JP3655700B2 - Current sensor - Google Patents

Description

【００１２】
で表される。ただし、（２）式においてＡはコア断面積、Ｎは１次コイルのターン数、Ｌｃはコア部の周長（コア全周長Ｌ₀ −ギャップ長さＬg ）、μr はコア材料の透磁率、μ₀ は真空透磁率である。
【００１３】
一方、ギャップがない場合は、１次コイルへの印加電流ｉs による磁束φ₀ は
【００１４】
【数２】

【００１５】
となる。
コアを部分的に飽和させることによって、図４のギャップに相当する飽和領域を作ったとき、その飽和領域の形成によって１次コイルから２次コイルへの信号伝達を１／１０にすることができれば、電流センサとして十分に機能させることができる。
【００１６】
すなわち、
【００１７】
【数３】

【００１８】
となればよいわけであるが、そのためには、
Ｌg ＞（９／μr ）×Ｌ₀ ・・（５）
にわたって飽和領域を形成すればよいことになる。例えばリングコアの直径（最外径）を９．６ｍｍとし、μr を２０００とすると、コア中に長さ０．１４ｍｍの飽和領域を形成すればよことになる。
【００１９】
次に、このような飽和領域を、コアの周囲に局部的に集中して信号線を外巻きすることによって形成し得るかについて検討する。
図５（Ａ）に模式的外観図を、（Ｂ）にそのＢ−Ｂ断面図を示すように、薄膜からなるリングコアに対して信号線を外巻きしたモデルを考える。この場合、信号線とコアの関係は同図（Ｃ）に模式的に示され、各信号線の半径をＲ、コア薄膜と最下層の信号線との間の絶縁層の厚さをｔ、コア薄膜の厚さをＴとして、コア薄膜の中心から各信号線までの距離をｒとすると、信号線に電流ｉが流れることによって１ターン当たりの信号線が発生する磁界のコア薄膜に平行な成分Ｈx は、
【００２０】
【数４】

【００２１】
で表される。ただし、Ｈx の単位はＯｅである。コア薄膜が１Ｏｅで飽和するとすれば、（６）式で示される１ターン当たりの磁界を信号線のターン数だけ合成した磁界ΣＨx が１Ｏｅ以上となればよいことになる。
【００２２】
図６に、信号線を６ターン単層巻きとし、図５のモデルにおける信号線の半径Ｒを０．０５ｍｍ、コア薄膜の厚さＴを２０μ、信号線に流れる電流ｉを５０ｍＡとしたとき、絶縁層の厚さｔのみを変更した場合の電流ｉによる発生磁界ΣＨx の計算結果を示す。
【００２３】
この図６より、絶縁層の厚さｔを５００μｍ以下としたとき、発生磁界ΣＨx は１Ｏｅを越える。
次に、上記した条件のもとに、絶縁層の厚さｔを５００μｍとしたとき、図５に示したようにコア薄膜の中央を原点としたｘ方向各点での磁界を計算すると、図７に示す通りとなる。
【００２４】
この図７から明らかなように、コア薄膜に対して、厚さ５００μｍの絶縁層を介して半径０．０５ｍｍの信号線を６ターン単層で外巻きすることにより、この信号線に５０ｍＡの電流が流れたとき、コア材料の透磁率μr を２０００、コア直径を９．６ｍｍとして前記した（５）式を計算して得られる０．１４ｍｍ（±７０μｍ）の長さの飽和領域を十分に形成することができる。
【００２５】
そして、他の条件を上記と同等にして、信号線を絶縁層に密着して６ターン、その上に４ターンの２層巻き合計１０ターンとするとともに、絶縁層の厚さｔを９００μｍとした場合には、ｘ方向各点での磁界は図８に示す通りとなり、リングコア中に±２００μｍ（０．４ｍｍの長さ）にわたって飽和領域を形成することが可能となり、１次コイルから２次コイルへの信号伝達を十分に減衰させることができる。
【００２６】
【発明の実施の形態】
図１は本発明の実施の形態の構成図で、全体構成を示す模式的平面図（Ａ）と、そのそのＢ矢視図（Ｂ）並びにＣ−Ｃ拡大断面図（Ｃ）である。なお、図１（Ａ）は、可飽和磁性体リングコア よりも上方に存在する石英基板１ｂおよび絶縁層４を透視した状態で示している。
【００２７】
この例においては、図１（Ｃ）に示すように、石英基板１ａの上に絶縁層２を介して薄膜からなる可飽和磁性体リングコア３が形成されており、その可飽和磁性体リングコア３の上に絶縁層４を介して更に石英基板１ｂを配置しているとともに、各絶縁層２，４内に、それぞれが薄膜からなる励振用１次コイル５と受信用２次コイル６を形成している。励振用１次コイル５および受信用２次コイル６は、図１（Ａ）に模式的に示されるように、可飽和磁性体リングコア３の内側および外側において絶縁層２，４を貫通して、それぞれがつる巻き状にリングコア３に巻回されているものであり、その製法の詳細は後述する。
【００２８】
被覆導線からなる信号線７は、可飽和磁性体リングコア３を挟み込んだ上下の石英基板１ａ，１ｂの外側に局部的に集中して巻きつけられ、これによって可飽和磁性体リングコア３を外巻きしている。この信号線７の直径は５０μｍであり、石英基板１ａ，１ｂに６ターン、その直上に４ターンの合計１０ターンの２層巻きとしている。
