Patent Application
20140300439
1. Technical Field
The present disclosure relates to a wire rod for inductor used for a winding of an inductor, and an inductor using such a wire rod.
2. Background Art
As a wire rod for windings for manufacturing an inductor, a wire rod having an insulating layer provided outwardly of an electrical conductor such as copper is commonly used.
Wire rods having a magnetic material plated on a surface of such an electrical conductor are also known. It has been disclosed that, with an inductor using such a wire rod, in a 1 MHz frequency band, there is an effect of increasing an inductance by approximately 10% (e.g., see Japanese Laid-open Patent Publication No. S62-211904).
The quality of an inductor is generally expressed by a Q factor (Q factor=2π×frequency×inductance Ls/wire-wound resistance Rs) being high. In the aforementioned document, it is described that an inductance L increases, but its relationship with respect to a resistance value R is not known. Also, in the aforementioned document, a relationship with respect to a material or a thickness of the magnetic layer is not described. On the other hand, regarding a resonant circuit disclosed in the document, it is described that the Q factor is lowered, but there is no description about increasing the Q factor (i.e., lowering a resistance value).
It is an object of the present disclosure to provide, by taking the aforementioned background art into consideration, a wire rod for inductor and an inductor that can improve a Q factor by further taking a resistance value into account when providing a magnetic layer on a surface of the electrical conductor.
In order to achieve the above mentioned object, according to the present disclosure, a wire rod for inductor used for a coil of an inductor includes an electric conductor and a magnetic layer provided on a surface of the electric conductor, and the magnetic layer has a thickness of greater than 0 μm and less than or equal to 3.0 μm.
Preferably, when a usable frequency band is greater than or equal to 0.01 kHz and less than or equal to 1,000 kHz, the magnetic layer has an initial permeability of 100 to 500 expressed as a relative permeability and has a thickness of greater than 0 μm and less than or equal to 3.0 μm.
More preferably, when a usable frequency band is greater than or equal to 0.01 kHz and less than or equal to 5,000 kHz, the magnetic layer has an initial permeability of 100 to 500 expressed as a relative permeability and has a thickness of greater than 0 μm and less than or equal to 2.0 μm.
More preferably, when a usable frequency band is greater than or equal to 0.01 kHz and less than or equal to 1,000 kHz, the magnetic layer has an initial permeability of 500 to 2,000 expressed as a relative permeability and has a thickness of greater than 0 μm and less than or equal to 2.5 μm.
More preferably, when a usable frequency band is greater than or equal to 0.01 kHz and less than or equal to 1,000 kHz, the magnetic layer has an initial permeability of 500 to 2,000 expressed as a relative permeability and has a thickness of greater than 0 μm and less than or equal to 2.0 μm.
More preferably, when a usable frequency band is greater than or equal to 0.01 kHz and less than or equal to 5,000 kHz, the magnetic layer has an initial permeability of 500 to 2,000 expressed as a relative permeability and has a thickness of greater than or equal to 0.5 μm and less than or equal to 1.5 μm.
More preferably, the magnetic layer may be an alloy of two or more elements containing Fe of greater than or equal to 10% by weight.
Further, the magnetic layer may be made of an Fe-50Ni alloy.
Further, the magnetic layer may be made of an Fe-80Ni alloy.
Further, wherein the magnetic layer may be made of substantially Fe.
Further, the magnetic layer may have a thickness of greater than 0 μm and less than or equal to 3.0 μm, and more preferably, the magnetic layer has a thickness of greater than or equal to 1.5 μm and less than or equal to 3.0 μm.
In the above cases, the magnetic layer may be provided between the electric conductor and an insulating layer.
On the other hand, an inductor may be manufactured using the aforementioned wire rod.
