JPH07153640A - Method and device for manufacturing permanent magnet - Google Patents

Abstract

PURPOSE:To provide a permanent magnet excellent in characteristics by a method wherein supersonic vibrations are effectively applied to alloy powder filled high in density into a cavity in an in-magnetic field compression molding process. CONSTITUTION:Alloy powder 7 is filled into a cavity 6 partitioned with a horn 3 joined to a cone 2 bonded to a vibrator 1, a die 4, and an upper punch 5, and a magnetic field is generated in the die 4 by a magnetic field generating means 8 to orientate alloy powder 7 when the alloy powder is compression- molded by the cone 2 as a lower punch, the horn 3, and the upper punch 6. The assembly composed of the cone 2 and the horn 3 is so formed in shape as a whole as to resonate with the resonant frequencies of the vibrator 1 and so set integral times as long as half the wavelength of vibrations generated by the vibrator 1. In result, a vibration A generated by the vibrator 1 has a maximum amplitude at the contacting surface of the horn 3 with a permanent magnet alloy powder 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a permanent magnet by compression-molding a permanent magnet alloy powder in a magnetic field, and in particular, to a vibration of the permanent magnet alloy powder filled in a mold during the compression molding process. The present invention relates to a method for manufacturing a permanent magnet to be added.

[0002]

2. Description of the Related Art Compression molding in a magnetic field in manufacturing a permanent magnet is roughly classified into a vertical magnetic field molding method and a parallel magnetic field molding method. By the vertical magnetic field molding method, a molded product having a high orientation can be obtained, but it is difficult to obtain a molded product having a complicated shape.
On the other hand, according to the parallel magnetic field molding method, molded bodies having various shapes can be easily obtained although the orientation is inferior. In particular, a small thin magnet having magnetization in the thickness direction is manufactured by a parallel magnetic field molding method in most cases. In recent years, the demand for small and thin magnets has been increasing, and improvements in their characteristics are strongly desired.

By the way, in the conventional parallel magnetic field molding method, if the alloy powder is naturally oriented and then compression-formed in the orientation direction while orienting the alloy powder in the magnetic field, the chains of the powder particles arranged in the magnetic field direction are bent and the orientation is disturbed. . Therefore, in order to solve such a problem, it is necessary to reduce the amount of compression in compression molding, and for that purpose, it is desirable that the alloy powder is already densely packed at the time of magnetic field orientation. However, if the alloy powder is already densely packed at the time of magnetic field orientation as described above, the high-density packing increases friction between particles, so that the powder particles cannot rotate sufficiently in the magnetic field direction. After all, there arises a problem that the orientation is not sufficiently improved. Therefore, a method of adding a lubricant in order to reduce friction between powder particles is widely used. However, this method has a problem in that the strength of the molded body after compression molding is lowered, and hence subsequent handling becomes difficult. Furthermore, in the conventional parallel magnetic field molding method, a compact having a locally dense and dense structure can be obtained because compression molding is performed without eliminating the non-uniformity of the density when filling the alloy powder. There is a problem that cracks and cracks easily occur and the sintered body is deformed after sintering. Therefore, in order to reduce the friction of the powder particles molded in the magnetic field and to make the density of the obtained molded product uniform, a slight vibration is applied to the filling powder through the molding die during the molding in the magnetic field, and Have been proposed (Japanese Patent Laid-Open No. 56-873).
04, JP-A-60-54418). It is considered that these methods are effective not only for orienting the densely packed powder particles, but also for making the density distribution of the compact uniform.

[0005]

However, the above-mentioned Japanese Patent Laid-Open No.
The magnetic field molding method disclosed in JP-A-6-87304 and JP-A-60-54418 has the following problems. The method disclosed in JP-A-56-87304 is a method in which a punch and a die are vertically arranged on a vibration transmission plate and one of the transmission plates is vibrated by an ultrasonic vibrator. The method disclosed in Japanese Laid-Open Patent Publication No. 54418 is a method of attaching an ultrasonic transducer to the side surface of the die. However, these methods do not have a structure that effectively imparts ultrasonic vibration to the alloy powder.
According to the method disclosed in Japanese Laid-Open Patent Publication No. 87304, the ultrasonic wave emitted from the vibrator hardly propagates through the vibration transmission plate thinner than the diameter of the vibrator, and the punch arranged perpendicularly to the vibration transmission plate is further improved. There is a problem that it does not propagate. Further, in the case of the method disclosed in Japanese Patent Laid-Open No. 60-54418, even if the vibrator is attached alone to the side surface of the die, it is not possible to effectively vibrate the powder. This is not suitable because vibration is applied from the side of the molded body.

