JP2015148470A - current detection structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide current detection structure which can use a highly sensitive magnetic detection element even when a large current flows in a bus bar, and can detect a current with high accuracy as a result.SOLUTION: The current detection structure is provided which includes a bus bar 2 and a magnetic detection element 3 for measuring the intensity of a magnetic field generated by a current flowing in the bus bar 2. In the current detection structure, a part of the bus bar 2 is formed in a concave shape in a cross section view and also formed in a symmetrical shape relative to a width-direction center thereof, and the magnetic detection element 3 is disposed in a space 10 enclosed by the concave-shaped bus bar 2 and also disposed at a width-direction center of the bus bar 2.

Description

  The present invention relates to a current detection structure.

  2. Description of the Related Art Conventionally, when detecting a current flowing through a bus bar, the intensity of a magnetic field generated by a current to be detected is detected by a magnetic detection element. By detecting the strength of the magnetic field by the magnetic detection element, the current flowing through the bus bar can be obtained by calculation based on the strength of the magnetic field.

  As magnetic detection elements, MR (Magneto Resistance) sensors and GMR (Giant Magneto Resistive effect) sensors are known.

  As prior art document information related to the invention of this application, there are Patent Documents 1 and 2.

Japanese Patent No. 5153481 JP 2013-170878 A

  By the way, in order to perform highly accurate measurement, it is desired to use a magnetic detection element such as a GMR sensor with higher sensitivity.

  However, when a large current flows through the bus bar, for example, when detecting a current flowing through each phase of a three-phase motor, the strength of the magnetic field formed by the current flowing through the bus bar is too high, and thus a highly sensitive GMR sensor. It was difficult to use a magnetic detection element such as.

  Accordingly, an object of the present invention is to solve the above-described problems and provide a current detection structure that can use a highly sensitive magnetic detection element even when a large current flows through a bus bar and can perform measurement with high accuracy.

  The present invention was devised to achieve the above object, and is a current detection structure comprising a bus bar and a magnetic detection element for measuring the strength of a magnetic field generated by a current flowing through the bus bar. A part of the bus bar is formed in a concave shape in a cross-sectional view and is formed in a symmetrical shape with respect to the center in the width direction, and the magnetic detection element is in a space surrounded by the bus bar formed in a concave shape. The current detection structure is arranged at the center in the width direction of the bus bar.

  The magnetic detection element may be arranged such that its detection axis is along the width direction of the bus bar.

  The magnetic detection element may be a GMR sensor.

  The magnetic detection element may be arranged at a position where the magnetic flux density of the magnetic field to be detected is greater than 0 and 5 mT or less.

  The magnetic detection element may be arranged at a position where a magnetic flux density of a magnetic field to be detected is greater than 0 and equal to or less than 2 mT.

  The concave portion, which is a concave portion of the bus bar, may be formed in a trapezoidal shape, a triangular shape, or an arc shape in which the side wall gradually expands toward the opening in a cross-sectional view.

  The concave portion, which is a portion formed in the concave shape of the bus bar, may be formed by drawing at a central portion in the width direction of the bus bar.

  The concave portion, which is a concave portion of the bus bar, may be formed by bending both side portions of the bus bar in the width direction.

  According to the present invention, a highly sensitive magnetic detection element can be used even when a large current flows through the bus bar, and a current detection structure capable of measuring with high accuracy can be provided.

It is a figure which shows the electric current detection structure which concerns on one Embodiment of this invention, (a) is a perspective view, (b) is the 1B-1B sectional view taken on the line. It is a figure which shows the electric current detection structure which concerns on one modification of this invention, (a) is a perspective view, (b) is the 2B-2B sectional view taken on the line. (A)-(c) is a cross-sectional view of the electric current detection structure which concerns on one modification of this invention.

