JP2006148023A - Toroidal coil, electric circuit element, and signal transmission unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toroidal coil or the like capable of coping with downsizing. <P>SOLUTION: The toroidal coil 10 includes: a gapless toroidal-shaped magnetic core member 11 formed to be a consecutive annular shape in a circumferential direction; and a conductor 12 wound on the magnetic core member 11, and the magnetic core member 11 comprises a ferrite sintered compact, as main constituents, containing 54.1 to 57.5 mol% Fe<SB>2</SB>O<SB>3</SB>, and the balance substantially MnO, and further containing, as additives, 60 to 800 ppm Si expressed in terms of SiO<SB>2</SB>, 600 to 4000 ppm Ca expressed in terms of CaCO<SB>3</SB>, and 1500 to 4000 ppm Co<SB>3</SB>O<SB>4</SB>. The ferrite sintered compact may furthermore contain Zn. The toroidal coil 10 as above has the inductance with excellent performance more than that of Ni group toroidal coils of prior arts, and the number of turns of the conductor 12 can be reduced more than that of the Ni group toroidal coils of prior arts. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a toroidal coil configured by winding a conductor around a toroidal type ferrite core, an electric circuit element configured using the toroidal coil, and a signal transmission device.

  The inductor element (coil element) is a circuit element that has been used for a long time, and is an essential basic circuit element even today. From an industrial point of view, ideal characteristics required for an inductor element include that an inductance with little variation is obtained by a certain number of turns, that the temperature dependence of the inductance is small, and that the Q factor is large. It is done.

In general, an inductor element uses an appropriate magnetic material as a core from the relationship between an inductance value and a use frequency, and forms an inductor element by winding a coil. This is because, when a magnetic material is used as a core, a desired inductance can be obtained with a smaller number of turns as the magnetic permeability of the magnetic material increases. For example, in a high frequency region exceeding about 100 MHz, the core is used as a core (dust core) in which metal powder is hardened with an insulating resin, a nonmagnetic core such as resin, or an air core coil. On the other hand, in a frequency region of approximately 100 MHz or less, particularly 10 MHz or less, a core having a higher magnetic permeability than a dust core is used, and a representative one is a ferrite sintered body (hereinafter referred to as a ferrite core). )
In general, the meaning of proper use of such a core material is generally described. In a high-frequency circuit of approximately 100 MHz or more, even when a certain AC impedance (inductive impedance) is ensured, the AC impedance increases in proportion to the frequency. Therefore, sufficient AC impedance can be secured even with a relatively small inductance value. That is, the magnetic permeability of the core material for increasing the inductance value may be small, an air-core coil can be used, and at the same time, the number of turns as the coil can be reduced.
On the other hand, in a frequency region of approximately 100 MHz or less, particularly 10 MHz or less, in order to ensure a desired AC impedance, a large inductance value is required as the frequency is low. That is, the number of turns as a coil is increased, or a core material with high magnetic permeability, for example, a ferrite sintered body is selected. Considering the manufacture of the inductor element, it is clear that the smaller the number of turns of the coil, the better. Therefore, it is apparent that it is preferable to select a core material having a high magnetic permeability such as a ferrite core.

  There are roughly two types of inductor elements using a ferrite core. One is a solenoid type inductor element in which a winding is provided on a rod-shaped core, and the other is a toroidal type inductor element in which a winding is provided on an annular core. There are differences in their characteristics and manufacturability, but the biggest difference is that the solenoid-type inductor element has an open magnetic circuit structure, and the magnetic flux generated in the core leaches out from both end faces of the rod-shaped core. On the other hand, the toroidal inductor element has a closed magnetic circuit structure, and the magnetic flux generated in the core is almost completely sealed in the annular core. That is, the toroidal inductor element has a feature that it is difficult to receive external magnetic field disturbance and does not leak magnetic flux to the outside at the same time. That is, the toroidal inductor element can be said to be an element suitable for a circuit that handles a small signal sensitive to external noise.

Due to such features, toroidal inductor elements have been used in various circuits. For example, a resonance circuit, a filter circuit, a transmission transformer, a balun, and the like.
Although the required characteristics differ depending on the application, in the resonance circuit and the filter circuit, the temperature dependence of the inductance becomes a problem as well as the initial accuracy of the inductance value. A dust core that is often used in a high-frequency region has a very small temperature dependency of the magnetic permeability and does not cause a problem. However, in a ferrite core used in a low frequency region, the temperature dependence of permeability is relatively large, and some measures must be taken to improve the temperature dependence of inductance.
As the most general technique for improving the temperature dependence of the inductance, as shown in FIGS. 6A and 6B, a gap (gap) 3 is inserted in a part of the circumference of the annular core 1 There is. As a result, the apparent magnetic permeability (effective magnetic permeability) of the core 1 is lowered, but the influence of various characteristics inherent in the core 1 is less likely to appear, and as a result, the temperature dependence and the accuracy of the initial inductance are improved.

However, as shown in FIGS. 6A and 6B, when a gap is formed in the core 1, the effective magnetic permeability decreases. Accordingly, in order to obtain an inductance equivalent to that of the gapless ferrite core 4 as shown in FIG. 6C, the number of turns of the coil 2 must be increased. As a result, the process of winding the winding takes time and effort.
Further, when the gap is formed, the mechanical strength of the core 1 is reduced. Furthermore, the manufacturing process increases due to the processing for forming the gap, and the manufacturing cost increases. In particular, since the ferrite sintered body is a very hard material, it is necessary to select a very inefficient processing method using a rotating disk grindstone or the like for the gap processing, and there is a problem that processing takes time and cost. It will be remarkable.
The present invention has been made based on such a technical problem, and provides a toroidal coil, an electric circuit element, and a signal transmission device that are low in temperature dependency, excellent in productivity, and can be manufactured at low cost. The purpose is to do.

