JPH095361A - Dc current sensor - Google Patents

Abstract

PURPOSE: To reduce the structure and power supply to an exciting coil by making a plurality of through holes, at a predetermined interval, in the circumferential direction of a detection core. CONSTITUTION: A plurality of through holes 13 are made, at a predetermined interval in the circumferential direction, in the side face of a detection core 12. An exciting coil 14 is set in the through holes 13 such that the direction of current flow is reversed between adjacent through holes. When a DC current I flows through a lead 11 to be detected, a magnetic filed H0 is induced in the detection core 12 and a flux ϕ0 is generated. A predetermined AC current is then fed through the exciting coil 14, and a field H is induced orthogonally to the field H0 . The direction of magnetization is turned in the detection core 12 based on the combined field and the flux ϕ0 is modulated. Consequently, a voltage VDET is induced in a detection coil 15 based on the circumferential component of flux in the detection core 12 incident to the variation of flux ϕ0 . More specifically, an electromotive force proportional to the current I flowing through the lead 11 to be detected is generated and detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a direct current sensor provided in equipment using various direct currents, and particularly to a current density in a plating bath for the purpose of preventing uneven plating in electroplating. The present invention relates to a direct current sensor suitable for a so-called current density measuring device for measuring and adjusting distribution, which has a simple structure and can be downsized.

[0002]

2. Description of the Related Art Conventionally, as a direct current sensor, a shunt resistance type, a mag-amp type, a magnetic multi-vibrator type, a hall element type and the like are known. But,
These DC current sensors are not only complicated in structure, but it is difficult to say that they are structures that can cope with minute current changes, and at present, they have not been put into practical use as highly sensitive DC current sensors.

In view of such a situation, the inventor of the present application has previously proposed a conventional high-sensitivity direct current sensor having a relatively simple structure and having an excellent detection ability even for a minute current change. A DC current sensor as shown in FIG. 9 having a structure completely different from that of the method was proposed (EP 0 579).
462A, JP-A-6-74978, JP-A6-1-1.
94389, JP-A-6-281674). The direct current sensor shown in FIG. 9 includes excitation core portions 4a and 4b formed of a pair of cylindrical bodies made of a soft magnetic material, and the excitation core portion 4
Each of a and 4b is formed by connecting and integrating the adjacent opening ends with a soft magnetic material, and having a detection core portion 2 formed by the connection portion and inner side surface portions of the excitation core portions 4a and 4b.
In the figure, reference numeral 1 denotes a conductor to be detected which is arranged to pass through the void portion of the detection core portion 2. Further, in the figure, 3a and 3b are a pair of detection coils, which are wound in a toroidal shape at positions facing the detection core portion 2 in the circumferential direction. Further, reference numeral 5 in the drawing denotes an exciting coil, which is wound around the outer circumference of the detection core portion 2.

In such a structure, when a direct current I flows through the conductor 1 to be detected, a magnetic field clockwise with respect to the direction of the direct current I is generated in the detection core portion 2 and a magnetic flux is generated in the detection core portion 2. Φ ₀ is generated. At this time, a predetermined alternating current is passed through the exciting coil 5 to generate a magnetic flux that periodically changes in the α direction in the figure in the pair of exciting core portions 4a and 4b.
When a and 4b are magnetically saturated periodically, the core crossing portion 6 which is a part of the detection core portion 2 in the circumferential direction becomes a so-called substantial magnetic gap in which the relative permeability μ is extremely close to 1, The magnetic flux Φ ₀ in the detection core unit 2 is reduced to Φ ₁ (Φ ₁ approximation 0).

