JP2006298725A - Ni-BASED FERRITE, AND MAGNETIC CORE OF TRANSMISSION TRANSFORMER FOR POWER LINE COMMUNICATION - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an Ni-based ferrite having a high saturation magnetic flux density and a high magnetic permeability. <P>SOLUTION: The Ni-based ferrite used for constituting a magnetic core 20 of a transmission transformer for power line communication has a fundamental composition comprising, by mol, 48-50% Fe<SB>2</SB>O<SB>3</SB>, 10-33% ZnO, 0-12% CuO, and ≥19% NiO. After sintering, the content of crystals having diameters of ≤5 μm is ≤30% expressed in terms of area. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a Ni-based ferrite and a magnetic core of a transmission transformer for power line communication using the same.

Currently, a transmission transformer for signal transmission is provided in an electronic device for high-speed communication used for broadband or the like. For the magnetic cores of these transmission transformers, Mn—Zn ferrite having good direct current superposition characteristics is often used (see, for example, Patent Document 1). However, since the specific resistance of Mn—Zn ferrite is as small as about 10 Ωm, in the case of a large magnetic core made of Mn—Zn ferrite, the influence of the skin effect increases as the signal frequency increases. is there. For this reason, it is difficult to use Mn—Zn-based ferrite as a magnetic core of a large transmission transformer applied to a power line having a diameter of several tens of mm or more, which is necessary for transmission of characters, images, and sounds using an existing power line. It is. In particular, when transmitting a high-frequency signal (for example, 2 MHz to 40 MHz) necessary for high-speed communication, the effect of the skin effect becomes larger. Therefore, a transmission transformer for performing high-speed power line communication with Mn—Zn ferrite is used. It is very difficult to use as a magnetic core. Therefore, conventionally, it has been proposed to configure a magnetic core of a transmission transformer for power line communication with Ni-based ferrite having a large specific resistance of 10 ⁶ Ωm and a small skin effect.

  However, the conventional general Ni-based ferrite has a low saturation magnetic flux density and a low magnetic permeability, so that there is a problem that the signal attenuation is increased in a transmission transformer using a magnetic core made of Ni-based ferrite. .

The present invention has been made to solve the above-described problems, and one object of the present invention is to provide a Ni-based ferrite having a high saturation magnetic flux density and a high magnetic permeability.
Another object of the present invention is to provide a magnetic core of a transmission transformer for power line communication made of Ni-based ferrite having a high saturation magnetic flux density and high magnetic permeability.

JP 2004-196632 A

Means for Solving the Problems and Effects of the Invention

To achieve the above object, a result of the present inventors have studied intensively, _Fe 2 _{O 3} is less 48 mol% or more 50 mol%, ZnO is less 10 mol% or more 33 mol%, CuO is more than 0 mol% 12 mol% or less, NiO is 19mol % Of the basic composition and the content of crystals with a grain size of 5 μm or less after firing is 30% or less in terms of area, thereby increasing the saturation magnetic flux density to increase the permeability and change the permeability. It has been found that a Ni-based ferrite with a small amount can be produced. That is, in the Ni-based ferrite according to the first aspect of the present invention, Fe ₂ O ₃ is 48 mol% to 50 mol%, ZnO is 10 mol% to 33 mol%, CuO is 0 mol% to 12 mol%, and NiO is 19 mol% or more. The content ratio of crystals having a crystal grain size of 5 μm or less after firing is 30% or less in terms of area.

In the Ni-based ferrite according to the first aspect, as described above, the content of NiO is 19 mol% or more, and the content of crystals having a crystal grain size after firing of 5 μm or less is 30% or less in terms of area. As a result, the saturation magnetic flux density can be increased and the decrease in the magnetic permeability at a high bias level when an AC bias magnetic field is applied can be suppressed. The amount of change can be reduced. That is, in the first aspect, by suppressing the decrease in magnetic permeability at a high bias level (high magnetic flux density) when an AC bias magnetic field is applied by increasing the saturation magnetic flux density by setting the NiO content to 19 mol% or more. A grain boundary that reduces the number of small crystals having a grain size of 5 μm or less and prevents magnetization by reducing the content of crystals having a grain size after firing of 5 μm or less to 30% or less in terms of area. The decrease in the magnetic permeability at a high bias level when an AC bias magnetic field is applied can also be suppressed by reducing the number of The amount of change can be reduced. Thereby, in the transformer having a magnetic core made of the Ni-based ferrite of the present invention, a signal can be stably transmitted using an AC power supply. Incidentally, by the content of Fe ₂ O ₃ more than 48 mol%, it is possible to increase the saturation magnetic flux density, which also, at high bias levels at the time of applying an AC bias magnetic field (high magnetic flux density) A decrease in magnetic permeability can be suppressed. Moreover, since the coercive force can be lowered by making the content of Fe ₂ O ₃ 50 mol% or less, this also makes it possible to achieve a high bias level (high magnetic flux density) when an AC bias magnetic field is applied. A decrease in magnetic permeability can be suppressed. Further, by making the content of _Fe 2 _{O 3} below 50 mol%, it is possible to increase the specific resistance. Thereby, since the influence of the skin effect can be suppressed, a high-frequency signal can be transmitted even in a large magnetic core. In addition, since the initial permeability can be increased by setting the content of ZnO to 10 mol% or more, the effective permeability can be increased even when a gap is formed in the magnetic core made of this Ni-based ferrite, The transmission efficiency of signal transmission can be increased. Moreover, since Curie temperature can be raised by making content of ZnO 33 mol% or less, practicality can be improved. Moreover, a saturation magnetic flux density can be raised by making content of CuO into 12 mol% or less.

