JPH04363010A - Method and device for manufacture of permanent magnet and rubber mold for orientation formation in magnetic field - Google Patents

Abstract

PURPOSE:To acquire a permanent magnet compact without generating cracks, flaws and chipping by arranging a rubber mold in a die press device and by acquiring a compact of permanent magnet powder by compressing rubber mold and permanent magnet powder by punching of the die press device. CONSTITUTION:Magnet powder 5 is injected from a feeder 42 to a bottomed rubber mold 10i put on a stopped conveyor 40 and filling density of the magnet powder 5 is increased by vibrating the bottomed rubber mold 10i by an excitator 1 simultaneously with the injection. When the conveyor 40 rotates, the rubber mold 10i with a rubber cover 10h moves to a middle between magnetic coils 4a and 4a and pulse magnetic field is applied to the magnet powder 5. The rubber mold 10i wherein the oriented magnet powder 5 is put slides toward a die 2 by a push rod, etc., on a base 44 provided in the same level as the conveyor 40 and an upper part of the die 2. Satisfactory orientation can be acquired even with high density filling if elasticity of rubber is applied in this way.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for manufacturing permanent magnets, and more specifically, it improves magnetic properties by compressing and orienting permanent magnet powder in a magnetic field, and is used in motors, generators, etc. This invention relates to a method for manufacturing permanent magnets that are widely used in electrical equipment. Furthermore, the present invention relates to a permanent magnet manufacturing device and a rubber mold.

As permanent magnets, BaO.6Fe2O3 and SrO.6Fe2, which have strong magnetic anisotropy in the c-axis direction, are used.
magnetoplumbite hexagonal crystal such as O3, CaCu
Sm with strong magnetic anisotropy in the c-axis direction of type 5 hexagonal crystal
Co5 alloy, Th2Zn17 type rhombohedral crystal or T
h2 Sm2Co17 alloy with strong magnetic anisotropy in the c-axis direction of Ni17 type hexagonal crystal, and Nd2Fe14B
Nd2F with strong magnetic anisotropy in the c-axis direction of tetragonal type
There are many materials such as e14B alloy, Mn-Al (tetragonal), Mn-Bi (hexagonal), etc., and anisotropy is usually performed to improve performance.

0003

[Prior Art] The most common method of anisotropy for permanent magnet powder is to fill the powder in a metal die in a state where the powder particles can rotate (pressure is applied to the powder by a punch). This method involves applying a magnetic field for a certain period of time to align the direction of easy magnetization to the direction of the magnetic field. In this oriented state, the powder is pressed in a die using a punch to obtain a green compact in which the powder is fixed so as not to move. Resin-bonded magnets, which are hardened with resin or solidified by die-pressing magnet powder and resin, and sintered magnets, which are made by sintering compacted powder, have been commercialized.

As a method for manufacturing sintered magnets, a method is also known in which powder is packed in a thin rubber mold, oriented in a magnetic field, and then the rubber mold is submerged in a liquid medium to perform hydrostatic pressing and sintering. "Magnetic Materials for a New Era" edited by the Unexplored Processing Technology Association, 1983, 2nd edition, p. 44). However, due to the inefficiency of hydrostatic press (CIP), this method is rarely practiced industrially.

Presses in a magnetic field that are often used industrially include a vertical die press as shown in FIG. 48 and a parallel die press as shown in FIG. 49. In the figure, 1a is the upper punch, 1b
2 is a lower punch, 2 is a die, 3 is a press plunger, 4 is an electromagnetic coil, 5 is a magnet powder, and 6 is a magnetic pole.

Parallel die pressing is used to manufacture anisotropic magnets that have anisotropy in the direction perpendicular to the main surface of the flat magnet.
Vertical die presses are used to manufacture anisotropic magnets of relatively simple shapes, such as blocks, whose length in the direction of magnetization is sufficiently large. In recent applications, magnets have a flat shape,
Most of the demand is for magnets that are magnetized in the direction perpendicular to the main surface. Therefore, the production volume of parallel die presses is much higher than that of vertical die presses. In particular, most ferrite magnets are produced by parallel die pressing.
It can be said that there is almost no industrial production using vertical die presses.

Table 1 shows typical characteristics of typical magnets obtained by vertical die pressing and parallel die pressing.

[0008]

[Table 1] Parallel press and perpendicular press characteristics of typical magnets

From Table 1, it can be seen that the characteristics differ depending on the orientation method in the magnetic field. That is, the magnetic properties of the sintered magnet compacted by parallel die press, especially Br and (BH)
max is lower than that of the vertical die press. As long as the same magnetic powder is used, differences in magnetic properties due to different manufacturing methods between parallel die press and perpendicular die press are highly reproducible, so magnet manufacturers publish the characteristics specified for each of these pressing methods in specifications and catalogs. are doing.

According to Japanese Patent Publication No. 55-26601,
A method has been proposed in which a pre-formed rubber container is placed in a mold, rare earth cobalt alloy powder is placed in the rubber container, and then parallel die pressing is performed. It is said that the magnetic properties are improved to the same level as die press. Furthermore, the publication explains that this method actually deteriorates the magnetic properties of the ferrite magnet.

In Table 1, "ferrite wet type" means a magnet made by sintering powder oriented in a magnetic field by wet pressing. For ferrite magnets, a wet molding technique is often used in which a slurry powder containing 30 to 40% water is molded in a magnetic field. The reason for this is that the magnetic powder easily rotates in the slurry, so when oriented in a magnetic field, a higher orientation rate can be obtained than when dry powder is used. The advantage of wet-formed ferrite magnets is that they have higher Br and (BH)max than dry-formed ferrite magnets. Another advantage of wet compaction is that the filling of powder into each press die is easy to automate. For these reasons, wet molding is more commonly performed than dry molding for ferrite magnets.

[0012] Here, referring to the specific method of die press molding of ferrite magnets in a wet magnetic field, slurry is injected into the die from a hole on the side of the die, and a single or multiple layer of paper or cloth attached to the upper punch suction port is used. Use the filter to
By compression from the lower punch and vacuum suction from the upper punch,
Water is sucked out and molded. Filters such as paper are replaced after every press or several presses due to clogging.

Unlike ferrite magnet powder, rare earth magnet powder is easily oxidized by water, so an organic solvent is used rather than water for slurry formation. However, since organic solvents are flammable and difficult to handle, dry molding is mainly used for rare earth magnets. Japanese Patent Publication No. 60-24758 discloses that a hole is made approximately at the center of an elastic body such as rubber, magnetic powder is inserted and filled into the hole, and isotropically pressurized using a multi-axis punch provided around the elastic body. We have proposed a method for producing anisotropic magnetic materials that applies pressure and a magnetic field at the same time. However, a six-axis punch is used to carry out this method, and the equipment cost is significantly higher than that of a conventional die press machine having upper and lower punches, and the price of the anisotropic magnetic material is also higher.

[0014]

[Problem to be solved by the invention] The above-mentioned Special Publication Publication No. 55-26
The method disclosed in Publication No. 601 makes it possible to produce rare earth-cobalt permanent magnets that have magnetic properties equivalent to those of vertical die presses even when using parallel die presses by oriented molding in a magnetic field using rubber as a pressure medium. In this method, the permanent magnet powder is placed in a rubber mold that has been set in advance in the mold of a die press machine, so that it is naturally filled into the rubber mold. In that case, the density will be approximately 18% or less (assuming the density of the rare earth-cobalt alloy to be 100%). If such powder is compressed into a green compact whose density is usually around 50%, the green compact will crack in the die press machine, or the rubber mold will deform unevenly during compression, requiring a design change in its shape. It was found that in some cases, the compact was deformed to an extent that could not be corrected. It is known that the orientation of magnet powder in a magnetic field is very sensitive to the packing density of the powder, and when the density is higher than natural packing, orientation in a magnetic field becomes difficult. Therefore, conventionally, permanent magnet powder was filled with a low density of 18% or less using a shaker or the like.

[0015] The present inventor also applied the method shown in the above-mentioned publication using a rubber container to produce neodymium magnets and ferrite magnets. That is, when rubber was compressed with a punch in a die press machine, and permanent magnet powder filled in the rubber was compression-molded in a magnetic field using the pressing force due to the elastic deformation of the rubber and the pressing force from the punch, after natural filling. It has been found that cracking or deformation of the powder compact always occurs when compacting the powder.

As explained with reference to Table 1 above, it is currently generally recognized that parallel die presses have inferior magnetic properties to vertical die presses in industrially produced magnets, and No parallel die press product is available on the market that has magnetic properties comparable to the vertical die press taught in the above patent. This is thought to be related to the fact that the method described in the publication causes cracking or deformation, making it impossible to obtain a product.

Therefore, the present invention utilizes the elasticity of rubber in the magnetic field orientation molding process to increase the degree of orientation of the permanent magnetic powder compact, thereby obtaining excellent magnetic properties.
The first object of the present invention is to provide a method capable of obtaining a permanent magnetic powder compact without causing cracks, cracks, chips, etc.

Furthermore, in the conventional oriented die pressing method in a magnetic field, it is necessary to adjust the timing of applying the magnetic field to the permanent magnet powder and the timing of compressing the powder, so the control is more complicated than that of a simple molding die press. was. Therefore, the present invention provides a permanent magnet having anisotropy while simplifying the control of the die pressing method like a simple die pressing method, and desirably provides a permanent magnet with better orientation than that obtained by the conventional orientation molding method in a magnetic field. A second purpose is to provide a method for manufacturing permanent magnets that can be obtained.

[0019] Furthermore, the above-mentioned Special Publication No. 55-26601
In the method of this issue, the rubber container completely surrounds the magnetic powder since it is described as replacing the pressure medium of CIP. Therefore, such a rubber container cannot be applied to a wet die press. Therefore, the present invention
By increasing the degree of orientation of the permanent magnet green compact using the elasticity of rubber in the wet-method orientation molding process in a magnetic field, a permanent magnet with excellent magnetic properties is obtained, and no cracks, cracks, or chips occur. A third object of the present invention is to provide a method for obtaining a permanent magnet powder compact.

Furthermore, in the method of the above-mentioned Japanese Patent Publication No. 55-26601, the rubber container is placed in a die press machine, and the magnet powder is placed in the rubber container. It is inefficient because the pillars that guide the lift get in the way of the feeder into which powder is charged. Further, the next cycle cannot be performed until one cycle of powder feeding, molding, and removal of the green compact is completed. Therefore, the above method is not suitable for continuous production of a large number of magnets. Therefore, the present invention provides a method and apparatus suitable for continuously producing permanent magnets having excellent magnetic properties by increasing the degree of orientation of a permanent magnet green compact by utilizing the elasticity of rubber in the magnetic field orientation molding process. The fourth purpose is to provide

In addition, the present inventor carried out orientation molding in a magnetic field using the elastic deformation of rubber, and found that the degree of deformation of the compact and the presence or absence of cracking are significantly influenced by the structure of the rubber mold. I found it. Therefore, a fifth object of the present invention is to provide a rubber mold suitable for carrying out the above method.

[0022]

[Means and effects for solving the problems] In the method for producing a permanent magnet including the step of performing orientation molding of permanent magnet powder in a magnetic field using a die press machine according to the present invention, the permanent magnet powder is placed outside the die press machine and inside a rubber mold. Either by applying vibration and/or pressing with a pusher, the permanent magnet powder is packed at high density, or by loading a preform of permanent magnet powder into a rubber mold outside the die press machine, and then pressing the rubber mold filled or loaded with permanent magnet powder into a die press machine. placed inside the aircraft,
compressing the rubber mold and permanent magnet powder with a punch of a die press machine to obtain an oriented green compact of permanent magnet powder;
Achieve your primary objective. The rubber mold referred to here is a mold whose at least side surfaces are made of rubber. Further, the rubber mold according to the present invention has a bottom part that is integrated with the mold, or the bottom part of the lower punch or the one-side closed die plays the role of the bottom part. Further, the rubber mold of the present invention may have a removable top lid made of a material such as metal or rubber, and in this case, the rubber mold also includes the top lid as a part.

When the conventional method of naturally filling permanent magnet powder is applied to a rubber mold, the packing density becomes rare earth-
18% for iron-boron magnets and rare earth-cobalt magnets
Below, it is 16% or less for ferrite magnets. In order to fully bring out the magnetic properties of these magnet powders, the particle size of the powder is very fine compared to that of general metal materials, so the fluidity is extremely poor. In general materials, a considerable amount of lubricant can be added to improve fluidity, but in magnetic materials, residual carbon etc. has a negative effect on magnetic properties, so even if lubricant is added, the amount is limited. The amount is extremely small and the flowability of the powder cannot be improved. Therefore, with general materials, it is possible to increase the density to a certain extent even with natural filling by increasing the particle size or adding a lubricant to improve fluidity, but with magnetic materials, it is unavoidable to flow due to the reasons mentioned above. Since a powder with poor properties is used, the filling rate will be the above-mentioned value by normal filling.

In the die press method using a rubber mold, the reason why cracks occur when powder is filled to such a natural packing density will be explained with reference to FIG. An example of a magnet having a flat shape will be described. In this case, in rare earth cobalt magnets, the packing density is often about 11 to 13%, and the dimensional shrinkage rate due to compression molding of the powder reaches as much as 30 to 40%. Then, the rubber mold 10
is greatly deformed as shown in FIG. 50(c). Among these deformations, the non-uniform deformation dy occurring in the lid portion 10u and bottom portion 10k of the rubber mold promotes the generation of cracks 5d in the direction parallel to the direction of pressure applied by the punch, and the non-uniform deformation dx occurring in the side portions of the rubber mold This promotes the generation of cracks 5e in the direction perpendicular to the direction of pressure applied by the punch. Further, the above-mentioned non-uniform deformation dx causes severe "elephant's foot" deformation at the edge portion of the molded body.

