JP5937819B2 - Loop core for current sensor and current sensor - Google Patents

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. 6 is a perspective view of a current sensor using the loop core as shown in FIG. As shown in FIG. 6, 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, the influence of an external magnetic field, which is one of disturbances at the time of measurement, in particular, the influence caused by the magnetic flux of the external magnetic field entering the probe P cannot be ignored.

  In order to eliminate the influence of such an external magnetic field, various methods can be considered. One of them is to eliminate the seam in the leg part of the loop core, thereby facilitating the magnetic flux of the external magnetic field to pass through the leg part. There is a method of suppressing the ratio of passing through the probe side. However, since the loop core is usually made 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. 7, the ratio of the magnetic flux of the external magnetic field passing through the probe P increases due to an increase in the magnetic resistance of the joint portion 21g provided on the upper and lower legs, 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 configured by joining a plurality of divided cores divided in the left and right directions on the dividing line formed on the upper and lower legs.
(5) At least one of the upper and lower leg portions of the plurality of split cores is formed in a trapezoidal shape with a narrower width from one end to the other end side, which is a connection side of the leg portion and the yoke portion. The hypotenuses of the divided cores are joined to each other.

  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 joint formed on the leg is formed obliquely along the length of the leg, the magnetic flux of the external magnetic field passes through the length of the leg without being largely blocked by the joint. Become. 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. The perspective view which shows the flow of the magnetic flux of the external magnetic field in embodiment of FIG. The perspective view which shows the assembly method of the current sensor using the loop core of FIG. The top view which shows the assembly method of the split core in embodiment of FIG. 1, and the flow of geomagnetism. 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. 5-7, the same code | symbol is attached | subjected and description is abbreviate | omitted.

1. Configuration of Loop Core FIG. 1 is a perspective view of a loop core according to the present embodiment, in which the central portion of FIG. 1 shows the configuration of the loop core in an assembled state, and the outer peripheral portion of FIG.

  As shown in the assembled state of FIG. 1, the loop core of the present embodiment has endless loop cores on the left and right (in a direction parallel to the yoke portions 31 and 32) along the dividing line C formed on the upper and lower legs. The two divided cores 1a and 1b are joined to each other. In this case, the dividing line C formed on the upper and lower leg portions is formed obliquely with respect to the length direction of the plate-like core material constituting the leg portions.

  Therefore, as shown in the shape of each component in FIG. 1, one divided core 1a includes upper and lower leg portions 21a and 22a having a triangular shape, and the other divided core 1b has upper and lower legs having the same triangular shape. The parts 21b and 22b are provided. The triangular leg portions of the two split cores 1a and 1b have a shape that forms upper and lower leg portions having a rectangular belt shape by combining the two.

  The joint part of the two split cores 1a and 1b, that is, the part of the leg parting line C is joined by means such as pressure welding, adhesion, or welding. In this case, in the present embodiment, the joint portion between the upper leg portions 21a and 21b and the joint portion between the lower leg portions 22a and 22b are in close contact with each other, and there is no gap.

  In other words, in the present embodiment, by providing joints (parting lines C) formed on the upper and lower legs along the length direction of the legs, as shown in FIG. The direction of the junction is substantially the same as that of the dotted line in FIG. 2, and the amount of magnetic flux of the external magnetic field across the junction is reduced. As a result, when viewed as the whole leg portion, the magnetic resistance to the magnetic flux of the external magnetic field decreases, and the amount of magnetic flux of the external magnetic field that passes through the probe can be suppressed.

  In the present embodiment, shield plates S1 and S2 are provided outside the upper and lower leg portions 21a and 21b and the lower leg portions 22a and 22b configured as described above. The shield plates S1 and S2 are disposed in close contact with the surfaces of the upper and lower leg portions, and are integrated with the leg portions.

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 FIG.

  First, two coils to be mounted on the upper and lower legs are manufactured in advance. That is, the winding 9 is wound around the bobbin 8 with the coil mounted on the lower leg. The coil attached to the upper leg portion winds the winding 11 around the bobbin 10 and incorporates the probe P inside the bobbin 10. In this case, the probe P is attached to the bobbin 10 so that there are a space for inserting the upper leg portions 21a and 21b and a space for inserting the intermediate leg portion 5 above and below the probe P.

