JPH027506A - Method of filling space with permanent magnet powder - Google Patents

Abstract

PURPOSE:To fill the molding space of a die with a certain quantity of permanent magnet powder piled above the opening of the molding space uniformly in a very short time and manufacture a permanent magnet having excellent magnetic characteristics by a method wherein a solenoid coil is provided near the opening and an AC current is applied to it and the permanent magnet powder is magnetically attracted into the space to fill it. CONSTITUTION:A solenoid coil 20 and a magnetic pole 22 are provided near the opening of the molding space 18 of a die and permanent magnet powder 24 is piled above the molding space 18. If an AC current is applied to the solenoid coil 20, AC magnetic lines of force are induced as shown by broken lines and an AC magnetic field is produced in the permanent magnet powder 24, the molding space 18 and so forth. The permanent magnet powder piled above the molding space 18 is magnetically attracted into the space 18 by the AC magnetic field and, while the permanent magnet powder repeats the complex vibration caused by the reaction with the AC magnetic field, even a very narrow gap is filled with the powder in a short time. Therefore, the molding space can be filled with the permanent magnet powder quickly and a permanent magnet can be molded very efficiently.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a solenoid coil near the opening of the molding space of a mold, and applies an alternating magnetic field to uniformly spread permanent magnet powder in a short time. The present invention relates to a method of filling a molding space.

[Prior art] In order to develop good magnetic properties, the molding of permanent magnet powder usually involves filling the molding space of a mold with permanent magnet powder and compression molding it with a press molding machine. ing.

In compression molding, permanent magnet powder is filled into the molding space using natural falling due to gravity. In other words, a bottomless powder supply mechanism that slides on the top surface of the die that makes up the mold fills the molding space by letting it fall naturally from the opening, and the powder supply mechanism is slid to remove excess powder. A common method is to fill the molding space of a mold with a certain amount of powder using a sliding method.

If the opening area of the mold forming space is quite large, it can be filled using this method, but if the area or width of the opening is small, the powder supply mechanism can be simply slid along the top surface of the mold. It is difficult to fill the liquid sufficiently by simply letting the liquid flow.

For this reason, a method of filling the mold by applying slight vibrations or a method of forcibly pushing the powder by providing a forced filling feather m<pushing member) above the molding space may be adopted.

[Problems to be solved by the invention] The method of filling a mold by applying slight vibrations has the disadvantage that the filling rate changes depending on the state and shape of the powder, and that the vibrations cause the bolts of the device to be loosely tightened. There is a gap,
There were drawbacks such as not much improvement in filling efficiency and poor reproducibility of filling amount.

In addition, the method of forced filling using blades not only takes a very long time to fill, but also makes it difficult to automate powder filling in the press process, resulting in extremely poor manufacturing efficiency. Because the powder is pushed in, the shape of the filled powder differs locally from the previous shape (before filling), which makes it difficult to fill uniformly and quantitatively, leading to variations in weight and uneven density distribution during molding. There were drawbacks such as:

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the conventional technology, and even if the opening area of the molding space of the mold is small or the width of the opening is narrow, the permanent magnet powder can be rolled evenly and uniformly in a short time. It is an object of the present invention to provide a method for filling permanent magnet powder which can be filled into the molding space, thereby producing a permanent magnet with good magnetic properties, and which can be immediately applied to an existing press molding machine.

[Means for Solving the Problems] The present invention, which can achieve the above objects, includes a solenoid coil in the vicinity of the opening of the molding space of the mold, the central axis direction of which substantially coincides with the depth direction of the molding space. This is a method for filling permanent magnet powder, characterized in that the permanent magnet powder above the opening is magnetically attracted and filled into the molding space by supplying alternating current.

Here, the solenoid coil may be of an air-core type, but more preferably has a structure having a magnetic ball inside.
Alternatively, any permanent magnet powder such as neodymium-iron-poron powder can be used, and powder of any particle size or state can also be used. Therefore, it may be a powder for sintered magnets or a powder for bonded magnets kneaded with resin.

[Operation] As is well known, permanent magnet powder having a certain coercive force reacts sensitively to magnetic fields. These permanent magnet powders naturally have the property of being attracted in the direction of a strong magnetic field, so a solenoid is installed near the opening of the molding space of the mold in an orientation such that its central axis almost coincides with the depth direction of the molding space. When the coil is installed and an alternating current is supplied, an alternating magnetic field is applied, which gives a moving force to the permanent magnet powder. This moving force acts in a direction to attract the permanent magnet powder into the molding space, and the permanent magnet powder is sequentially filled into the space. This filling is performed using a magnetic attraction force that is much larger than the force generated by natural painting, so even if the opening area of the molding space of the mold is small or the width of the opening is extremely narrow, it can be filled in a short time. is carried out smoothly. Moreover, unlike conventional forced filling using blades or the like, the permanent magnet powder is filled almost uniformly with almost no breakage.

[Example] FIG. 1 is an explanatory diagram showing an example of an apparatus suitable for carrying out the method of the present invention. This shows a part of a mold for obtaining a cylindrical or ring-shaped molded body. A die 10 having a circular hole in the center, a lower rod 12 arranged with a gap in the center thereof, and the die 10 and the lower rod 12.
The cylindrical lower bunch 14 is slidable vertically within the cylindrical gap between the cylindrical lower bunch 14 and the cylindrical lower bunch 14. The cylindrical void formed by these kings constitutes the molding space 18. The molding space 18 is filled with permanent magnet powder, and a cylindrical upper punch (not shown) is inserted from above and pressurized to perform compression molding.

The mold structure of such a press molding machine is basically the same as that of the conventional case.

