetic flux are required as described above, and when used as a permanent magnet material for an encoder, the detection sensitivity is low. It is necessary to have the contradictory characteristics that it is high and can be easily magnetized at the time of magnetization. In addition, because high dimensional accuracy is required, the resin-bonded permanent magnet material must be a kneaded mixture of magnetic powder and a resin binder, and it is necessary to mold this into a predetermined shape. Dispersibility in a mixed state is also required. Further, in order to be magnetized by a magnetic head or the like and to facilitate detection as an encoder, the magnetic powder is required to have a filling property of magnetic powder and a surface property of a molded product. Therefore, it is necessary to use a magnetic powder having a small particle size.

The present inventors have studied various magnetic powders based on such knowledge, and have found that the above problems can be solved at once by using a MnBi magnetic powder and using a specific magnetizing method. That is, the MnBi magnetic powder shows a very large coercive force of about 5000 Oe or more at room temperature, but has a coercive force of 500 Oe or less at a low temperature. Further, after cooling the MnBi magnetic powder to a low temperature,
When the temperature is returned to room temperature (15 to 30 ° C.) (that is, after initialization), a signal can be easily recorded at room temperature, and once recorded, the coercive force becomes 5000 Oe or more before the initialization. It has the characteristic that it cannot be rewritten or erased. In addition, it is possible to obtain a fine particle powder suitable as a magnetic powder for a resin-bonded permanent magnet material used in an encoder, and since the magnetic powder has a crystalline anisotropy, the finer the particles, the higher the coercive force. It also has

Therefore, Mn having such properties
When the Bi magnetic powder is mixed with a resin binder, and compression-molded into a predetermined shape in a magnetic field and then subjected to an initialization treatment, the magnetic material can be easily magnetized at room temperature, while once magnetized, it exhibits an extremely large coercive force. Thus, the resin-bonded permanent magnet material exhibits excellent performance. If this resin-bonded permanent magnet material is used, a high-performance permanent magnet material having good dimensional accuracy and a fine magnetized pattern required for delicate operation control can be produced as a constituent member for the encoder. . In addition, since the encoder having the high-performance permanent magnet material obtained as a constituent member has a high detection sensitivity, the encoder may be included in a drive control system including a control motor such as a stepping motor or a servomotor. In cooperation with the electric or mechanical means, the rotation of the control motor can be more finely controlled. Further, by utilizing the above properties of the MnBi magnetic powder for a resin-bound permanent magnet material,
New applications that could not be realized with conventional resin-bonded permanent magnet materials can be developed.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below. [Example of magnetization curve of permanent magnet material according to the present invention] FIG.
Shows an example of a magnetization curve of a resin-bonded permanent magnet material using MnBi magnetic powder. This permanent magnet material was prepared by mixing MnBi magnetic powder having an average particle size of 1.8 μm with a resin binder and compression-molding in a magnetic field. After initializing the material, the initial magnetization curve and demagnetization curve were measured at room temperature. Things. From this figure, it can be seen that when initialization is performed by cooling to a low temperature, magnetization can be easily performed at room temperature with a magnetic field as low as about 2000 Oe, but once magnetized, an extremely large coercive force of about 11000 Oe is exhibited.

[Production Method of MnBi Magnetic Powder] Next, a production method of the MnBi magnetic powder will be described. The MnBi magnetic powder used in the present invention is obtained by powder metallurgy, arc furnace melting, high frequency melting, melting quenching, or the like.
Bi ingot is manufactured by crushing the ingot. For example, in the case of manufacturing by the powder metallurgy method, the ingot is manufactured as follows, divided into a process of manufacturing the ingot, a process of pulverizing the ingot, and a stabilization process. Note that MnBi magnetic powder may be used instead of the pulverization method.

Production of Ingot In production of an ingot, Mn powder and Bi powder of 50 to 300 mesh are sufficiently mixed, and the mixture is pressed under pressure to form a molded body, thereby producing an ingot. When Mn powder and Bi powder are mixed, the ratio (Mn / Bi) is 4 in molar ratio.
Preferably, the ratio is in the range of 5:55 to 65:35.
When Mn is increased as compared with i, the corrosion resistance of the MnBi magnetic powder is improved by forming an oxide or hydroxide of Mn on the surface of the MnBi magnetic powder, and a good quality magnetic powder can be obtained. Therefore, it is more preferable to increase Mn as compared with Bi.