  In the Ni-based ferrite according to the first aspect described above, the content of crystals having a crystal grain size after firing of 5 μm or less is preferably 20% or less in terms of area. With such a configuration, small crystals having a grain size of 5 μm or less after firing can be further reduced, and therefore the number of crystal grain boundaries that hinder the magnetization of Ni-based ferrite can be further reduced. Thereby, the fall of the magnetic permeability in the high bias level when an alternating current bias magnetic field is applied can be suppressed more.

  In the Ni-based ferrite according to the first aspect, the average crystal grain size after firing of the Ni-based ferrite is preferably 5 μm or more and 30 μm or less. In this way, by setting the average crystal grain size of Ni-based ferrite to 5 μm or more, it is possible to reduce crystals with a small crystal grain size, thereby reducing the number of grain boundaries that hinder the magnetization of Ni-based ferrite. Can do. Thereby, the magnetic permeability when an AC bias magnetic field is applied can be increased. Further, when the average crystal grain size of the Ni-based ferrite is set to 30 μm or less, abnormal grain growth of crystals can be prevented. Thereby, it is possible to prevent the transformer magnetic core made of Ni-based ferrite from being damaged due to abnormal grain growth of crystals.

  In the Ni-based ferrite according to the first aspect, the average crystal grain size after firing of the Ni-based ferrite is preferably 5 μm or more and 10 μm or less. Thus, if the average crystal grain size after firing Ni-based ferrite is made 10 μm or less, abnormal grain growth of the crystal can be further prevented, so that the magnetic core of the transformer made of Ni-based ferrite has abnormal grain growth of the crystal. It is possible to further suppress damage due to the damage.

The magnetic core of the transmission transformer for power line communication according to the second aspect of the present invention has Fe ₂ O ₃ of 48 mol% to 50 mol%, ZnO of 10 mol% to 33 mol%, CuO of 0 mol% to 12 mol%, and NiO of 19 mol. % Of the basic composition, and the content of the crystals having a crystal grain size after firing of 5 μm or less is 30% or less in terms of area.

As described above, the magnetic core of the transmission transformer for power line communication according to the second aspect of the present invention has a NiO content of Ni-based ferrite of 19 mol% or more and a crystal grain size after firing of 5 μm or less. By making the content 30% or less in terms of area, it is possible to increase the saturation magnetic flux density and to suppress a decrease in permeability at a high bias level when an AC bias magnetic field is applied. The amount of change in magnetic permeability when a bias magnetic field is applied can be reduced. That is, in the second aspect, by reducing the content of NiO to 19 mol% or higher, the saturation magnetic flux density is increased and an AC bias magnetic field is applied to suppress a decrease in magnetic permeability at a high bias level (high magnetic flux density). A grain boundary that reduces the number of small crystals having a grain size of 5 μm or less and prevents magnetization by reducing the content of crystals having a grain size after firing of 5 μm or less to 30% or less in terms of area. The decrease in the magnetic permeability at a high bias level when an AC bias magnetic field is applied can also be suppressed by reducing the number of The amount of change can be reduced. Thereby, in the transformer having the magnetic core of the transmission transformer for power line communication of the present invention, it is possible to stably transmit a signal using an AC power source. Incidentally, by the content of Fe ₂ O ₃ more than 48 mol%, it is possible to increase the saturation magnetic flux density, which also, at high bias levels at the time of applying an AC bias magnetic field (high magnetic flux density) A decrease in magnetic permeability can be suppressed. Further, by making the content of _Fe 2 _{O 3} below 50 mol%, it is possible to increase the specific resistance. Thereby, since the influence of the skin effect can be suppressed, a high-frequency signal can be transmitted even in a large magnetic core. In addition, since the initial permeability can be increased by making the content of ZnO 10 mol% or more, the effective permeability can be increased even when a gap is formed in the magnetic core of the transmission transformer for power line communication, The transmission efficiency of signal transmission can be increased. Moreover, since Curie temperature can be raised by making content of ZnO 33 mol% or less, practicality can be improved. Moreover, a saturation magnetic flux density can be raised by making content of CuO into 12 mol% or less.

