JPH08262063A - Direct current sensor - Google Patents

Abstract

PURPOSE: To provide a highly sensitive direct current sensor which can detect a small current of approx. several mA at a high accuracy by innovating the structure of a shield case to reduce the generation of an incorrect output due to effect of an external magnetic field. CONSTITUTION: A conductor 1 to be detected is arranged in a core part 20 piercing it. Then, a primary shield case 30 is provided to warp the core part 20, a secondary shield case 40 to wrap the primary shield case 30, a specified gap 60 is formed between the primary shield case 30 and the secondary shield case 40 and moreover, a tertiary shield case 50 comprising a copper plate is stuck inside the secondary shield case 40. With such an arrangement, effect by an external magnetic field can be reduced significantly and even when a magnetic field (magnetic flux) to be detected is very small as compared with an external magnetic field, a small current of approx. several mA can be detected at a high accuracy. The tertiary shield case 50 allows the prevention of malfunctioning as caused by a pulse-like noise such as surge current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is provided in equipment using various DC currents, as well as ground fault detectors in DC control panels of power plants and substations, leak detectors in drive circuits of electric vehicles, and the like. With respect to the improvement of the DC current sensor, the generation of error output due to the influence of the external magnetic field is reduced by devising the configuration of the shield case, and the high sensitivity that can detect a minute current of about several mA with high accuracy is achieved. DC current sensor

[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,
Not only can these DC current sensors not only have a complicated structure, but also cannot be said to be structures that can respond to the minute current changes required for DC leakage detectors, etc., and have not yet been put into practical use as highly sensitive DC current sensors. The current situation.

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. Various direct current sensors having a structure completely different from the method have been proposed (EP 0 579 462).
A, JP-A-6-74978, JP-A-6-19438
No. 9, Japanese Patent Application No. 5-215074, Japanese Patent Application No. 5-2340
70).

In these proposals, an exciting core made of an annular soft magnetic material that is cross-connected to the circumferential direction of the detecting core is integrally arranged in a part of the detecting core made of an annular soft magnetic material. With respect to the circumferential magnetic flux generated in the detection core by the direct current flowing through the detected conductor penetrating the inside of the detection core, a magnetic flux in a direction perpendicular to the magnetic flux is generated at the intersection of the detection core and the excitation core. Generate
This is a method of detecting a direct current flowing through a conductor to be detected by periodically modulating a magnetic flux in the circumferential direction generated in the detection core.

Based on the above basic structure, electromagnetic imbalance is further reduced to reduce noise generation and S / N.
FIG. 14, FIG. 15, FIG.
17 and 18 in which the detection core can be divided as a configuration that enables easy installation and placement without cutting the DC current sensor shown in FIG. 6 or a wire (detection wire) that has already been wired. The DC current sensor shown is also proposed.

In the direct current sensor shown in FIG. 14, a pair of cylindrical bodies made of a soft magnetic material are formed in parallel with each other with a predetermined gap through which the lead wire 1 to be detected is arranged and whose axial center lines are parallel to each other. And the exciting core portions 4a and 4b, and the open end adjoining portions of the pair of cylindrical bodies are connected and integrated by a soft magnetic material, and the detection core portion is formed by the connecting portion and the pair of cylindrical inner side surfaces. It has a configuration having two. 3 in the figure
Reference numerals a and 3b denote a pair of detection coils, which are arranged in a toroidal manner at circumferentially opposed positions of the detection core portion (in the figure, connecting portions for connecting and integrating the opening end adjacent portions of the tubular body). There is. Reference numeral 5 in the drawing denotes an exciting coil, which is wound around the outer circumference of the detection core portion 2 so that the exciting core portions 4a and 4b can be excited in a direction perpendicular to the circumferential direction 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 in 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 periodically magnetically saturated, the detection core unit 2
The core crossing portion 6 which is a part in the circumferential direction of the above becomes a so-called substantial magnetic gap in which the relative permeability μ is extremely close to ₁ , and reduces the magnetic flux Φ ₀ in the detection core portion 2 to Φ ₁ .

