JPH08130143A - Anisotropic bonded magnet and manufacturing method - Google Patents

Abstract

PURPOSE: To make it possible to manufacture an anisotropic rear-earth bonded magnet using a method of anisotropic orientation of polarity. CONSTITUTION: A die 2 is made up of a temporary compression molding unit 2A with an electromagnetic coil 6 and a main compression molding unit 2B. In the temporary compression molding unit 2A, a molding space among upper and lower punches 3 and 4, a core 5 and the die 2 is filled with rear-earth magnetic powder mixed with a binder. Then, pulse current is applied continuously to the electromagnet 6 to from an orientated magnetic field in the molding space. The temporary compression molding is carried out in the orientated magnetic field with a surface pressure of 0.5 to 1ton/cm<2> . The temporary molded body is moved to the main compression molding unit 2B to mold under surface pressure of 5 to 10ton/cm<2> .

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an anisotropic bonded magnet and an anisotropic bonded magnet obtained by the manufacturing method.

[0002]

2. Description of the Related Art In recent years, the use of rare earth bonded magnets has been expanding with the miniaturization of electronic devices. The rare-earth bonded magnet is formed by kneading a rare-earth alloy powder with a binder such as a synthetic resin, and has excellent magnetic properties, and is also lightweight and has a strong resistance to breakage. The most widely used rare earth bond magnet at present is an isotropic neodymium-iron-boron bond magnet. In this magnet, a magnetic powder (MQ powder) manufactured by General Motors having a neodymium-iron-boron-based composition is kneaded with a thermosetting resin such as an epoxy resin, compression molded, and finally subjected to a thermosetting treatment. Manufactured by manufacturing, surface pressure 5
The volume ratio of the magnetic powder becomes 70% or more by the compression molding of about ton / cm ² , and the magnetic characteristics also have the maximum energy product BHmax 8 to 12M.
It shows the high value of GOe. Further, since there is no need for magnetic field orientation during molding, the manufacturing is simple and the cost is low.

However, with the recent further miniaturization of electronic devices, there has been a demand for rare earth bond magnets having magnetic characteristics superior to those of the above isotropic neodymium-iron-boron bond magnets. In order to enhance the magnetic properties of the magnet, it is effective to orient the magnetic powder to make it magnetically anisotropic. For example, an anisotropic samarium-cobalt bond magnet is compression molded in a transverse magnetic field of 15 kOe. The maximum energy product BHmax 15MG
It has been confirmed to be an excellent magnet having Oe.

As one method of magnetically anisotropically transforming magnetic powder, there is a polar anisotropic orientation method, which has been widely used in the field of sintered ferrite magnets. In this method, a magnetic field generating means such as an electromagnetic coil is embedded in a molding die, and the magnetic field generating means generates an orientation magnetic field in a molding region for compression molding. According to this method, since the orienting magnetic field acts locally, it is possible to take a large number of molds by preparing a plurality of molding dies incorporating the magnetic field generating means on the press ram, which is excellent in productivity. Has become. Further, when applied to a ring-shaped magnet, there is also an advantage that high magnetic characteristics can be obtained because the orientation direction and the magnetization direction coincide with each other.

By the way, according to the above-mentioned polar anisotropic orientation method, it is necessary to bring the electromagnetic coil as close as possible to the magnetic powder in order to improve the efficiency of orientation, and the surface pressure that can be endured by the forming die is reduced accordingly. Become. In this case, the surface pressure required for forming the sintered ferrite magnet is about 1 ton / cm ² at most, which is not a serious problem, but in the production of the rare earth bonded magnet, the surface pressure is 5 to 10 as the forming pressure.
Ton / cm ² is required, and it is practically impossible to use this ultra-anisotropic orientation method.

Therefore, conventionally, when compression-molding a ring-shaped anisotropic rare earth bonded magnet, an electromagnet is attached to the upper and lower rams of the press, and a radial magnetic field is formed by the repulsion of opposing magnetic force lines. Only the so-called radial orientation method in which magnetic powder is oriented and compression-molded has been used.

[0007]

However, according to the production of the anisotropic bonded magnet by the above radial orientation method,
Since the magnetic powder must be placed in the center of the radial magnetic field, it is difficult to obtain a large number of powders, and there is a problem that productivity is deteriorated and manufacturing cost is inevitably increased.

