JPH0612728B2 - Manufacturing method of cylindrical radial anisotropic permanent magnet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a cylindrical radial anisotropic permanent magnet oriented so as to have anisotropy in the radial direction.

[Prior Art] As a permanent magnet for a small motor such as a stepping motor, a cylindrical isotropic permanent magnet magnetized with multiple poles has been conventionally used. However, in recent years, there has been an increasing demand for magnets having a strong magnetic force, and therefore, the practical application of radial anisotropic magnets in which magnet powder is radially oriented is strongly desired.

However, as described in JP-A-56-33934, in the case of a ferrite magnet, the magnetic powder can be oriented in the radial direction by applying a radial magnetic field of about 7 KOe. If
Since the magnetic powder has a high coercive force, it cannot be sufficiently oriented in a low magnetic field, and even if an attempt is made to apply a strong radial magnetic field, the applied magnetic field will be saturated and there is a problem that a strong magnetic field cannot be applied. is doing.

In the present invention, the radial anisotropic magnet refers to a permanent magnet in which the orientation of the magnetic particles is the radial direction as shown by the arrow, as shown in FIG. In addition, the direction of the arrow may be opposite to that in the figure.

FIG. 2 shows an example of a conventional cylindrical radial anisotropic magnet molding method. The basic structure is composed of an upper coil 1, a lower coil 2, an upper magnetic core 3, a lower magnetic core 4, an upper punch 5, a lower punch 6, dies 7, 8 and a cavity 9. The molding process will be briefly described. First, the magnetic powder is uniformly charged into the cavity 9. Next, the upper punch 5 is lowered to a position where magnetic particles do not come out of the cavity even when a magnetic field is applied.
Then, a direct current is passed through the upper coil and the lower coil to excite the upper magnetic core 3 and the lower magnetic core 4. The polarities are such that the opposite surfaces of 3 and 4 have the same magnetic pole. The current is then increased until 3 and 4 are magnetically saturated. Some of the generated magnetic force lines are modeled by arrows and N. The lines of magnetic force emitted from the upper and lower sides collide with each other on opposing surfaces and become horizontal to pass through the cavity 9 to orient the magnetic particles in the radial direction. In this state, one or both of the upper punch 5 and the lower punch 6 are moved to perform press molding. Thus, the green body of the radial anisotropic magnet is obtained. In this state, the polarity of the coil current is reversed to demagnetize and take out from the mold. The green body is then sintered or cured into a magnet.

However, in such a conventional method, the magnetic field lines are
And the lower magnetic core 4, and most of them are diffused into the atmosphere having a magnetic permeability of 1 and weakened, so that a strong magnetic field cannot be applied to the magnetic powder, and the height and thickness of the cavity (that is, the cylindrical magnet). If the difference between the outer diameter and the inner diameter of (1) becomes large, a parallel magnetic field cannot be obtained in the cavity, and uniform magnetic powder orientation cannot be obtained.

The inventor of the present invention is the same as Japanese Patent Application No. 56-72597
7-187914), a method for improving the above-mentioned conventional method is proposed. The method will be briefly described with reference to FIG. The magnetic lines of force generated in the coil 1 flow horizontally and radially from the die 5 to the die 8. Therefore, the magnetic force lines run in the cavity 15 (spotting portion) in the radial direction and have a distribution as shown in FIG. A magnetic powder is charged in the cavity 15 and pressed by the punches 11 and 13 to form a radial anisotropic magnet. This method produces industrially practical radial anisotropic magnets at low cost, but the greater the strength of the orienting magnetic field, the more the radial anisotropic magnet with the magnetic performance close to that of magnetic powder can be produced. The demand for increasing the strength of the orientation magnetic field is strong from the magnet manufacturing side.

However, even with the method of FIG. 3, as shown in Table 1, depending on the size of the cavity, only a magnetic field of about 4 to 5 KOe can be applied, so that the above requirements cannot be sufficiently satisfied.