Here, when the alternating current passing through the exciting coil 5 is set to frequency f ₀ and the exciting core portions 4a and 4b are saturated near the peak value of the current, the exciting core portion is excited twice in one cycle of the exciting current. 4a and 4b will be saturated. Therefore, the magnetic flux [Phi ₀ generated in the detecting core 2 by the DC current I flowing through the lead wire being detected 1 becomes a be modulated with 2f _0, the voltage V _DET of frequency 2f ₀ with the change of the magnetic flux [Phi ₀ Will be generated in the detection coils 3a and 3b. Regardless of the direction of the direct current I flowing through the conductor 1 to be detected, the magnetic flux Φ ₀ ∝ DC current I and voltage V _DET ∝
Due to the relationship with the magnetic flux Φ ₀ , the voltage becomes V _DET ∝ DC current I, and the electromotive force proportional to the DC current I flowing in the conductor 1 to be detected can be detected by the detection coils 3a and 3b.
As described above, the DC current sensor shown in FIG. 9 has a relatively simple structure and has an electromagnetically well-balanced structure, and therefore has an excellent detection ability even for a minute current change. In addition, stable and highly sensitive measurement can be realized.

[0006]

The DC current sensor shown in FIG. 9 has a simple structure and enables high-sensitivity measurement as compared with various kinds of DC current sensors known in the related art, and thus has a wide range of applications. Was achieved. However, for example, when used in a current density measuring device for measuring and adjusting the current density distribution in the plating bath for the purpose of preventing uneven plating of electroplating, further miniaturization without decreasing the sensitivity described above. In particular, it is desired to simplify the shapes of the detection core and the excitation core and simplify the winding configuration of the detection coil and the excitation coil.

Further, in the DC current sensor shown in FIG.
In order to perform magnetic switching, it is necessary to magnetically saturate part or all of the detection core in the circumferential direction, and relatively large electric power is supplied to the exciting coil. Therefore, it cannot be said that this is a preferable configuration for use in a portable device such as a clamp meter.

The present invention has been proposed in view of the above situation, and the core shape made of a soft magnetic material forming a direct current sensor is made as simple as possible, and a winding structure of a detection coil and an excitation coil is also provided. It is an object of the present invention to provide a DC current sensor which can be downsized by simplification and can reduce the power supplied to the exciting coil.

[0009]

As a result of various studies on the structure for achieving the above-mentioned object, the inventor of the present application has found that the core shape can be made simple by changing the magnetic switching method. I found out. That is, the DC current sensor shown in FIG. 9 employs a configuration in which magnetic switching is performed by magnetically saturating a part or all of the detection core in the circumferential direction. By applying a magnetic field, which is orthogonal to the circumferential magnetic field and whose direction changes periodically, to the magnetic field in the circumferential direction of the detection core portion generated by the direct current flowing through the conducting wire, the magnetization direction in the detection core portion is increased. It was confirmed that magnetic switching is possible by rotating and rotating the magnetic flux in the circumferential direction inside the detection core, and as a result, the core of soft magnetic material that constitutes the DC current sensor is cylindrical. We have found that the objective can be achieved by using only the core.

The present invention has been completed based on the above findings, and is made of a cylindrical soft magnetic material and has a plurality of through-holes formed in its side surface at predetermined intervals in the circumferential direction, and An exciting coil wound so that the directions of currents in the through holes adjacent to each other are opposite to each other, and a detection coil wound around the outer circumference of the detection core in a toroidal shape. It is a direct current sensor that does.

Further, as a higher performance direct current sensor, a detection core made of a cylindrical soft magnetic material and having a plurality of through holes formed on its side surface at predetermined intervals in the circumferential direction, and the through hole are provided with each other. An exciting coil wound so that the directions of the currents in adjacent through holes are opposite to each other, a shield case made of a soft magnetic material surrounding a detection core formed by winding the exciting coils, and the shield. A DC current sensor is also proposed, which has a detection coil wound around the outer circumference of the case in a toroidal shape. Further, as a desirable configuration for applications such as a clamp meter, in the above configuration, a DC current sensor is proposed in which the detection core is a configuration that can be divided in the circumferential direction.

In particular, the current density distribution in the plating bath is measured.
When used in a current density measuring device or the like to be adjusted, since the entire DC current sensor is immersed in a plating bath, the surface of the DC current sensor is coated with a corrosion-resistant protective film such as synthetic resin, or synthesized. It is preferable to surround with a resin case.