  Conventionally, Ni-based ferrite has been used as a material for a ferrite core having low temperature dependence. The ferrite core is required to have a characteristic that the temperature dependence of the initial permeability is small and that the loss coefficient (tan δ) is small, that is, the Q value (Q = 1 / tan δ) is large. However, since the Ni-based ferrite cannot increase the inductance and the Q value so much, the improvement in the quality of the toroidal coil using the Ni-based ferrite has almost reached the limit. As for inductance, even if Ni-based ferrite is used, a high value can be obtained by increasing the number of turns of the coil. However, increasing the number of turns leads to an increase in the size of the toroidal coil. It is not preferable to increase the number of turns in view of downsizing of devices.

  By the way, as a ferrite material, a ferrite material containing Mn and further Zn is known. Since this ferrite material has an advantage of high saturation magnetic flux density, it is mainly used for transformers for large currents (see, for example, Patent Documents 1 and 2). However, a ferrite material containing Mn and further Zn has a large temperature dependency.

JP-A-11-3813 (Claims, Examples) JP 2000-286119 A (Claims, Examples)

Accordingly, the present inventors have made various studies focusing on the fact that ferrite materials containing Mn and Zn can have higher inductance and Q value than Ni-based ferrites for the technical problems as described above. .
As a result, for ferrite materials containing Mn etc., the temperature dependence of the initial permeability can be improved and applied to toroidal coils by making the main composition, the types of subcomponents, and the contents of subcomponents appropriate. I found out. More specifically, the ferrite sintered body includes a ferrite sintered body and a conductor wound around the ferrite sintered body, and the ferrite sintered body is Fe ₂ O ₃ : 54.1 to 57.5 mol%, and the balance is substantially MnO. Is a toroidal coil containing Si as a main component, Si as a subcomponent in an amount of 60 to 800 ppm in terms of SiO ₂ , Ca in a range of 600 to 4000 ppm in terms of CaCO ₃ , and 1500 to 4000 ppm of Co ₃ O ₄ . They found that temperature dependence could be improved.

Furthermore, when the subject of the present invention was further studied for such a toroidal coil, according to the toroidal coil as described above, the temperature dependence of the initial permeability can be kept low even in a gapless state. I found out.
The toroidal coil of the present invention made there includes an annular ferrite sintered body continuous in the circumferential direction and a conductor wound around the ferrite sintered body, and the ferrite sintered body is Fe ₂ O ₃ : 54. 0.1-57.5 mol%, the balance being substantially MnO as the main component, Si as the secondary component 60-800 ppm in terms of SiO ₂ , Ca 600-4000 ppm in terms of CaCO ₃ , and Co ₃ O ₄ 1500-4000 ppm It is characterized by containing.
The ferrite sintered body may further contain Zn. In this case, the composition of the ferrite sintered body is Fe ₂ O ₃ : 54.1 to 57.5 mol%, ZnO: 10.5 mol% or less (however, , 0 is not included), and the balance is substantially composed of MnO as a main component, Si as an auxiliary component is 60 to 800 ppm in terms of SiO ₂ , Ca is 600 to 4000 ppm in terms of CaCO ₃ , and Co ₃ O ₄ is 1000 to 3800 ppm What should I do?
In the toroidal coil of the present invention, for example, in the range of −40 ° C. to 130 ° C., the initial permeability is 500 or more, and the absolute value of the change rate of the initial permeability is 20 based on the initial permeability at 20 ° C. % Or less.

Further, the ferrite sintered body constituting the toroidal coil of the present invention can contain TiO ₂ of 5000 ppm or less (including 0) and / or SnO ₂ of 5000 ppm or less (including 0). The content of TiO ₂ and SnO ₂ is arbitrary, but by including these, for example, the absolute value of the rate of change of initial permeability in the range of −40 ° C. to 130 ° C. is 18% or less, and further 15% or less. It can be.
Furthermore, the ferrite sintered body constituting the toroidal coil of the present invention has Ta ₂ O ₅ of 3000 ppm or less (including 0), Nb ₂ O ₅ of 500 ppm or less (provided that 0 is included), ZrO ₂ . At least one or more of 500 ppm or less (including 0) can be contained. Inclusion of Ta ₂ O ₅ , Nb ₂ O ₅ , and ZrO ₂ is optional, but by including these, for example, the absolute value of the rate of change of initial permeability in the range of −40 ° C. to 130 ° C. is 15%. Hereinafter, it is also possible to make it 10% or less.
According to the above toroidal coil of the present invention, in addition to the above characteristics, for example, the characteristic that the minimum value of Q (Q = 1 / tan δ, tan δ is a dielectric loss tangent) in the range of −40 ° C. to 130 ° C. is 200 or more. Obtainable.
The toroidal coil of the present invention can be applied to various applications. Typical examples of the toroidal coil include filters such as a bandpass filter, electric circuit elements such as a tuning circuit and a resonance circuit, and the like. Examples thereof include a signal transmission device including an electric circuit.

The electric circuit element of the present invention is an annular ring that is continuous in the circumferential direction, contains Fe ₂ O ₃ and MnO as main components, and has an initial permeability in the range of −40 ° C. to 130 ° C. based on the initial permeability at 20 ° C. A conductor is wound around a ferrite sintered body whose absolute value of magnetic permeability change rate is 20% or less, and a toroidal coil mounted on the substrate, and connected to the toroidal coil in parallel or in series, mounted on the substrate And a capacitor. Such an electric circuit element can function as a resonance circuit or a filter circuit by mounting the toroidal coil and the capacitor connected in parallel on the substrate.
In this case, the ferrite sintered body is Fe ₂ O ₃ : 54.1 to 57.5 mol%, the balance is substantially composed of MnO as a main component, Si as an auxiliary component is 60 to 800 ppm in terms of SiO ₂ , and Ca is CaCO _3. It is preferable to contain 600 to 4000 ppm in terms of conversion and 1500 to 4000 ppm of Co ₃ O ₄ .
Further, the ferrite sintered body is composed of Fe ₂ O ₃ : 54.1 to 57.5 mol%, ZnO: 10.5 mol% or less (however, not including 0), and the balance is substantially composed of MnO as a main component. And Si may contain 60 to 800 ppm in terms of SiO ₂ , Ca to 600 to 4000 ppm in terms of CaCO ₃ , and 1000 to 3800 ppm of Co ₃ O ₄ .

