JP6901990B2 - Heat resistance High magnetic permeability MnZn ferrite - Google Patents

Description

The present invention relates to a heat resistant high magnetic permeability MnZn ferrite.

In recent years, _{the need for CO 2} emission reduction and energy saving has increased, and in-vehicle devices such as hybrid vehicles and electric vehicles have been electrified, and studies for clearing noise regulations related to in-vehicle devices are underway.

Above all, it has been clarified that common mode noise is generated from the inverter and the motor in the electric compressor, and the need for noise countermeasures using an AC line filter or the like is increasing.

Conventionally, in order to suppress noise generated from a power supply line of a television, an air conditioner, or the like, a common mode choke coil such as an AC line filter has been developed. Particularly in recent years, in order to enhance the noise attenuation capability in the region of 150 kHz to several MHz, the magnetic permeability of MnZn ferrite (sintered body), which is the magnetic core material (core) of the AC line filter, has been improved and the magnetic permeability has been improved with respect to the frequency. Development has been carried out to enhance.

MnZn ferrite, which has been developed as a magnetic core material for AC line filters, mainly has a Curie temperature of about 120 ° C. in order to increase the initial magnetic permeability near room temperature, and in a high temperature range exceeding this temperature. It could not function as a line filter in applications such as in-vehicle devices used.

On the other hand, in Patent Document 1, by controlling the basic component composition of ferrite and suppressing the amount of carbon remaining in ferrite to a predetermined value or less, the initial permeability at 10 kHz in a wide temperature range of -20 to 150 ° C. Mn-Zn-Co-based ferrites with increased magnetic permeability are disclosed. Further, Patent Document 2 discloses Mn—Zn—Co-based ferrite in which a trace amount of MgO is further added and the amount of carbon remaining in the ferrite is suppressed to a predetermined value or less. These technologies are considered to be effective technologies for equipment used in a high temperature range.

Japanese Unexamined Patent Publication No. 2015-229626 JP-A-2015-229625

On the other hand, electronic components used especially for in-vehicle use not only have temporary magnetic characteristics in a high temperature environment, but also maintain their performance even when used continuously for a long period of time in a high temperature environment of 100 ° C. or higher, for example. High durability is also required. However, until now, such durability has not been evaluated including the above patent documents.

In view of the above problems, the present invention provides a heat-resistant high magnetic permeability MnZn ferrite with a small decrease in the initial high relative initial magnetic permeability even when continuously used for a long period of time in a high temperature environment of 100 ° C. or higher. The purpose.

The heat-resistant high magnetic permeability MnZn ferrite according to the present invention is
MnZn ferrite whose main components are Fe ₂ O _{3 and Zn O and Mn O.}
Fe ₂ O ₃ was contained in an amount of 50.50 to 54.00 mol%, ZnO was contained in an amount of 11.00 to 18.00 mol%, and the balance of MnO was contained in a total amount of 100 mol%.
When the total amount of the main component is 100 parts by mass, Co ₂ O ₃ is 0.10 to 0.55 parts by mass, TiO ₂ is 0.10 to 2.50 parts by mass, and Bi ₂ O ₃ is used as subcomponents. It contains 0.001 to 0.030 parts by mass, MoO ₃ by 0.001 to 0.020 parts by mass, SiO ₂ by 0.001 to 0.010 parts by mass, and CaO by 0.015 to 0.030 parts by mass. It is characterized by that.

According to the present invention, it is possible to provide a heat-resistant high magnetic permeability MnZn ferrite having a small decrease in the initial high relative initial magnetic permeability even when continuously used for a long period of time in a high temperature environment of 100 ° C. or higher.

(Curie temperature)
The MnZn ferrite according to the embodiment of the present invention will be described below. Since the MnZn ferrite according to the present embodiment is used as a magnetic core material for, for example, an AC line filter for automobiles, it is preferable to have a high Curie temperature of 170 to 235 ° C. so as to withstand continuous use for a long time in a high temperature environment. .. The Curie temperature is the temperature at which a ferromagnet turns into a paramagnetic material. In MnZn ferrite, the Curie temperature is almost determined by the ratio _{of the main components Fe 2} O _{3, MnO, and ZnO.} Therefore, MnZn ferrite having a Curie temperature of 170 to 235 ° C. can be obtained by appropriately combining these blending amounts.