In the DC current sensor of the present invention, the detection core is not limited to a cylindrical permalloy machined product as shown in the embodiments described later, but the magnetic properties required and the object to be penetrated and arranged in the detection core. It is desirable to select the shape and material in consideration of the number of detection wires and workability. For example, in addition to the cylindrical shape, a configuration such as an elliptic cylinder shape or a rectangular cylinder shape can be adopted. Also, in these configurations,
Not only an integrated product made by cutting out a predetermined material, but also a long ribbon material wound in a spiral shape into a tubular shape, or a plurality of tubular ribbon materials stacked concentrically to form a tubular shape. It is desirable to select the soft magnetic material such as the above-mentioned one in consideration of the shape, size, mechanical characteristics, etc. of the soft magnetic material.

As the material of the detection core, permalloy is usually preferable from the viewpoint of magnetic properties and workability, but other known soft magnetic materials such as silicon steel plate, amorphous, electromagnetic soft iron, and soft ferrite can be used. .

[0015]

The operation of the DC current sensor of the present invention will be described based on an embodiment shown in FIGS. FIG. 1 is a partial cross-sectional plan view of a DC current sensor, FIG. 2 is an enlarged view of a portion thereof, FIG. 3 is an explanatory view of the operating principle, and FIG. 4 is an exciting current applied to an exciting coil and a circumferential direction in a detection core. It is a graph which shows the relationship with the electromotive force (output) of a magnetic flux and a detection coil.

In FIG. 1 and FIG. 2, reference numeral 11 denotes a conductor to be detected which is penetrated and arranged inside a cylindrical detection core 12 which is an integrally formed product obtained by carving out permalloy. A plurality of through holes 13 are formed on the side surface of the detection core 12 at predetermined intervals in the circumferential direction. In this through hole 13, the exciting coil 1 is arranged so that the directions of the currents in the through holes 13 adjacent to each other are opposite to each other.
4 are wound and arranged. In the figure, after the windings are arranged so as to pass through all the through holes 13 clockwise or counterclockwise as a whole so that the insertion directions of the through holes 13 adjacent to each other are opposite, the whole structure is reversed again. One through hole 1 is arranged so that all the through holes 13 are wound around it.
Two exciting coils 14a in which the directions of currents are the same in 3
(Thick solid line in the figure) and 14b (thick broken line in the figure) are arranged. Reference numeral 15 in the drawing denotes a detection coil wound around the outer circumference of the detection core 12 in a toroidal shape.

In such a structure, the lead wire 11 to be detected is
When a direct current I flows through the detection core 1, as shown in FIG.
A clockwise magnetic field H ₀ with respect to the direction of the direct current I (white arrow in the figure) is generated at 2, and a magnetic flux Φ ₀ is generated in the detection core 12. At this time, when a predetermined alternating current is applied to the exciting coil 14, for example, when a current flows in the direction indicated by an arrow i in the drawing, a magnetic field H ₀ generated by the direct current I flowing through the detection lead wire 11 is generated in the detection core 12. A magnetic field H (black arrow in the figure) in a direction orthogonal to that is generated, the magnetization direction in the detection core 12 is rotated based on the combined magnetic field, and the magnetic flux Φ ₀ is modulated. Therefore, the voltage V _DET based on the circumferential magnetic flux component in the detection core 12 is generated in the detection coil 15 according to the change in the magnetic flux Φ ₀ .

Further, such a phenomenon will be described in detail with reference to FIGS. 3 and 4. FIG. 3 schematically shows the directions of magnetic fluxes generated between the through holes 13 formed in the detection core 12 by arrows. The exciting coil 14
Also, the illustration of the detection coil 15 is omitted (however, the detection coil 15 is shown only in FIG. 3A). When a direct current I flows through the conductor 11 to be detected, as shown in FIG. 3A, a clockwise magnetic field with respect to the direction of the direct current I is generated in the detection core 12, and a magnetic flux Φ ₀ is generated in the detection core 12. To do.

