JP3639584B1 - Magnetic field orientation molding device and orientation magnetic field generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alignment magnetic field forming apparatus capable of uniformly generating a high alignment magnetic field without changing the interval between pole pieces and without significantly changing the configuration of the alignment magnetic field forming apparatus.
SOLUTION: Upper and lower punches 2 and 3 arranged opposite to each other, a die 4 that forms a cavity 9 for accommodating a powder to be molded together with upper and lower punches 2 and 3, and press-molds the powder to be molded; Pole pieces 5 and 6 disposed opposite to each other and excitation coils 7 and 8 disposed on each of the pole pieces 5 and 6, and a magnetic field in a direction orthogonal to the direction of pressure molding is accommodated in the cavity 9. And an orientation magnetic field generator to be applied to the powder to be molded. The pole pieces 5 and 6 are connected to the cylindrical portions 5a and 6a having the same cross-sectional area in the direction of the magnetic field and the cylindrical portions 5a and 6a, and the cross-sectional areas thereof are smaller than the cylindrical portions 5a and 6a and face the die 4. And the exciting coils 7 and 8 are disposed over the cylindrical portions 5a and 6a and the truncated cone portions 5b and 6b.
[Selection] Figure 1

Description

  The present invention relates to a magnetic field orientation molding apparatus that applies pressure to a magnetic powder while applying a magnetic field to perform orientation, and more particularly to a magnetic field orientation molding apparatus that applies a magnetic field in a direction perpendicular to the pressure direction.

A rare earth sintered magnet pulverizes a raw material alloy to a predetermined particle size, applies a magnetic field to the pulverized fine powder and orients it while pressing to produce a compact. It is manufactured through the basic process of sintering the compact.
There are two methods for performing molding in a magnetic field depending on the relationship between the pressurizing direction and the application direction of the magnetic field. One is vertical magnetic field shaping (for example, Patent Document 1) in which a magnetic field parallel to the pressurizing direction is applied, and the other is a magnetic field perpendicular to the pressurizing direction as shown in FIG. This is the transverse magnetic field shaping to be applied (for example, Patent Document 2). As shown in FIG. 7, the magnetic field orientation molding apparatus 31 in the transverse magnetic field molding has a pair of upper punch 32 and lower punch 33 that are arranged to face each other. The upper punch 32 and the lower punch 33 are disposed so as to advance and retract in the vertical direction by a hydraulic device (not shown). The magnetic field orientation molding apparatus 31 includes a die 34 for forming a cavity 39 for accommodating the rare earth-iron alloy powder together with the upper punch 32 and the lower punch 33 and for pressure molding the rare earth-iron alloy powder.
A pair of pole pieces 35 and 36 are arranged opposite to each other with the die 34 interposed therebetween, and excitation coils 37 and 38 are arranged on the pole pieces 35 and 36, respectively. The pole piece 35 includes a cylindrical part 35a and a truncated cone part 35b connected to the cylindrical part 35a. Similarly, the pole piece 36 includes a cylindrical portion 36a and a truncated cone portion 36b connected thereto.

  Longitudinal magnetic field shaping is mainly applied to the production of flat magnets, and transverse magnetic field shaping is mainly applied to the production of block magnets. Compared with longitudinal magnetic field shaping, transverse magnetic field shaping can obtain a higher degree of orientation. And the magnetic characteristic of the permanent magnet after sintering can be improved by obtaining a high degree of orientation at the time of shaping | molding.

Japanese Utility Model Publication No. 6-79134 JP-A-6-116603 JP 2001-28314 A

It goes without saying that a magnet with high magnetic properties can be obtained by obtaining a higher degree of orientation in transverse magnetic field shaping. In order to obtain a high degree of orientation, a high orientation magnetic field may be realized. For this purpose, the power supply of the magnetic field orientation molding device may be set to a high output, but the change of the device configuration becomes significant.
As another method, it is possible to obtain a high orientation magnetic field by narrowing the interval between pole pieces provided with excitation coils for generating a magnetic field. Narrowing the gap between the pole pieces places a limit on the volume of the cavity filled with the magnet powder, so that only a limited number of compacts can be obtained, or only a limited number of compacts can be molded at one time. The problem that it cannot be obtained arises.
Further, Patent Document 3 proposes that a correction pole piece is provided in the vicinity of a die constituting the magnetic field orientation molding device to obtain a uniform orientation magnetic field in a cavity in the die. However, the installation of the correction pole piece is undesirable because it leads to an increase in the number of components of the oriented magnetic field forming apparatus.