  In the magnetic core of the transmission transformer for power line communication according to the second aspect, preferably, the Ni-based ferrite has a thickness of 5 mm or more. Thus, even in the case of the magnetic core of a large power line communication transmission transformer having a thickness of 5 mm or more, if the Ni-based ferrite according to the second aspect is used, the amount of change in magnetic permeability can be reduced.

  In the magnetic core of the transmission transformer for power line communication according to the second aspect, preferably, the content of crystals having a crystal grain size after firing of Ni-based ferrite of 5 μm or less is 20% or less in terms of area. With such a configuration, small crystals having a grain size of 5 μm or less after firing can be further reduced, and therefore the number of crystal grain boundaries that hinder the magnetization of Ni-based ferrite can be further reduced. Thereby, the fall of the magnetic permeability in the high bias level when an alternating current bias magnetic field is applied can be suppressed more.

  In the magnetic core of the transmission transformer for power line communication according to the second aspect, the average crystal grain size of the Ni-based ferrite is preferably 5 μm or more and 30 μm or less. In this way, by setting the average crystal grain size of Ni-based ferrite to 5 μm or more, it is possible to reduce crystals with a small crystal grain size, thereby reducing the number of grain boundaries that hinder the magnetization of Ni-based ferrite. Can do. Thereby, the magnetic permeability when an AC bias magnetic field is applied can be increased. Further, when the average crystal grain size of the Ni-based ferrite is set to 30 μm or less, abnormal grain growth of crystals can be prevented. Thereby, it can suppress that the magnetic core of the transmission transformer for power line communications is damaged by the abnormal grain growth of a crystal.

  In the magnetic core of the transmission transformer for power line communication according to the second aspect, the average crystal grain size after firing of the Ni-based ferrite is preferably 5 μm or more and 10 μm or less. Thus, if the average crystal grain size after firing of the Ni-based ferrite is set to 10 μm or less, abnormal grain growth of the crystal can be further prevented, so that the magnetic core of the transmission transformer for power line communication contributes to the abnormal grain growth of the crystal. It can suppress more that it is damaged.

  Examples of the present invention will be described below.

  In the present application, as an example corresponding to the present invention, a magnetic core of a power line communication transmission transformer made of Ni-based ferrite according to Examples 1 to 5 below is manufactured, and the following Comparative Examples 1 to Comparative Examples are used as comparative examples. The magnetic core of the transmission transformer for power line communication which consists of Ni system ferrite by 5 was produced. When the magnetic core of the power line communication transmission transformer is used for power line communication, as shown in FIG. 1, the magnetic cores 1 and 2 of the power line communication transmission transformer 10 each have a commercial power source (AC power source) corresponding to the primary coil. ) And the like, and the signal line 6 connected to the modem 5 corresponding to the secondary coil is passed. In the power line communication transmission transformer 10 having such a configuration, a high frequency signal of several MHz to several tens of MHz sent on a commercial power supply (for example, an AC power supply having a frequency of 50 Hz or 60 Hz) is transmitted from the power lines 3 and 4. Transmitted on line 6;

[Manufacture of magnetic core for transmission transformer for power line communication using Ni-based ferrite]
Example 1
First, in Example 1, _Fe 2 _{O 3} is 49.4Mol% of the main component composition ratio of Ni ferrite, ZnO is 27.4 mol%, NiO is mixed raw material powder so as to 23.2mol%, 800 Calcination was carried out in the atmosphere at 3 ° C for 3 hours. Next, this calcined calcined powder was wet-pulverized by a ball mill until the average crystal grain size became about 1.0 μm, and then dried. Next, the polyvinyl alcohol solution is added to the powder and granulated so that the mass ratio of the dried powder and the 7% by mass polyvinyl alcohol solution is 100: 14, and then dried to have an average particle diameter of 150 μm. The following granulated powder was produced. Next, this granulated powder was compressed to a density of 3.1 g / cm ³ with a pressure of 1.5 ton / cm ² using a mold press, and formed into a ring shape. For this molded product, the cross-sectional area of a crystal whose average crystal grain size is 10 μm in the magnetic core after firing and whose crystal grain size is 5 μm or less with respect to the cross-sectional area of all crystal grains in a predetermined cross-section of the magnetic core is converted into a circular area. Firing was carried out in air at 1250 ° C. for 3 hours so that the content of the finished area was 20%. Thus, as shown in FIG. 2, the magnetic core 20 of the transmission transformer for power line communication according to the first embodiment, which is made of ring-shaped Ni-based ferrite having an outer diameter of 30 mm, an inner diameter of 20 mm, and an axial length of 12 mm, is produced. did. That is, in Example 1, a ring type magnetic core 20 having a thickness of 5 mm (= (30−20) / 2) was produced. In addition, the average crystal grain size and the content ratio of the area converted to a circular area of the crystal having a crystal grain size of 5 μm or less were measured using a cross section of the magnetic core after being subjected to mirror polishing and chemical etching. Moreover, converting the cross-sectional area into a circle area means that the cross-sectional area is calculated by regarding the cross-section of the crystal grain as a circle.

