JP2911017B2 - Manufacturing method of radial anisotropic rare earth sintered magnet - Google Patents

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 a radially anisotropic rare earth sintered magnet.

[0002]

2. Description of the Related Art Anisotropic magnets made by finely pulverizing crystalline magnetic anisotropic materials such as ferrites and rare earth alloys and press-molding them under a specific magnetic field are used for speakers, motors, measuring instruments,
Widely used for other electrical equipment. Of these, rare earth sintered magnets having anisotropy in the radial direction in particular have excellent magnetic properties, can be freely magnetized in the axial direction, and are easy to perform multipolar magnetization and skew magnetization to suppress cogging. . When the segment magnets are bonded to form a cylindrical magnet, some reinforcement is necessary to prevent the magnet from peeling off due to the centrifugal force caused by the high-speed rotation of the motor. Although the characteristics are deteriorated, the radial anisotropic magnet does not require reinforcement and has excellent motor characteristics. For these reasons, radial anisotropic magnets are used in AC servomotors, DC brushless motors, and the like. In particular, in recent years, a long radial anisotropic magnet has been demanded with the improvement of motor characteristics.

[0003]

A sintered magnet having a radial orientation may be molded in a mold having a radial orientation during molding in a magnetic field. After filling the pulverized magnetic powder, a coil forms a magnetic field in the direction of the arrow. FIG. 5 shows the state of the magnetic field orientation in the AA 'cross section at this time. As shown in FIG. 5, a magnetic field in the radial direction can be obtained from the core 2 into the mold. Thereafter, compression molding is performed by pressing to obtain a radially anisotropic molded body. The orientation magnetic field of the mold is determined by the outer periphery, the inner periphery, and the height of the mold, and is represented by the formula (1). k = I ² s / 4hO (1) (where O: outer circumference, I: inner circumference, h: height, s: saturation magnetization of the core, k: orientation magnetic field) Since it is about 2 Tesla and k is about 1 Tesla, the mold height at which a sufficient orientation can be obtained is expressed by the following equation (2). ^{h ≦ I 2/2 · O} ··· (2) is uniform height obtained orientation magnetic field is the inner circumference smaller outer circumference by more than that lower than large, (2) the h
If the mold height is set to the above height, a magnetic field sufficient for radial alignment will not be obtained. Therefore, it has been difficult to produce a long radial anisotropic magnet required for a high-performance motor. The present invention has been made in order to solve such problems, and provides a radially anisotropic rare earth sintered magnet having no seams, having a uniform orientation even in a height direction, and having a long length. It is a manufacturing method.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a long radially anisotropic member is formed by bonding and sintering an arc-shaped compact having radial anisotropy. In the manufacture of Nd-Fe-B-based radial anisotropic rare earth sintered magnets, first, an arc-shaped molded body having radial anisotropy was prepared. Next, a method for producing a radially anisotropic rare earth sintered magnet is characterized in that these are combined in a cylindrical shape with a binder, compression molded, combined and sintered.

Hereinafter, the present invention will be described in detail.

The Nd-Fe-B-based radially anisotropic rare earth sintered magnet according to the present invention is obtained by combining cylindrical shaped bodies having radial anisotropy into a cylindrical shape to obtain a cylindrical shaped body. The magnetic properties are determined by the degree of orientation of the arc-shaped molded body. The arc-shaped molded body obtains a radially oriented magnetic field by applying a magnetic field generated in a coil to a mold through a ferromagnetic material. According to this method, since the cross-sectional area of the ferromagnetic core is substantially equal to the cross-sectional area of the mold, a magnetic field sufficient for orientation can be obtained in the mold. Therefore, a cylindrical molded product obtained by combining such radially anisotropic arc-shaped molded products can have a uniform orientation even in the height direction and can be made long. Further, since this compact is pressed again by the external pressure, the arc-shaped compacts are combined by the subsequent shrinkage and densification by sintering to form a cylindrical sintered compact. However, preferably, in order to prevent cracks occurring at the boundaries between the respective arc-shaped compacts, it is preferable that rare-earth-rich magnetic alloy powder be interposed at these boundaries as a bonding agent. The cylindrical radially anisotropic rare earth sintered magnet thus obtained does not need to reinforce the outer periphery of the magnet as in the case where the segment sintered magnet is attached, and reduces the gap between the rotor and the stator. Therefore, the motor efficiency can be improved. Thus, according to the present invention, an R-Fe-B-based cylindrical radially anisotropic rare earth sintered magnet having a high height can be easily obtained.