The present invention has been made in view of the above-mentioned conventional problems, and enables the production of anisotropic rare earth bonded magnets by utilizing the polar anisotropic orientation method, thereby improving the productivity and reducing the production cost. Providing a manufacturing method that greatly contributes to reduction,
Another object is to provide a high-performance anisotropic bonded magnet obtained by this manufacturing method.

[0009]

In order to achieve the above object, a method for producing an anisotropic bonded magnet according to the present invention is one in which a magnetic powder is magnetically oriented and temporarily compression molded, and then a predetermined surface pressure is applied. It is characterized in that the main compression molding is performed.

In the present invention, the temporary compression molding and the main compression molding can be carried out by using different molding dies in different steps, but they are carried out in the same process at different parts in the same molding dies. It is desirable to do so.

The features of the present invention will be further described with reference to the drawings. FIG. 1 conceptually shows a method for manufacturing a ring-shaped anisotropic bonded magnet. A forming die indicated by reference numeral 1 is a die 2, an upper punch 3, and a lower punch 4 as in a conventional ordinary forming die. And a core 5. Then, the die 2 used in the present invention has the upper half thereof as the temporary compression molding portion 2A,
A lower half thereof is partitioned as a main compression molding portion 2B, and an electromagnetic coil 6 for generating an orientation magnetic field in a molding region is embedded in the upper temporary compression molding portion 2A.

At the time of compression molding, first, a magnetic powder 7 mixed with a binder is filled in a molding region inside the temporary compression molding portion 2A of the die 2, and then a pulse current or a steady current is passed through the electromagnetic coil 6 to form a molding region. An orienting magnetic field is generated, and in this magnetic field, the upper punch 3 is moved downward so that the surface pressure becomes 0.5.
Temporarily compression molded at ~ 1 ton / cm ² (). Next, the die 2 and the upper punch 3 and the lower punch 4 are moved relative to each other, and the temporary molded body is transferred to the main compression molding section 2B of the die 2, and the surface pressure 5
Main compression molding is carried out at 10 ton / cm ² to obtain a ring-shaped molded body 8 (). The molded body (ring) 8 thus obtained is an anisotropic bonded magnet having a magnetic powder volume ratio of 70% or more and four or more magnetic poles on the outer periphery.

On the other hand, in order to obtain a ring-shaped magnet whose inner circumference is a magnetic pole, as shown in FIG. 2, the core 5 is divided into a lower temporary compression molding portion 5A and an upper main compression molding portion 5B. Then, the electromagnetic coil 6 is embedded in the temporary compression molding portion 5A. The compression molding is performed in the same procedure as described with reference to FIG. 1 above. First, the magnetic powder 7 is filled in the molding region outside the temporary compression molding portion 5A of the core 5, and the temporary compression molding is performed in the orientation magnetic field by the electromagnetic coil 6. Then, the temporary molded body is transferred to the main compression molded portion 5B of the core 5 to perform the main compression molding, and the ring-shaped molded body 8 is formed.
Get (). The molded body (ring) 8 thus obtained is an anisotropic bonded magnet having a magnetic powder volume ratio of 70% or more and four or more magnetic poles on the inner circumference.

As the magnetic powder used in the present invention, various rare earth alloy powders having magnetic anisotropy, for example, neodymium-iron-boron alloy powder, samarium-
Cobalt-based alloy powder and samarium-iron-nitrogen-based alloy powder can be used. In addition, examples of the binder include pure metals such as zinc and tin, alloys thereof, thermosetting resins such as epoxy resins and phenol resins, polyamide resins (nylon), polyphenylene sulfide (PPS), polybutylene terephthalate (PBT). ) And other thermoplastic resins can be used.

In the present invention, a permanent magnet can be used in place of the above-mentioned electromagnetic coil 6 in order to generate an orientation magnetic field in the molding region. In the present invention, the temporary compression molding portions 2A, 5A and the main compression molding portion 2B, which are set in the molding die,
The vertical relationship with 5B is arbitrary, and any one is selected in consideration of molding efficiency. Further, in the present invention, after the temporary compression molding, a reverse current may be applied to the electromagnetic coil 6 to perform demagnetization (demagnetization).

