JP2014106101A - 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. The magnetic core 3 and the magnetic sensing element 5 are fixed to a substrate 6 having a conductor-through-hole 7 for letting the electric conductor 2 penetrate. A first part 3b facing the gap 4 in the magnetic core 3 extends only outward in a core diameter direction separating from the center of the conductor-through-hole 7 so that the width Wa of the first part 3b is wider than the width Wb of a semicircular-shaped second part 3c positioned in the gap 4 in the magnetic core 3. The magnetic sensing element 5 is disposed at a center part in the core diameter direction in 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 width of the first portion facing the gap portion in the magnetic core is a semicircular shape located on the opposite side of the gap portion in the magnetic core The first portion extends only in a direction away from the center of the conductor passage region so as to be larger than the width of the second portion.

  Thus, in the current sensor of the present invention, the width of the first portion facing the gap portion in the magnetic core is larger than the width of the semicircular second portion located on the opposite side of the gap portion in the magnetic core. As described above, the first portion is configured to extend only in the direction away from the center of the conductor passage region, so that the magnetic path through which the magnetic flux in the magnetic core passes is outside the core radial direction (conductor) in the first portion of the magnetic core. Shift to the opposite side of the passing area). 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 magnetic core is formed such that the distance from the center position of the conductor passage region to the gap portion is equal to the distance from the center position of the conductor passage region to a portion other than the gap portion in the magnetic core. The width of the magnetic core gradually increases from the second part toward the first part. In this case, without providing a corner portion in the magnetic core, the width of the first portion facing the gap portion in the magnetic core is made to be a semicircular second located on the opposite side of the gap portion in the magnetic core. It can be made larger than the width of the part. Therefore, since the shape of the magnetic path in the magnetic core is prevented from changing suddenly, magnetic saturation of the magnetic core can be prevented.

  The magnetic core is formed such that the distance from the center position of the conductor passage region to the gap portion is equal to the distance from the center position of the conductor passage region to a portion other than the gap portion in the magnetic core. One portion may have a protrusion protruding to the opposite side of the conductor passage region. In this case, without making the magnetic core larger than necessary, the width of the first portion facing the gap portion in the magnetic core is made to be a semicircular first located on the opposite side of the gap portion in the magnetic core. It can be larger than the width of the two parts.

  Preferably, the first portion is configured such that the peak of the magnetic flux density distribution in the radial direction of the magnetic core in the gap portion exists in the central portion in the radial direction of the magnetic core in the gap portion. In this case, the arrangement position of the magnetosensitive element can be easily adjusted.

  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 adhered to the substrate 6 in a state of being disposed so as to surround the conductor through hole 7 or is screwed through a bracket.

  The shape of the inner periphery 3 a of the magnetic core 3 is a perfect circle shape except for the gap portion 4. The magnetic core 3 is fixed to the substrate 6 so that the center position of the inner periphery 3 a coincides with the center position G of the conductor through hole 7. Therefore, in the magnetic core 3, the distance from the central position G of the conductor passage region 7 to the gap portion 4 is equal to the distance from the central position G of the conductor passage region 7 to a portion other than the gap portion 4 in the magnetic core 3. It is formed as follows. Moreover, the thickness of the magnetic core 3 is generally the same.

  The magnetic core 3 has a first portion 3 b facing the gap portion 4 and a semicircular second portion 3 c located on the opposite side of the gap portion 4 with the conductor passage region 7 interposed therebetween. Both end portions of the magnetic core 3 sandwiching the gap portion 4 are magnetic pole portions J of the magnetic core 3.

  The width Wa of the first portion 3 b in the magnetic core 3 is larger than the width Wb of the second portion 3 c in the magnetic core 3. Accordingly, the cross-sectional area of the first portion 3b is larger than the cross-sectional area of the second portion 3c. Specifically, the magnetic core 3 has a shape such that the width of the magnetic core 3 gradually increases from the second portion 3c toward the first portion 3b. That is, the first portion 3 b has the extending portion 3 d that extends only on the outer side in the core radial direction (opposite the conductor through hole 7) away from the center position G of the conductor passage region 7.

  The magnetosensitive element 5 is mounted on the substrate 6 so as to be disposed at the center of the gap 4 of the magnetic core 3 in the radial direction (core radial direction) 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. For this reason, the width W of the part facing the gap part 4 in the magnetic core 3 is substantially equal to the width of the part located on the opposite side of the gap part 4 in the magnetic core 3. The magnetosensitive element 5 is disposed in an inner region of the gap portion 4 in the core radial direction.

  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 width Wa of the first portion 3b facing the gap portion 4 in the magnetic core 3 is a semicircular shape located on the opposite side of the gap portion 4 in the magnetic core 3. The first portion 3b extends only outward in the core radial direction so as to be larger than the width Wb of the second portion 3c. 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 body core 3 becomes large, and the magnetic flux actuality from near the center of the gap part 4 to the core radial direction outer side becomes high. Further, the magnetic pole portion J is slightly pulled outward in the core radial direction by the extension of the magnetic pole portion J. 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 seems to have a magnetic flux density peak at the center in the core radial direction of the gap portion 4 as shown by the solid line P in FIG. Distribution can be obtained. That is, in the gap part 4, the area | region where magnetic flux density becomes uniform can be enlarged.