[0025] In a compacted compact of a magnet that has been subjected to orientation molding in a magnetic field, if demagnetization after orientation molding in a magnetic field is insufficient, magnetization remains in the compact, and the resulting magnetostatic energy causes the powder compaction to fail. Stress occurs inside the body. Therefore, even if a small crack occurs in the compact, the stress may cause the crack to expand rapidly and the compact to break into pieces. Such cracks are very likely to occur when die pressing permanent magnet powder using a rubber mold. In particular, cracks are likely to occur due to such residual magnetization, especially at the edges of the powder compact where the "elephant's foot" deformation has occurred.

In the present invention, in order to prevent cracking and deformation due to non-uniform deformation of the rubber mold and residual magnetization, it is necessary to fill the rubber mold with a higher density than natural filling. Since the densely packed permanent magnet powder is compressed in a magnetic field orientation molding process, the amount of compression is smaller than in the normal method, which reduces uneven deformation of the rubber mold and prevents cracks and poor shape of the compacted compact. . Further, regarding orientation, improvement can be seen by applying a magnetic field before compression molding and deforming the rubber in a direction orthogonal to the moving direction of the punch, which will be described later. Therefore, despite high-density packing, better orientation than conventional die press in a magnetic field can be obtained.

For high-density filling, the density is increased by applying vibration to the permanent magnet powder naturally filled in the rubber mold. Alternatively, the packing density is increased by pressing or compacting the permanent magnet powder naturally filled in the rubber mold with a pusher. Alternatively, the packing density can be increased by pressing with a pusher after vibration.

[0028] In the present invention, the term "high packing density" means a value greater than 1.2 times the natural packing density, regardless of the type of material of the magnet. The natural packing density is mainly determined by the particle size of the magnet powder, but for rare earth magnets with a particle size of 3 to 4 μm, it is 14
%, and for a ferrite magnet with a particle size of approximately 0.7 μm, it is 1
It is 2%. The packing density is preferably 25% or more for rare earth-iron-boron magnets and rare earth-cobalt magnets, and 20% or more for ferrite magnets. A more preferable packing density is 29% or more. However, if the packing density exceeds 50%, orientation will not be possible with normal magnetic field strength, so the packing density is preferably 50% or less.

In addition to the high-density filling method described above, it is also possible to preform permanent magnet powder to produce a preform having the above-mentioned "high density." This method uses a pressure machine such as a die press machine to increase the density by compacting permanent magnet powder, but presses the permanent magnet powder at a lower density than that of a normal powder compact. The density of the preform is 25-50% for rare earth magnets and 20-50% for ferrite magnets.
It is preferable that

Next, the vibration excitation method will be specifically explained with reference to FIG. Permanent magnet powder 5 (hereinafter referred to as "powder 5") whose weight has been measured in advance from a powder tray 90 is naturally filled into a rubber mold 10 having a guide frame 100 fixed to the top (see (a) of FIG. 1). Powder 5 is in rubber mold 10
It accumulates above the upper surface of the surface. Subsequently, the rubber mold 10 is placed on the vibrator 41 and vibration is applied (see (b) in FIG. 1). As the vibrator 41, an electromagnetic type or crank type vibrator that generates horizontal or vertical vibration can be used. The frequency of vibration is not particularly limited, but is, for example, 1 to 60 Hz. Vibration may be performed from the time of powder feeding or after the end of powder feeding.

Thereafter, when the powder 5 rises further above the rubber mold 10, the pusher 121 pushes down the upper surface of the powder 5 to the upper surface of the rubber mold 10 (see FIG. 1(c)). Next, pusher 121
and pull up the guide frame 100 from the rubber mold 10 (
(See (d) in Figure 1).

Further, a specific example of the method for manufacturing the preform will be explained with reference to FIG. The press machine that makes the preform is
It is composed of a die 125, a die bottom part 126 consisting of a movable bottom plate, and a punch 128. The powder 5 whose weight has been measured in advance is naturally filled into the die space from the powder tray 90 (Fig. 2
(see (a)), 15kg/cm2 to 100kg/c
Compress at a pressure of about m2 (see Figure 2 (b)). After that, the rubber mold 10 is conveyed below the pressurizing machine, the die bottom 126 is pulled out, and the punch 128 is further pushed down.
Dropping the preform 129 into the rubber mold 10 (
(See FIGS. 2(c) and (d)). It is preferable that the dimensions of the preform 129 be smaller than the internal dimensions of the rubber mold 10 in order to efficiently apply the impact force of the pulse to the preform 129.

By increasing the density of the powder and filling the rubber mold as shown in FIGS. 1 and 2 outside the press machine that performs orientation molding in a magnetic field, the idle time of the press can be reduced and productivity can be increased. can be increased. Unlike FIGS. 1 and 2, the rubber mold 10 may be integrated with a die, and the powder filling or preformed body may be loaded outside the die press machine, and then the die may be set in the die press machine.

[0034] The rubber mold must be a continuous body, either integral or segmented. Frictional forces may occur between the rubber molds, resulting in uneven deformation, which may be undesirable, but in order to make it easier to set the rubber mold in the die, it is recommended to part (10a
, 10b) and contact them in the die to form a continuous body (see FIG. 3). Although it is not preferable in terms of efficiency, granular, liquid, gel, or powder rubber 10c may be used in parts that do not come into direct contact with the magnet powder (see FIG. 4). The position in the die space where the rubber mold is placed is determined depending on the shape of the product to be manufactured so that compressive force is applied to the powder as uniformly as possible. For example, as shown in FIG. 5, a cavity 10e provided inside the rubber mold 10
Water, oil, liquid rubber, etc. may be added to the rubber mold 10 to equalize the stress inside the rubber mold 10.

In addition, in the case of the most common disk-shaped anisotropic magnet, if the rubber mold is placed in contact with the inner circumferential wall of the die, a strong radially inward compressive force is generated by the compressive force of the punch 1. . In this case, the rubber slips against the die,
It is preferable to place a lubricant, an anti-friction agent, etc. between the two so that sufficient compressive deformation occurs.

In the rubber mold shown in FIG. 1, when "elephant legs" 5a occur on the upper and lower edges of the powder compact 5' as shown in FIG. 6, the rubber mold 10b as shown in FIG.
A taper 10f may be provided at the upper and lower ends of. In the figure, 10k
is the bottom of the rubber mold.

The inner surface of the rubber mold can be coated with a lubricant such as BN (boron nitride) to reduce the adhesion force between the magnetic powder and the rubber mold, thereby preventing cracks caused by adhesion. Furthermore, if a rubber mold is used in which the inner wall of the rubber mold is covered with thin rubber, the stress applied to the powder compact when the compressive force is released can be weakened and cracking can be prevented.

[0038] Orientation molding in a magnetic field is carried out as in the usual method.
This is done by applying a magnetic field with a static field strength of ~12 kOe to the powder followed by demagnetization.

Next, preferred compression conditions will be explained. The compression ratio A1 of the powder in the plane perpendicular to the direction of movement of the punch is the compression area reduction rate in the direction of movement of the punch, which is the compression ratio S0 in the direction of movement of the punch (= dimensional reduction in the direction of punch movement/dimension before deformation). On the other hand, it is preferable to fall within the following range.

(a) Parallel die press 0<A1≦6S0, more preferably 0.4S
0≦A1≦4S0. More preferably, S0≦A1≦3.6S0. The compression ratio is the ratio of the average size change of the magnetic compact after compression to the average size of the magnetic powder before compression. The compression area reduction ratio is the ratio of the amount of reduction in the cross-sectional area of the green compact to the cross-sectional area of the magnetic powder before compression. If A1 <0.4S0, no significant effect of improving magnetic properties can be obtained. However, even within this range, there is an advantage that irregularly shaped products and ultra-thin products can be molded. 0.4S0≦A1, more preferably S0≦A
1, a remarkable effect of improving magnetic properties can be obtained. On the other hand, if A1 is too large, excessive pressing pressure will be required, which is not practical. A1≦6S0, preferably A1≦4S0, more preferably A1≦3.6S
0 is desirable. Also, if the thickness of the rubber in the direction perpendicular to the direction of movement of the punch takes a finite value that is not 0, then in principle A1
can always be larger than 0, but if the absolute value of the rubber thickness becomes too small, the rubber mold will buckle during pressing and molding will not be possible. Considering the elastic modulus of the rubber, it is necessary to select an appropriate rubber thickness so that buckling does not occur and A1 falls within a preferable value range.

(b) Vertical die press 0<A1≦4S0, preferably 0<A1≦3S
0 More preferably, 0<A1≦2.4S0 In a vertical die press, since a gap is created between the rubber mold and the molded object, there is less friction when taking out the molded object from the rubber mold, resulting in irregularly shaped products and ultra-thin products. It is possible to produce molded objects in shapes that were previously difficult to produce using die presses. Also, as in the case of parallel pressing, it is necessary to select the rubber thickness in order to keep A1 within a preferable range without causing buckling of the rubber mold. If A1 is too large, excessive pressing pressure is required, as in the case of parallel die press. However, in the case of right-angle pressing, if A1 is large, the improvement in magnetic properties will not be significant, so the upper limit value of A1 is limited to be lower than in the case of parallel pressing, as described above.

[0042] Punch pressure is 50kg/cm2 to 500
A range of 0 kg/cm2 is generally preferred. A more preferable punching pressure is 100kg/cm2 to 1000kg/cm2.
It is in the range of cm2. This value partially overlaps with the value of conventional die pressing, but is lower. This is because pressure is applied to the powder from the entire circumference of the mold due to the use of rubber, which facilitates densification. There are no particular restrictions on the shape and dimensions of permanent magnets, and they can be used for rotor magnets for wristwatches, ultra-small magnets for electronic cylinder locks, stepping motors for office automation equipment, DC motors for video cameras, ultra-thin magnets for robot actuators, etc. From small magnets to magnetic resonance
Large magnets such as e image) can be manufactured according to the present invention.

Furthermore, an arcuate powder compact can be made as shown in FIGS. 8 to 10. FIG. 8 is an overall view of the rubber mold, FIG. 9 is a sectional view of the rubber mold, and FIG. 10 is an arcuate powder compact. The upper and lower punches (not shown) each have a concave surface and a convex surface having the same shape as the upper and lower surfaces of the rubber mold 10. Furthermore, a rubber mold 1 with a cylindrical outer shape is used to make a prismatic powder compact.
0 (Fig. 11), a rubber mold for making a semicylindrical shape (i.e., a rectangular parallelepiped with a curved top or bottom) powder compact (Fig. 1
2) shows a rubber mold for making a truncated pyramid (Fig. 13) and a grooved flat plate rubber mold (Fig. 14).

In the case of a powder compact with a complicated shape, the design of the rubber mold is based on the dimensions of the rubber mold and data of the compact obtained from a simpler rubber mold with a similar shape. Designed using computer simulation to form compacted powder. Furthermore, if the shape is simple and the outer shape of the rubber mold and the powder compact are the same, the rough dimensions can be estimated using a simple design method as shown below.

In the simple design of a rubber mold, the volume of the rubber remains unchanged before and after pressing (premise 1), and the bulk density of the magnetic powder before pressing is a constant ratio to the bulk density of the compacted compact (premise 1). 2) The approximate dimensions of the rubber mold can be designed based on this assumption. When pressing the disk-shaped compact 11 using the ring-shaped rubber mold side part 10s as shown in FIG.
0/2)2-(xi/2)2}=YGπ {(x0/2
)2 − (lG/2)2}.

Assumption 2 is approximately 1.9:1 in the case of ungranulated dry ferrite powder, so yπ(xi/2)2 :YGπ(l G/2)2 =
The ratio is 1.9:1. From these two formulas, the approximate dimensions of the rubber mold side portion 10s of the powder compact to be produced can be designed. After designing, we trial-produced the green compact several times and took into consideration the ease of removing the green compact from the rubber mold, the dimensional accuracy of the green compact, the deformation of the rubber mold, the hardness of the rubber mold, etc. Adjust the dimensions of the section.

The die press machine used in the present invention may be a hydraulic press or a mechanical press, and any die press can be used, from a small manual die press machine to a large automatic die press machine, but the upper and lower cylinders move simultaneously and pressurize at the same time. It is preferable to use a double press type die press machine, a die float type die press machine or a with-drawal type press machine in which only one of the upper and lower cylinders moves, but the die moves in accordance with the movement of the cylinder.

By deforming the rubber mold described above in a direction perpendicular to the direction of movement of the punch, the degree of orientation of the permanent magnet powder is increased. The degree of orientation is generally Br/4πIs (where Br is the residual magnetic flux density and 4πIs is the saturation magnetic flux density)
It is.

The structure and operation of the present invention will be explained below, in principle, in the order of the claims. In the method of claim 2, before the step of orientation molding in a magnetic field, a magnetic field is momentarily applied to the permanent magnet powder filled in the rubber mold or a preformed body of the loaded permanent magnet powder, or by a die press in the magnetic field. It is characterized by applying a high static magnetic field. That is, according to this method, after filling a rubber mold with permanent magnet powder or loading a preformed body of permanent magnet powder into a rubber mold from the open part of the rubber mold in a dry molding method, the rubber mold is covered and the powder is filled with the rubber mold. A magnetic field is applied, and then orientation molding in the magnetic field is performed by the method of the present invention described above.