(Example 2)
In Example 2, and the Ni-based _Fe 2 _{O 3} in the main component composition ratio of the ferrite is 49.7mol%, ZnO is 31.1mol%, NiO was mixed raw material powder so that 19.2 mol%, In the magnetic core after firing, the content ratio of the area obtained by converting the cross-sectional area of a crystal having an average crystal grain size of 10 μm and a crystal grain size of 5 μm or less with respect to the cross-sectional area of all crystal grains in a predetermined cross-section of the magnetic core into a circular area A magnetic core 20 of a transmission transformer for power line communication made of Ni-based ferrite was produced using the same process as in Example 1 except that firing was performed in the atmosphere of 1230 ° C. for 3 hours so as to be 20%.

(Example 3)
In Example 3, Ni-based _Fe 2 _{O 3} is 48.7Mol% of the main component composition ratios of the ferrite, ZnO is 20.5mol%, CuO is 6.1mol%, the raw material so NiO is 24.7Mol% The cross-sectional area of a crystal having an average crystal grain size of 10 μm and a crystal grain size of 5 μm or less with respect to the cross-sectional area of all crystal grains in a predetermined cross-section of the magnetic core in the magnetic core after firing is mixed with the powder. The core of the transmission transformer for power line communication made of Ni-based ferrite was used by using the same process as in Example 1 except that it was fired in the atmosphere at 1150 ° C. for 3 hours so that the converted area content was 20%. 20 was produced.

Example 4
In Example 4, Ni-based _Fe 2 _{O 3} is 48.6Mol% of the main component composition ratios of the ferrite, ZnO is 23.8mol%, CuO is 6.2 mol%, the raw material so NiO is 21.5 mol% The cross-sectional area of a crystal having an average crystal grain size of 10 μm and a crystal grain size of 5 μm or less with respect to the cross-sectional area of all crystal grains in a predetermined cross-section of the magnetic core in the magnetic core after firing is mixed with the powder. The core of the transmission transformer for power line communication made of Ni-based ferrite was used by using the same process as in Example 1 except that it was fired in the atmosphere at 1150 ° C. for 3 hours so that the converted area content was 20%. 20 was produced.

(Example 5)
In Example 5, Ni-based _Fe 2 _{O 3} is 49.2Mol% of the main component composition ratios of the ferrite, ZnO is 15.6mol%, CuO is 3.6 mol%, the raw material so NiO is 31.6Mol% The cross-sectional area of a crystal having an average crystal grain size of 10 μm and a crystal grain size of 5 μm or less with respect to the cross-sectional area of all crystal grains in a predetermined cross-section of the magnetic core in the magnetic core after firing is mixed with the powder. The core of the transmission transformer for power line communication made of Ni-based ferrite was used by using the same process as in Example 1 except that it was fired in the atmosphere at 1150 ° C. for 3 hours so that the converted area content was 20%. 20 was produced.

(Comparative Example 1)
In Comparative Example 1, and the Ni-based _Fe 2 _{O 3} in the main component composition ratio of the ferrite is 48.8mol%, ZnO is 33.2mol%, NiO was mixed raw material powder so that 18.0 mol%, In the magnetic core after firing, the content ratio of the area obtained by converting the cross-sectional area of a crystal having an average crystal grain size of 8 μm and a crystal grain size of 5 μm or less with respect to the cross-sectional area of all crystal grains in a predetermined cross-section of the magnetic core into a circular area A magnetic core 20 of a transmission transformer for power line communication made of Ni-based ferrite was produced using the same process as in Example 1 except that it was fired in the atmosphere of 1200 ° C. for 3 hours so as to be 30%.