[0016]

In the production of the anisotropic bonded magnet configured as described above, when the magnetic powder is magnetically oriented, the magnetic powder is pre-compressed with a small surface pressure. The powder can be anisotropic. Further, by performing the main compression molding with a large surface pressure after the temporary compression molding, it becomes possible to sufficiently increase the magnetic powder volume ratio to 70% or more. Further, when the temporary compression molding and the main compression molding are performed at different parts in the same molding die, the compression molding can be continuously performed.

[0017]

Embodiments of the present invention will be described below.

Example 1 A neodymium-iron-boron magnetic powder produced by a hydrogen treatment method (HDDR method) was pulverized with a pin mill to an average particle size of 150 μm (μm) or less, and an epoxy resin 2. 5 wt% was added and kneaded.
It was put in the molding die 10A shown in 4 and 4 and compression molded by a hydraulic press. The molding die 10A is supported by a ring-shaped die 11, a cylindrical upper punch 12 supported by a press upper ram (not shown), and a press lower ram (not shown) facing the upper punch 12. The cylindrical lower punch 13 and the core 14 inserted into the die 11 are roughly configured.

The die 11 is a temporary compression molding portion 1 on the upper side.
5 and the main compression molding portion 16 on the lower side. The upper temporary compression molding portion 15 is composed of an inner thin sleeve 17 and an outer thick cylindrical yoke 18, and a 12-pole electromagnetic coil 19 is embedded in the yoke 18. On the other hand, the main compression molding portion 16 is composed of an inner cylindrical die body 20 and an outer cylindrical die holder 21. It should be noted that the sleeve 17 and the die body 20 constituting the die 11 are
The upper and lower punches 12 and 13 and the core 14 are made of non-magnetic carbide, and the die holder 21 is made of stainless steel (for example, SU.
S 304), the yokes 18 are each made of pure iron. The die body 20 has a wall thickness of about 8 mm.

In this embodiment, a capacitor type pulse power source (not shown) is connected to the electromagnetic coil 19. At the time of compression molding, first, the mixture (magnetic powder) 22 is filled in the molding region inside the temporary compression molding portion 15 of the die 11, and then the electromagnetic coil 19 is intermittently supplied with a pulse current of 20 KA for 10 msec. An orientation magnetic field is generated in the area. Then, in this magnetic field, the upper punch 12 was moved downward to perform temporary compression molding at a surface pressure of 0.5 ton / cm ² , and subsequently demagnetized. Next, the upper punch 12 and the lower punch 13 are moved downwards as they are, and the temporary compact is transferred to the main compression molding part 16 of the die 11, and the main compression molding is performed at a surface pressure of 5 tons / cm ² to form a ring shape. A molded body of was obtained. After that, the molded body is taken out from the molding die 10A, subjected to heat curing treatment at 150 ° C. for 1 hour, and then magnetized to have an anisotropic ring shape as shown in FIGS. 5 (1) and 5 (2). Curable bonded magnet sample 1 was obtained, and this was subjected to a measurement test of magnetic powder volume ratio and magnetic characteristics. The bonded magnet sample (hereinafter, simply referred to as a magnet sample) 1 has an outer diameter of 22 mm, an inner diameter of 20 mm, a height of 8 mm, and an outer circumference of 12 poles. For comparison, the above M
An isotropic magnet sample 2 having the same dimensions was manufactured by mixing Q powder (neodymium-iron-boron-based alloy) with an epoxy resin in the same amount as described above and performing compression molding. It was subjected to a measurement test.

Table 1 shows the measurement test of the magnetic powder volume ratio and magnetic characteristics of the magnet samples 1 and 2 obtained as described above. The magnetic characteristics were measured using a vibrating sample magnetometer (VSM). From the results shown in the table, it was confirmed that the magnetic powder volume ratio of the magnet sample 1 according to the present invention was 70% or more, similarly to the general-purpose isotropic magnet sample 2, and had a sufficient magnetic powder volume ratio. . As for the magnetic characteristics, the residual magnetic flux density Br, the coercive force iHc, and the maximum energy product BHmax are all the magnet sample 1 according to the present invention.
It was confirmed that the magnetic property was higher than that of the general-purpose magnet sample 2, and the maximum energy product BHmax was twice as high, and the magnetic properties were remarkably excellent.

[0022]

[Table 1]

FIG. 6 shows the measurement results of the surface magnetic flux of the magnet samples 1 and 2. The surface magnetic flux was measured using a flux meter. In the figure, the solid line shows the result for the magnet sample 1 according to the present invention, and the dotted line shows the result for the general-purpose isotropic magnet sample 2, respectively. From this, the magnet sample according to the present invention is shown. 1 has a surface magnetic flux that is about 25% higher than that of the magnet sample 2 over the entire circumference.