_{Specifically, Fe 2} O ₃ is contained as a main component in an amount of 50.50 to 54.00 mol%, ZnO is contained in an amount of 11.00 to 18.00 mol%, and MnO is contained as a balance so as to be 100 mol% in total. MnZn ferrite having a Curie temperature of 170 ° C. or higher and 235 ° C. or lower can be obtained. Fe ₂ O ₃ is more preferably 51.00 mol% or more and 53.00 mol% or less. Further, ZnO is more preferably 15.00 mol% or more and 17.00 mol% or less.

By setting the content of Fe ₂ O ₃ to 50.50 mol% or more, a Curie temperature of 170 ° C. or higher can be obtained. Further, _{by setting Fe 2} O ₃ to 54.00 mol% or less, 7,000 or more can be obtained at a relative initial magnetic permeability of 10 kHz to 200 kHz at 23 ° C to 150 ° C.

Further, by setting the ZnO content to 11.00 mol% or more, 7,000 or more can be obtained with a relative initial magnetic permeability of 10 kHz to 200 kHz at 23 ° C to 150 ° C. Further, by setting ZnO to 18.00 mol% or less, a Curie temperature of 170 ° C. or higher can be obtained.

Since the Curie temperature of this MnZn ferrite is 170 ° C. or higher, it is possible to manufacture a line filter having a MnZn ferrite core as a magnetic core that can be used for a long time in a high temperature environment of 100 ° C. or higher such as an in-vehicle device.

The sub-components for improving the relative initial magnetic permeability will be described below.

(Improvement of temperature dependence of relative initial permeability)
MnZn ferrite preferably has as high a relative initial permeability as possible. For that purpose, it is preferable to have uniform and large crystal grains. _{Therefore, by combining Bi 2} O ₃ that promotes the growth of crystal grains _{and MoO 3} that promotes the uniform growth of crystal grains as a material, uniform and large crystal grains can be obtained, and a high relative initial magnetic permeability can be obtained. Further, _{by containing Co 2} O ₃ , the temperature dependence of magnetocrystalline anisotropy can be suppressed to a small extent, and a high relative initial magnetic permeability (7,000 or more) can be obtained in a wide temperature range (23 to 150 ° C.). By appropriately combining the blending amounts of these materials, MnZn ferrite having a high relative initial magnetic permeability can be obtained over a wide temperature range.

Specifically, in the above MnZn ferrite, when _{the total amount of the main components Fe 2} O ₃ , MnO, and Zn O is 100 parts by mass, Bi ₂ O ₃ is 0.001 to 0.030 mass as a sub-component. By _{containing 0.001 to 0.020 parts by mass of MoO 3} , a specific initial magnetic permeability of 10 kHz at 23 to 150 ° C. can be obtained as 7,000 or more. Further, by _{containing 0.10 to 0.55 parts by mass of Co 2} O ₃ , the temperature dependence of the relative initial magnetic permeability can be suppressed. Bi ₂ O ₃ is more preferably 0.005 to 0.020 parts by mass. Further, MoO ₃ is more preferably 0.001 to 0.010 parts by mass. More preferably, Co ₂ O ₃ is 0.25 to 0.40 parts by mass.

By _{setting the content of Bi 2} O ₃ to 0.030 parts by mass or less, it is possible to suppress the generation of many coarse crystal grains, suppress the non-uniformity of crystal grain size, and increase the initial magnetic permeability of ferrite. In order to suppress the deterioration of the frequency characteristics of the above, it is possible to obtain a relative initial magnetic permeability of 7,000 or more even at 200 kHz. Further, by _{setting Bi 2} O ₃ to 0.001 part by mass or more, crystal grain growth in the central part of the core is sufficiently performed, and 7,000 or more can be obtained at a specific initial magnetic permeability of 10 kHz.

By _{containing 0.001 part by mass or more of MoO 3} , a sintered body having a uniform crystal grain size can be obtained, the frequency characteristics are improved, and a relative initial magnetic permeability of 7,000 or more can be obtained even at 200 kHz. Further, by _{setting MoO 3} to 0.020 parts by mass or less, crystal grain growth in the central part of the core is sufficiently performed, and 7,000 or more can be obtained at a relative initial magnetic permeability of 10 kHz.