Further, the signal transmission device of the present invention includes a toroidal coil in which a conductor is wound around an annular ferrite sintered body that is continuous in the circumferential direction, and a resonance circuit configured by a capacitor connected in parallel to the toroidal coil; A lead wire that passes through the annular ferrite sintered body and transmits an AC signal to and from the resonance circuit, and the ferrite sintered body is Fe ₂ O ₃ : 54.1 to 57.5 mol%, the remainder It is characterized by containing MnO as a main component, Si as an auxiliary component in a range of 60 to 800 ppm in terms of SiO ₂ , Ca in a range of 600 to 4000 ppm in terms of CaCO ₃ , and Co ₃ O ₄ in a range of 1500 to 4000 ppm. Further, the ferrite sintered body is composed of Fe ₂ O ₃ : 54.1 to 57.5 mol%, ZnO: 10.5 mol% or less (however, not including 0), and the balance is substantially composed of MnO as a main component. As for Si, it is also possible to contain 60 to 800 ppm in terms of SiO ₂ , Ca to 600 to 4000 ppm in terms of CaCO ₃ , and 1000 to 3800 ppm of Co ₃ O ₄ .

  According to the present invention, it is possible to obtain a toroidal coil that is low in temperature dependency, excellent in productivity, and can be manufactured at low cost. As a result, the number of turns of the conductor can be reduced, and a small and high-performance electric circuit element and signal transmission device can be formed.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
The toroidal coil in the present invention has the basic configuration shown in FIG. 1, but the present invention is characterized in that a ferrite sintered body having the following composition is used as the magnetic core member (ferrite sintered body) 11.
Hereinafter, the reasons for limiting the composition of the ferrite sintered body will be described.

First, the reasons for limiting the main components constituting the ferrite sintered body will be described.
Fe ₂ O ₃ is 54.1 to 57.5 mol%. When Fe ₂ O ₃ is less than 54.1 mol%, Q is small and the rate of change of initial permeability μi (hereinafter referred to as μi rate of change as appropriate) is also large. On the other hand, when Fe ₂ O ₃ exceeds 57.5 mol%, the μi change rate also increases.
A desirable amount of Fe ₂ O ₃ is 54.5 to 57.0 mol%, and a more desirable amount of Fe ₂ O ₃ is 55.5 to 56.5 mol%.

ZnO is 10.5 mol% or less. If ZnO exceeds 10.5 mol%, the μi change rate is large, and it becomes difficult to obtain a Q value of 200 or more.
A desirable ZnO amount is 0.1 to 10.0 mol%, and a more desirable ZnO amount is 2.0 to 9.0 mol%.

  In addition to the above, the sintered ferrite body of the present invention contains MnO as a substantial remainder.

The reason for limiting the composition when the ferrite of the present invention is MnZn-based has been described above. However, the addition of the first to fourth subcomponents described in detail below is not limited to MnZn-based ferrite, but Zn as a main component. It is also effective in the case of ferrite that does not contain (hereinafter sometimes referred to as “Mn ferrite”).
When Mn ferrite is the main component, the amount of Fe ₂ O _{3 is} preferably 55.0 to 57.0 mol%, and the substantial balance is preferably MnO. In this case, the more desirable amount of Fe ₂ O ₃ is 56.0-57.0 mol%.

Next, the reasons for limiting the subcomponents will be described.
The ferrite sintered body of the present invention contains Si as a first subcomponent in a range of 60 to 800 ppm in terms of SiO ₂ and Ca in a range of 600 to 4000 ppm in terms of CaCO ₃ .
Si and Ca are segregated at the grain boundaries to form a high resistance layer and contribute to low loss, and have the effect of improving the sintering density as a sintering aid. However, when Si exceeds 800 ppm in terms of SiO ₂ or Ca exceeds 4000 ppm in terms of CaCO ₃ , loss deterioration due to discontinuous abnormal grain growth is large. Therefore, in the present invention, Si is set to 800 ppm or less in terms of SiO ₂ and Ca is set to 4000 ppm or less in terms of CaCO ₃ . On the other hand, if Si is less than 60 ppm in terms of SiO ₂ or Ca is less than 600 ppm in terms of CaCO ₃ , the above effect cannot be obtained sufficiently, so Si is 60 ppm or more in terms of SiO ₂ and Ca is 600 ppm or more in terms of CaCO _3. To do.
The desirable Si content is 70 to 600 ppm in terms of SiO ₂ , and the more desirable Si content is 100 to 500 ppm in terms of SiO ₂ .
The desirable Ca content is 600 to 3500 ppm in terms of CaCO ₃ , and the more desirable Ca content is 1200 to 3500 ppm in terms of CaCO ₃ .

The ferrite sintered body of the present invention contains a predetermined amount of Co ₃ O ₄ as the second subcomponent. Co ₃ O ₄ effectively contributes to reducing the μi change rate and flattening the μi change rate, and the inclusion of Co ₃ O ₄ is effective to improve the Q value.
In the present invention, when Mn ferrite is the main component, Co ₃ O ₄ is contained in the range of 1500 to 4000 ppm. In this case, if the amount of Co ₃ O ₄ is less than 1500 ppm, the above effect cannot be obtained sufficiently. On the other hand, when the amount of Co ₃ O ₄ exceeds 4000 ppm, the Q value is remarkably lowered, and the μi change rate is increased.
On the other hand, when MnZn-based ferrite is a main component in the present invention, Co ₃ O ₄ may be contained within a range of 1000 to 3800 ppm. By containing Co ₃ O ₄ in the range of 1000 to 3800 ppm, the above effect can be enjoyed. In this case, the desirable amount of Co ₃ O ₄ is 1000 to 2800 ppm, and the more desirable amount of Co ₃ O ₄ is 1200 to 2500 ppm.