  The present invention has been made on the basis of such a technical problem, and it is possible to uniformly achieve a high orientation magnetic field without changing the interval between the pole pieces and without significantly changing the configuration of the orientation magnetic field forming apparatus. An object of the present invention is to provide an orientation magnetic field forming apparatus that can be generated.

  An orientation magnetic field forming apparatus according to the present invention includes a pair of punches arranged opposite to each other, a die for forming a cavity for containing the powder to be molded together with the pair of punches, and a die for pressure-molding the powder to be molded. A pair of pole pieces disposed opposite to each other and an excitation coil disposed on each of the pair of pole pieces, and applying a magnetic field in a direction orthogonal to the direction of pressure molding to the powder to be molded accommodated in the cavity An orientation magnetic field magnetic field generator. The pole piece has an equal cross-sectional area portion whose cross-sectional area is equal in the direction of the magnetic field, and a cross-sectional area reduction portion which is connected to the equal cross-sectional area portion and whose cross-sectional area is smaller than the equal cross-sectional area portion and faces the die. The excitation coil is attached over the equal cross-sectional area part and the cross-sectional area decreasing part.

In the orientation magnetic field forming apparatus of the present invention, the excitation coil is disposed in the entire region along the direction of the magnetic field in the equal cross-sectional area portion, and is disposed in the entire region or a part in the direction of the magnetic field in the cross-sectional area decreasing portion. Can be made. Further, the exciting coil may be disposed with a magnetic gap formed between it and the cross-sectional area reducing portion, or may be disposed without forming the gap.
In the oriented magnetic field shaping apparatus of the present invention, the pole piece has a configuration in which the connecting portion of the equal cross-sectional area portion and the cross-sectional area reducing portion has the same cross-sectional area, and the cross-sectional area reducing portion continuously decreases in cross-sectional area. be able to. In particular, in order to obtain a high orientation magnetic field, it is preferable that the equal cross-sectional area portion is formed of a cylindrical member and the cross-sectional area reduction portion is formed of a truncated cone-shaped member.

The inventors of the present invention have disclosed a pole piece having a cylindrical base portion and a truncated cone portion that is continuous with the base portion, the cross-sectional area of which decreases toward the magnetic field die, and the front end surface of which faces the cavity die. When the diameter of the tip surface of the truncated cone portion is c, it has been found that there is a difference in the magnetic field intensity generated depending on the value of c / d. Therefore, the present invention provides a pair of punches arranged opposite to each other, a die that forms a cavity for containing the powder to be molded together with the pair of punches, and press-molds the powder to be molded together with the pair of punches, An orientation having a pair of pole pieces arranged opposite to each other and an excitation coil arranged on each of the pair of pole pieces, and applying a magnetic field in a direction perpendicular to the direction of pressure molding to the powder to be molded contained in the cavity A magnetic field generator, and an excitation coil is provided across the base and the truncated cone, and c / d is 0.2 to 0.8, preferably 0.3 to 0.6. It is proposed to set the range.

The present invention can also be understood as an orientation magnetic field generator that constitutes a magnetic field orientation molding device. This orientation magnetic field generator applies a magnetic field in a direction perpendicular to the pressurizing direction to magnetic powder that has been press-molded. An excitation coil that generates a magnetic flux when energized, and an excitation A pole piece for supplying the magnetic flux generated by the coil toward the magnetic powder, the pole piece converging the magnetic flux passing through the base toward the magnetic powder and converging the magnetic flux passing through the base to the magnetic powder And a converging part that exits from the surface. When the distance in the magnetic flux passage direction from the front end surface of the converging portion to the base portion is a and the distance in the magnetic flux passage direction from the front end surface of the converging portion to the exciting coil is b, a−b> 0. It is a feature.
In this orientation magnetic field generator, when the base is composed of a cylindrical member and the converging portion is a truncated cone-shaped member, assuming that the diameter of the base is d and the diameter of the distal end surface of the converging portion is c, c / d is 0.2. It is desirable to set it to -0.6.