By _{containing 0.10 parts by mass or more and 0.55 parts by mass or less of Co 2} O ₃ , the temperature dependence of the specific initial magnetic permeability is suppressed, and the specific initial magnetic permeability of 7,000 or more is obtained from 23 ° C. to 150 ° C. Can be done.

Since this MnZn ferrite has a high relative initial magnetic permeability (7,000 or more) in a wide temperature range (23 to 150 ° C.), a line filter having the same size as the line filter using the conventional MnZn ferrite and having higher performance can be manufactured. can do. Alternatively, a smaller line filter having the same performance as the conventional one can be manufactured.

(Improvement of frequency dependence of relative initial permeability)
MnZn ferrite _{suppresses the generation of eddy currents in the high frequency region by forming grain boundaries with high specific resistance due to SiO 2} and CaO, and has a high relative initial permeability (7,000 or more) up to the high frequency region (~ 200 kHz). ) Can be maintained. Further, when the core is wound and used as the magnetic core of the line filter, it can have a large noise attenuation capability (impedance) in a frequency band (150 kHz to around 1 MHz) which is considered to be particularly important.

Specifically, when the total amount of the main component is 100 parts by mass, the MnZn ferrite _{contains 0.001 to 0.010 parts by mass of SiO 2} and 0.015 to 0.030 parts by mass of CaO as subcomponents. By doing so, it is possible to obtain a specific initial magnetic permeability of 7,000 or more in the frequency region of 10 kHz to 200 kHz. It is more preferable that SiO ₂ is 0.003 to 0.006 parts by mass. CaO is more preferably 0.018 to 0.023 parts by mass.

By _{containing 0.001 part by mass or more of SiO 2} , deterioration of the frequency characteristic of magnetic permeability can be suppressed, and a specific initial magnetic permeability of 7,000 or more can be obtained even at 200 kHz. Further, by _{setting SiO 2} to 0.010 parts by mass or less, the value of the relative initial magnetic permeability at 10 kHz can be obtained as 7,000 or more.

Further, by containing 0.015 parts by mass or more of CaO, deterioration of the frequency characteristic of magnetic permeability can be suppressed, and a specific initial magnetic permeability of 7,000 or more can be obtained even at 200 kHz. Further, by setting CaO to 0.030 parts by mass or less, the value of the relative initial magnetic permeability at 10 kHz can be obtained to be 7,000 or more.

Such MnZn ferrite has a large noise attenuation capability (impedance) in a frequency band (from 150 kHz to around 1 MHz), which is considered to be particularly important when the core is molded and wound and used as a magnetic core of a line filter. .. That is, the ability to reduce noise is greater than that of the line filter using MnZn ferrite of the prior art.

(Improved heat resistance)
When _{MnZn ferrite containing 50 mol% or more of Fe 2} O ₃ is left in a high temperature environment such as 150 ° C., metal ions (Fe ²⁺ and Co ²⁺ ) begin to diffuse into the pores, and the pores are gradually driven around the domain wall. It is considered that the domain wall becomes difficult to move and the relative permeability decreases.

In order to suppress this phenomenon, it is considered effective to reduce ^{metal ions (Fe 2+} , Co ^{2+) in ferrite or reduce Confucius.} In order to reduce ^{Fe 2+} _{, it is considered effective to reduce Fe 2} O ₃ to 50 mol% or less, but there arises a problem that the relative magnetic permeability and the Curie temperature are lowered. Further, _{if the content of Co 2} O ₃ is reduced in order to reduce ^{Co 2+} , the temperature dependence of the relative magnetic permeability deteriorates. Further, it is considered effective to reduce the oxygen concentration in the sintering process in order to reduce the number of vacancies, but in order to maintain a high relative permeability up to a high frequency region of about 200 kHz, the specific resistance of the ferrite sintered body should be increased. In order to improve it, it is necessary to raise the oxygen concentration moderately to form a high resistance grain boundary, and it is difficult to completely eliminate the punctures.