As the Mn powder and Bi powder used here, it is preferable to use those having a small impurity content. However, when adjusting the magnetic characteristics, Ni and A powders should be added.
Metals such as l, Cu, Pt, Zn, and Fe are used in addition. When such a metal is added, the magnetic property can be controlled well by setting the addition amount to 0.6 at% or more with respect to MnBi, and by adding less than 5.0 at% to MnBi. Since the crystal structure itself can be favorably maintained and the original characteristics of MnBi can be exhibited, it is preferable that the content be in the range of 0.6 to 5.0 atomic%. In addition, it is preferable that an alloy of Mn and these elements is prepared in advance as a method of adding these elements.

As the Mn powder or Bi powder, a powder that has been pulverized in advance may be used, or a lump such as flakes or shots may be pulverized into fine powder for use. In the case of synthesizing by sintering reaction, MnBi is generated by a diffusion reaction through a contact interface between Mn and Bi. Therefore, when Mn powder and Bi powder are finely divided into 50 to 300 mesh, the generation reaction is smooth. move on. Mixing of these Mn powder and Bi powder is performed by any means such as an automatic mortar and a ball mill.

When the Mn powder and the Bi powder are pressed and formed into a molded body, the pressing force is preferably set to 1 to 8 t / cm ^2. As a result, the sintering reaction is promoted to produce a uniform ingot. By setting the pressure to 1 t / cm ² or more, MnBi
The ingot can be made more uniform, and productivity can be improved by setting the ingot to 8 t / cm ² or less.

The obtained molded body is sealed in a glass container or a metal container, and the inside of the container is set to a vacuum or an inert gas atmosphere to prevent oxidation during the heat treatment. As the inert gas, hydrogen, nitrogen, argon, or the like can be used, but nitrogen gas is used as the optimal gas in terms of cost. The container in which the molded body is sealed in this way is then placed in an electric furnace and heat-treated at 260 to 271 ° C for 2 to 15 days. By setting the heat treatment temperature to 260 ° C. or higher, the heat treatment can be performed in a short time, the amount of magnetization of the obtained ingot can be increased, and by setting the temperature to 271 ° C. or lower, the melting of Bi can be suppressed and uniform. It is preferable to perform the process immediately below the melting point of Bi, since a proper ingot can be obtained.

Pulverization of Ingot The MnBi ingot produced as described above is taken out and coarsely pulverized in advance in an inert gas atmosphere using an automatic mortar or the like, and the particle size is adjusted to 100 to 500 μm. Then, the particles are formed into fine particles by the impact due to the collision between the particles or the wall of the container by wet pulverization utilizing the impact of a ball using a ball mill, a planetary ball mill or the like, or dry pulverization such as a jet mill.

In the pulverization utilizing the impact of the ball, as the pulverization progresses, the diameter of the ball is reduced stepwise to obtain a magnetic powder having a more uniform particle diameter. Originally, since MnBi has a hexagonal structure, it shows a property of cleavage, so that it is not necessary to pulverize with high energy. It is preferable to use an organic solvent as the liquid in the case of wet pulverization, and it is also preferable to use a non-polar solvent such as toluene as the organic solvent and remove dissolved water in the solvent in advance. On the other hand, in the case of dry pulverization, it is preferable to perform the pulverization in a non-oxidizing atmosphere. As the non-oxidizing atmosphere, a vacuum or an inert gas atmosphere such as a nitrogen gas or an argon gas is preferably used.

The MnBi magnetic powder thus obtained has an average particle size in the range of 0.1 μm to 20 μm, and the particle size can be controlled by pulverizing conditions. By making the particle diameter larger than 0.1 μm, the saturation magnetization of the finally obtained magnetic powder can be increased, and by making the particle diameter 20 μm or less, the coercive force of the magnetic powder can be sufficiently increased. The moldability at the time of compression molding or injection molding by mixing with a resin binder is improved, preferably from 0.3 μm to 10 μm,
More preferably, it is 0.5 μm or more and 5 μm or less.

