JP2014106100A - Current sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current sensor capable of improving the freedom of arrangement of a magnetic sensing element by arbitrary adjustment of a magnetic flux density distribution in a core diameter direction at a gap of a magnetic core.SOLUTION: A current sensor 1 comprises: a substantially annular magnetic core 3 having a gap 4; and a magnetic sensing element 5 placed in the gap 4 and detecting a magnetic field generated in the gap 4 by an electric current flowing in an electric conductor 2 to convert it into voltage signals. An inner periphery 3a and an outer periphery 3b of the magnetic core 3 form a long circular shape except the gap 4. The magnetic core 3 has an extension part 3e that makes a distance La from a center position G of a conductor-through-hole 7 of a substrate 6 to the gap 4 longer than a distance Lb from the center position G of the conductor-through-hole 7 to a part on the opposite side of the gap 4 with the conductor-through-hole 7 in the magnetic core 3 sandwiched between them. The magnetic sensing element 5 is disposed in a position corresponding to a center part in a width W direction at an end face facing the gap 4 of the magnetic core 3.

Description

  The present invention relates to a current sensor that detects a current flowing through a conductor.

  As a conventional current sensor, for example, as described in Patent Document 1, a magnetosensitive element is disposed in a gap provided in an annular magnetic core, and a current flowing in a conductor penetrating the annular magnetic core causes a gap in the gap. A device that detects a current flowing through a conductor by converting a magnetic field generated in the circuit into a voltage by a magnetosensitive element and outputting the voltage is known.

JP 2011-220983 A

  The current sensor as in the above prior art is used in an electric device such as an inverter. And it is desired that the current sensor be miniaturized as the electric equipment is miniaturized. In order to reduce the size of the current sensor, it is necessary to make the annular magnetic core small. However, if the annular magnetic core becomes small, there arises a problem that magnetic saturation is likely to occur. One of the countermeasures is to increase the magnetic resistance of the magnetic path by widening the gap interval of the annular magnetic core. When the gap interval becomes wide, the magnetic resistance of the magnetic path increases, and the magnetic flux density in the gap generated by the current to be measured decreases. However, if the gap between the annular magnetic cores is excessively widened, the magnetic flux density distribution in the radial direction (core radial direction) of the annular magnetic core in the gap is biased due to the leakage magnetic flux generated near the gap. Such a deviation in the magnetic flux density distribution becomes more prominent as the gap interval becomes wider, and restricts the arrangement of the magnetosensitive elements. In addition, an accurate current sensor can be obtained by arranging the magnetosensitive element at a position where the magnetic flux density reaches a peak in the gap portion of the annular magnetic core. However, in a general annular annular magnetic core, The peak of the magnetic flux density approaches the inside of the core radial direction. For this reason, if it is going to arrange | position a magnetosensitive element in the position where a magnetic flux density becomes a peak, there exists a possibility that a magnetosensitive element may interfere with the through-hole etc. which were provided in the electric current bus or the board | substrate.

  An object of the present invention is to provide a current sensor that can improve the degree of freedom of arrangement of magnetosensitive elements by arbitrarily adjusting the magnetic flux density distribution in the core radial direction in the gap portion of the magnetic core.

  The present invention provides a current sensor that detects a current flowing through a conductor, is provided so as to surround a conductor passing region through which the conductor passes, and is disposed in a substantially annular magnetic core having a gap portion, and in the gap portion. A magnetic sensing element that detects a generated magnetic field and converts it into an electric signal, and the inner periphery of the magnetic core has an oval shape excluding the gap, and the magnetic core is the center of the conductor passage region. It has an extending part that makes the distance from the position to the gap part longer than the distance from the center position of the conductor passage region to the part on the opposite side of the gap part in the magnetic core. In addition, the oval shape here includes not only a part that is linear, but also an elliptical shape that is entirely curved.