When a rubber mold is filled with magnetic powder at a very high density, the higher the packing density, the more 29
% or more, the frictional force acting between powder particles becomes large, and the static magnetic field (8 to 1
2 kOe), it becomes difficult to apply sufficient rotational force to overcome friction and orient the powder. As a result, the degree of orientation of the powder compact decreases. In the method of claim 2, before the rubber mold is subjected to orientation molding in a magnetic field, sufficient rotational force is applied to the powder by applying an instantaneous magnetic field or a magnetic field higher than the magnetic field orientation molding process to the magnet powder in the rubber mold. is generated and changes the orientation state of the powder. Thereafter, a magnetic field is again applied to the magnetic powder in the rubber mold using a die press machine, and even if the packing density is extremely high, for example, 29% or more, an extremely good degree of orientation can be obtained with good reproducibility. In order to improve the degree of orientation, it is preferable that the rotational force in applying the preliminary magnetic field be applied as an impact force. The magnetic field is 5kOe
~100 kOe, preferably 10 kOe or more, especially 15
It is desirable to apply a high magnetic field of kOe or more as a pulse of 1 μsec to 1 sec to the magnet powder at least once, preferably twice or more. Furthermore, it is important that the pulsed magnetic field has a rapid change in the strength of the magnetic field at the start, and after reaching a predetermined strength, the magnetic field strength may be constant or may gradually decrease.

[0051] In addition, if powder packed at an extremely high density is compressed as it is, the powder will deform unevenly, but by applying a magnetic field in advance as described above, the powder will be crushed and the powder will be compressed during filling. When the rubber mold is filled, the filling state changes from a locally uneven filling state to a uniform filling state. When the compact is deformed in a die press in a densely packed state, if the compact has a shape that tends to cause non-uniform deformation, such as having sharp corners, cracks and chips may occur in the green compact, and deformation of the sintered compact may occur. This causes problems such as having to take a large amount of machining allowance. However, deforming uniformly packed powder in a rubber mold is an effective solution to this problem.

The method described above in connection with claim 2 applies equally to the preform. Since the preform uses equipment that is more expensive than a magnetic powder vibration device, it is desirable to increase the density of the powder to prevent cracking and chipping as much as possible, but doing so may reduce the degree of orientation. Therefore, applying a preliminary magnetic field is effective as a countermeasure against this problem.

A specific example of an apparatus for carrying out the method of claim 2 will be explained with reference to FIG. Shown in the right half of the figure is a line for filling magnet powder and inserting it into the die press, 4a is an electromagnetic coil that crushes and orients the magnet powder outside the die, and 40 is a conveyor. ,4
1 is a vibrator that is in slidable contact with the back side of the conveyor 40, and 42 is a feeder for magnetic powder. Vibrator 41
may be contacted from the side of the rubber mold. In this line, first, the magnet powder 5 is injected from the feeder 42 into the bottomed rubber mold 10i placed on the stopped conveyor 40, and at the same time as the injection, the bottomed rubber mold 10i is shaken by the vibrator 41, and the magnet Increase the packing density of powder 5. When the conveyor 40 rotates in the direction of the arrow, the bottomed rubber mold 10i moves to the location where the rubber lid 10h is set, and then the conveyor 40 stops and the piston rod 53 of the hydraulic cylinder 52 descends to move the lid to the bottomed rubber mold 10i. Fit into. When the conveyor 40 further rotates, the rubber mold 10i with the rubber lid 10h (hereinafter referred to as the rubber mold 10h, i) moves the magnetic field coils 4a, 4a.
, and a pulsed magnetic field is applied to the magnet powder 5. Rubber mold 1 containing oriented magnet powder 5
0h,i slides toward the die 2 on a conveyor 40 and a stand 44 provided at the same level as the upper part of the die 2 by means of a push rod (not shown) or the like. The time required for the above series of operations is, for example, as follows.

(a) Injection from feeder 42: 0.5
~30 seconds (b) Vibration: 1 to 30 seconds (c) Conveyor rotation (movement from feeder 42 to the hydraulic cylinder position): 1 to 10 seconds (d) Fitting of lid 10h: 1 to 30 seconds (ho) ) Conveyor rotation (movement from the hydraulic cylinder to the position of the electromagnetic coil): 1 to 10 seconds (f) Pulse magnetic field application: 1 to 10 seconds (g) Conveyor rotation (movement from the electromagnetic coil to the die 2): 1 to 10 seconds

The timing and required time of the above series of operations (a) to (g) are controlled by the control unit 50. That is, during the operations of (a), (b), (d), and (f), the conveyor 40 is
The control unit 50 issues commands so that these operations are started after the operation stops. Also, (ha), (ho), (
It is necessary that the conveyor rotations in (g) and (g) be performed synchronously. In the above example, since the time required for (f) is the shortest, the conveyor movement in (c) will not start until the longest (b) is completed. The control unit 50 also issues commands for such standby and synchronous movement.

In FIG. 16, 51 is a motor that rotates a screw rod (not shown) provided inside the feeder 42. As shown in FIG. In response to a command from the control unit 50, the motor rotates the screw rod a predetermined number of times, and the powder caught in the screw gap is supplied in a fixed amount into the rubber mold according to the amount of rotation. Reference numeral 55 denotes a pulse excitation power source, which generates pulses with set power, desired time, and timing by the control unit 50.

[0057] At the same time as the motor finishes rotating by a predetermined amount, a feeding end signal is generated and sent to the control unit 50. When the feeding end signal is input to the control unit 50, the conveyor 40 becomes movable. 41, 5
The end signal of the corresponding operation is also sent to the control unit 50 from 4 and 55.
Once there, the conveyor 50 moves a predetermined distance in the direction of the arrow and then stops. The conveyor 40 is constructed by arranging a plurality of metal chains or belts, and an electromagnetic switch or a dielectric constant sensor provided between the two chains mechanically or physically detects the rubber molds 10h,i. When the conveyor 40 is stopped, the rubber molds 10h and 10i are accurately stopped at a predetermined position. After the die press, the rubber molds 10h,i are pushed up by the lower punch 1b and carried out from the die press by a conveyor in a direction perpendicular to the plane of the drawing.

[0058] The method according to claim 3 is a method whose gist is applying the magnetic field according to claim 2, and molding the densely packed powder or preform in a non-magnetic field using a rubber mold in a die press. The second objective is achieved by using a die press machine (see FIG. 16) without the coil 4 and its excitation power supply, or by using a simple press machine that uses a low magnetic field for demagnetization. According to this method, the structure of the die press becomes simple and the efficiency of the die press is increased. In addition, since no magnetic field is applied during molding,
Pressing time can be shortened. Demagnetization can be omitted as well, but whether or not to omit demagnetization is determined by taking into consideration the shape and dimensions of the molded body, which will affect cracks and the like since magnetization remains in the molded body.

In claim 3, molding in a non-magnetic field means that magnetic powder is exposed to leakage magnetic fields from pulse magnetic field generators, power supplies, electric motors, etc. adjacent to the die press machine, and unavoidable magnetic fields due to earth's magnetism, etc., due to orientation. This means a forming method that does not use means such as the coil 4.

[0060] In the above method, the movement of the punch and compression in the orthogonal direction using a rubber mold makes it difficult to disturb the preliminary orientation during crushing by pulses, so no magnetic field for orientation is applied to the powder during pressing. In both cases, sufficient magnetic properties can be obtained that are equivalent to those of conventional parallel die-pressed magnet products. That is, when the direction of magnetic field orientation is the same as the direction of movement of the punch, the powder particles are subjected to a force that causes them to buckle due to the upper and lower punches. In the present invention, the compressive force in the direction orthogonal to the movement of the punch acts to prevent such buckling, that is, to maintain the powder particles in the direction of the upper and lower punches, resulting in better orientation than in the conventional parallel die press. It will be done. Note that if a magnetic field is applied during compression, good orientation can be stably obtained without variation.

[0061] The die pressing method according to claims 4 and onwards will be explained below, but unless otherwise specified, these methods can be applied to both the die pressing method in a magnetic field and the die pressing method in a non-magnetic field.

In the method described in claim 4, a backup plate made of an elastic body harder than the rubber mold is disposed between the rubber mold and one of the upper and lower punches. An example of the use of the backup plate will be explained with reference to FIG. 17. When the rubber mold 10 placed in the die 2 is directly pressurized with the punches 1a and 1b, especially when the rubber is soft, the rubber flows plastically into the gap between the die 2 and the punches 2a and 2b (see (a) in Fig. 17). ), causing jamming. As a result, it becomes difficult to remove the punches 1a and 1b from the die 2, and the rubber mold 10 is damaged. Therefore, as shown in FIG. 17(b), the rubber mold 10 and
A rubber mold 1 is placed on both the upper punch 1a and the lower punch 1b.
Backup plate 12 made of rubber harder than 0
When the backup plate 12 is placed, the backup plate 12 is elastically deformed by the reduction by the punches 1a and 1b, and the punch 1
The gaps between a, 1b and die 2 are sealed. Further, the backup plate 12 may be attached only to the upper punch 1a, as shown in FIG.
, 1b may be provided with a depression, and the backup plate 12 on the ring may be attached thereto.

The backup plate 12 is shown in FIG.
) Ring-shaped objects may be fitted into the upper and lower ends of the outer periphery of the rubber mold. FIG. 18 is a plan view of an apparatus according to an embodiment of the present invention, and FIG. 19 is a side view of FIG. 18, but a partially sectional view. In this device, the die is a disk-shaped rotary die 2a, which is formed by a plurality of drilled cylindrical holes (only two are shown in the drawing, but three or more may be formed), and each die is circular. The rotary die 2a is rotated by the motor 91 so as to move along the path, and the upper and lower punches 1a,
1b is provided at a first position P1 to force it into the die from above and below, a mold loader 70 is provided at a second position P2 to force the magnet powder together with the rubber mold into the rotary die, and further, at a third position P3. Take-out devices 78, 8 take out the rubber mold containing the compacted powder from the rotary die 2a
There are 4. The rotating die 2a is rotated by the motor 91.
1, P3, and P2 are sequentially circulated.

The entire disk die 2a is not made of expensive die steel, but only the periphery that contacts the punch can be used, and the rest can be partially made of plastic, iron, etc. in order to reduce weight and cost. The mold loader 70 is driven by two cylinders 71 and 80. The cylinder 71 advances and retreats a hollow rod 79 having a suction port attached to its tip. In the position of FIG. 19, the rubber mold 10 shown on the right is inserted into the die. The cylinder 80 raises and lowers the cylinder 71 fixed to its piston 82 as a whole. In the raised state, the suction port suctions the rubber mold 10 onto the conveyor 40, and then the piston 79 moves forward while remaining in the raised state and moves above the die. The cylinder 71 then descends and inserts the rubber mold 10 into the die. 76 and 81 are hydraulic units. 75 is a fixed cam, and when the rotary die 2a rotates, the elevating bottom 2d provided in the die moves along the upper surface contour of the fixed cam 75 as shown in FIG.
Slide as shown in 0. That is, during pressing, the die is completely separated from the fixed cam 75 ((a
), then ride the hem of the fixed cam 75 (see (b)
) The rubber mold 10, in which the powder compact is placed inside, further rises along the slope of the mountain (see (c, d)), and when it reaches the flat part of the top, the rubber mold 10, in which the compact is placed inside, touches the upper surface of the rotary die 2a. The same level is reached (see figure (e)). At this time, the rubber mold has reached the third position P3 (see FIG. 19). After that, the elevating bottom 2d descends again, so that the unformed magnetic powder can be received in the die (see figure (f)).

A first conveyor 40 whose end is located near the second position P2 is provided, and the first conveyor 40 conveys a rubber mold filled with magnet powder. A pulse magnetic field generator 4a is provided at a predetermined position of the first conveyor 40, a mold loader 70 for pressing a lid onto a bottom mold is provided at another location, and a feeder 42 for magnetic powder powder is provided at another location.

A second cone conveyor 140 is provided, the end of which is located near the third position P3. Rubber mold 1
0 is guided along the rubber mold recovery plate 78 by the rotational movement of the rotary die 2a, and further slides slightly on the fixed table 84 and is delivered onto the second conveyor 140.

In the method described in claim 5, oxidation of the powder is prevented by filling or charging rare earth permanent magnet powder into a rubber mold in the presence of an inert gas. In this embodiment, the steps shown in FIGS. 1 and 2 are performed in a chamber 95 filled with inert gas, as shown in FIG. 21(a). Thereafter, as shown in FIG. 21(b), the rubber mold 10
is set in a die press machine and die pressed, (c)
The rubber mold 10 is taken out from the die press machine as shown in FIG. In this way, oxidation of the rare earth powder, which is easily oxidized, can be avoided and good magnetic properties can be maintained. This method provides significant benefits when applied to jet-milled magnetic powder in an oxygen-free atmosphere. This pulverization method uses a N2 atmosphere with an oxygen content below the detection limit, so the resulting powder has a low oxygen content and may exhibit excellent magnetic properties, but it is also extremely active and cannot be absorbed into the air. It ignites immediately and is difficult to handle.