  In the present embodiment, the magnetosensitive element 5 is disposed near the peak of the magnetic flux density in the gap portion 4, that is, in the 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.

  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 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 has a first portion 3e facing the gap portion 4 and a semicircular second portion 3c located on the opposite side of the gap portion 4 with the conductor passage region 7 interposed therebetween. The first portion 3 e has a pair of protrusions 8 that protrude only outward in the core radial direction of the magnetic core 3. Accordingly, the width Wa of the first portion 3e facing the gap portion 4 in the magnetic core 3 is a semicircular second portion located on the opposite side of the gap portion 4 across the conductor through hole 7 in the magnetic core 3. It is larger than the width Wb of 3c.

  As described above, also in the present embodiment, the width Wa of the first portion 3e facing the gap portion 4 in the magnetic core 3 is the semicircular second portion 3c located on the opposite side of the gap portion 4 in the magnetic core 3. Since the first portion 3e extends only to the outside in the core radial direction so as to be larger than the width Wb, the peak of the magnetic flux density in the gap portion 4 shifts to the outside in the core radial direction as in the first embodiment. As described above, the magnetic flux density distribution in the core radial direction in the gap portion 4 can be changed.

  In the present embodiment, the first portion 3 e of the magnetic core 3 has only the protrusion 8 that protrudes outward in the core radial direction of the magnetic core 3, and protrudes inward in the core radial direction of the magnetic core 3. Therefore, it is not necessary to lengthen the distance between the magnetic pole part J and the conductor through hole 7. Therefore, an increase in size of the magnetic core 3 can be prevented.

  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 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 inner periphery 3 a of the magnetic core 3 has an oval shape except for the gap portion 4. Note that the oval shape referred to here includes not only a part that is linear, but also an elliptical shape that is entirely curved.

  The magnetic core 3 includes a first portion 3b facing the gap portion 4, a semicircular second portion 3c located on the opposite side of the gap portion 4 across the conductor passage region 7, a first portion 3b and a first portion It has the extending | stretching part 3f provided between the 2 parts 3c.

  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 extended portion 3 f extends from the position corresponding to the center position G of the conductor through hole 7 to the gap portion 4 side.

  Similar to the first embodiment, the magnetic core 3 has a shape such that the width of the magnetic core 3 gradually increases from the second portion 3c toward the first portion 3b. Therefore, the width Wa of the first portion 3b facing the gap portion 4 in the magnetic core 3 is a semicircular second portion located on the opposite side of the gap portion 4 across the conductor through hole 7 in the magnetic core 3. It is larger than the width Wb of 3c.

  As described above, in the present embodiment, the semicircular second portion in which the width Wa of the first portion 3 b facing the gap portion 4 in the magnetic core 3 is located on the opposite side of the gap portion 4 in the magnetic core 3. In addition to being larger than the width Wb of 3c, the distance La from the center position G of the conductor through hole 7 to the gap portion 4 is a portion of the magnetic core 3 opposite to the gap portion 4 from the center position G of the conductor through hole 7. Therefore, the magnetic flux is further pulled outward in the core radial direction at the magnetic pole portion J of the magnetic core 3. Therefore, the magnetic flux density distribution in the core radial direction in the gap portion 4 can be changed so that the peak of the magnetic flux density in the core radial direction in the gap portion 4 is further shifted outward in the core radial direction.

  In the present embodiment, the shape of the inner periphery 3a of the magnetic core 3 is an oval shape excluding the gap portion 4, and the width of the magnetic core 3 is directed from the second portion 3c to the first portion 3b. However, instead of such a configuration, the magnetic body core 3 itself has an oval shape except for the gap portion 4, and the second embodiment has the same configuration as that of the second embodiment. Thus, the protrusion 8 may be provided on the first portion 3 e of the magnetic core 3.

  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.

  DESCRIPTION OF SYMBOLS 1 ... Current sensor, 2 ... Conductor, 3 ... Magnetic body core, 3b ... 1st part, 3c ... 2nd part, 3e ... 1st part, 4 ... Gap part, 5 ... Magnetosensitive element, 7 ... Conductor through-hole ( Conductor passing region), 8 ... projections.

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 width of the first portion facing the gap portion in the magnetic core is larger than the width of the semicircular second portion located on the opposite side of the gap portion in the magnetic core. A current sensor characterized in that the portion extends only in a direction away from the center of the conductor passage region.   The magnetic core is formed such that the distance from the center position of the conductor passage region to the gap portion is equal to the distance from the center position of the conductor passage region to a portion other than the gap portion in the magnetic core. The current sensor according to claim 1, wherein the current sensor has a shape in which the width of the magnetic core gradually increases from the second portion toward the first portion. The magnetic core is formed such that the distance from the center position of the conductor passage region to the gap portion is equal to the distance from the center position of the conductor passage region to a portion other than the gap portion in the magnetic core. And
The current sensor according to claim 1, wherein the first portion has a protrusion protruding to the opposite side of the conductor passage region.   The first portion is configured such that a peak of a magnetic flux density distribution in the radial direction of the magnetic core in the gap portion exists in a central portion in the radial direction of the magnetic core in the gap portion. The current sensor according to any one of claims 1 to 3.

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