  According to the present invention, the conventional oriented magnetic field forming apparatus has the exciting coil disposed only in the equal cross-sectional area portion, whereas the present invention is disposed over the equal cross-sectional area portion and the cross-sectional area decreasing portion. As a result, the strength of the magnetic field applied to the cavity can be improved and made uniform.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
FIG. 1 is a front sectional view showing a schematic configuration of a magnetic field orientation molding apparatus 1 in the present embodiment.
The magnetic field orientation molding apparatus 1 has a pair of upper punch 2 and lower punch 3 that are arranged to face each other. The upper punch 2 and the lower punch 3 are arranged so as to advance and retract in the vertical direction by a hydraulic device (not shown). The magnetic field orientation molding device 1 includes a die 9 for forming a cavity 9 for accommodating a rare earth-iron alloy powder as a powder to be molded together with the upper punch 2 and the lower punch 3 and press-molding the rare earth-iron alloy powder. Yes.
A pair of pole pieces 5, 6 are arranged opposite to each other with the die 4 interposed therebetween, and excitation coils 7, 8 are arranged on each of the pole pieces 5, 6. The pole piece 5 includes a cylindrical portion 5a and a truncated cone portion 5b connected to the column portion 5a. Similarly, the pole piece 6 includes a cylindrical portion 6a and a truncated cone portion 6b connected to the column portion 6a. The cylindrical portions 5a and 6a have the same cross-sectional area in the direction of the magnetic field. The truncated cone parts 5b and 6b are arranged so that the cross-sectional area thereof is smaller than that of the columnar parts 5a and 6a and faces the die 4 except for the connecting parts. The cylindrical portions 5a and 6a and the truncated cone portions 5b and 6b have the same cross-sectional area at their connection portions, but the truncated cone portions 5b and 6b continuously decrease in cross-sectional area.

A magnetic field (magnetic flux) generated by energizing the exciting coil 7 passes through a path of the pole piece 5 (or 6) die 4, the cavity 9, the die 4 and the pole piece 6 (or 5). This path, that is, the direction H of the magnetic field is orthogonal to the pressure forming direction P as shown in FIG. In the pole piece 5 (or 6), the magnetic flux passes substantially parallel in the cylindrical portion 5a (6a) having a constant cross-sectional area, but in the truncated cone portion 5b (6b) in which the cross-sectional area decreases toward the die 4. Focusing toward the rare earth-iron alloy powder housed in the cavity 9.
Each of the above components is disposed in a housing 10 made of a magnetic material.

The magnetic field orientation molding apparatus 1 according to the present invention is characterized by the positional relationship between the pole pieces 5 and 6 and the exciting coils 7 and 8. As shown in FIG. 7, the conventional magnetic field orientation molding apparatus 31 is disposed only around the cylindrical portions 35 a and 36 a of the pole pieces 35 and 36.
However, in the magnetic field orientation molding apparatus 1 according to the present invention, as shown in FIG. 1, the excitation coil 7 extends from the cylindrical portion 5 a of the pole piece 5 toward the truncated cone portion 5 b, and the excitation coil 8 is connected to the pole piece 6. The cylindrical portion 6a extends toward the truncated cone portion 6b. Thus, the exciting coils 7 and 8 are extended and arranged across the columnar part 5a and the truncated cone part 5b, and the columnar part 6a and the truncated cone part 6b, so that the interval between the pole pieces 5 and 6 is not reduced. The orientation magnetic field in the cavity 9 can be improved and made uniform.