According to the method of claim 5, the highly active powder is utilized to bring out its excellent magnetic properties, and
Combined with the effect of improving magnetic properties due to the deformation of the rubber mold, extremely good magnetic properties can be obtained.

A sintered permanent magnet can be produced by sintering the powder compact obtained by the above method using a known method and, if necessary, also heat-treating it. Further, a resin-bonded magnet can be manufactured by compacting a resin and magnet powder.

In the method according to claim 8, the steps of filling the rubber mold with high density, applying a magnetic field, die pressing, and taking out the compacted powder from the rubber mold after natural filling of the permanent magnet powder into the rubber mold are performed. In the apparatus according to claim 29, the feeder is configured to sequentially and repeatedly fill the permanent magnet powder into the rubber mold along the circulating route for conveying the mold;
pusher or vibrator, magnetic field generator, die press,
The fourth object is achieved by sequentially arranging jigs for taking out the compacted powder compact from the rubber mold.

An example of these configurations will be described with reference to FIG. 22. The rubber itself of the rubber mold 10i (see FIG. 23) forms a bottomless mold, and the open bottom of the rubber mold is closed by a part of the rotary die 2a. Therefore, the rotary die 2a constitutes the bottom of the rubber mold. The rubber mold 10i is sequentially rotated and moved on the ring-shaped rotating die 40, filling the rubber mold 10i with powder by the feeder 42, fitting the lid 10u at position C (not shown), and pulse orientation by the electromagnetic coil 4a. , die press using a die press device 60 in a magnetic field, lid 10
A series of operations such as removing u (carried out at position F) and taking out the molded body using the molded body take-out device 62 (
A to H) can be performed.

The removed lid 10u is returned to the lid fitting location C by the linear transporter 140. The linear transporter 140 (see FIG. 24) is composed of a rail that moves the suction port 140a. The suction port 140a is communicated with an intake pump, and a motor (not shown) movably mounted on the rail attracts the top cover and travels on the rail.

The magnetic field die press device 60 has upper and lower punches,
It consists of electromagnetic coils, etc. The compact removal device 62 includes an arm 64 made of an electromagnet that can be swung around a shaft 65 at a certain angle.
When the electromagnet is turned off after being absorbed and swung, the molded body is placed on another conveyor 66.

In FIG. 22, 150 is an air piston, 151 is an air unit, 152 is an electromagnet, and 153 is an electromagnet excitation power source. After the powder compact is taken out from the die, the electromagnet 152 moves above the die cavity, and is excited by the power supply 153, and uses its magnetic force to attract the permanent magnet powder remaining inside the rubber mold, thereby cleaning the rubber mold. This will be done as necessary.

[0075] Since the rubber mold 10i returns to its original shape after powder compaction, a ring-shaped gap 10r is created around the powder compact 63.
is made. This gap 10r has a size sufficient to take out the powder compact 63 from the rubber mold 10i by the above-described suction. 66 is a conveyor driven by a step motor 67 driven by the control unit 50. After the arm 64 swings above the conveyor 66 and places the green compact 63 on the conveyor 66, the conveyor 66
moves. This series of operations is controlled by the control unit 50.

[0076] Compared to a method in which the three steps of rubber mold setting, pressing in a magnetic field, and taking out the rubber mold are performed in a die press, the method shown in Fig. 22 performs only pressing in a magnetic field in a die press, and presses the rubber in other parts at the same time. Since the mold can be set and the rubber mold taken out, one press cycle can be very short, making it suitable as an apparatus for mass production.

When mass producing permanent magnets by the endless path die press method shown in FIG. 22, the time required for each step is, for example, as follows. (a) Natural filling, vibration, pusher (performed at A in Figure 22) to (b) -15 seconds (b) Top cover installation (performed at C) -5 seconds (c) Pulsed magnetic field application (performed at D) (d) Die press (performed in E) - 15 seconds (e) Top cover removal (performed in F) - 5 seconds (f) Removal of green compact and rubber mold cleaning (performed in G) -10 seconds The longest time required is 15
seconds, from each step (a) to (f) to the next step.
Since the conveyance time is seconds, one green compact is produced every 17 seconds.

Next, the time required for a typical die press to fill powder in a die will be shown. (a) Filling the powder with the feeder - 10 seconds (b) Lowering the upper punch (the upper punch descends from the position it had retreated from the feeder to the inside of the die) - 5 seconds (c) Pressing (static magnetic field applied, upper and lower punches Apply pressure, apply reverse magnetic field - 27 seconds (d) Escape adjustment - 5 seconds (e) Removal of green compact - 10 seconds (a) to (e), total 57 seconds. In the normal die press method, the entire process (a) The first step (a) until ~(e) is completed.
Unable to start. Therefore, it takes a long time of 57 seconds to make one green compact.

In the method of the present invention, it is preferable that the natural filling of the permanent magnet powder into the rubber mold and the high-density filling into the rubber mold are performed at the same place. Natural filling is performed using the guide frame 100 (see Figure 1), but if filling using a pusher or the like is performed at a different location from the natural filling, it becomes necessary to move the guide plate from the natural filling location to the pushing location. . In this case, the number of guide plates required increases and the device becomes complicated.

Furthermore, as shown in FIG. 22, rather than directly feeding the powder from the feeder 42 to the rubber mold 10, the powder from the feeder may be passed through a mesh that sieves powder lumps, if necessary, and once fed into another container. It is preferable to supply the powder from the container to the rubber mold after accurately weighing the powder. Since the fluidity of permanent magnet powder is so low that it is difficult to feed the correct weight of powder directly from the feeder to the rubber mold, it is preferable to use a separate container as described above.

In the method according to claim 10 and the apparatus according to claim 27, the same effects as those obtained by the method according to claim 5 can be obtained by housing the circumferential path in an inert gas chamber, and high performance can be obtained. To obtain a means for efficiently manufacturing rare earth magnets. Permanent magnet powders such as Nd2Fe14B and Sm-Co are extremely easily oxidized, and when the powder is oxidized, the magnetic properties immediately deteriorate. To prevent this, the rubber mold is moved through a dome-shaped enclosure filled with inert gas. The dome-shaped cover can be in the form of a ring along the circumferential path, or in the form of a disk or an ellipse that covers the circumferential path and its central space.

[0082] In the method according to claim 9 and the apparatus according to claim 31, the steps of loading the preliminary green compact into the rubber mold, applying a magnetic field, die pressing, and taking out the green compact from the rubber mold are carried out by placing the green compact into the rubber mold. The configuration is such that the process is repeated in sequence on the circular path of conveyance. In these inventions, devices 125 and 128 (see FIG. 2) for loading a preform into a rubber mold are arranged in place of the feeder 42 in FIG. 22.

-Wet molding method- Although the configuration of the present invention described above applies to both dry molding methods and wet molding methods, the features of the wet molding method will be explained here. The wet molding method uses a slurry of magnetic powder. The ratio of water or organic solvent to magnet powder in the slurry may be a known ratio, and is not particularly limited, but a weight ratio of 2 to 4 parts water to 8 to 6 parts magnet powder is preferred.

In the wet molding method, it is necessary to remove water or organic solvent from the slurry before compression is completed, but since it is difficult to make holes in the rubber mold and suck out water etc. It is essential to suck out the water in the slurry through a filter. Therefore, in the wet molding method of the present invention, a rubber mold that does not have a top lid and has rubber on the sides or on the sides and bottom is pressurized with an upper punch having water absorption holes through a filter to absorb moisture in the slurry. Orientation molding is performed in a magnetic field while being discharged from the rubber mold through the hole. In this case, since a rubber mold without a top lid is used, unlike conventional pseudo-CIP, only a part of the magnet powder is surrounded by the rubber mold (pressure transmission medium), so the isotropy of compression is slightly less. Since the friction between powder particles is reduced by the presence of water or solvent, sufficient orientation can be obtained. The lateral compression also allows for extremely high drainage speeds, greatly increasing efficiency.

[0085] As the filter, a paper, cloth filter, or a ceramic filter such as gypsum is used. Furthermore, as a method of filling and compressing the slurry into the rubber mold, there are two methods: first injecting the slurry into the rubber mold outside the die, then putting the rubber mold into the die, and compressing the rubber mold and slurry with a punch. Alternatively, a method is possible in which a rubber mold is placed in the die in advance and the slurry is injected into the mold. To fill a rubber mold with slurry: The inside of the rubber mold is evacuated beforehand, and then the slurry is filled; After injecting the slurry into the rubber mold, the slurry in the rubber mold is placed under vacuum or reduced pressure; Inside the rubber mold By performing a treatment such as injecting slurry at high pressure into the rubber mold, no air bubbles remain on the surface of the rubber mold, and defects caused by this can be reduced.

Claims 16 to 19 relate to the invention of a wet die press method that achieves the third object. If the die press machine is a wet die press machine, it is necessary to provide a device for sucking water from the rubber mold. For this purpose, it is necessary to provide a water suction hole in the upper punch that communicates with the pump to perform suction. Therefore, the wet die press method according to the present invention compresses a slurry of permanent magnet powder using a die press machine having an upper punch with water absorption holes and a filter.
In a method for manufacturing a permanent magnet, which includes a step of performing orientation molding in a magnetic field, a slurry of permanent magnet powder is filled inside or outside a die press machine, and a rubber mold with at least side parts made of rubber and an open top part is placed in the die press machine. A filter is arranged between the upper punch and the open part of the rubber mold, and during the compression, the rubber mold and permanent magnet powder are compressed, and water or water in the slurry is removed through the filter and the water absorption hole. The structure is such that the solvent is discharged. This method makes it possible to perform orientation molding in a wet magnetic field that uses the elasticity of rubber to improve orientation.

If the diameter of this water absorption hole is smaller than that of the magnet powder, only water can be absorbed, but the pump efficiency will be extremely reduced and this is not practical. Therefore, the water absorption hole should have a large diameter of 1 mm or more, for example, and and the porous ceramic, paper, between the die and
It is preferable to provide a filter made of cloth or the like. Further, a feeder can be provided for filling the rubber mold with a slurry of magnet powder outside the die press machine.

FIG. 25 is a diagram showing an example of a wet die press apparatus. In the figure, 30 is a magnetic field power supply, 31 is a hydraulic unit, 32 and 33 are hydraulic cylinders, 34 is a filter made of water-absorbing paper, water-absorbing cloth, etc., 35 is a roll around which the filter 34 is wound, and 36 is a hole punched at the tip of the upper punch 1a. 38 is a water suction pump, 39 is a motor that is a driving source for the water suction pump 38, and 42 is a raw material feeder. Reference numerals other than those mentioned above indicate the same elements as in FIG. 16.

The raw material feeder 42 is communicated with a compressed air source (not shown) when it is necessary to feed the slurry under high pressure, and after supplying the slurry to the rubber mold 10, it is withdrawn from the compression area of the punch. Due to the action of the pressure medium sent from the hydraulic unit 31 to the hydraulic cylinder 32, the filter 34 is moved along with the upper punch 1a so that its tip reaches the die 2.
It is lowered until the gap between the two is sealed. Next, lower punch 1
b rises, and at the same time the pump 38 sucks up water in the slurry through the water suction hole 36. When the suction is completed, the lower punch 1b further rises to perform compression.

The magnetic field power supply 30 is excited after the upper punch 1a seals the gap with the die 2, and the magnetic field generated by the coil 4 passes through the upper and lower punches 1a and 1b and orients the magnet powder. After the die press is completed, an operation opposite to the above operation is performed, and the roll 35 further rotates to wind up the filter 34 until the unused surface is exposed.

FIG. 26 is a diagram showing the main parts of the device similar to FIG. 25 in which the filter 34 is made of ceramic. In this device, continuous holes on the inner and outer surfaces of the ceramic are used as water absorption holes, and after die pressing, high-pressure air is blown into the water absorption holes to remove clogging caused by magnet powder, and the filter is used many times. A gypsum filter, which is available at a very low cost as a ceramic filter, or a filter with a two-layer structure to improve durability and water absorption can be used.

FIG. 27 is a graph explaining the operation of the apparatus of FIG. 25. First, the upper punch 1a descends from the upper limit to the lower limit, and almost at the same time when it stops, the power source is excited, and immediately after that, the water suction pump is energized. That is, a positive magnetic field is applied to the magnet powder by a magnetic field power source to orient the magnet powder, and water is removed from the slurry by a water suction pump during the orientation. At the same time as the vacuum pump is energized, the lower punch begins to rise, pushing out water from the slurry. Furthermore, the lower punch is raised to the upper limit to compress the magnet powder to a desired density. Thereafter, the magnetic field power supply is de-energized and re-excited to generate a reverse magnetic field that is weaker than the positive magnetic field, thereby reducing the residual magnetic flux density of the magnet powder so that it can be easily handled thereafter. During the above processing, the vacuum pump remains energized to further remove moisture. After deenergizing the vacuum pump, excitation power source, and lower punch, raise the upper punch and blow out pressurized gas from the filter to remove clogging.

The above series of operations is performed by inputting the punch position, pump pressure, magnetic field strength, etc. to a control unit such as a microcomputer, and monitoring which stage it is in in FIG. 27.
The command for the next stage is controlled by giving the command to the magnetic field power source, pump, punch, etc. Alternatively, sequence control may be performed in which these operations are routineized from the beginning.

