JPH0729716A - Plastic magnet and treatment method thereof - Google Patents

Abstract

PURPOSE:To provide an electronic lens magnet which is manufactured at a low cost and excellent in magnetic properties and moldability and a treating method thereof. CONSTITUTION:Plastic magnet material containing 30 to 70% by weight of magnet powder which is mainly composed of iron, aluminum, nickel, and cobalt and as large in average grain diameter as 40 to 100mum is molded into a plastic magnet. Provided that a final magnetization value is 100%, a plastic magnet is magnetized higher than a final magnetization value b 110 to 140% in a primary magnetizing process, then magnetized lower than a final magnetization value by -10 to -30% in a second magnetizing process so as to be kept equal in remanence to a final magnetization value, and then subjected to an aging process at a temperatures of 80 to 120 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic magnet and a method for treating the same.

[0002]

2. Description of the Related Art As a magnet for convergence or centering in a cathode ray tube (CRT),
Conventionally, alnico magnets are often used. Alnico magnets are, as is well known, iron (Fe)
), Aluminum (Al), nickel (Ni) and cobalt (Co) as the main components. The cobalt component contained in this type of general alnico magnet is usually about 24 to 34%. However, cobalt is expensive, and therefore, an alnico magnet containing a large amount of cobalt component becomes expensive.

On the other hand, ferrite magnets are often used especially for high frequencies. The powder particle size of this magnet is about 0.5 to 3 μm. Ferrite magnets have the characteristics of good magnetic stability and large coercive force, but have the drawback of severely deteriorating their characteristics due to temperature changes (high temperatures) and limiting their applications. FIG. 7 shows changes in magnetic force with respect to ambient temperature. The change in magnetic force due to the temperature change of the Alnico magnet is indicated by the characteristic line 71.
0.02% / ° C. as shown in FIG. 7, whereas that of the ferrite magnet is 0.02% as shown by the characteristic line 72.
It is about 2% / ° C., which is an order of magnitude larger than that of Alnico magnets. It should be noted that the straight line 70 shows a reference line with no change.

The content of magnet powder in plastic magnets is generally about 70% in the case of ferrite type magnets and about 30% in the case of alnico type magnets. Conventionally, the content has not been diversified. No (content is fixed), the diversification of magnetic characteristics is supported by the magnetization process. Further, conventionally, the magnetic stabilizing treatment is not performed in the case of the ferrite magnet, but only the stabilizing demagnetization or heat aging of about 5% is performed in the case of the alnico magnet.

Here, a commonly used method of magnetizing a plastic magnet will be described.

Now, consider a general BH characteristic of a magnet as shown in FIG. The horizontal axis represents the magnetomotive force Hc, and the vertical axis represents the magnetization amount Br. When the predetermined amount of magnetization is A, the ferrite type magnet is not used for (1) full magnetization, but is magnetized according to the characteristic lines 81 and 82. In the case of an alnico magnet, (2) first, full magnetization B is performed according to the characteristic lines 81 and 83, and then demagnetization processing is performed to obtain the magnetization amount of A.

Therefore, the magnetizing method (1) is not always used with the rated coercive force Hc.

The stabilized demagnetization rate should be minimized. The reason is that if the demagnetization rate is high, it is necessary to increase the amount of primary magnetization, but this leads to an increase in the amount of magnet powder contained, which is disadvantageous in terms of cost. Nevertheless, the relationship between the stabilized demagnetization rate and the cost has not been considered so far.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a plastic magnet which can be manufactured at a lower cost and has excellent magnetic properties and moldability, and a method for treating the plastic magnet.

[0010]

In order to achieve the above object, the plastic magnet of the present invention comprises a magnet containing iron, aluminum and nickel as main components and having an average particle diameter of 40 to 100 μm in a weight ratio of 30 to 30. 7
It was molded from a plastic magnet material containing 0%.

Further, the plastic magnet of the present invention contains 10% of the cobalt component of an alnico magnet mainly containing iron, aluminum, nickel and cobalt.
The following is formed by a plastic magnet material containing 30 to 70% by weight of magnet powder having an average particle diameter of 40 to 100 μm.

Furthermore, in the method for treating a plastic magnet according to the present invention, when the final magnetizing amount of the magnet according to claim 1 or 2 is 100%, the primary magnetizing amount is 1
After being magnetized as high as 10 to 140%, it becomes 10 by secondary magnetization.
It is characterized by demagnetizing to 0% and further aging at a temperature of 80 to 120 ° C.