According to a wire rod for inductor of the present disclosure, a wire rod for inductor used for a coil of an inductor, includes an electric conductor; and a magnetic layer that is provided on a surface of the electric conductor and the magnetic layer has a thickness of greater than 0 μm and less than or equal to 3.0 μm. That is to say, since a magnetic layer of the predetermined thickness is provided on a surface of an electric conductor, an inductance can be improved while decreasing a resistance value and increasing a Q factor, as compared to a wire rod that is not provided with a magnetic layer.
Hereinafter, a wire rod for inductor 1 of an embodiment of the present disclosure will be described with reference to the drawings.
The wire rod for inductor 1 includes an electric conductor 2 that is a core of the wire rod, a magnetic layer 3 that covers an outer side of the electric conductor 2 and an insulating layer 4 that covers a further outer periphery of the magnetic layer 3.
The electric conductor 2 has a circular cross-section and is made of copper which is a conductive material.
The magnetic layer 3 is conductive and formed to have a thickness of an order of a few to several μm, and, for example, formed to have a thickness of greater than 0 μm and less than or equal to 3.0 μm. The magnetic layer 3 is formed by a plating or the like in such a manner that it uniformly covers an entire outer periphery of the electric conductor 2. Regarding the material of the magnetic layer 3, the magnetic layer 3 is made of an alloy of two or more elements containing Fe of greater than or equal to 10% by weight. Preferably, the magnetic layer 3 is made of an Fe-50Ni alloy or an Fe-80Ni alloy.
The insulating layer 4 is, for example, an enamel insulating layer, and has a thickness of approximately 35 μm.
As shown in
A wire rod for inductor 11 shown in
A wire rod for inductor 21 shown in
Now, an experiment of an inductor using the wire rod for inductor 1 of the present embodiment will be described with reference to
In the related art, as a wire rod for inductor, a wire rod that has only an insulating layer on an outer side of an electric conductor has been used. It is known that, by plating the magnetic layer, an inductance Ls increases for a high frequency band, but a relationship with respect to the resistance value Rs of the wire rod is not known. On the other hand, in this experiment, as a result of measuring an inductance Ls and a resistance value Rs of the wire rod in terms of a material and a thickness of the magnetic layer, it was found that there is an optimum value in a relationship between them.
In this experiment, the following three types of wire rods for inductor were used.
(A) Wire rod for inductor 1A (wire size φ0.5)
Electric conductor: Mainly copper.
Magnetic layer: Alloy of mainly Fe.
Insulating enamel layer (35 μm) outwardly of the magnetic layer.
(B) Wire rod for inductor 1B (wire size φ0.5)
Electric conductor: Mainly copper.
Magnetic layer: Fe-50Ni with heat treatment.
Insulating enamel layer (35 μm) outwardly of the magnetic layer.
(C) Wire rod for inductor 1C (wire size φ0.5)
Electric conductor: Mainly copper.
Magnetic layer: Fe-80Ni without heat treatment.
Insulating enamel layer (35 μm) outwardly of the magnetic layer.
Note that in the description below, alphabets A, B and C accompanying the numerals correspond to the aforementioned wire rods for inductor (A), (B) and (C), respectively.
Initial permeabilities of the wire rods for inductor 1A, 1B and 1C were 100, 2,000 and 500, respectively, expressed in relative permeability.
Saturation flux densities (T) of the wire rods for inductor 1A, 1B, and 1C were 2.0 (T), 1.5 (T) and 0.75 (T), respectively.
As shown in
Similarly, the air core coils 30B and 30C have the same basic structure and the only difference is their wire rods (material of the magnetic layer).
With such a configuration, first, an experiment on the relationship between a frequency of a usable band and an inductance was carried out for a case where a thickness of plating was 3 μm.
From the results of the experiments shown in
(a) As shown in
Particularly, it was found that the wire rod 1B provided with an Fe-50Ni alloy (air core coil 30B, shown by reference numeral 40B) takes the highest values in the aforementioned entire frequency band (e.g., at a frequency of 1,000 kHz, an inductance of approximately double the reference numeral 41).