^{The inventors considered that it would be effective to incorporate metal ions other than Fe 2+} and Co ^{2+ in} order to reduce the pores without reducing the oxygen concentration during sintering, and as a result of various studies, the results of various studies were conducted. It was discovered that in MnZn ferrite containing Co ₂ O ₃ and Fe ₂ O _{3 in an amount} of 50 mol% or more, it is possible to suppress a decrease in relative magnetic permeability after being left in a high temperature environment by containing an appropriate amount of _{TiO 2.} did.

Specifically, in the above MnZn ferrite, when the total amount of the main component is 100 parts by mass, by _{containing 0.10 to 2.50 parts by mass of TiO 2} as a sub component, 1000 hours in an environment of 150 ° C. It was found that the rate of change of the specific initial magnetic permeability after being left as compared with the specific initial magnetic permeability before being left can be suppressed to 35% or less as an absolute value. The _{amount of TiO 2} is more preferably 0.75 to 1.25 parts by mass.

By _{containing 0.10 parts by mass or more of TiO 2} , the relative initial magnetic permeability after being left in an environment of 150 ° C. for 1000 hours shall be 35% or less as an absolute value as compared with the relative initial magnetic permeability before being left. Can be done. Further, by _{setting TiO 2} to 2.50 parts by mass or less, a relative initial magnetic permeability of 7,000 or more at 23 ° C. to 150 ° C. can be obtained.

Such MnZn ferrite can provide a line filter having little deterioration in characteristics such as relative initial magnetic permeability due to aging even in a situation where it is used for a long period of time in an in-vehicle environment of 100 ° C. or higher.

As described above, Fe ₂ O ₃ , ZnO, and MnO are the main components, and Co ₂ O ₃ , TiO ₂ , Bi ₂ O ₃ , MoO ₃ , SiO ₂ , and CaO are contained in a predetermined range as subcomponents. Therefore, the Curie temperature is 170 ° C. or higher, the relative initial magnetic permeability is as high as 7000 ° C. or higher in a wide frequency range of 10 kHz to 200 kHz in the temperature range of 23 to 150 ° C., and the ratio even after being left for 1000 hours in an environment of 150 ° C. It is possible to obtain MnZn ferrite having a high magnetic permeability having excellent heat resistance characteristics that the decrease in the initial magnetic permeability is small.

(Production method)
Next, one embodiment of the method for producing MnZn ferrite will be described.
The method for producing an MnZn ferrite core of the present embodiment includes a crushing and mixing step, a calcining step, a crushing step, a molding step, and a sintering step.

The Fe ₂ O ₃ content after sintering is 50.50 mol% or more and 54.00 mol% or less, the ZnO content is 11.00 mol% or more and 18.00 mol% or less, and the balance is MnO so that the total amount is 100 mol%. In the crushing and mixing step, Fe ₂ O ₃ is 49.30 mol% or more and 52.80 mol% or less, ZnO is 11.60 mol% or more and 18.60 mol% or less, and the balance is MnO. Weigh the raw material powder. Next, all the raw material powders are mixed and crushed to obtain a mixed powder. Specifically, using an attritor or the like, the aggregated raw material powder is crushed and mixed until the median diameter D50 of the mixed powder becomes 0.5 μm or more and 0.9 μm or less. The particle size distribution of the mixed powder can be measured with a particle size distribution measuring device.

In the calcination step, polyvinyl alcohol is added to the mixed powder obtained in the crushing and mixing step to obtain granules using a spray dryer or the like, and then the granules are calcinated in an air atmosphere at 750 ° C. for 1 hour. To get.

In the crushing step, when the total mass of the obtained calcined product (main component) is 100 parts by mass, 0.001 to 0.010 parts by mass of SiO ₂ is added to the calcined product. Here, the _{amount of SiO 2} added is preferably 0.003 to 0.005 parts by mass. _{Further, 0.019 to 0.040 parts by mass of Ca (OH) 2} is added to the calcined product so that the CaO content after sintering is 0.015 to 0.030 parts by mass. _{Further, the required amount of MoO 3} is added to the calcined _{product so that the MoO 3} content after sintering is 0.001 to 0.020 parts by mass when the total mass of the calcined product is 100 parts by mass. Since a part of MoO ₃ is volatilized in the sintering step, a required amount larger than the desired content after sintering is added. The required amount of MoO ₃ is, for example, 0.1 parts by mass or less.

