JPH06124822A - R-tm-b group anisotropic ring magnet and its manufacture - Google Patents

Abstract

PURPOSE:To provide an R-TM-B group anisotropic ring magnet having the magnetic flux density waveform distribution effective to counter-cogging measure of a motor, for the cost similar to conventional R-TM-B group radial anisotropic ring magnet. CONSTITUTION:An R-T-B (R is one or more kinds of rare earth metal elements, including Y, and TM is one or more kinds of transient metals) is applied with radial magnetic anisotropy, in the direction of cylinder's radial, in an actual manner, to form a ring magnet, with high anisotropic orientation A and low anisotropic orientation B alternately applied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a permanent magnet consisting essentially of R-TM-B (where R is at least one rare earth metal element containing Y and TM is at least one transition metal). ,
In particular, the present invention relates to so-called radial anisotropic ring magnets used in servo motors, spindle motors and the like.

[0002]

2. Description of the Related Art Permanent magnets substantially composed of R-TM-B have attracted attention because they are inexpensive and have high magnetic properties. The R-TM-B system magnet has excellent magnetic characteristics and R
-Mechanical strength is higher than that of a Co-based magnet, it is not brittle, and can withstand internal stress due to shrinkage of sintering. Therefore, conventional R
-Co facilitates the production of ring anisotropic magnets such as radial anisotropy and multipole anisotropy, which are considered to be difficult to produce, and have radial magnetic anisotropy in the cylindrical radial direction. Higher output and smaller size of the motor can be realized (Japanese Patent Laid-Open No. 61-284907, Hitachi Metals Technical Report 6 (19)
90) 33. reference).

However, when a radial anisotropic ring magnet is used in a motor, some motor performance may fail. In other words, the conventional radial anisotropic ring magnet has a uniform wall thickness and a uniform anisotropic orientation (uniform characteristic level) over the entire circumference in the circumferential direction of the magnet. Since the magnetic force is strong near the required portion, that is, between the poles, and the magnetic flux density changes sharply as shown in FIG. 4, there may occur a problem that the cogging torque increases. As a measure for solving the cogging torque, there is a method of skewing the magnetization of the winding side of the motor or the magnetization of the magnet, that is, a method of arranging the magnetic poles in the axial direction with respect to the axis. Further, when the magnet has a divided segment shape, a method of forming a small thickness in the vicinity of both ends of the magnet has been studied. In addition, even with a multi-pole anisotropic ring in which the same number of poles as the final magnetized state is previously provided with anisotropy, the magnetic flux density distribution may be improved by devising the die magnetic circuit for providing the anisotropy. .

[0004]

However, in the case where the winding of the motor or the magnetization of the magnet has a skew angle, the output (torque) of the motor is reduced as compared with the conventional method, or the winding or the magnet of the motor is reduced. The winding of the magnetizing yoke becomes difficult to perform, which causes a problem of cost increase. In addition, the method of reducing the thickness of the divided segment magnets in the vicinity of both ends causes an increase in processing cost.
Further, when the polar anisotropy ring is applied, there is a problem that the applicable range is limited in terms of cost because it is necessary to secure a sufficient thickness in order to exert its effect.
Therefore, the present invention has an R-TM-B having a magnetic flux density waveform distribution effective for countermeasures against cogging of a motor at a cost equivalent to that of the conventional R-TM-B radial anisotropic ring magnet.
An object is to provide a system anisotropic ring magnet.

[0005]

The present invention provides an R-TM-B
(However, R is one or more of rare earth metal elements including Y, T
In a ring magnet in which M is substantially one or more of transition metals and is provided with radial magnetic anisotropy in a cylindrical radial direction, high anisotropy orientation and low anisotropy orientation are alternately provided. By doing so, the above problem was solved. The radial anisotropic ring magnet is radially aligned in the radial direction in the pre-sintering magnetic field molding, but high magnetic field strength and low magnetic field strength are alternately formed in the circumferential direction in the magnetic field molding. It is possible to manufacture the ring magnet of the present invention in which the high anisotropy orientation and the low anisotropy orientation are alternately provided by performing the above step. Such an orientation magnetic field can be formed by providing non-magnetic portions at equal intervals in the circumferential direction of the molding die or core made of a magnetic material.

[0006]

[Function] Since the radial anisotropic ring magnet has a portion with a low orientation-adjusted characteristic locally, when it is finally magnetized in a multi-pole manner in accordance with the inter-electrode portion, it has a normal uniform orientation. Compared to the case of using a radial anisotropic ring magnet, the lower magnetizability and magnetic property level near the gap between the poles makes the change in the surface magnetic flux density between the poles smoother, and is effective as a measure against motor cogging. Become.