【００２９】
石英基板１ａおよび１ｂの厚さはそれぞれ５００μｍであり、絶縁層２および４の厚さはそれぞれ４００μｍ以下であり、従って可飽和磁性体リングコア３と信号線７間に介在する絶縁層全体の厚さは９００μｍ以下となっている。
【００３０】
可飽和磁性体リングコア３の材質は、高透磁率材料であれば任意であるが、例えばパーマロイやＣo 系材料とすることができ、これらを使用することによって１Ｏｅ程度の磁界が作用することにより飽和する。また、この例において可飽和磁性体リングコア３の最外周の直径は９．６ｍｍ、最内周の直径は７．６ｍｍであり（中心直径８．６ｍｍ）、その膜厚は２０μｍである。
【００３１】
また、励振用１次コイル５および受信用２次コイル６の材質については、例えばＣu 等を用いることができる。
以上の実施の形態においては、励振用１次コイル５には外部回路から高周波信号が励振信号として供給され、これによってリングコア３中に磁束が発生し、受信用２次コイル６に高周波信号が伝達される。受信用２次コイル６の両端は、例えば検波器ないしは整流回路に接続され、その検波器ないしは整流回路の出力かに基づいて信号線７に電流が流れているか否かが判別される。
【００３２】
信号線７に電流が流れていない状態では、高透磁率材料からなる可飽和磁性体リングコア３を介して励振用１次コイル５に供給されている高周波信号が高い伝達率のもとに受信用２次コイル６に伝達される。
【００３３】
信号線７に５０ｍＡの電流が流れると、前記した図８に示した通り、その電流が発生する磁界により、可飽和磁性体リングコア３には、信号線７の直下部分においてｘ方向に４００μｍ（±２００μｍ）の長さにわたって１Ｏｅ以上の磁界が作用する。この可飽和磁性体リングコア３の材質を先に例示したように１Ｏｅ以上の磁界で飽和する材料としておけば、このリングコア３には長さ４００μｍにわたる飽和領域が形成される。リングコア３中にこのような部分的な飽和領域が形成された状態では、その部分の透磁率が非常に小さくなり、励振用１次コイル５に供給される高周波信号により発生する磁束φg は、飽和領域が形成されない状態での磁束をφ₀ としたとき、前記した（１）〜（３）式に準じて、
【００３４】
【数５】

【００３５】
に減衰する。ここで、Ｌ₀ はリングコア３の全周長であり、Ｌg は飽和領域の周方向長さ、Ｌc ＝Ｌ₀ −Ｌg 、μｒは可飽和磁性体リングコア３の透磁率であって、Ｌ₀ ＝π×８．６ｍｍ、μｒを２０００としたとき、前記したように４００μｍの飽和領域が形成されると、φg ／φ₀ は約０．０３２となる。
【００３６】
従って、信号線７に５０ｍＡの電流が流れると、受信用用２次コイル６に伝達される高周波信号は、信号線７に電流が流れていない状態に比して３／１００に減衰し、これによって信号線７への通電を検知することが可能となる。
【００３７】
以上の実施の形態において特に注目すべき点は、信号線は可飽和磁性体リングコアに対して外巻きされるが故にリングコア内を通す必要がなくなる点と、リングコアはこの信号線によって部分的に飽和させるために、その巻き数も従来に比して大幅に少なくすることができ点であり、これらによって実際の素子の製造に要する工数を大幅に低減することができる。
【００３８】
また、信号線がリングコア全体を外巻きすることによって、１本の信号線から発生する磁界のリングコアに対して作用する強度は、従来の構成に比して約２倍となりまた、飽和領域はリングコアの２箇所において形成されるため、実際には前記した計算よりも大きな信号減衰量を見込むことができる。
【００３９】
更に、以上の実施の形態のように、可飽和磁性体リングコアおよび励振用１次コイル並びに受信用２次コイルからなる薄膜部を、２枚の石英基板によって挟み込んだ状態で、外側に信号線を巻き付けた構成を採用することにより、信号線と薄膜部との絶縁耐圧を大きくとれるという利点がある。
【００４０】
次に、以上の本発明の実施の形態の製造方法の例について述べる。
図２はその製造手順の説明図である。
まず、石英基板１ａの表面にＣu をスパッタによって成膜した後パターニングすることにより、励振用１次コイル５および受信用２次コイル６の下層側のパターンＰu を形成し、パターン間をポリイミド等の絶縁材料Ｉ₁ によって平坦化する（Ａ）。このパターンＰu は、各コイル５または６について図３（Ａ）に例示されるようなパターンとする。次に、（Ｂ）に示すように、更にその上にポリイミド等によって絶縁層Ｉ₂ を形成した後、パーマロイ等の高透磁率材料を成膜して可飽和磁性体リングコア３をパターニングする。
【００４１】
