JPS5972702A - Molding of magnetic slurry in magnetic field and device thereof - Google Patents

Abstract

PURPOSE:To obtain a molded body adhered with anisotropy in the radial direction by a method wherein the slurry of ferrite magnet powder is supplied into cavity space of a metal mold built in with the permanent magnet body of an outside pole on the outside circumference, the liquid only is filtered to be drained, and pressure is applied in the axial direction of the same cylindrical cavity space. CONSTITUTION:A filter 8 is set on the upper part of a fixed die 1 and a central core 6, and the slurry of ferrite powder is filled up in cavity space 10 through a hole part 6a and a lateral hole 6b from a feed pipe in the condition that a lower punch 7 is lowered than the lateral hole 6b. At this time, the device acts to absorb water pressing the filter 8 to drain only water leaving the ferrite particles in the cavity. When supply of the slurry is stopped, the lower punch 7 pushes upward to compress the ferrite powder draining water, and the press molded body having the prescribed density can be obtained. Because the multipolar permanent magnet 3 to generate a magnetic field in the radial direction is provided to the die 1, the circularly cylindrical press molded body whose ferrite particles are adhered with multipolar anisotropy in the radial direction along the line of magnetic force thereof can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the production of anisotropic ferrite magnets,
In particular, the present invention relates to a method and apparatus for molding a magnetic slurry in a magnetic field to impart anisotropy in the radial direction.

The plate-like hexagonal structure of the magnetoblanbite phase, which has Sr, a type of Pb), has a magnetic easy axis (C-axis) in the direction of the six-fold symmetry axis. There are two types of magnets: those whose C-axis directions are aligned by applying an electric current, and those whose C-axis directions are not aligned.The former are called anisotropic magnets, and the latter are called isotropic magnets, and are generally commercially available. In addition, when molding anisotropic magnets, there are two methods: filling a mold with ferrite magnet powder and compression molding, and compression molding the ferrite magnet powder as a slurry suspended in a liquid such as water. It is well known that the former method is called the dry method and the latter is called the wet method.The wet method has excellent orientation of ferrite magnet particles and has much better magnetic properties than the dry method.

That is, the wet anisotropic magnet has the highest magnetic properties. It is often used for speakers as an anisotropic magnet in which the press compression direction and the C-axis direction of the particles are in the same direction.

By the way, cylindrical magnets are used as magnets for micro motors or dynamo generators, but these are isotropic magnets. For this reason, the magnetic properties were poor, and the torque or electromotive force was small.

It has been suggested that it be sexualized.

Conventionally, in magnetic field molding of ferrite, it is common to apply a magnetic field using an electromagnet. However, when applying a multipolar magnetic field in the radial direction.

There are many difficulties involved in using electromagnets. The electromagnet must be large enough to generate the required magnetic field. The installation space for the emitter magnet is limited, and the pitch between the poles is 30 va.
If it is small, such as less than or equal to t.

It is necessary to construct the electromagnet compactly using extremely thin wires. If a thinner wire is used, the resistance value will be higher, and therefore the amount of heat generated will increase when the required current is passed, resulting in the inconvenience that the wire coating may be destroyed. Alternatively, depending on the power supply conditions, even the required current may not be able to flow. Moreover, in the wet method of magnetic field forming, it is necessary to apply a magnetic field until the density of the powder changes from a coarse state to a dense state while filtering water, and the duration of the magnetic field for orientation ranges from 10 seconds to 6 seconds.
Heat generation is a big problem because it requires a long time of 0 seconds. Therefore, it is difficult to put it into practical use using electromagnets.

We are still adding a second press to one press to increase production efficiency.
As shown in the figure, it is preferable to install a mold having a plurality of powder filling cavities 10, but for the reason mentioned above, the electromagnet becomes large, so the size of the mold for one cavity becomes large. So.

It becomes impossible to provide multiple cavities in a mold compatible with one press machine.

In view of the above problems, it is an object of the present invention to provide a rational wet magnetic field molding method and a compact device capable of imparting anisotropy in the radial direction.

