JP2007208104A - Compound bond magnet molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pole anisotropic compound bond magnet by arranging a rare-earth magnet by selectively filling it into a pole-oriented magnetic pole part to control a high surface magnetic flux density characteristic and corrugated magnetic flux density on the surface of the magnet, not by arranging the rare-earth magnet all over the entire ring circumference as before in order to solve the problem of a conventional technology. <P>SOLUTION: The compound bond magnet is the pole anisotropic compound bond magnet molding having a plurality of magnetic poles on its surface and mainly comprises a ferrite resin composite of the bond magnet molding with the rare-earth magnet arranged at a plurality of magnetic poles on its surface. The rare-earth magnet of the magnetic pole part comprises at least one of an NdFeB system alloy, an SmFeN system alloy, and an SmCo system alloy. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a bonded magnet molded body having a multi-surface configuration.

  In recent years, with the improvement in performance of motors using permanent magnets, there has been an increasing demand for magnetic properties of the permanent magnet materials used.

  By realizing high performance of permanent magnets, motors are expected to have significant effects in various areas, such as improvement of basic performance, concomitant miniaturization and reduction of manufacturing costs, and reduction of energy consumption due to high efficiency. it can. Therefore, the development of permanent magnet materials that achieve a high energy product is progressing, while efforts are made to maximize the surface magnetic flux density by optimizing the magnetic circuit using the permanent magnet. In the former case, the basic material cost is increased to improve the performance of the permanent magnet material. On the other hand, in the latter case, although magnetic characteristics can be improved only by the magnetic circuit design technology and there is an advantage that it is economical, there are many things that can be realized by improving the basic performance of the constituent materials. .

  Generally, techniques for manufacturing a ring-shaped bonded magnet molding include an injection magnetic field molding technique and a compression magnetic field molding technique.

  In the injection magnetic field molding technique, permanent magnet powder such as ferrite powder, alnico powder, Sm-Co powder, Nd-Fe-B powder, or Sm-Fe-N powder is used as a thermoplastic resin (for example, nylon). Mix and knead in an environment with air or inert gas at a temperature of 150 to 300 ° C. to make a compound, and further heat the compound at a temperature of 150 to 300 ° C. to give fluidity. Then, it is poured into a mold to form a bonded magnet molded body. By using a magnetic powder having uniaxial anisotropy as the magnetic powder to be used and injecting the compound into a mold having a fixed shape while applying a magnetic field, it is possible to produce a magnetic pole having an arbitrary position.

  On the other hand, the compression magnetic field molding technique is made of a permanent magnet powder such as ferrite powder, alnico powder, Sm-Co powder, Nd-Fe-B powder, or Sm-Fe-N powder, and a thermosetting resin such as epoxy. And then knead in an environment with air or inert gas at room temperature to 100 ° C to make a compound, and after filling the formed compound into a fixed shape mold, it is molded and bonded magnet molded body Get. By using a powder having uniaxial anisotropy in the magnet powder as described above, a magnetic field is applied during molding to orient the compound in the magnetic field direction, and at the same time by performing compression molding, it can be placed at any position as described above. Bonded magnets having magnetic poles can be formed.

  In other words, in the method of manufacturing a bonded magnet, a powder is oriented in the direction of the magnetic field by filling the cavity of the mold with a compound and forming a magnetic field using a permanent magnet or an electromagnet. It is important to align. In this case, as shown in FIG. 2a, the magnetic field orientation direction of the magnet radiates from the center of the ring to the outside of the ring (in the direction of the arrow) is a radial magnet, and multipolar magnetization is performed. In the radially oriented magnet, NS poles appear so as to be paired on both sides of the magnet. When the surface magnetic flux density is measured along the circumference of the radial magnet, a sawtooth surface magnetic flux density is obtained. However, when this radially oriented magnet is used as a bonded magnet for a rotor, although it has excellent magnetic properties, the magnetic attractive force between the motor magnet and the armature silicon steel sheet increases due to the sawtooth surface magnetic flux density distribution, thereby cogging. There is a problem that there is a possibility of causing (cogging) development.