Here, if 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 is detected coil frequency 2f ₀ with changes in the magnetic flux It occurs in 3a and 3b.
Regardless of the direction of the direct current I flowing through the detected lead wire 1,
In any case, magnetic flux Φ ₀ ∝ DC current I, voltage V _DET
The voltage V _DET ∝ DC current I due to the relationship with ∝ magnetic flux Φ _0, and the electromotive force proportional to the DC current I flowing in the lead wire 1 to be detected can be detected by the detection coils 3a and 3b. The absolute value of the direct current I flowing through the conductor 1 can be known.

The DC current sensor shown in FIGS. 15, 16, 17, and 18 also detects the DC current I flowing through the conductor 1 to be detected by the same operating principle as the DC current sensor shown in FIG. 14 described above. be able to. The DC current sensor shown in FIG. 15 has a pair of exciting coils 5a and 5b arranged therein, and has a structure in which the pair of exciting cores 4a and 4b are wound around the outer surface portions, and the other structure is the same as in FIG.
This is the same as the DC current sensor shown in FIG. In the DC current sensor shown in FIG. 16, the pair of exciting coils 5a and 5b are wound around the exciting coil winding bars 7a and 7b formed in the inner central portions of the pair of exciting core portions 4a and 4b.
A pair of detection coils 3a and 3b are wound around the magnetic cores 4a and 4b in a toroidal shape.
In particular, the magnetic flux generated in the exciting coils 5a and 5b has an effect of efficiently acting without leaking to the outside of the exciting core portions 4a and 4b.

The DC current sensor shown in FIG. 17 is shown in FIG.
The detection coil unit 2 of the DC current sensor shown in FIG. 2 is separable, and the detection core unit 2 is provided with excitation core units 4a and 4b.
The detecting core members 2a and 2b are divided by the connecting portions of the detecting core members 2a and 2b, and the abutting portions 8a and 8b of the detecting core members 2a and 2b are formed in an L shape, and the detected conductor 1 is arranged at a predetermined position. After that, the screw 9 is integrated. In this configuration, the pair of detection coils 3a and 3b
Since (only 3a is shown in the figure) is wound around the connecting portion of the excitation core portions 4a and 4b, it is independently wound near the abutting portions 8a and 8b of the detection core members 2a and 2b. Detection coils 3a-1, 3a-2 and 3b-
1, 3b-2 (only 3a-1 and 3a-2 are shown in the figure).

The DC current sensor shown in FIG. 18 is shown in FIG.
The detection core unit 2 of the DC current sensor shown in FIG. 16 is separable, and is the same as the DC current sensor shown in FIG. 16 except for the configuration of the detection core unit 2.

In addition to the above, various configurations are proposed in accordance with the location of the detection coil 3 and the excitation coil 5, the location of division of the detection core section 2, the configuration of the abutting section, and the like. These DC current sensors have made it possible to detect minute currents of a few mA with high accuracy, but depending on the application, they may be affected by external magnetic fields generated from electrical equipment and the like that are placed close to the DC current sensor. Since the arrangement may be easy, it is necessary to reduce the generation of error output due to the influence of the external magnetic field in order to effectively utilize the inherent advantages. For example, permalloy as shown in FIG. A configuration in which it is surrounded by a shield case 10 made of a soft magnetic material such as a non-oriented silicon steel plate is adopted. That is, the rectangular frame-shaped case main bodies 10a and 10b are arranged on the outer circumference and the inner circumference of the direct current sensor (the direct current sensor shown in the figure corresponds to the direct current sensor shown in FIG. 14), and then the upper and lower case lids 10c. , 10d is used.

[0013]

It is possible to prevent the external magnetic field from being mixed into the detection core constituting the DC current sensor to some extent by surrounding the detection core portion with the above-mentioned shield case or the like. When the detection current flowing through the detection lead wire is a minute current of about several mA, the magnetic field generated by the detection current flowing through the detection lead wire is about 1/1000 to 1/2000 of the earth's magnetism, and the effect of the external magnetic field is substantial. Need to be zero.