(Comparative Example 2)
In Comparative Example 2, and the Ni-based _Fe 2 _{O 3} in the main component composition ratio of the ferrite is 49.8mol%, ZnO is 32.7mol%, NiO was mixed raw material powder so that 17.5%, In the magnetic core after firing, the average crystal grain size is 7 μm, and the content ratio of the area obtained by converting the cross-sectional area of a crystal having a crystal grain size of 5 μm or less with respect to the cross-sectional area of all crystal grains in a predetermined cross-section of the magnetic core into a circular area A magnetic core 20 of a transmission transformer for power line communication made of Ni-based ferrite was produced using the same process as in Example 1 except that firing was performed in an atmosphere of 1200 ° C. for 3 hours so as to be 30%.

(Comparative Example 3)
In Comparative Example 3, Ni-based _Fe 2 _{O 3} is 49.8Mol% of the main component composition ratios of the ferrite, ZnO is 32.2mol%, CuO is 5.8 mol%, the raw material so NiO is 12.1Mol% The cross-sectional area of a crystal having an average crystal grain size of 12 μm and a crystal grain size of 5 μm or less with respect to the cross-sectional area of all the crystal grains in a predetermined cross-section of the magnetic core in the magnetic core after being mixed with the powder The core of the transmission transformer for power line communication made of Ni-based ferrite using the same process as in Example 1 except that it was fired in the atmosphere at 1200 ° C. for 3 hours so that the converted area content was 10%. 20 was produced.

(Comparative Example 4)
In Comparative Example 4, Ni-based _Fe 2 _{O 3} is 48.4Mol% of the main component composition ratios of the ferrite, ZnO is 31.5 mol%, CuO is 5.8 mol%, the raw material so NiO is 14.2Mol% The cross-sectional area of a crystal having an average crystal grain size of 10 μm and a crystal grain size of 5 μm or less with respect to the cross-sectional area of all crystal grains in a predetermined cross-section of the magnetic core in the magnetic core after firing is mixed with the powder. The core of the transmission transformer for power line communication made of Ni-based ferrite was used by using the same process as in Example 1 except that it was fired in the atmosphere at 1150 ° C. for 3 hours so that the converted area content was 20%. 20 was produced.

(Comparative Example 5)
In Comparative Example 5, and that the Ni-based _Fe 2 _{O 3} in the main component composition ratio of the ferrite is 49.4mol%, ZnO is 27.4 mol%, NiO was mixed raw material powder so that 23.2Mol%, In the magnetic core after firing, the average crystal grain size is 7 μm, and the content ratio of the area obtained by converting the cross-sectional area of a crystal having a crystal grain size of 5 μm or less with respect to the cross-sectional area of all crystal grains in a predetermined cross-section of the magnetic core into a circular area A magnetic core 20 of a transmission transformer for power line communication made of Ni-based ferrite was produced using the same process as in Example 1 except that it was fired in the atmosphere at 1050 ° C. for 3 hours so as to be 40%.

[Saturation magnetic flux density and permeability measurement test]
The saturation magnetic flux density of the magnetic cores according to Examples 1 to 5 and Comparative Examples 1 to 5 produced as described above was measured. Further, a primary loop and a secondary coil are both wound around the magnetic cores of Examples 1 to 5 and Comparative Examples 1 to 5 30 times, and a minor loop of Bm = 100 mT by an AC BH tracer (Iwasaki Tsushinki Co., Ltd.). Then, an AC bias magnetic field corresponding to a minor loop of 100 mT was applied, and the permeability under the AC bias magnetic field was measured. The results are shown in Table 1 below and FIG.

In Table 1 above, Bms indicates the saturation magnetic flux density, μ _MAX indicates the maximum magnetic permeability in the minor loop, and μ _{BIAS = 0} indicates the magnetic permeability when the AC bias magnetic field is 0 (hereinafter referred to as the reference magnetic permeability). Μ _MIN indicates the minimum magnetic permeability in the minor loop. FIG. 3 shows the ratio of the saturation magnetic flux density (Bms) of the magnetic cores of Examples 1 to 5 and Comparative Examples 1 to 5 to the maximum permeability and the reference permeability (μ _MAX / μ _{BIAS = 0} ). FIG. 6 is a correlation diagram showing a relationship between a ratio of minimum magnetic permeability and reference magnetic permeability (μ _MIN / μ _{BIAS = 0} ). Hereinafter, with reference to Table 1 and FIG. 3, the measurement result of the saturation magnetic flux density and the magnetic permeability of Examples 1 to 5 and Comparative Examples 1 to 5 will be described.