In the method described in claim 17, the rubber mold is filled with the slurry so that the shape of the top surface of the slurry filled in the rubber mold substantially matches the shape of the bottom surface of the upper punch. If the top surface of the slurry is lower than the top surface of the rubber mold, the top of the rubber mold will be greatly deformed and cracks will occur in the green compact. On the other hand, if the slurry is higher than the rubber mold, the pressed slurry will protrude onto the rubber mold and cause burrs 5g (see FIG. 28). In particular, when the upper punch 1a has a curved shape as shown in FIG. 29, the slurry 15 tends to protrude, so it is preferable that the upper surface shape of the slurry 15 matches the lower surface shape of the upper punch 1a. However, since the slurry has an amorphous shape, it is unavoidable that some unevenness will occur on its surface, but by increasing the amount of water, solvent, etc. to, for example, 60% by weight or more, the top surface of the slurry will be as droopy as possible. It is preferable not to have any. A preferred jig for carrying out the above method is a guide plate shown as 105 in FIG. and grind the slurry. Alternatively, pull up the guide plate 105.

In the method according to claim 18, generation of foam is prevented by using a slurry to which an antifoaming agent such as methyl alcohol or ethyl alcohol is added. These bubbles tend to form on the surface of the rubber mold due to the air in the slurry or the cavity of the rubber mold, and cause surface defects such as depressions on the surface of the powder compact, so antifoaming agents are used to prevent the formation of bubbles. It is preferable. Claim 19
This method aims to prevent the formation of bubbles as in claim 18, and the inner surface of the rubber mold is subjected to a vacuum treatment before or after filling with the slurry. FIG. 31 shows a vacuum evacuation method before slurry filling, and FIG. 32 shows a vacuum evacuation method after slurry filling. In the figure, 92 is a lid, and 93 is a vacuum chamber. Although the rubber mold 10 may be exposed to the atmosphere again after vacuum suction from the suction port 94, almost no air bubbles are generated.

A specific example of an apparatus for adjusting the shape of the top surface of the slurry and reducing the pressure is shown in FIG. The rubber mold 10 is fixed by a rubber mold fixing base 131 and a side presser 131. Packing 13 is attached to side presser 131.
3, an acrylic resin vacuum container 132 is airtightly fixed. A piston 135 is airtightly installed in a hole formed in the center of the upper part of the vacuum container 132 via a packing 134 so as to be movable up and down. A collar 137 is fixed to a portion of the piston 135 outside the vacuum vessel 132, and a spring 136 is connected between the collar 137 and the top of the vacuum vessel.
constantly urges the piston 135 upward. A stopper 142 is attached to the tip of the piston 135, and a slurry supply pipe 138 is fixed inside the stopper 142. The slurry supply pipe 138 is airtightly attached to the vacuum container 132 via a packing 139 so that it can be taken out and taken out, and therefore moves up and down as the piston 135 moves up and down. Reference numeral 140 denotes a reinforcing plate to which a mold release plate 141 made of a mold release material, preferably a material with low wettability with water such as fluororesin, is fixed, and the upper center thereof is a passage that can be opened and closed by an electromagnetic valve 149. The lower surface of the release plate 141 has the same shape as the lower surface of the upper punch of the die press machine.

The method of operation of the apparatus shown in FIG. 32 is as follows. That is, the piston 135 is
0, close the electromagnetic valve 149 in advance, and suck the reinforcing plate 140 connected to the piston 135 to pull it up to the position shown by the dotted line. Next, the air introduction port 145 is closed, and the inside of the vacuum container 132 is evacuated from the vacuum port 144. After that, the piston 135 is lowered,
The reinforcing plate 140 and the rubber mold 10 are brought into pressurized contact, the solenoid valve 141 is opened by remote control from outside the vacuum container 132, and the slurry is supplied from the slurry supply pipe 138 into the rubber mold 10 using high-pressure gas. After that, air is sent into the vacuum container 132 from the air introduction port 145, the piston 135 is raised, and the vacuum container 132 is hooked on the stopper 142 and lifted.

[0098] Instead of the fluid filling of the slurry shown in Figs. 25, 26 and 33, a preformed slurry can be uniformly charged and filled in a rubber mold (method according to claim 27). An example of an apparatus used for charging the preformed slurry is shown in FIG. In the figure, a piston 151 slides against the wall members 152, 153 to compress the slurry 15 and move the preform 15a from the outlet of the slurry former 160.
(see (a)). Slurry former 160
is an extruder composed of the members 151, 152, and 153 mentioned above. The preformed body 15a includes 157, which will be explained below.
The rubber molds 10s and 10k are charged by a device composed of 158, 159, and 161. Preformed body 15
a is pushed out onto the retractable bottom 159 and then the cutter 1
58 is lowered to cut. Pusher 157 after cutting
is slid onto the cutter 158 and the wall member 161 to be lowered, and the lowering is stopped when it hits the upper surface of the preform 15a (see (b)). Next, the retractable bottom part 159 is moved back, and the pusher 157 moves the rubber mold 10s,
Push the preform 15a into 10k (see (c))
.

[0099] Next, a specific example of a wet type apparatus that performs each process in a circular path will be described with reference to FIG. Note that the reference numerals in FIG. 35 that are the same as those in FIGS. 22 and 33 refer to the same members.

For example, the slurry filling device shown in FIG. 33 is installed at the position indicated by A, and slurry filling and vacuum suction are performed at the A position, or slurry filling is only performed at the A position and the slurry filling is performed at the B position. Perform vacuum suction at the location. 16
5 is a pump that performs vacuum suction, and 166 is an air unit that pumps the slurry. The vacuum chamber 132 does not need to be installed at the positions A and B. Further, a preformed slurry shown in FIG. 34 can be placed at the position A.

Next, an example of the time required for the method according to claim 26, in which each step of the wet molding method is performed in a circular path, will be shown. (a) Slurry filling (including vacuum suction) - 15 seconds (b)
Press (the operations of lowering the upper punch, applying a static magnetic field, pressurizing dehydration, applying a reverse magnetic field, and raising the upper punch are performed) - 20 seconds (c) Removing the compact (including cleaning the rubber mold) -
10 seconds The rubber mold is transported between the steps (a), (b), and (c) above, and the required time is 3 seconds. The longest required time is 20 seconds, and since the conveyance time is 3 seconds, one green compact is produced every 23 seconds.

[0102] Next, an example of the time required for each process in the case of a normal die press for filling slurry into a die will be shown. (a) Upper punch lowering - 5 seconds (b) Slurry filling - 5 seconds (c) Pressing (static magnetic field application, dehydration pressure and reverse magnetic field application are performed) - 90 seconds (d) Upper punch rising - 5 seconds (e) Removal of green compact - 10 seconds The total time required is 115 seconds. In a normal die press, it is necessary to dehydrate slowly in the dehydration process to prevent cracking of the green compact. On the other hand, in the present invention, the rubber mold is deformed in the direction perpendicular to the direction of movement of the punch and toward the mold cavity, which promotes the discharge of moisture and eliminates friction between the powder and the die. The pressing process is done in a short time. Furthermore, in the present invention, since each step can be carried out simultaneously, the productivity of the green compact is extremely high.

Claim 14 (dry method) and Claim 23 (wet method) relate to a method for manufacturing a hollow body such as a ring, in which a rubber mold is provided with a mandrel made of a harder material than the rubber mold for forming the hollow part. The configuration is as follows. Contrary to this configuration, if the mandrel is soft, the mandrel will contract in the radial direction together with the powder compact due to the pressing force of the punch.
Next, the punch is moved back and the load applied to the rubber mold and powder compact is removed, and the mandrel 10m expands so as to push out the center hole of the contracted powder compact 5 (see FIG. 36). As a result, cracks occur in the green compact 5'. Therefore, it is preferable that the mandrel 10m (see FIG. 36) be harder than the side portion 10s.

The hollow-shaped magnet is given radial anisotropy oriented in the radial direction, axial anisotropy oriented in the thickness direction, and the like.

FIG. 37 shows a specific example of a molding method for producing a green compact having two hollow parts as shown in FIG. 38 using a mandrel. Mandrels 10m and 10m' are made of metal, A recess 1a' into which the upper punch 1a is inserted is formed in the upper punch 1a. Next, preferred embodiments of a dry die press, a wet die press, and a rubber mold common to all shapes of green compacts will be described.

The first is that the material forming at least one of the upper and lower surfaces of the inner surface of the rubber mold (the material forming the upper surface is called the lid part, and the material forming the lower surface is called the bottom part) is The material is made to be harder than the material forming the side parts (this is called the side part). Contrary to this configuration, if the bottom part is soft and the side parts are hard, in addition to the uneven deformation shown in FIG. 50(c),
As schematically shown in , the bottom portion 10k tends to shrink as the side portions 10s deform, and wrinkles occur on the surface of the bottom portion 10k. These wrinkles become the starting point of cracks, and the green compact 5' breaks. In addition, soft materials tend to have powder entrapped on their surfaces, and the friction between the green compact and the mold is also large. Furthermore, when the pressure from the punch is removed, the soft bottom 10k tries to return to its original shape and undergoes reverse deformation, but at this time, the rubber at the bottom gets caught in the powder compact 5' and tries to follow the reverse deformation. , the green compact 5' cracks. These factors cause cracks in the green compact. If the side parts 10s and the bottom part 10k have the same hardness, the risk of cracking increases as the amount of compression by the punch increases. Therefore, in the present invention, the bottom and/or the lid are made of harder rubber than the side parts, or the bottom and/or the lid are made of metal or hard resin.

In the second rubber mold, the thickness (t,
(unit: mm) is expressed by the formula: t≦16h/D (where h is the thickness of the powder compact and D is the positive square root of the cross-sectional area of the powder compact). Here, the thickness of the lid or bottom and the thickness of the compact refer to the thickness in the direction of pressure applied by the punch, and the cross-sectional area of the compact refers to the cross-sectional area of the compact perpendicular to the direction of pressure applied by the punch. . As the area of the green compact increases (the right side of the equation becomes smaller), the force when the rubber reversely deforms increases, making the green compact more likely to break. Therefore, the thickness of the lid and bottom of the rubber mold should be Make it smaller. In FIG. 39 illustrating reducing the thickness of the bottom portion 10k, the bottom portion 10k is
k is pressed down by the pressing force Pa of the upper punch 1a and its reaction Pb. On the other hand, the force that creates wrinkles in the bottom portion 10k is the force Pc that causes the side portions 10s of the rubber mold and the powder 5 to contract so as to reduce their cross-sectional areas. bottom 10k
As the thickness of the former becomes smaller, the pressing force Pa, Pb of the former becomes smaller.
When the latter force becomes large and exceeds the latter force Pc, wrinkles no longer occur. Further, as a result of the following experiment, it was found that the coefficient 16 in the above equation is critical to whether or not cracks occur. Using a rubber mold (dimensions 30 x 30 x 5 mm, h/D = 0.17) having the shapes shown in FIGS. 40 (e) and (g) described later, Nd-Fe-B magnet powder was poured at 1.0 t/h. cm2
It was molded at a pressure of This molding was performed 10 times for each thickness by changing the bottom thickness (t) of the rubber mold in the range of 0.5 to 3.5 mm, to produce 10 molded bodies. As a result, the following number of cracks was obtained. t=0.5, 1.0
, 1.5mm, 0 pieces; t=2.0mm, 1 piece; t=2.
5mm, 4 pieces; t=3.0mm, 10 pieces. The above-mentioned coefficient 16 was determined from the results of this crack investigation.

41(a) to (k), FIG. 39, FIG.
Examples of rubber molds embodying the two methods shown in Figure 0 are shown below. Hatching in the figure indicates metal or hard rubber. (a) is an example in which the top lid 10u is made of soft rubber, the side part 10s is made of soft rubber, and the bottom part 10k is made of hard rubber or metal. (b) is an example in which the top lid 10u is made of soft rubber, the side part 10s is made of soft rubber, and the bottom part 10k is made of hard rubber or metal. (c) is an example in which the top lid 10u is made of thin (hereinafter simply referred to as "thin") soft rubber that satisfies the above formula, the side part 10s is made of soft rubber, and the bottom part 10k is made of hard rubber or metal. In (d), the upper lid 10u is made of thin (hereinafter simply referred to as "thin") soft rubber that satisfies the above formula, the side parts 10s and the bottom part 1.
This is an example in which 0k is made of one piece of soft rubber. (e) is upper lid 1
0u is hard rubber or metal, side part 10s and bottom part 1
This is an example in which 0k is made of one piece of soft rubber. (f) is upper lid 1
This is an example in which 0u is made of soft rubber or metal, and the side portions 10s and thin bottom portion 10k are made of integrated soft rubber. (g) is an example in which the upper lid 10u is made of hard rubber or metal, and the side part 10s and thin bottom part 10k are made of integral soft rubber. (h)
This is an example in which the upper lid 10u is made of thin soft rubber, and the side parts 10s and the thin bottom part 10k are made of integrated soft rubber. (i) is an example in which the top lid 10u is made of hard rubber or metal, the side part 10s is made of soft rubber, and the bottom part 10k is made of hard rubber or metal. (j) has no top lid, side parts 10s are soft rubber, bottom part 1
This is an example in which 0k is made of hard rubber or metal fixed to a notch in the side part. (k) is hard rubber or metal bottom 1
This is an example in which 0k is surrounded by the side portion 10s from the side and bottom surface. If the bottom is thin, the bottom bottom can be reinforced with a harder material than the top, such as metal or hard rubber. In (l), a downward protrusion is provided on the upper lid 10u of (i), and the powder is compressed to a high density with the upper lid outside the press machine.
This is an example of pressing in the state shown in ).

