JP7278787B2 - magnetic material - Google Patents

Description

The present invention relates to magnetic materials.

Magnetic materials, which are ceramics, are classified into manganese-zinc ferrite (Mn--Zn-based ferrite), nickel-zinc-based ferrite (Ni--Zn-based ferrite), and the like, depending on the composition of the main component including iron oxide. Of these, Mn--Zn ferrite has a smaller magnetic loss (hereinafter sometimes referred to as core loss) than Ni--Zn ferrite, and can easily improve DC weight characteristics. It is used as a material for the core of the coil element of In general, the core of the coil element is manufactured by molding weighed and mixed powdery raw materials using a mold and firing the molded body.

By the way, in recent years, electric vehicles such as hybrid cars and electric vehicles, which can be driven by a motor, have become widespread. In such electric vehicles, for example, the high voltage of about 200V to 300V handled by the running battery, which is the power source for driving the motor, is changed to the low voltage of about 14V to operate the onboard electronic equipment (air conditioner, audio, etc.). It has a DC-DC converter for conversion.

In order to improve the voltage conversion efficiency of the DC-DC converter, it is also necessary to reduce the core loss of the transformer mounted in the DC-DC converter. Furthermore, unlike transformers for general power supply applications, transformers for DC-DC converters installed in electric vehicles can withstand a wide range of temperatures, not just the ambient temperature where the DC-DC converter is installed in the vehicle. Low core loss is required in the range.

Specifically, DC-DC converters for electric vehicles operate in a temperature range from about 25°C to about 40°C (hereinafter sometimes referred to as the room temperature range) when the load is low. Since the ambient temperature rises, it exhibits stable performance even in a temperature range from about 100°C to about 140°C, which is the upper limit of the design specifications (hereinafter sometimes referred to as the high temperature range). There is a need. Therefore, transformers mounted in such DC-DC converters are required to have low loss over a wide temperature range from room temperature to high temperatures.

FIG. 1 shows general temperature characteristics of a coil element having a core made of a magnetic material whose main component is Mn--Zn ferrite. In FIG. 1, the horizontal axis indicates temperature (° C.), and the vertical axis indicates core loss (kW/m ³ ) when the coil element is excited with a sine wave of 100 kHz-200 mT. As shown in FIG. 1, the core loss temperature characteristic curve has a trough shape that minimizes the core loss at a certain temperature. Incidentally, Patent Document 1 and Non-Patent Document 1 below describe a technique of adding an appropriate amount of CoO to Mn—Zn ferrite in order to reduce the temperature dependence of core loss. In addition, the following Non-Patent Document 2 describes the characteristics of Mn—Zn ferrite materials, which are magnetic materials mainly composed of conventional Mn—Zn ferrite, and the characteristics of cores of coil elements using the magnetic materials. is described. Patent Document 2 below describes a magnetic material in which CaCO ₃ and SiO ₂ are added to Mn—Zn ferrite.

JP 2005-119892 A JP-A-2001-155915

Akira Fujita, Satoshi Goto, ``MnZn ferrite with low core loss over a wide temperature range'' Kawasaki Steel Technical Report Vol.34 No.3 2002 FDK Corporation, "Development of new Mn-Zn ferrite material ``6H60T'' that achieves the industry's lowest level of low core loss -Launch of industry standard core shape ``UU79/129A''-", [online], [Heisei 30 Searched September 27, 2016], Internet <URL: http://www.fdk.co.jp/whatsnew-j/release20160411-j.html>

FIG. 1 shows the relationship between core loss and temperature for Mn--Zn ferrite materials including the Mn--Zn ferrite material described in Patent Document 1. FIG. In order to reduce the core loss over a wide temperature range, it is necessary to reduce the temperature dependence of the core loss as shown in FIG. Therefore, it is conceivable to reduce the core loss on the low temperature side by increasing the amount of CoO that is included as an additive in the magnetic material. However, even if the amount of CoO added is increased or decreased while maintaining the composition of the main component, the valley-shaped characteristic shown in FIG. Range cannot lower core loss.

