JPH01114009A - Manufacturing method of bonded magnet - Google Patents

Abstract

PURPOSE:Tc enable a bond magnet which has a high density and good characteristics to be effectively produced, by employing a series of processes in which after the mixture of permanent magnet powder material and resin is pelletized, the pelletized powder is filled into a metallic mold and molded with being pressurized by applying an a.c. magnetic field which has the gradient in the direction of the depth of the metallic mold. CONSTITUTION:The upper part of a ring-shaped molding space 50 is filled with the pelletized powder which is produced by pelletizing the mixture of permanent magnet powder material and resin. The magnetic flux caused by the current in coils 22a and 22b is collected to an upper punch holder 16 through yokes 18a, 18b, 20a and 20b, and then passes through rods 12 and 32, thereafter flowing a die 10. When this a.c. magnetic field is applied to the pelletized powder in the die 10, the flux density in the space 50 is more large than that between the rods 12 and 32. Therefore, the pelletized powder is magnetically attracted into the space 50 so that it is perfectly filled in the die 10 even if the die 10 has any narrow gap. Subsequently, the pelletized powder is molded with being pressurized. Accordingly, the magnet which has a high density and good characteristics can be effectively produced.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for manufacturing a bonded magnet in which stone powder is permanently bonded using a resin. The present invention relates to a method for manufacturing a bonded magnet, which is uniformly filled into a mold and compression-molded in a short time.

[Prior Art] A bonded magnet in which permanent magnet powder is bonded with a polymer resin is conventionally known. This type of bonded magnet is manufactured by mixing permanent magnet powder and a polymer resin such as an epoxy resin, and molding the mixture into a predetermined shape. For molding,
In order to develop good magnetic properties, a compression molding method is usually employed in which the mixture is filled into a mold and compressed with a press.

In this molding, the granulated powder is filled into the mold by allowing the powder to fall naturally from the mold opening by a bottomless powder supply mechanism that slides on the top surface of the die, and then by sliding the powder supply mechanism. A common method is to fill a certain amount of powder into a mold using a cutting method.

However, if the area or width of the mold opening is quite small, it is very difficult to supply the powder by such natural falling, and it is unavoidable to use a push rod or the like to force the powder from above to force the powder to fall and fill. method is adopted.

[Problems to be solved by the invention] When the mold opening area is small or the width of the opening is narrow,
In the method of forcibly filling the powder using a push rod, etc. from above, when the powder is filled into the mold, there are parts where the shape of the powder differs from the previous shape, making it difficult to uniformly and quantitatively fill the mold, resulting in poor density distribution. There is a problem that arises. Furthermore, since the operation is troublesome, it takes a very long time to fill the powder, which has the disadvantage of poor manufacturing efficiency.

Particularly in the case where an anisotropic magnet is manufactured by applying an orienting magnetic field during molding, it becomes difficult to orient by the magnetic field in extremely dense parts, which may result in a decrease in properties.

The purpose of the present invention is to eliminate the drawbacks of the prior art as described above, to supply a fixed amount of granulated powder, which is a mixture of permanent magnet powder and resin, uniformly into a mold in a very short time. An object of the present invention is to provide a method for efficiently manufacturing bonded magnets with stable quality and excellent magnetic properties.

[Means for Solving the Problems] The present invention, which can achieve the above-mentioned objects, involves granulating a mixture of permanent magnet powder and resin, and placing the granulated powder deep in a mold. This is a method for manufacturing bonded magnets in which a mold is filled and compression molded using an alternating current magnetic field with a magnetic field gradient in the horizontal direction.

The granulation process can be easily carried out by crushing the mixture, for example by passing it through a mesh or by crushing it with a blade rotating at high speed.

The permanent magnet powder used can be rare earth, ferrite, alnico, or neodymium-iron-boron, and the resin can be epoxy, phenol, etc. It is.

There are no particular restrictions on the magnetic field used when filling the granulated powder into the mold, as long as it changes depending on the location so that it becomes stronger in the direction of fall. It doesn't matter how you put it.

The present invention can be applied to cases in which an orienting magnetic field is applied during compression molding to create anisotropy, and can also be applied to isotropic magnets in which no magnetic field is applied during molding.