Furthermore, the ferrite sintered body of the present invention can contain TiO ₂ of 5000 ppm or less (including 0) and / or SnO ₂ of 5000 ppm or less (including 0) as the third subcomponent.
Ti and Sn are present in the crystal grains and at the crystal grain boundaries, and have an effect of reducing loss. However, when the amount of TiO ₂ exceeds 5000 ppm, the loss is deteriorated due to discontinuous abnormal grain growth. Therefore, in the present invention, the amount of TiO ₂ is set to 5000 ppm or less. For the same reason as TiO ₂ , the upper limit of SnO ₂ is also set to 5000 ppm.
On the other hand, in order to fully enjoy the effect of loss reduction, it is desirable to contain TiO ₂ and / or SnO ₂ as the third subcomponent at 500 ppm or more.
A desirable TiO ₂ content is 500 to 4000 ppm, and a more desirable TiO ₂ content is 500 to 3000 ppm.
Desirable SnO ₂ content is 500 to 4000 ppm, and more desirable Sn content is 500 to 3000 ppm.

  When the third subcomponent is contained in combination, the total content is 8000 ppm or less, preferably 1000 to 5000 ppm.

The ferrite sintered body of the present invention includes, as the fourth subcomponent, Ta ₂ O ₅ of 3000 ppm or less (including 0), Nb ₂ O ₅ of 500 ppm or less (including 0), and ZrO ₂ of 500 ppm. At least one or more of the following (including 0) can be included. By including these fourth subcomponents, it is possible to obtain the effect of reducing the μi change rate and / or reducing the loss. In order to fully enjoy the effect, it is desirable to contain 50 ppm or more of Ta ₂ O ₅ , Nb ₂ O ₅ , and ZrO ₂ .
A desirable amount of Ta ₂ O ₅ is 0 to 2500 ppm, and a more desirable amount of Ta ₂ O ₅ is 500 to 2000 ppm.
A desirable Nb ₂ O ₅ content is 0 to 400 ppm, and a more desirable Nb ₂ O ₅ content is 50 to 350 ppm.
A desirable amount of ZrO ₂ is 0 to 400 ppm, and a more desirable amount of ZrO ₂ is 50 to 350 ppm.
When the fourth subcomponent is contained in combination, the total content is 3000 ppm or less, preferably 300 to 2000 ppm.

The ferrite sintered body of the present invention exhibits a characteristic that the maximum value of the μi change rate at −40 ° C. to 130 ° C. is 20% or less, desirably 15% or less in absolute value. Generally, the tolerances of electronic components include ± 10%, ± 5%, ± 2%, and ± 1% grades, but a normal coil is about ± 10%. On the other hand, according to the ferrite sintered body of the present invention, by selecting a particularly desirable composition, for example, the maximum value of the μi change rate at −40 ° C. to 130 ° C. is 10% or less in absolute value, and further 5 % Or less. Furthermore, the ferrite sintered body of the present invention can have an initial permeability of 500 or more in the range of −40 ° C. to 130 ° C., for example.
Further, the ferrite sintered body of the present invention exhibits the characteristic that the maximum value of the μi change rate is 20% or less in absolute value, and the Q value is 200 or more, further 250 or more.
As described above, since the ferrite sintered body of the present invention can obtain high characteristics that could not be obtained with MnZn-based ferrite or Mn ferrite in the past, the toroidal coil configured to include this ferrite sintered body is provided. Furthermore, the electric circuit element and the signal transmission device configured to include the toroidal coil can have characteristics higher than those of the conventional one.

Next, the manufacturing method suitable for the ferrite sintered body according to the present invention will be described.
As the raw material of the main component, an oxide or a powder of a compound that becomes an oxide by heating is used. Specifically, Fe ₂ O ₃ powder, Mn ₃ O ₄ powder, ZnO powder, or the like can be used. In addition, what is necessary is just to select suitably the average particle diameter of each raw material powder in the range of 0.1-5.0 micrometers.
The raw material powder of the main component is wet mixed and then calcined. The calcining temperature may be a predetermined temperature within a range of 650 to 1000 ° C., and the atmosphere may be N ₂ or air. What is necessary is just to select the stable time of calcination suitably in the range of 0.5 to 5.0 hours. After the calcination, the calcined body is pulverized, for example, to an average particle size of about 0.5 to 2.0 μm. In the present invention, not only the above-mentioned main component materials, but also a composite oxide powder containing two or more metals may be used as the main component materials. For example, a complex oxide powder containing Fe and Mn can be obtained by oxidizing and roasting an aqueous solution containing iron chloride and manganese chloride. This powder and ZnO powder may be mixed and used as a main component material. In such a case, calcining is unnecessary.

Similarly, an oxide or a powder of a compound that becomes an oxide by heating can also be used as a raw material for the accessory component. Specifically, SiO ₂ , CaCO ₃ , Co ₃ O ₄ , TiO ₂ , SnO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , ZrO ₂ or the like can be used.
The raw material powders of these subcomponents are mixed with the main component powder pulverized after calcining. However, after mixing with the raw material powder of the main component, it can be subjected to calcining together with the main component.

  The mixed powder composed of the main component and the subcomponent is granulated into a granule in order to smoothly execute the subsequent molding process. Granulation can be performed using, for example, a spray dryer. A small amount of a suitable binder such as polyvinyl alcohol (PVA) is added to the mixed powder, and this is sprayed and dried with a spray dryer. The particle size of the obtained granules is preferably about 40 to 400 μm.

The obtained granule is formed into a desired shape using, for example, a press having a mold having a predetermined shape, and this formed body is subjected to a firing step.
In the firing step, it is necessary to control the firing temperature and firing atmosphere. The firing temperature can be appropriately selected from the range of 1050 to 1250 ° C., but it is desirable to fire in the range of 1100 to 1200 ° C. in order to sufficiently bring out the effect of the ferrite material of the present invention.