  On the other hand, as shown in FIG. 2b, the pole-oriented magnet has NS poles appearing on one surface of the magnet, and the orientation direction is such that NS poles hardly appear on the opposite side (back side). ing. A pole-oriented magnet generally has a surface magnetic flux density of 30 to 40% higher than that of a radial magnet of the same material and the same number of poles and size. Therefore, a sinusoidal waveform can be easily obtained when applied to a motor. There are advantages to being

  However, since an extra material is required to form a magnetic path to the inside of the magnet, there is a problem that the material cost becomes high. Most of such polar-oriented magnets are formed of injection-molded bonded magnets or sintered magnets using ferrite magnetic powder. Recently, a method of forming a polar orientation magnet by injection molding using rare earth magnet powder has been disclosed.

  Such a rare earth powder having a strong magnetic force is effective in improving the magnet performance, but the material cost is about 10 times higher than that of the ferrite powder having a low magnetic property, so that it is essential to reduce the thickness.

As already known as a problem in thinning, cracks in the cooling process during molding have been raised. This is due to the distortion that occurs in the cooling process when molding a metal material with a difference in thermal expansion coefficient from a metal material such as a mold, so far under conditions that can be absorbed by the material and the molding thickness. However, it occurs because there is almost no absorption margin in the thin-wall molding of the rare earth magnet. In addition, since it is a molding process in a magnetic field, there are many components in which the magnetic flux generated from the mold passes through the injection-molded magnet in the magnetic field orientation process, and the magnetic orientation distribution of the rotor is not obtained as a result. The surface magnetic force waveform deviates from the sine wave. For this reason, by increasing the thickness of the rare earth layer so that the magnetic flux does not penetrate, the orientation magnetic flux from the mold rotates in the magnet, and as a result, the surface magnetic flux waveform becomes close to a sine wave. As a result, the thickness of the magnet may be increased to some extent, but the weight of the magnet material increases, and the unit price of the rotor increases as described above. Therefore, the surface magnetic flux waveform becomes a sine wave while thinning the rare earth layer. A technique is required, and for this reason, it has been proposed that the magnet portion has two layers, a rare earth magnet is disposed on the surface side, and a ferrite is formed on the rotor core side (see, for example, Patent Document 1 and Patent Document 2).
JP-A-2005-64448 JP 2005-151757 A

  When using a rare earth bonded magnet as a permanent magnet material for a rotor, it is possible to reduce the effective magnet volume because it has higher magnetic properties than a ferrite bonded magnet from the viewpoint of performance, from an economical viewpoint Considering the fact that reduction of magnet cost is required and considering the above, the thickness of the rare earth magnet used in the rotor is designed to be thin.

  From this, it is clear that just replacing the ferrite magnet which is the current material with a rare earth magnet as it is and making it thin will significantly increase the material cost, and there are problems such as reduction in strength of the magnet and cracking in production, The solution of the above problems has been achieved by making the magnetic material into two layers. However, in the present invention, the arrangement of the magnet material is improved in order to solve the above-mentioned problems of the prior art, and the rare earth magnet in a state in which the high surface magnetic flux density characteristics and the waveform of the magnetic flux density on the magnet surface are controlled. It is an object of the present invention to provide a polar anisotropic composite bonded magnet having locally disposed portions.

In order to solve the above problems, the rare earth bonded magnet composite of the present invention has a polar orientation, and a rare earth magnet is selectively disposed only on the magnetic pole portion, and the magnetic pole corresponding portion after surface multipolar magnetization is made of ferrite. It is characterized by being a structure composed of rare earth magnets having high magnetic properties. The basic configuration is different from that in which two types of ring-shaped magnets are stacked as in the disclosed example, and the rare earth magnet portion is not cracked because the rare earth magnet portion is not formed over the entire circumference.

  When molding, after placing the rare earth magnet at a desired position in the mold, the ferrite magnet is poured into the mold, and a method of forming a composite magnet body or first forming a ferrite magnet body, Although a method such as two-stage molding in which a rare earth magnet portion is formed by a mold can be selected, the performance of the composite magnet after molding is not affected by any method.