[Operation] Permanent magnetic powder with a certain coercive force, like Zhou Nero, responds sensitively to magnetic fields. These permanent magnet powders naturally have the property of being attracted in the direction of a strong magnetic field.

The presence of a magnetic field near the mold whose strength varies depending on location provides a moving force to the granulated powder.

If this is an alternating current magnetic field with a magnetic field gradient in the depth direction of the mold, the magnetic field will become progressively stronger as the granulated powder enters the mold, and it will be filled. This filling process is performed using the force of natural falling and the force of a magnetic field, so even if the mold opening area is small or the width of the opening is extremely narrow, it can be done smoothly within a short time. Unlike conventional forced filling using a push rod, the granulated powder is filled almost uniformly without breaking.

Thereafter, by compression molding using the mold, an anisotropic magnet can be produced if a special magnetic field is applied, and an isotropic magnet can be produced if a magnetic field is not applied. Since the mold is filled uniformly and the granulated powder is not destroyed during filling, permanent magnets with stable and high characteristics can be manufactured. Furthermore, since the granulated powder is quickly filled, manufacturing efficiency is also significantly improved.

[Example] Samarium-cobalt (S m
z Co +t) alloy with an average grain size of 3 using a shed mill.
The powder was crushed into micrometers, compacted in a magnetic field, sintered and aged, and used as a raw material.

This raw material sintered body was crushed with a show crusher and sieved to obtain average particle sizes of 100 μm and 50 μm.

Three types of powders of 20 μm were obtained and mixed at 50; 25:2.
A permanent magnet powder was obtained by mixing at a ratio of 5:5.

This permanent magnet powder was treated with a coupling agent and then mixed with an epoxy resin. This mixture is granulated by crushing it with a crushing type granulator, and the average particle size is 300 to 40.
Granulated powder of 0 μm was obtained.

A radially anisotropic ring-shaped bonded magnet was manufactured using the granulated powder.

Figure 1 shows the structure of the mold and magnetic circuit used here. An upper rod 12 is located at the upper center of the magnetic die 10, and an upper punch 14 and an upper punch support 16 are provided to surround it.

The upper rod 12 and the upper punch support 16 are made of a magnetic material, and magnetic yokes 18a, 18b and a magnetic yoke 20a are arranged to form a magnetic path between them and the die 10.
20b is provided.

The magnetic yokes 18a and 18b each have a coil 2.
2a and 22b are wound. The lower half of the die 10 has almost the same structure, including a lower rod 32, a lower punch 34, a lower punch support 36, magnetic yokes 38a, 38b, 40a, 4
0b, and coils 42a and 42b. As a result, a thin ring-shaped molding space 50 is formed in the die 10 by the lower punch 34, lower rod 32, etc., and the granulated powder is filled therein.

To fill the granulated powder, as shown in FIG. 2, the granulated powder 52 is placed on the upper part of the ring-shaped molding space 50, and
This is done by applying an alternating magnetic field at 22b, 42a, and 42b. Note that the member indicated by the reference numeral 54 is a cover for preventing scattering of granulated powder.

The magnetic flux generated by the coils 22a, 22b passes through the magnetic yokes 18a, 18b, 20a, 20b, is collected by the upper punch support 16, and is transferred to the upper rod 12 as shown by the broken line in FIG.
It also flows through the lower rod 32 to the die 10. The same goes for the lower half. When such an alternating magnetic field is applied to the granulated powder 52 piled on the die 10, the magnetic flux density in the ring-shaped molding space 50 is greater than the magnetic flux density between the upper rod 12 and the lower rod 32, and the magnetic field The granulated powder is sucked into the ring-shaped molding space 50 due to such a difference in the time when . The granulated powder 52 remaining on the die 10 also repeats complex vibrations in response to the alternating magnetic field, and is completely filled into the die within a few seconds even in a very narrow gap.

The magnetic field applied here is about 0.6 to 1 kOe, and is an alternating magnetic field at a commercial frequency.

In this way, the outer diameter is 18 mmφ, the inner diameter is 16 mmφ, and the height is 1.
Approximately 1.5 g of granulated powder could be quickly filled into a 0 mm mold.