Non-Patent Document 1 describes a magnetic material with low temperature dependence of core loss. However, in electric vehicles, it is assumed that the DC-DC converter will be used in a high temperature environment of about 140°C. The magnetic material described in Non-Patent Document 1 has a core loss of 400 kW/m ³ or more at a temperature of 140°C. Moreover, the minimum value of core loss is about 300 kW/m ³ , and it is difficult to say that the core loss is extremely low.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a magnetic material having a small core loss over a wide temperature range.

In one aspect of the present invention for achieving the above object, a Mn—Zn ferrite composed of Fe ₂ O ₃ , ZnO, and MnO is used as a main component, and CoO, TiO ₂ , and CaO are added as subcomponents. A magnetic material added to the main component,
The main component contains 53.45 mol% or more and 53.75 mol% or less of the Fe ₂ O ₃ and 10.05 mol% or more and 10.65 mol% or less of the ZnO, and the balance is the MnO,
The CoO is contained at a ratio of 0.38 wt% or more and 0.46 wt% or less in terms of Co ₂ O ₃ with respect to the main component,
The TiO ₂ is contained at a ratio of 0.15 wt% or more and 0.40 wt% or less with respect to the main component,
The CaO is contained in a ratio of 0.03 wt% or more in terms of CaCO ₃ with respect to the main component,
The core loss is the minimum value at a temperature of 40 ° C. or less, and the core loss at a temperature of 140 ° C. is 350 kW / m ³ or less.
A magnetic material characterized by:

The above magnetic materials include:
ZrO ₂ is included as the secondary component at a ratio of 0.02 wt% or more and 0.05 wt% or less with respect to the main component,
Sb ₂ O ₃ may be included as the secondary component at a rate of 0.09 wt % or less with respect to the main component.

ADVANTAGE OF THE INVENTION According to this invention, the magnetic material with small core loss in a wide temperature range is provided. Other effects will be clarified in the following description.

1 is a diagram showing general temperature characteristics of a magnetic material containing Mn—Zn ferrite as a main component; FIG. 4 is a flow chart showing a procedure for producing a magnetic material according to an example of the present invention;

=== Example ===
Considering that the magnetic material according to the embodiment of the present invention is used for the core of a transformer mounted in a DC-DC converter mounted on an electric vehicle, , Core loss is low in the temperature range up to about 140°C, which is assumed to be the temperature of a DC-DC converter that generates heat under high load. The magnetic material according to the example has Mn—Zn ferrite composed of Fe ₂ O ₃ , ZnO, and MnO as the main component, and CoO and TiO ₂ are added as subcomponents to the main component. The composition of the main component and the added amount of the subcomponent are optimized.

<Process of conceiving the present invention>
Addition of CoO to Mn--Zn ferrite, which is the main component of the magnetic material, reduces the temperature dependence of the magnetic material. That is, the difference between the maximum value and the minimum value of core loss is small, and the characteristic curve of core loss with respect to temperature has a flat shape as shown in FIG. In the knowledge obtained in the process of conceiving the present invention, in the Mn—Zn ferrite composed of Fe ₂ O ₃ , ZnO, and MnO, when the ratio of Fe ₂ O ₃ and ZnO is insufficient, the room temperature The core loss increases in the high temperature range, and when the proportions of Fe ₂ O ₃ and ZnO are excessive, the core loss increases in the high temperature range. Further, in a magnetic material containing Mn--Zn ferrite as a main component, adding about 0.40 wt % of CoO in terms of Co ₂ O ₃ can suppress an increase in core loss at low temperatures. Furthermore, when the amount of TiO ₂ added is insufficient, the temperature at which the core loss is minimized does not fall below 40° C., and when the amount of TiO ₂ added is excessive, the core loss increases in the high temperature range.

Therefore, the present inventor optimized the ratio of Fe ₂ O ₃ and ZnO in the main component and the amount of TiO ₂ added as a secondary component, and added CoO to the main component in terms of Co ₂ O ₃ If it is possible to suppress the increase in core loss in the room temperature range while adding about 0.40 wt% at, it is possible to produce a magnetic material with low loss in a wide temperature range from the room temperature range of 40 ° C. or less to the high temperature range of about 140 ° C. I thought I could do it. The present invention has been accomplished as a result of intensive research based on the above findings and considerations.