Bi ₂ O ₃ has the effect of growing crystal grains by adding it to ferrite, but also has the effect of making the crystal grain size non-uniform. Therefore, when the total mass of the calcined product is 100 parts by mass. It is desirable to add 0.001 to 0.030 parts by mass to the calcined product. Further, when the total mass of the calcined product is 100 parts by mass so that _{the Co 2} O _{3 content after sintering is 0.10 to 0.55 parts by mass, 0.09 to 0.54 parts by mass.} Add Co ₃ O ₄ to the calcined product. Further, when the total mass of the calcined product is 100 parts by mass, 0.10 to 2.50 parts by mass of TiO ₂ is added.

After adding each additive, the calcined product is crushed with a crusher to obtain a crushed powder. Specifically, in the crushing step, the calcined product is crushed until the median diameter D50 of the particle size after crushing becomes 0.5 μm or more and 1.0 μm or less to obtain a crushed powder.

In the molding step, polyvinyl alcohol is added to the crushed powder obtained in the crushing step to obtain granules using a spray dryer or the like, and then the granules have a predetermined shape, for example, an outer diameter of 19 mm and an inner diameter of 13 mm. It is molded into a toroidal core with a height of 11 mm.

In the sintering step, for example, a sintered body is obtained by sintering at 1300 ° C. for a predetermined time.

Next, an embodiment will be described. In the example, an MnZn ferrite core was prepared using a raw material containing a predetermined component in a predetermined amount, and its characteristics were evaluated. First, the ferrite core used for evaluating the characteristics will be described. The ferrite cores produced in the examples and comparative examples of the present invention are toroidal type ferrite cores having an outer diameter of 19 mm, an inner diameter of 13 mm, and a height of 11 mm. A copper wire having a wire diameter of 0.26 mm was wound around this ferrite core 10 times to prepare an evaluation sample, and the relative initial magnetic permeability was measured using an impedance analyzer (4194A, Yokogawa Hewlett-Packard Co., Ltd.). The current value at the time of measurement was 0.2 mA.

(Example 1)
_{In the crushing and mixing step, Fe 2} is produced so that the Fe ₂ O ₃ content after sintering is 50.50 mol%, the ZnO content is 16.00 mol%, and the MnO content is 33.50 mol%, for a total of 100 mol%. Each raw material powder was weighed and mixed so that O ₃ was 49.30 mol%, Zn O was 16.60 mol%, and Mn ₃ O ₄ was 34.10 mol% in terms of MnO, for a total of 100 mol%. The mixture was crushed with an attritor and pulverized until the median diameter D50 of the mixture was 0.5 μm or more and 0.9 μm or less. Next, polyvinyl alcohol was added thereto to obtain granules using a spray dryer, and then the granules were calcined at 750 ° C. for 1 hour in an air atmosphere to obtain a calcined product.

When the total mass of the obtained calcined product was 100 parts by mass, 0.004 parts by mass of SiO ₂ was added to the calcined product. Hereinafter, similarly, 0.028 parts by mass of Ca (OH) ₂ , MoO ₃ is 0.075 parts by mass, and Bi ₂ O ₃ is 0. _{0.28 parts by mass of Co 3} O ₄ when the total mass of the calcined product is 100 parts by mass so that _{the Co 2} O ₃ content after sintering is 014 parts by mass and 0.29 parts by mass. TiO ₂ was added to the calcined product in an amount of 0.750 parts by mass.

Next, the mixture of the calcined product and the additive was crushed with a crusher so that the median diameter D50 of the particle size after crushing was 0.5 μm or more and 1.0 μm or less to obtain a crushed powder. Polyvinyl alcohol is added to the pyroclastic material to obtain granules using a spray dryer, and then the granules are molded into a toroidal core having an outer diameter of 19 mm, an inner diameter of 13 mm, and a height of 11 mm, and sintered at 1300 ° C. Obtained a sintered body. The above-mentioned manufacturing process until the sintered body is obtained is the same as the manufacturing process of the ferrite core in the prior art.