次に、その上方から全体的に絶縁層Ｉ₃ を形成した後（Ｃ）、絶縁層Ｉ₂ ，Ｉ₃ をイオンミリング等でエッチングし、（Ｄ）のようにパターンＰu の各一端部に連通するコンタクトホールｈを形成する。その後、その上から一様にＣu をスパッタによってル成膜し（Ｅ）、励振用１次コイル５および受信用２次コイル６の上層側のパターンＰa を形成する（Ｆ）。これにより、図３（Ｂ）に模式的斜視図で示すようなＣu 薄膜からなる励振用１次コイル５ないしは受信用２次コイル６が得られる。
【００４２】
その後、パターンＰa の上からポリイミド等の絶縁層Ｉ₄ を形成し、必要に応じて平坦化した後、（Ｇ）に示すようにその上から石英基板１ｂを被着して、最後に信号線７を外巻きすることにより、図１に示した構造の本発明の実施の形態を得ることができる。
【００４３】
なお、本発明は、可飽和磁性体リングコア３の寸法や材質、絶縁層２，４の厚さ、あるいは信号線７の線径やターン数等については、前記した実施の形態に限られないことは勿論であり、要は、ある一定以上の電流が信号線７に流れたときに、その電流によってリングコア３が部分的に飽和して、励振用１次コイル５から受信用２次コイル６に伝達される高周波信号が、確実に判別可能なまでに減衰するような組み合わせとすればよい。
【００４４】
【発明の効果】
以上のように、本発明によれば、薄膜製の可飽和磁性体リングコアに対して同じく薄膜製の励振用１次コイルおよび受信用２次コイルを巻回するとともに、導線からなる信号線をリングコアに対して局部的に集中して外巻きすることによって、信号線に電流が流れたときに可飽和磁性体リングコアを部分的に飽和させて受信用２次コイルへの信号伝達を減衰させるから、信号線のリングコアに対する巻き数を従来に比して大幅に減少させることができると同時に、信号線は外巻きであるが故にリングコア内を通す必要がなくなり、実素子の製作時における工数を大幅に低減することが可能となる。
【図面の簡単な説明】
【図１】本発明の実施の形態の説明図で、（Ａ）は可飽和磁性体リングコア３よりも上方に存在する石英基板１ｂおよび絶縁層４を透視した状態で示す模式的平面図、、（Ｂ）はそのＢ矢視図、（Ｃ）はそのＣ−Ｃ拡大断面図
【図２】本発明の実施の形態の製造方法の一例の手順説明図
【図３】図２の手順により得られる励振用１次コイル５または受信用２次コイル６の説明図
【図４】リングコア中に部分的な飽和領域が形成されたときに、励振用１次コイルに流れる電流により発生する磁束の変化を計算するためのモデル説明図
【図５】リングコアに対して信号線を外巻きすることによって得られる飽和領域の計算のためのモデル説明図
【図６】図５のモデルにおける絶縁層の厚さと信号線を流れる電流によるリングコア内への発生磁界との関係の計算結果の例を示すグラフ
【図７】図５のモデルにおいて絶縁層の厚さを５００μｍ、信号線のターン数を単層６ターンとしたとき、信号線を流れる電流による発生磁界のリングコア膜厚方向への分布の計算結果の例を示すグラフ
【図８】図５のモデルにおいて絶縁層の厚さを９００μｍとし、かつ、信号線の巻き数を２層１０ターンとしたとき、信号線を流れる電流による発生磁界のリングコア膜厚方向への分布の計算結果の例を示すグラフ
【符号の説明】
１ａ，１ｂ 石英基板
２，４ 絶縁層
３ 可飽和磁性体リングコア
５ 励振用１次コイル
６ 受信用２次コイル
７ 信号線[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a current sensor for detecting whether or not a current is flowing through a signal line. For example, the present invention is used as a fail-safe sensor for monitoring the movable state of a movable part such as a machine tool or an industrial robot. It relates to a suitable current sensor.
[0002]
[Prior art]
For example, in industrial robots, etc., in order to prevent dangers caused by malfunctions of robots during teaching work, maintenance and inspection work, etc., in general, the current flowing to the drive motor of the moving part of the robot is monitored and the current flows. A fail-safe mechanism or an interlock mechanism that immediately cuts off the driving power of the robot is provided.