In the present invention, the solenoid coil 20 is arranged near the opening of the molding space 18 of the mold. The solenoid coil 20 is oriented so that its solid axis direction substantially coincides with the depth direction of the molding space 18.

Here, the solenoid coil 20 has an inner diameter slightly larger than the outer diameter of the molding space 18, and a cylindrical magnetic ball 22 having a diameter equal to or smaller than the diameter of the solenoid coil 20 is provided on the lower punch 14 in the center.

In this embodiment, among the members constituting the mold, die 1
0 and the lower rod 12 are made of magnetic material, and the lower punch 14 (also the upper punch) is made of non-magnetic material.

The filling of permanent magnet powder is carried out as shown in the figure.The solenoid coil 20 and magnetic balls 22 are installed as described above near the opening of the molding space 1B of the mold, and the permanent magnet powder is filled above the molding space 18. Add body 24. Then, alternating current is supplied to the solenoid coil 20. There is no particular restriction on the frequency of the alternating current to be used, but it may be a normal commercial frequency. By passing an alternating current through the solenoid coil 20, alternating current magnetic lines of force are generated as shown by the broken line in the figure, and the permanent magnet powder is An alternating magnetic field is formed within the molding space 24 and the molding space 18 .

Although the shape of the magnetic lines of force changes depending on the material (magnetic or non-magnetic) of the mold component, the approximate path is shown for convenience. Due to this alternating magnetic field, the permanent magnet powder 24 piled up on the upper part of the molding space 18 is magnetically attracted to the inside thereof, and repeats complex vibrations in response to the alternating magnetic field, even if the gap is very narrow. It will fill up in time.

Therefore, if necessary thereafter, excess permanent magnet powder is removed by a sliding method or the like, and compression molding is performed by lowering the upper punch and applying pressure.

As described above, in this embodiment, the magnetic ball 22 is arranged at the center of the solenoid coil 20.

When the magnetic ball 22 is provided, the molding space 18 is thereby
This is preferable because it is possible to concentrate the alternating magnetic field at , and to effectively attract the permanent magnet powder 24 into the molding space 18 even with a weak current.

However, depending on the case, an air-core solenoid coil that does not use magnetic balls may be used, or another yoke structure may be provided.

Next, an experimental example in which permanent magnet powder was filled based on the method of the present invention will be explained. Using samarium-cobalt powder with an average particle size of 110 μm or less, the outer diameter is 185 mφ and the inner diameter is 16 mm.
A cylindrical molding space with a diameter of 16 m and a height of 16 m was filled. The results are shown in Table 1. In Table 1, the conventional method is a natural fall method in which the powder is placed in a sliding filling jig and moved back and forth on a die to fall and fill into the molding space. It is.

(Left space below) Table 1 Here, method A of the present invention is a case where a magnetic ball is installed at the center of the solenoid coil, and method B of the present invention is a case of an air-core solenoid coil without a magnetic ball. It can be seen that in either case, a substantially uniform filling amount was obtained and the filling time was extremely short. In particular, if a magnetic ball is used in the center, the filling time can be further shortened compared to the case of an air-core solenoid coil.

On the other hand, in the conventional method, not only does it take a long time to fill the mold, but the molding space is so thin that the powder does not enter, resulting in a small amount of filling and large variations.

The above-mentioned remarkable effects of the present invention are mainly due to the magnetic properties of the powder, so in the case of permanent magnet powder, in addition to the samarium-cobalt magnet powder, ferrite, alnico, Alternatively, similar results can be obtained with any neodymium-iron-boron system. It is particularly effective when the shape of the molding space is a thin cylinder or a thin plate, but it can also be applied to any other shape.

Needless to say, the present invention can be applied not only to powder for sintered magnets but also to powder for bonded magnets (powder kneaded with resin).

[Effects of the Invention] As described above, the present invention provides a method in which a solenoid coil is installed in the vicinity of the opening of the molding space of a mold in a direction in which the central axis direction substantially coincides with the depth direction of the molding space, thereby applying an alternating magnetic field. Because of the method of filling permanent magnet powder configured in This method has extremely excellent effects in that the powder can be quickly filled into the molding space and the permanent magnet can be molded very efficiently.

Moreover, since the permanent magnet powder is filled by magnetic attraction rather than forced mechanically, the original shape of the powder is maintained, resulting in a uniform density distribution and a constant molded weight, resulting in characteristics We can mass-produce permanent magnets with a complete set of characteristics. Furthermore, since the present invention only requires installing a solenoid coil at the top of the mold, it can be applied to any type of existing press molding machine, regardless of the particle size or condition of the powder.
It can be used in various fields of manufacturing permanent magnets.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a molding die, a filling solenoid coil, and AC magnetic cotton used in the method of the present invention. DESCRIPTION OF SYMBOLS 10... Dice, 12... Lower rond, 14... Lower punch, 18... Molding space, 20... Solenoid coil, 22... Magnetic pole, 24... Permanent magnet powder.

Claims (5)

[Claims] 1. A solenoid coil is installed near the opening of the molding space of the mold.
Permanent magnet powder, characterized in that the central axis direction thereof is installed in a direction that substantially coincides with the depth direction of the molding space, and the permanent magnet powder above the opening is filled into the molding space by supplying an alternating current. filling method. 2. Claim 1: A magnetic pole is provided in the solenoid coil.
Filling method as described. 3. The filling method according to claim 1, wherein the solenoid coil is an air-core solenoid coil. 4. 2. The filling method according to claim 1, wherein the permanent magnet powder is powder for sintered magnets. 5. 2. The filling method according to claim 1, wherein the permanent magnet powder is powder for bonded magnets kneaded with resin.