JPH0469407B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a ring-shaped thermoplastic resin bonded rare earth radially anisotropic permanent magnet by an extrusion molding method in a magnetic field.

[Conventional technology] Conventionally, rare earth permanent magnets using thermoplastic resin as a binder have been manufactured by injection molding, and these magnets include isotropic magnets and magnets with magnetic performance added only in a specific direction. It can be roughly divided into anisotropic magnets.

In particular, cylindrical radially anisotropic permanent magnets that have magnetic anisotropy in a radial direction are widely used as rotors for small motors and the like by applying multipolar magnetization to the outer peripheral surface.

However, most cylindrical permanent magnets are short in length compared to their inner diameter, and have a wall thickness of 1 mm or more, which limits their dimensions.

Therefore, a method for manufacturing cylindrical radially anisotropic permanent magnets by extrusion molding has been invented, but none of these methods have been put to practical use. A method is disclosed in which a mixture with plastic is produced into a sheet by a calendering method, then formed into a tape, and wound in multiple layers to create a roll.

However, when manufacturing rare earth permanent magnets using thermoplastic resin, the raw material cost is much higher than that of ferrite magnet powder, so it is difficult to put into practical use processes that increase costs, such as winding multiple layers, and it is difficult to achieve a certain thickness. The problem is that cutting the material after cutting it into a sheet is inefficient, and cracks and cracks tend to occur when wrapping.If rare earth magnet particles are used, it is not possible to add magnetic anisotropy by the calendering method. It was hot.

[Problems to be Solved by the Invention] The present invention is intended to solve such problems, and its purpose is to use resin-bonded rare earth magnet powder to create a magnet with a wall thickness that is longer than the inner diameter. An object of the present invention is to provide a method for manufacturing a thin ring-shaped radially anisotropic permanent magnet.

[Means for Solving the Problems] A method for manufacturing a ring-shaped permanent magnet of the present invention includes: a method for manufacturing a ring-shaped permanent magnet having magnetic anisotropy by extrusion molding in a magnetic field, comprising: a resin-bonded rare earth magnet; This method of manufacturing a ring-shaped permanent magnet is characterized by extruding a spiral tape using powder, winding the tape around a ring-shaped mandrel, and then cutting it into rounds to a predetermined length.

[Function] The method for manufacturing a ring-shaped permanent magnet of the present invention is a method for manufacturing a ring-shaped permanent magnet having magnetic anisotropy by an extrusion molding method in a magnetic field. The magnet is formed into a tape shape using a magnetic field extrusion molding apparatus shown in FIG. 1, which will be described later, and then spirally formed into a ring-shaped permanent magnet.

Since it is made into a tape shape in the process of adding magnetic anisotropy, the magnetic field does not saturate, so a strong magnetic field can be applied and the orientation of the magnetic particles is improved. In the method of directly forming a ring to add radial anisotropy, it may not be possible to obtain an orienting magnetic field depending on the shape, but this method is particularly useful in such cases. Because it is shaped like this, it is possible to manufacture long, thin-walled radial magnets.

In addition, since it is made into a ring shape after being made into a spiral shape, it is possible to manufacture long, thin-walled radial magnets.Also, since it is made into a spiral shape and then wound around a ring-shaped mandrel, it is possible to produce thin-walled magnets. In addition, compared to the conventional method of wrapping a tape around a ring-shaped mandrel, the amount of change after curing is smaller, so there are fewer cracks and cracks. There is no need to wrap it, and it can be formed to a predetermined thickness and then wrapped, thereby reducing costs.

The rare earth magnet powder has the general formula Sm
(CO0.0627Cu0.008Fe0.22Zr0.028) 8.35 It is a magnetic powder made by grinding a 2-17-diamond intermetallic compound alloy to a particle size of 2 to 80 microns using a ball mill,
The mixing ratio of the rare earth magnet powder and the binder nylon 6, 12 is preferably 40 to 75% by volume of magnet powder, 10 to 35% by volume of nylon 6, and the remainder nylon 12 by volume.

Furthermore, the dimensions of the cooling die part of the above-mentioned magnetic field extrusion molding apparatus are important in determining the molding dimensions. thickness of 5 to 20
mm, the width is preferably 2 to 10 mm larger than the width of the gap.

Hereinafter, the present invention will be explained in detail based on examples.

[Example] Example 1 FIGS. 1A and 1B are explanatory diagrams of a magnetic field extrusion molding apparatus and a magnetic generation circuit for carrying out the manufacturing method according to the embodiment of the present invention, and FIG. 2 is an explanatory diagram of the present embodiment. FIG. 3 is a graph of the relationship between coil current and generated magnetic field strength, and FIGS. 4 and 5 are cross-sectional views of the magnet molded product in this embodiment.