[0003]
Conventionally, as such a current monitoring sensor, a common saturable magnetic ring core includes a signal line through which a current to be monitored flows, a primary coil for excitation to which a high frequency signal is supplied, and a secondary coil for reception. The current of the signal line is utilized by utilizing the fact that the saturable magnetic ring core is saturated by winding and current flows through the signal line, and the signal transmission from the excitation primary coil to the reception secondary coil is attenuated. There has been proposed a current sensor that detects the presence or absence of this (Japanese Patent Laid-Open No. 6-201733).
[0004]
[Problems to be solved by the invention]
By the way, in the above-mentioned proposal, the saturable magnetic ring core is in a bulk shape, and the primary and secondary coils and the signal line coil each made of a conducting wire are respectively spirally wound with respect to the ring core. That is, it is wound so as to alternately pass through the inside and outside of the ring core.
[0005]
Here, when the signal line coil is wound around the ring core, the generated magnetic field H from the signal line is N for the number of turns of the signal line coil, I for the current flowing through the signal line coil, If the circumference is L,
H = N · I / L (1)
Estimated at Now, when making a current sensor that can detect when a current of 50 mA flows through the signal line, it is necessary to saturate the saturable magnetic ring core by flowing a current of 50 mA through the signal line. In this case, if the saturable magnetic ring core is saturated with, for example, 1 Oe, and its total circumference is 24 mm, it is necessary to make 40 turns of the signal line with respect to the saturable magnetic ring core. That is, when manufacturing an actual element, it is necessary to insert a signal line 40 times in a minute ring, which requires a lot of labor and is not practical.