  The ferrite sintered body in the present invention can be obtained through the above steps.

  Next, the toroidal coil of the present invention will be described. As shown in FIG. 1, the toroidal coil 10 of the present invention includes a magnetic core member 11 and a conductor 12 wound around the magnetic core member 11. In the present invention, a ferrite sintered body having the above-described composition is used for the magnetic core member 11.

The magnetic core member 11 has a cylindrical shape in which a hole is formed in the central portion, that is, a so-called toroidal shape, and can have, for example, an outer diameter of 4 to 30 mm, an inner diameter of 2 to 15 mm, and a thickness of 1 to 10 mm.
Here, the magnetic core member 11 has an annular shape that is completely continuous in the circumferential direction and has a so-called gapless shape without a gap.

  For example, a copper wire can be used as the conductor 12. The pitch and number of turns of the winding pattern can also be set as appropriate according to the application.

Next, the signal transmission device of the present invention will be described. FIG. 2 is a schematic diagram of the signal transmission device. As shown in FIG. 2, the signal transmission device 100 includes a toroidal coil 10, a capacitor 20 provided in parallel with the toroidal coil 10, and a conductor 30 that penetrates the center of the magnetic core member 11 of the toroidal coil 10. . In this signal transmission device 100, the capacitor 20 and the toroidal coil 10 constitute a parallel resonance circuit. These toroidal coil 10 and capacitor 20 are mounted on a substrate (not shown).
In such a signal transmission device 100, a signal can be transmitted between the parallel resonance circuit constituted by the capacitor 20 and the toroidal coil 10 and the conducting wire 30.

  Since the toroidal coil 10 of the present invention has a high initial magnetic permeability due to the gapless shape, the inductance is higher than that of the conventional Ni-based toroidal coil, and the number of turns of the conductor 12 is smaller than that of the conventional Ni-based toroidal coil. Therefore, the toroidal coil 10 and the signal transmission device 100 can be reduced in size.

Hereinafter, the present invention will be described based on specific examples.
(First embodiment)
Ferrite cores having the compositions shown in Table 1 were produced.
Fe ₂ O ₃ powder, MnO powder and ZnO powder were used as raw materials for the main component, and these were wet mixed and then calcined at 850 ° C. for 3 hours.
Next, the calcined product of the main component material and the subcomponent material were mixed. SiO ₂ powder, CaCO ₃ powder, Ta ₂ O ₅ powder, Co ₃ O ₄ powder, and TiO ₂ powder were used as the raw materials for the accessory components. The auxiliary component raw material was added to the calcined material of the main component raw material and mixed while being pulverized. The pulverization was performed until the average particle size of the calcined product was about 1.0 μm. A binder was added to the resulting mixture, granulated, and then molded to obtain a toroidal shaped molded body.

The obtained molded body was fired at a temperature of 1150 ° C. (stable part 5 hours, stable part oxygen partial pressure 0.5%) under oxygen partial pressure control to obtain a ferrite core. Using this ferrite core, for example, the Q value in a temperature range of −40 ° C. to 130 ° C. was measured. The toroidal size was 20 mm in outer diameter, 10 mm in inner diameter, and 5 mm in thickness. The number of turns was 20 turns, and the excitation voltage was 250 mV. Table 1 shows the minimum Q value in the range of −40 ° C. to 130 ° C. as Qmin. Moreover, the initial permeability μi (measurement frequency: 100 kHz) in the range of −40 ° C. to 130 ° C. was measured. Based on the initial permeability μi at 20 ° C., the absolute value of the change rate of the initial permeability μi in the range of −40 ° C. to 130 ° C. is shown as “Δμi” in Table 1. Table 1 also shows the minimum value μi _min of μi in the range of −40 ° C. to 130 ° C. The change rate of the initial permeability μi was calculated based on the following formula.

Change rate of initial permeability μi = (μi _T −μi ₂₀ ) / μi ₂₀ × 100 (%)
μi _T : Initial permeability at temperature T ° C μi
μi ₂₀・ ・ ・ Initial permeability μi at 20 ℃

Sample No. 1-7, Fe ₂ O ₃ is increased in this order. Among them, when Fe ₂ O ₃ is 54.0 mol%, which is less than the range of the present invention, and when 58.0 mol% is more than the range of the present invention, the Q value is low, and the change rate of μi (hereinafter referred to as “Δμi”). ") Is big. Therefore, in the present invention, the amount of Fe ₂ O ₃ is 54.1 to 57.5 mol%.
Next, sample No. As for 8-13, ZnO is increasing in this order. Among them, when ZnO is 11.0 mol%, which is more than the range of the present invention, the Q value is low and Δμi is large. Therefore, in this invention, the amount of ZnO shall be 0-10.5 mol% (however, 0 is not included).
From the above results, when the present invention is applied to MnZn ferrite, in order to combine a high Q value and a low Δμi, Fe ₂ O ₃ ranges from 54.1 to 57.5 mol%, and ZnO ranges from 0 to 0. It can be seen that it is important to set the amount within the range of 10.5 mol% (excluding 0).
An example in which the present invention is applied to Mn ferrite not containing Zn is shown in the sixth embodiment.

(Second embodiment)
In the second embodiment, fluctuations in Qmin and Δμi accompanying fluctuations in the Co content are confirmed.
To prepare a ferrite core having a composition shown in Table 2 by the same procedure as in the first embodiment, Qmin and Derutamyuai, the .mu.i _min was determined under the same conditions as in the first embodiment. The results are shown in Table 2.

