JP2013130447A - Loop core for current sensor and current sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a loop core and a current sensor insusceptible to an influence by an external magnetic field.SOLUTION: A pair of upper and lower leg parts 21, 22 and a pair of right and left yoke parts 31, 32 are formed with an endlessly-formed tabular core material. Each center of the right and left yoke parts is projected in parallel to the leg parts and toward an opposite yoke side to form a U-shape, and a predetermined gap 4 is formed between tips of the U-shape, so that an intermediate leg part 5 is formed. The intermediate leg part, the upper and lower leg parts and the left and right yoke parts integrally form a first annular part 6 for inserting a cable of a measuring object and a second annular part 7 for accommodating a magnetic probe. An endless loop core is formed by a plurality of division cores 1a, 1b divided at division lines C formed at the right and left yoke parts, respectively. The leg parts 21, 22 at each division core are formed with a tabular member having no juncture formed as a pair with regard to the right and left yoke parts.

Description

  The present invention relates to a loop core and a current sensor using the loop core.

  Conventionally, a current sensor for measuring a current flowing through an electric wire to be measured is known. This type of current sensor includes a loop core into which an electric wire to be measured is inserted, a coil wound around the leg of the loop core, and a Hall element or a fluxgate sensor for detecting a magnetic field induced by the current flowing through the electric wire. The magnetic probe in FIG.

  Various types of loop cores have been proposed for use in this current sensor. One of them has, for example, two annular portions as described in Patent Document 1.

  The configuration of this prior art loop core is shown in FIG. In this loop core, a pair of upper and lower leg portions 21 and 22 and a pair of left and right yoke portions 31 and 32 are formed by an endless plate-shaped core material 1. By projecting the center of the left and right yoke portions 31 and 32 in a U shape in parallel to the leg portions 21 and 22 toward the opposing yoke side, and forming a predetermined gap 4 between these U-shaped tips, An intermediate leg 5 is formed between the upper and lower legs.

  The intermediate leg 5, the upper and lower legs 21 and 22, and the left and right yoke parts 31 and 32, the first annular part 6 through which the electric wire to be measured is inserted, and the magnetic field induced by the current flowing through the electric wire A second annular portion 7 for accommodating the magnetic probe P for detection is formed.

  FIG. 8 is a perspective view of a current sensor using the loop core as shown in FIG. As shown in FIG. 8, a first winding 9 is wound around a leg portion 22 below the loop core via a bobbin 8. A second winding 11 is wound around the upper leg 21, the probe P in the second annular portion, and the intermediate leg 5 via a bobbin 10.

  In such a loop core having the first and second annular portions 6 and 7, a magnetic field is generated in the loop core by the current flowing through the electric wire inserted into the first annular portion. By detecting the magnetic flux generated by the generated magnetic field with the probe P arranged in the second annular portion, the magnitude of the current flowing through the electric wire is measured.

Japanese Patent No. 4733244

  By the way, the fluxgate sensor mainly used in this type of loop core has a feature of excellent current detection accuracy. However, it is not possible to ignore the influence of disturbances during measurement, particularly the influence of the magnetic flux of the external magnetic field entering the probe P.

  In order to eliminate the influence of such an external magnetic field, various methods are conceivable. One of them is to eliminate the joint at the leg of the loop core, thereby making it easier for the magnetic flux of the external magnetic field to pass through the leg. There is a method of suppressing the ratio of passing through the probe side. However, since the loop core is usually manufactured by combining a plurality of split cores divided into two at the center, it is difficult to eliminate the joints at the legs.

  In particular, since this type of loop core has the intermediate leg portion 5 having a gap, as shown in Patent Document 1, the split cores are often joined at the upper and lower leg portions 21 and 22. As a result, as shown in FIG. 9, the magnetic resistance of the joint portion 21g provided on the upper and lower legs increases, so that the ratio of the magnetic flux of the external magnetic field passing through the probe P increases, causing measurement errors. .

  The present invention has been proposed to solve the above-described problems of the prior art. That is, according to the present invention, by improving the joint portion of the split core provided in the leg portion, the magnetic resistance of the joint portion becomes smaller than the magnetic resistance of the gap portion, and the magnetic flux of the external magnetic field passes through the probe side. It is an object of the present invention to provide a loop coil with a reduced ratio and a current sensor that can improve detection accuracy by using the loop coil.