=== Optimization of magnetic material composition ===
In order to determine the optimum composition of the magnetic material according to the embodiment of the present invention, various magnetic materials with different compositions of main components and additives were produced, and sintered bodies obtained by firing the magnetic materials were used as samples. bottom. Then, the core loss in the temperature range of 25° C. to 140° C. was measured for each sample.

<Sample preparation method>
FIG. 2 shows the procedure for preparing samples. As shown in FIG _. 2, the sample preparation procedure adopted here _is as follows. were weighed, and these ferrite raw materials were mixed using a ball mill or the like (S1).

Next, the raw material mixture of the main components is calcined at a temperature of about 900 ° C. (S2), and the powder obtained by the calcination (hereinafter sometimes referred to as calcined powder) is subjected to a predetermined amount using a ball mill. (S3). Then, titanium oxide (TiO ₂ ) and cobalt oxide III (Co ₂ O ₃ ), which is the source of CoO, are mixed with the calcined powder after pulverization in amounts corresponding to the sample as subcomponent raw materials, and the mixture is were mixed in a mortar (S4). In this embodiment, in the step (S4) of mixing raw materials for the subcomponents, in addition to Co ₂ O ₃ and TiO ₂ , trace amounts of zirconium oxide (ZrO ₂ ) and antimony trioxide (Sb ₂ O ₃ ) are added. Appropriate amount is added as an additive. ZrO ₂ is an additive for increasing the grain boundary resistance. If the amount added is too small, the effect will not be obtained, and if the amount added is too large, the resistivity of ferrite will decrease and the core loss will increase. ZrO ₂ is preferably added in an amount of about 0.03 wt % to 0.04 wt % with respect to the main component. The optimum amount of Sb ₂ O ₃ to be added is about 0.03 wt % to 0.07 wt % with respect to the main component, and the addition of an appropriate amount of Sb ₂ O ₃ densifies the structure of the sample and reduces core loss. be able to.

In addition, in the subcomponent addition/mixing step (S4), an appropriate amount of calcium carbonate (CaCO ₃ ), which is a source of calcium oxide (CaO), and silicon dioxide (SiO ₂ ) are added together with the subcomponent raw materials. there is CaO and SiO ₂ increase the resistivity of the magnetic material and reduce core loss.

In addition, in the conventional ferrite material, when adding SiO ₂ , the amount of SiO ₂ added is about 0.01 wt % or less. Although 0.005 wt % of SiO ₂ is added to all the samples here, SiO ₂ does not significantly affect the temperature characteristics of core loss.

On the other hand, the amount of CaO added in terms of CaCO ₃ is about 0.05 to 0.15 wt% in conventional ferrite materials, but at least the lower limit of the amount of CaO added is the core loss at 140 ° C. It is necessary to set a target to reduce the amount to a predetermined value or less. Here, the target is to set the core loss at 140° C. to 350 kW/m ³ or less. Since the temperature characteristics of the core loss also depend on the size of the core, etc., it is difficult to uniquely define the upper limit of the amount of CaO to be added.

As will be described later, the amount of CaO added in terms of CaCO ₃ is an annular shape (toroidal ring shape), the size is φ25 mm, and the surface including the axial direction and the diametrical direction of the annular ring is cut. It has been found that even for a core with a cross-sectional area of about 25 mm ² when it is dry, an addition amount of 0.03 wt % or more is necessary. It is believed that if the amount of CaO added is less than 0.03 wt % in terms of CaCO ₃ , the electrical resistance decreases and the eddy current loss increases, thereby worsening the core loss. In the following, unless otherwise specified, 0.08 wt % of CaO in terms of CaCO ₃ is added to all samples.

Next, 1 wt % of PVA was added as a binder to the mixture of the calcined powder of the main component and the raw material of the subcomponent, and granulation was carried out so that the particle diameter was appropriately large (S5). Further, the granules were formed into the toroidal ring-shaped core described above using a mold (S6). Then, the molded body was fired at a maximum temperature of about 1300° C. for 3 hours at a predetermined oxygen concentration (S7) to obtain a sintered body as a sample.