Here, as shown in FIG. 3, the distance (direction in which the magnetic flux passes) of the truncated cone part 5b (6b) of the pole piece 5 (6) is a, and the truncated cone part 5b (6b) of the pole piece 5 (6). ) Side end surface of the magnetic pole surface 5c (6c) to the exciting coil 7 (8), where b is the magnetic flux orientation forming apparatus 1 according to the present invention, ab> 0. Thus, the exciting coil 7 (8) is arranged. As shown in the examples described later, since the magnetic flux density in the cavity 9 varies depending on the value of ab, it is desirable to set the value of ab appropriately in order to generate a high orientation magnetic field.
Further, as shown in FIG. 3, when the diameter of the magnetic pole surface 5c (6c) is c and the diameter of the cylindrical portion 5a (6a) is d, as shown in an embodiment described later, the value in the cavity 9 depends on the value of c / d. The strength of the orientation magnetic field is different. Specifically, since a high orientation magnetic field can be obtained when c / d is in the range of 20 to 60%, it is desirable that the pole pieces 5 and 6 are produced according to this.

  Even if the present inventors initially extended the exciting coil 7 (8) as shown in FIG. 1, there is a magnetic gap between the exciting coil 7 (8) and the truncated cone part 5b (6b). For this reason, it was assumed that it was not effective in improving the strength of the orientation magnetic field. However, in reality, the orientation magnetic field can be improved by about 20% by applying the present invention. This can be said to be a remarkable effect exceeding the prediction of those skilled in the art.

The magnetic field orientation shaping | molding apparatus 1 by this invention is not restricted to the form shown in FIG. For example, like the magnetic field orientation molding device 21 shown in FIG. 2 (the same parts as those in FIG. 1 are denoted by the same reference numerals), the excitation coils 17 and 18 extend in the direction of the truncated cones 5b and 6b. The predetermined effect of the present invention can also be obtained by arranging the provided portion along the truncated cone portions 5b and 6b so as not to provide a magnetic gap.
Further, the pole piece 5 (6) is not limited to the form shown in FIG. It may have any form as long as it has a portion through which the magnetic flux passes substantially in parallel and a portion for converging the magnetic flux toward the rare earth-iron alloy powder accommodated in the cavity 9. For example, a portion corresponding to the truncated cone portion 5b can be formed by a column having a smaller diameter than the column portion 5a, or a pole piece having a cross section other than the column can be used.

Hereinafter, the present invention will be described based on specific examples.
The magnetic field generated in the cavities 9 and 39 was measured using the magnetic field orientation molding apparatus 1 according to the present invention shown in FIG. 1 and the conventional magnetic field orientation molding apparatus 31 shown in FIG. The results are shown in Table 1. The effective magnetic field area ratio in Table 1 refers to the ratio of the area where a magnetic field of 1114 kA / m or more is generated to the area of the magnetic pole face (5c, 6c). Even if the generated magnetic field strength is high, if it is partial, it is insufficient to improve the degree of orientation of the permanent magnet, and the generated magnetic field strength is high and the uniform magnetic field area ratio is large. Required for improvement. The measurement conditions are as follows, and a to d correspond to a to d in FIG.

<Measurement conditions of the present invention, common to the past>
Distance between pole pieces = 150 mm, coil surface interval = 240 mm, energizing current value = 1000 A
* Excitation coil specifications: A square pipe copper wire of 12 mm x 7.5 mm is used, and 26 turns of double pancake winding is divided into 7 blocks (total 182 turns), which are arranged in each of the excitation coils 7 and 8 in FIG. Excitation coil inner diameter = φ350 mm, excitation coil outer diameter = φ728 mm, excitation coil length = 189 mm
<Measurement conditions of the present invention>
a = 80 mm, b = 45 mm, c = φ140 mm, d = φ350 mm
a−b = 35 mm , c / d = 0.40
<Measurement conditions Conventional>
a = 47.5 mm, b = 47.5 mm, c = φ280 mm, d = φ350 mm
a−b = 0 mm , c / d = 0.80

As shown in Table 1, according to the present invention (ab = 35 mm), the generated magnetic field strength is improved by about 18% compared to the conventional case (ab = 0 mm), and the magnetic field strength is uniform. It can be seen that the ratio has also improved.
Rare earth magnet (composition: 31.5 wt% Nd-0.5 wt% Co-0.2 wt% Al-1) obtained by sintering the compact obtained by the magnetic field orientation molding apparatus 1 of the present invention and the conventional magnetic field orientation molding apparatus 31. 0.0 wt% B-bal.Fe) was measured. The results are shown in Table 2, and it can be seen that the rare earth magnet obtained by the magnetic field orientation molding apparatus 1 of the present invention has improved magnetic properties as the degree of orientation is improved.