The method of the present invention involves supplying a slurry of ferrite magnet powder to a mold cavity having nine cylindrical cavities (in which a multipolar permanent magnet body is built in the outer periphery of the cavity to generate a radial magnetic field in the cavity). A method for molding magnetic slurry in a magnetic field, characterized in that only the liquid of the slurry is filtered and drained, and the cylindrical cavity space is pressurized in the axial direction to obtain a molded body having anisotropy in the radial direction. be.

The device used in this method is a magnetic field molding device for magnetic slurry that presses and molds a cylindrical slurry while applying a magnetic field in the radial direction, and has holes and creates a radial magnetic field in the holes. In this way, an outer wall mold containing a multipolar permanent magnet placed around the hole (5), an inner wall mold placed in the hole, and a space between the inner and outer wall molds is filled with ferrite magnet powder. a slurry supply mechanism provided in the inner wall mold to supply slurry; a lower punch that moves in and out of the space between the inner and outer wall molds; and a lower punch installed in both molds on the opposite side of the lower punch in the space. This is a magnetic slurry molding device in a magnetic field, characterized in that it has a filtration device for filtration of liquid in the slurry.

According to the present invention, it is possible to perform wet molding of ferrite magnet powder with anisotropy in the radial direction without the problem of heat generation using a small device and requiring no power source to generate a magnetic field. can.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention shown in the drawings will be described in detail below.

Referring to FIGS. 3 and 4 showing the magnetic field molding apparatus according to the present invention, 1 is an outer wall mold, and has a vertical hole in the center. Inside this die 1, there is a magnetic ring 2 made of a soft magnetic material concentric with the vertical hole, and a high energy product having non-magnetic materials (6) 4 alternately arranged at approximately equal angular intervals inside the magnetic ring 2. It has a rare earth magnet 3 and a cylinder 5 made of non-magnetic cemented carbide disposed inside the rare earth magnet 3, and this cylinder 5 defines the vertical hole. 6 is an inner wall mold (center core) placed inside the cylinder 5 and is made of cemented carbide.

A cavity 10 is formed between the cylinder 5 and the cylinder 5.

At the bottom of the core 6 is a hole 6a connected to a supply pipe (not shown) for slurry of ferrite magnet powder.

Furthermore, it has a horizontal hole 6b that connects the hole 6a and the above-mentioned cavity 10. 7 is a downward punch.

It now moves in and out of cavity 10.

At least the portion in contact with the die 1 and the core 6 is made of a hard non-magnetic alloy. 8 is the die 1 and the core 6
It is a non-magnetic filtration device with a small hole 9 placed on top and communicating with the cavity.

A filtration device 8 is set on the upper surface of the fixed die 1 and core 6, and with the lower 4-inch 7 lower than the horizontal hole 6b, a slurry of ferrite powder is poured into the hole from a supply pipe (not shown). Part 6
a. The cavity space 10 is filled through the horizontal hole 6b.

At this time, a water absorbing device (not shown) operates while pressing the filter device 8, and only water is drained while leaving the ferrite particles in the cavity. When the supply of slurry is stopped, the lower punch 7 presses upward to compress the ferrite particles while draining water, thereby obtaining a press-molded body having a predetermined density.

At this time, since there is a multi-pole permanent magnet in the die 1 that generates a magnetic field in the radial direction, along the lines of magnetic force.

A cylindrical press-molded body is obtained in which the ferrite particles are anisotropically multipolar in the radial direction.

After this, the press molded body is ejected from die 1.

After drying, it is sintered.

The sintered permanent magnet body shrinks according to the poles during press molding, that is, the shrinkage is large in areas close to the magnetic poles, and slightly smaller in areas not adjacent to the magnetic poles, and there are slight irregularities on the outer periphery. It is best to sand the outer periphery a little with a centerless sander.

However, if the number of poles is large, such unevenness will be eliminated. Thereafter, a permanent magnet is manufactured by multipolar magnetization in the radial direction, similar to the application of a magnetic field during press molding.

A specific example will be described below.