<Examination of the composition of the main component>
In the above-described sample preparation procedure, the present inventor first prepared samples of sintered bodies composed of 25 types of magnetic materials having different ratios of Fe ₂ O ₃ , ZnO, and MnO, which are raw materials of Mn—Zn ferrite. 1-25. Then, the core loss Pcv (kW/m ³ ) when each of samples 1 to 25 was subjected to sinusoidal excitation at 100 kHz-200 mT using an AC BH analyzer was measured in the temperature range of 25 ° C to 140 ° C. .

Table 1 below shows the manufacturing conditions of samples 1 to 25 and the temperature characteristics of core loss in each sample.

表１において、サンプル１～２５は、いずれも副成分の添加（Ｓ４）に際して、ＴｉＯ_２の添加量を０．３０ｗｔ％、ＣｏＯの添加量をＣｏ_２Ｏ_３換算で０．４０ｗｔ％としている。また、表１では、コアロスの最大値と最小値、及び最大値と最小値のそれぞれが測定されたときの温度を示した。なお、表１では、参考までに、温度依存性という数値を示した。温度依存性は、コアロスの最大値から最小値を減算した値を、コアロスが最大となる温度からコアロスが最小となる温度を減算した値で除算して求めた値の絶対値であり、例えば、図１に示したコアロスの温度特性曲線の平坦度を示す指標となる。そして、温度依存性の数値は、温度特性の平坦度が増すほど、すなわち、コアロスの最大値と最小値との差が小さいほど、あるいはコアロスが最大値となる温度とコアロスが最小値となる温度との差が大きいほど小さくなる。

In Table 1, samples 1 to 25 all have a TiO ₂ addition amount of 0.30 wt % and a CoO addition amount of 0.40 wt % converted to Co ₂ O ₃ when adding subcomponents (S4). Table 1 also shows the temperatures at which the maximum and minimum values of core loss and the maximum and minimum values were measured. In addition, in Table 1, the numerical value of temperature dependence was shown for reference. Temperature dependence is the absolute value of the value obtained by dividing the value obtained by subtracting the minimum value from the maximum value of core loss by the value obtained by subtracting the temperature at which core loss is minimum from the temperature at which core loss is maximum. It is an index showing the flatness of the temperature characteristic curve of the core loss shown in FIG. The numerical value of the temperature dependence increases as the flatness of the temperature characteristics increases, that is, as the difference between the maximum and minimum values of core loss decreases, or the temperature at which core loss reaches its maximum value and the temperature at which core loss reaches its minimum value. becomes smaller as the difference between

Here, considering that the magnetic material described in Non-Patent Document 1 had a maximum core loss value of 400 kW / m ³ at a temperature of 140 ° C., 90% of the core loss value (400 kW / m ³ ) When 350 kW / m ³ , which is less than 350 kW / m 3, is used as a standard for judging the superiority of core loss characteristics, as shown in Table 1, samples 1 to 25 all have the maximum core loss at a temperature of 140 ° C., and the sample 1, 2, 4, 5, 7 to 19, 22, and 23 exhibited excellent core loss characteristics with a core loss of 350 kW/m ³ or less. Samples 3, 6, 20, 21, 24, and 25 had a core loss exceeding 350 kW/ ^m3 .

Among samples 1, 2, 4, 5, 7 to 19, 22, and 23, samples other than samples 22 and 23 exhibited the lowest core loss at a temperature of 40° C. or lower. In addition, Samples 2, 4, 7, 8, 10, 12, 13, 15, 16, 17, 18, and 21 showed the lowest core loss at a temperature of 25°C. In samples 3, 6, 24, and 25, the temperature at which core loss was minimized was 60°C, and in samples 22 and 23, the temperature at which core loss was minimized was 80°C.