  As described above, in the current sensor of the present invention, the inner peripheral shape of the magnetic core is an oval shape excluding the gap portion, and the distance from the center position of the conductor passage region to the gap portion is set to the magnetic core. By providing an extending portion that is longer than the distance from the center position of the magnetic core to the opposite side of the gap portion in the magnetic core, the magnetic path passing through the magnetic core is close to the outside in the core radial direction (in the conductor passage region) in the vicinity of the gap portion. Shift to the opposite side). For this reason, the magnetic flux density distribution in the core radial direction in the gap portion changes, and the peak of the magnetic flux density distribution moves to the outside in the core radial direction. Thus, the magnetic flux density distribution in the core radial direction in the gap portion can be arbitrarily adjusted. At this time, the arrangement position of the magnetosensitive element may be appropriately determined according to the magnetic flux density distribution in the core radial direction in the gap portion. For example, an accurate current sensor can be obtained by placing a magnetosensitive element near the peak of the magnetic flux density distribution in the core radial direction in the gap portion. Conventionally, however, the magnetic flux density distribution in the core radial direction in the gap portion Therefore, when the magnetic sensitive element is arranged near the peak of the magnetic flux density distribution, the magnetic sensitive element may interfere with the conductor and the through hole of the substrate which is the conductor passage area. However, in the current sensor of the present invention, the peak of the magnetic flux density distribution is moved outward in the core radial direction, so that the magnetic sensitive element does not interfere with the conductor or the through hole of the substrate that is the conductor passage region, and the accuracy is improved. A good current sensor can be obtained.

  Preferably, the outer periphery of the magnetic core has an oval shape corresponding to the inner periphery of the magnetic core except for the gap portion. In this case, the width of the magnetic core (the length in the radial direction) becomes the same overall. Therefore, it becomes easy to produce a magnetic core by, for example, press punching. Moreover, it is not necessary to make the magnetic core larger than necessary.

  Preferably, the extending portion has such a length that the peak of the magnetic flux density distribution in the radial direction of the magnetic core in the gap portion corresponds to the central portion in the width direction of the end surface of the magnetic core facing the gap portion. doing. In this case, adjustment of the arrangement position of the magnetosensitive element is further facilitated. For example, an accurate current sensor can be obtained by disposing the magnetosensitive element at a position corresponding to the central portion in the width direction of the end face of the magnetic core in the gap portion.

  Further preferably, the extending portion is formed between a first portion including the end face of the magnetic core facing the gap portion and a semicircular second portion provided on the opposite side of the gap portion in the magnetic core. Has been. In this case, the peak of the magnetic flux density distribution in the radial direction of the magnetic core in the gap can be arbitrarily adjusted without increasing the size of the entire magnetic core.

  According to the present invention, by freely adjusting the magnetic flux density distribution in the core radial direction in the gap portion of the magnetic core, the degree of freedom of arrangement of the magnetosensitive elements can be improved. As a result, for example, when the peak of the magnetic flux density distribution in the gap portion of the magnetic core is shifted to the center portion of the gap portion, the detection sensitivity of the current sensor can be obtained by arranging a magnetosensitive element in the center portion of the gap portion. It is possible to reduce the variation of.

It is a top view which shows 1st Embodiment of the current sensor which concerns on this invention. It is a top view which shows one of the conventional current sensors as a comparative example. It is a graph which shows magnetic flux density distribution in the gap part of the magnetic body core shown in FIG.1 and FIG.2. It is a top view which shows 2nd Embodiment of the current sensor which concerns on this invention. It is a top view which shows 3rd Embodiment of the current sensor which concerns on this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of a current sensor according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a plan view showing a first embodiment of a current sensor according to the present invention. In the figure, a current sensor 1 according to the present embodiment is used in an inverter mounted on a vehicle such as an electric vehicle or a hybrid vehicle, and detects a current flowing through a conductor 2.

  The current sensor 1 includes a substantially annular magnetic core 3. A gap portion 4 is provided in the magnetic core 3. The magnetic core 3 is made of, for example, iron or an iron alloy (such as an electromagnetic steel plate). The magnetic core 3 is produced by, for example, press punching.

  Further, the current sensor 1 includes a magnetosensitive element 5 disposed in the gap portion 4 of the magnetic core 3. The magnetosensitive element 5 detects a magnetic field (magnetic flux density) generated in the gap portion 4 by the current flowing through the conductor 2, converts the magnetic field into a voltage signal proportional to the value of the current flowing through the conductor 2, and outputs the voltage signal.

