JPS6221206A - Manufacture of ring-shaped multipolar magnet - Google Patents

Abstract

PURPOSE:To obtain a small-sized annular multipolar magnet having large surface magnetic force by a method wherein a composition for a magnet is solidified by orienting magnetic powder in circumferential direction under an annular magnetic field, and a multipolar magnet is formed on the inner or outer circumference of said composition. CONSTITUTION:The composition consisting of magnetic powder and a binder is filled up in the annular cavity 15 formed by the outer mold 11 and the inner mold 12. An annular magnetic field is formed by applying a large DC current or a pulse to a conductor 13 and the magnetic powder is oriented in circumferential direction. Then, the magnetized pole 19 consisting of a magnetic material 19 whereon a coil 18 is wound around is arranged in alternate polarity, a multipolar magnetization is performed by applying a current to each coil 18. If L/DELTAr<=4 is selected when the length in circumferential direction of a radial orientational magnetic pole is L and the thickness in radial direction is DELTAr, an excellent result can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cylindrical magnet magnetized into multiple poles in the radial direction, and particularly to a method for producing a ring-shaped molded resin composition containing magnetic powder.

[Conventional technology]

Ring-shaped magnets with multiple poles in the radial direction are widely used in various applications including small motors. In order to manufacture a high-performance ring-shaped magnet with multiple poles in the radial direction, in the process of molding magnetic powder into a ring-shape,
It is desirable that the magnetic powder be oriented in the radial direction to form a ring-shaped magnetic compact having magnetic anisotropy. The more uniform the orientation of the magnetic powder, the better the magnetic properties of the magnet. This will be further explained with reference to the figures.

Figure 8 shows the arrangement of the solenoid coil of the molding device used in the previously proposed method for manufacturing a ring-shaped magnetic molded body, the first magnetic member and second magnetic member constituting the outer mold, and the inner mold. This corresponds to a cross section perpendicular to the central axis of the cavity of the molding device, that is, a cross section taken along line II in FIG. FIG. 9 corresponds to a cross-sectional view taken along line II--II in FIG. 8.

In the figure, 1 is a pole piece, 2 is a solenoid coil surrounding it, 3 is an inner magnetic member, and 4 is an outer part that contacts the pole piece 1 at its end and is magnetically coupled to it. A magnetic member which is a mold, 5 is a cavity, and 6 and 7 are the upper bottom of the cavity 5.

It is the bottom. (Since the previously proposed invention is characterized by the magnetic interrelationship of each part of the molding device used, the means for supplying the magnet composition to the cavity 5, the means for taking out the molded body from the cavity 5, etc. (The mechanical configuration of the molding device shown in FIG. 8 is omitted in the figure because it can be based on a known one.) In order to manufacture a radially oriented ring-shaped molded product using the device shown in FIG. 5 is filled with a magnet composition so that the magnetic powder can be displaced, that is, its position and orientation can be changed. As the magnetic powder, any material including ferrite can be used, but alloys containing rare earth elements such as samarium-cobalt alloys, which provide high performance magnets, are preferred. To induce sufficient orientation in the powder of such an alloy, 8
Although the strength of the spatial magnetic field is required to be greater than KOe, according to this method, such a strong radial magnetic field can be easily generated within the cavity 7.

After filling the cavity 5 with the magnet composition, when currents in opposite directions are passed through the left and right solenoid coils, a magnetic field is generated as shown by the arrow in FIG. 10, and the magnetic powder of the magnet composition in the cavity 7 is generated. is oriented in this direction. When the composition is solidified when orientation is completed, a radially oriented molded body is obtained. Note that the direction of the arrow in FIG. 1O indicates the direction of the magnetic flux, and the length thereof indicates the magnitude of the magnetic flux.

[Problem that the invention seeks to solve]

In the case of conventional radially oriented magnets, as the pole pitch becomes shorter (particularly 3 mm or less), the area of the part where adjacent poles create a closed loop of magnetic flux increases, so the magnet's holding capacity increases. There was a problem in that it became difficult to fully draw out the magnetism that existed.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for manufacturing a ring-shaped multipolar magnet that can obtain a large surface magnetic flux even if the pole pitch is shortened.

[Means for solving problems]

A method for manufacturing a ring-shaped multipolar magnet according to the present invention includes applying an annular magnetic field to a magnet composition containing magnetic powder filled in a ring-shaped cavity of a molding die to orient the magnetic powder in the circumferential direction. After solidification, multipole magnetization is performed on the inner or outer surface of the ring-shaped molded body.

[Effect]

In this invention, by applying an annular magnetic field, the magnetic powder is solidified in a circumferentially oriented state. Next, by forming a multipolar magnet on its inner or outer surface, a small ring-shaped multipolar magnet with a large surface magnetic force can be obtained.

〔Example〕

1 and 2 are a plan view and a side perspective view of a molding apparatus for applying orientation according to the present invention.

In these figures, 11 is an outer mold in which a cylindrical space with an inner diameter of φ11 is formed inside, and 12 is a cylindrical outer mold with an outer diameter of φI2.
, the inner mold is smaller than the inner diameter φ11 of the outer mold 11,
All of them are manufactured from non-magnetic materials such as ceramics.

