JP2015225024A - Current sensing structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current sensing structure which enables accurate detection of a magnetic field and thus allows for accurately sensing current flowing through bus bars even when a GMR element is used as a magnetic sensing element.SOLUTION: A current sensing structure comprises a first bus bar 2 through which current flows, a second bus bar 3 through which current flows in the same direction as the current flowing through the first bus bar 2, and a magnetic sensing element 4 located between the first bus bar 2 and the second bus bar 3. The magnetic sensing element 4 is positioned to be able to measure intensity of a magnetic field in a direction that is perpendicular to the direction of the current flowing through the bus bars 2, 3 and is also perpendicular to a direction in which the first bus bar 2 and second bus bar 3 are arrayed.

Description

  The present invention relates to a current detection structure.

  Patent Document 1 is known as a conventional current detection structure for detecting a current flowing through a bus bar.

  In the current detection structure described in Patent Document 1, a ring-shaped magnetic core having a gap portion is disposed so as to surround the bus bar, and a Hall element as a magnetic detection element is disposed in the gap portion. In the current detection structure described in Patent Document 1, the magnetic field generated by the current flowing in the bus bar is collected by the ring-shaped magnetic core, and the collected magnetic field is concentrated on the Hall element arranged in the gap portion. Even if the magnetic field is weak, the magnetic field from the bus bar can be detected with high accuracy, and the current flowing through the bus bar can be detected with high accuracy.

  However, in the current detection structure of Patent Document 1, since it is necessary to arrange a ring-shaped magnetic core on the outer periphery of the bus bar, there is a problem that the current detection structure becomes large.

  Therefore, Patent Document 2 proposes a current detection structure that detects a current flowing through a bus bar without providing a ring-shaped magnetic core.

JP 2010-175276 A JP 2010-19747 A

  However, in the current detection structure of Patent Document 2, although the ring-shaped magnetic core can be omitted and the size can be reduced, the magnetic field generated by the bus bar cannot be concentrated on the magnetic detection element, and therefore the magnetic field cannot be accurately detected. There was a problem that there was.

  Therefore, in order to realize a current detection structure capable of accurately detecting a magnetic field generated in a bus bar while being small, the present inventors have developed a giant magnetoresistive effect element having high detection sensitivity as a magnetic detection element. (Hereinafter referred to as GMR (Giant Magneto Resistive effect) element) was considered.

  However, when a GMR element is used as the magnetic detection element, the problem is that the magnetic field to be detected is too large and the magnetic field cannot be detected with high accuracy.

  Accordingly, an object of the present invention is to solve the above-described problems and to detect a magnetic field with high accuracy even when a GMR element is used as a magnetic detection element, and to accurately detect a current flowing through a bus bar. It is to provide a possible current detection structure.

  The present invention has been devised to achieve the above object, and includes a first bus bar through which current flows, a second bus bar through which current flows in the same direction as the first bus bar, the first bus bar, and the second bus bar. Between the first bus bar and the second bus bar, and the magnetic detection element is in a direction perpendicular to a direction in which the currents of the two bus bars flow. A current detection structure arranged to measure the strength of a magnetic field perpendicular to the direction.

  The magnetic detection element may be a giant magnetoresistance effect element.

  The distance between the first bus bar and the magnetic detection element may be greater than the distance between the second bus bar and the magnetic detection element.

  The first bus bar and the second bus bar may be made of a rectangular plate-like conductor that allows current to flow along the longitudinal direction, and may be arranged in parallel so that the surfaces thereof face each other.

  The magnetic detection element may be disposed on a surface passing through the center in the width direction of the both bus bars.

  According to the present invention, even when a GMR element is used as a magnetic detection element, it is possible to provide a current detection structure that can accurately detect a magnetic field and can accurately detect a current flowing through a bus bar. .

It is a figure which shows the electric current detection structure which concerns on one Embodiment of this invention, (a) is a side view, (b) is the 1B-1B sectional view taken on the line.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  1A and 1B are diagrams showing a current detection structure according to the present embodiment, in which FIG. 1A is a side view and FIG. 1B is a sectional view taken along line 1B-1B.