The present invention has been made in view of the above problems in the prior art, and by effectively applying ultrasonic vibration to the densely packed alloy powder, the powder particles are vibrated to cause friction between the particles. It is possible to obtain a permanent magnet with better characteristics than the conventional parallel magnetic field forming method in the range of normal applied magnetic field strength, and to make the density distribution of the formed body uniform while reducing the magnetic field. The purpose is to provide a method.

[0007]

[Means for Solving the Problems] The inventors of the present invention have conducted various studies to achieve the objects of the present invention, and in order to effectively apply ultrasonic vibration to a densely packed alloy powder, a vibrator and a metal are used. The vibration system including the entire mold must be in resonance,
Therefore, the present invention has been created by considering the wave of the ultrasonic wave, the shape of the vibrator, the shape of the transmission portion between the vibrator and the powder, and the like. That is, the method for producing a permanent magnet of the present invention is a method for producing a permanent magnet in which a permanent magnet alloy powder is oriented in a magnetic field for compression molding, and a vibrator is provided in at least one of an upper punch and a lower punch in a molding die. It is characterized by being attached and performing compression molding in a magnetic field while applying ultrasonic waves to the permanent magnet alloy powder. Further, the apparatus for producing a permanent magnet of the present invention comprises a molding die for filling the permanent magnet alloy powder, a magnetic field generating means for generating a magnetic field in the molding die, and a permanent magnet alloy oriented by the magnetic field generated by the magnetic field generating means. In a permanent magnet manufacturing apparatus having an upper punch and a lower punch for compressing and molding powder in a molding die, a vibrator is attached to at least one of the upper punch and the lower punch, and ultrasonic waves are applied to the permanent magnet alloy powder. It is characterized by performing compression molding in a magnetic field while applying. The shape of the punch to which the vibrator is attached is preferably a shape having the maximum amplitude at the contact surface with the permanent magnet alloy powder. This is because the maximum vibration energy can be applied to the filling powder to efficiently reduce the friction of the filling powder and make the filling density uniform. Further, the cross-sectional area of the punch to which the vibrator is attached changes continuously or / and discontinuously,
In addition, it is preferable to use a horn that resonates at the frequency of the vibrator used. This is because the ultrasonic waves generated by the vibrator are amplified and transmitted, and the maximum vibration energy is applied to the filling powder to efficiently reduce the friction of the filling powder and make the filling density uniform. . The application direction of the ultrasonic vibration is preferably parallel to the application direction of the shaping magnetic field. This is because in particular, when a thin-walled molded body that is magnetically oriented in the thickness direction is obtained, friction can be efficiently reduced and the packing density can be made uniform, and the orientation efficiency can be improved. Further, by fixing the punch to which the vibrator is attached to a support base through a mounting tool, it is possible to prevent the reaction force of the punch forming pressure from being applied to the vibrator.

A punch to which the above-mentioned vibrator is attached is composed of a cone and a horn, and these expand the vibration amplitude (several μm) of the vibrator to generate a large vibration amplitude (15-40 μm) at the contact surface in contact with the filling powder. In order to obtain, the cross-sectional area is changed continuously or discontinuously, and the entire length of the cone and horn is set as an integer multiple of a half wavelength of the vibration wavelength generated by the used oscillator. A shape that resonates at the resonance frequency is preferable. Further, as shown in FIG. 1, it is preferable that the fixture 3 is provided at the position of the vibration node, and the joint portion between the vibrator 1 and the cone 2 and the cone 2 and the horn 4 is provided at the position of the antinode of the vibration. As a result, the punch is firmly supported by the mounting portion 3, while the vibrator 1
This is because the energy loss in the transmission of vibration in the cone 2, the cone 2, and the joint portion of the cone 2 and the horn 4 becomes small.