[Problems to be Solved by the Invention] As described above, according to the conventional technique, there is a drawback that the orientation magnetic field in the radial direction is nonuniform or low.

Then, this invention solves such a problem, and it aims at providing the method of manufacturing by raising the shaping | molding magnetic field of a radial anisotropic magnet.

[Means for Solving the Problems] The present invention is characterized in that the conventional repulsive magnetic field method is provided with a third magnetic pole, and is combined with a dimension of a cavity capable of applying a sufficiently strong magnetic field even in a radial magnetic field. And

[Operation] The strength of the orientation magnetic field has been found to be better from both theoretical and experimental points of view. More specifically, The degree of orientation changes depending on the magnitude of the coercive force of the magnetic powder as well as the strength of the magnetic field. The degree of orientation of the magnetic powder directly affects the performance of the magnet. When the coercive force of the magnetic powder is 4 KOe or less, the orientation magnetic field strength is 8 KOe and a magnetic performance of about 90% is obtained. A magnetic powder having a coercive force exceeding 4 KOe can achieve 90% magnetic performance by adding twice the amount of the coercive force exceeding 4 KOe to the orientation magnetic field of 8 KOe. From a practical point of view, the strength of the orientation magnetic field is at least 8 KOe
is necessary.

As is clear from FIG. 5, the strength of the orientation magnetic field is the ratio (Φ / S) of the total magnetic flux (Φ) passing through the dies 6 and 10 to the contact area (S) of the die 12 and the cavity 20. ). It can be seen from Table 1 given at the end of the sentence that the larger the ratio, the larger the orientation magnetic field.

If the outer diameter of the cavity is defined as Dout, the inner diameter is defined as Din, and the height is defined as t, and the magnetic flux density passing through a unit area of the inner diameter is standardized as 1, the total magnetic flux (Φ) is proportional to the cross-sectional area of the inner diameter π ×
^(Din) 2/4. On the other hand die 12 and the area of the cavity 20 contacts (S) is π × Dout × t becomes, the ratio (Φ / S) is used as a size factor of the cavity ^{(Din) 2} It is expressed by the formula: / (4 × Dout × t).

Therefore, if the thickness of the cylindrical magnet is reduced and the inner diameter is increased, the dimensional coefficient of the cavity can be increased.

On the other hand, from the magnetic theory, the magnitude of the demagnetizing field of the magnet is inversely proportional to the square of the magnetic pole interval (corresponding to the thickness of the magnet in the magnetization direction).

Since the alnico magnet has a low coercive force of about 1 KOe, when the thickness of the magnet is set to 1 to 2 mm, it is canceled by the demagnetizing field and the magnetomotive force becomes so small that it cannot be put to practical use. On the other hand, a magnet having a large coercive force of 4 KOe or more has a coercive force effect even though it is thinned to a thickness of 1 to 2 mm even though it is canceled by the demagnetizing field, and the magnetomotive force is of a size that can be put to practical use. Owns.

Thus, according to the present invention, the magnetic material has a coercive force of 4 KO.
Experiments based on the novel theory that a radial anisotropic magnet that can be put to practical use can be supplied for the first time by adopting a material of e or higher and setting the size factor of the cavity above a certain value. It was confirmed in.

[Examples] The present invention will be specifically described in detail with reference to Examples.

FIG. 4 is a sectional view of an example of a method for forming a three-pole type radial anisotropic magnet according to the present invention.

