JP2016099160A - Current sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current sensor with a reduced size and enhanced detection accuracy.SOLUTION: A current sensor 1 includes: a ring-shaped core 3 with a gap 33, disposed surrounding a bus bar 2; and a Hall element 5, which has a magneto-sensitive surface 50 responsive to a magnetic field 8 induced in the gap 33 by current 7 flowing through the bus bar 2 and is mounted on a substrate 4, disposed such that a magneto-sensitive point 51, defined as a center of the magneto-sensitive surface 50, is at a position that is on an inner circumference side of a thickness center 11 of the core 3 and is closer to one of an end face 31 and end face 32 than to the other in the gap 33.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a current sensor.

  As a conventional technique, a ring-shaped magnetic core that surrounds the path of the current to be measured and has a gap portion of a predetermined width, a magnetic detection element positioned in the gap portion, and a magnetic core provided over the magnetic core and magnetically A current sensor including a support for holding a detection element is known (for example, see Patent Document 1).

  The current sensor support includes an accommodating portion that is formed in an intermediate portion thereof and accommodates the magnetic detection element in the internal space, an abutting portion that is formed on the inner wall portion of the peripheral portion and abuts on the peripheral surface of the magnetic core, and both sides thereof And an arm portion that extends to the side of the pair of magnetic cores and is engaged with the engaged portions formed on both side surfaces of the magnetic core at the engaging portion of the tip portion.

  In addition, the support is positioned with respect to the magnetic core by the contact portion being in contact with the peripheral surface of the magnetic core and the locking portion of the arm portion being locked to the locked portion of the magnetic core, thereby detecting the magnetic force. The element is disposed at the center of the gap portion in a state where the displacement is regulated by contacting the wall portion of the internal space of the housing portion. Therefore, this current sensor can be made less susceptible to the influence of an external magnetic field by positioning the magnetic detection element stably and accurately at the central portion in the gap portion of the magnetic core.

JP 2013-164288 A

  However, in the conventional current sensor, since the magnetic detection element is arranged at the center of the gap portion of the magnetic core, the gap portion is formed wide. Therefore, this current sensor has a problem that the magnetic flux density in the gap portion decreases as the gap portion becomes wide, so that the detection accuracy of the magnetic field must be set high, and the SN ratio decreases.

  Accordingly, an object of the present invention is to provide a current sensor that can be miniaturized and can increase detection accuracy.

  One embodiment of the present invention has a ring shape in which a gap is formed, a core disposed so as to surround the conductor, and a magnetosensitive surface that reacts to a magnetic field generated in the gap based on a current flowing through the conductor. And a magnetic sensing element that is mounted on the substrate and is arranged such that the center of the magnetosensitive surface is on the inner peripheral side of the thickness center of the core and shifted to either one of the opposing end faces in the gap. A current sensor is provided.

  According to the present invention, it is possible to reduce the size and increase the detection accuracy.

FIG. 1A is a perspective view of a current sensor according to the embodiment, and FIG. 1B is a front view of the current sensor. 2A is a schematic diagram simulating the influence of a disturbance magnetic field in the core gap of the current sensor according to the embodiment, and FIG. 2B is a diagram around the gap for explaining the arrangement of the magnetic sensor. FIG.

(Summary of embodiment)
The current sensor according to the embodiment has a ring shape in which a gap is formed, a core disposed so as to surround the conductor, and a magnetosensitive sensor that reacts to a magnetic field generated in the gap based on a current flowing through the conductor. A magnetic sensing element that is mounted on a substrate having a surface and is arranged such that the center of the magnetosensitive surface is on the inner peripheral side from the thickness center of the core and shifted to either one of the opposing end faces in the gap. In general, it is structured.

[Embodiment]
(Configuration of current sensor 1)
FIG. 1A is a perspective view of a current sensor according to the embodiment, and FIG. 1B is a front view of the current sensor. Note that, in each drawing according to the embodiment described below, the ratio between figures may be different from the actual ratio.

  As an example, the current sensor 1 is a current sensor that measures the current of a lead battery mounted on a vehicle. This current sensor 1 is electrically connected to the negative electrode of the lead battery. In FIG. 1A and FIG. 1B, it is assumed that the current 7 flows from the front side to the back in FIG. 1B. Therefore, on the paper surface of FIG. 1B, the magnetic field 8 is generated clockwise, and a part of the magnetic field 8 forms a magnetic path 80 inside the core 3.

  As shown in FIG. 1A and FIG. 1B, the current sensor 1 has a ring shape in which a gap 33 is formed, and a core 3 arranged so as to surround the periphery of the bus bar 2 as a conductor. And mounted on the substrate 4 with a magnetic sensitive surface 50 that reacts to the magnetic field 8 generated in the gap 33 based on the current 7 flowing through the bus bar 2, and the magnetic sensitive point 51 as the center of the magnetic sensitive surface 50 is the core 3. And a magnetic detection element arranged on the inner peripheral side of the thickness center 11 and shifted to either one of the end face 31 and the end face 32 facing each other in the gap 33. As an example, the magnetic detection element is a Hall element 5.