FIG. 42(a) shows a rubber mold having the same effect as FIG. 41(e). In the rubber mold of (a), the upper punch 1a acts as an upper lid 10u to prevent the green compact from cracking (methods according to claims 12 and 20). Furthermore, FIG. 42(b) shows the upper lid 1 in FIG. 41(i).
An example of a mold in which the upper punch 1a and the lower punch 1b perform the functions of the upper punch 1a and the lower punch 1b, respectively, is shown. Furthermore, Figure 42
41(c) shows a mold in which the upper punch 1a and the lower punch 1b are made of a hard material, and which functions as a hard upper lid 10u (see, for example, FIG. 41(e)).

If the edge 5e of the compacted compact 5' shown in FIG. 43 is sharp or if the degree of uniform deformation of the rubber mold is poor, the corner portions of the compacted compact are vulnerable to mechanical impact and are particularly susceptible to mechanical shock. Chips are likely to occur due to handling by robots in automated processes and kicking by equipment during transportation. In addition, sharp corners tend to remain magnetized even if demagnetized after orientation molding in a magnetic field, resulting in a decrease in mechanical strength. FIG. 44(a) shows that the corner portion 5e is cracked during orientation molding in a magnetic field. If a small amount of magnetization remains in the corner portion 5e after demagnetization, the corner portion 5e falls off and reverses as shown in FIG. 44(b).
The corner portion 5e, the powder compact 5' body, and the different polarities attract each other, and since these try to release the energy stored inside, chipping is more likely to occur after demagnetization than during orientation molding in a magnetic field. In order to prevent such chipping and to round the corners of the powder compact, it is preferable to provide a curved portion 10r in the rubber mold 10s as shown in FIG. 45. The curved portion 10r is one or both of the upper and lower ends of the surface of the rubber mold that faces the powder. The radius of curvature of the curved portion 10r is preferably about 0.1 to 5 mm. The present invention will be explained in detail below with reference to Examples.

The rubber mold used in Example 1 (Nd-Fe-B sintered magnet) is shown in FIG. The top lid 10u is made of metal, the side parts 10s and the bottom plate part 10k are made of soft urethane rubber (hardness 40), and a backup plate 12 made of hard urethane rubber (hardness 90) is provided under the bottom part 10k to prevent rubber from getting caught. was placed. The shapes of the mold cavities were 30 mm, 30 mm, and 5 mm.

[0112] Metallic neodymium (Nd), electrolytic iron (Fe)
, metallic boron (B), metallic dysprosium (Dy)
was blended into a composition of Nd13.8Dy0.4Fe78.2B7.6, and arc melted in argon gas to create an ingot. This ingot was coarsely ground using a stamp mill to have an average particle size of 20 μm, and then finely ground using a jet mill to have an average particle size of 3.0 μm. This fine powder is applied to the above rubber molds 10s and 10k by vibration and pusher pressure, and the packing density is 1.0 to 4.2.
It was filled so that the amount was 13 to 56%. Rubber mold 10s, 10k covered with top lid 10u, 40k
A pulsed magnetic field of Oe was applied five times for 5 μs. Thereafter, the rubber mold was placed in a die press machine, and parallel press molding was performed at a pressure of 0.8 ton/cm2 while applying a magnetic field of 12 kOe. After sintering the powder compact at 1100°C for 2 hours, it was aged at 650°C for 1 hour. Thereafter, the magnetic properties were evaluated and the results are shown in Table 2.

[0113]

[Table 2] The packing density of 1.0 g/cc is a comparative example using natural packing. Breakage and chipping judgment criteria (n=50) 〇 No chipping △ Less than 10% of the total number of cracks occur × 10% or more of the total number of cracks occur Deformation judgment criteria (n = 50) × - Failure Uniform deformation is so significant that it is impossible to adjust the dimensions through later processing, and it is difficult to improve even if the rubber mold is improved: △ - There is some uneven deformation, but it can be compensated for by adjusting the dimensions through later processing: ○ - Almost non-uniform Although there is no deformation and some non-uniform deformation remains, an almost perfect molded product can be obtained by only slightly changing the shape of the inner surface of the rubber mold.

Example 2 (Sm--Co sintered magnet) The rubber mold used in Example 1 was used. As raw materials, Sm(Co0.72Fe0.2Cu0.06Zr0.
03) An ingot having a composition of 7.3 was used. This ingot was coarsely ground using a stamp mill to an average particle size of 25 μm, and then a jet mill to an average particle size of 3.5 μm.
It was finely ground to a size of μm.

[0115] This fine powder was molded into the above rubber mold 10s,
10k was subjected to vibration and pusher pressure, and was filled to a packing density of 1.1 to 4.9 g/cm2 (13 to 58%). Rubber mold 10s, 10k with top lid 10
A pulsed magnetic field of 40 kOe was applied for 5 μs 5 times. After that, place the rubber mold in the die press machine,
0.8 ton/cm2 while applying a magnetic field of 12 kOe
Parallel press molding was performed at a pressure of . The resulting fine powder was dry pressed under the above conditions, the compact was sintered at 1215°C for 1 hour, and solution treated at 1170°C for 1 hour.
Thereafter, it was aged at 850° C. for 2 hours and then slowly cooled. Thereafter, the magnetic properties were evaluated and the results are shown in Table 3.

[0116]

[Table 3] The packing density of 1.1 g/cc is a comparative example using natural packing. Breaking and chipping determination criteria (n=50) 〇 No chipping △ Less than 10% of the total number of cracks occur × 10% or more of the total number of cracks that occur Deformation criteria (n = 50) Example 1 Same as

Example 3 (Sintered ferrite permanent magnet) The rubber mold used in Example 1 was used. Industrial strontium carbonate (SrCO3) and industrial ferric oxide (Fe2O3) were used as raw materials. These raw materials were blended in a molar ratio of 1:5.9, ground and mixed in a ball mill for 5 hours, and then calcined at 1270° C. for 1 hour. The calcined sample was coarsely ground using a stamp mill to have an average particle size of 4 μm, and then finely ground using a ball mill to have an average particle size of 0.7 μm. The obtained finely pulverized powder was dried in the air if it was to be subjected to dry pressing, and then crushed. This fine powder is applied to rubber molds 10s and 10k under vibration and pusher pressure, and the packing density is 0.6 to 2.8 g/cm2 (12 to
44%).

[0118] Rubber mold 10s, 10k with upper lid 10u
A pulsed magnetic field of 40 kOe was applied five times for 5 microseconds. After that, place the rubber mold in the die press machine and
0.8ton/cm2 while applying a magnetic field of 2kOe
Parallel press molding was performed at a pressure of . Green compact at 1200℃
The magnetic properties were measured after sintering. Table 4 shows the experimental results.
Shown below.

[0119]

[Table 4] Packing density of 0.6 g/cc is a comparative example of natural filling.Cracking judgment criteria (n=50) 〇 No cracking occurs △ Less than 10% of the total number of cracks occur × of the total number Deformation criteria for occurrence of cracking of 10% or more (n=50) Same as Example 1

Example 4 (Sm-Co bonded magnet) As a raw material, Sm(Co0.72Fe0.2Cu0.06Zr
0.03) with a composition of 7.3, an average particle size of 20 μm,
Bonded magnet powder having a coercive force iHc of 15.5 kOe was used. This powder was applied with vibration and pusher pressure to rubber molds 10s and 10k (see Figure 46) together with epoxy resin powder, and the packing density was 1.4 to 5.5 g/cm2.
(18 to 65%). Rubber molds 10s and 10k were covered with upper lids 10u, and a pulsed magnetic field of 40 kOe was applied five times for 5 microseconds. Thereafter, the rubber mold was placed in a die press machine, and parallel press molding was performed at a pressure of 1 ton/cm2 while applying a magnetic field of 12 kOe. After curing the green compact at 120° C. for 1 hour, magnetic properties were measured. The experimental results are shown in Table 5.

[0121]

[Table 5] A packing density of 1.5 g/cc is a comparative example using natural packing. Chipping criteria (n = 50) 〇 No chipping occurs △ Less than 10% of the total number of cracks occur × 10% or more of the total number of cracks occur Deformation criteria (n = 50) Previous example same as 1

Example 5 As raw materials, average particle size 1.35 μm, coercive force 2.7 kO
Fine powder for ferrite bond magnets (manufactured by Toda Kogyo) was used. After crushing these raw material powders, 0.5% by weight of epoxy resin is added to give a packing density of 0.6 to 2.2 g/
cm3 (12 to 44%) was filled into rubber molds 10s and 10k shown in FIG. 46 using vibration and a pusher. Rubber molds 10s and 10k were covered with upper lids 10u, and a pulsed magnetic field of 40 kOe was applied 5 times for 5 microseconds. After that, the rubber mold was placed in the die press machine and the 12k
Parallel press molding was performed at a pressure of 0.8 ton/cm2 while applying a magnetic field of Oe. The obtained molded body was heated to 120
After curing for 2 hours at ℃, the magnetic properties were measured. The experimental results are shown in Table 6.

[0123]

[Table 6] Packing density of 0.6 g/cc is a comparative example of natural filling.Crackage judgment criteria (n=50) 〇Cracked, no chipping △ Less than 10% of the total number of cracks occurred × of the total number Deformation criteria for occurrence of cracking of 10% or more (n=50) According to Example 1

Example 6 In Examples 1 to 5, the powder was filled into the die of a conventional die press machine (without a rubber mold) so that the packing density was as shown below, and the powder was pressed at a pressure of 1.5 t/cm2. Permanent magnets were manufactured in the same manner as in each example except that parallel die pressing was performed. Table 7 shows a comparison with the examples of the present invention. The magnet powders of this example and comparative example had the same composition and underwent the same treatment process. Therefore, the 4πIs of these magnetic powders are the same. Therefore, it is clear that the degree of orientation of various permanent magnets can be increased more than the parallel die pressing method by the method of the present invention, which has a Br of about 7% higher than that by the parallel die pressing method. Regarding iHc, there is a difference of about 1% between the method of the present invention and the parallel die pressing method. However, iHc is highly variable and no significant difference is observed between these methods.

[0125]

[Table 7]

Example 7 Neodymium metal (Nd), electrolytic iron (Fe), boron metal (B), dysprosium metal (Dy) were mixed with Nd13
After blending into a composition of Dy0.5Fe79.5B7.6, an ingot was prepared by arc melting in argon gas. This ingot was coarsely ground to an average particle size of 20 μm using a stamp mill in an inert gas, and then crushed to an average particle size of 3.0 μm using a jet mill in a nitrogen gas atmosphere with an O2 concentration below the detection limit. It was finely ground. This fine powder was applied with vibration and pusher pressure to the above rubber molds 10s and 10k, and the packing density was 2.6g/c.
m2 (34%) in a nitrogen gas chamber. On the other hand, an attempt was made to fill the fuel in the atmosphere, but the powder ignited, making it impossible to continue. Rubber mold 10s,
Cover 10k with the upper lid 10u (see Figure 46) and generate 40kOe.
A pulsed magnetic field of 5 microseconds was applied five times. Thereafter, the rubber mold was placed in a die press machine, and parallel press molding was performed at a pressure of 0.8 ton/cm2 while applying a magnetic field of 12 kOe. After sintering the powder compact at 1100°C for 2 hours, it was aged at 630°C for 1 hour. After that, we evaluated the magnetic properties and found that Br=13.9kOe, (BH
)max=45.1MGOe, iHc=12.8kO
e was obtained. In addition, the oxygen concentration of the sintered body is 2680 pp
It was m.

Example 8 (Wet ferrite magnet) Industrial strontium carbonate (SrCO5) and industrial ferric oxide (Fe2O3) were mixed in a molar ratio of 1:5.95.
After pulverizing with a ball mill for an hour, it was calcined at 1260°C for 2 hours. The sample after calcining is coarsely crushed, and then the average particle size is 0.75.
It was finely ground to a size of μm. The resulting finely ground slurry has a concentration (weight% of ferrite fine powder relative to the total weight) of 7.
A slurry adjusted to 1% was used.

A wet die press device shown in FIG. 25 equipped with a filter 34 made of cloth and paper as shown in FIG. 25, a vacuum suction device, and a slurry injection device, and a filter 34 made of ceramics as shown in FIG. Using the equipped wet die press, an arcuate powder compact as shown in FIG. 10 was manufactured. Slurry injection is done outside the die press.
A method was adopted in which slurry was injected from above a rubber mold placed in advance in a die (see FIG. 25), or a method in which slurry was injected into a rubber mold outside a die press machine. In other words, unlike conventional wet die presses, an injection system from the inside surface of the die was not used. Compression molding was carried out after the process was designed by finely adjusting the timing of each pressing process so that the pressing processes would not interfere with each other or cause extra waiting time.

Each sample was molded 100 times, and the incidence of defects such as cracks was investigated. For comparison, molding was performed 100 times using a conventional wet parallel die press (without using a rubber mold). For the density and magnetic properties of the sintered magnet, samples were taken every five press cycles and the average values obtained after sintering at 1235° C. for 1.5 hours were used. The magnetic properties were evaluated by cutting out a test piece from a bow-shaped magnet, processing it, and evaluating the magnetic properties with a B-H tracer. The results are shown in Table 8.