With the wire rod for inductance 1C (air core coil 30C, shown by reference numeral 40C) which is provided with an Fe-80Ni alloy, an inductance of a multiple of approximately 1.7 is obtained, for example, in comparison to reference numeral 41 at frequency 1,000 kHz.
(b) As shown in
Particularly, it was found that in all of the air core coils 30A, 30B and 30C, the rate of change of inductance improved in a frequency band of greater than or equal to 1,000 kHz than in a frequency band of less than or equal to 1,000 kHz. Accordingly, it can be determined that, at a high frequency band, a high inductance can be obtained by providing a magnetic layer.
Then, a change in the inductance and a change in the resistance value were measured for the aforementioned air core coils 30A, 30B and 30C for cases where the film thickness (thickness of plating) of the magnetic layer 3 was changed between 1.0 μm, 3.0 μm and 5.0 μm. Since the changes in the inductance and the resistance value vary depending on the frequency band, measurements were taken with the value of frequency being 0.01 kHz, 0.1 kHz, 1 kHz, 2 kHz, 10 kHz, 20 kHz, 100 kHz, 1,000 kHz, and 5,000 kHz. Note that a current density is 5 A/mm2.
Then, from these measurement values, the respective Q factors were calculated.
Each of
It can be seen from the graph of
However, regarding the resistance value R, as shown in
Accordingly, in order to increase the Q factor of the air core coil 30A, first, in a frequency band in which the air core coil 30A is used, it is preferable to provide the thickness of plating such that the resistance value Rs decreases by a predetermined amount with respect to a case where plating is not provided. Furthermore, it is still preferable to provide a thickness of plating to be such that the resistance value Rs is around a smallest value (or a minimum value).
Further, it can be seen that, when distinguishing between the frequency bands, in the case of the air core coil 30A used in a frequency band of greater than or equal to 5,000 kHz, it is preferable to make a thickness of the plating to be approximately 2.0 μm (greater than 1 μm and less than 3 μm).
It can be seen from the graph of
However, regarding the resistance value R, as shown in
Similarly, when viewing in a similar manner for the case where the frequency band is 5,000 kHz, as shown in
Accordingly, it is can be seen that in the case of increasing the Q factor of the air core coil 30C, it is first necessary to distinguish between the frequency bands. In other words, in the case of the air core coil 30C used in the frequency band of 1,000 kHz (greater than 100 kHz and less than 5,000 kHz), it is preferable to make a thickness of the plating to be approximately 2.0 (greater than 1 μm and less than 3 μm). Also, in the case of the air core coil 30C used in the band of greater than or equal to 5,000 kHz, it can be seen that it is preferable to make the thickness of the plating to be 1 μm (greater than 0 μm and less than 2 μm).
Further, from the aforementioned measurement results of 1,000 kHz and 5,000 kHz, it can be seen that the Q factor can be maximized (optimized) by reducing the thickness of the magnetic layer 3 as the usable frequency band becomes greater. Further, in the present measurement result, although the greatest value of the Q factor does not appear in the band of less than or equal to 1,000 kHz, it is estimated that the aforementioned relationship between the magnitude of frequency band and the thickness of magnetic layer 3 holds.
From the graph of
However, regarding the resistance value R, as shown in
Similarly, when viewing in a similar manner for the case where the frequency band is 5,000 kHz, as shown in
Accordingly, it is can be seen that in the case of increasing the Q factor of the air core coil 30B, it is first necessary to distinguish between the frequency bands. In other words, in the case of the air core coil 30B used in the frequency band of 1,000 kHz (greater than 100 kHz and less than 5,000 kHz), it is preferable to make a thickness of the plating to be approximately 2.0 μm (greater than 1 μm and less than 3 μm). Also, in the case of the air core coil 30B used in the band of greater than or equal to 5,000 kHz, it can be seen that it is preferable to make the thickness of the plating to be 1 μm (greater than 0 μm and less than 2 μm).