The magnetic force lines generated from the upper coil 1 are transmitted to the dies 5 and 6 through the upper magnetic core 4. Similarly, the magnetic lines of force generated from the lower coil 2 are transmitted to the dice 9 and 10 through the lower magnetic core 8. The dies 5 and 6 are mechanically fixed to or integrally formed with the magnetic core 4, and similarly the dies 9 and 10 are mechanically fixed to or integrally formed with the magnetic core 8.
The horizontal cross section of the dice 5, 6, 9, 10 is a circle. Further, the horizontal cross section of the punches 15, 16, 17, 18 is a ring. The middle coil 3 is coupled to a middle magnetic core 11 located between the upper magnetic core 4 and the lower magnetic core 8, and the dice 12, 13 are attached to the middle magnetic core 11.
Are mechanically fixed or integrally formed. Further, the die 13 is mechanically fixed to or integrally formed with the lower magnetic core. The magnetic force lines generated from the upper coil 1 pass through the upper magnetic core 4, the dice 5 and 6, pass through the cavities 19 and 20, pass through the dice 12 and 13, and reach the middle magnetic core 11.
The line of magnetic force generated in the lower coil 2 is also 8 → (9,10).
→ (19, 20) → (12, 13) → 11 That is, the upper magnetic core 4, the lower magnetic core 8 and the middle magnetic core 12 are magnetically coupled by the constituent elements of the magnetic circuit, whereby the magnetic field is induced in the cavity. When the upper coil 1 has an N pole downward, the lower coil 2 has an N pole upward, and the middle coil 3 has an S pole upward, a flow of the above magnetic force lines results in the cavities 19 and 20 (dotted portions). The magnetic powder charged in the is oriented in a radial shape. Punches 15, 16, 17, 18 in the oriented state
And press-mold. The polarity of the coil current is reversed and demagnetized to create a green body of radial anisotropic magnet.
This is sintered and cured into a magnet. In these figures, one magnetic pole of each of the coils 1, 2 and 3 is open, but if left open, magnetic leakage will be large, which is not preferable.

Referring to FIG. 5 (AA 'cross section in FIG. 4), the upper coil 1, the lower coil 2, the middle coil 3, the upper magnetic core 4, the lower magnetic core 8, the middle magnetic core 11, the dies 6, 10, 12, punches 16, 18 are shown. ,
The cavity 20 is formed, and the flow of the magnetic force lines is shown by arrows as a model, and the magnetic force lines flow from the magnetic cores 4, 8 to the dies 6, 10 and are radially distributed in the cavity 20. In the figure, the parts without numbers are made of non-magnetic material or space.

One of the magnetic poles of the coils 1 and 2 is idle. This magnetic pole can be replaced with the coil 3. In this case, since a magnetic circuit is assembled from the coil 1 to bring the magnetic force lines to the middle magnetic core 11, magnetic leakage in the middle is large, and the total magnetic flux amount to be excited in the middle magnetic core 11 may be insufficient. In this case, it is necessary to excite the coils 1 and 2 more strongly or use the medium coil 3 as an auxiliary.

4 and 5 show a model of one example of the present invention, and the dimensional relationship is not the actual size. It can be easily understood from FIGS. 4 and 5 that the multi-cavity can be constructed by arranging the single-cavity molds in a plane.

The thickness of the magnetic cores 4, 8 and 11 must be 5 cm or more for practical use.
It is preferably 10 cm or more. This is because when the generated magnetic field is high, the magnetic gradient becomes too large when the thickness is thin. The punches 16 and 18 are made of a non-magnetic material having good wear resistance (stellite, cemented carbide). The magnetic cores 4, 8 and 11 require high saturation magnetic flux density (4πIs) and high magnetic permeability (μ).
An e-Co alloy and pure iron are used. Dice 6, 10, 1
No. 2 requires high wear resistance, high 4πIs, and high μ. There is currently no material that satisfies all of these required characteristics. Therefore, a part or the whole is made of hardened steel (SK, SKD, SKJ, SKS). If further abrasion resistance is required, surface hardening treatment is applied to these, or partially stellite or cemented carbide is used. Surface hardening is a commonly used method, and nitriding, stellite, cemented carbide overlaying or the like is effective.

Table 1 shows the results of actually measuring the strength of the magnetic field generated in the cavity by this method. The exciting current is 10 amps for the coils 1 and 2 and 20 amps for the coil 3. Again 2
As a result of performing the same measurement with 10 multi-piece type, the same value was obtained in the measurement error range as in Table 1.