[0013]

FUNCTION AND EXAMPLE The magnet according to the present invention is made of iron,
It is molded from a plastic magnet material containing aluminum and nickel and, if necessary, cobalt-based magnet powder having an average particle size of 40 to 100 μm in a weight ratio of 30 to 70%.

Between the magnetic characteristics and the moldability of this type of plastic magnet, there is a contradictory tendency regarding the particle size of the magnet powder. As shown in FIG.
Has a function of increasing function with respect to the particle size, while the formability 22 has a function of decreasing function with the particle size. As described above, there is a contradictory tendency between the magnetic characteristics and the formability of the magnet regarding the particle size of the magnet powder. The average particle diameter of the magnet powder according to the present invention of 40 to 100 μm is selected as a region that simultaneously satisfies both the magnetic characteristics and the formability. Fig. 1 shows the relationship between the average particle size of magnet powder, magnetic properties, and moldability (Koka type flow).
Shown in. FIG. 1 shows the relationship between the particle size and B · Hmax in a low-cobalt alnico magnet (content rate 50%), where the left side of the vertical axis is B · Hmax, and the right side of the vertical axis is an elevation flow. The horizontal axis represents the average particle size of the magnet powder. Here, B · Hmax is the magnetization amount B
And the magnetomotive force H of the product B · H. In the present invention, the average particle size of the magnet powder is 40-100.
The range of μm is that the range is magnetic characteristics B · Hmax
This is because it was determined that the Koka type flow characteristically exists in a practically coexisting region.

Next, the content of the magnet powder is 30 to 7
By adjusting the magnetic flux density within the range of 0%, the magnetic flux density of the final product can be adjusted over a wide range, so that a magnet having a high magnetic flux density characteristic from a magnet with a low required magnetic flux density to a magnet with a high magnetic flux density It can be handled by a kind of magnet. As shown in FIG. 3, when the magnet powder content is large (70%), a large magnetization amount shown by the characteristic line 31 can be obtained, and when the magnet powder content is small (30%), the characteristic line 32 is obtained.
As shown by, the magnetization amount also becomes small. Assuming that the demagnetization rate for stabilizing the magnetic force is -10% to -30%, the primary magnetization amount is 110 to 110 when the predetermined magnetization amount is 100%.
According to the present invention, one type of magnet can be applied to models with a high magnetic force (straight line 33) to models with a low magnetic force (straight line 34), which is 140%.
Each saturation magnetic force can also be secured.

Even in the case of an alnico type magnet, the coercive force against an external magnetic field can be set to a level at which there is no problem in practice, if appropriate magnetic force stabilizing demagnetization is performed.

FIG. 4 shows the characteristics of the alnico magnet with respect to the external magnetic field (AC magnetic field). Fig. 4 shows a ring-shaped 4-pole magnet without stabilizing demagnetization (characteristic line 4
1), demagnetization rate-10% (characteristic line 42), demagnetization rate-30%
(Characteristic line 43), demagnetization rate of -50% (characteristic line 44) and demagnetization rate of -70% (characteristic line 45), the rate of change in magnetic force measured was shown as a function of the distance L between the magnet and the degausser. It is a thing. For reference, a characteristic line 46 shows a measurement result of a fully magnetized ferrite magnet. As can be seen from the figure, the external magnetic field characteristics of Alnico magnets are generally specified to be within 5% demagnetization when left (irradiated) for 10 seconds in an alternating magnetic field of 90 Gauss (G). ,
It can be seen that the magnet according to the invention clears it sufficiently. It is better to minimize the stabilizing demagnetization rate. As described above, if the demagnetization rate is high, it is necessary to increase the primary magnetizing amount, but this leads to an increase in the amount of magnet powder contained, which is disadvantageous in terms of cost.

The magnetic flux density of the final product is adjusted by primary magnetization (normal magnetization) and secondary magnetization (demagnetization), but as shown in FIG. 3, when the content of magnet powder is large. A large amount of magnetization can be obtained, and when the content of magnet powder is small, the amount of magnetization also becomes small. However, the constant magnetizing characteristics obtained under the condition that the magnet powder content is constant, for example, the adjustment work for obtaining the predetermined magnetizing quantity according to the characteristic line 51 of "high content" in FIG. It is difficult to perform the adjustment work in a standing portion, that is, in a place where the variation width of the magnetization voltage corresponding to the predetermined variation amount of the magnetization is “narrow”. By adjusting the content of the magnet powder according to the present invention, it is possible to easily obtain a magnetized product having an appropriate magnetizing amount characteristic. Therefore, the adjustment work for obtaining a predetermined magnetizing amount should be carried out by the part where the characteristic is particularly outstanding. Even if the magnet powder content is large (characteristic line 51) or small (characteristic line 52), a relatively wide range of the variation of the magnetization voltage corresponding to the predetermined variation in the amount of magnetization is used. It is possible to easily adjust and obtain a stable amount of magnetization.