By the above steps, a MnBi magnetic powder contained in the permanent magnet material of the present invention is obtained. At this time, the coercive force measured by applying a magnetic field of 16 kOe and being 5000 Oe to 16000 Oe at 300 K is applied.
It is preferable to use a MnBi magnetic powder in the range described above. This is because the coercive force of the permanent magnet material also depends on the filling property of the magnetic powder, so that if it is less than 5000 Oe, the coercive force decreases if the filling property is excessively increased when mixed with the resin binder. If the ratio is high, the productivity becomes difficult because the magnetic powder needs to be finely divided. Considering the productivity of the magnetic powder and the dispersibility in the resin binder, the saturation magnetization of the MnBi magnetic powder is desirably 30 to 50 emu / g when a magnetic field of 16 kOe is applied at a temperature of 300K.

Stabilization Treatment The MnBi magnetic powder produced by such a method is preferably further subjected to a stabilization treatment. Here, as a typical example, a method of forming a coating film of Mn and Bi oxides on the surface of MnBi magnetic powder using oxygen will be described. First, the MnBi magnetic powder is heated at a temperature of 20 to 150 ° C. in a nitrogen gas or an argon gas containing about 100 ppm to 10,000 ppm of oxygen. The heating time is suitably about 0.5 to 40 hours. It is preferable that the lower the temperature is, the longer the heating time is. By this treatment, oxides of Mn and Bi are formed. In particular, in this treatment, an oxide of Mn, which greatly contributes to the chemical stability of the MnBi magnetic powder, is preferentially formed. As the degree of oxidation increases, the oxide film formed near the surface becomes thicker and the chemical stability improves, but the initial value of the saturation magnetization decreases.

[Resin Binder Used in the Present Invention] As the resin binder for binding used in the present invention, conventionally known resins can be used. For example, in the case of compression molding, epoxy resin, phenol Curable resins such as a base resin can be cited as preferable ones.In the case of injection molding, polyamide resins such as nylon, polyolefin resins such as polypropylene, and polyester resins such as polyethylene terephthalate are preferable. Can be.

The amount of the resin binder was as follows: MnBi magnetic powder 1
The amount is preferably from 0.3 to 20 parts by weight, more preferably from 0.5 to 10 parts by weight, per 100 parts by weight. When the content is 0.3 parts by weight or more, the mechanical strength of the permanent magnet material after the resin is cured can be further increased, and the wear of the mold can be reduced. On the other hand, by setting the content to 20 parts by weight or less, MnBi
The filling amount of the magnetic powder can be improved, and high magnetic properties can be obtained.

[Molding Method] Compression molding or injection molding can be performed according to a conventional method. For example, in the case of compression molding, a MnBi magnetic powder and a resin binder are mixed, and this mixture is supplied to a press molding die. In the case of an oriented magnet, press molding is performed while applying a magnetic field. It is obtained by heating and curing the resin.

[Coercive force of resin-bonded permanent magnet material] The coercive force of the resin-bonded permanent magnet material obtained as described above depends on the conditions at the time of magnetization.
When a magnetic field of 16 KOe was applied at 3000
e to 16000 Oe, preferably 5000 Oe to 16000 Oe, more preferably 7000 Oe to 16000 Oe. That is, 3
At 000 Oe or less, the magnetic energy, which is the performance of the permanent magnet material, becomes small, so that a high output cannot be obtained when used in an encoder. In addition, when a permanent magnet having a high coercive force is installed near the magnet of the present invention. In addition, the effect of the demagnetization due to the leakage magnetic field cannot be ignored. On the other hand, 16
If it is 000 Oe or more, the productivity will be reduced because the MnBi magnetic powder needs to be finely divided. The coercive force (iHc) is a value obtained by applying a magnetic field at 300 K in a direction opposite to the direction of application of a magnetization magnetic field of 16 KOe and measuring the value of the magnetic field at which the magnetization becomes zero.

[Magnetization method] Next, MnBi as described above is used.
The basic operation of the method for magnetizing a permanent magnet material according to the present invention containing a magnetic powder and a resin binder will be described.

In the case of an oriented magnet, the resin-bonded permanent magnet material produced as described above is already magnetized because a magnetic field is applied at the time of molding, and thus has a coercive force of 30%.
Since the coercive force is not less than 00 Oe and not more than 16000 Oe, a normal magnetic head or the like cannot provide a sufficient magnetic field strength to perform sufficient magnetization, and cannot provide a magnetization pattern with a high recording density. .