As is clear from Table 1, in Examples 1 to 5, the content of crystals having a NiO content of 19.2 mol% or more and a crystal grain size after firing of 5 μm or less is 20 in terms of area. %, The saturation magnetic flux density Bms (370 mT or more) of Examples 1 to 5 was changed to the saturation magnetic flux density of Comparative Examples 1 to 4 (excluding Comparative Example 5 having a NiO content of 23.2 mol%). Bms (330 mT or less) can be increased, and a decrease in permeability (minimum permeability μ _MIN ) at a high bias level when an AC bias magnetic field is applied is suppressed as compared with Comparative Examples 1 to 5. Therefore, the difference in magnetic permeability ratio AB in Examples 1 to 5 (0.19 or less) is changed to the difference in magnetic permeability ratio AB in Comparative Examples 1 to 5 (0. 23 or more). Therefore, in Example 1 to Example 5, compared with Comparative Examples 1 to 5, the amount of change in magnetic permeability when an AC bias magnetic field is applied can be reduced. That is, in Examples 1 to 5, the content of NiO is set to 19.2 mol% or more, thereby increasing the saturation magnetic flux density Bms and applying an AC bias magnetic field at a high bias level (high magnetic flux density). A decrease in magnetic permeability (permeability μ _MIN ) can be suppressed, and the crystal grain size after firing is reduced to 5% by converting the content of crystals having a crystal grain size of 5 μm or less to 20% in terms of area. By reducing the number of crystal grain boundaries that hinder magnetization by reducing the crystal, it is possible to suppress a decrease in the magnetic permeability (minimum magnetic permeability μ _MIN ) at a high bias level when an AC bias magnetic field is applied. Because of these synergistic effects, the amount of change in magnetic permeability when an AC bias magnetic field is applied can be reduced. Thereby, in the transmission transformer for power line communication which has a magnetic core of Example 1- Example 5, a signal can be stably transmitted using AC power supply.

  In Examples 1 to 5, since the average crystal grain size of the Ni-based ferrite can be reduced to 10 μm, crystals having a small crystal grain size can be reduced. The number of can be reduced. Thereby, the magnetic permeability when an AC bias magnetic field is applied can be increased. In Examples 1 to 5, abnormal grain growth of crystals can be prevented by setting the average crystal grain size of Ni-based ferrite to 10 μm. Thereby, it is possible to prevent the transformer magnetic core made of Ni-based ferrite from being damaged due to abnormal grain growth of crystals.

[Manufacture of gap cores for transmission transformers for power line communication using Ni-based ferrite]
(Example 6)
In Example 6, a pair of semi-cylindrical magnetic core pieces 21a and 21b as shown in FIG. 4 were produced using the same process as in Example 1 described above. And the sealing materials 22a and 22b are arranged in the gap provided between the magnetic core pieces 21a and 21b, and the ring shape has an outer diameter of 100 mm, an inner diameter of 60 mm, and an axial length of 20 mm, and A ring-type magnetic core 30 having an initial effective magnetic permeability of 70 H / m was produced. That is, in Example 6, a ring-type magnetic core 30 having a thickness of 20 mm (= (100-60) / 2) was produced.

(Comparative Example 6)
In Comparative Example 6, magnetic core pieces 21a and 21b similar to those in Example 6 are manufactured using the same process as in Comparative Example 3, and the same shape as that of Example 6 is used using the magnetic core pieces 21a and 21b. A magnetic core was prepared.

(Comparative Example 7)
In Example 7, using the same process as in Comparative Example 4, magnetic core pieces 21a and 21b similar to those in Example 6 were produced, and using the magnetic core pieces 21a and 21b, the same shape as in Example 6 was used. A magnetic core was prepared.

  Measurement of main component composition, average crystal grain size, ratio of crystal grain size of 5 μm or less, and effective magnetic permeability of magnetic core 30 constituting magnetic core pieces 21a and 21b according to Example 6 and Comparative Examples 6 and 7 described above The test results are shown in Table 2 below.

[Measurement test of effective permeability]
The effective permeability when an AC bias magnetic field was applied was measured in the state where the primary coil and the secondary coil were both wound 30 times around the magnetic cores of Example 6 and Comparative Examples 6 and 7 produced as described above. The result is shown in FIG. The effective magnetic permeability is an effective magnetic permeability of the magnetic core 30 including the magnetic core pieces 21a and 21b and the sealing materials 22a and 22b functioning as magnetic gaps.

  FIG. 5 shows the relationship between the AC bias magnetic field applied to the magnetic cores of Example 6 and Comparative Examples 6 and 7 and the effective magnetic permeability. Hereinafter, Example 6 and Comparative Examples 6 and 7 will be described with reference to FIG.