[0130]

[Table 8]

From Table 8, it is clear that according to the method of the present invention, cracking is reduced and Br and (BH)max are increased.

Example 9 (Filter Durability Test) The gypsum filter used in Example 8 and a filter with a two-layer structure consisting of two layers with different air permeability, with the side facing the slurry having lower air permeability. The durability of each filter was investigated by repeatedly molding it 100 times in the case of a gypsum filter and 10,000 times in the case of a two-layer ceramic filter.

[0133] For the gypsum filter, the failure rate during the first 1 to 20 presses and from 21 to 100 presses, and for the double-layer ceramic filter, the failure rate during the first 100 presses and the last 100 presses, and the failure rate at 1235°C. Table 9 shows the results of evaluating the magnetic properties of the magnets after sintering for 5 hours.

[0134]

[Table 9]

[0135] Compared with paper or cloth filters, ceramic filters do not require winding up of paper or cloth after pressing, so the equipment around the upper punch is simplified and troubles during mass production are reduced. In addition, paper and cloth filters require high-quality materials to be replaced every time, which is very costly, but ceramic filters can be used repeatedly and continuously, so they are very cost-effective. In addition, the surface of the sintered body manufactured using the ceramic filter is smooth, requiring less machining allowance during processing and improving yield.

[0136] The two-layer ceramic filter can be used over 10,000 times and is suitable for mass production. Gypsum filters can only be used about 100 times, but since they are extremely cheap, they can be easily mass-produced even if they are replaced every 10 presses.

Example 10 The slurry used in Example 8 was dried and crushed in a ball mill for 1 hour to produce dry powder. The bulk density of this dry powder was measured and found to be 0.80 g/cm3. This dry powder has an outer diameter of 23.95 mm, an inner diameter of 12 mm, and a height of 1
Place the powder in a 0mm silicone rubber rubber mold and perform the following methods in combination as necessary to adjust the amount of powder that can fit up to the upper limit of the rubber mold, and make sure that the bulk density (g/cm3) of the powder in the rubber mold is within the magnetic field. The effect on molding was investigated.

Step ① Place on a vibrator to increase packing density by vibration. ■Place in a tapping machine and increase packing density by tapping. ■A magnetic field is applied, and the packing density is increased by the force that attracts the powder to the magnetic field and the force that attracts the powders to each other due to the magnetic force. ■Use granulated powder that is granulated to the extent that it can be easily crushed in a magnetic field. ■Use granulated powder that is granulated relatively firmly while oriented in a magnetic field. ■Pre-forming the magnetic powder at a pressure of several tens of kg/cm2 or less to increase the packing density. In addition, a 5 μsec pulse (
40 kOe) was applied five times, and in order to confirm the characteristics of the sintered magnet, the green compact was sintered at 1230° C. for 2 hours, and the maximum energy product (MGOe) was examined.

[0139]

[Table 11] The occurrence of cracks and cracks was determined according to the following criteria. × - 5% or more of cracks or cracks occurred; Δ - 5% of cracks or cracks; ○ - Almost no cracks or cracks occurred. Non-uniform deformation of the green compact was determined according to the following criteria. × - Uneven deformation is so significant that it is impossible to adjust the dimensions through later processing, and it is difficult to improve even if the rubber mold is improved: △ - There is some uneven deformation, but it can be compensated for by adjusting the dimensions through later processing: ○ - Almost no non-uniform deformation.Although some non-uniform deformation remains, an almost perfect molded product can be obtained by just slightly changing the shape of the inner surface of the rubber mold.

Example 11 The fine powder prepared in Example 1 was molded using a series of dry parallel presses of the present invention as schematically shown in FIG. Further, the direction of the magnetic field (H) and the direction of the rubber mold 10 were set as shown in the plan view of FIG. 47. Thereafter, 100 sintered magnets were produced under the same conditions as in Example 1. Its magnetic properties are shown in Table 12.

[0141]

[Table 12] According to this method, it is possible to continuously produce magnets with stable characteristics, and the process can be automated.

Example 12 A slurry raw material for a commercially available ferrite magnet was obtained, and a conventional parallel die press and a die press according to Example 3 of the present invention were carried out, and powder compacts were sintered by each method. The magnetic properties of the sintered magnet are shown below.

[0143]

[Table 13]

Comparing this example with Table 4 of Example 3, it can be seen that the (BH)max of the comparative example in Table 13 is equal to the value of the "method of the present invention" of Example 8. In Example 11, since ferrite powder with excellent magnetic properties was used as the raw material, good values were obtained in the comparative example as well. The method of the present invention (B
H) max is approximately 10% higher than that of the comparative example, which is extremely excellent due to the use of magnetic powder with excellent magnetic properties (B
It can be seen that H) max is obtained.

Example 13 A commercially available raw material for an Nd-Fe-B magnet was obtained, and a conventional parallel die press and a parallel die press according to Example 1 of the present invention were performed, and powder compacts were sintered by each method. The magnetic properties of the sintered magnet are shown below.

[0146]

[Table 14] In this Example 13, N was used as a raw material because it had excellent magnetic properties.
Since d-Fe-B powder was used, good values were also obtained in the comparative example. The (BH)max of the method of the present invention is about 14% higher than that of the comparative example, and it can be seen that extremely excellent (BH)max can be obtained by using magnetic powder with excellent magnetic properties.

Example 14 In the method of Example 1, the influence of packing density and presence or absence of crushing by a pulsed magnetic field on magnetic properties was investigated. The results are shown in Table 15.

[0148]

[Table 15] Table 15 shows that when the packing density is high, the application of a preliminary pulse magnetic field is effective in improving the orientation.

Example 15 In the method of Example 2, the influence of packing density and presence or absence of crushing by a pulsed magnetic field on magnetic properties was investigated. The results are shown in Table 16.

[0150]

[Table 16] Table 16 shows that when the packing density is high, the application of a preliminary pulse magnetic field is effective in improving the orientation.

Example 16 In Example 3, the influence of the packing density and the presence or absence of crushing by a pulsed magnetic field on the magnetic properties was investigated. The results are shown in Table 17.

[0152]

[Table 17]

Example 17 A permanent magnet was manufactured using the same method and conditions as in Examples 1 to 5, including the steps up to the pulverization step and the steps after sintering. For Comparative Examples and Examples A and B, the following treatments were performed. Comparative example - die press in parallel magnetic field (press pressure 1.5t/
cm2, magnetic field 12 kOe) Example A - A pulsed magnetic field of 40 kOe was applied five times for 5 μsec to the densely packed powder, followed by die pressing using a rubber mold without a magnetic field. Press pressure is 1.0t/cm
2. The pressing direction was the same as the pulsed magnetic field application direction. Example B - The same pulsed magnetic field as in Example A was applied, and then parallel die pressing was performed at a pressing pressure of 1.0 t/cm 2 and a magnetic field of 12 kOe. The magnetic properties of the obtained permanent magnets are shown in Tables 18 and 19.

[0154]

[Table 18]

[0155]

[Table 19]

Tables 18 and 19 show that the method of the present invention (Example A) provides better magnetic properties than the comparative example (conventional die pressing in a parallel magnetic field). However, the magnetic properties are more stable in the magnetic field orientation method (Example B) than in the non-magnetic field pressing method (Example A).

[0157]

[Effects of the Invention] As explained above, in the present invention, cracks, chips, cracks, deformation, etc. occur in the compacted compact when pressing is performed using the elasticity of rubber to improve the orientation of the compact. The common feature is to prevent product defects due to such cracks and to provide magnetically oriented products.

[0158] Conventionally, it was thought that sufficient orientation could not be obtained in the magnetic field orientation molding method for magnet materials unless the packing density in the die was as low as natural packing, but surprisingly, the elasticity of rubber Or, by using rubber elasticity and applying a magnetic field before compression molding, sufficient orientation can be obtained even with high density packing. Moreover, defects such as cracks can be prevented by compressing the densely packed powder with a rubber mold.

[0159] In the magnetic field orientation molding method, which utilizes the elasticity of rubber to achieve the first objective, the magnetic properties are superior to ordinary die-pressed products, and in particular, parallel die-pressed products are equivalent to or better than ordinary vertical die-pressed products. Demonstrates characteristics that exceed that. However, unless the powder filling method is modified, the product cannot be obtained due to problems such as cracking, so the method of utilizing the elasticity of rubber had the potential to improve magnetic properties, but it was not actually used. could not. According to the present invention that achieves the first object, it is possible to provide a permanent magnet with improved characteristics as described below.

[0160] Nd2 Fe14B magnets are used in large quantities in small motors and actuators. In these applications, most of them have a flat shape with a small thickness in the direction of magnetization, and from the viewpoint of productivity, many of them have been manufactured by parallel die pressing. However, due to the low magnetic properties peculiar to the parallel die press, the current level of mass production is limited to obtaining 35 MGOe even if powder exhibiting the highest magnetic properties is used. However, due to the significant improvement in magnetic properties achieved by the method of the present invention, it is now possible to obtain high properties of 40MGOe, which was unattainable with magnets mass-produced using the conventional die press method, and especially 45MGOe when using oxygen-free powder. Ta.

According to the method of the present invention that achieves the second objective,
The structure of the die press machine is simplified, and the productivity of orientation molding in a magnetic field is increased by applying a magnetic field simultaneously with the die press outside the die press machine. Furthermore, by appropriately determining the packing density of the powder, high magnetic properties can be obtained as in the invention that achieves the first objective.

[0162] The wet method of the present invention, which achieves the third object, has made it possible for the first time to perform a wet die press method in a magnetic field using a rubber mold, and has improved magnetic properties.

Furthermore, magnetic properties of (BH)max 5MGOe could not be obtained in industrial production with ferrite magnets that were conventionally produced in large quantities by the wet method; however, (BH)max
Magnetic properties of ≒4.5 MGOe can be achieved by the die pressing method. By applying the method of the present invention, which brings about a 10% improvement in the properties of the powder, (BH) max = 5 MG
Oe ferrite magnets can be manufactured in industrial production. Currently, 4.5 MGOe ferrite magnets are mass-produced using the usual die pressing method. (BH)max=
Although 4.5 MGOe is close to the limit with the current technology, applying the method of the present invention makes it possible to achieve (BH)max=5MGOe. Since ferrite magnets have a long history, many improvements have already been made, and improvements in (BH)max have reached their limits. The method of the present invention has made a breakthrough in overcoming this limitation. Furthermore, since the slurry can be drained quickly, compression molding can be performed with higher efficiency than in a normal wet method.

According to the present invention which achieves the fourth object, in the process of moving the rubber mold along the circumferential path, (no)
In order to complete operations other than die pressing in a magnetic field,
Productivity is significantly improved compared to conventional methods.

[0165] A rubber mold that achieves the fifth object is very effective against cracks, cracks, deformation, etc. of molded products that occur during powder compaction. Furthermore, if the rubber mold forming the edge portion of the powder compact is chamfered (Claim 38), it is possible to prevent cracks in the edge portion where magnetization tends to remain. Therefore, it is possible to prevent cracking during handling or kicking out by robots in the automated process of compacted powder compacts.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a method for densely filling permanent magnet powder.

FIG. 2 is an explanatory diagram of a method for making a pre-compacted powder body of permanent magnet powder.

FIG. 3 is a diagram of a split rubber mold.

FIG. 4 is a diagram showing an example of a rubber mold.

FIG. 5 is a diagram showing an example of a rubber mold.

FIG. 6 is an explanatory diagram of the shape of a compacted powder body.

FIG. 7 is a diagram showing an example of a rubber mold.

FIG. 8 is an explanatory diagram of an embodiment of a rubber mold for molding an arcuate powder compact.

9 is a cross-sectional view of the rubber mold of FIG. 8. FIG.

FIG. 10 is a diagram of an arcuate powder compact.

FIG. 11 is a diagram showing an example of a rubber mold for forming a square shape.

FIG. 12 is a diagram showing an example of a rubber mold for forming a semicylindrical shape.

FIG. 13 is a diagram showing an example of a rubber mold for molding a pyramid shape.

FIG. 14 is a diagram showing an example of a rubber mold for molding a flat plate with grooves.

FIG. 15 is an explanatory diagram of a rubber mold design method.

FIG. 16 is a diagram of a dry die press apparatus.

FIG. 17 is an explanatory diagram of a method for preventing powder from getting caught.

FIG. 18 is a diagram of a dry die press apparatus.

19 is a partial cross-sectional view of the dry die press apparatus of FIG. 18. FIG.

20 is a diagram illustrating the operation of a cam in the dry die press device of FIG. 18. FIG.

FIG. 21 is an illustration of a method of filling a rubber mold with magnet powder in an inert gas atmosphere.

FIG. 22 is a diagram of a dry die press device using a circular path.

FIG. 23 is a diagram showing an example of a rubber mold.

FIG. 24 is a diagram of a linear transporter.

FIG. 25 is a diagram of a wet molding apparatus.

FIG. 26 is a diagram showing the main parts of a wet molding apparatus (using a ceramic filter) for molding an arcuate powder compact.

27 is an explanatory diagram of each step of the wet molding method of FIG. 25. FIG.

FIG. 28 is an explanatory diagram of the occurrence of burrs.

FIG. 29 is an explanatory diagram of a slurry filling method in a wet molding method.

FIG. 30 is an explanatory diagram of a slurry filling method in a wet molding method.

FIG. 31 is an explanatory diagram of a vacuum treatment method for a rubber mold.

FIG. 32 is an explanatory diagram of a vacuum processing method for a rubber mold.

