JPS62141712A - Manufacture of ferrite magnet - Google Patents

Abstract

PURPOSE:To obtain a composite type ferrite magnet of excellent magnetic characteristics stably by dividing a metal mold cavity into a plurality of sections with a partitioning member, separately supplying by pressure two sorts of suspensions which are different in magnetic characteristics into the divided cavity, removing the above-mentioned partitioning member immediately after the supplying by pressure and by pressing for formation. CONSTITUTION:A calcined material of composition Fe2O3/SrO=5.5 (mole ratio) is added with 1.0wt% CaCO3 and 0.5wt% SiO2, ground and magnetic powder for high Br is obtained. Magnetic powder for high IHc is also obtained by adding 1.0wt% CaCO3 and 2.0wt% Al2O3 to the above-mentioned calcined powder and by grinding. Two sorts of suspensions are made by adding polyvinyl alcohol to each above-mentioned magnetic powder and by dispersing in water. The above-mentioned suspensions are sent in a supply by pressure device, the two sorts of suspensions are supplied by pressure in a cavity 4 for forming, then a partitioning member 8 is removed and formed in a magnetic field to obtain a formed object, which is sintered and then magnetized and a composite ferrite magnet is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a ferrite magnet for a field used in a permanent magnet rotating machine such as a permanent magnet generator or a permanent magnet motor.

(Prior art) Rotating electrical machines using permanent magnets have been widely used, especially small motors and generators using arc segment ferrite magnets, and in recent years ferrite magnets have also been applied to large motors. It has spread. In particular, the number of motors that have a very large load at startup, such as starter motors for starting engines and motors for driving near conditioner compressors, has increased. For this reason, since the demagnetizing field due to armature reaction is large, magnets with especially high demagnetizing strength among ferrite magnets are used. however,
In order to improve the output, it is necessary to have a high residual magnetic flux density, and moreover, as the output increases, the demagnetizing field due to armature reaction increases, so it is also necessary to have a high coercive force. However, it is difficult to satisfy these requirements with a ferrite magnet having a single composition, and there are certain limits in terms of output improvement and demagnetization characteristics.

Therefore, in order to overcome this limit, for example, JP-A-52-3
As described in Publications No. 199 and No. 55-56456, a composite ferrite magnet has been proposed that consists of a portion having a larger residual magnetic flux density than the other segment portion and a portion having a larger coercive force than the other segment portion. ing.

The manufacturing method for this ferrite magnet includes, for example, injecting a material with a high coercive force into a mold space, then injecting a material with a high remanence, and then dehydrating, forming in a magnetic field, and sintering (Japanese Patent Application Laid-open No. 52-3199) or a method in which the mold is divided into several parts, each raw material is injected and then pre-compressed, and then the partition plates are removed before compression molding (JP-A-57
-11001&) has been proposed.

(Problems to be Solved by the Invention) However, the above-mentioned prior art has the following problems.

First, in the method described in JP-A-52-3199, in which two types of materials are injected into a mold at different times, large shrinkage deformation occurs when the obtained molded body is fired, resulting in defects such as cracks. There was a problem in that it was easy for this to occur.

Next, as described in Japanese Patent Application Laid-open No. 57-110018,
A similar problem occurred in a method in which preliminary compression, partition plate removal, and molding were performed in this order.

The purpose of the present invention is to solve the problems of the prior art described above,
It is an object of the present invention to provide a manufacturing method capable of obtaining a permanent magnet capable of obtaining a defect-free composite magnet.

(Means for solving the problem) The method for manufacturing a ferrite magnet of the present invention is based on MO.nFe2
O, (M: one or more of Ba, Sr, Pb, n=5~
6) is mainly composed of oxide powder having the basic composition, and
Two or more suspensions with different magnetic properties are injected into the mold cavity, molded in a magnetic field, and then sintered to create a region with a higher residual magnetic flux density than the others and a region with a higher coercive force than the others. In the method for manufacturing a ferrite magnet in which a region is integrated with a ferrite magnet, the mold cavity is divided into a plurality of parts by a partition member, and the suspension is introduced into the divided cavities so that the pressure difference between each suspension is maintained. The present invention is characterized in that the material is pressure-fed at the same time so that the weight is 4 kg/am" or less, and immediately after the pressure-feeding, the partition member is removed and then pressure molding is performed.