  The magnetic core 3 and the magnetosensitive element 5 are fixed to the substrate 6. The substrate 6 is provided with a circular conductor through hole (conductor passage region) 7 through which the conductor 2 passes. The magnetic core 3 is bonded to the substrate 6 or is screwed via a bracket in a state of being disposed so as to surround the conductor through hole 7.

  The magnetic core 3 itself has an oval shape except for the gap portion 4. That is, the inner periphery 3 a and the outer periphery 3 b of the magnetic core 3 are both oval except for the gap portion 4. For this reason, the width | variety (diameter direction length) of the magnetic body core 3 is equal over the perimeter. Moreover, the thickness of the magnetic core 3 is generally the same.

  The magnetic core 3 includes a first portion 3c including a magnetic pole portion J facing the gap portion 4, a semicircular second portion 3d provided on the opposite side of the gap portion 4 across the conductor through hole 7, It has the extending | stretching part 3e provided between the 1st part 3c and the 2nd part 3d.

  In the magnetic core 3, the distance La from the center position G of the conductor through-hole 7 of the substrate 6 to the gap portion 4 is from the center position G of the conductor through-hole 7 to sandwich the conductor through-hole 7 in the magnetic core 3. It is being fixed to the board | substrate 6 so that it may become longer than the distance Lb to the part on the opposite side. Therefore, the extending portion 3 e extends from the position corresponding to the center position G of the conductor through hole 7 toward the gap portion 4.

  The magnetosensitive element 5 is mounted on the substrate 6 so as to be disposed at a position corresponding to the central portion in the width W direction on the end surface facing the gap portion 4 of the magnetic core 3.

  In such a current sensor 1, when a current flows through the conductor 2, a magnetic field (magnetic flux) is generated in the magnetic core 3 to form a magnetic path. At this time, the strength of the magnetic field generated in the gap portion 4 is reduced. The current value flowing through the conductor 2 is detected by being detected by the magnetosensitive element 5 and converted into a voltage signal.

  Here, as a comparative example, one conventional current sensor is shown in FIG. In the current sensor 50 shown in the figure, the shape of the magnetic core 3 itself is a perfect circle except for the gap portion 4. The magnetic core 3 is fixed to the substrate 6 so that the center position coincides with the conductor through hole 7. The magnetosensitive element 5 is disposed in an inner region in the core radial direction of the gap portion 4 of the magnetic core 3.

  In such a current sensor 50, the magnetic flux generated in the magnetic core 3 is likely to pass through the inner region of the magnetic core 3 having a small magnetic resistance. For this reason, the magnetic flux density distribution in the core radial direction in the gap portion 4 of the magnetic core 3 is such that the peak of the magnetic flux density exists in the inner region of the magnetic core 3 as indicated by the broken line Q in FIG. Can be obtained. That is, the magnetic flux density distribution in the core radial direction in the gap portion 4 is uneven.

  Incidentally, the amount of change in the magnetic flux density is small near the peak of the magnetic flux density. For this reason, it is preferable to arrange the magnetosensitive element 5 near the peak of the magnetic flux density. Therefore, in the current sensor 50, the magnetosensitive element 5 is arranged in the inner region in the core radial direction in the gap portion 4 of the magnetic core 3.

  However, the inner region of the gap portion 4 in the core radial direction is close to the conductor through hole 7 of the substrate 6 and has a layout restriction. For this reason, since the arrangement position of the magnetosensitive element 5 tends to vary, there is a possibility that the detection sensitivity varies for each current sensor 1.

  In contrast, in the present embodiment, as described above, the shape of the magnetic core 3 itself is an oval shape except for the gap portion 4, and from the center position G of the conductor through hole 7 of the substrate 6 to the gap portion 4. The distance La is longer than the distance Lb from the center position G of the conductor through hole 7 to the portion on the opposite side of the gap portion 4 in the magnetic core 3. For this reason, the magnetic flux generated in the magnetic core 3 is pulled outward in the core radial direction at the magnetic pole portion J of the magnetic core 3. Therefore, as compared with the current sensor 50 shown in FIG. 2, the shape of the magnetic path in the magnetic core 3 changes so as to shift outward in the core radial direction at the magnetic pole portion J. As a result, the magnetic flux density distribution in the core radial direction in the gap portion 4 of the magnetic core 3 is the center in the width W direction on the end surface facing the gap portion 4 of the magnetic core 3 as shown by the solid line P in FIG. A distribution in which the peak of the magnetic flux density exists at the position corresponding to the portion, that is, the central portion in the core radial direction of the gap portion 4 is obtained.