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

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

  As shown in FIGS. 1A and 1B, the current detection structure 1 includes a bus bar 2 that flows current along the longitudinal direction, and a magnetic detection element 3 that measures the strength of a magnetic field generated by the current flowing through the bus bar 2. And. The current detection structure 1 detects, for example, a current flowing through a bus bar 2 provided in an automobile inverter.

  The bus bar 2 is a plate-like conductor and serves as a current path through which a current flows. The current flowing through the bus bar 2 is, for example, about 200 A at the maximum in a steady state, about 800 A at the inrush current at the time of abnormality, and the frequency is, for example, about 100 kHz at maximum.

  The magnetic detection element 3 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 sensor having high sensitivity is used as the magnetic detection element 3.

  Now, in the current detection structure 1 according to the present embodiment, a part of the bus bar 2 is formed in a concave shape in a cross-sectional view and is formed in a symmetrical shape with respect to the center in the width direction. Hereinafter, the concave portion of the bus bar 2 is referred to as a concave portion 4.

  In the present embodiment, the recess 4 is formed at the center in the width direction of the bus bar 2. The recess 4 is formed by drawing.

  The concave portion 4 is formed in a U-shape that is rotated 90 degrees counterclockwise in a cross-sectional view. The recess 4 is formed so as to protrude outward in the thickness direction (upward in the drawing) from the surface of the bus bar 2, and is formed in a hollow rectangular parallelepiped shape that opens to the back side of the bus bar 2. Hereinafter, the two wall surfaces in the longitudinal direction of the recess 4 are the front wall 5 and the rear wall 6, the two wall surfaces in the width direction are the right wall 7 and the left wall 8, and the wall surface in the thickness direction, that is, the wall surface serving as the bottom of the recess 4 This is called wall 9.

  The magnetic detection element 3 is disposed in the space 10 surrounded by the bus bar 2 formed in a concave shape, and is disposed at the center in the width direction (X-axis direction) of the bus bar 2. The arrangement of the magnetic detection element 3 in the space 10 means that at least a part of the magnetic detection element 3 is accommodated in the space 10.

  Further, the magnetic detection element 3 is arranged such that the detection axis D is along the width direction (X-axis direction) of the bus bar 2. The detection axis D of the magnetic detection element 3 may be tilted by about −10 ° to 10 ° with respect to the width direction (X-axis direction) of the bus bar 2.

  As shown in FIG. 1B, in the current detection structure 1, the current flowing through the bus bar 2 is from the right wall 7 (and the bus bar 2 on the outer side in the width direction than the right wall 7), the left wall 8 (and the left wall 8). Also flows separately into the bus bar 2) on the outer side in the width direction and the upper wall 9.

  In the present embodiment, since the bus bar 2 is formed symmetrically with respect to the center in the width direction in the portion where the recess 4 is formed, the right wall 7 (and the outer side in the width direction than the right wall 7) in the space 10. The magnetic field (B1 in the figure) generated by the current flowing through the bus bar 2) and the magnetic field (B2 in the figure) generated by the current flowing through the left wall 8 (and the bus bar 2 on the outer side in the width direction from the left wall 8) cancel each other. The intensity of the magnetic field becomes zero at the center of the bus bar 2. For this reason, the magnetic detection element 3 is disposed at the center in the width direction of the bus bar 2 (the center of the magnetic detection element 3 in the width direction of the bus bar 2 is disposed at a position overlapping the center in the width direction of the bus bar 2). It is possible to prevent the magnetic detection element 3 from detecting a magnetic field generated on the left and right of 10 (both sides in the width direction).

  As a result, the magnetic detection element 3 detects only the magnetic field (B3 in the drawing) generated by the current flowing through the upper wall 9. Since the current flowing through the upper wall 9 is a part of the current flowing through the bus bar 2, the magnetic field detected by the magnetic detection element 3 can be reduced even when the current flowing through the bus bar 2 is large.