[0009]

According to the present invention, the vibration can be applied to the filling powder in parallel with the magnetic field direction by directly transmitting the vibration to the alloy powder to be molded through the upper punch or the lower punch in the parallel magnetic field molding. Further, the vibration can be effectively transmitted to the filling powder in the mold by bringing the entire vibration system including the punch including the cone and the horn and the vibrator into the resonance state.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the method for manufacturing a permanent magnet and the apparatus therefor according to the present invention will be described below with reference to the drawings. FIG. 1 shows an overall schematic view of a permanent magnet manufacturing apparatus of the present invention, and FIGS. 2 and 3 show partially enlarged views thereof. As shown in FIGS. 1, 2 and 3, a cone 2 is joined to a vibrator 1 having a known structure for generating ultrasonic waves, and a horn 3 is joined to the cone 2. Further, the horn 3 forms a cavity 6 together with the die 4 as the molding die and the upper punch 5, and the alloy powder 7 is filled and filled in the cavity 6 to form the cone 2 and the horn 3 as the lower punch and the upper punch 6. By compression molding. At that time, a magnetic field is generated in the die 6 by the action of the magnetic field generating means 8 provided to generate a magnetic field in the die 6, whereby the alloy powder is oriented in a predetermined direction. The entire shape of the cone 2 and the horn 3 is a shape that resonates at the resonance frequency of the vibrator 1. Specifically, as shown in the drawing, the horn 3 has a maximum diameter at the joint portion with the cone 2, and has a minimum diameter at the other end that forms the cavity 6 together with the die 4 and the upper punch 5, and continuously or / And has a discontinuously changing shape. Further, the total length of the cone 2 and the horn 3 is set to an integral multiple of a half wavelength of the vibration wavelength generated by the vibrator 1. As a result, as shown in the figure, the vibration A generated in the vibrator 1 has the maximum amplitude at the contact surface of the horn 3 with the permanent magnet alloy powder 7. The punch, that is, the cone 2 and the cone 2 of the horn 3 to which the vibrator is attached are fixed to a support base 10 via an attachment 9. Therefore, the alloy powder 7 is formed by the lower punch including the horn 3 and the cone 2.
The reaction force of the molding pressure at the time of compression molding is received by the support base 10 from the cone 2 fixed to the support base 10 via the fixture 9, and the reaction force of the molding pressure is received by the vibrator 1. There is no possibility that the vibrator 1 will be damaged due to the above.
In the above, the fixture 9 is located at the node of the vibration generated and propagated by the vibrator 1, and the joint between the vibrator 1 and the cone 2 and the cone 2 and the horn 3 is located at the antinode of the vibration. The position of the fixture 9, the lengths of the cone 2 and the horn 3, and the like are set. As a result, the fixture 9 is not affected by the vibration of the vibrator 1, while the vibrator 1 is not formed at the joint between the vibrator 1 and the cone 2 and the cone 2 and the horn 3.
The vibration generated by is efficiently transmitted.

The method for producing a permanent magnet of the present invention was carried out using the above-described apparatus for producing a permanent magnet of the present invention. The composition of the alloy powder used is Nd: 29.4, B: 1.02, Dy:
1.25, Nb: 0.35, Ga; 0.075, Pr: 0.0.
45 (wt%), Fe: bal., The applied magnetic field is 17 kOe, and the molding pressure is 0.8 ton / cm ² . At the same time as the start of compression, ultrasonic waves with a frequency of 28 kHz were applied. After sintering this compact in a vacuum at 1,100 ° C. for 2 hours, the first heat treatment is performed in an Ar atmosphere at 900 ° C. × 2.
After being cooled to room temperature for 2 hours, a second heat treatment was performed at 620 ° C. for 1 hour in an Ar atmosphere.

For comparison, the same alloy powder was prepared by the same method without applying ultrasonic waves. The results are shown in Table 1.
Shown in.