The loop coil of the present invention has the following characteristics.
(1) A pair of upper and lower leg portions and a pair of left and right yoke portions are formed by an endless plate-shaped core material.
(2) The upper and lower leg portions are formed by projecting the center of the left and right yoke portions in a U-shape parallel to the leg portions toward the opposing yoke side, and forming a predetermined gap between the U-shaped tips. An intermediate leg is formed between the two.
(3) A first annular portion through which the electric wire to be measured is inserted by the intermediate leg portion, the upper and lower leg portions, and the left and right yoke portions, and a magnetic probe for detecting a magnetic field induced by the current flowing through the electric wire A second annular portion that accommodates is formed.
(4) An endless loop core is formed by joining a plurality of divided cores divided in a direction parallel to the leg portions in a dividing line formed in the left and right yoke portions.
(5) The leg portion of at least one of the split cores is composed of a plate-like member having no joint portion formed in a pair with the left and right yoke portions.

  A loop coil as described above; a magnetic probe disposed in a space surrounded by the second annular portion; and a coil wound around a leg portion of the loop core for the current sensor via a bobbin. A featured current sensor is also an embodiment of the present invention.

  According to the present invention, the following effects are exhibited. Since the leg portion of the split core is composed of a plate-like member formed with a pair of left and right yoke portions and without a joint portion, the magnetic flux of the external magnetic field is not largely blocked by the joint portion, and the length of the leg portion is reduced. It will pass in the direction. As a result, the magnetic flux amount of the external magnetic field passing through the probe from the leg portion is reduced, and the influence of the external magnetic field can be reduced in current measurement, and a current sensor with high measurement accuracy can be obtained.

The disassembled perspective view which shows one Embodiment of the loop core of this invention. It is a perspective view which shows the assembly method of the current sensor using the loop core of FIG. 1, and shows an upper division | segmentation core part. It is a perspective view which shows the assembly method of the current sensor using the loop core of FIG. 1, and shows the division | segmentation core part below. It is a perspective view which shows the assembly method of the current sensor using the loop core of FIG. 1, and shows the state which combines an upper and lower division | segmentation core. The perspective view which shows the flow of the magnetic flux of the external magnetic field in embodiment of FIG. Sectional drawing which shows the modification of the junction part of an up-and-down division | segmentation core. The perspective view of the conventional loop core. The perspective view of the current sensor using the conventional loop core. Sectional drawing explaining the influence of the external magnetic field in the conventional loop core.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, about the part same as the prior art shown in FIGS. 7-9, the same code | symbol is attached | subjected and description is abbreviate | omitted.

1. Configuration of Loop Core As shown in the assembled state of FIG. 1, the loop core according to the present embodiment is configured such that endless loop cores are parallel to the upper and lower legs 21 and 22 in the dividing line C formed on the left and right yoke portions. The two divided cores 1a and 1b divided into two are joined. In this case, the dividing line C formed in the left and right yoke portions is formed at right angles to the length direction of the plate-like core material constituting the yoke portion.

  As shown in the shape of each part in FIG. 1, the upper divided core 1 a includes upper yoke portions 31 a and 32 a formed continuously from the end of the upper leg portion 21 to the lower portion of the intermediate leg portion 5. ing. The lower split core 1b includes lower yoke portions 31b and 32b that are formed continuously from the end of the lower leg portion 22. The upper and lower yoke portions 31a and 32a and the lower yoke portions 31b and 32b are joined at the parting line portion, thereby forming left and right yoke portions having a rectangular band shape.

  The joint portions of the two divided cores 1a and 1b, that is, the joint portions of the upper yoke portions 31a and 32a and the lower yoke portions 31b and 32b are joined by means such as pressure welding, adhesion, and welding. As a means for this joining, as shown in FIG. 6 (a), the end portions of both yoke portions are abutted, and as shown in FIGS. 6 (b) and 6 (c), a structure such as meshing or overlapping is used. Can be adopted. In the present embodiment, the joint portions of the upper yoke portions 31a and 32a and the lower yoke portions 31b and 32b are in close contact with each other, and no gap is present. However, a gap may be provided at the joint portions.

  On the other hand, in the present embodiment, the upper and lower leg portions 21 and 22 of the split cores 1a and 1b are configured by plate-like members having no joint portion formed integrally with the left and right yoke portions 31 and 32, respectively. As a result, as shown in FIG. 5, when viewed as the whole leg portion, the magnetic resistance to the external magnetic field is reduced, and the amount of magnetic flux of the external magnetic field passing through the probe can be suppressed.