  The magnitude of the magnetic field detected by the magnetic detection element 3 flows to the upper wall 9 by changing the width of the upper wall 9 (the ratio of the height of the right wall 7 / left wall 8 to the width of the upper wall 9) or the cross-sectional area. Adjustment is possible by adjusting the ratio of the current or by adjusting the distance from the upper wall 9 of the magnetic detection element 3. That is, in the current detection structure 1, it is possible to adjust the intensity of the magnetic field detected by the magnetic detection element 3 to an optimum intensity according to the sensitivity of the magnetic detection element 3.

  When a GMR sensor is used as the magnetic detection element 3, the magnetic detection element 3 is arranged at a position where the magnetic flux density of the magnetic field to be detected (the magnetic field generated by combining the magnetic fields generated by the three bus bars 2) is greater than 0 and less than 5 mT. It is desirable. This is because, in a general GMR sensor, the output is saturated under a magnetic flux density exceeding 5 mT, making measurement 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.

  In addition, in the GMR sensor, the region in which the magnetic flux density can be detected with high accuracy (the region in which the magnetic flux density and the output voltage can be easily linearly corrected) is usually 2 mT or less. It is desirable to dispose the magnetic detection element 3 at a position where the magnetic flux density at (1) is greater than 0 and 2 mT or less.

  In the vicinity of the longitudinal end of the recess 4, the magnetic field generated by the current flowing through the front wall 5 and the rear wall 6 causes an error, so that it is not affected by the magnetic field generated at the front wall 5 or the rear wall 6. It is desirable to arrange the magnetic detection element 3 at a position away from the longitudinal end of the concave portion 4, and it is preferable to arrange the magnetic detection element 3 at the central portion of the concave portion 4 in the longitudinal direction of the bus bar 2. The length of the recess 4 is determined so that the magnetic detection element 3 can be disposed at a position not affected by the magnetic field generated on the front wall 5 and the rear wall 6 in consideration of the magnitude of the current flowing through the bus bar 2 and the like. Good.

  Moreover, it is preferable that the thickness of the upper wall 9 be a thickness that can suppress the influence of the skin effect in consideration of the frequency of the current flowing through the bus bar 2. When copper or a copper alloy is used as the bus bar 2, the skin thickness at a frequency of 100 kHz is about 0.2 mm. Therefore, the thickness of the upper wall 9 is preferably 0.5 mm or less, more preferably 0.2 mm or less. . The skin thickness at a frequency of 10 kHz is about 1 mm. In this case, the thickness of the upper wall 9 is desirably 2 mm or less, more preferably 1 mm or less.

  In the present embodiment, the recess 4 is formed by drawing in the central portion of the bus bar 2 in the width direction. However, the present invention is not limited to this, and the width direction of the bus bar 2 is not limited to this, as shown in FIGS. You may make it form the recessed part 4 by bending the both sides. In this case, the entire bus bar 2 becomes the recess 4. 2A and 2B show, as an example, a case where both sides in the width direction are bent in the entire longitudinal direction of the bus bar 2, but both sides in the width direction are bent only in a part in the longitudinal direction of the bus bar 2. It doesn't matter if you do. As shown in FIGS. 2 (a) and 2 (b), when the recesses 4 are formed by bending both sides in the width direction of the bus bar 2, the recesses 4 can be formed relatively easily as compared with the drawing process. There is an advantage that the cost can be reduced.

  Further, in the present embodiment, the recess 4 is formed in a U-shape that is rotated 90 degrees substantially counterclockwise in a cross-sectional view, but the shape of the recess 4 is not limited to this, and for example, FIG. As shown to a), the recessed part 4 is good also as trapezoid shape from which a side wall (the right wall 7 and the left wall 8) expands gradually toward an opening by cross sectional view. Further, as shown in FIG. 3 (b), the recess 4 may be triangular in a cross-sectional view, or as shown in FIG. 3 (c), the recess 4 is arc-shaped (semi-arc) in a cross-sectional view. You may form in.