[Table 1] As shown in Table 1, the permanent magnets obtained in the examples of the present invention have excellent magnetic flux density and maximum energy product as compared with the permanent magnets of the comparative example.

[0014]

As described above, according to the method and apparatus for manufacturing a permanent magnet of the present invention, a vibrator is attached to at least one of the upper punch and the lower punch to apply ultrasonic waves to the permanent magnet alloy powder. Since compression molding is performed in a magnetic field while applying, for example, when manufacturing a thin magnet having magnetization in the thickness direction by parallel magnetic field molding, ultrasonic vibration can be applied in the compression direction through the upper punch or the lower punch. In addition, the vibration of the vibrator can be effectively applied to the filling powder, the effect of reducing friction due to the vibration can be more remarkably brought out, and the uniformity of the orientation and density of the molded body can be improved.

[Brief description of drawings]

FIG. 1 is a schematic view of a permanent magnet manufacturing apparatus according to an embodiment of the present invention.

FIG. 2 is a partially enlarged view of FIG.

FIG. 3 is a partially enlarged view of FIG.

[Explanation of symbols]

 1 Vibrator 2 Cone 3 Horn 4 Die 5 Upper Punch 7 Permanent Magnet Alloy Powder 8 Magnetic Field Generating Means 9 Mounting Tool 10 Support

Claims (11)

[Claims] 1. A method for producing a permanent magnet in which permanent magnet alloy powder is oriented in a magnetic field for compression molding, wherein a vibrator is attached to at least one of an upper punch and a lower punch in a molding die to form a permanent magnet alloy. A method for producing a permanent magnet, which comprises subjecting powder to compression molding in a magnetic field while applying ultrasonic waves. 2. The method for producing a permanent magnet according to claim 1, wherein the shape of the punch has a maximum amplitude at the contact surface with the permanent magnet alloy powder. 3. The method for producing a permanent magnet according to claim 1, wherein a horn whose cross-sectional area changes continuously or / and discontinuously and which resonates at a frequency of a vibrator used is used as the punch. 4. The method of manufacturing a permanent magnet according to claim 1, 2 or 3, wherein the application direction of the ultrasonic vibration is parallel to the application direction of the shaping magnetic field. 5. A molding die for filling the permanent magnet alloy powder, a magnetic field generating means for generating a magnetic field in the molding die, and a permanent magnet alloy powder oriented by the magnetic field generated by the magnetic field generating means in the molding die. In a manufacturing apparatus for a permanent magnet having an upper punch and a lower punch, which are compression-molded by a method described above, a vibrator is attached to at least one of the upper punch and the lower punch to compress the permanent magnet alloy powder in a magnetic field while applying ultrasonic waves. An apparatus for manufacturing a permanent magnet, characterized by being molded. 6. The permanent magnet manufacturing apparatus according to claim 5, wherein the punch to which the vibrator is attached is composed of a cone and a horn, and the shape of the entire cone and the horn resonates at the resonance frequency of the vibrator used. 7. The punch to which the oscillator is attached comprises a cone and a horn, and the entire length of the cone and the horn is an integral multiple of a half wavelength of the oscillation wavelength generated by the oscillator. The manufacturing apparatus for the permanent magnet described. 8. The permanent magnet manufacturing apparatus according to claim 5, wherein the punch has a shape having a maximum amplitude at a contact surface with the permanent magnet alloy powder. 9. The permanent according to claim 5, wherein the punch is a horn whose cross-sectional area changes continuously or / and discontinuously and which resonates at the frequency of the vibrator. Magnet manufacturing equipment. 10. The punch according to claim 5, wherein the punch to which the vibrator is attached is fixed to a support base via a mounting tool so that a reaction force of a punch forming pressure is not applied to the vibrator. An apparatus for manufacturing a permanent magnet described in 1. 11. The mounting member is provided at a node of vibration generated and propagated by the vibrator, and the joint between the vibrator and the cone and the cone and the horn is provided at an antinode position of the vibration. 11. The permanent magnet manufacturing apparatus according to claim 9.