  Under the above conditions, the magnetic field strength was measured when the value of the current applied to the exciting coil was changed. The result is shown in FIG. In order to obtain the magnetic field strength obtained at a current value of 1000 A in the present invention by the conventional magnetic field orientation molding apparatus 31, it is necessary to flow a large current of about 1300 A. However, it is rare that a magnetic field orientation molding apparatus that is currently popular is capable of passing such a large current, and the excitation coil generates a lot of heat.

  Using the magnetic field orientation molding apparatus 1 of the present invention, a magnetic field generated by changing a value of b (see FIG. 3) while fixing a (see FIG. 3) was measured. The measurement conditions are as follows. The graph of FIG. 5 shows the measured generated magnetic field with the ab value as the horizontal axis. As shown in FIG. 5, it can be seen that the intensity of the generated magnetic field depends on the value of ab. It can be seen that under the conditions of Example 2, ab should be 5 to 65 mm, preferably 20 to 65 mm, more preferably 25 to 55 mm.

<Measurement conditions>
* Distance between pole pieces = 150 mm, coil surface interval = 240 mm, energization current value = 1000 A
* Excitation coil specifications: A square pipe copper wire of 12 mm x 7.5 mm is used, and 26 turns of double pancake winding is divided into 7 blocks (total 182 turns), which are arranged in each of the excitation coils 7 and 8 in FIG. Excitation coil inner diameter = φ350 mm, excitation coil outer diameter = φ728 mm, excitation coil length = 189 mm
* Current value = 1000A
* Ab = 5 to 65 mm , c = φ212 mm , d = φ350 mm , c / d = 0.30

  Using the magnetic field orientation molding apparatus 1 of the present invention, the magnetic flux density generated by changing a value of c / d while fixing a and b was measured. The measurement conditions are as follows. The graph of FIG. 6 shows the measured magnetic flux density with the value of c / d as the horizontal axis. As shown in FIG. 6, the magnetic flux density depends on the c / d value, and c / d should be 0.20 to 0.60, preferably 0.30 to 0.50.

<Measurement conditions>
* Distance between pole pieces = 150 mm, coil surface interval = 240 mm, energization current value = 1000 A
* Excitation coil specifications: A square pipe copper wire of 12 mm x 7.5 mm is used, and 26 turns of double pancake winding is divided into 7 blocks (total 182 turns), which are arranged in each of the excitation coils 7 and 8 in FIG. Excitation coil inner diameter = φ350 mm, excitation coil outer diameter = φ728 mm, excitation coil length = 189 mm
* Current value = 1000A
* A = 80 mm, b = 35 mm, ab = 45 mm, c = φ70 to 280 mm, d = φ350 mm, c / d = 0.20 to 0.80

It is a front fragmentary sectional view which shows the structure outline of the magnetic field orientation shaping | molding apparatus in embodiment of this invention. It is a front fragmentary sectional view which shows the structure outline of the modification of the magnetic field orientation shaping | molding apparatus in embodiment of this invention. FIG. 5 is a diagram showing an orientation magnetic field generation unit in the embodiment of the present invention. It is a graph which shows the relationship between the electric current value supplied to the magnetic field orientation shaping | molding apparatus by this invention, and the conventional magnetic field orientation shaping | molding apparatus, and the generated magnetic field. It is a graph which shows the value of the ab of the magnetic field orientation shaping | molding apparatus by this invention, and the relationship of the generated magnetic field. It is a graph which shows the relationship between the value of c / d of the magnetic field orientation shaping | molding apparatus by this invention, and the generated magnetic flux density. It is front sectional drawing which shows the structure outline of the conventional magnetic field orientation shaping | molding apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Magnetic field orientation shaping | molding apparatus, 2 ... Upper punch, 3 ... Lower punch, 4 ... Die, 5 ... Pole piece, 6 ... Pole piece, 5a ... Cylindrical part, 5b ... Frustum part, 6a ... Cylindrical part, 6b ... Cone Base, 7 ... excitation coil, 8 ... excitation coil, 9 ... cavity, 10 ... housing