  The magnet of the present invention has a structure in which a rare earth magnet is embedded in a magnetic pole forming portion of a conventional polar-oriented ferrite magnet. When viewed from the surface having the magnetic poles, the ferrite material and the rare earth magnet material are alternately arranged, and the rare earth magnet portions are discontinuously arranged. This is composed of rare earth magnets that are formed in a separate process in a part of the ferrite magnet formed by injection molding a compound made of a kneaded material composed of ferrite magnetic powder and thermoplastic resin into a magnetic field oriented mold. The composite pole-oriented bonded magnet having a high surface magnetic flux density after multipolar magnetization is obtained by using the rare earth portion as the pole-oriented portion corresponding to the pole.

  The ferrite constituting this magnet is the basis of a bonded magnet molded body having polar orientation, and is preferably an anisotropic material. The ferrite magnet constituting the bonded magnet composite of the present invention can be made of a powder selected from a ferrite powder alone or a mixed powder of a ferrite powder and a NdFeB rare earth magnet.

  The rare earth magnet material constituting the composite magnet may be isotropic or anisotropic. The constituent material is not limited to a magnet containing a rare earth ferromagnetic powder mainly composed of NdFeB, but may be a magnet containing a ferromagnetic powder such as SmFeN or SmCo, and may be composed of at least one kind of powder. .

  The binder of the ferrite bond magnet as the base is preferably polyamide, and PPS may be used particularly when heat resistance and chemical resistance are required. When the rare earth magnet portion is also a bonded magnet, it is desirable to use the same binder in consideration of adhesion. However, if there is no problem in the molding process of the rare earth layer and the subsequent processes, there is no need to stick to this.

  The magnetic field orientation can be formed into a multi-polar ring magnet by using polar anisotropic molding with a magnetic field by a permanent magnet embedded in the mold, and the magnetic force waveform on the magnet surface when the rotor is formed with this magnet. Since a product close to a sine wave is easily produced, there are particularly advantageous effects such as motor vibration and noise reduction and efficiency improvement.

  In the present invention, the thickness of the ferrite magnet is not particularly limited, but it is desirable to consider so as to reduce the leakage of magnetic flux to the rotor core and to suppress the disturbance of the surface magnetic flux waveform during magnetization after the rotor is formed. The thickness of the rare earth layer is not particularly limited, but the rare earth layer thickness is selected in consideration of the required surface magnetic flux density and balance of material costs.

  As described above, the ferrite magnet part is formed by injection molding as described above, and a rare earth magnet may be placed in this molding die so as to be integrated with the ferrite magnet. You may shape | mold in the metal mold | die for shaping | molding. Further, by adopting a two-color molding method, the ferrite magnet and the rare earth magnet may be continuously molded in the same mold.

Since the composite bonded magnet of the present invention is a pole-oriented surface multi-pole magnet, the magnetic field applied at the time of molding can be a method in which a magnetic field is generated by passing a current through a coil installed in the mold. It is desirable to use an extremely anisotropic mold in which a permanent magnet is embedded. This is particularly effective when both ferrite magnets and rare earth magnets are formed by injection molding. This is effective for forming a magnetic pole in advance by the orientation magnetic field on the surface of the ferrite magnet formed in the process before molding the rare earth magnet, and functioning as a part of the orientation magnet in the rare earth magnet molding in the next process. .

  Hereinafter, although the procedure of the Example of this invention is demonstrated in detail, within the meaning of this invention, it is not limited to a following example.

  First, a ferrite magnet is formed by injection molding. Specifically, pellets formed from a compound obtained by kneading ferrite-based magnet powder with nylon-based resin are charged into an injection machine. It is important that the temperature conditions at the time of molding are such that the material of the ferrite magnet 2 flows and the permanent magnet 3 for magnetic field orientation does not demagnetize, the mold temperature of 40 to 150 ° C., the injection temperature of 200 to 290 ° C. And forming a ferrite polar anisotropic magnet by performing injection molding while applying a magnetic field to an octupole anisotropic mold (outer diameter 50 mm × inner diameter 30 mm) under the conditions of injection pressure of 800-1500 kg / cm 2. .

  Next, a rare earth magnet is similarly formed by injection molding. Specifically, pellets formed from a compound obtained by kneading NdFeB-based magnetic powder, which is a permanent magnet material containing rare earth, with a nylon-based resin in the same manner as described above are charged into an injection machine. Next, the ferrite magnet is placed in a mold, a magnetic field is applied within the range of the above-described conditions, and an 8-pole anisotropic mold (outer diameter 50 mm × inner diameter 30 mm) is injection-molded. Form. In this way, the composite bonded magnet molded body shown in FIG.