Example 2 A neodymium-iron-boron magnetic powder produced by the HDDR method was crushed with a pin mill to an average particle size of 150 μm or less, and 2.5 wt% of an epoxy resin was added and kneaded. This mixture is shown in FIGS. 7 and 8 in a mold 10B.
And was compression-molded by a hydraulic press. Mold 1
0B is basically the same as that used in Example 1 (FIGS. 3 and 4), but here, the yoke 18 constituting the temporary compression molding portion 15 of the die 11 is made of a non-magnetic material (SUS304).
12 permanent magnets 25 are embedded in place of the electromagnetic coil 19. The permanent magnet 25 is made of a neodymium sintered magnet and has a maximum energy product BHmax of 30M.
It is GOe.

In compression molding, first, the molding region inside the temporary compression molding portion 15 of the die 11 is filled with the above mixture (magnetic powder) 22, and a surface pressure of 0.5 is applied under the orientation magnetic field of the permanent magnet 25. Temporary compression molding at ton / cm ² is performed, followed by demagnetization, then the temporary compact is transferred to the main compression molding section 16 of the die 11 and subjected to main compression molding at a surface pressure of 5 tons / cm ² . A ring-shaped molded body was obtained. Then, the molded body was taken out of the molding die, subjected to a heat curing treatment at 150 ° C. for 1 hour, and further magnetized to obtain a magnet sample 3 having the same number of poles and the same size as in Example 1, which was measured by a flux meter. The surface magnetic flux was subjected to a measurement test.

FIG. 9 shows the measurement result of the surface magnetic flux of the magnet sample 3 in comparison with the result of the magnet sample 1 obtained in the above-mentioned bending 1. In the figure, the solid line shows the results for the magnet sample 3 according to the present invention, and the dotted line shows the results for the magnet sample 1 obtained in Example 1, respectively. Sample 3 has a surface magnetic flux that is not substantially different from that of magnet sample 1 over the entire circumference, and it has been clarified that excellent magnetic characteristics can be obtained even when a permanent magnet is used for magnetic field orientation.

Example 3 A neodymium-iron-boron type magnetic powder produced by the HDDR method was crushed with a pin mill to an average particle size of 100 μm or less, and 2.8 wt% of an epoxy resin was added and kneaded. This mixture was molded into a mold 1 shown in FIGS.
It was put in 0 C and compression molded by a hydraulic press. The molding die 10C is supported by a ring-shaped die 31, a cylindrical upper punch 32 supported by a press upper ram (not shown), and a press lower ram (not shown) facing the upper punch 32. The cylindrical lower punch 33 and the core 34 inserted in the die 31 are roughly configured.

The die 31 comprises an inner cylindrical die body 35 and an outer cylindrical die holder 36. On the other hand, the core 34 includes a lower temporary compression molding portion 37 and an upper main compression molding portion 38. The temporary compression molding portion 37 includes a thin sleeve 39 on the outer side and a columnar yoke 40 on the inner side. The main compression molding portion 38 is composed of a columnar core block 41. Then, this core 3
An electromagnetic coil 42 having 32 poles is embedded in the fourth yoke 40. The die body 35, the sleeve 39 and the core block 41 forming the core 34, the upper and lower punches 32 and 33 are made of non-magnetic cemented carbide, and the die holder 36 is made of stainless steel (for example, SUS 303). There is.