In the method of the present invention, when Φ / S is 0.27 or more, 8KO
It can be seen from Table 1 that a radial orientation magnetic field of e or more can be obtained. The radial magnetic field generated in the cavity becomes saturated when Φ / S is around 0.8 to about 15 KOe because the magnetic material forming the die has a saturation magnetic flux density. , It becomes larger as the shape of the cavity is changed and Φ / S is increased.

From Table 1, the strength of the magnetic field generated by the three-pole method according to the present invention is approximately twice that of the two-pole method.

As can be seen from Table 1, there is a limit of 8 KOe, which is the lower limit of the required strength of the orientation magnetic field, depending on the size of the cavity. The present inventor has invented a method for forming a radial anisotropic magnet in this size range by increasing the degree of orientation, as an application example of the present invention. They are: Partial orientation press method 2. Orientation / press separation method.

The total magnetic flux passing through the die changes the material of the die and is high 4π.
The use of Is material slightly improves the ratio, but the ratio is not large. However, dice 6 and 8 and cavity 20
The area of the surface directly contacting with can be reduced in inverse proportion to the number of presses. That is, by dividing the radial anisotropic magnet and striking it multiple times, the magnitude of the magnetic field generated in the cavity can be roughly doubled.

The partial orientation method, which is an application of the present invention, will be described below.

One of the partially oriented pressing methods is a method in which the height direction of the radial anisotropic magnet is divided into two or more and the height directions are stacked.

Further, it will be specifically described with reference to FIG. When the cavity size is φ30 × φ26 × t20 mm, the height of the cylindrical radial anisotropic magnet, which is a molded product after pressing, is 8 mm. Since the magnetic powder has a low density, when it is pressed under pressure, the height is compressed from 20 mm to 8 mm to 1 / 2.5 and solidifies. To strike a cylindrical radial anisotropic magnet of this size, namely φ30 × φ26 × t8 mm, twice, a cavity of φ30 × φ26 × t10 mm is used. The height of the first magnetic powder is 10
It is filled in a cavity having a size of mm, and magnetic powder is pressed to 1 / 2.5 to form a molded product having a height of 4 mm in a magnetic field. After demagnetizing by reversing the polarity of the exciting current flowing through the coil, punch 1
6 and 18 are fixed and the magnetic core 11 connected to the die 12 is raised by 4 mm, and then the punch 16 is raised. The cavity 20 is emptied and filled with the second magnetic powder,
Repeat the same as the first time. With this, φ30
In the present invention, it was possible to strike a radial anisotropic magnet of × φ26 × t8 mm, which had an orientation magnetic field of 8 KOe by the above-mentioned ordinary single-strike method, by 13 KOe in the present invention. Similarly, if a die with a height of 5 mm for the cavity 20 is used, the magnetic powder similarly filled in the cavity is compressed to 1 / 2.5, and a molded product with a height of 2 mm is obtained by one molding, When the pressing was performed four times, a radial anisotropic magnet of φ30 × φ26 × t8 mm could be molded with a highly oriented magnetic field of 15 KOe. The above embodiment is one example of the application of the present invention, but radial anisotropic magnets of all shapes could be formed with a high orientation magnetic field by these partially oriented breathing methods.

The next partial orientation press method is a method of dividing the cavity into a certain angle.

The die 12 is divided at a certain angle with the magnetic core 4 (or 8) as the center, and the one divided portion is made of a ferromagnetic material, and the remaining divided portion is made of a non-magnetic material. It is made of a material, and magnetic particles are magnetically oriented and pressed for each division by performing the division times.
As a result, it was possible to perform the alignment with an alignment magnetic field that is a multiple of the division number as compared with the 360 ° collective alignment.

The third partial orientation pressing method is a method in which the cavity is divided in the radial direction and press-molded.

Regarding the strength of the orientation magnetic field, as can be seen from Table 1, the orientation magnetic field sharply decreases as the thickness increases. As an example, the cavity dimensions are φ20 × φ18 × t5mm, φ20 × φ16 ×
At t5 mm, they are 15 KOe and 11 KOe, respectively. This is because the total magnetic flux is proportional to the square of the inner diameter of the cavity and the magnetic resistance is proportional to the thickness of the cavity. Conversely, the orientation magnetic field can be increased by reducing the thickness of the cavity space.