Further, from the aforementioned measurement results for 1,000 kHz and 5,000 kHz, it can be determined that the Q factor can be maximized (optimized) by reducing the thickness of the magnetic layer 3 as the usable frequency band increases. Further, in the present measurement result, although the greatest value of the Q factor does not appear in the band of less than or equal to 1,000 kHz, it is estimated that the aforementioned relationship between the magnitude of frequency band and the thickness of magnetic layer 3 holds.
Focusing on the relative permeability, from the results of
It can be seen that, in a case where the relative permeability is 500 to 2,000, a good Q factor can be obtained with the frequency band of 0.01 kHz to 1,000 kHz when the thickness of plating is greater than 0 μm and less than or equal to 2.5 μm, and more preferably, greater than or equal to 0.5 μm and less than or equal to 2.0 μm (
According to the wire rod for inductor of the embodiment of the present disclosure, since the wire rod for inductor 1 (11, 21) used for a coil 30A, 30B, 30C of an inductor includes a magnetic layer 3 (13, 23) having a thickness of greater than 0 μm and less than or equal to 3.0 μm that is provided on a surface of the electric conductor 2 (12, 22), an inductance Ls of the coil 30A, 30B, 30C can be increased while decreasing the resistance value R, and an Q factor can be improved as compared to a case of a wire rod provided with no magnetic layer 3 (13, 23).
The magnetic layer 3 (13, 23) is made of an alloy of two or more elements containing Fe of greater than or equal to 10% by weight, specifically, an Fe-50Ni alloy or an Fe-80Ni alloy, the magnetic layer 3 (13, 23) can be easily formed by plating or the like.
On the other hand, since the thickness of the magnetic layer 3 (13, 23) of an Fe-50Ni alloy or an Fe-80Ni alloy is decreased as the usable frequency band increases, it is possible to achieve a high Q factor by taking an increase in the inductance Ls and an increase or a decrease in the resistance R into consideration. That is to say, an optimum Q factor can be realized.
Also, in a case where the usable frequency band is greater than or equal to 5,000 kHz, since the thickness of the magnetic layer of an alloy of two or more elements containing Fe of greater than or equal to 10% by weight is made to be greater than 1 μm and less than 3 μm, it is possible to achieve a high Q factor by taking an increase in the inductance Ls and an increase or a decrease in the resistance R into consideration.
Further, in a case where the usable frequency band is greater than 100 kHz and less than 5,000 kHz, since the thickness of the magnetic layer 3 (13, 23) of an Fe-50Ni alloy or an Fe-80Ni alloy is made to be greater than 1 μm and less than 3 μm, it is possible to achieve a high Q factor by taking an increase in the inductance Ls and an increase or a decrease in the resistance R into consideration.
Further, in a case where the usable frequency band is greater than or equal to 5,000 kHz, since the thickness of the magnetic layer 3 (13, 23) of an Fe-50Ni alloy or an Fe-80Ni alloy is made to be greater than 0 μm and less than 2 μm, it is possible to achieve a high Q factor by taking an increase in the inductance Ls and an increase or a decrease in the resistance R into consideration.
Also, considering
Within the range of the aforementioned relative permeability, by making this value to a lower value (around 100 to 500), a wire rod for inductor having a low rate of increase of Q factor but a high Q factor at a frequency of up to around 5,000 kHz can be obtained within a relatively broad range of thickness of plating of around 0.5 to 2.5 μm.
Also, when this value is made high (around 500 to 2,000), a very high Q factor can be obtained at a frequency of up to around 5,000 kHz in a range of the thickness of plating of 0.5 to 1.5 μm. By making the frequency band to be up to around 1,000 kHz, an even higher Q factor can be obtained with a thickness of plating of 0.5 to 3.0 μm.