In this embodiment, a capacitor type pulse power source (not shown) is connected to the electromagnetic coil 42. When performing compression molding, first, the temporary compression molding portion 3 of the core 34 is
The mixture (magnetic powder) 43 was filled in the outer molding region of No. 7, and a pulse current of 12 KA for 10 msec was intermittently passed through the electromagnetic coil 42 to generate an orientation magnetic field in the molding region. Then, in this magnetic field, the upper punch 32 was moved downward to perform temporary compression molding at a surface pressure of 0.5 ton / cm ² , followed by demagnetization. Next, the upper punch 32 and the lower punch 33 are moved up as they are, and the temporary molded body is transferred to the main compression molding portion 38 of the core 34, and the main compression molding is performed at a surface pressure of 8 tons / cm ² to form a ring shape. A molded body of was obtained. Then, the molded body is taken out from the molding die 10C, subjected to heat curing treatment at 150 ° C. for 1 hour, and then magnetized to have an anisotropic ring shape as shown in FIGS. 12 (a) and 12 (b). Bonded magnet sample 4 was obtained, and this was subjected to a surface magnetic flux measurement test using a flux meter. The magnet sample 4 has an outer diameter of 33 mm and an inner diameter of 30 m.
It has m and height of 5 mm, and has an inner circumference of 32 poles. Also,
For comparison, an equal amount of epoxy resin was mixed with the MQ powder (neodymium-iron-boron alloy), and an isotropic magnet sample 5 of the same size was manufactured by compression molding, which was also used for the same surface magnetic flux measurement test. I served.

FIG. 13 shows the measurement results of the surface magnetic flux. In the figure, the solid line shows the result for the magnet sample 4 according to the present invention, and the dotted line shows the result for the general-purpose isotropic magnet sample 5, respectively. From this, the magnet sample according to the present invention is shown. No. 4 has a higher surface magnetic flux than the general-purpose magnet sample 5 over the entire circumference, and it is clear that excellent magnetic characteristics are obtained.

[0031]

As described above in detail, according to the method for manufacturing an anisotropic bonded magnet of the present invention, a two-step molding process including temporary compression molding and main compression molding is performed to achieve an extremely anisotropic shape. Magnetic powder can be anisotropy by using the orientation method, anisotropic magnets with excellent magnetic properties can be manufactured with high efficiency, which greatly contributes to improvement of productivity and reduction of manufacturing cost. Becomes Further, when the temporary compression molding and the main compression molding are performed at different portions in the same molding die, the compression molding can be continuously performed, and the productivity can be further improved.

[Brief description of drawings]

FIG. 1 is a schematic view conceptually showing a method for manufacturing an anisotropic bonded magnet according to the present invention.

FIG. 2 is a schematic view showing another concept of the method for manufacturing the anisotropic bonded magnet.

FIG. 3 is a perspective view showing the structure of a molding die used in Example 1 as a partial cross section.

4 is a cross-sectional view showing a part of the molding die shown in FIG.

5 is a schematic diagram showing the shape and magnetism of the anisotropic bonded magnet obtained in Example 1. FIG.

6 is a graph showing the measurement results of surface magnetic flux of the anisotropic bonded magnet obtained in Example 1. FIG.

FIG. 7 is a perspective view showing the structure of a molding die used in Example 2 as a partial cross section.

8 is a cross-sectional view showing a part of the molding die shown in FIG.

9 is a graph showing measurement results of surface magnetic flux of the anisotropic bonded magnet obtained in Example 2. FIG.

FIG. 10 is a perspective view showing the structure of a molding die used in Example 3 as a partial cross section.

11 is a cross-sectional view showing a part of the molding die shown in FIG.

12 is a schematic diagram showing the shape and magnetism of the anisotropic bonded magnet obtained in Example 3. FIG.

13 is a graph showing the measurement results of surface magnetic flux of the anisotropic bonded magnet obtained in Example 3. FIG.

[Explanation of symbols]

 1 Mold 2 Die 3 Upper Punch 4 Lower Punch 5 Core 6 Electromagnetic Coil 7 Magnetic Powder 8 Molded Body 2A Temporary Compression Molding Section 2B Main Compression Molding Section 5A Temporary Compression Molding Section 5B Main Compression Molding Section

Claims (5)

[Claims] 1. A method for producing an anisotropic bonded magnet, which comprises magnetically orienting magnetic powder for temporary compression molding, and then main compression molding at a predetermined surface pressure. 2. The method for producing an anisotropic bonded magnet according to claim 1, wherein the temporary compression molding and the main compression molding are performed at different portions in the same molding die. 3. The method for producing an anisotropic bonded magnet according to claim 1, wherein an oriented magnetic field is generated in the temporary compression molding region by passing a pulse current or a steady current through the electromagnetic coil. 4. The method for producing an anisotropic bonded magnet according to claim 1, wherein an orientation magnetic field is generated in the temporary compression molding region with a permanent magnet. 5. A magnetic powder volume ratio of 70% or more, having a number of poles of 4 or more and having a ring shape,
An anisotropic bonded magnet manufactured by the method according to claim 1.