FIG. 20 is a schematic explanatory view for explaining a mechanism of generating an error output due to an external magnetic field. That is,
This diagram corresponds to the configuration of the DC current sensor shown in FIG. 14, and is a schematic explanatory diagram in which the exciting coil 5 is omitted in particular. When a direct current I flows through the conductor 1 to be detected, a magnetic flux Φ ₀ in a predetermined circumferential direction is generated in the detection core portion 2. At this time,
As described above, the electromotive forces Va and Vb are generated in the pair of detection coils 3a and 3b wound around the detection core portion 2 in the circumferentially opposed positions based on the generation of the magnetic flux Φ ₀ . The pair of detection coils 3a and 3b are connected to these electromotive forces Va and Vb.
Are connected so that they are combined, and finally the combined output voltage V
It is output as _DET (V _DET = Va + Vb).

On the other hand, when a magnetic flux Φ _{n in the} same direction as the magnetic flux Φ ₀ (horizontal direction in the figure) is generated in the detection core portion 2 by the external magnetic field, the pair of detection coils 3 is operated by the same action as described above.
Electromotive forces Va 'and Vb' are generated in a and 3b, respectively. Normally, since the magnetic fluxes Φ _n passing through the detection coils 3a and 3b have the same direction, the electromotive forces Va ′ and Vb ′ are canceled by each other, and finally the output (Va ′) due to the external magnetic field is generated.
-Vb '= 0) becomes zero and is not output.

However, in practical use, the electromotive force Va generated in each of the detection coils 3a and 3b due to the external magnetic field is caused by variations in the assembly accuracy of the members constituting the DC current sensor and the operating conditions of the external magnetic field. In many cases, the difference between 'and Vb' does not become completely zero, and in particular, when the magnetic field (magnetic flux) to be detected is much smaller than the external magnetic field (magnetic flux), it is based on the DC current I flowing through the conductor 1 to be detected. Electromotive force V due to external magnetic field with respect to output voltage V _DET
The value of the error output due to the difference between a ′ and Vb ′ is about the same or more, and even if the shield case as shown in FIG. 19 is arranged, the minute current flowing in the detected conductor 1 to be detected is highly accurately measured. It becomes impossible to detect.

The present invention is proposed for the purpose of solving such a problem, and in particular, by devising the configuration of the shield case, the occurrence of error output due to the influence of an external magnetic field is reduced, It is an object of the present invention to provide a highly sensitive direct current sensor capable of detecting a minute current of about mA with high accuracy.

[0018]

In order to achieve the above-mentioned object, the present invention has variously studied the structure of the shield case, and as a result, a shield case made of a soft magnetic material is formed with a magnetic gap. The inventors have completed the invention by discovering that the object can be achieved by using the two-layer structure.

That is, according to the present invention, an exciting core portion is formed by forming a pair of cylindrical bodies made of a soft magnetic material with a predetermined gap through which the conductor to be detected is arranged and having their axial center lines parallel to each other. And connecting the opening end adjacent portions of the pair of cylindrical bodies with a soft magnetic material so as to be integrated, and the detecting core portion formed by the connecting portion and the pair of cylindrical inner surface portions of the tubular body, and the exciting core portion. An exciting coil wound so as to be able to be excited in a direction perpendicular to the circumferential direction of the detection core portion, and at least a pair of detection coils wound in a toroidal shape at opposite positions in the circumferential direction of the detection core portion. In a direct current sensor in which these outer peripheral portions are surrounded by a shield case made of a soft magnetic material, the shield case has a two-layer structure, and is provided between an inner primary shield case and an outer secondary shield case. To A DC current sensor, characterized in that the formation of the gas-air gaps.

In addition, in the above construction, a direct current sensor characterized in that the detection core portion is dividable is also proposed. In any construction, a primary shield case made of a soft magnetic material is also proposed. Between the secondary shield case and the inside of the primary shield case, and at least one of the outside of the secondary shield case. We propose a characteristic direct current sensor.