As shown in FIG. 5, the maximum magnetic permeability of Example 6 and Comparative Examples 6 and 7 are 9.3 × 10 ⁻⁵ H / m, 9.3 × 10 ⁻⁵ H / m, and 9.2 ×, respectively. The value was almost the same as 10 ⁻⁵ H / m. On the other hand, the minimum magnetic permeability of Example 6 in which the NiO content is as high as 23.2 mol% and the crystal content of 5 μm or less is 20% in terms of area ratio is 4.5 × 10 ⁻⁵ H / m. In contrast, the minimum permeability of Comparative Examples 6 and 7 in which the NiO content is as low as 15 mol% or less and the crystal content of 5 μm or less is 10% and 20% in area ratio, respectively, It was as low as 3.4 × 10 ⁻⁵ H / m and 1.3 × 10 ⁻⁵ H / m. That is, in Example 6, the amount of change in magnetic permeability accompanying the change in the AC bias magnetic field (AC current) (9.3 × 10 ⁻⁵ −4.5 × 10 ⁻⁵ = 4.8 × 10 ⁻⁵ H / m). ) Is small, in Comparative Examples 6 and 7, the amount of change in magnetic permeability (9.3 × 10 ⁻⁵ −3.4 × 10 ⁻⁵ = 5.9 × in accordance with the change in the AC bias magnetic field (alternating current)). 10 ⁻⁵ H / m and 9.2 × 10 ⁻⁵ −1.3 × 10 ⁻⁵ = 7.9 × 10 ⁻⁵ H / m). From this result, even in the case of a magnetic core provided with a magnetic gap, the content of NiO is 19 mol% or more (23.2 mol%) and the content of crystals of 5 μm or less is 20% or more. Since the amount of change in effective permeability when a bias magnetic field is applied can be reduced, it has been found that signals can be stably transmitted using an AC power supply.

  In addition, it should be thought that the Example disclosed this time is an illustration and restrictive at no points. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes meanings equivalent to the scope of claims for patent and all modifications within the scope.

  For example, in Examples 1 to 6 described above, an example in which the content ratio of crystals having a crystal grain size of Ni-based ferrite of 5 μm or less is 20% in terms of area ratio is not limited to this. What is necessary is just to make it the content rate of the crystal | crystallization with a crystal grain diameter of 5 micrometers or less of a system ferrite becoming 30% or less by an area ratio. In this way, by reducing the content of crystals having a crystal grain size of 5 μm or less after firing to 30% or less in terms of area, the number of small crystals having a crystal grain size of 5 μm or less is reduced, thereby preventing the grain boundary from interfering with magnetization. Since the number can be reduced, it is possible to suppress a decrease in magnetic permeability at a high bias level when an AC bias magnetic field is applied. Thereby, the amount of change in magnetic permeability when an AC bias magnetic field is applied can be reduced.

  In Examples 1 to 6, the example in which the average crystal grain size of the Ni-based ferrite is 10 μm is shown. However, the present invention is not limited to this, and the average crystal grain size of the Ni-based ferrite is 5 μm to 30 μm. The following is sufficient. In this way, by setting the average crystal grain size of Ni-based ferrite to 5 μm or more, it is possible to reduce crystals with a small crystal grain size, thereby reducing the number of grain boundaries that hinder the magnetization of Ni-based ferrite. Can do. Thereby, the magnetic permeability when an AC bias magnetic field is applied can be increased. Further, when the average crystal grain size of the Ni-based ferrite is set to 30 μm or less, abnormal grain growth of crystals can be prevented. Thereby, it is possible to prevent the transformer magnetic core made of Ni-based ferrite from being damaged due to abnormal grain growth of crystals.

  Moreover, in the said Example 1- Example 6, although content of NiO was set to 19.2 mol% or more, this invention is not restricted to this, If the content of NiO is 19 mol% or more, it will be the same effect. Can be obtained.

In the Examples 1 to 6 has been set the content of _Fe 2 _{O 3} to 48.6mol% ~49.7mol%, the present invention is not limited thereto, the content of _Fe 2 _{O 3} What is necessary is just to set to 48 mol% or more and 50 mol% or less. Since the saturation magnetic flux density Bms can be increased by setting the content of Fe ₂ O ₃ to 48 mol% or more in this way, this also provides a high bias level (high magnetic flux density) when an AC bias magnetic field is applied. The decrease in the magnetic permeability (minimum magnetic permeability μ _MIN ) can be suppressed. Moreover, since the coercive force can be lowered by making the content of Fe ₂ O ₃ 50 mol% or less, this also makes it possible to achieve a high bias level (high magnetic flux density) when an AC bias magnetic field is applied. A decrease in magnetic permeability μ _MIN can be suppressed. Moreover, since the coercive force can be lowered by making the content of Fe ₂ O ₃ 50 mol% or less, this also makes it possible to achieve a high bias level (high magnetic flux density) when an AC bias magnetic field is applied. A decrease in magnetic permeability can be suppressed. Further, by making the content of _Fe 2 _{O 3} below 50 mol%, it is possible to increase the specific resistance. Thereby, since the influence of the skin effect can be suppressed, a high-frequency signal can be transmitted even in a large magnetic core having a thickness of 5 mm or more.