13 is a conductor passing through the center of the inner mold 12. 14
1 is a bottom plate, which has a hole through which the conductor 13 is led out, but other parts close the cap between the outer mold 11 and the inner mold 12. ]5
is a ring-shaped cavity formed between an outer mold 11 and an inner mold 12.

The orientation process using this molding apparatus will be explained next.

First, as shown in FIG. 1, a magnet composition consisting of magnetic powder and a binder is placed in a ring-shaped cavity 15 formed between an outer mold 11 and an inner mold 12 in such a way that the magnetic powder can be displaced. Fill it.

Then, when a large direct current or pulse current is passed through the conductor 13, a ring-shaped magnetic field is created by this large current, so that the magnetic powder in the ring-shaped cavity 15 is oriented in the circumferential direction. The magnitude of this annular magnetic field varies depending on the raw material of the magnetic powder used, but for example, in the case of a rare earth magnet, 10
KOe or higher is required. When removed from the molding apparatus, a ring-shaped magnetic molded body 16 as shown in FIG. 3 is obtained. Multipolar magnetization of the ring-shaped magnetic molded body oriented in the circumferential direction in this manner is then performed. This may be normal multi-pole magnetization, and an example thereof will be explained below.

That is, as shown in FIG. 4, the magnetic material 17. A magnetized pole 19 with a coil 18 wound around it is placed outside the ring-shaped magnetic molded body 16 so that its polarity alternates between N and S poles (only a portion is shown in FIG. 4). Others are shown with dotted lines and omitted). Thereafter, multipolar magnetization can be performed by passing current through each coil 18.

In the above embodiment, the annular magnetic field was created by passing a large current through the conductor 13, but in addition to this, as shown in FIG. Alternatively, an annular magnetic field may be created by passing a pulsed current. This is the same as the annular magnetic field created within the annular core of a toroidal coil. In addition, the fifth
In the figure, the outer mold 11 is circular.

According to the present invention, it is possible to easily obtain a ring-shaped multi-pole magnet necessary for producing a step motor having an extremely large number of poles, such as 24 poles or 48 poles.

Furthermore, in the embodiment shown in FIG. 5, it is necessary to wind the conductor 20 each time, so in order to avoid this, the conductor 20 is wound using a thick one, and the entire conductor 20 is divided into one piece.
- If the ring-shaped magnetic molded body 16 inside is taken out, it becomes easy to fill the ring-shaped cavity 15 with the magnet composition.

FIG. 6 shows another example of multi-pole magnetization, in which magnetization is performed by applying magnetizing poles 19 from the inside and outside of the ring-shaped magnetic molded body 16, and is shown as a partially developed view. .

FIG. 7 shows L/Δr (L: length of the magnetic pole in the circumferential direction, Δr:
It shows the average magnetic flux density per pole with respect to the thickness in the radial direction.

It can be seen that when L/Δr≦4, the circumferential orientation according to the present invention is superior to the conventional radial orientation. That is, since the thickness Δr can be considered to be a substantially constant value, it can be seen that the effect of the present invention is greater when L is smaller (which means a larger number of poles).

〔Effect of the invention〕

As explained above, in this invention, a magnet composition is solidified by applying an annular magnetic field, and then multipolar magnetization is performed on the inner or outer surface of the obtained ring-shaped molded body.
This has the effect of providing a ring-shaped multi-polar magnet with a large surface magnetic flux density even when the number of poles is increased, and is expected to be widely used in step motors and other applications in the future.

[Brief Description of the Drawings] Fig. 1 is a plan view of a molding device used in an embodiment of the present invention, Fig. 2 is a perspective view of Fig. 1, and Fig. 3 is a perspective view of a ring-shaped magnetic molded body. 4 is a schematic plan view of a multi-pole magnetizing device used in one embodiment of the present invention, FIG. 5 is a schematic plan view showing another molding device, and FIG. 6 is a partially expanded plan view of another multi-pole magnetizing device. FIG. 7 is a diagram showing the relationship between the average magnet density per pole and L/Δr of a radially oriented magnet and a circumferentially oriented magnet according to the present invention, and FIGS. 8 and 9 show an example of a conventional molding apparatus. Figure 10 is a cross-sectional view of the
It is a figure which shows the direction and magnitude|size of the magnetic flux in a cavity and its surrounding area by the molding apparatus of a figure. In the figure, 11 is an outer mold, 12 is an inner mold, 13 is a conductor, 14 is a bottom plate, 15 is a ring-shaped cavity, 16 is a ring-shaped magnetic molded body, 17 is a magnetic body, 18 is a coil, and 19 is a magnetized pole. . Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 L/Δr Figure 8

Claims (2)

[Claims] (1) After filling the ring-shaped cavity of the molding die with a magnet composition containing magnetic powder, solidify by applying an annular magnetic field that orients the magnetic powder in the circumferential direction, and then
A method for manufacturing a ring-shaped multipolar magnet, which comprises performing multipolar magnetization on the inner or outer surface of the obtained ring-shaped molded body. (2) When the thickness of the ring-shaped molded body in the radial direction is Δr, and the length of one magnetic pole in the circumferential direction is L, L/Δr is 4 or less. A method for manufacturing a ring-shaped multipolar magnet according to item (1).