In the present invention, as the soft magnetic material forming the exciting core portion and the detecting core portion, permalloy,
Known soft magnetic materials such as silicon steel sheet, amorphous, electromagnetic soft iron, and soft ferrite can be used alone or in combination, and it is desirable to select them in consideration of required magnetic properties and workability.

Further, as the soft magnetic material forming the primary shield case and the secondary shield case, permalloy, non-oriented silicon steel plate, etc. are effective, and these shield cases do not contact each other and have a predetermined gap. It is necessary to form and arrange. In particular, it is also effective to form a magnetic gap by interposing a non-magnetic material such as synthetic resin between the shield cases. The size of the magnetic gap formed in this manner is selected in consideration of the required shield effect, size of the shield case, etc., but about 2 mm to 10 mm is effective. In addition, the thickness of each of the primary shield case and the secondary shield case is also selected in consideration of the shield effect, workability, etc.
0.2 mm to 1 mm is effective, and it is desirable that the shield cases have the same thickness or the secondary shield case has a larger thickness.

Further, as the non-magnetic and good conductive material for forming the third shield case, conductive characteristics, workability,
From the point of view of cost, it is effective to use copper or aluminum having a thickness of about 0.1 mm to 10 mm. This third shield case is placed for the purpose of preventing malfunction due to pulse noise such as surge current, but it is placed between the above-mentioned primary shield case and secondary shield case because it is non-magnetic. Therefore, it also has a role of forming a part of the magnetic gap.

In the direct current sensor of the present invention, the overall configuration of the direct current sensor is electromagnetically balanced with the at least one pair of detection coils wound in a toroidal shape at opposite positions in the circumferential direction of the detection core portion. Since it is configured to be symmetric with respect to the conductor to be detected in consideration, even when a plurality of pairs of detection coils are wound around a plurality of positions in the circumferential direction of the detection core portion, they are electromagnetically balanced with each other. It shows a configuration in which the windings are arranged at opposite positions so as to be symmetrical with respect to the conductor to be detected so as to maintain it.

[0025]

The operation of the DC current sensor of the present invention will be described in detail with reference to an embodiment shown in FIGS. 1 is a vertical cross-sectional explanatory view showing an outline of the entire DC current sensor, and FIG. 2 is a front partial cross-sectional explanatory view of FIG. FIG. 3 is an exploded perspective view showing components of the primary shield case,
FIG. 4 is a perspective explanatory view showing an outline of the entire primary shield case, and FIG. 5 is a perspective explanatory view showing an outline of the entire secondary shield case having a configuration in which a tertiary shield case is arranged inside. .

The direct current sensor of the present invention shown in FIGS. 1 and 2 has a structure for detecting a differential current of a balanced current (reciprocating current). Two core wires 20 to be detected 1a and 1b are to be detected. Are arranged through. The same shielding effect can be obtained with any of the configurations shown in FIGS. 14 to 18 as the configuration of the core portion 20. 30 in the figure
Is a primary shield case that surrounds the core portion 20,
Reference numeral 40 is a secondary shield case that surrounds the primary shield case 30, and reference numeral 50 is a tertiary shield case attached inside the secondary shield case 40. Incidentally, 60 is a space formed between the primary shield case 30 and the secondary shield case 40.

As shown in FIGS. 3 and 4, the primary shield case 30 has a body 31 which is formed by bending a permalloy plate into a U-shaped cross section, and has a permalloy plate press-punched at both ends of the main body 31 to penetrate a detected conductor wire. The end surface portions 33a and 33b having the notches 32 forming the window portion are formed by a pair of box portions 30a and 30b that are integrated by spot welding so that a magnetic gap is not formed at the joint portion.

That is, when an external magnetic field is generated in a direction parallel to the axis center line of the exciting core portion (direction of arrow a in the figure), the shield case 30 is electrically operated in a direction perpendicular to the axis center line of the exciting core portion. When a gap is formed, this gap portion becomes a magnetic resistance and a leakage magnetic flux is generated in the direction of the axis center line of the exciting core portion, and an electromotive force due to the leakage magnetic flux is generated in the detection coil, which easily causes an error output. As described above, the main body 3
1 and the end surface portions 33a and 33b are integrated by spot welding so as not to form a magnetic gap.