In Fig. 1, 1 is a hopper, 2 is a cylinder, 3 is a heater, 4 is a screw, 5 is a tapered barrel part, 6 is a magnetic circuit, 7 and 8 are magnetic field coils, 9 is a line of magnetic force, 10 is a gap, and 11 is a cooling unit. Dice, 12 is a cooling pipe, 13 is a degaussing circuit, 14
1 is a straightening die, and 15 is a heating heater.

First, the operation of the magnetic field extrusion molding apparatus will be explained based on FIG. 1A.

The mixture of rare earth magnet powder and thermoplastic resin charged into the hopper 1 is heated to a predetermined temperature by the heater 3 in the cylinder 2, kneaded by the rotation of the screw 4, and transferred to the tapered barrel part 5 made of non-magnetic material. Extruded.

Next, the rare earth magnet powder in the kneaded material is oriented perpendicular to the direction of extrusion and in the thinner direction by a magnetic field generated in the magnetic circuit 6 which also serves as a die.

As shown in FIG. 1B, this structure has an E-shape facing upward and downward, with a tapered middle portion and a gap 10 between the two.

Magnetic field coils 7 and 8 are set on both sides, and lines of magnetic force 9 flow in the direction of the arrows shown in the figure due to direct current flowing from a separate direct current power supply to generate a magnetic field in the gap 10.

Normally, the gap 10 is in the range of 10 to 20 mm, depending on the thickness of the tape-shaped magnet to be formed, and a forming die is sandwiched between the gap 10 and used.

The oriented kneaded material is cooled and solidified by flowing water through a water-cooled pipe 12 wound around a cooling die 11.

Up to this point, due to the residual magnetic field caused by the orientation magnetic field, the magnetization balance is disrupted when the molded products are attracted to each other in the subsequent process or when multipole magnetization is performed in a ring shape, so demagnetization is performed by the demagnetization circuit 13.

The degaussing circuit 13 has the same structure as that shown in FIG. 1B, but by making the currents flow in the magnetic field coils 7 and 8 in opposite directions, the lines of magnetic force 9 generated are in the opposite direction, thereby demagnetizing the circuit. .

Through the above steps, a resin-bonded rare earth anisotropic permanent magnet with magnetic anisotropy added perpendicularly to the thin direction of the tape-shaped permanent magnet and whose surface magnetic flux density is close to zero due to demagnetization is formed.

Next, the straightening die 14 is heated to a predetermined temperature by the heating heater 15, passed through the die and cooled, and is twisted and rolled into a spiral shape as shown in FIG. Wrap it around, fix it with epoxy adhesive, and cut it into rings to a predetermined length to make a ring-shaped permanent magnet.

As described above, a straightening die is attached to the magnetic field extrusion molding apparatus to change the tape shape into a spiral shape and then into a ring shape.

The aforementioned rare earth magnet powder has the general formula Sm
(Co0.0627Cu0.008Fe0.22Zr0.028) 8.35 is a magnet powder obtained by pulverizing a 2-17 intermetallic compound alloy to a particle size of 2 to 80 microns using a ball mill.

To 65% by volume of the magnet powder thus produced, 15% by volume of thermoplastic resin nylon-6 and 20% by volume of nylon-12 were added and mixed in a mixer.
The material is put into a magnetic field extrusion molding device from hopper 1.

Cylinder 2 is heated to approximately 300℃ by heater 3.
The mixture is kept at
It reaches the tapered barrel portion 5 made of non-magnetic material, and the gap 10 of the magnetic circuit 6 made of magnetic material is reached.
Lines of magnetic force 9 caused by direct current flowing through the magnetic field coils 7 and 8 through the cooling die part 11 made of a magnetic material fixed to the magnetic field coils 7 and 8
The rare earth magnet powder in the mixture passes through the mixture while being oriented.

The dimensions of the cooling die part 11 are as follows: the gap corresponding to the molding thickness is 0.8 mm, the width of the gap is 8 mm, the thickness of the die itself is 10 mm, the width is 12 mm, and the gap part 10 of the magnetic circuit 6 is also aligned with the die part 11. The dimensions were set as follows.

A current is passed through the magnetic field coils 7 and 8, and the generated magnetic field is
15000 (Oe).

A graph showing the relationship between the strength of the magnetic field (KOe) generated in the dice 11 and the current (A) is shown in FIG.

Next, when the mixture passes through the cooling die 11, the mixture is cooled and solidified by flowing water through the water cooling pipe 12, and passes through the magnetic circuit 6 and the degaussing circuit 13 made of a magnetic material having the same specifications as the die part 11. As a result, lines of magnetic force 9 in the opposite direction to the orientation act to cause current to flow in the magnetic field coils 7 and 8 in the opposite direction, resulting in demagnetization. The magnetic field coils 7 and 8 are similar to those described above, but the demagnetizing magnetic field is set by controlling the current.