  As a comparative example, as a result of measuring the surface magnetic flux density of a magnet obtained by forming a ferrite polar anisotropic magnet alone with the 8-pole anisotropic mold, the maximum value was 1700 G. As a result of measuring the surface magnetic flux density in the same manner as shown in FIG. 1 by forming an NdFeB-based magnet into the magnetic pole portion so that the magnetic pole portion has a substantially concave shape, the magnetic flux portion increased to a maximum value of 2500G. The magnetic property of the rare earth magnet alone is (BH) max: 8.8 MGOe. The embedding depth of the rare earth magnet was 2 mm. The surface magnetic flux waveform was close to a sine wave. For comparison, a rare earth magnet with a thickness of 2 mm was formed on the outer periphery, and a ring-shaped all-round type was also formed, but the maximum magnetic flux density was about 2300 G. In the configuration of FIG. 1, since the rare earth magnets are discontinuously arranged, the volume occupied by the rare earth magnet can be relatively reduced.

  By making the rare earth magnet discontinuous, the slope of the surface magnetic flux waveform near the origin is smaller than that of the conventional type in which ring magnets are laminated. As a result, the embedded composite polar anisotropic magnet according to the present invention can reduce the cogging torque. By changing the area occupied by the rare earth magnet and the embedding depth when viewed from the surface, the surface magnetic flux density waveform can be adjusted in various forms according to the motor, and the efficiency of the motor can be improved.

As described above, based on the conventional technique, a rare earth bonded magnet body is previously installed in a mold, and then a ferrite magnet is formed integrally by injection molding to form a desired composite bonded magnet. A B-type ring-shaped mold is used as the mold. As a first step, an isotropic NdFeB rare earth bonded magnet block preheated in the range of 50 to 100 ° C. is disposed along the outer periphery of the mold cavity so as to be in a polar orientation position. Set. The magnetic properties of the rare earth bonded magnet block were the same as those in Example 1. Next, a ferrite magnet is formed by injection molding in the closed mold under the conditions of Example 1. Thereafter, the composite magnet integrated with the rare earth magnet was obtained by cooling in the mold.

  As a result of magnetizing this composite magnet and measuring the surface magnetic flux density using a gauss meter, the maximum magnetic flux density was 2550G. Further, the surface magnetic flux waveform is close to a sine wave, and it is possible to obtain the same characteristics as those formed under the conditions of Example 1.

  Since the ferrite / rare earth composite magnet of the present invention provides a high surface magnetic flux density, a motor formed using a rotor using the same contributes to energy saving because it achieves higher efficiency than the conventional type.

  In addition, while maintaining the thermal durability similar to that of a ferrite, it is possible to reduce the size, weight, output, and efficiency of a motor equipped with this magnet.

  In addition to the rotor, the present invention can be applied to a bonded magnet application product used for an encoder, a sensor, or the like that magnetizes a multipole magnet.

Schematic of ferrite / rare earth composite bonded magnet of the present invention a) Illustration showing the magnetization direction of a radial magnet, b) Illustration showing the magnetization direction of a pole-oriented magnet

Explanation of symbols

11 Ferrite Magnet Part 12 Rare Earth Magnet Part 21 Radial Oriented Magnet Part 22 Polar Oriented Magnet Part

Claims (4)

A polar anisotropic composite bonded magnet molded body having a plurality of magnetic poles on the surface, the bonded magnet molded body is mainly composed of a ferrite resin composition, and rare earth magnets are arranged on a plurality of magnetic pole portions on the surface. A composite bonded magnet molded body characterized by that. 2. The composite bonded magnet molded body according to claim 1, wherein the rare earth magnet of the magnetic pole portion is made of at least one of an NdFeB alloy, an SmFeN alloy, and an SmCo alloy. The ferrite resin composition is a resin composition formed from a powder obtained by mixing at least one alloy powder selected from the group consisting of an NdFeB alloy, an SmFeN alloy powder and an SmCo alloy, and a ferrite powder. The composite bonded magnet molded body according to claim 1. The composite bonded magnet molded body according to claim 1, wherein a boundary surface between the rare earth magnet portion and the ferrite magnet portion has a substantially arc shape.

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