  In the present embodiment, the magnetosensitive element 5 is arranged near the peak of the magnetic flux density in the gap portion 4, that is, in the core radial direction center portion of the gap portion 4. Thereby, the magnetic sensitive element 5 can be arrange | positioned, without receiving the restrictions on a layout especially. Therefore, since the variation in the arrangement position of the magnetosensitive element 5 is suppressed, the variation in detection sensitivity for each current sensor 1 can be sufficiently reduced.

  In addition, since the extending portion 3e that makes the magnetic core 3 oval is provided between the first portion 3c and the second portion 3d, the core in the gap portion 4 can be formed without increasing the size of the entire magnetic core 3. The peak of the magnetic flux density distribution in the radial direction can be easily set at the central portion of the gap portion 4 in the core radial direction.

  Moreover, in this embodiment, since the substantially annular magnetic core 3 is used, the leakage magnetic flux can be reduced and the detection sensitivity of the current sensor 1 can be improved as compared with the rectangular magnetic core. Further, since there is no corner on the inner periphery 3a of the magnetic core 3, the shape of the magnetic path in the magnetic core 3 does not change abruptly, and magnetic saturation of the magnetic core 3 is difficult to occur. Therefore, the current sensor 1 can be downsized or the current detection range can be expanded.

  FIG. 4 is a plan view showing a second embodiment of the current sensor according to the present invention. In the figure, the same or equivalent elements as those in the first embodiment described above are denoted by the same reference numerals, and the description thereof is omitted.

  In the figure, the current sensor 1 of this embodiment includes a substantially annular magnetic core 3 having a gap portion 4. The magnetic core 3 includes a non-semicircular part 3f as a first part including an end face facing the gap part 4 and a semicircular first part provided on the opposite side of the gap part 4 with the conductor through hole 7 interposed therebetween. 2 part 3d and the extending | stretching part 3e provided between the non-semicircle-shaped part 3f and the 2nd part 3d.

  The width Wa of the end face of the non-semicircular part 3f facing the gap part 4 in the magnetic core 3 is a second part 3d that is the part on the opposite side of the gap part 4 across the conductor through hole 7 in the magnetic core 3. It is larger than the width Wb. Specifically, in the magnetic core 3, the width of the magnetic core 3 is opposed to the gap portion 4 in the non-semicircular portion 3 f on the gap portion 4 side from the position corresponding to the center position G of the conductor through hole 7. It has a shape that gradually increases toward the end surface. That is, the extending part 3g extending to the outer side in the core radial direction (opposite side of the conductor through hole 7) is provided on the end face of the non-semicircular part 3f facing the gap part 4. The inner circumference 3a of the magnetic core 3 has an oval shape except for the gap portion 4 as in the first embodiment.

  Further, in the same manner as in the first embodiment, the magnetic core 3 has a distance La from the center position G of the conductor through hole 7 of the substrate 6 to the gap portion 4 from the center position G of the conductor through hole 7. The extending portion 3e is provided and fixed to the substrate 6 so as to be longer than the distance Lb to the opposite side portion of the gap portion 4 in FIG. The magnetosensitive element 5 is mounted on the substrate 6 so as to be disposed at a position corresponding to the central portion in the width direction on the end face of the magnetic core 3 facing the gap portion 4.

  Thus, in the present embodiment, the width Wa of the end surface of the magnetic core 3 that faces the gap 4 is larger than the width Wb of the portion of the magnetic core 3 opposite to the gap 4. For this reason, compared with the current sensor 50 shown in FIG. 2, the cross-sectional area of the magnetic pole part J of the magnetic core 3 becomes large, and the rate of change of the magnetic flux density distribution in the core radial direction in the gap part 4 can be reduced. .