Therefore, in the third partially oriented pressing method, which is one of the application examples of the present invention, the outer diameter and the inner diameter are divided into two or more to form a thin radial anisotropic magnet with a high orientation magnetic field. , A method of combining molded products to form a predetermined shape.

Next, the magnetic field orientation / press separation method will be specifically described.

The magnetic field orientation / press separation method is a method in which the magnetic field orientation of the magnetic particles filled in the cavity and the pressure press are temporally independent. That is, to explain one example in FIG. 5, the side surface of the die 12 facing the cavity 20 is divided in the height direction to reduce the surface area of the high magnetic permeability (high μ) material. The high magnetic permeability material part is sandwiched between the upper and lower parts by the non-magnetic material. The upper punch 16 is lowered to a position where magnetic particles do not jump out of the cavity 20. In this state, the magnetic powder is not pressed. Next, a current is applied to the coils 1 and 2 to move the die 12 up and down to partially orient the magnetic particles. In order to enhance the orientation of the magnetic powder, the coil current is reversed and the forward and reverse orientations are repeated. In this way, high-field radial orientation can be achieved. Thereafter, press molding is performed by the same method as described above. Further, the oriented magnetic particles form a magnetic circuit between the magnetic particles when the magnetic field is set to 0 Oe, so that the magnetic particles rotate by themselves and the orientation in the cavity deteriorates. Therefore, it is preferable to press with some residual magnetism in part or all of 4, 6, 8, and 10. Further, the die 12 and the magnetic powder may be put in the sleeve without directly contacting each other.

The method according to the present invention makes it possible to supply radial anisotropic magnets with high productivity and low cost as shown in Table 2, but representative values for magnetic performance are shown in Table 3. On the street. Table 3 shows, for example, Japanese Patent Publication No. 53-3233.
As shown in Example 1 of Japanese Unexamined Patent Publication (Kokai) No. 0, a mixture of SmCo ₅ magnetic powder, which is a typical composition of rare earth cobalt magnets, with an epoxy adhesive added at about 0.5 wt% is mixed and molded by the method of the present invention. The magnetic performance is shown when the test is performed, and both are extremely excellent as compared with the isotropic property.

In the present invention, the non-magnetic material means a material having μ of about 1. Although the polarities are limited in the description, both the N pole and the S pole are exchangeable.

The present invention relates to a method of forming a radial anisotropic magnet having a high coercive force, and it is clear that the magnetic coercive force limits the magnetism and is not particularly limited depending on the material of the magnet. , Alnico magnet, Fe
It can be applied to any of -Cr-Co spinodal decomposition magnets, Mn-Al magnets, Mn-Bi magnets, ferrite magnets, and Fe shape anisotropic magnets. In particular, a remarkable effect is obtained when applied to a rare earth cobalt-based magnet having a high coercive force.

Rare earth cobalt magnets are rare earth elements (Y, La, Ce, Pr, N
d, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) and transition elements containing cobalt (Co, Fe, Ni, Cu, Mn, Cr, V, Ti, Zn, Cd, Ag) , Pd, Rh, Ru, M
o, Nb, Zr, Au, Pt, Ir, Os, Re, W, Ta, Hf) and small amount of metal, semimetal / nonmetal (B, C, Be, Al, Si, P, Ge, Ga, In) , Sn, Sb, Bi, Pb), and the crystal system includes a hexagonal system and a cubic system.

Alnico magnets and Fe-Cr-Co spinodal decomposition magnets are powder magnets.

The Mn-Al magnet also contains a third element and additional elements of a higher kind, and the Mn-Al-C system also belongs to the present invention. Ferrite magnets include, in addition to Ba ferrite and Sr ferrite, Co-modified magnets. The iron-shaped anisotropic magnet also includes an alloy containing Co in Fe.