  As shown in FIGS. 1A and 1B, the current detection structure 1 includes a first bus bar 2 through which current flows, a second bus bar 3 through which current flows in the same direction as the first bus bar 2, and a first bus bar 2. And a magnetic detection element 4 disposed between the first bus bar 3 and the second bus bar 3.

  The bus bars 2 and 3 are rectangular plate-like conductors, and serve as current paths through which current flows along the longitudinal direction thereof. The first bus bar 2 and the second bus bar 3 are formed in the same shape.

  The first bus bar 2 and the second bus bar 3 are arranged in parallel so that the longitudinal directions thereof coincide with each other and the surfaces thereof face each other (so that the normal directions of the surfaces coincide).

  In the present embodiment, it is assumed that the same current flows through the first bus bar 2 and the second bus bar 3. Although the current values flowing through the first bus bar 2 and the second bus bar 3 may be different, the current detection structure 1 detects the intensity of the magnetic field obtained by synthesizing the magnetic fields generated by the two bus bars 2 and 3 in the magnetic detection element 4. Therefore, the relationship between the currents flowing through both bus bars 2 is constant, or the current flowing through one of both bus bars 2 and 3 is known (that is, the current flowing through one of the bus bars 2 and 3 is used as a reference). It is necessary to obtain the other current value). The current flowing through the bus bars 2 and 3 is, for example, about 200 A at the maximum in a steady state, about 800 A at the maximum in an inrush current at the time of abnormality, and the frequency is, for example, about 100 kHz at the maximum.

  The magnetic detection element 4 is configured to output an output signal having a voltage corresponding to the intensity (magnetic flux density) of the magnetic field in the direction along the detection axis D. In the present embodiment, a GMR element having high sensitivity is used as the magnetic detection element 4.

  The magnetic detection element 4 is in a direction perpendicular to the direction in which the currents of both bus bars 2 and 3 flow (the paper surface direction in FIG. 1B), and the arrangement direction of both bus bars 2 and 3 (FIG. 1B). In the direction perpendicular to the vertical direction), that is, along the width direction of the bus bars 2 and 3 (the horizontal direction in FIG. 1B), and along the detection axis D. Arranged to measure the strength of the magnetic field. The detection axis D of the magnetic detection element 4 may be tilted by about −10 ° to 10 ° with respect to the width direction of the bus bars 2 and 3.

  As shown in FIG. 1B, the magnetic detection element 4 detects a combined magnetic field obtained by synthesizing a magnetic field generated by the first bus bar 2 on the upper side of the drawing and a magnetic field generated by the second bus bar 3 on the lower side of the drawing. become. Here, since the currents flowing through both bus bars 2 and 3 are in the same direction, the magnetic fields generated in both bus bars 2 and 3 are opposite to each other at a position between both bus bars 2 and 3 where the magnetic detection element 4 is disposed. Thus, the combined magnetic field is smaller than the magnetic field generated by both bus bars 2 and 3.

  Here, since the magnetic fields generated in both bus bars 2 and 3 are completely opposite to each other are on the plane passing through the center in the width direction of both bus bars 2 and 3, in order to perform detection with higher accuracy. The magnetic detection element 4 is arranged on a surface passing through the center in the width direction of both bus bars 2 and 3 (that is, at least a part of the magnetic detection element 4 overlaps a surface passing through the center in the width direction of both bus bars 2 and 3. It is desirable to arrange the magnetic detection element 4 at a position).

  It is known that the GMR element used as the magnetic detection element 4 has a bias coil inside and stabilizes the output in a state where a magnetic field is always applied in a direction perpendicular to the detection axis D. In this embodiment, the direction of the magnetic field applied by the bias coil is the vertical direction in FIG. 1B, but if a large magnetic field is applied in this direction, the magnetic field applied by the bias coil is canceled and the output is reduced. It may become unstable. In the present embodiment, since the magnetic detection element 4 is disposed on the surface passing through the center in the width direction of both bus bars 2 and 3, the magnetic field generated by the bus bars 2 and 3 may affect the magnetic field of the bias coil. In addition, the output of the GMR element can be stabilized and highly accurate detection can be performed. Further, the magnetic detection element 4 is arranged so that the detection axis D is along the direction perpendicular to the arrangement direction of the both bus bars 2 and 3. This also provides the same effect as described above.