  FIG. 5 is a plan view showing a third embodiment of the current sensor according to the present invention. In the figure, the same or equivalent elements as those in the first embodiment described above are denoted by the same reference numerals, and the description thereof is omitted.

  In the figure, the current sensor 1 of this embodiment includes a substantially annular magnetic core 3 having a gap portion 4. The magnetic core 3 includes a convex part 3h as a first part including an end face facing the gap part 4 and a semicircular second part provided on the opposite side of the gap part 4 with the conductor through hole 7 interposed therebetween. 3d and an extending portion 3e provided between the convex portion 3h and the second portion 3d.

  The width Wa of the end face of the convex portion 3h facing the gap portion 4 in the magnetic core 3 is larger than the width Wb of the second portion 3d which is the portion on the opposite side of the gap portion 4 in the magnetic core 3. . Specifically, the inner periphery 3a and the outer periphery 3b of the magnetic core 3 have an oval shape except for the gap portion 4 as in the first embodiment. And the convex part 3h of the magnetic body core 3 has the extending | stretching part 8 as a pair of protrusion part which protrudes to the core radial direction outer side of the magnetic body core 3. As shown in FIG. Other configurations are the same as those in the first embodiment.

  As described above, also in this embodiment, the width Wa of the end surface of the magnetic core 3 that faces the gap 4 is larger than the width Wb of the opposite side of the gap 4 in the magnetic core 3. As in the second embodiment, the rate of change in the magnetic flux density distribution in the core radial direction in the gap portion 4 can be reduced.

  The present invention is not limited to the above embodiment. For example, in the above embodiment, the peak of the magnetic flux density distribution in the core radial direction in the gap portion 4 of the magnetic core 3 is positioned at the center of the gap portion 4. The peak position is not particularly limited to this. According to the embodiment, since the magnetic flux density distribution in the core radial direction in the gap portion 4 can be arbitrarily adjusted, if the variation in detection sensitivity of the current sensor 1 can be reduced, the core in the gap portion 4 can be reduced. The peak position of the magnetic flux density distribution in the radial direction may be shifted from the center of the gap part 4.

  In the embodiment described above, the outer periphery 3b of the magnetic core 3 has an oval shape except for the gap portion 4, but the shape of the magnetic core 3 is not particularly limited thereto, and at least the magnetic core 3 The shape of the inner periphery 3a may be an oval shape (including an elliptical shape) except for the gap portion 4, and the shape of the outer periphery 3b of the magnetic core 3 may be a rectangular shape or the like.

  DESCRIPTION OF SYMBOLS 1 ... Current sensor, 2 ... Conductor, 3 ... Magnetic body core, 3a ... Inner periphery, 3b ... Outer periphery, 3c ... First part, 3d ... Second part, 3e ... Extension part, 3f ... Non-semicircular shape part (No. 1 part), 3h ... convex part (first part), 4 ... gap part, 5 ... magnetosensitive element, 7 ... conductor through hole (conductor passage area).

Claims (4)

In the current sensor that detects the current flowing through the conductor,
A substantially annular magnetic core provided to surround a conductor passage region through which the conductor passes, and having a gap;
A magnetic sensing element that is arranged in the gap part and detects a magnetic field generated in the gap part and converts it into an electric signal;
The inner periphery of the magnetic core has an oval shape except for the gap portion,
In the magnetic core, the distance from the center position of the conductor passage region to the gap portion is longer than the distance from the center position of the conductor passage region to a portion on the opposite side of the gap portion in the magnetic core. A current sensor having an extending portion.   2. The current sensor according to claim 1, wherein an outer periphery of the magnetic core has an oval shape corresponding to an inner periphery of the magnetic core except for the gap portion.   The extending portion has a length at which the peak of the magnetic flux density distribution in the radial direction of the magnetic core in the gap portion corresponds to the central portion in the width direction of the end surface of the magnetic core facing the gap portion. The current sensor according to claim 1, wherein the current sensor is a current sensor.   The extending portion is formed between a first portion including an end face of the magnetic core facing the gap portion and a semicircular second portion provided on the opposite side of the gap portion in the magnetic core. The current sensor according to claim 1, wherein the current sensor is a current sensor.

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