Then, from the compositions of samples 1, 2, 4, 5, and 7 to 19, which had a maximum core loss of 350 kW / m ³ or less and a temperature at which the core loss was the minimum value of 40 ° C. or less, the main component was A magnetic material comprising a certain Mn—Zn ferrite having an Fe ₂ O ₃ content of 53.45 mol% or more and 53.75 mol% or less, a ZnO content of 10.05 mol% or more and 10.65 mol% or less, and the balance being MnO. It was found that the maximum value of core loss in the temperature range of 25 to 140° C. can be reduced to 350 kW/m ³ or less, and the core loss is minimized in the room temperature range of 40° C. or less. Also, the average temperature dependence of samples 1, 2, 4, 5, and 7 to 19 was 1.05.

<Examination of the amount of subcomponents to be added>
Next, in order to examine the appropriate additive amount of the subcomponents, sample 26 was a sintered body composed of 30 kinds of magnetic materials with different additive amounts of CoO and TiO ₂ in the sample preparation procedure shown in FIG. ~55. The compositions of the main components of Samples 26-55 are Fe ₂ O ₃ based on the median values of the proportions of Fe ₂ O ₃ and ZnO in Samples 1, 2, 4, 5, and 7-19 in Table 1. was 53.60 mol %, ZnO was 10.35 mol %, and the remaining 36.05 mol % was MnO. Then, the temperature characteristics of the core loss of each sample were investigated.

Table 2 below shows the manufacturing conditions and temperature characteristics of Samples 26 to 55.

表２に示したように、サンプル２６～５５の全てにおいて、１４０℃の温度下でコアロスが最大となった。そして、サンプル２７～３１、３４～３８、４２、４６、４７、５０、５１、及び５３は、コアロスの最大値が３５０ｋＷ／ｍ^３以下であり、コアロスが最小となるときの温度が４０℃以下であり、さらに、サンプル２７～３１、３４、３６、４７、及び５０～５２では、コアロスが最小となるときの温度が２５℃であった。また、サンプル２６～３２、３５～５１、及び５３では、コアロスの最小値が２５０ｋＷ／ｍ^３以下であった。そして、表２において、コアロスの最大値が３５０ｋＷ／ｍ^３以下であり、コアロスが最小となるときの温度が４０℃以下であったサンプル２７～３１、３４～３８、４２、４６、４７、５０、５１、及び５３の温度依存性の平均値は、０．９８であり、表１における同様の特性を有するサンプル１、２、４、５、及び７～１９の温度依存性の平均値の１．０５よりも１．００に近かった。したがって、主成分とともに副成分の添加量が適切に調整された磁性材料は、より平坦な温度特性を有しているということが分かった。

As shown in Table 2, all samples 26 to 55 had the maximum core loss at a temperature of 140°C. Samples 27 to 31, 34 to 38, 42, 46, 47, 50, 51, and 53 have a maximum core loss of 350 kW/ ^m3 or less, and a temperature at which the core loss is minimized is 40°C or less. and in samples 27-31, 34, 36, 47, and 50-52, the temperature at which the core loss was minimized was 25°C. In samples 26-32, 35-51, and 53, the minimum value of core loss was 250 kW/m ³ or less. Then, in Table 2, samples 27 to 31, 34 to 38, 42, 46, 47, and 50 in which the maximum value of core loss was 350 kW/m ³ or less and the temperature at which the core loss was minimized was 40 ° C. or less. , 51, and 53 is 0.98, which is one of the average temperature dependencies of samples 1, 2, 4, 5, and 7-19 in Table 1, which have similar properties. It was closer to 1.00 than .05. Therefore, it was found that a magnetic material in which the addition amounts of subcomponents as well as the main component are appropriately adjusted has flatter temperature characteristics.

<Study on trace additives>
As described above, the magnetic materials according to the embodiments of the present invention also contain ZrO ₂ and Sb ₂ O ₃ as additives, albeit in very small amounts. For example, the various samples described above contained 0.04 wt % of ZrO ₂ and 0.05 wt % of Sb ₂ O ₃ with respect to the main component. It should be noted that trace additives such as ZrO ₂ and Sb ₂ O ₃ are not intentionally added too little or too much. Therefore, the amount of the trace additive added does not affect the temperature characteristics of the magnetic material unless it is too little or too much.