FIG. 33 is an explanatory diagram of a method of vacuum treating a rubber mold and filling the rubber mold with slurry.

FIG. 34 is an explanatory diagram of a method of forming slurry.

FIG. 35 is a plan view of the wet circulating device.

FIG. 36 is an explanatory diagram of a method for forming a hollow body.

FIG. 37 is a diagram of a rubber mold with a mandrel.

38 is a diagram of a green compact formed by the rubber mold of FIG. 37. FIG.

FIG. 39 is an explanatory diagram of the occurrence of cracks due to wrinkles.

FIG. 40 is an explanatory diagram of the force acting on the rubber mold.

FIG. 41 is a diagram of a rubber mold in which the material and thickness are changed in each part.

FIG. 42 is a diagram of a rubber mold with an open top and bottom.

FIG. 43 is a diagram of a compacted powder body.

FIG. 44 is an explanatory diagram of cracks occurring at the corners of a powder compact.

FIG. 45 is a diagram showing an example of a rubber mold.

FIG. 46 is a diagram of the rubber mold used in Examples 1 to 5.

FIG. 47 is an explanatory diagram of the direction of a magnetic field.

FIG. 48 is a schematic diagram of an apparatus for carrying out a conventional vertical die pressing method.

FIG. 49 is a schematic diagram of an apparatus for carrying out a conventional parallel die pressing method.

FIG. 50 is an explanatory diagram of the occurrence of cracks during compressive deformation of powder using a rubber mold.

[Explanation of symbols]

1a Upper punch 1b Lower punch 2 Die 3 Press plunger 4 Electromagnetic coil 5 Magnetic powder 6 Magnetic pole 10 Rubber mold 30 Magnetic field power supply 31 Hydraulic unit 32 Hydraulic cylinder 34 Filter 40 Conveyor 42 Feeder 45 Feeder 50 Control unit 60　Magnetic field press device 62 Molded object removal device 63　Powder compact 66 Conveyor 70 Pusher 71 Cylinder 75 Fixed cam 76 Hydraulic unit 78 Rubber mold extractor 79 Hollow rod 80 cylinder 81 Hydraulic unit 82 Piston 84 Rubber mold extractor 90 Powder saucer 92 Lid 93 Vacuum chamber 94 Suction port 95 Chamber 100 Guide frame 105 Guide plate 107 Inlet 125 Loading device 128 Loading device 132 Vacuum container 133 Packing 134 Packing 135 Piston 136 Spring 137 color 138 Slurry supply pipe 139 Packing 140 Second conveyor 141 Release plate 142 Stopper 144 Vacuum port 145 Air introduction port 150 Air piston 151 Air unit 152 Electromagnet 153 Electromagnet excitation power supply 157 pusher 158 Cutter 159 Retractable bottom 165 Pump 166 Air unit

Claims (38)

[Claims] 1. A method for producing a permanent magnet, which includes a step of orienting permanent magnet powder in a magnetic field using a die press machine, in which the permanent magnet powder is placed outside the die press machine in a mold having at least a side surface made of rubber and a bottom. Either by applying vibration and/or by pressing with a pusher, the pre-compacted powder of permanent magnet powder is loaded into a rubber mold having at least a rubber side surface and a bottom outside the die press machine, and then The rubber mold filled or loaded with the permanent magnet powder is placed in a die press machine, and the rubber mold and the permanent magnet powder are compressed by a punch of the die press machine to obtain a green compact of the permanent magnet powder. A method of manufacturing permanent magnets. 2. The rubber mold is filled with permanent magnet powder at a high density by the vibration and/or pressing, or the pre-compacted powder is loaded, the upper open part of the rubber mold is covered with a lid, and then the permanent magnetic powder is 2. The production of a permanent magnet according to claim 1, wherein a magnetic field is instantaneously applied to the magnet powder or preform before the magnetic field orientation molding step, or a static magnetic field stronger than the magnetic field orientation molding step is applied. Method. 3. A method for producing a permanent magnet, which includes the step of orienting and forming permanent magnet powder using a die press machine,
Permanent magnet powder is naturally filled outside a die press machine into a mold having at least a rubber side surface and a bottom, and then filled with high density by vibration and/or pressure by a pusher, or by preparing a reserve of permanent magnet powder. The powder compact is loaded into a rubber mold having at least a side surface made of rubber and a bottom outside the die press machine, and then a lid is placed over the open upper part of the rubber mold, and then a magnetic field is applied to the permanent magnet powder or the pre-compact powder. The permanent magnet powder is applied instantaneously, and then the rubber mold filled or loaded with the permanent magnet powder is placed in a die press machine, and the rubber mold and the permanent magnet powder are compressed in the absence of a magnetic field by the punches of the die press machine. A method of manufacturing permanent magnets. 4. A backup plate made of an elastic body harder than the rubber mold is disposed between the rubber mold and at least one of the upper and lower punches, and the backup plate is compressed by the punch. A method for producing a permanent magnet according to any one of items 1 to 3. 5. The permanent magnet according to claim 1, wherein the rubber mold is filled or loaded with rare earth permanent magnet powder or a preform in the presence of an inert gas. Production method. 6. A method for producing a permanent magnet, which comprises sintering the powder compact after the press forming step by the method according to claim 1 . 7. The method for manufacturing a permanent magnet according to claim 1, wherein the rubber mold is filled with resin together with permanent magnet powder. 8. High-density filling into the rubber mold after natural filling of permanent magnet powder into the rubber mold, applying a magnetic field according to claim 2 or 3, die pressing, and taking out the compacted powder from the rubber mold. Claim 2, characterized in that the process is performed repeatedly in sequence on a circular route for conveying the rubber mold.
7. The method for producing a permanent magnet according to any one of items 7 to 7. 9. Loading a pre-compacted powder into a rubber mold;
A method for manufacturing a permanent magnet, characterized in that applying the magnetic field according to claim 2 or 3, die pressing, and removing the compact from the rubber mold are performed repeatedly in a circular path that conveys the rubber mold. 10. The method of manufacturing a permanent magnet according to claim 8, wherein the rubber mold is transported within a circumferential path within an inert gas chamber. 11. The material on at least one of the upper and lower sides of the rubber mold facing the upper and lower punches of the die press machine is
Claims 1 to 10 characterized in that the rubber mold is harder than the rubber on the side facing the die of the die press machine.
The method for producing a permanent magnet according to any one of the preceding items. 12. The permanent magnet according to any one of claims 1 to 11, characterized in that the surface having at least one open opening of a rubber mold whose upper or upper and lower parts are open is directly pressurized with a punch. manufacturing method. 13. The thickness (t, unit: mm) of at least one of the top cover portion and the bottom portion of the rubber mold is expressed by the formula: t
Any one of claims 1 to 12, characterized in that it is expressed as ≦16h/D (where h is the thickness of the green compact and D is the positive square root of the cross-sectional area of the green compact). A method of manufacturing the described permanent magnet. 14. The compacted powder body is a hollow body, and the rubber mold is provided with a mandrel made of a material harder than the rubber mold for forming the hollow part. A method for producing a permanent magnet according to any one of the above. 15. Any one of claims 1 to 14, wherein the rubber mold has a curved portion curved toward the powder side at the end of the inner surface and at least one of the upper surface side and the lower surface side. A method for producing a permanent magnet according to item 1. 16. Compressing permanent magnet powder using a die press machine having an upper punch with water absorption holes and a filter,
A method for manufacturing a permanent magnet including a step of oriented molding a slurry in a magnetic field, in which a slurry of permanent magnet powder is filled in or outside a die press machine, at least a side surface is made of rubber, an upper part is open, and the bottom is made of rubber. The mold is placed in a die press machine, a filter is placed between the upper punch and the open part of the rubber mold, and during the compression, the rubber mold and permanent magnet powder are compressed, and the powder is passed through the filter and the water absorption hole. A method for producing a permanent magnet, which comprises discharging water or solvent in a slurry. 17. The production of a permanent magnet according to claim 16, wherein the rubber mold is filled with the slurry so that the shape of the top surface of the slurry filled in the rubber mold substantially matches the shape of the bottom surface of the upper punch. Method. 18. The method for producing a permanent magnet according to claim 16 or 17, characterized in that a slurry containing an antifoaming agent is used. 19. The method for producing a permanent magnet according to claim 16, wherein the inside of the rubber mold is subjected to vacuum reduction treatment before or after filling the slurry into the rubber mold. 20. The method for producing a permanent magnet according to claim 16, wherein the upper surface of the rubber mold, the upper part of which is open, is directly pressed with a metal punch. 21. From claim 16, wherein the material on the side of the rubber mold facing the lower punch of the die press is harder than the rubber on the side of the rubber mold facing the die of the die press. 20. The method for producing a permanent magnet according to any one of items 19 to 19. 22. The thickness of the bottom of the rubber mold (t
, unit mm) is expressed by the formula: t≦16h/D (where h is the thickness of the compact and D is the positive square root of the cross-sectional area of the compact). 22. The method for producing a permanent magnet according to any one of items 21 to 22. 23. The compacted powder body is a hollow body, and the rubber mold is provided with a mandrel made of a material harder than the rubber mold for forming the hollow part. A method for producing a permanent magnet according to any one of the above. 24. Filling a rubber mold according to the method according to claim 16, compressing according to claim 16, discharging moisture or solvent, and taking out the compacted product from the rubber mold, by moving the rubber mold along a circumferential path. A method for manufacturing a permanent magnet, which is characterized in that the process is repeated in sequence while being conveyed. 25. Filling a rubber mold according to the method according to claim 16, compressing and discharging water or solvent according to claim 16, removing the compact from the rubber mold, and reducing pressure treatment according to claim 19. A method for manufacturing a permanent magnet, characterized in that the steps are sequentially and repeatedly carried out while conveying a rubber mold along a circumferential path. 26. Filling a rubber mold according to the method according to claim 16, reducing the pressure according to claim 19, compressing and discharging water or solvent according to claim 16, and removing the compact from the rubber mold, A method for manufacturing a permanent magnet, characterized in that the steps are sequentially and repeatedly carried out while conveying a rubber mold along a circumferential path. 27. Claims 16 to 2, in which the slurry is replaced with a slurry of a molded product obtained by preforming the slurry.
6. The method for producing a permanent magnet according to any one of items 6 to 6. 28. Any one of claims 16 to 27, wherein the rubber mold has a curved portion curved toward the powder side at the end of the inner surface and at least one of the upper surface side and the lower surface side. A method for producing a permanent magnet according to item 1. 29. Along a path around a rubber mold having at least a side surface made of rubber and a bottom,
Manufacture of a permanent magnet characterized by sequentially arranging a feeder for naturally filling permanent magnet powder into a rubber mold, a pusher or vibrator, a magnetic field generator, a die press, and a jig for taking out the compacted powder from the rubber mold. Device. 30. The permanent magnet manufacturing apparatus according to claim 29, wherein the mold is rotated within an inert gas chamber. 31. Along a path around a rubber mold having at least a side surface made of rubber and a bottom,
1. A permanent magnet manufacturing device, characterized in that a loader for pre-compacted permanent magnet powder, a pulse generator for applying a magnetic field, a die press, and a jig for taking out a green compact from a rubber mold are arranged in sequence. 32. At least the side portion is made of rubber,
A feeder that naturally fills a rubber mold with a slurry of permanent magnet powder along a path that revolves around a rubber mold that has an open top and a bottom, or a loader that loads a slurry molded product into a rubber mold, a die press, and a compacted powder molded product. A permanent magnet manufacturing device characterized by sequentially arranging jigs for taking out magnets from a rubber mold. 33. At least the side portion is made of rubber,
A feeder that naturally fills the rubber mold with slurry of permanent magnet powder or a loader that loads the slurry molded body into the rubber mold, a die press, and a compacted powder body are used along the path that circulates around the rubber mold that has an open top and a bottom. A permanent magnet manufacturing device characterized by sequentially arranging a jig for taking out a rubber mold and a pump for depressurizing the rubber mold. 34. At least the side portion is made of rubber,
A feeder that naturally fills a slurry of permanent magnet powder into a rubber mold along a path that revolves around a rubber mold that is open at the top and has a bottom, or a loader that loads a slurry molded body into the rubber mold, and the inner surface of the rubber mold is subjected to vacuum treatment. A permanent magnet manufacturing device characterized by sequentially arranging a pump, a die press, and a jig for taking out a compacted powder from a rubber mold. 35. At least the side portion is made of rubber, and the material of at least one of the top cover portion and the bottom portion of the rubber mold is harder than the rubber on the side of the rubber mold facing the die of the die press machine. Rubber mold for manufacturing compacted powder of permanent magnets. 36. At least the side portion is made of rubber,
The thickness (t) of at least one of the top cover or the bottom of the rubber mold is expressed by the formula: t≦16h/D (where h is the thickness of the compact and D is the positive square root of the cross-sectional area of the compact). A rubber mold for producing a powder compact of a permanent magnet, characterized by the following: 37. The permanent mold according to claim 35 or 36, wherein the powder compact is a hollow body, and the rubber mold is provided with a mandrel made of a harder material than the rubber mold for forming the hollow part. Rubber mold for magnet production. 38. The rubber mold according to any one of claims 35 to 37, wherein the rubber mold has a curved portion curved toward the powder side at the end of the inner surface and at least one of the upper surface side and the lower surface side. Rubber mold for producing compacted powder of the described permanent magnet.