Sample No. 14 to 18, Co ₃ O ₄ is increased in this order. Among them, when Co ₃ O ₄ is 500 ppm, which is less than the range of the present invention, and when 4000 ppm is more than the range of the present invention, the Q value is low and Δμi is large.
Next, Sample No. with an Fe ₂ O ₃ content of 55.5 mol% was used. 19 to 21 and the sample No. having an amount of Fe ₂ O ₃ of 56.5 mol%. When focusing on Nos. 22 to 25, sample Nos. In which the amount of Co ₃ O ₄ is in the range of 1000 to 3800 ppm. 22 to 25 all have a Q value of 200 or more. At the same time, sample no. 22 to 25 show the characteristic that Δμi is 20% or less in absolute value.
From the above results, in order to combine a high Q value and a low Δμi, it is important to set the amount of Co ₃ O ₄ in the range of 1000 to 3800 ppm when the present invention is applied to MnZn-based ferrite. Was confirmed. The desirable amount of Co ₃ O ₄ when the Q value is emphasized is 1000 to 2800 ppm, preferably 1200 to 2500 ppm. The preferable amount of Co ₃ O ₄ when Δμi is important is 1000 to 2500 ppm, preferably 1300 to 2500 ppm.

(Third embodiment)
In the third example, the variation of the Q value and Δμi accompanying the variation of the Si and Ca contents is confirmed.
To prepare a ferrite core having a composition shown in Table 3 in the same procedure as in the first embodiment, Qmin and Derutamyuai, the .mu.i _min was determined under the same conditions as in the first embodiment. The results are shown in Table 3.

Sample No. 26 to 30, SiO ₂ is increased in this order. Among them, when SiO ₂ is 50 ppm, which is less than the range of the present invention, Δμi shows a good value, but Qmin is as low as 180. On the other hand, when SiO ₂ is 1000 ppm, which is larger than the range of the present invention, Qmin decreases to 85. Therefore, in the present invention, the Si amount is set to 60 to 800 ppm in terms of SiO ₂ . A desirable amount of Si is 70 to 600 ppm, more desirably 100 to 500 ppm in terms of SiO ₂ .

Sample No. 31 to 34, CaCO ₃ is increasing in this order. Among them, when CaCO ₃ is 500 ppm, which is less than the range of the present invention, and CaCO ₃ is 5000 ppm, which is greater than the range of the present invention, Qmin is low. Therefore, in the present invention, the amount of Ca is set to 600 to 4000 ppm in terms of CaCO ₃ . The desirable amount of Ca is 600 to 3500 ppm, more desirably 1200 to 3500 ppm in terms of CaCO ₃ .

(Fourth embodiment)
In the fourth example, fluctuations in the Q value and Δμi accompanying the inclusion of Ti and Sn are confirmed.
To prepare a ferrite core having a composition shown in Table 4 to the same procedure as in the first embodiment, Qmin and Derutamyuai, the .mu.i _min was determined under the same conditions as in the first embodiment. The results are shown in Table 4.

Sample No. 35 to 38, TiO ₂ has increased in this order. Sample No. 35 (without TiO ₂ content) and sample no. From the comparison of 36 (TiO ₂ : 2000 ppm), it can be seen that Δμi is reduced by containing TiO ₂ . However, when the content of TiO ₂ becomes 7000 ppm (sample No. 38), Δμi becomes larger than that without TiO ₂ (sample No. 35), and Qmin also decreases. Therefore, in the present invention, the amount of TiO ₂ is set to 0 to 5000 ppm. Desirable amount of TiO ₂ is 500～4000Ppm, more preferably TiO ₂ amount is 500～3000Ppm.
All the samples shown in the first to third examples described above contained TiO ₂ . From 35, even if it does not contain TiO _{2, by} setting the other components within the range recommended by the present invention, it is possible to combine Qmin of 200 or more and Δμi of 20% or less in absolute value. Therefore, in the present invention, the inclusion of TiO ₂ is not essential and is optional.

Sample No. 35,39～41 is, SnO ₂ has increased in this order. First, sample no. 35 (no SnO ₂ content) and sample no. Comparison of 39 (SnO ₂ : 2000 ppm) shows that Δμi is reduced by containing SnO ₂ . However, when the content of SnO ₂ reaches 7000 ppm (sample No. 41), Qmin decreases. Therefore, in the present invention, the amount of SnO ₂ is set to 0 to 5000 ppm. Preferably SnO ₂ weight 500～4000Ppm, more preferably the amount of SnO ₂ is 500～3000Ppm.
Sample No. From 35, even when SnO ₂ is not contained, by setting other components within the range recommended by the present invention, it is possible to combine Qmin of 200 or more and Δμi of 20% or less in absolute value. Therefore, the inclusion of SnO ₂ is not essential in the present invention and is optional.

(5th Example)
In the fifth embodiment, fluctuations in the Q value and Δμi accompanying the contents of Ta, Nb, and Zr are confirmed.
To prepare a ferrite core having a composition shown in Table 5 to the same procedure as in the first embodiment, Qmin and Derutamyuai, the .mu.i _min was determined under the same conditions as in the first embodiment. The results are shown in Table 5.

Sample No. In 42 to 45, Ta ₂ O ₅ increases in this order. Sample No. 42 (without Ta ₂ O ₅ content) and sample no. From the comparison of 43 (Ta ₂ O ₅ : 1000 ppm), it can be seen that the inclusion of Ta ₂ O ₅ also improves Qmin. However, when the content of Ta ₂ O ₅ is 4000 ppm (sample No. 45), Δμi becomes larger than that when no Ta ₂ O _{5 is} contained (sample No. 42), and Qmin is significantly reduced. . Therefore, in the present invention, the amount of Ta ₂ O ₅ is set to 0 to 3000 ppm. A desirable amount of Ta ₂ O ₅ is 0 to 2500 ppm, and a more desirable amount of Ta ₂ O ₅ is 500 to 2000 ppm.