Next, the reason why the content of cobalt in the magnet containing cobalt is 10% or less will be described. When the magnetic properties of various magnet materials containing cobalt (Co) were compared, the results shown in Table 1 were obtained. In Table 1, Br is a magnetizing magnetic flux and bHc is a magnetomotive force. (B · H) max indicates the maximum value of the product B · H of the magnetic flux density B and the magnetomotive force H. As shown in Table 1, the product having a high Co content (No. 2) and the product having a low Co content (No. 5) among the five kinds of materials show almost the same magnetic characteristics, and thus the low Co product. However, it turns out that it will be fully practical.

[0020]

[Table 1] Furthermore, according to the present invention, the amount of magnetization in the end use is 100%.
As a result, after the primary magnetization amount is set to a high value of 110 to 140%, the secondary magnetization is demagnetized to 100%, and then 80 to
Aging is performed at a temperature of 120 ° C. By thus performing the double magnetic stabilization treatment, the magnetic stability can be improved. Aging temperature 80-120 ℃
Is due to the following reasons.

The temperature inside the set of a color television, a display or the like (for example, the temperature at the portion where the convergence magnet is attached) changes depending on the distance from the heater inside the CRT neck, the space condition inside the set, the heat radiation condition, etc. In the case of ° C, it rises to about 80-110 ° C. Also, the heat deformation temperature of the magnet, which varies depending on the content of the magnet powder and the blending degree of the flame retardant or flame retardant auxiliary agent, is usually about 140 to 160 ° C, and the safety degree is 15 to If 25% is expected, the maximum aging temperature will be around 120 ° C. Incidentally, 100
It has been put to practical use by aging at a temperature of ℃.

FIG. 6 shows the characteristics of various alnico magnets over time, that is, the elapsed time and the change in magnetic force. Characteristic line 61 is the one without stabilization treatment, characteristic line 62
Is the one after only a little demagnetization treatment, characteristic line 6
3 shows the case where both demagnetization processing and aging processing were performed, and the characteristic line 64 shows the case where too much demagnetization processing was performed, respectively. What we can see is
This means that the time-dependent characteristics of the magnet can be made closer to ideal by performing appropriate demagnetization processing and appropriate aging processing (characteristic line 63).

[0023]

As described above in detail, according to the present invention, it is possible to inexpensively provide a plastic magnet having excellent magnetic characteristics and moldability.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the average particle size and magnetic properties and moldability.

FIG. 2 is a diagram generally showing the relationship between the average particle size and the magnetic properties and formability.

FIG. 3 is a diagram showing the relationship between the content of magnet powder and the magnetization characteristics.

FIG. 4 is a diagram showing an external magnetic field characteristic of an alnico magnet.

FIG. 5 is a diagram for explaining a method of adjusting a magnetizing amount of a magnet.

FIG. 6 is a diagram showing a time-dependent characteristic of magnetic force of an alnico magnet.

FIG. 7 is a diagram showing a relationship between ambient temperature of a magnet and magnetic force.

FIG. 8 is a diagram for explaining a general magnetizing method for magnets.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01J 29/64 A H04N 9/28 D 9187-5C

Claims (3)

[Claims] 1. A plastic magnet formed of a plastic magnet material containing 30 to 70% by weight of magnet powder having an average particle diameter of 40 to 100 μm of a magnet containing iron, aluminum and nickel as main components. 2. A plastic magnet containing 10% or less of a cobalt component of an alnico magnet containing iron, aluminum, nickel and cobalt as main components, and 30 to 70% by weight of magnet powder having an average particle diameter of 40 to 100 μm. Plastic magnet molded from material. 3. The magnet according to claim 1 or 2,
When the final magnetization amount is 100%, the primary magnetization amount is 110
After being magnetized as high as ~ 140%, 100% by secondary magnetization
Demagnetization and further aging at a temperature of 80 to 120 ° C. is a method for treating a plastic magnet.