On the other hand, considering ease of process control in the manufacturing process of the magnetic material, it is better not to strictly define the addition amount of the trace additive. Therefore, samples 56 to 70 were produced as sintered bodies composed of 15 kinds of magnetic materials with different amounts of ZrO ₂ and Sb ₂ O ₃ added, and the temperature characteristics of each sample were evaluated. In this case, the sample production conditions were also constant except for the addition amount of the trace additive. Specifically, the main components of the various samples are Mn—Zn ferrite with a ratio of Fe ₂ O ₃ of 53.60 mol %, a ratio of ZnO of 10.35 mol %, and the remaining 36.05 mol % of MnO. , 0.30 wt % TiO ₂ and 0.40 wt % CoO in terms of Co ₂ O ₃ were added as subcomponents.

Table 3 below shows the manufacturing conditions and temperature characteristics of samples 56 to 70.

表３に示したように、サンプル５６～７０の全てにおいても、１４０℃の温度下でコアロスが最大となった。

As shown in Table 3, all samples 56 to 70 also showed the maximum core loss at a temperature of 140°C.

Samples 58 to 60 and 63 to 67 had a maximum core loss of 350 kW/m ³ or less, and a temperature at which the core loss was minimized was 40° C. or less. In samples 56-60 and 63-70, the minimum value of core loss was 250 kW/m ³ or less. Then, in Table 3, the average value of the temperature dependence of samples 58 to 60 and 63 to 67, in which the maximum core loss was 350 kW/m ³ or less and the temperature at which the core loss was minimized was 40 ° C. or less. is 1.26, compared to the mean value of 0.98 for the temperature dependence of samples 27-31, 34-38, 42, 46, 47, 50, 51, and 53 with similar properties in Table 2. As a result, the flatness of the temperature characteristics was lost. However, the amount of ZrO ₂ added to the main component should be 0.02 to 0.05 wt%, and the amount of Sb ₂ O ₃ to be added should be 0.00 to 0.09 wt%. . That is, if the amount of ZrO ₂ or Sb ₂ O ₃ added to the main component is within the above range, the magnetic material according to the embodiment of the present invention can exhibit the above effects. Since there is no need to strictly control the amount of additive added, process control can be easily performed in the production process of the magnetic material.

<Optimum amount of CaO to be added>
As described above, it is necessary to determine the lower limit of the addition amount of CaO in terms of _CaCO3 . Therefore, sintered bodies composed of four types of magnetic materials with different amounts of CaCO ₃ added were produced as samples 71 to 74, and the temperature characteristics of each sample were evaluated. Except for the addition amount of the trace additive, the sample preparation conditions were kept constant. Specifically, the main components of the various samples are Mn—Zn ferrite with a ratio of Fe ₂ O ₃ of 53.60 mol %, a ratio of ZnO of 10.35 mol %, and the remaining 36.05 mol % of MnO. , 0.30 wt % TiO ₂ and 0.40 wt % CoO in terms of Co ₂ O ₃ were added as subcomponents. Also, 0.04 wt % and 0.05 wt % of ZrO ₂ and Sb ₂ O ₃ were added to the main component, respectively.

Table 4 below shows the relationship between the amount of CaCO ₃ added and the temperature characteristics in Samples 71-74.

以上より、本発明の実施例に係る磁性材料は、５３．４５ｍｏｌ％以上５３．７５ｍｏｌ％以下のＦｅ_２Ｏ_３と、１０．０５ｍｏｌ％以上１０．６５ｍｏｌ％以下のＺｎＯとを含むとともに、残部がＭｎＯからなるＭｎ－Ｚｎ系フェライトを主成分とし、副成分として、ＣｏＯが、主成分に対し、Ｃｏ_２Ｏ_３換算で０．３８ｗｔ％以上０．４６ｗｔ％以下の割合で添加され、ＴｉＯ_２が、主成分に対し、０．１５ｗｔ％以上０．４０ｗｔ％以下の割合で添加され、ＣａＯがＣａＣＯ_３換算で０．０３ｗｔ％以上添加されてなる。

As described above, the magnetic material according to the example of the present invention contains 53.45 mol % or more and 53.75 mol % or less of Fe ₂ O ₃ and 10.05 mol % or more and 10.65 mol % or less of ZnO, and the balance is Mn—Zn ferrite made of MnO is the main component, CoO is added as an auxiliary component at a rate of 0.38 wt % or more and 0.46 wt % or less in terms of Co ₂ O ₃ with respect to the main component, and TiO ₂ is added. , is added at a rate of 0.15 wt% or more and 0.40 wt% or less with respect to the main component, and CaO is added at 0.03 wt% or more in terms of _CaCO3 .