[0006]
An object of the present invention is to provide a current sensor of a type in which a primary coil for excitation and a secondary coil for reception are wound around a saturable magnetic ring core to detect energization to a signal line. An object of the present invention is to provide a current sensor that can reliably detect when a minute current flows and that is easy to manufacture.
[0007]
[Means for Solving the Problems]
In the current sensor of the present invention, when a primary coil for excitation to which a high-frequency signal is supplied, a secondary coil for reception, and a signal line coil are wound around a saturable magnetic ring core, and a current flows through the signal line coil In a current sensor that detects the presence or absence of current in a signal line coil by utilizing the fact that the saturable magnetic ring core is saturated and the signal transmission from the excitation primary coil to the receiving secondary coil is attenuated. The above-described object is achieved by adopting the following configuration.
[0008]
That is, as shown in FIG. 1 showing the embodiment, in the current sensor of the present invention, the primary coil 5 for excitation, the secondary coil 6 for reception, and the saturable magnetic ring core 3 are formed by thin films, respectively. The secondary and secondary coils 5 and 6 are wound around the ring core 3 alternately through the inside / outside of the ring core 3, respectively, while the signal line coil is a conductor. The signal line 7 has a structure in which the periphery of the saturable magnetic ring core 3 is externally wound while being locally concentrated.
[0009]
In the present invention, the signal line 7 is not passed through the inside of the saturable magnetic ring core 3 and the ring core 3 is externally wound, so that the winding work is reduced, and at the same time, the ring core 3 is subjected to current flowing in the signal line. Rather than saturating the whole, the ring core 3 is locally saturated to attenuate the signal transmission from the excitation primary coil 5 to the reception secondary coil 6, and thereby the ring core 3 of the signal line 7. It is also intended to reduce the number of external windings for.
[0010]
It will be proved below that such a configuration of the present invention can detect a minute current flowing through the signal line 7.
First, whether a signal transmission from the excitation primary coil to the reception secondary coil can be suppressed by saturating only a part of the ring core will be considered using a model as shown in FIG. When there is a gap of length Lg in the ring core as shown in FIG. 4, the magnetic flux φg when the current is flows through the primary coil is expressed by the following equation (2).
[0011]
[Expression 1]

[0012]
It is represented by In the equation (2), A is the core cross-sectional area, N is the number of turns of the primary coil, Lc is the circumference of the core (core total circumference L ₀ -gap length Lg), and μr is the magnetic permeability of the core material. , Μ ₀ is the vacuum permeability.
[0013]
On the other hand, when there is no gap, the magnetic flux φ ₀ due to the applied current is applied to the primary coil is:
[Expression 2]

[0015]
It becomes.
If the saturation region corresponding to the gap in FIG. 4 is created by partially saturating the core, the signal transmission from the primary coil to the secondary coil can be reduced to 1/10 by forming the saturation region. It can function sufficiently as a current sensor.
[0016]
That is,
[0017]
[Equation 3]

[0018]
However, for that purpose,
Lg> (9 / μr) × L ₀ (5)
A saturated region may be formed over the entire area. For example, if the diameter (outermost diameter) of the ring core is 9.6 mm and μr is 2000, a saturated region having a length of 0.14 mm may be formed in the core.
[0019]
Next, it will be examined whether such a saturated region can be formed by locally concentrating around the core and winding the signal line outwardly.
As shown in a schematic external view in FIG. 5A and a BB cross-sectional view in FIG. 5B, consider a model in which signal lines are wound around a ring core made of a thin film. In this case, the relationship between the signal line and the core is schematically shown in FIG. 4C, where the radius of each signal line is R, the thickness of the insulating layer between the core thin film and the lowermost signal line is t, When the thickness of the core thin film is T and the distance from the center of the core thin film to each signal line is r, the current i flows through the signal line, and the signal line per turn generates a magnetic field parallel to the core thin film. The component Hx is
[0020]
[Expression 4]

[0021]
It is represented by However, the unit of Hx is Oe. If the core thin film is saturated at 1 Oe, the magnetic field ΣHx obtained by synthesizing the magnetic field per turn represented by the equation (6) by the number of turns of the signal line should be 1 Oe or more.