  Since the recess 4 is shaped so that the side walls (the right wall 7 and the left wall 8) gradually expand toward the opening in a cross-sectional view, the surfaces of the magnetic detection element 3 and the bus bar 2 are close to each other. It is possible to suppress the frequency dependency and suppress the frequency.

  As described above, in the current detection structure 1 according to the present embodiment, a part of the bus bar 2 is formed in a concave shape in a cross-sectional view and is formed in a symmetrical shape with respect to the center in the width direction. The detection element 3 is disposed in the space 10 surrounded by the bus bar 2 formed in a concave shape, and is disposed at the center of the bus bar 2 in the width direction.

  With this configuration, only the strength of the magnetic field generated by the current flowing through the upper wall 9 of the recess 4 can be detected by the magnetic detection element 3, and even when a large current flows through the bus bar 2. The magnetic field detected by the magnetic detection element 3 can be reduced. That is, according to the current detection structure 1, even when a large current flows through the bus bar 2, it is possible to use the magnetic detection element 3 such as a highly sensitive GMR sensor, and it is possible to perform highly accurate measurement.

  Further, in the current detection structure 1, since the magnetic detection element 3 is disposed in the space 10 in the recess 4, the magnetic detection element 3 is covered with the bus bar 2, and the bus bar 2 serves as a shield. The influence of external noise on the element 3 is suppressed, and detection with higher accuracy becomes possible.

  In addition, a GMR sensor is known which has a bias coil inside and stabilizes 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 Y-axis direction. However, if a large magnetic field is applied in the Y-axis direction, the magnetic field applied by the bias coil is canceled and the output becomes unstable. There is a case. In the present embodiment, the magnetic field generated in the Y-axis direction, that is, the magnetic field generated by the current flowing through the right wall 7 (and the bus bar 2 on the outer side in the width direction than the right wall 7), and the left wall 8 (and the width beyond the left wall 8). Since the magnetic field generated by the current flowing in the bus bar 2) outside the direction cancels each other, the magnetic field of the bias coil is not affected, and the output of the GMR sensor can be stabilized and highly accurate detection can be performed.

  Further, in the current detection structure 1, since the magnetic detection element 3 is disposed in the space 10 in the recess 4, the detection unit (the portion where the magnetic detection element 3 is disposed) can be reduced in size.

  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 Bus bar 3 Magnetic detection element 4 Recessed part 5 Front wall 6 Rear wall 7 Right wall 8 Left wall 9 Upper wall 10 Space

Claims (8)

A current detection structure comprising a bus bar and a magnetic detection element for measuring the strength of a magnetic field generated by a current flowing through the bus bar,
A part of the bus bar is formed in a concave shape in a cross-sectional view and is formed in a symmetrical shape with respect to the center in the width direction,
The magnetic detection element is arranged in a space surrounded by the bus bar formed in a concave shape, and is arranged in the center in the width direction of the bus bar. The current detection structure according to claim 1, wherein the magnetic detection element is disposed such that a detection axis thereof is along a width direction of the bus bar. The current detection structure according to claim 1, wherein the magnetic detection element is a GMR sensor. The current detection structure according to claim 3, wherein the magnetic detection element is disposed at a position where a magnetic flux density of a magnetic field to be detected is greater than 0 and equal to or less than 5 mT. The current detection structure according to claim 3, wherein the magnetic detection element is disposed at a position where a magnetic flux density of a magnetic field to be detected is greater than 0 and equal to or less than 2 mT. The concave portion, which is a concave portion of the bus bar, is formed in a trapezoidal shape, a triangular shape, or an arc shape in which a side wall gradually expands toward an opening in a cross-sectional view. Current detection structure. The current detection structure according to any one of claims 1 to 6, wherein a concave portion that is a concave portion of the bus bar is formed by drawing at a center portion in a width direction of the bus bar. The current detection structure according to any one of claims 1 to 6, wherein a concave portion that is a concave portion of the bus bar is formed by bending both side portions in the width direction of the bus bar.

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