As shown in FIG. 5, the secondary shield case 40 has the same structure as the primary shield case 30, in which both ends of the main body 41 formed by bending a permalloy plate into a U-shaped cross section.
An end face portion 43 having a notch portion 42 forming a window portion for penetrating a detected conductor obtained by punching out a permalloy plate.
The a and 43b are integrated by spot welding so that a magnetic gap is not formed at the joint.

Further, the secondary shield case 40 may have a structure in which the entire primary shield case 30 is surrounded by a pair of box portions as in the case of the primary shield case 30.
Even if the one end is open as shown in the figure, the pair of box parts 30 constituting the primary shield case 30.
The object of the present invention can be achieved as long as the structure prevents the invasion of external magnetic flux from the contact portions of a and 30b. In addition,
The secondary shield case 40 shown in FIG. 5 has a structure in which a third shield case 50 made of a copper plate is attached to the inner side of the second shield case 40. However, a clad in which a permalloy plate having a predetermined thickness and a copper plate have been pressure-welded in advance. It can be easily made by subjecting the plate to the above-mentioned processing.

As described above, in the DC current sensor of the present invention, the primary shield case 30 and the secondary shield case 40 are formed by using a permalloy plate having good workability, and these shield cases 30, 40 are formed. The core portion 20 is surrounded by a so-called two-layer structure shield case in which a predetermined magnetic gap 60 is formed.
By setting the effect of the external magnetic field (magnetic flux) acting on to substantially zero, even if the magnetic field (magnetic flux) to be detected is much smaller than the external magnetic field (magnetic flux), the occurrence of error output is reduced, A minute current of about several mA can be detected with high accuracy. Further, by arranging the third shield case 50 made of a copper plate or the like, it is possible to prevent malfunction due to pulse noise such as surge current, and further improve accuracy.

6 to 13 are longitudinal sectional explanatory views showing various embodiments of the shield case constituting the DC current sensor of the present invention. In addition, the illustration of the core portion 20 arranged in these shield cases is omitted. Figure 6
4 has the same configuration as the shield case shown in FIGS. 4 and 5, and one of the third shield case 50 is attached to the inside of the primary shield case 30 including a pair of boxes 30a and 30b. It is a structure surrounded by a secondary shield case 40 having an open end.

The configuration of FIG. 7 has a third shield case 50.
Is not provided, and the primary shield case 30 including the pair of box portions 30a and 30b is surrounded by the secondary shield case 40 having one open end. The configuration of FIG. 8 is
The primary shield case 30 including the pair of box portions 30a and 30b is surrounded by the secondary shield case 40 including the pair of box portions 40a and 40b.
The contact portions of 0a and 30b and the contact portions of the box portions 40a and 40b are not arranged at the same position, and the external magnetic flux is prevented from entering the primary shield case 30.

9 to 12 show the third shield case 5
In addition to the configuration of being attached to the inner side surface of the secondary shield case 40 shown in FIG. 6, the outer side surface (FIG. 9) of the primary shield case 30 and the secondary shield case 40 of FIG. Outer side (Fig. 10), primary shield case 3
No. 0 (FIG. 11), or in the gap between the primary shield case 30 and the secondary shield case 40 (FIG. 12), etc., the pulse of surge current or the like can be obtained similarly to the configuration shown in FIG. It is possible to prevent a malfunction due to the characteristic noise. Further, a configuration in which they are arranged on the inner side surface and outer side surface of the primary shield case 30 and on the inner side surface and outer side surface of the secondary shield case 40 is possible, but in consideration of the required electrical characteristics and workability. Therefore, it is desirable to select the arrangement form of the third shield case 50.