At this time, when a predetermined alternating current is passed through the exciting coil 14 to generate a magnetic field in the detection core 12 in a direction orthogonal to the magnetic field generated by the direct current I flowing in the conductor 11 to be detected, these are generated. The magnetization direction in the detection core 12 rotates based on the combined magnetic field of (1), and the directions of the magnetic flux generated between the adjacent through holes 13 are (↑ ↓) in FIG. 3B, (→→) in FIG. 3C, and (↑) in FIG. 3D. ↓) changes as shown. The magnitude of the exciting current is the direct current I flowing through the detected lead wire 11.
The magnitude of the current required to rotate the direction of the magnetization generated in the detection core 12 in the circumferential direction by
It is not necessary to magnetically saturate the entire 2.

That is, when the exciting current to the exciting coil 14 becomes maximum, the direction of the magnetic flux in the detecting core 12 becomes the direction orthogonal to the circumferential direction (shown in FIGS. 3B and 3D),
The circumferential magnetic flux component in the detection core 12 becomes substantially zero. Further, when the exciting current to the exciting coil 14 becomes the minimum, the magnetic field in the direction orthogonal to the magnetic field generated by the direct current I flowing in the conductor 11 to be detected becomes substantially zero. Magnetic flux component in the circumferential direction (Φ
The Θ approximation Φ ₀ ) is also maximum (illustrated in FIGS. 3A and 3C). Therefore, an electromotive force (V _DET ) corresponding to the amount of change of the magnetic flux in the detection core 12 is generated in the detection coil 15.

Here, if the alternating current passing through the exciting coil 14 is set to frequency f ₀ and the magnetic flux component in the circumferential direction in the detection core 12 is substantially zero in the vicinity of the peak value of the current, FIG. As shown in, the magnetic flux component in the circumferential direction in the detection core 12 is substantially zero twice in one cycle of the exciting current (illustrated in FIGS. 4a and 4b). Therefore, the detected lead wire 1
Magnetic flux [Phi ₀ generated in the detecting core 12 by the DC current I flowing through the 1 becomes a be modulated with 2f _0, generating a voltage V _DET is detection coil 15 of the frequency 2f ₀ with the change of the magnetic flux [Phi ₀ (As shown in FIG. 4c). Note that A to D in FIG. 4 show the relationship with FIGS. Regardless of the direction of the direct current I flowing through the conductor 11 to be detected, in any case, the magnetic flux Φ ₀ ∝ DC current I and voltage V _DET
From the relationship with ∝ magnetic flux Φ ₀ , voltage V _DET ∝ DC current I,
The detection coil 15 can detect an electromotive force proportional to the direct current I flowing through the conductor 11 to be detected.

As described above, the DC current sensor of the present invention is different from the DC current sensor shown in FIG. 9 described above in magnetic switching means, but the mechanism for generating electromotive force in the detection coil 15 is different. Substantially the same, high-sensitivity measurement equivalent to or higher than that of the DC current sensor shown in FIG. 9 can be realized, and the structure can be extremely simplified. Further, since the electromotive force generation mechanism for the DC current sensor shown in FIG. 9 and the detection coil 15 are substantially the same, various types of additional DC current sensors shown in FIG. 9 are added for the purpose of improving the characteristics of the DC current sensor. Mechanical and electrical equipment can be attached as well.

In the above description, the two exciting coils 14a (thick solid lines in the figure) and 14b having the same current direction in each through hole 13 formed in the side surface of the detection core 12 are described.
(Thick broken line in the figure) has been described in the configuration, but each through hole 13 is arranged so as to be clockwise or counterclockwise as a whole.
The object of the present invention can be achieved even in a configuration in which only one exciting coil (14a or 14b) is arranged inside. However, from the viewpoint of magnetic efficiency and balance, the illustrated configuration is desirable. Further, in the above description, the detected conductor 11 is arranged inside the detection core 12, but the detected conductor 11 is not arranged, for example, the current density distribution in the plating bath is measured and adjusted. High-sensitivity measurement can be performed even in a configuration in which a change in the amount of charged substances passing inside the detection core 12 is measured, such as a current density measuring device. The same applies to the other embodiment described below.