Molding was carried out in a magnetic field of 15 kOe with a radial orientation at a pressure of 3 ton/cm'', followed by a curing treatment at 120°C for 2 hours and a pulse magnetizer at 20 to 30 kOe. 24-pole magnetization was performed.

In addition, for comparison, a radial anisotropic ring-shaped pound magnet was manufactured by filling the granulated powder into a mold using a combination of gravity fall and forced press-fitting with a push rod, and molding using the same procedure. .

Table 1 shows the measurement results of the physical properties of the obtained bonded magnet and the time required for filling it into the mold.

Table 1 As is clear from the results, the method of the present invention has a very small variation in surface magnetic flux, allowing for higher density of the product, the value of surface magnetic flux is also very large, and the total magnetic flux is 10% higher than that of the conventional product. It can be seen that the improvement is about 15%. This is because in the present invention, the shape of the granulated powder in the mold is the same as the original shape (before filling), there are no locally collapsed parts, and a uniform density distribution can be achieved, with sufficient orientation even in a predetermined magnetic field. This is so that things can be done. Further, as is clear from the filling time column, the method of the present invention completes filling in a time so short that it is not a problem compared to the prior art.

Although a preferred embodiment of the present invention has been described above in detail, the present invention is not limited to only such a configuration. The above-mentioned excellent effects of the present invention are mainly due to the magnetic properties of the material, so if it is a mixture of permanent magnet powder and resin, the samarium-cobalt based magnet may be used as the magnet powder. In addition, similar results can be obtained even if any of the resins is ferrite, alnico, neodymium-iron-boron, etc., and the resin is not only epoxy but also phenol. The shape of the molded object,
The shape can be applied not only to a ring shape but also to any other arbitrary shape. In particular, the present invention is effective when the opening area of the mold is very small, or when one side is extremely narrow (i.e., thin-walled structure) as in the above embodiment. It is optional whether or not to apply an orientation magnetic field during final molding, and therefore it is also applicable to the production of isotropic bonded magnets. The magnetic field when filling the granulated powder changes depending on the location, and any method of application such as a vertical magnetic field, transverse magnetic field, or radial magnetic field can be applied as long as the magnetic field changes to become stronger as the falling direction increases. It may be parallel or perpendicular to the falling direction of the granulated powder.

[Effects of the Invention] The present invention granulates a mixture of permanent magnet powder and resin as described above, and then fills the mixture into a mold with an alternating current magnetic field having a magnetic field gradient in the depth direction of the mold and compression molds the mixture. Because of this method, the time required to fill the granulated powder into the mold can be significantly shortened compared to conventional techniques, and it can be filled quickly even when the mold opening area is small or extremely narrow. This has an excellent effect in that the production efficiency of magnets can be greatly increased.

In addition, with the present invention, the granulated powder can be uniformly filled into the mold without changing the original shape, and can be filled in a fixed quantity with good reproducibility.
A high degree of orientation can be expected even in a given magnetic field, a more uniform density distribution is realized, and uniform magnetic flux is generated, which has the effect of making it possible to manufacture bonded magnets with higher density and higher characteristics.

[Brief explanation of the drawing]

FIG. 1 is an overall structural diagram of a mold and a magnetic circuit for manufacturing a radially anisotropic ring-shaped bonded magnet used in the method of the present invention;
FIG. 2 is an enlarged explanatory diagram showing the granulated powder filling state and magnetic flux at the portion H surrounded by the dashed line in FIG. 1. FIG. 10...Dice, 12...Upper rond, 14...Upper punch, 22a, 2jb, 42a, 42b-coil, 3
2... Lower rod, 34... Lower punch, 52... Granulated powder, 54... Scattering prevention cover. Patent applicant: Fuji Electrochemical Co., Ltd. Agent: Minoru Shigeru (Figure 1, 1')

Claims (1)

[Claims] 1. A mixture of permanent magnet powder and resin is subjected to granulation treatment,
A method for manufacturing a bonded magnet, which comprises filling the granulated powder into a mold using an alternating current magnetic field having a magnetic field gradient in the depth direction of the mold and compression molding the powder.