[0022]
In FIG. 6, when the signal line is 6-turn single layer winding, the radius R of the signal line in the model of FIG. 5 is 0.05 mm, the thickness T of the core thin film is 20 μ, and the current i flowing through the signal line is 50 mA. The calculation result of the magnetic field ΣHx generated by the current i when only the thickness t of the insulating layer is changed is shown.
[0023]
From FIG. 6, when the thickness t of the insulating layer is 500 μm or less, the generated magnetic field ΣHx exceeds 1 Oe.
Next, when the thickness t of the insulating layer is 500 μm under the above-described conditions, the magnetic field at each point in the x direction with the center of the core thin film as the origin is calculated as shown in FIG. As shown in FIG.
[0024]
As is apparent from FIG. 7, a signal line having a radius of 0.05 mm is wound around the core thin film through a single layer of 6 turns through an insulating layer having a thickness of 500 μm, whereby a current of 50 mA is applied to the signal line. Sufficiently flows, a saturated region of a length of 0.14 mm (± 70 μm) obtained by calculating the above formula (5) with the core material having a magnetic permeability μr of 2000 and a core diameter of 9.6 mm is sufficiently formed. can do.
[0025]
Then, the other conditions were made the same as above, and the signal line was in close contact with the insulating layer to make 6 turns, and then 4 turns to make a total of 10 turns, and the thickness t of the insulating layer was 900 μm. In this case, the magnetic field at each point in the x direction is as shown in FIG. 8, and a saturation region can be formed in the ring core over ± 200 μm (0.4 mm length). Signal transmission to can be sufficiently attenuated.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a configuration diagram of an embodiment of the present invention, and is a schematic plan view (A) showing the overall configuration, a view as viewed in the direction of arrow B (B), and an enlarged cross-sectional view C-C (C). FIG. 1A shows the quartz substrate 1b and the insulating layer 4 present above the saturable magnetic ring core as seen through.
[0027]
In this example, as shown in FIG. 1C, a saturable magnetic ring core 3 made of a thin film is formed on a quartz substrate 1a via an insulating layer 2, and the saturable magnetic ring core 3 A quartz substrate 1b is further arranged on the insulating layer 4, and a primary coil for excitation 5 and a secondary coil for receiving 6 each made of a thin film are formed in each of the insulating layers 2 and 4. Yes. The excitation primary coil 5 and the reception secondary coil 6 penetrate through the insulating layers 2 and 4 inside and outside the saturable magnetic ring core 3, as schematically shown in FIG. Each is wound around the ring core 3 in a spiral shape, and details of the manufacturing method will be described later.
[0028]
The signal line 7 made of a coated conductor is locally concentrated around the upper and lower quartz substrates 1a and 1b sandwiching the saturable magnetic ring core 3 so that the saturable magnetic ring core 3 is wound outwardly. ing. The diameter of the signal line 7 is 50 μm, and two layers of total 10 turns, 6 turns on the quartz substrates 1a and 1b and 4 turns immediately above, are formed.
[0029]
The thicknesses of the quartz substrates 1a and 1b are 500 μm, respectively, and the thicknesses of the insulating layers 2 and 4 are each 400 μm or less. Therefore, the thickness of the entire insulating layer interposed between the saturable magnetic ring core 3 and the signal line 7 Is 900 μm or less.
[0030]
The material of the saturable magnetic ring core 3 is arbitrary as long as it is a high magnetic permeability material. For example, it can be a permalloy or a Co-based material, and by using these materials, a magnetic field of about 1 Oe acts and becomes saturated. To do. In this example, the diameter of the outermost periphery of the saturable magnetic ring core 3 is 9.6 mm, the diameter of the innermost periphery is 7.6 mm (center diameter 8.6 mm), and the film thickness is 20 μm.
[0031]
For example, Cu can be used as the material for the primary coil 5 for excitation and the secondary coil 6 for reception.