[0007]

EXAMPLES Examples of the present invention will be described below. Figure 2
FIG. 3 is an example of a circumferential sectional view in the vicinity of a molding space of a magnet molding die according to the present invention. In FIG. 2, 1 is a magnetic core,
Reference numeral 2 is a molding space (cavity) for filling the raw material powder during magnet molding, 3 is a sleeve for protecting the die, and 4a is a magnetic die having 8 non-magnetic portions 4b evenly arranged in the circumferential direction. Similar to the conventional radial anisotropic die ring, when an external magnetic field coil is energized, a magnetic flux flows between any magnetic bodies of the core 1 and the die 4a to form a radial orientation magnetic field. The strength is different between the portion 5a having no non-magnetic portion and the portion 5b having the non-magnetic portion because the substantial gap changes depending on the presence or absence of the die non-magnetic portion 4b. The orientation magnetic field strength can be arbitrarily adjusted, and a magnet having a characteristic distribution (orientation distribution) adjusted according to the purpose can be manufactured. Table 1 shows the results of measuring the magnetic characteristics in the radial direction by cutting out a ring magnet (outer diameter φ70 mm, inner diameter φ58 mm, height 20 mm) produced by the mold having the structure shown in FIG.

[0008]

[Table 1] As shown in Table 1, in the mold, a portion A where the non-magnetic portion 4b is not present (a portion where a normal radial anisotropic ring orientation is obtained) and a portion B where the non-magnetic portion 4b is present (orientation level adjusting portion) Causes a difference in magnetic characteristic level. This is illustrated in FIG. 1, in which high anisotropic orientation portions A and low anisotropic orientation portions B are alternately formed. When the orientation level adjusting portion is placed between the poles of this anisotropic ring magnet and the outer peripheral eight poles are attached, a magnetic flux density distribution on the outer peripheral surface as shown in FIG. 3 is obtained, and the ordinary radial anisotropic ring magnet shown in FIG. 4 is obtained. For the waveform of, the change in the magnetic flux density near the gap becomes smooth,
It was extremely effective in reducing cogging after motor assembly. In addition, R-TM having a non-uniform orientation in the circumferential direction
-The B-type sintered magnet has a problem that when it is sintered alone, the deformation during firing becomes large due to the significant difference in the firing shrinkage rate depending on the degree of anisotropy. However, a circular ring is inserted in the inner diameter during sintering. By sintering (see Japanese Patent Laid-Open No. 1-117003), it is possible to obtain a sintered body having the same roundness as that of the conventional radial anisotropic ring magnet. The sintering method was also adopted in this example. Further, in the present embodiment, the non-magnetic portion is locally arranged on the die side (outer peripheral portion), but the same effect can be expected by arranging the non-magnetic portion on the core side (inner peripheral portion). You can easily assume.

[0009]

According to the present invention, by only changing a part of the magnetic circuit of the magnetic field molding die, a surface more effective as a countermeasure against motor cogging at a cost almost equal to that of the conventional radial anisotropic ring magnet. R- having a magnetic flux density waveform
A TM-B system anisotropic ring magnet can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing an orientation degree of an R-TM-B anisotropic ring magnet according to the present invention.

FIG. 2 is a sectional view of an essential part of a mold for molding the anisotropic ring magnet of the present invention.

FIG. 3 is a view showing a magnetic flux density distribution on the outer peripheral surface of the anisotropic ring magnet of the present invention.

FIG. 4 is a diagram showing a magnetic flux density distribution on the outer peripheral surface of a conventional anisotropic ring magnet.

Claims (3)

[Claims] 1. R-TM-B (wherein R is one or more rare earth metal elements including Y, and TM is one or more transition metal).
In a ring magnet having a substantially cylindrical shape and being radially imparted with magnetic anisotropy in a radial direction, a high anisotropy orientation and a low anisotropy orientation are alternately applied.
-TM-B type anisotropic ring magnet. 2. R-TM-B (wherein R is one or more rare earth metal elements including Y, and TM is one or more transition metal).
When manufacturing a ring magnet in which the magnetic anisotropy is given radially in a cylindrical radial direction, the high magnetic field strength and the low magnetic field strength are alternately formed in the circumferential direction in the magnetic field molding. R-TM-
Method for manufacturing B-type anisotropic ring magnet. 3. A high orientation magnetic field strength and a low magnetic field orientation strength are alternately formed by forming non-magnetic portions at equal intervals in the circumferential direction of a molding die or core made of a magnetic material.
The method for manufacturing the R-TM-B anisotropic ring magnet according to item 1.