In the structure shown in FIG. 13, the cylindrical fourth shield case 70 is provided not only on the outer peripheral side of the core portion 20 (not shown) but also on the inner peripheral side of the core portion 20 through which the conductor to be detected is arranged. The fourth shield case 7 is shown in FIG.
With the arrangement of 0, the effect of improving the balanced current (round-trip current) characteristic can be obtained. In any of the configurations described above, a predetermined magnetic gap 6 is provided so that the primary shield case 30 and the secondary shield case 40 do not come into contact with each other.
It is necessary to form 0, and by using the shield case having these configurations, the influence of the external magnetic field can be made substantially zero, and a minute current of about several mA can be detected with high accuracy. became.

[0036]

【Example】

Example 1 As the direct current sensor of the present invention, the direct current sensor shown in FIGS. 1 and 2 was prepared. In addition, the core portion 20,
Primary shield case 30, secondary shield case 40
Both are 78Ni-3.5Cu-4.5Mo-Fe (ba
11) A permalloy plate was used for processing, and then a predetermined heat treatment was performed to obtain the desired soft magnetic characteristics. As the core portion 20, a permalloy plate having a thickness of 0.3 mm is used, and the detection core portion 2 shown in FIG. The overall dimensions were width (dimension in the axial center line direction of the excitation core portion was (W ₀ ) 20 mm x length (L ₀ ) 10 mm x height (H ₀ ) 20 mm.

The primary shield case 30 has a thickness of 0.
A 35 mm permalloy plate was used and the structure shown in FIG. 4 was adopted. The overall dimensions are width (W ₁ ) 35 mm ×
The length (L ₁ ) was 15 mm and the height (H ₁ ) was 30 mm.
As the secondary shield case 40, a permalloy plate having a thickness of 0.6 mm was used, and a copper plate having a thickness of 0.1 mm was attached to the inner side of the structure shown in FIG. The overall dimensions were width (W ₂ ) 45 mm × length (L ₂ ) 40 mm × height (H ₂ ) 40 mm. Primary shield case 30
The secondary shield case 40 and the secondary shield case 40 are not in contact with each other so as to form a gap of about 2 mm to 10 mm in the lengthwise direction and form a gap of about 5 mm to 10 mm in the widthwise direction. Placed and fixed in.

The sensitivity of the DC current sensor of the present invention produced in this way was set so that the through current to the conductor to be detected was 2 mA.
When the output voltage is adjusted to be 2V, the error output is 0.5V when a magnet driver having a magnetic flux density of 500 G (Gauss) at the tip is brought to a position about 10 mm from the core portion 20. I confirmed that it occurred. Furthermore, when the above-mentioned secondary shield case 40 is not used, when the same experiment is performed when neither the primary shield case 30 nor the secondary shield case 40 is used, the error output is about 2.5V, It was confirmed that about 5 V was generated.

[0039]

As is apparent from the above embodiments, in the DC current sensor of the present invention, by using the two-layer structure shield case composed of the primary shield case and the secondary shield case, The influence of the external magnetic field can be significantly reduced, and as a result, even if the magnetic field (magnetic flux) to be detected is much smaller than the external magnetic field (magnetic flux), a minute current of about several mA is detected with high accuracy. It has become possible. Further, by arranging the third shield case made of a copper plate or the like at a predetermined position, it is possible to prevent malfunction due to pulse noise such as surge current and further improve accuracy.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional explanatory view showing an overview of the entire DC current sensor that is an embodiment of the present invention.

2 is a front partial cross-sectional explanatory view of FIG. 1. FIG.

FIG. 3 is an exploded perspective view showing components of the primary shield case.

FIG. 4 is a perspective explanatory view showing an overview of the entire primary shield case.

FIG. 5 is a perspective explanatory view showing an overall outline of a secondary shield case having a configuration in which a third shield case is arranged inside.

FIG. 6 is a vertical cross-sectional explanatory view showing one embodiment of a shield case which constitutes the DC current sensor of the present invention.

FIG. 7 is a vertical cross-sectional explanatory view showing one embodiment of a shield case which constitutes the DC current sensor of the present invention.