An example of the method for producing an arc-shaped formed body having radial anisotropy of the present invention will be described below. The magnet composition elements are weighed in advance so as to have a predetermined alloy composition ratio, and are melted and solidified in a high-frequency furnace to produce an ingot. The ingot is roughly pulverized with a jaw crusher and further finely pulverized with a jet mill using N ₂ gas to obtain a fine powder having an average particle size of 3.5 μm. Next, an arc-shaped radially anisotropic molded article is produced using the magnetic field molding section shown in FIG. In the magnetic field forming section, the ferromagnetic core 2 is formed at the center and the ferromagnetic material 7 for the magnetic path is arranged outside the in-mold forming section 6 at a pressure of 1 ton / cm ² . FIG. 2 shows an arc-shaped molded body 8 whose central angle θ is 90 degrees. The four arc-shaped moldings are combined and molded again at a hydrostatic pressure of ² ton / cm ² to form a cylinder.
At this time, a bonding agent may be used to increase the bonding strength of the molded body and prevent the occurrence of cracks. This cylindrical compact is placed in a vacuum for 10
Sintering is performed at 00 to 1200 ° C for 1 to 3 hours, and then aging treatment is performed at 500 to 600 ° C for 1 to 3 hours to obtain a radially anisotropic sintered magnet.

[0007] The composition range of the R-Fe-B based rare earth magnet alloy to which the present invention is applied is as follows.
a, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and a mixed element composed of two or more elements selected from the group consisting of Lu, and Fe (Co And B, and other additional elements.

[0008]

EXAMPLES The embodiments of the present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. (Example 1) Nd, Dy, Fe, Al of 99.9% purity and purity respectively
99.5% of B is Nd 14.0- Dy 1.0-Fe 77.0- A1 1.0-B
It was weighed so as to have an atomic mixture ratio of 7.0, and was melted and solidified in a high frequency furnace to produce an ingot. The ingot was coarsely pulverized with a jaw crusher and further finely pulverized with a jet mill using N ₂ gas to obtain a fine powder having an average particle size of 3.5 μm. Next, an arc-shaped radially anisotropic molded body was produced at a pressure of 1 ton / cm ^{2 in} a mold in which the ferromagnetic core 2 was arranged at the center shown in FIG. Θ of the obtained molded body 8 was 90 degrees, the inner radius was 10.8 mm, the outer radius was 15.2 mm, and the length was 18.0 mm.
This is shown in FIG. Combine four arc-shaped molded bodies,
Molding was again performed at a hydrostatic pressure of ² ton / cm ^{2 to} obtain a cylinder.
The obtained molded body dimensions are 19.4 mm inside diameter, 27.4 mm outside diameter, and 1 height.
6.2 mm. The molded body was sintered in vacuum at 1090 ° C. for 2 hours, and further subjected to aging treatment at 580 ° C. for 1 hour to obtain a permanent magnet. As shown in FIG. 3, cubic test pieces 11 of 2 mm × 2 mm × 2 mm were cut out from the obtained sintered magnet 10 one after another in the height direction. The test piece was magnetized with a pulse magnetic field of 5 T, and then subjected to magnetic measurement using a VSM (vibrating sample magnetometer). The results are shown in Table 1. Here, 1 to 6 indicate positions when a cube 11 of 2 mm square is cut out from above the sintered magnet 10. The obtained magnetic properties were uniform in the height direction. Similarly, uniform magnetic characteristics were obtained in the circumferential direction.

(Comparative Example 1) For comparison, using a fine powder having the same composition and the same manufacturing method as in the Example and having an average particle diameter of 3.5 μm, compacting in a magnetic field was performed in a magnetic field compacting apparatus shown in FIG. 4 by a conventional method. . FIG. 5 is a sectional view of the magnetic field forming section taken along line AA ′ in FIG. The dimensions of the molded body thus obtained are
0.4 mm, inner diameter 21.5 mm, height 18.7 mm. This molded body was sintered at 1090 ° C. for 2 hours in a vacuum, and then, as shown in FIG.
Was cut out. The test piece was magnetized with a pulse magnetic field of 5 T, and then subjected to magnetic measurement using a VSM (vibrating sample magnetometer). The results are shown in Table 1. From this, it was found that the radially anisotropic sintered magnet produced according to the present invention had uniform magnetic properties in the height direction and excellent magnetic properties.

[0010]

[Table 1]

[0011]

According to the present invention, a radially anisotropic sintered cylindrical magnet having uniform and excellent magnetic properties in the height direction can be stably produced, and an AC servo motor, a DC brushless motor,
It is useful for high performance, high power, miniaturization, and the like of speaker magnets and the like, and its industrial value is extremely high.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a mold for an arc-shaped radially anisotropic molded product used in the present invention.

FIG. 2 is a perspective view showing an arc-shaped radially anisotropic molded article of the present invention.

FIG. 3 is a perspective view showing a radially anisotropic sintered magnet of the present invention and a test piece cut out therefrom.

FIG. 4 is a sectional view showing the arrangement of a conventional magnetic field shaping unit.

FIG. 5 is a sectional view taken along line A-A 'in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 ferromagnetic die 2 ferromagnetic core 3 lower punch 4 upper punch 5 coil 6 molded part in mold 7 ferromagnetic material for magnetic path 8 molded body 9 radial magnetic field 10 sintered magnet 11 test piece ← line of magnetic force

Claims (1)

(57) [Claims] 1. An Nd-Fe-B-based radially anisotropic rare earth sintered magnet is produced by first forming an arc-shaped compact having radial anisotropy, and then combining them into a cylindrical shape.
A method for producing a radially anisotropic rare earth sintered magnet, which comprises compression molding, bonding and sintering.