Furthermore, ZrO ₂ is added at a ratio of 0.02 wt% or more and 0.05 wt% or less with respect to the main component, and Sb ₂ O ₃ is added at a ratio of 0.00 wt% or more and 0.09 wt% or less with respect to the main component. By adding , a magnetic material having the above temperature characteristics can be produced more reliably.

For example, when the magnetic material according to the embodiment is applied to the core of a coil element such as a transformer mounted on a circuit board of a DC-DC converter mounted on an electric vehicle or a hybrid car, the DC-DC converter can be widely used. It operates stably and with high efficiency in the operating environment of the temperature range. Such a low-loss core over a wide temperature range can reduce power consumption of a coil element including the core and a DC-DC converter in which the coil element is mounted. Moreover, the core manufactured using the magnetic material according to the embodiment has a small core loss, and the coil element including the core hardly generates heat. Therefore, even if the size of the coil element is specified when designing the DC-DC converter, the size of the coil element can be flexibly set by using the magnetic material according to the embodiment for the core of the coil element. can. In particular, even if the design specifies a small coil element with a small surface area that is difficult to dissipate heat, the core made of the magnetic material according to the above embodiment that has a small core loss in the expected wide operating temperature range is provided. By using the coil element, it is possible to achieve miniaturization of the coil element while raising the operating temperature of the coil element.

In addition, in the magnetic materials according to the above examples, a predetermined amount of SiO ₂ was added as an auxiliary component. ) may be appropriately added in order to adjust to the required numerical range. Also, the upper limit of the amount of CaO to be added may be appropriately set in order to adjust the properties other than the temperature properties of the magnetic material within the desired numerical range.

The description of the above-described embodiments is intended to facilitate understanding of the present invention, and does not limit the technical scope of the present invention. The present invention can be modified and improved without departing from the spirit of the above embodiments, and the present invention includes equivalents thereof.

The magnetic materials according to the above-described embodiments can be applied not only to cores of transformers mounted on circuit boards of DC-DC converters, but also to cores of other coil elements such as toroidal cores. Of course, the magnetic material according to the embodiment may be used for electronic components that require low core loss properties from room temperature to high temperature.

S1 Weighing/mixing step of main components, S2 Temporary firing step, S3 Crushing step, S4 Addition/mixing step of subcomponents, S5 Granulation step, S6 Molding step, S7 Firing step,

Claims (2)

A magnetic material containing Mn—Zn ferrite consisting of Fe ₂ O ₃ , ZnO, and MnO as a main component, and a secondary component containing CoO, TiO ₂ , and CaO added to the main component,
The main component contains 53.45 mol% or more and 53.75 mol% or less of the Fe ₂ O ₃ and 10.05 mol% or more and 10.65 mol% or less of the ZnO, and the balance is the MnO,
The CoO is contained at a ratio of 0.38 wt% or more and 0.46 wt% or less in terms of Co ₂ O ₃ with respect to the main component,
The TiO ₂ is contained at a ratio of 0.15 wt% or more and 0.40 wt% or less with respect to the main component,
The CaO is contained in a ratio of 0.03 wt% or more in terms of CaCO ₃ with respect to the main component,
The core loss is the minimum value at a temperature of 40 ° C. or less, and the core loss at a temperature of 140 ° C. is 350 kW / m ³ or less.
A magnetic material characterized by: A magnetic material according to claim 1,
ZrO ₂ is included as the secondary component at a ratio of 0.02 wt% or more and 0.05 wt% or less with respect to the main component,
Sb ₂ O ₃ is contained as the secondary component at a ratio of 0.09 wt% or less with respect to the main component,
A magnetic material characterized by:

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