In the above embodiment, the excitation primary coil 5 is supplied with a high frequency signal from an external circuit as an excitation signal, thereby generating a magnetic flux in the ring core 3 and transmitting the high frequency signal to the receiving secondary coil 6. Is done. Both ends of the receiving secondary coil 6 are connected to, for example, a detector or a rectifier circuit, and it is determined whether or not a current is flowing through the signal line 7 based on the output of the detector or the rectifier circuit.
[0032]
In a state where no current flows through the signal line 7, the high frequency signal supplied to the excitation primary coil 5 through the saturable magnetic ring core 3 made of a high permeability material is received under a high transmissibility. It is transmitted to the secondary coil 6.
[0033]
When a current of 50 mA flows through the signal line 7, as shown in FIG. 8, the saturable magnetic ring core 3 is caused to have 400 μm (± A magnetic field of 1 Oe or more acts over a length of 200 μm). If the saturable magnetic ring core 3 is made of a material that is saturated with a magnetic field of 1 Oe or more as exemplified above, a saturated region having a length of 400 μm is formed in the ring core 3. In a state where such a partial saturation region is formed in the ring core 3, the magnetic permeability of that portion becomes very small, and the magnetic flux φg generated by the high-frequency signal supplied to the excitation primary coil 5 is saturated. When the magnetic flux in a state where no region is formed is φ ₀ , according to the above-described equations (1) to (3),
[0034]
[Equation 5]

[0035]
Attenuates. Here, L ₀ is the total circumference of the ring core 3, L g is the circumferential length of the saturation region, L c = L ₀ -L g, μr is the permeability of the saturable magnetic ring core 3, and L ₀ = [pi × 8.6 mm, when the 2000 .mu.r, the saturation region of 400μm as mentioned above is formed, .phi.g / phi ₀ is about 0.032.
[0036]
Therefore, when a current of 50 mA flows through the signal line 7, the high frequency signal transmitted to the receiving secondary coil 6 is attenuated to 3/100 compared to the state where no current flows through the signal line 7. Thus, it is possible to detect energization to the signal line 7.
[0037]
Particularly noteworthy in the above embodiments are that the signal line is externally wound around the saturable magnetic ring core so that it does not have to pass through the ring core, and the ring core is partially saturated by this signal line. Therefore, the number of windings can be significantly reduced as compared with the prior art, and the number of man-hours required for actual device manufacture can be greatly reduced.
[0038]
Further, when the signal line is wound around the entire ring core, the strength of the magnetic field generated from one signal line acting on the ring core is about twice that of the conventional configuration, and the saturation region is the ring core. Therefore, it is possible to expect a larger signal attenuation than the above-described calculation.
[0039]
Further, as in the above embodiment, the signal line is connected to the outside with the saturable magnetic ring core, the excitation primary coil and the reception secondary coil sandwiched between the two quartz substrates. By adopting the wound configuration, there is an advantage that the withstand voltage between the signal line and the thin film portion can be increased.
[0040]
Next, an example of the manufacturing method according to the above embodiment of the present invention will be described.
FIG. 2 is an explanatory diagram of the manufacturing procedure.
First, Cu is formed on the surface of the quartz substrate 1a by sputtering and then patterned to form a pattern Pu on the lower layer side of the primary coil 5 for excitation and the secondary coil 6 for reception. Planarization is performed with the insulating material I ₁ (A). This pattern Pu is a pattern as illustrated in FIG. 3A for each coil 5 or 6. Next, as shown in (B), an insulating layer I ₂ is further formed thereon with polyimide or the like, and then a high permeability material such as permalloy is formed to pattern the saturable magnetic ring core 3.
[0041]
Next, after the insulating layer I ₃ is entirely formed from above (C), the insulating layers I ₂ and I ₃ are etched by ion milling or the like, and communicated with each end of the pattern Pu as shown in (D). A contact hole h is formed. Thereafter, Cu is uniformly formed by sputtering from above (E), and a pattern Pa on the upper layer side of the exciting primary coil 5 and the receiving secondary coil 6 is formed (F). Thereby, the exciting primary coil 5 or the receiving secondary coil 6 made of a Cu thin film as shown in the schematic perspective view of FIG. 3B is obtained.