FIG. 8 is a vertical cross-sectional explanatory view showing one embodiment of a shield case which constitutes the DC current sensor of the present invention.

FIG. 9 is a vertical cross-sectional explanatory view showing one embodiment of a shield case which constitutes the DC current sensor of the present invention.

FIG. 10 is a vertical cross-sectional explanatory view showing one embodiment of a shield case which constitutes the DC current sensor of the present invention.

FIG. 11 is an explanatory longitudinal sectional view showing an embodiment of a shield case that constitutes the DC current sensor of the present invention.

FIG. 12 is an explanatory longitudinal sectional view showing an embodiment of a shield case which constitutes the DC current sensor of the present invention.

FIG. 13 is a vertical cross-sectional explanatory view showing one embodiment of a shield case which constitutes the DC current sensor of the present invention.

FIG. 14 is a perspective explanatory view showing an example of the configuration of the core portion of the previously proposed DC current sensor.

FIG. 15 is a perspective explanatory view showing an example of the configuration of the core portion of the previously proposed DC current sensor.

FIG. 16 is a perspective explanatory view showing an example of the configuration of the core part of the previously proposed DC current sensor.

FIG. 17 is a perspective explanatory view showing an example of the configuration of the core part of the previously proposed DC current sensor.

FIG. 18 is a perspective explanatory view showing an example of the configuration of the core portion of the previously proposed DC current sensor.

FIG. 19 is an exploded perspective view showing a DC current sensor in which the shield case proposed previously is arranged.

FIG. 20 is a cross-sectional explanatory view of a vertical portion for explaining the influence of an external magnetic field (magnetic flux) on the core portion that constitutes the DC current sensor.

[Explanation of symbols]

 1, 1a, 1b Detected conducting wire 2 Detection core part 2a, 2b Detection core member 3a, 3b, 3a-1, 3a-2, Detection coil 4a, 4b Excitation core part 5 Excitation coil 6 Core crossing part 7a, 7b Excitation coil Winding bars 8a, 8b Attaching portion 9 Screw 10 Shield case 10a, 10b Case body portion 10c, 10d Case lid portion 20 Core portion 30 Primary shield case 30a, 30b Box portion 31 Main body portion 32 Cutout portion 33a, 33b End face part 40 Second shield case 40a, 40b Box part 41 Body part 42 Notch part 43a, 43b End face part 50 Third shield case 60 Void part 70 Fourth shield case

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Shigeru Yamaguchi 2-19-1 Minami Suita, Suita City, Osaka Prefecture Sumitomo Special Metals Co., Ltd. Suita Works (72) Inventor Masahiro Suzuki 4-8 Shibaura, Minato-ku, Tokyo No.33 KANDENKO Co., Ltd.

Claims (3)

[Claims] 1. An exciting core portion formed by arranging a pair of cylindrical bodies made of a soft magnetic material to form a predetermined space through which a conductor to be detected is arranged and having their axial center lines parallel to each other.
Each of the pair of cylindrical bodies is connected to the opening end adjacent portion by a soft magnetic material so as to be integrated, and the detection core portion formed by the connection portion and the pair of cylindrical body inner surface portions and the excitation core portion are connected to the detection core. An exciting coil wound so as to be able to be excited in a direction perpendicular to the circumferential direction of the portion, and at least a pair of detecting coils wound in a toroidal manner at opposing positions in the circumferential direction of the detecting core portion. In a DC current sensor in which the outer peripheral part of the is surrounded by a shield case made of a soft magnetic material, the shield case has a two-layer structure, and a magnetic field is provided between an inner primary shield case and an outer secondary shield case. DC current sensor characterized by the formation of a general void. 2. The direct current sensor according to claim 1, wherein the detection core portion has a dividable structure. 3. A non-magnetic material is provided at least at one place between the primary shield case and the secondary shield case made of a soft magnetic material, inside the primary shield case, and outside the secondary shield case. The DC current sensor according to claim 1 or 2, further comprising a third shield case made of a conductive material.