Claims (9)

A pair of punches arranged opposite to each other;
Forming a cavity for accommodating the powder to be molded together with a pair of the punches, and press-molding the powder to be molded; and
A pair of pole pieces arranged opposite to each other with the die interposed therebetween, and an excitation coil attached to each of the pair of pole pieces, and a magnetic field in a direction perpendicular to the direction of the pressure molding was accommodated in the cavity An orientation magnetic field generator to be applied to the powder to be molded,
The pole piece has an equal cross-sectional area with the same cross-sectional area in the direction of the magnetic field, and a cross-section that is continuous with the equal cross-sectional area and smaller than the equal cross-sectional area and is disposed facing the die. With an area reduction part,
The magnetic field orientation forming apparatus, wherein the excitation coil is provided across the equal cross-sectional area portion and the cross-sectional area decreasing portion.   The excitation coil is disposed in the entire region along the direction of the magnetic field in the equal cross-sectional area portion, and is disposed in the entire region or a part along the direction of the magnetic field in the cross-sectional area reduction portion. The magnetic field orientation molding apparatus according to claim 1.   3. The magnetic field orientation forming apparatus according to claim 1, wherein the exciting coil is disposed with or without forming a magnetic gap with the cross-sectional area reducing portion.   2. The pole piece according to claim 1, wherein a connecting portion between the equal cross-sectional area portion and the cross-sectional area reducing portion has the same cross-sectional area, and the cross-sectional area decreasing portion continuously decreases in cross-sectional area. The magnetic field orientation shaping | molding apparatus in any one of -3.   5. The magnetic field orientation molding apparatus according to claim 4, wherein the equal cross-sectional area portion is formed of a cylindrical member, and the cross-sectional area reduction portion is formed of a truncated cone-shaped member. A pair of punches arranged opposite to each other;
Forming a cavity for accommodating the powder to be molded together with a pair of the punches, and press-molding the powder to be molded; and
A pair of pole pieces arranged opposite to each other with the die interposed therebetween, and an excitation coil attached to each of the pair of pole pieces, and a magnetic field in a direction perpendicular to the direction of the pressure molding was accommodated in the cavity An orientation magnetic field generating unit to be applied to the powder to be molded,
The pole piece includes a columnar base portion, and a truncated cone portion that is continuous with the base portion and whose cross-sectional area decreases toward the die and whose front end face the die.
The excitation coil is provided across the base and the truncated cone part,
The diameter of the base is d,
When the diameter of the tip surface of the truncated cone part is c,
A magnetic field orientation molding apparatus characterized in that c / d is set in a range of 0.2 to 0.8.   c / d is 0.3-0.6, The magnetic field orientation shaping | molding apparatus of Claim 6 characterized by the above-mentioned. An orientation magnetic field generator that applies a magnetic field in a direction perpendicular to the pressurizing direction to the magnetic powder that has been press-molded,
The orientation magnetic field generator comprises:
An exciting coil that generates magnetic flux when energized;
A pole piece for supplying the magnetic flux generated by the exciting coil toward the magnetic powder,
The pole piece includes a base part through which the magnetic flux passes substantially in parallel, and a converging part for converging the magnetic flux that has passed through the base part toward the magnetic powder and emitting from the tip surface thereof,
The distance in the direction of passage of the magnetic flux from the front end surface of the converging portion to the base is a,
When the distance in the magnetic flux passage direction from the front end surface of the convergence portion to the excitation coil is b,
An orientation magnetic field generator characterized by ab> 0. The base portion is a cylindrical member, and the converging portion is a truncated cone-shaped member. When the diameter of the base portion is d and the diameter of the tip surface of the converging portion is c, c / d is 0.2 to 0.6. The orientation magnetic field generator according to claim 8 , wherein the orientation magnetic field generator is provided.

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