(Example) The details of the present invention will be explained below with reference to Examples.

Figure 1 is a longitudinal sectional view of the molding device used in the present invention, Figure 2
The figure is a sectional view taken along the line xx in FIG. 1 (however, the magnetic field coil is omitted).

In both figures, 1 is the die body, and the lower cylinder 1
Multiple pieces made into 11 moving boards of 3! 12 and is movable up and down. The die body 1 is provided with a molding cavity portion 4, and the side walls (la, lb) of this die body are provided with suspension supply holes 16a, 16b.
, 16b are connected to a suspension pumping device (not shown) via supply pipes 17a and L7b. A non-punch 2 is supported on a pedestal 10 installed on a floor 9, and a partition member 8 is attached to a part of it.
It is mounted so as to be movable up and down by a middle cylinder 14 installed on a frame 10.

A backing 19 such as an O-ring is attached to the outer periphery and joint portion of the lower punch 2 and the partition member 8 in order to prevent the suspension from leaking due to the suspension injection pressure in the molding cavity 4. The upper punch 3 fixed to the upper cylinder 15 is movable up and down so that it can be joined to the upper surface of the molding cavity 4. The upper punch 3 is provided with a plurality of drainage holes 5, and the filter body 7 is provided with a plurality of drainage holes 5.
Through the drain hole 5, the liquid medium of the suspension is discharged to the outside of the molding cavity 4, and then to the outside of the apparatus via the liquid collecting chamber 6 and the drain pipe 21. A magnetic field coil 18 is installed around the outer periphery of the die body to enable magnetic field orientation of the ferrite powder.

Next, a manufacturing process using the above manufacturing apparatus will be explained with reference to FIGS. 1 and 3.

First, as shown in FIG. 1, the die body 1 and the upper punch 3 are
and move the partition member 8 to a predetermined position. Specifically, by operating the lower cylinder 13 and raising the movable plate 11, the upper surface of the die body 1 is raised to a predetermined position. In addition, the upper cylinder 15 is operated to release the upper punch 3.
lower to the specified position. In this way, the die body 1. A molding cavity 4 is formed by the upper punch 4 and the lower punch 2. At this time, by operating the middle cylinder 14 and raising the partition member 8 until its upper surface reaches the position shown in the figure, the above-mentioned cavity is divided into two spaces (4a, 4b).
partition into.

Next, as shown in FIG. 3(a), l! Two types of suspensions S1 and S2 are simultaneously injected into the cavities 4a and 4b from the introduction holes 16a and 16b (FIG. 2), respectively, using a suspension pumping device (not shown). In this case, the injection pressure is preferably 20 to 40 kg/cm''.

Immediately after injection of a predetermined amount of suspension is then completed.

The middle cylinder 11 is operated to lower the partition member 8 [
3(b)], the upper surface of the partition member 8 is made to match the upper surface of the lower punch 2 [FIG. 3(C)], and the liquid medium of this suspension is sequentially passed through the filter body 7 and the drain hole 5. The liquid is discharged from the liquid collection chamber 6 to the outside of the apparatus via a drainage channel 21.

Next, while lowering the upper punch 3 and the die body 1,
The floating pressure of the lower cylinder 13 and the middle cylinder 14 is gradually lowered, and the upper punch 3, lower bunch 2 and die body 1 are
The pressurization progresses in between, and the final pressurization is performed. At this point, the floating pressure in the lower cylinder 13 and middle cylinder 14 has been released to a pressure sufficient to support the weight of the die body, etc.

Then, after depressurizing the upper cylinder 15 and completing all molding pressurization, the die body 1 is lowered by the lower cylinder 13 as shown in FIG. It is possible to obtain a molded body 20 in which regions 20a and 20b that meet the above requirements are integrated. An external view of this molded body is shown in FIG.

As a result of detailed study of the above manufacturing process, the present inventor found that a good composite ferrite magnet can be obtained by satisfying the following conditions.

The first condition is that when two types of suspensions are injected into the molding cavity, the difference in injection pressure (ΔPs) between the two is 4.
kg/cn+z or less. ΔP
If s is within this range, even if the partition member is removed immediately after filling the molding cavity with the suspension, the balance of both suspensions will be maintained and mixing of the two will be prevented. .