[0042]
Thereafter, an insulating layer I ₄ made of polyimide or the like is formed on the pattern Pa, flattened as necessary, and then a quartz substrate 1b is deposited thereon, as shown in FIG. The embodiment of the present invention having the structure shown in FIG. 1 can be obtained by externally winding 7.
[0043]
The present invention is not limited to the above-described embodiment with respect to the size and material of the saturable magnetic ring core 3, the thickness of the insulating layers 2 and 4, the wire diameter and the number of turns of the signal line 7, etc. Of course, the point is that when a certain current or more flows through the signal line 7, the ring core 3 is partially saturated by the current, and the primary coil 5 for excitation changes to the secondary coil 6 for reception. What is necessary is just to set it as the combination which attenuate | damps before the transmitted high frequency signal can be discriminate | determined reliably.
[0044]
【The invention's effect】
As described above, according to the present invention, a thin film primary coil for excitation and a secondary coil for reception are wound around a thin film saturable magnetic ring core, and a signal line made of a conductive wire is connected to the ring core. By locally concentrating and winding externally, the saturable magnetic ring core is partially saturated when current flows through the signal line, and the signal transmission to the secondary coil for reception is attenuated. The number of turns of the signal line around the ring core can be greatly reduced compared to the conventional method. At the same time, the signal line is externally wound, so there is no need to pass through the ring core, greatly increasing the man-hours required for manufacturing the actual device. It becomes possible to reduce.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an embodiment of the present invention, in which (A) is a schematic plan view showing a quartz substrate 1b and an insulating layer 4 existing above a saturable magnetic ring core 3 as seen through; (B) is a view taken along the arrow B, (C) is an enlarged cross-sectional view taken along the line C-C. FIG. 2 is an explanatory diagram of an example of the manufacturing method according to the embodiment of the present invention. FIG. 4 is an explanatory diagram of the excitation primary coil 5 or the reception secondary coil 6. FIG. 4 shows a change in magnetic flux generated by the current flowing in the excitation primary coil when a partial saturation region is formed in the ring core. FIG. 5 is a model explanatory diagram for calculating a saturation region obtained by winding a signal line around a ring core. FIG. 6 is a diagram illustrating the thickness of an insulating layer in the model of FIG. Magnetic field generated in the ring core by the current flowing through the signal line FIG. 7 is a graph showing an example of the calculation result of the relationship. FIG. 7 is a ring core of a magnetic field generated by a current flowing through a signal line when the thickness of the insulating layer is 500 μm and the number of turns of the signal line is 6 turns FIG. 8 is a graph showing an example of a calculation result of distribution in the film thickness direction. FIG. 8 shows a signal line when the thickness of the insulating layer is 900 μm and the number of turns of the signal line is 10 turns in 2 layers in the model of FIG. Showing an example of the calculation result of the distribution of the magnetic field generated by the current flowing through the ring core in the film thickness direction [Explanation of symbols]
1a, 1b Quartz substrate 2, 4 Insulating layer 3 Saturable magnetic ring core 5 Primary coil 6 for excitation Secondary coil 7 for reception Signal line

Claims (1)

A primary coil for excitation to which a high-frequency signal is supplied, a secondary coil for reception, and a signal line coil are wound around a saturable magnetic ring core, and when a current flows through the signal line coil, the saturable magnetic ring core In a current sensor that detects the presence or absence of current flowing in the signal line coil by using the fact that the signal transmission from the excitation primary coil to the reception secondary coil is attenuated and becomes saturated,
The primary coil for excitation, the secondary coil for reception, and the saturable magnetic ring core are each formed of a thin film, and the primary and secondary coils respectively pass through the inside / outside of the ring core alternately with respect to the ring core. A current sensor characterized in that a signal line coil made of a conductive wire is wound around in a helical manner and is wound around the saturable magnetic ring core in a locally concentrated manner.

Images