The magnet may be manufactured by any of a sintering method, a metal bonding method, a resin bonding method, and an inorganic bonding method.

In the present invention, the cylindrical radial anisotropic permanent magnet refers to a cylindrical permanent magnet in which the orientation of the magnetic particles is the radial direction as shown by the arrow, as shown in FIG. In addition, the direction of the arrow may be opposite to that in the figure. In special cases, the bottom surface and the top surface may have different shapes. Radial lines of magnetic force are emitted in a radial direction from a curved surface in any shape, thereby orienting the magnetic powder,
A magnetic field is formed. The application of the present invention includes an elliptic cylinder, a rectangular cylinder, and the like.

[Advantages of the Invention] As described above, according to the present invention, by improving the magnetic circuit and limiting the relationship between the inner diameter, the outer diameter, and the height of the cavity, the radial anisotropy with a coercive force of 4 KOe or more is obtained. A radial orientation magnetic field of 8 KOe or more, which is necessary for manufacturing a magnet, can be applied to the magnetic powder.

Also, the magnetic field forming processing cost is shown in Table 2 when indexing 1 piece (the number of pieces produced per press is 1) as shown in Table 2, and with 10 pieces, the processing cost is reduced to 15% of the single piece. I was able to do it.

The magnet manufactured according to the present invention is extremely effective for miniaturization and high performance of control motors, speakers, magnetic bearings, traveling wave tubes, and the like, and has high industrial practical value.

[Brief description of drawings]

FIG. 1 is a diagram showing the orientation of magnetic powder of a cylindrical radial anisotropic permanent magnet. FIG. 2 is a partial sectional view of a conventional magnetic field repulsion type cylindrical radial anisotropic permanent magnet manufacturing apparatus. 1 ... Upper coil, 2 ... Lower coil 3 ... Upper magnetic core, 4 ... Lower magnetic core 5 ... Upper punch, 6 ... Lower punch 7,8 ... Die, 9 ... Cavity Sectional view of a part of the yoke type cylindrical radial anisotropic permanent magnet manufacturing apparatus of FIG. 1 ... Upper coil, 2 ... Lower coil 3 ... Upper magnetic core, 6 ... Lower magnetic core 5,8 ... Die, 11 ... Upper punch 13 ... Lower punch, 15 ... Cavity Sectional drawing of a part of apparatus used for the cylindrical radial anisotropic permanent magnet manufacturing method which becomes invention. 1 ... Upper coil, 2 ... Lower coil 3 ... Medium coil, 4 ... Upper magnetic core 8 ... Lower magnetic core, 11 ... Medium magnetic core 5,6,9,10,12,13 ... Dice 15,16 ... upper punch, 17, 18 ... lower punch 19, 20 ... cavity Fig. 5 is a cross section taken along the line AA 'in Fig. 4.

Claims (1)

[Claims] 1. A first magnetic pole is formed on an upper part of an upper magnetic core and a lower part of a lower magnetic core by a magnetic field generated by two coils arranged above and below a die formed of a high magnetic permeability material. A second magnetic pole is formed on a lower portion of the upper magnetic core and an upper portion of the lower magnetic core, and a first magnetic pole is formed at a portion adjacent to the die of an intermediate magnetic core arranged so as to surround a horizontal periphery of the die. A magnetic pole is formed and a second magnetic pole is formed at a position distant from the adjacent portion, and a magnetic field substantially induced in the horizontal direction by the interaction between the upper magnetic core, the lower magnetic core, and the intermediate magnetic core is substantially formed. Inner diameter (Din), outer diameter (Dout), and height (t) of a cylindrical cavity whose spatial shape is applied
And a coercive force (iHc) of 4K was applied to a molding die satisfying the relationship of (Din) ² /(4×Dout×t)≧0.27.
Manufacture of a cylindrical radial anisotropic permanent magnet characterized in that it is filled with Oe or more magnet powder, a radial radial magnetic field is applied to the cavity, the magnet powder is magnetically oriented, and pressure-molded. Method.