The second condition is to remove the partition member immediately after filling the suspension as described above. This is because if there is a delay in pulling out the partition member from the molding cavity, cracks (indicated by 22 in FIG. 4) are likely to occur near the boundary during firing.

In addition, in the present invention, in order to allow the partition member to move within the molding cavity, the gap g between the partition member and the die body is
(See Figure 2) cannot be eliminated. However, if the gap g between the levers is 0.05 m or less, the airtightness between the partition member and the die body is sufficient, and even if two types of suspensions are filled at the same time, they will not mix.

In the present invention, suspensions used in conventional wet molding of ferrite magnets can be used. This suspension is MO' n F
Hard ferrite powder (particle size Q, approximately 5 to 2 μm) approximately 50 to 70% by weight, represented by the general formula ez 03 (where M is one or more of Ba, Sr, and Pb, n = 5 to 6) , about 0.01 to about 0.2% by weight of a binder such as polyvinyl alcohol or methyl cellulose, and about 3% by weight of a solvent (generally water).
It is prepared by mixing 0 to about 50% by weight. Among suspensions, those that obtain high residual magnetic flux density include S i O,,
Known additives such as CaC0, etc. are added to the suspension, while suspensions for high coercivity include AQ, O, and CaC○.

It is sufficient to add known additives such as.

Experimental Example A calcined product having a composition of Fe, 03/S r O = 5.5 (molar ratio) was mixed with 0.1.0% by weight of CaC and 0.0% by weight of Si.
5% by weight was added and ground to an average particle size of 1 μm to obtain high Br magnetic powder. In addition, 1.0% by weight of CaCO3 was added to the above calcined powder.
, added 2.0% by weight of AQ203, average particle size 1.0μ
The powder was ground to obtain a high Br magnetic powder. 1.0% by weight of polyvinyl alcohol was added to each of the above magnetic particles and dispersed in water to prepare two types of suspensions ('a degree: 60% by weight).

The above suspension was put into a pressure feeding device, and then the suspension was pumped into the device shown in FIG.
Molding was performed in a magnetic field of 0006 to obtain a molded body. The obtained compact was sintered at 1150° C. for 2 hours, and then magnetized to obtain a ferrite magnet.

Here, the results of experiments conducted by changing the pumping conditions of the suspension are as follows. The pressure of the suspension for high Br is 25kg/
cm” and the pressure of the suspension for high He is 15-35k.
When changed in the range of g/am2, ΔPs is 4kg/am2.
cm” or less, the two did not coexist, whereas ΔP
When s was 5 kg/cm'' or more, a mixture of both was observed.

Further, Table 1 shows the results of experiments conducted by setting the pumping pressure of both suspensions at 20 kg/cm'' and changing the timing of removing the partition member.

Table 1 As is clear from Table 1, if the partition member is removed within 2 see after pressure-feeding, there will be no generation of cleansing.
It can be seen that the longer the removal of the partition member is delayed, the more the occurrence of sharpness increases.

Table 2 shows typical magnetic properties of ferrite magnets manufactured under conditions within the scope of the present invention.

Table 2 (Effects of the Invention) As described above, according to the present invention, a composite ferrite magnet with excellent magnetic properties can be stably obtained.

[Brief explanation of drawings]

Figure 1 is a longitudinal sectional view of the molding device used in the present invention, Figure 2
The drawings are a sectional view taken along the line xx in FIG. 1, FIG. 3 is a sectional view of a main part of a molding apparatus for explaining the manufacturing process of the present invention, and FIG. 4 is a perspective view of a molded article. 1: Die body, 2: Lower punch, 3: Upper punch, 4th
Figure d six

Claims (1)

[Claims] 1, MO・_nFe_2O_3 (M: Ba, Sr, Pb
Suspensions of two or more types of oxide powders mainly composed of oxide powders having a basic composition of one or more of the following, n = 5 to 6) and having different magnetic properties are injected into the mold cavity, and a magnetic field is applied. In a method for manufacturing a ferrite magnet in which a region having a higher residual magnetic flux density than the other region and a region having a higher coercive force than the other region are integrated by sintering after molding in the mold cavity, the mold cavity is formed into a partition member. The suspension is divided into a plurality of cavities, and the pressure difference between each suspension is 4 kg/cm^2.
A method for manufacturing a ferrite magnet, which comprises simultaneously pressurizing the magnet as follows, removing the partition member immediately after the pressurizing, and then performing pressure forming.