Therefore, it is necessary to first perform a low-temperature treatment on the permanent magnet material so as to be able to be magnetized at room temperature as an initialization process. That is, by this low-temperature treatment, the coercive force of the MnBi magnetic powder becomes 500 Oe or less, and when the temperature is returned to room temperature in this state, the magnetization can be easily performed.
In addition, since magnetization can be performed with such a low coercive force, the gap length of the magnetic head can be reduced so that magnetization can be performed even in a low magnetic field. Can be achieved.

The temperature for the low-temperature treatment is preferably 100 K or lower, more preferably, liquid nitrogen temperature (77 K) or lower. The processing time is 10 seconds to 20 minutes, more preferably 1 minute to 10 minutes, in consideration of productivity.

The magnet demagnetized as described above is
By taking out at room temperature (15 ° C. to 30 ° C.) and applying an external magnetic field, the permanent magnet material of the present invention is initialized and a magnetization pattern can be recorded. In this case, as described above, since the magnet material has already been initialized,
It can be easily magnetized by ordinary application means. As a means for applying an external magnetic field, an application means such as an electromagnet, a permanent magnet, or a magnetic head can be used. In particular, when it is necessary to record a fine magnetized pattern such as an encoder, a high recording density can be achieved by magnetizing the permanent magnet material of the present invention using a magnetic head.

By the above-described magnetization, the permanent magnet material of the present invention has a high coercive force of 3000 Oe or more and 16000 Oe or less, exhibits excellent magnetic energy as a magnet performance, can obtain a high output, and has a high output. With the method, demagnetization becomes extremely difficult.

In order to obtain more excellent characteristics as an encoder, it is preferable that the magnetic powder is molded in a magnetic field to orient the magnetic powder in a specific direction as described above. On the other hand, when a magnetic field is not applied during molding, the magnetic powder becomes non-oriented. In that case, the performance as a permanent magnet, that is, the coercive force and the residual magnetic flux, are lower than when oriented in a specific direction, but since the magnetic powder is not magnetized, without performing the above-described initialization processing, It has the advantage that it can be magnetized. Therefore, when the permanent magnet material of the present invention is used, even such a non-oriented resin-bonded permanent magnet material has more excellent characteristics than the conventional resin-bonded permanent magnet material.

[0038]

Embodiments of the present invention will be described below. (Example 1) << Preparation of MnBi magnetic powder >> Mn powder and Bi powder pulverized to a particle size of 200 mesh were mixed with M powder.
n and Bi were weighed so that the molar ratio was 55:45, and were sufficiently mixed using a ball mill.

Next, these mixtures were crushed at a pressure of 3 tons / cm ² using a press machine to a diameter of 20 mm and a height of 10 mm.
Into a cylindrical shape. The molded body was placed in a sealed aluminum container, and after vacuum was drawn, nitrogen gas was introduced at 0.5 atm. Next, the container was placed in an electric furnace and heat-treated at a temperature of 270 ° C. for 10 days. After the heat treatment, the MnBi ingot was taken out into the air, crushed lightly in a mortar, and the magnetic properties were measured. The coercive force measured by applying a maximum magnetic field of 16 kOe at 300 K is 840 Oe, and the magnetization amount is 53.6 emu.
/ G.

Next, the above coarsely pulverized MnBi powder was
It was pulverized using a planetary ball mill. Internal capacity 1000cc
Zirconia balls with a diameter of 3 mm in the ball mill pot
It was filled so as to occupy 1/3 of the internal volume. Into this, 500 g of roughly pulverized MnBi powder and 500 g of toluene as a solvent were added, and pulverized at 150 rpm for 4 hours. The obtained MnBi magnetic powder was taken out, toluene was evaporated, and then the magnetic properties were measured. The coercive force and the amount of magnetization measured by applying a maximum magnetic field of 16 KOe at a temperature of 300 K were 8600 Oe and 39.2 emu, respectively.
/ G.

The MnBi magnetic powder obtained by the above method was subjected to a stabilization treatment by the following method. The MnBi magnetic powder was taken out in a state of being immersed in toluene, transferred to a heat treatment vessel, and vacuum dried at room temperature for about 2 minutes. Next, while keeping the same container, nitrogen gas containing 1000 ppm of oxygen was introduced at 1 atm, and heat treatment was performed at a temperature of 40 ° C. for 15 hours.