Sample No. In 42, 46, and 47, Nb ₂ O ₅ increases in this order. First, sample no. 42 (Nb ₂ O _{5 not} contained) and Sample No. Comparison of 46 (Nb ₂ O ₅ : 300 ppm) shows that Qmin is improved while maintaining a smaller Δμi by containing Nb ₂ O ₅ . However, when the content of Nb ₂ O ₅ is 700 ppm (sample No. 47), the effect of improving Qmin while suppressing the deterioration of Δμi cannot be enjoyed. Therefore, in the present invention, the amount of Nb ₂ O ₅ is set to 0 to 500 ppm. A desirable amount of Nb ₂ O ₅ is 0 to 400 ppm, and a more desirable amount of Nb ₂ O ₅ is 50 to 350 ppm.

Sample No. In 42, 48 and 49, ZrO ₂ increases in this order. First, sample no. 42 (without ZrO ₂ content) and Sample No. Comparison of 48 (ZrO ₂ : 300 ppm) shows that Qmin is improved while maintaining a smaller Δμi by containing ZrO ₂ . However, when the content of ZrO ₂ is 700 ppm (sample No. 49), Qmin is significantly reduced. Therefore, in the present invention, the amount of ZrO ₂ is set to 0 to 500 ppm. A desirable amount of ZrO ₂ is 0 to 400 ppm, and a more desirable amount of ZrO ₂ is 50 to 350 ppm.

(Sixth embodiment)
Although the example which applied this invention to the MnZn type | system | group ferrite was shown in the above 1st-5th Example, the experimental example which applied this invention to Mn ferrite is shown as a 6th Example.

To prepare a ferrite core having a composition shown in Table 6 by the same procedure as in the first embodiment, Qmin and Derutamyuai, the .mu.i _min was determined under the same conditions as in the first embodiment. The results are shown in Table 6.

Sample No. 50 (Co ₃ O ₄ : 1000 ppm) and Sample No. 51 (Co ₃ O ₄ : By comparison with 2500 ppm, even in a Mn-based ferrite not containing ZnO, by setting the amount of Co ₃ O ₄ to an appropriate range, Qmin of 200 or more and Δμi of 20% or less in absolute value can be obtained. Therefore, when the present invention is applied to a Mn-based ferrite, the amount of Co ₃ O ₄ is set to 1500 ppm or more, but even in the Mn-based ferrite, when the amount of Co ₃ O ₄ is 5000 ppm, Δμi Therefore, when the present invention is applied to Mn ferrite, the amount of Co ₃ O ₄ is set to 1500 to 4000 ppm.

  The desirable composition of the ferrite sintered body has been described in detail above. The ferrite sintered body having the composition recommended by the present invention has a small temperature dependency of the initial magnetic permeability (μi) and a large Q value. In addition, the ferrite sintered body having the composition recommended by the present invention has a high initial permeability. For this reason, according to the toroidal coil using the ferrite sintered body of the present invention, it is possible to have a higher inductance than the conventional Ni-based toroidal coil even if the number of turns of the conductor is reduced, and the toroidal coil can be downsized. be able to. Thereby, size reduction of the signal transmission apparatus provided with the toroidal coil can also be achieved.

Next, in the composition of the present invention, the temperature dependence of the toroidal coil 10 configured using the gapless magnetic core member 11 was evaluated, and the results are shown below.
Ferrite cores having the compositions shown in Table 7 were produced.

Fe ₂ O ₃ powder, MnO powder and ZnO powder were used as raw materials for the main component, and these were wet mixed and then calcined at 850 ° C. for 3 hours.
Next, the calcined product of the main component material and the subcomponent material were mixed. SiO ₂ powder, CaCO ₃ powder, Ta ₂ O ₅ powder, Co ₃ O ₄ powder, and TiO ₂ powder were selectively used as the raw materials for the accessory components. The auxiliary component raw material was added to the calcined material of the main component raw material and mixed while being pulverized. The pulverization was performed until the average particle size of the calcined product was about 1.0 μm. A binder was added to the resulting mixture, granulated, and then molded to obtain a toroidal shaped molded body.
Here, the molded body had an outer diameter of 20 mm, an inner diameter of 10 mm, and a thickness of 5 mm.

The obtained molded body was fired at a temperature of 1150 ° C. (stable part 5 hours, stable part oxygen partial pressure 0.5%) under oxygen partial pressure control to obtain a ferrite core. Sample No. For 54, 55, and 56, a gapless core and a core formed with a 0.3 mm gap after sintering were prepared.
Then, the initial permeability μi (measurement frequency: 100 kHz) of the ferrite core in the range of −40 ° C. to 130 ° C. was measured. Furthermore, the absolute value Δμi of the rate of change of the initial permeability μi in the range of −40 ° C. to 130 ° C. was obtained with the initial permeability μi at 20 ° C. as a reference.

FIG. 53 and Sample No. 54 is a diagram for comparing Sample No. 54 and FIG. 53 and Sample No. FIG. 5 is a diagram for comparing No. 55 and FIG. 53 and Sample No. 56 are diagrams for comparing 56, (a) is a measured value of the initial permeability μi, and (b) is a diagram showing an absolute value Δμi of the rate of change of the initial permeability μi.
As shown in FIG. 3 to FIG. In 54 to 56, when the ferrite core is made gapless, the initial permeability varies as the temperature increases, and the temperature dependence of the initial permeability is very high. Sample No. In 54 to 56, when the gap is provided, the initial permeability is stable even if the temperature is changed, and the temperature dependence of the initial permeability is low, but the initial permeability itself is very low. You can see that As a result, sample no. In 54 to 56, it is necessary to provide a gap in order to reduce the temperature dependence of the initial permeability. However, in order to obtain a high inductance equivalent to that of the gapless ferrite core, the conductor 12 is compared with the gapless case. It is necessary to increase the number of turns.
In contrast, Sample No. having the composition of the present invention. 53, in the toroidal coil constructed using the gapless ferrite core, the initial permeability is stable even when the temperature changes, and the temperature dependence of the initial permeability is low, and the samples 54 to Compared to 56, it is clear that the initial permeability itself is high. Thereby, compared with the samples 54-56, the toroidal coil which has an equivalent inductance can be formed with a copper wire with fewer turns.