FIG. 5 is a partially sectional perspective explanatory view showing another embodiment of the direct current sensor of the present invention, and FIG. 6 is a partially enlarged vertical sectional explanatory view. In this DC current sensor, the detection core 12 and the exciting coil 14 arranged in the through hole 13 formed in the side surface of the detection core 12 have the same configuration as that in FIG. After the detection core 12 formed by winding the exciting coils 14 is surrounded by the shield case 16 made of a soft magnetic material, the detection coil 15 is wound around the outer circumference of the shield case 16 in a toroidal shape. Reference numeral 11 in the figure denotes a conductor to be detected. Also in the DC current sensor having such a configuration, high-sensitivity measurement can be realized by the same operating principle as the DC current sensor having the configuration in FIG.

In this structure, the detection core 12 formed by winding the exciting coil 14 is surrounded by the shield case 16 made of a soft magnetic material, so that the leakage magnetic flux from the detecting core 12 and the exciting coil 14 generate the magnetic flux. Since the adverse effect on the detection coil 15 (mixing of the excitation signal and its high frequency, etc.) can be reduced without leaking the generated magnetic flux to the outside of the shield case 16, it is possible to provide a direct current sensor with higher performance than the configuration of FIG. Is possible. In particular, in the illustrated configuration, as shown in FIG. 6, the direction of the magnetic flux generated in the shield case 16 by the excitation coils 14a and 14b is the direction of the magnetic flux generated by the excitation coil 14a as indicated by the solid arrow a. In this case, the directions of the magnetic fluxes generated by the exciting coil 14b are the directions indicated by the broken arrow B, which are opposite to each other, and thus cancel each other out.
This is substantially the same as the state where no magnetic field is applied to the shield case 16. That is, the magnetic flux does not leak to the outside of the shield case 16, and the adverse effect on the detection coil 15 can be reduced.

FIG. 7 is a partial cross-sectional plan view showing a DC current sensor of the present invention having a structure useful as a clamp meter in which the detection core is divided in the circumferential direction. In this configuration, the detection core is composed of a pair of substantially semicircular detection core members 12a and 22.
2a and 22 have a structure in which one end is held by a clamp member 17 so that one end can be opened and closed. In each of the through holes 13 and 23 formed on the side surfaces of the pair of detection core members 12a and 22, two exciting coils 14a (thick solid line in the figure) and 14b (thick line in the figure) having the same current direction are formed. Dashed line) and 24a (thick solid line in the figure), 24b (thick broken line in the figure)
Are arranged in a roll. Further, the detection core member 12a,
Detection coils 15 and 25 are wound around the outer circumference of 22 in a toroidal shape.

In the DC current sensor having such a structure, the pair of detection core members 12 is provided without cutting the lead wire (not shown) to be detected, which has already been wired.
After arranging the conductor to be detected from the open ends of a and 22 inside the detection core, and closing the open end to form an integral cylindrical detection core, the same operating principle as the DC current sensor shown in FIG. By this, it becomes possible to measure the direct current flowing through the conductor to be detected with high sensitivity.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to confirm the operation and effect of the present invention, FIG.
A direct current sensor having the structure shown in was prepared. That is, the outer diameter is 18 mm and the inner diameter is 15 which is a machined and integrated product.
mm x 3 mm height cylindrical permalloy (78% Ni-5
% Mo-4% Cu-bal. Eight through holes each having an outer diameter of 1 mm were provided on the side surface of Fe) at equal intervals in the circumferential direction, and further magnetic annealing was performed at 1100 ° C. for 3 hours in a hydrogen gas atmosphere to form a detection core. A silk winding wire having an outer diameter of 0.3 mm is wound around the detection core as an exciting coil, and
200 formal wire with an outer diameter of 0.1 mm is used as a detection coil.
A direct current sensor of the present invention was obtained by arranging in a turn winding.