The Mn finally obtained by the above method
The average particle size of the Bi magnetic powder is 1.8 μm and the temperature is 300
The coercive force and the magnetization amount measured by applying a maximum magnetic field of 16 KOe at K are 8500 Oe and 46.3, respectively.
emu / g.

<< Preparation of Resin-Bound Permanent Magnet Material, etc. >> To 100 parts by weight of the MnBi magnetic powder prepared by the above method, 5 parts by weight of an epoxy resin containing a curing agent dissolved in methyl ethyl ketone was added, and the mixture was thoroughly mixed and dispersed. After that, a deorganizing agent treatment was performed in a vacuum. Next, the MnBi magnetic powder containing the resin binder obtained in this manner was applied to an outer shape 25.
The powder was fed into a mold having a concave portion having a diameter of 21 mm, an inner diameter of 21 mm and a depth of 30 mm, and was molded under a magnetic field of 16 KOe at a pressure of 5 ton / cm ² . The molded body is further heated at 130 ° C. for 20 minutes,
The resin binder was cured to obtain a resin-bonded permanent magnet material. Then, as an initialization treatment, the molded body (resin-bonded permanent magnet material) was cooled at liquid nitrogen temperature for 10 minutes, and then returned to room temperature.

Example 2 A molded article was prepared in the same manner as in Example 1, except that the amount of the epoxy resin containing the curing agent was changed from 5 parts by weight to 2 parts by weight.
A resin-bonded permanent magnet material was obtained. The obtained resin-bonded permanent magnet material was subjected to an initialization treatment in the same manner as in Example 1, and then returned to room temperature.

(Example 3) In Example 1, MnBi
As a magnetic powder, the average particle size is 1.2 μm and the temperature is 300
The coercive force and the magnetization amount measured by applying a maximum magnetic field of 16 kOe at K are 11200 Oe and 39.
A molded body was produced in the same manner as in Example 1 except that a material having a viscosity of 4 emu / g was used, and a resin-bonded permanent magnet material was obtained. The obtained resin-bonded permanent magnet material was subjected to an initialization treatment in the same manner as in Example 1, and then returned to room temperature.

Comparative Example 1 The procedure of Example 1 was repeated except that the resin-bonded permanent magnet material obtained in Example 1 was not initialized.

(Comparative Example 2) A molded body was produced in the same manner as in Example 1 except that NdFeB magnetic powder having a coercive force of about 12000 Oe was used as the magnetic powder in Example 1, and a resin-bonded permanent magnet material was prepared. I got

(Comparative Example 3) A molded body was produced in the same manner as in Example 1 except that a Sr ferrite magnetic powder having a coercive force of 2800 Oe was used as the magnetic powder in Example 1, and a resin-bonded permanent magnet material was prepared. I got

(Evaluation) Examples 1-3 and Comparative Examples 1-3
A part of the resin-bonded permanent magnet material obtained in the above was cut out, and the magnet performance and the magnetization were evaluated by the following methods. The following measurement temperatures were all 300K.

Among the magnet performances, the residual magnetic flux was measured in a state after molding in a magnetic field of 16 KOe, and this value was expressed as Br (+16
K).

Regarding the magnetism, as a measurement sample, in Examples 1 to 3, a sample subjected to an initialization treatment separately from the sample whose residual magnetic flux was measured was used, and 5000 Oe was applied in a direction opposite to the direction applied during the magnet forming process. And the residual magnetic flux B
r (−5K) was measured, and the ratio with the above Br (+ 16K) was determined.
That is, evaluation was made from the value of Br (−5K) / Br (+ 16K). That is, when this value is negative, -5000 Oe
This indicates that the magnetization is easily reversed by application of the reverse magnetic field, and that the closer the value is to -1, the more excellent the permanent magnet is.

Among the magnet properties, the coercive force (iHc) was measured by measuring a hysteresis curve in a magnetic field of 16 KOe after the magnetization measurement, and a magnetic field (iHc) at which the magnetic flux became 0 G in the hysteresis curve. The performance as a permanent magnet is
It was evaluated from the value of iHc × Br (+ 16K). That is, the larger the value, the better the magnet performance.