It is a figure for demonstrating the basic composition of a toroidal coil. It is a figure for demonstrating the basic composition of a signal transmission apparatus. In Example 2, sample no. 53 and sample no. 54 is a diagram showing a measured value of the initial permeability μi, and FIG. 5B is a diagram showing an absolute value Δμi of a change rate of the initial permeability μi. In Example 2, sample no. 53 and sample no. FIG. 5A is a diagram showing a measured value of initial permeability μi, and FIG. 4B is a diagram showing an absolute value Δμi of a change rate of initial permeability μi. In Example 2, sample no. 53 and sample no. 56 is a graph showing a measured value of the initial permeability μi, and FIG. 5B is a diagram showing an absolute value Δμi of a change rate of the initial permeability μi. It is a figure for demonstrating the structure of the conventional toroidal coil, (a) is an external view, (b) is an example of the magnetic core member which has a gap, (c) is a figure which shows the example of a gapless magnetic core member. is there.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Toroidal coil, 11 ... Magnetic core member (ferrite sintered body), 12 ... Conductor, 20 ... Capacitor 30 ... Conductor, 100 ... Signal transmission apparatus

Claims (12)

An annular ferrite sintered body continuous in the circumferential direction;
A conductor wound around the ferrite sintered body,
The ferrite sintered body is
Fe ₂ O ₃ : 54.1 to 57.5 mol%, the balance being substantially composed of MnO as the main component, Si as a subcomponent, 60 to 800 ppm in terms of SiO ₂ , Ca to 600 to 4000 ppm in terms of CaCO ₃ , and Co ₃ A toroidal coil containing 1500 to 4000 ppm of O ₄ . An annular ferrite sintered body continuous in the circumferential direction;
A conductor wound around the ferrite sintered body,
The ferrite sintered body is
Fe ₂ O ₃ : 54.1 to 57.5 mol%, ZnO: 10.5 mol% or less (however, not including 0), the balance being substantially composed of MnO as the main component, and Si as the subcomponent in terms of SiO ₂ of 60 ～800Ppm, toroidal coil, characterized in that 600~4000ppm the Ca in terms of CaCO _3, and the Co ₃ O ₄ containing 1000～3800Ppm.   3. The toroidal coil according to claim 1, wherein an absolute value of a rate of change of initial permeability in a range of −40 ° C. to 130 ° C. is 20% or less with reference to initial permeability at 20 ° C. 4. .   4. The toroidal coil according to claim 3, wherein the ferrite sintered body has an initial permeability in a range of −40 ° C. to 130 ° C. of 500 or more. 5. The ferrite sintered body contains 5000 ppm or less (including 0) of TiO ₂ and / or 5000 ppm or less (including 0) of SnO _{2. 5.} The toroidal coil as described. The ferrite sintered body contains Ta ₂ O ₅ of 3000 ppm or less (including 0), Nb ₂ O ₅ of 500 ppm or less (including 0), and ZrO ₂ of 500 ppm or less (including 0). The toroidal coil according to claim 1, comprising at least one kind. An annular shape continuous in the circumferential direction, containing Fe ₂ O ₃ and MnO as main components, and the absolute value of the rate of change of the initial permeability in the range of −40 ° C. to 130 ° C. with reference to the initial permeability at 20 ° C. A toroidal coil in which a conductor is wound around a ferrite sintered body having a thickness of 20% or less and mounted on a substrate;
And a capacitor mounted on the substrate in parallel or in series with the toroidal coil.   8. The electric circuit element according to claim 7, wherein the toroidal coil and the capacitor are mounted in parallel on the substrate and function as a resonance circuit or a filter circuit. The ferrite sintered body is Fe ₂ O ₃ : 54.1 to 57.5 mol%, the balance is essentially MnO as a main component, Si as an auxiliary component is 60 to 800 ppm in terms of SiO ₂ , and Ca is in terms of CaCO ₃ . The electric circuit element according to claim 7 or 8, wherein the electric circuit element contains 600 to 4000 ppm and 1500 to 4000 ppm of Co ₃ O ₄ . The ferrite sintered body is composed of Fe ₂ O ₃ : 54.1 to 57.5 mol%, ZnO: 10.5 mol% or less (however, not including 0), and the balance is mainly composed of MnO as a subcomponent. 60~800ppm of Si in terms of SiO _2, 600～4000Ppm the Ca in terms of CaCO _3, and an electric circuit device according to claim 7 or 8, characterized in that the Co ₃ O ₄ containing 1000～3800Ppm. A toroidal coil in which a conductor is wound around an annular ferrite sintered body that is continuous in the circumferential direction, and a resonance circuit composed of a capacitor connected in parallel to the toroidal coil;
A lead wire that passes through the annular ferrite sintered body and transmits an AC signal to and from the resonance circuit,
The ferrite sintered body is Fe ₂ O ₃ : 54.1 to 57.5 mol%, the balance is essentially MnO as a main component, Si as an auxiliary component is 60 to 800 ppm in terms of SiO ₂ , and Ca is in terms of CaCO ₃ . A signal transmission device comprising 600 to 4000 ppm and 1500 to 4000 ppm of Co ₃ O ₄ . A toroidal coil in which a conductor is wound around an annular ferrite sintered body that is continuous in the circumferential direction, and a resonance circuit composed of a capacitor connected in parallel to the toroidal coil;
A lead wire that passes through the annular ferrite sintered body and transmits an AC signal to and from the resonance circuit,
The ferrite sintered body is composed of Fe ₂ O ₃ : 54.1 to 57.5 mol%, ZnO: 10.5 mol% or less (however, not including 0), and the balance is mainly composed of MnO as a subcomponent. A signal transmission device comprising Si in a range of 60 to 800 ppm in terms of SiO ₂ , Ca in a range of 600 to 4000 ppm in terms of CaCO ₃ , and Co ₃ O ₄ in a range of 1000 to 3800 ppm.

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