JPH0638377B2 - Method for manufacturing ring-shaped multipole magnet - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a cylindrical magnet magnetized in a radial direction with multiple poles, in particular, a resin composition ring-shaped molded article containing magnetic powder.

[Conventional technology]

Ring 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. Then, the more uniform the orientation of the magnetic powder, the more excellent the magnetic properties of the magnet can be obtained. This will be further explained with reference to the drawing.

FIG. 8 shows the positional relationship between the solenoid coil of the molding apparatus used in the previously proposed method for manufacturing a ring-shaped magnetic molded body, the first magnetic member constituting the outer die, the second magnetic member and the inner die. And corresponds to a cross section perpendicular to the central axis of the cavity of the molding apparatus, that is, a cross-sectional view taken along the line I-I in FIG. 9. FIG. 9 corresponds to a sectional view taken along the line II-II in FIG. In the drawing, 1 is a pole piece, 2 is a solenoid coil surrounding the pole piece, 3 is a magnetic member of an inner type, and 4 is an outer end which is in contact with the pole piece 1 at its end and is magnetically coupled to the pole piece 1. Type magnetic member, 5 is cavity, 6, 7
Are the upper and lower bottoms of the cavity 4. (Because the invention proposed above is characterized by the magnetic mutual relation of each part of the molding apparatus used, means for supplying the composition for magnets to the cavity 5 and means for taking out a molded body from the cavity 5, etc. Since the mechanical structure of the molding apparatus of FIG. 3 may conform to the known one, it is omitted in the figure.) To manufacture a radially oriented ring-shaped molded body using the apparatus of FIG. 5 is filled with a magnet composition so that the magnetic powder can be displaced, that is, its position and posture can be changed. Although any magnetic powder such as ferrite can be used as the magnetic powder, an alloy containing a rare earth element such as a samarium-cobalt alloy that provides a high-performance magnet is preferable. Although a spatial magnetic field strength of 8 KOe or more is required to cause the powder of such an alloy to have a sufficient orientation, this method easily generates such a strong magnetic field in the radial direction in the cavity 5. Can be made.

After filling the cavity 5 with the magnet composition, when a reverse current is passed through the left and right solenoid coils 2, a magnetic field is generated as shown by the arrow in FIG. The powder is oriented in this direction. When the composition is solidified when the orientation is completed, a radially oriented molded body is obtained. The direction of the arrow in FIG. 10 indicates the direction of the magnetic flux, and its length indicates the magnitude of the magnetic flux.

[Problems to be solved by the invention]

In the case of a conventional radially oriented magnet, when the pole pitch becomes shorter (especially 3 mm or less), the area of the part that forms a closed loop of magnetic flux between adjacent poles relatively increases, so the magnet has There is a problem that it becomes difficult to fully extract the magnetism.

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

[Means for solving problems]

The method for producing a ring-shaped multi-pole magnet according to the present invention comprises applying a circular magnetic field to a magnet composition containing magnet powder filled in the ring-shaped cavity of a molding die to orient the magnetic powder in the circumferential direction. After solidifying, the inner surface or the outer surface of the ring-shaped molded body is subjected to multi-pole magnetization.

[Action]

In the present invention, by applying an annular magnetic field, the magnetic powder is solidified in the circumferentially oriented state. Then, a multi-pole magnet is formed on the inner surface or the outer surface thereof to obtain a small ring-shaped multi-pole magnet having a large surface magnetic force.

〔Example〕

1 and 2 are a plan view and a side perspective view of a molding apparatus for applying an orientation according to the present invention. In these figures, 11 is an outer die having a cylindrical space with an inner diameter φ ₁₁ formed inside, 12 is an outer die having a cylindrical outer diameter φ ₁₂ , and is an inner die smaller than the inner diameter φ ₁₁ of the outer die 11. Both are made of non-magnetic material such as ceramics. Reference numeral 13 is a conductor penetrating the center of the inner mold 12. Reference numeral 14 denotes a bottom plate, which has a hole through which the conductor 13 is led out, but closes the cap between the outer mold 11 and the inner mold 12 at another portion. A ring-shaped cavity 15 is formed between the outer mold 11 and the inner mold 12.