The relative initial magnetic permeability (23 ° C.) of this ferrite core was 7100 at 10 kHz and 7200 at 200 kHz. The Curie temperature was 170 ° C. This ferrite core was left in a constant temperature bath (air atmosphere) at 150 ° C. for 1000 hours, and the relative initial magnetic permeability at 120 ° C. before and after the standing was measured to determine the rate of change. As a result of measuring the relative initial magnetic permeability as described above, the rate of change of the specific initial magnetic permeability at 10 kHz was −9.8%. The rate of change was calculated as ((specific initial magnetic permeability at 120 ° C. after standing-specific initial magnetic permeability at 120 ° C. before leaving) / specific initial magnetic permeability at 120 ° C. before leaving)) × 100 (%).

In the same manner as above, the characteristics of the ferrite cores of Examples 2 to 17 and Comparative Examples 1 to 16 were measured with the compositions shown in Table 1. The results are shown in Table 1.

As shown in Table 1, by producing an MnZn ferrite core using a material having a composition within the range of the present invention, the Curie temperature is 170 ° C. or higher, and the relative initial magnetic permeability (23 ° C.) is 7000 at 10 kHz to 200 kHz. As described above, it was possible to obtain an MnZn ferrite core in which the rate of change in the relative initial magnetic permeability at 120 ° C. before and after being left in an environment of 150 ° C. for 1000 hours was 35% or less as an absolute value.

In particular, from Example 1-4 and Comparative Example 1-4, it is important to keep _{Fe 2} O _{3 and Zn O and Mn O within a predetermined range in order to bring the Curie temperature to 170-235 ° C.} Understand. Further, from Example 5-12 and Comparative Example 5-12, in order to make the relative initial magnetic permeability (23 ° C.) 7,000 or more, SiO ₂ , CaO, MoO _3, and Bi ₂ O ₃ are set within a predetermined range. Turns out to be important. Further, from Example 13-17 and Comparative Example 13-16, in order for the rate of change of the relative initial magnetic permeability at 120 ° C. before and after being left in an environment of 150 ° C. for 1000 hours to be 35% or less as an absolute value, Co. _It can be seen that it is important to keep 2 O ₃ and TiO _{2 within a predetermined range.}

Claims (5)

MnZn ferrite whose main components are Fe ₂ O _{3 and Zn O and Mn O.}
Fe ₂ O ₃ was contained in an amount of 50.50 to 54.00 mol%, ZnO was contained in an amount of 11.00 to 18.00 mol%, and the balance of MnO was contained in a total amount of 100 mol%.
When the total amount of the main component is 100 parts by mass, Co ₂ O ₃ is 0.10 to 0.55 parts by mass, TiO ₂ is 0.10 to 2.50 parts by mass, and Bi ₂ O ₃ is used as subcomponents. It contains 0.001 to 0.030 parts by mass, MoO ₃ by 0.001 to 0.020 parts by mass, SiO ₂ by 0.001 to 0.010 parts by mass, and CaO by 0.015 to 0.030 parts by mass. MnZn ferrite with high heat resistance and high magnetic permeability. The heat-resistant high magnetic permeability MnZn ferrite according to claim 1, wherein the Co ₂ O ₃ is contained in an amount of 0.25 to 0.40 parts by mass and the TiO _{2 is contained in an amount of 0.75 to 1.25 parts by mass.} The heat-resistant high magnetic permeability MnZn according to claim 1 or 2, wherein the Bi ₂ O ₃ is contained in an amount of 0.005 to 0.020 parts by mass and the MoO _{3 is contained in an amount of 0.001 to 0.010 parts by mass.} Ferrite. The heat-resistant and highly transparent according to any one of claims 1 to 3, wherein the SiO ₂ is contained in an amount of 0.003 to 0.006 parts by mass and the CaO is contained in an amount of 0.018 to 0.023 parts by mass. Permeability MnZn ferrite. The heat resistance according to any one of claims 1 to 4, wherein the rate of change of the relative initial magnetic permeability at 10 kHz at 120 ° C. before and after being left in an environment of 150 ° C. for 1000 hours is 35% or less as an absolute value. MnZn ferrite core for line filters manufactured using high magnetic permeability MnZn ferrite.