In such cases, since the magnetic layer 3 (13) is provided between the electric conductor 2 (12) and the insulating layer 4 (14), the magnetic layer 3 (13) can be easily formed by plating on the electric conductor 2 (12) made of copper.
Also, by manufacturing the inductor using the aforementioned wire rod for inductors 1, 11, 21, it is possible to achieve a high Q factor by taking an increase in the inductance Ls and an increase or a decrease in the resistance R into consideration.
The wire rod for inductor 1 (11, 21) of the embodiment of the present embodiment has been described above. However, the present disclosure is not limited to the aforementioned embodiments, and various modifications and alterations can be made based on a technical spirit of the present invention.
For example, in an experimental example of the air core coils 30A, 30B and 30C, data are measured using a single air core coil. However, as an applied example, as shown in
When a voltage E was applied across the transmitter coil 50B, an electric current I2 flowing through the receiver coil 50A can be expressed as:
I
2
=E×jwM/((R1+jwL1)(R2+jwL2)+(wM)2),
An electromotive force E2 of the receiver coil 50A can be expressed as:
E
2
=−jwM.
Thus, a transmission power W can be expressed as:
W=E
2
I
2=(wM)2/((R1+jwL1)(R2+jwL2)+(wM)2).
Since Q1=wL1/R1 Q2=wL2/R2,
a component of the denominator can be expressed as:
(R1+jwL1)(R2+jwL2)=(1/wQ1L2+jL1/wL2)(1/wQ2L1+jL2/wL1).
That is to say, the electric power W to be transmitted can be increased by increasing the Q factor (Q1, Q2) of the aforementioned equation.
Note that the aforementioned embodiment is shown by way of example, and in addition, it is also applicable to an antenna coil, signals utilizing electromagnetic induction and magnetic resonance, or an electric power transmission coil, and enables an efficient signal and electric power transmission.
In the first embodiment described above, the magnetic layer 3 (13, 23) made of an alloy containing a predetermined amount of Fe metal was taken as an example. In addition, the inventors have found that an attractive force can be increased in a case where the magnetic layer is made of Fe alone as compared to a case where the wire rod for inductor is provided with no magnetic layer.
A wire rod for inductor 161 includes an electric conductor 162 which is a core of the wire rod, a magnetic layer 163 that covers an outer side of the electric conductor 162, a metal layer 164 that covers a further outer periphery of the magnetic layer 163, and an insulating layer 165 that covers a further outer periphery of the metal layer 164. In other words, the magnetic layer 163 is provided between the electric conductor 162 and the metal layer 164. In this embodiment, a wire size of the wire rod for inductor 161 is, for example, φ0.5.
The magnetic layer 163 is made of a magnetic layer which is a film made of Fe (single element). The film thickness of the magnetic layer is greater than 0 μm and less than or equal to 3.0 μm and preferably greater than or equal to 1.5 μm and less than or equal to 3.0 μm. The metal layer 164 is preferably formed with a thickness of an order of several μm, and, for example, made of Ni.
From the graph of
With the wire rod for inductor according to the present embodiment, since the magnetic layer 163 is formed by a layer made of Fe, the Q factor of the air-core coil 170a can be increases as compared to a case in which the magnetic layer 163 is not provided. In the case of the coil 170b in which the ferrite core is used, a high Q factor that is greater than or equal to double the Q factor of the air-core coil 170a can be achieved in the aforementioned frequency band.
In the present embodiment, the magnetic layer 163 is made of Fe. However, it is not limited thereto, and may be made of substantially Fe. An effect similar to the above can be achieved with the present configuration.
In the present embodiment, Fe only, an alloy mainly containing Fe or an Fe—Ni alloy was used for forming the magnetic layer. However, it is not limited thereto, and any material can be used as long as a magnetic substance can be made.
This is a continuation application of International Patent Application No. PCT/JP2011/072829 filed Oct. 4, 2011, the full content of which is hereby incorporated by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2011/072829 | Oct 2011 | US |
| Child | 14244512 | US |