Table 1 shows Examples 1 to 3 and Comparative Examples 1 to 3.
Br (-5K), Br (+ 16K), Br
(−5K) / Br (+ 16K), and iHc × Br
The results of (+ 16K) are shown.

[0054]

[Table 1]

In Table 1, Br (-5K) / Br (+
16K) has a positive value (Comparative Example 1 and Comparative Example 2). This is because even if a magnetic field of 5000 Oe is applied in a direction opposite to the magnetic field applied at the time of magnetization, iHc is 5000 Oe.
This is because magnetization reversal can hardly be performed because of being larger than e.

As is clear from Table 1, the MnB of the present invention
Example 1 Using i Magnetic Powder and Initializing
The resin-bonded permanent magnet materials of Nos. 1 to 3 are Br (-5K) / B
r (+ 16K) shows a value close to -1, good magnetization performance, and iHc × Br (+ 16K) also shows a large value;
Magnet performance is also excellent.

On the other hand, even in the case where the MnBi magnetic powder was used, in Comparative Example 1 where no initialization treatment was performed, Br was used.
The value of (−5K) / Br (+ 16K) is positive, which indicates that magnetization is difficult.

In Comparative Example 2 using NdFeB magnetic powder, iHc × Br (+ 16K) is large and magnet performance is excellent, but Br (−5K) / Br (+ 16K) is a positive value. Moreover, since the value is close to +1, 500
It can be seen that at a magnetic field of about 0 Oe, the magnetization is not reversed and the magnetization is hardly possible.

Further, Comparative Example 3 using Sr ferrite
In this case, since the iHc is low, Br (+ 5K) / Br (+16
K) indicates a negative value, indicating that the magnetism is relatively good, but on the other hand, iHc × Br (+ 16K) is small due to low iHc, and magnet performance is inferior.

Thus, each of the resin-bonded magnet materials of Examples 1 to 3 of the present invention using the MnBi magnetic powder and subjected to the initialization treatment is easy to magnetize and has good magnet performance after magnetization. It has been confirmed that extremely useful characteristics that cannot be realized with ordinary magnet materials can be realized.

[0061]

As described above, the resin-bonded permanent magnet material of the present invention using the MnBi magnetic powder and subjected to the initialization treatment exhibits excellent magnetizability that can be easily magnetized in a low magnetic field. Further, once magnetized, it exhibits a large coercive force, and thus exhibits excellent magnet performance. Such characteristics cannot be realized by the conventional resin-bonded magnet material, but can be realized for the first time by the resin-bonded magnet material of the present invention.
The resin-bonded permanent magnet material of the present invention is particularly effective in a magnetic head having a limited generated magnetic field strength, an encoder which needs to form an arbitrary magnetized pattern using a permanent magnet, or the like. According to the magnetization method of the present invention, a required magnetization pattern can be easily formed on the resin-bonded permanent magnet material according to the intended use.

[Brief description of the drawings]

FIG. 1 is a diagram showing an initial magnetization curve and a demagnetization curve of a resin-bonded permanent magnet material according to the present invention.

Claims (5)

[Claims] 1. An average particle size of 0.1 μm or more and 20 μm or more.
A resin-bonded permanent magnet material comprising the following MnBi magnetic powder and a resin binder, wherein a coercive force measured by applying a magnetic field of 16 KOe at a temperature of 300 K is 3,000 Oe to 16,000 Oe. 2. The resin-bonded permanent magnet material according to claim 1, wherein the content of the resin binder is 0.3 to 20 parts by weight based on 100 parts by weight of the MnBi magnetic powder. 3. An encoder having a permanent magnet material as a constituent member, wherein the permanent magnet material is made of the resin-bonded permanent magnet material according to claim 1. 4. A magnetizing method for forming a predetermined magnetized pattern on a resin-bonded permanent magnet material containing MnBi magnetic powder and a resin binder, wherein the resin-bonded permanent magnet material is formed in a magnetic field. A method of magnetizing a resin-bonded permanent magnet material, comprising: forming into a desired shape, cooling to a low temperature to be in a demagnetized state, and magnetizing at room temperature by applying an external magnetic field. 5. The method according to claim 4, wherein the external magnetic field is applied by any one of an electromagnet, a permanent magnet, and a magnetic head.