In the apparatus shown in FIGS. 3 and 4, the outer diameter of the cavity 10 is 32fiWφ and the inner diameter is 17φ, and the length of the magnet 3 is 7φ.
A rare earth magnet (Br 12 kGauss, nHc) constructed with dimensions of 17 mm wide and 2.5 m thick
9KOe, (BH)maX2s MGσ (materials were used) were arranged in the radial direction at equal intervals of 24 poles.

Into such a mold, a slurry of Sr ferrite having a particle size of 0.8 μm was filled under pressure into the cavity 10, and molded. The pressed body was sintered at 1260°C and magnetized with 24 poles in the same direction as the molding.

The total magnetic flux density in the radial direction was measured and was 1,400 Gauss.

For comparison, it is 700 to 1000 Gauss for an isotropic magnet. From this, it can be seen that according to the present invention, a magnet with improved characteristics due to magnetic field orientation can be obtained. At this time, the shrinkage rate in the radial direction was 18% and that in the axial direction was 12%.

When the outer peripheral surface was polished and observed, 24 streaks were observed in the axial direction (9). This corresponds to the 24 magnetic poles, and is due to the difference in the amount of light reflected between the parts aligned with the C-axis of the ferrite particles and those not aligned with the C-axis.
This is a result of the magnetic field orientation being performed by the magnet.

The basic structure and basic operation of the present invention have been explained above, and the present invention has the following effects.

(1) Since a permanent magnet is used in the multi-pole magnetic field generator built into the die, it is difficult to construct a multi-pole structure when using an electromagnet, and is complicated, large-sized, and expensive. m
The present invention is effective from the viewpoint of energy saving.

(2) It is difficult to fill a die with a built-in permanent magnet with ferrite powder using the dry method, and the characteristics vary widely due to non-uniform density.1 The present invention takes full advantage of the advantages of the wet method. These shortcomings have been resolved.

(3) In the above explanation, the press machine used one cavity space.
) For this reason, it is possible to install a mold with multiple cavity spaces in one press machine as shown in Figure 2, and multiple cylindrical magnet bodies can be installed per so-called i4 inch vertical movement stroke. It has the advantage of being extremely efficient in production.

(4) Compared to the isotropic ferrite magnets of conventional dry or wet methods, by using the anisotropic permanent magnets made possible by the present invention, the motor can generate torque,
In a generator, the electromotive force is greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a model diagram of lines of magnetic force showing the magnetic field orientation of a cylindrical anisotropic ferrite molded body obtained by the present invention. FIG. 2 is a plan view of an apparatus in which a plurality of powder filling/cavities are provided in a mold installed in one press machine. FIG. 3 is a half-sectional plan view showing one embodiment of the present invention. FIG. 4 is a partially cutaway front view. 1... External wall mold (die), 2..., Magnetic ring, 3
... magnet, 4 ... non-magnetic material, 5 ... non-magnetic cylinder,
6...Inner wall mold (center core), 7...Lower punch, 8...
・Offshore passing device.

Claims (1)

[Claims] 1. A slurry of ferrite magnet powder is placed in a cylindrical cavity space of a mold that has a multipolar permanent magnet body built into the outer periphery of the cavity so as to generate a radial magnetic field in the cavity space. Molding of magnetic slurry 1 in a magnetic field characterized by supplying the slurry, filtering and draining only the liquid of the slurry, and applying pressure in the axial direction of the cylindrical cavity space to obtain a molded body having anisotropy in the radial direction. Law. 2. A magnetic field molding device for magnetic slurry that presses and molds a cylindrical slurry while applying a magnetic field in the radial direction. an outer wall mold having a hole and incorporating a multipolar permanent magnet arranged around the hole to create a radial magnetic field in the hole; an inner wall mold disposed in the hole; A slurry supply mechanism provided in the inner wall mold for supplying slurry of ferrite magnet powder to the space between the inner and outer wall molds, a lower punch that moves into and out of the space between the inner and outer wall molds, and the space. 1. An apparatus for molding magnetic slurry in a magnetic field, comprising a filtration device for filtering liquid in the slurry, which is installed on both molds at the bottom and opposite sides of the mold.