An electromotive force of a detection coil when a detection wire made of vinyl coating having an outer diameter of 8 mm is penetratingly arranged inside the detection core and a DC current is applied to the detection wire while increasing or decreasing a direct current within a range of ± 10 mA. (Output) V _DET was measured, and the result is shown in FIG. The exciting coil has a frequency of 200 Hz, 0.
A sinusoidal alternating current of 1 Arms is applied, and the electromotive force (output) V _DET of the detection coil is shown as a value after passing through a bandpass filter of 400 Hz and Q = 10.
From FIG. 8, according to the DC current sensor of the present invention, 10
It can be seen that highly sensitive measurement is possible even with a minute current of about mA.

[0030]

According to the present invention, a magnetic field which is orthogonal to the magnetic field in the circumferential direction and whose direction changes periodically is applied to the magnetic field in the circumferential direction of the detection core portion generated by the direct current flowing through the conductor to be detected. By rotating the magnetization direction in the detection core section by doing so, magnetic flux in the circumferential direction in the detection core section is modulated to implement magnetic switching, thereby adopting a DC current sensor. It has become possible to make a very simple structure in which the core of the soft magnetic material is only a cylindrical core. As a result, it is possible to simplify the winding configuration of the detection coil and excitation coil,
It is possible to realize high-sensitivity measurement and to downsize the direct current sensor itself. Therefore, it can be used for a current density measuring instrument or the like for measuring and adjusting the current density distribution in the plating bath for the purpose of preventing uneven plating of electroplating, and the application of the DC current sensor is further expanded. Further, since the direction of magnetization in the detection core is rotated, the electric power supplied to the exciting coil can be relatively small, which facilitates the use in a portable device such as a clamp meter.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional plan view showing an embodiment of a direct current sensor of the present invention.

FIG. 2 is a partially enlarged explanatory view of the DC current sensor of the present invention shown in FIG.

3A to 3D are explanatory views of the operating principle of the DC current sensor of the present invention.

4A to 4C are graphs showing the relationship between the exciting current applied to the exciting coil of the DC current sensor of the present invention, the circumferential magnetic flux in the detecting core, and the electromotive force (output) of the detecting coil.

FIG. 5 is a partial cross-sectional perspective explanatory view showing another embodiment of the DC current sensor of the present invention.

6 is a partially enlarged vertical cross-sectional explanatory view of the DC current sensor of the present invention shown in FIG.

FIG. 7 is a partial cross-sectional plan view showing another embodiment of the direct current sensor of the present invention.

FIG. 8 is a graph showing measured data based on the DC current sensor of the present invention shown in FIG.

FIG. 9 is a perspective explanatory view of a direct current sensor previously proposed by the inventor.

[Explanation of symbols]

 1, 11 Detected conducting wire 2 Detection core part 3a, 3b Detection coil 4a, 4b Excitation core part 5 Excitation coil 12 Cylindrical detection core 12a, 22 Detection core member 13, 23 Through hole 14, 14a, 14b, 24a, 24b Excitation Coil 15,25 Detection coil 16 Shield case

Claims (3)

[Claims] 1. A detection core made of a cylindrical soft magnetic material, having a plurality of through holes formed on its side surface at predetermined intervals in the circumferential direction, and a current flowing in the through holes adjacent to the through hole. A direct current sensor, comprising: an exciting coil wound in a reverse direction; and a detecting coil wound in a toroidal shape on the outer circumference of the detecting core. 2. A detection core made of a cylindrical soft magnetic material and having a plurality of through holes formed on its side surface at predetermined intervals in the circumferential direction, and a current flowing through the through holes adjacent to the through hole. Exciting coils wound in opposite directions, a shield case made of a soft magnetic material surrounding a detection core formed by winding these exciting coils, and a toroidal coil wound around the outer circumference of the shield case. A direct current sensor having a detection coil arranged. 3. The DC current sensor according to claim 1, wherein the detection core has a structure that can be divided in the circumferential direction.