Next, it enters a straightening die 14 heated to a temperature in the range of 180±20°C by a heater 15, and is twisted and rolled. With this method, the inner diameter is about 17mm and the length is 600mm.
mm spiral magnets were molded.

After applying epoxy resin to the outer diameter of a ring-shaped mandrel with an outer diameter of 16 mm and a length of 120 mm, and wrapping it while adhering it.
It was heated at 80°C for 1 hour and then cut with a cutter to obtain a rotor magnet with an outer diameter of 17.6 mm and a length of 18 mm.

On the other hand, using the mixture of rare earth magnet powder used in this example, nylon-6, and nylon-12, an isotropic tube of the same size was formed by extrusion molding, cut into a length of 18 mm, and then extruded. A rotor magnet similar to this example was obtained by adhesively fixing it to a ring-shaped mandrel having a diameter of 16 mm.

Both rotor magnets obtained by the above method were magnetized with two poles inside and outside, and the surface magnetic flux density was measured using a Gauss meter and a Hall probe. The rotor magnet manufactured by the method of the present invention had a magnetic flux density of approximately 2100 (G). The isotropic rotor magnet produced by the conventional extrusion molding method showed approximately 900 (G), and it is clear that the rotor magnet produced by the method of the present invention is superior.

Example 2 The same rare earth magnet mixture as in Example 1 was used and the same method was used, except that the gap between the dice 11 was set to 0.5 mm,
Molding was carried out with a gap width of 5 mm.

The orientation magnetic field in the gap is the same as in Example 1, 15000 (Oe)
And so.

Furthermore, the dimensions of the gap portion 10 of the magnetic circuit 9 remain unchanged.

Replace the straightening die 14, outer diameter 8mm, length 150
mm spiral magnet is formed, wrapped around a ring-shaped mandrel with an inner diameter of 7 mm, glued, and cut to have an outer diameter of 8 mm.
obtained a rotor magnet.

On the other hand, using a mixture of the rare earth magnet specified in this example, nylon-6, and nylon-12, an isotropic tube of the same size was formed by extrusion molding.
A ring-shaped mandrel similar to that in Example 1 was glued inside the tube, and the outer diameter was 8 mm and the length was 8 mm as in Example 1.
obtained a rotor magnet.

Both rotor magnets obtained by the above method were polarized inside and outside, and the surface magnetic flux density was measured, and it was found that the rotor magnet manufactured by the method of the present invention was approximately
800 (G), and an isotropic rotor magnet made by conventional extrusion molding showed approximately 210 (G).

Although the embodiments have been described above, the cross-sectional shape of the tape to be extruded does not have to be flat, but may be the cross-sectional shape shown in Fig. 4, and the tape can be wound in multiple strips by extremely reducing the pitch of the spiral. A rotor magnet as shown in FIG. 5 can also be manufactured.

[Effects of the Invention] As described above, in the method for manufacturing a ring-shaped permanent magnet of the present invention, since it is made into a tape shape in the process of adding magnetic anisotropy, a large amount of magnetic field can be obtained, so that the magnetic particles are well oriented and can be directly In the method of adding radial anisotropy to a ring shape, it may not be possible to obtain an orienting magnetic field depending on the shape, but this method is particularly useful in such cases.

Moreover, since it is formed into a ring shape after being formed into a spiral shape, it has the effect that a long and thin radial magnet can be manufactured.

In addition, thin-walled magnets are possible because the method is made into a spiral and then wrapped around a ring-shaped mandrel. Also, by wrapping a tape-shaped material around a ring-shaped mandrel, there is less change after hardening, so there are fewer cracks and cracks, and it is possible to create a thin magnet. There is no need to roll thin-walled products in multiple layers to make them thick, and you can form them to a predetermined thickness.
It can be wrapped around, which also has the effect of reducing costs.

[Brief explanation of the drawing]

Figures 1A and B are explanatory diagrams showing the manufacturing method in an embodiment of the present invention, Figure 2 is an explanatory diagram of a molded magnet product in this embodiment, and Figure 3 is a diagram showing the relationship between coil current and generated magnetic field strength. Related graphs, Figures 4 and 5
The figure is a sectional view of a molded magnet in this embodiment. 1...Hopper, 2...Cylinder, 3...Heater, 4...Screw, 5...Taper barrel part, 6...Magnetic circuit, 7, 8...Magnetic field coil, 9...Magnetic field line, 10...Gap , 11...
Cooling die, 12...water cooling pipe, 13...demagnetizing circuit, 14...straightening die, 15...heating heater.

Claims (1)

[Claims] 1. A method for producing a ring-shaped permanent magnet with magnetic anisotropy by extrusion molding in a magnetic field, comprising: extruding a spiral tape using resin-bonded rare earth magnet powder; 1. A method for producing a ring-shaped permanent magnet, which comprises winding the magnet around a ring-shaped mandrel, and then cutting the magnet into rings of a predetermined length.