  In this embodiment, since the values of the currents flowing through both bus bars 2 and 3 are the same, the intensity of the combined magnetic field obtained by synthesizing the magnetic fields generated by both bus bars 2 and 3 is at an intermediate position between both bus bars 2 and 3. 0. Therefore, the magnetic detection element 4 needs to be arranged at a position shifted from the intermediate position between the two bus bars 2 and 3. In the present embodiment, the magnetic detection element 4 is arranged at a position where the distance between the first bus bar 2 and the magnetic detection element 4 is larger than the distance between the second bus bar 3 and the magnetic detection element 4.

  Since the strength of the combined magnetic field can be adjusted by the position of the magnetic detection element 4 in the arrangement direction of the both bus bars 2 and 3, the magnetic detection element 4 is detected so that a magnetic field having a strength suitable for the magnetic detection element 4 is detected. It is advisable to adjust the position as appropriate.

  More specifically, the magnetic detection element 4 is desirably arranged at a position where the magnetic flux density of the magnetic field to be detected (the combined magnetic field generated by combining the magnetic fields generated by the bus bars 2 and 3) is greater than 0 and 5 mT or less. This is because in a general GMR element, the output is saturated under a magnetic flux density exceeding 5 mT, and measurement becomes difficult. In addition, the magnitude | size of a magnetic flux density here is in a steady state, and excludes the case where it exceeds 5 mT temporarily at the time of abnormality or a transient state.

  Further, in the GMR element, the region where the magnetic flux density can be detected with high precision (the region where the magnetic flux density and the output voltage can be easily linearly corrected) is usually 2 mT or less, and more preferably, the magnetic flux density (steady state) of the magnetic field to be detected The magnetic detection element 4 may be arranged at a position where the magnetic flux density at (1) is greater than 0 and equal to or less than 2 mT.

  As described above, in the current detection structure 1 according to the present embodiment, the first bus bar 2 through which current flows, the second bus bar 3 through which current flows in the same direction as the first bus bar 2, the first bus bar 2, and the second bus bar 2 And a magnetic detection element 4 disposed between the bus bar 3 and the magnetic detection element 4. The magnetic detection element 4 is perpendicular to the direction in which the currents of the bus bars 2 and 3 flow, and the first bus bar 2 It arrange | positions so that the intensity | strength of the magnetic field of a perpendicular | vertical direction may be measured with respect to the arrangement direction of 2 bus bars 3. FIG.

  With this configuration, the magnetic fields generated by both bus bars 2 and 3 cancel each other, and even when the current flowing through the bus bars 2 and 3 is large, the strength of the magnetic field detected by the magnetic detection element 4 is reduced. It becomes possible to make it smaller. That is, according to the present embodiment, even when a GMR element is used as the magnetic detection element 4, it is possible to detect the magnetic field with high accuracy and to detect the current flowing through the bus bars 2 and 3 with high accuracy. become.

  The present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Current detection structure 2 1st bus bar 3 2nd bus bar 4 Magnetic detection element

Claims (5)

A first bus bar through which current flows;
A second bus bar in which current flows in the same direction as the first bus bar;
A magnetic detection element disposed between the first bus bar and the second bus bar,
The magnetic detection element is configured to measure a magnetic field strength in a direction perpendicular to a direction in which current flows in both bus bars and in a direction perpendicular to an arrangement direction of the first bus bar and the second bus bar. A current detection structure characterized by being arranged. The current detection structure according to claim 1, wherein the magnetic detection element is a giant magnetoresistance effect element. The current detection structure according to claim 1, wherein a distance between the first bus bar and the magnetic detection element is larger than a distance between the second bus bar and the magnetic detection element. The said 1st bus bar and the said 2nd bus bar consist of a rectangular plate-shaped conductor which sends an electric current along a longitudinal direction, and are arrange | positioned in parallel so that the surfaces may oppose. The current detection structure described. The current detection structure according to claim 4, wherein the magnetic detection element is disposed on a surface passing through a center in a width direction of the both bus bars.