  Moreover, in the said Example 1- Example 6, although content of ZnO was set to 15.6 mol%-31.1 mol%, this invention is not restricted to this, Content of ZnO is 10 mol% or more and 33 mol% or less Should be set. In this way, by setting the ZnO content to 10 mol% or more, the initial permeability can be increased. Therefore, even if a gap is formed in the magnetic core, the effective permeability can be increased and the transmission efficiency of signal transmission can be increased. Can be increased. Moreover, since Curie temperature can be raised by making content of ZnO 33 mol% or less, practicality can be improved.

  Moreover, in the said Example 1- Example 6, although content of CuO was set to 0 mol%-6.2 mol%, this invention is set not only to this but CuO content to 0 mol% or more and 12 mol% or less do it. Thus, saturation magnetic flux density can be raised by making content of CuO into 12 mol% or less.

  Moreover, in the said Example 1- Example 6, although the example of the magnetic core which has a thickness of 5 mm and 20 mm was shown, this invention is not limited to this, The large-sized magnetic core which has other thickness of 5 mm or more is also shown. It is possible to apply.

  Moreover, in the said Example 1- Example 6, although the example of the cylindrical-shaped magnetic core was shown, this invention is not limited to this, For example, the magnetic core formed in the ring shape is cut | disconnected using an outer peripheral blade cutting device etc. By doing so, the outer shape of the magnetic core may be a hexagonal shape or a rectangular shape. By adopting such a shape, the magnetic core is difficult to roll and alignment is facilitated, so that the magnetic core can be easily attached.

It is a perspective view which shows an example of the transmission transformer for power line communications by the Example of this invention. It is a perspective view which shows the magnetic core of the transmission transformer for power line communication of Example 1- Example 5 and Comparative Examples 1-5. It is a correlation diagram which shows the relationship between the saturation magnetic flux density measured with respect to Example 1- Example 5 and Comparative Examples 1-5, and the ratio of magnetic permeability. It is a perspective view which shows the magnetic core with a gap of the transmission transformer for power line communication by Example 6 and Comparative Examples 6 and 7. It is a correlation diagram which shows the relationship between the alternating current bias magnetic field measured with respect to Example 6 and Comparative Examples 6 and 7, and effective magnetic permeability.

Explanation of symbols

1, 2, 20, 30 Magnetic core 3, 4 Power line 5 Modem 6 Signal line 10 Power line communication transmission transformers 21a, 21b Magnetic core pieces 22a, 22b Sealing material

Claims (9)

Fe ₂ O ₃ has a basic composition of 48 mol% to 50 mol%, ZnO 10 mol% to 33 mol%, CuO 0 mol% to 12 mol%, NiO 19 mol% or more,
Ni-based ferrite having a crystal content after firing of 5 μm or less and a crystal content of 30% or less in terms of area.   2. The Ni-based ferrite according to claim 1, wherein the content of crystals having a crystal grain size after firing of 5 μm or less is 20% or less in terms of area.   3. The Ni-based ferrite according to claim 1, wherein an average crystal grain size after firing of the Ni-based ferrite is 5 μm or more and 30 μm or less.   The Ni-based ferrite according to claim 3, wherein the average crystal grain size after firing of the Ni-based ferrite is 5 µm or more and 10 µm or less. Fe ₂ O ₃ has a basic composition of 48 mol% to 50 mol%, ZnO 10 mol% to 33 mol%, CuO 0 mol% to 12 mol%, NiO 19 mol% or more, and the crystal grain size after firing is 5 μm or less. The core of a transmission transformer for power line communication, which is made of Ni-based ferrite having a crystal content of 30% or less in terms of area.   The magnetic core of the transmission transformer for power line communication according to claim 5, wherein the Ni-based ferrite has a thickness of 5 mm or more.   The magnetic core of the transmission transformer for power line communication according to claim 5 or 6, wherein a content ratio of crystals having a crystal grain size of 5 µm or less after firing of the Ni-based ferrite is 20% or less in terms of area.   The magnetic core of the transmission transformer for power line communication according to any one of claims 5 to 7, wherein an average crystal grain size after firing of the Ni-based ferrite is 5 µm or more and 30 µm or less. The Ni-based ferrite according to claim 8, wherein the average crystal grain size after firing of the Ni-based ferrite is 5 µm or more and 10 µm or less.

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