The orientation process by this molding device will be described below.

First, as shown in FIG. 1, a magnetic composition composed of a magnetic powder and a binder is placed in a ring-shaped cavity 15 formed between an outer mold 11 and an inner mold 12 so that the magnetic powder can be displaced. To fill.

Next, when a direct current or a pulse of a large current is applied to the conductor 13, an annular 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, 10K for rare earth magnets.
Oe or higher is required. When removed from the molding device, a ring-shaped magnetic molded body 16 as shown in FIG. 3 is obtained. In this way, multi-pole magnetization of the ring-shaped magnetic compact 16 oriented in the circumferential direction is performed next. This may be a normal multi-pole magnetization, an example of which will be described below.

That is, as shown in FIG. 4, the magnetized magnetic pole 19 in which the coil 18 is wound on the magnetic body 17 is placed outside the ring-shaped magnetic molded body 16 so that the N pole and the S pole are alternately arranged. They are arranged (only a part is shown in FIG. 4, and the others are shown by dotted lines and omitted). After that, multi-pole magnetization can be performed by passing a current through each coil 18.

In the above-described embodiment, the annular magnetic field was created by passing a large current through the conductor 13. However, as shown in FIG. 5, the conductor 20 is wound around the ring-shaped cavity 15 and the direct current is applied to this. Alternatively, an annular magnetic field may be created by passing a pulse current. This is the same as the annular magnetic field created in the annular core of the toroidal coil. 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 required for making a step motor having a large number of poles such as 24 poles and 48 poles.

Further, in the embodiment of FIG. 5, the conductor 20 must be wound each time, so in order to avoid this, the conductor 20 can be wound with a thick one so that the whole can be separated vertically and integrated. By doing so, it becomes easy to take out the ring-shaped magnetic molded body 16 inside and to fill the magnet composition into the ring-shaped cavity 15.

FIG. 6 shows another example of multi-pole magnetization, and shows a case where the magnetized magnetic poles 19 are applied from inside and outside of the ring-shaped magnetic molded body 16 to magnetize, and it is shown as a partially developed view. .

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

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 regarded as a substantially constant value, it can be seen that the effect of the present invention is large when L is small (which means that the number of poles is large).

〔The invention's effect〕

As described above, as described above, the annular magnetic field is applied to solidify the magnet composition, and thereafter, the inner surface or the outer surface of the obtained ring-shaped compact is subjected to multi-pole magnetization.
Even if the number of poles increases, the ring-shaped multi-pole magnet having a large magnetic flux density on the surface can be obtained, and it is expected to be widely used in step motors and the like in the future.

[Brief description of drawings]

FIG. 1 is a plan view of a molding apparatus used in an embodiment of the present invention, FIG. 2 is a perspective view of FIG. 1, FIG. 3 is a perspective view of a ring-shaped magnetic molded body, and FIG. A schematic plan view of a multi-pole magnetizing device used in the embodiment, FIG. 5 is a schematic plan view showing another molding device, and FIG. 6 is a partially developed plan view of another multi-pole magnetizing device.
FIG. 7 is a diagram showing the relationship between the radial orientation magnet and the average magnet density per pole with respect to L / Δr of the circumferential orientation magnet according to the present invention, and FIGS. 8 and 9 show an example of a conventional molding apparatus. Fig. 10 is a plan sectional view and a sectional view taken along the line II-II, and Fig. 10 is a diagram showing the direction and magnitude of magnetic flux in the cavity and its peripheral portion by the molding apparatus of Fig. 8. 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 magnetic pole. .

Claims (2)

[Claims] 1. A ring-shaped cavity of a molding die is filled with a composition for a magnet containing magnetic powder, which is then solidified by applying an annular magnetic field for orienting the magnetic powder in the circumferential direction. A method for producing a ring-shaped multi-pole magnet, characterized in that the inner surface or the outer surface of the ring-shaped molded body is magnetized in multiple poles. 2. The radial thickness of the ring-shaped compact is Δr,
L / Δr, where L is the length of one magnetic pole in the circumferential direction
Is 4 or less, Claim (1)
Item 7. A method for manufacturing a ring-shaped multi-pole magnet according to item.