2. Assembly of Current Sensor An example of a method for assembling a current sensor using the loop core of the present embodiment having the above-described configuration will be described with reference to FIGS.

  As shown in FIG. 2, the probe P is inserted into the annular portion 7 provided in the upper divided core 1a, and the bobbin 10 is attached to the divided core 1a so as to surround the upper leg portion 21 and the intermediate leg portion 5. Installing. In this state, the winding 11 is wound around the outer periphery of the bobbin 10. On the other hand, as shown in FIG. 3, the bobbin 8 is attached to the outer periphery of the leg portion 22 of the lower split core 1b, and the winding 9 is wound around the periphery. Note that this operation may be performed first, or may be performed simultaneously at another location.

  Thereafter, as shown in FIG. 4, the upper divided core 1a and the lower divided core 1b on which the coil is mounted are joined by abutting the end surfaces of the upper yoke portions 31a and 32a and the lower yoke portions 31b and 32b. A current sensor having a coil and a probe attached to the loop core is obtained.

3. Advantages of the Embodiment As described above, in this embodiment, the split portion is formed outside the winding and the joint portion is not provided inside the winding. Therefore, the magnetic resistance of the leg portion is reduced to reduce the probe side. The amount of magnetic flux of the external magnetic field passing through can be reduced, and the decrease in measurement accuracy due to the external magnetic field can be reduced.

  In this embodiment, since the loop core is divided by the dividing line provided in the yoke portion, the bobbin can be attached to the leg portion and the winding can be wound with the upper and lower divided cores separated from each other. . As a result, when the winding is wound, the other divided cores do not get in the way and workability is improved. Further, since the split cores 1a and 1b are joined at the yoke portion where no winding is present, the work of joining the split cores is easy.

4). Other Embodiments The present invention is not limited to the above-described embodiments, and includes other embodiments as described below.

(1) In the illustrated embodiment, the dividing line has a shape perpendicular to the length direction of the yoke portion. However, the dividing line is formed obliquely with respect to the length direction of the yoke portion, or the concave and convex portions are engaged. It can also be.

(2) Although the magnetic resistance is low without providing a gap in the joint portion provided in the yoke portion, the geomagnetism passing through the lower leg portion by providing the gap passes through the yoke portion and the intermediate leg portion 5 and the probe P. It is also possible to prevent sneaking to the side.

(3) In the illustrated embodiment, both the upper and lower legs are configured without a joint, but only one of the legs may be configured without a joint. In that case, the amount of magnetic flux of the external magnetic field passing through the probe P is provided by providing a joint having a gap in the upper leg close to the probe and guiding the magnetic flux of the external magnetic field to the lower leg without the joint. Can be suppressed.

(4) The present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

DESCRIPTION OF SYMBOLS 1 ... Core material 1a, 1b ... Division | segmentation core 21,22 ... Leg part 31,32,31a, 32a, 31b, 32b ... Yoke part 4 ... Gap 5 ... Intermediate leg part 6 ... 1st cyclic | annular part 7 ... 2nd Annular part 8, 10 ... Bobbin 9, 11 ... Winding P ... Probe

Claims (4)

A pair of upper and lower leg portions and a pair of left and right yoke portions are formed by an endless plate-shaped core material,
By projecting the center of the left and right yoke parts into U-shapes parallel to the leg parts toward the opposing yoke side, and forming a predetermined gap between the U-shaped tips, the space between the upper and lower leg parts Intermediate legs are formed on the
The intermediate leg portion, the upper and lower leg portions, and the left and right yoke portions accommodate a first annular portion through which the electric wire to be measured is inserted and a magnetic probe for detecting a magnetic field induced by the current flowing through the electric wire. A loop core for a current sensor in which a second annular portion is formed,
The current sensor loop core is formed by joining a plurality of divided cores divided in a direction parallel to the leg portions in a dividing line formed in the left and right yoke portions,
The leg core of at least one of the split cores is composed of a plate-like member having no joint part formed in a pair with the left and right yoke parts.   The loop core for a current sensor according to claim 1, wherein the leg portions of both the upper and lower divided cores are formed of a plate-like member having a joint portion formed in a pair with the left and right yoke portions.   The loop core for a current sensor according to claim 1, wherein a gap exists in an upper leg portion forming the second annular portion on which the probe is mounted. A loop core for a current sensor according to any one of claims 1 to 3,
A magnetic probe disposed in a space surrounded by the second annular portion;
A coil wound around a leg of the loop core for the current sensor via a bobbin;
A current sensor comprising:

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