  The left and right split cores 1a and 1b are assembled from both sides of the two coils thus manufactured. In that case, the upper legs 21 a and 21 b are inserted into the upper gap of the probe P of the upper bobbin 10, and the intermediate leg 5 is inserted into the lower gap of the probe P of the bobbin 10. The lower legs 22a and 22b are inserted inside the lower coil bobbin 8.

  Inside each of the bobbins 8 and 10, the bobbin slides along the triangular leg portions 21 a and 21 b in which the tips of the divided cores 1 a and 1 b are narrowed and the dividing line C in which the leg portions 22 a and 22 b are slanted. As shown in FIG. 4 (b), the triangular leg portions are combined to form a rectangular belt-like leg portion. In this case, since the triangular leg portions 21a, 21b and 22a, 22b are pushed into the bobbins 8, 10 in a wedge shape, the bobbins 8, 10 can be firmly fixed to the leg portions. 21a, 21b and the junction part of 22a, 22b can be stuck closely.

  As shown in FIG. 1, when the shield plates S1 and S2 are provided on the outside of the leg portion, the shield plate is fixed to the outside of the leg portion of one split core in advance, and then the left and right split cores are inserted into the bobbin. To do. Alternatively, the left and right split cores can be inserted into the bobbin after the shield plates S1 and S2 are joined to the inner surface of the bobbin.

3. Effects of the Embodiment As described above, in the present embodiment, by forming the dividing line obliquely with respect to the length direction of the leg portion, the joint portion of the divided core has a shape along the direction in which the magnetic flux of the external magnetic field flows. can do. As a result, the magnetic resistance of the leg portion with respect to the external magnetic field is reduced, so that the amount of magnetic flux of the external magnetic field passing through the probe side is reduced, and the decrease in measurement accuracy due to the external magnetic field can be suppressed.

  In the present embodiment, the triangular leg portions are combined inside the coil bobbin like a wedge while sliding the triangular leg portions, so that the coupling strength of the left and right divided cores is high and the adhesion of the joint portion is also excellent.

  When the shield plates S1 and S2 are provided outside the legs, the magnetic flux of the external magnetic field that flows in the length direction of the legs easily passes through the shield plates S1 and S2. It becomes possible to reduce the amount of magnetic flux.

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

(1) The joint portions of the lower leg portions 22a and 22b are brought into close contact with each other, and a slight gap can be formed in the joint portion of the upper leg portions 21a and 21b. In that case, the magnetic flux of the external magnetic field that runs along the length direction of the leg portion passes through the joint side of the lower leg portions 22a and 22b where there is no gap, and the upper leg portion 21a and 21b side with the gap. Therefore, the amount of magnetic flux of the external magnetic field that passes through the probe P can be suppressed.

(2) Only the joints of the upper legs 21a and 21b or the joints of the lower legs 22a and 22b can be formed by oblique dividing lines. In that case, the oblique junction is closely contacted to reduce the magnetic resistance, and the other parting line has a shape orthogonal to the length direction of the leg as shown in the prior art, and the part is closely contacted or gapd. You may have it.

(3) The loop core can be configured only by the legs without providing the shield plates S1 and S2.

(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 ... Divided core 21,22,21a, 22a, 21b, 22b ... Leg part 31,32 ... Yoke part 4 ... Gap 5 ... Intermediate leg part 6 ... First annular part 7 ... Second Annular parts 8, 10 ... Bobbins 9, 11 ... Windings S1, S2 ... Shield plate P ... Probe

Claims (5)

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,
Loop core for the current sensor is constructed by joining a plurality of divided cores divided into left and right, each of the at least one leg of the upper and lower leg portions of the plurality of divided cores, the legs and the yoke portion A loop core for a current sensor, characterized in that it is formed in a trapezoidal shape with a narrower width from one end to the other end, which is a connecting side, and the oblique sides of each divided core are joined together . The loop core for a current sensor according to claim 1, wherein the hypotenuse is formed on an upper leg portion constituting the second annular portion. The hypotenuse is formed in a lower leg part constituting the first annular part, and a gap exists in a dividing line of the upper leg part constituting the second annular part. The loop core for current sensors according to claim 2. 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: Inside the bobbin, the legs having a hypotenuse formed in the left and right of the split cores are inserted through, characterized in that the inner wall of the bobbin is pressed pressure wedge by the legs of the left and right divided cores The current sensor according to claim 4 .

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