(Configuration of bus bar 2)
The bus bar 2 is formed so as to have an elongated plate shape by punching a conductive plate member such as copper, a copper alloy, and brass. The shape of the bus bar 2 is not limited to a plate shape, and may be an arbitrary shape.

  The bus bar 2 is electrically connected to the negative electrode of the lead battery. The bus bar 2 is inserted into the through hole 30 of the core 3 as shown in FIG.

(Configuration of core 3)
For example, the core 3 has a shape in which a part of an ellipse is cut off. This cut-out area is a gap 33. As an example, the core 3 is obtained by integrating a plurality of plate-like cores having a plate shape by press working. The plate-like core is formed using a soft magnetic material such as permalloy, an electromagnetic steel plate (silicon steel plate), or ferrite.

  The core 3 has a through hole 30 into which the bus bar 2 is inserted. Further, the end surface 31 and the end surface 32 which are the end portions of the gap 33 are located in the major axis direction of the core 3.

  In the core 3, for example, as shown in FIG. 1B, a magnetic path 80 is formed that closes through the inside of the core 3 and the gap 33 when a current 7 flows through the bus bar 2. The magnetic flux 81 in the gap 33 springs out from the end face 31 and is sucked into the end face 32 as shown in FIG.

(Configuration of Hall element 5)
The Hall element 5 is a magnetic sensor that outputs an electrical signal corresponding to the magnetic flux 81 penetrating the magnetosensitive surface 50 based on the Hall effect. The magnetic sensitive point 51 described above is the center of the magnetic sensitive surface 50.

  For example, the Hall element 5 is disposed on a substrate 4 which is a rigid substrate, and is configured as a magnetic sensor 6 together with an amplifier circuit, a control circuit, and the like disposed on the substrate 4. In the magnetic sensor 6, for example, the Hall element 5 outputs an electric signal corresponding to the magnetic flux 81 in the gap 33 to the control circuit via the amplifier circuit, and the control circuit calculates the current value based on the amplified electric signal. It is configured to calculate and output.

  The Hall element 5 may be disposed on the substrate 4 in a bare chip state, for example, or may be disposed on the substrate 4 as a part of a Hall IC (Integrated Circuit) molded with resin, including an amplifier circuit and a control circuit. May be.

(Regarding arrangement of Hall element 5)
2A is a schematic diagram simulating the influence of a disturbance magnetic field in the core gap of the current sensor according to the embodiment, and FIG. 2B is a diagram around the gap for explaining the arrangement of the magnetic sensor. FIG. The intensity of the disturbance magnetic field 9 in FIG. 2A is approximately equal to the upper side of the thickness center 11 and about one third of that of the lower strong place. This lower strong place is near the outer periphery of the lower end face 31 and the end face 32.

  As described above, the Hall element 5 is arranged such that the magnetosensitive point 51 is shifted from the thickness center 11 of the core 3 to the inner peripheral side and to either the end face 31 or the end face 32. Specifically, when the X axis is set from the left to the right in FIG. 1B and the Y axis is set from the bottom to the top, the Hall element 5 has a magnetic sensitive point 51 at the center and end face of the through hole 30 of the core 3. The gap center 10 passing through the center between the end face 31 and the end face 32 is shifted by ± ΔX, and the thickness center 11 passing through the center of the end face 31 and the end face 32 is shifted by + ΔY.

  Here, when the disturbance magnetic field 9 is acting from the outside of the gap 33 in the state where the current 7 does not flow through the bus bar 2, the magnetic vector 90 of the gap 33 is, for example, as shown in FIG. Distributed. Specifically, the influence of the disturbance magnetic field 9 is large on the outer peripheral side of the core 3, and the inner peripheral side is small. Therefore, the X-axis direction component of the magnetic vector 90 related to detection is smaller on the upper side than the thickness center 11 compared to the lower side.

  Accordingly, the Hall element 5 is arranged in the arrangement region 100 on the inner peripheral side from the thickness center 11 as shown in FIG. As shown in FIG. 2A, the arrangement region 100 is a region surrounded by a dotted line excluding the gap center 10.

  Although it is generally preferable that the Hall element 5 is arranged so that the magnetic sensitive point 51 is positioned at the gap center 10 of the gap 33, there are the following problems. When the Hall element 5 is arranged so that the magnetosensitive point 51 is positioned on the gap center 10, it is necessary to widen the gap 33 according to the thickness of the substrate 4 and the thickness of the Hall element 5.

  That is, the gap 33 needs to be at least twice as thick as the thickness of the substrate 4 and the thickness from the substrate 4 to the magnetosensitive surface 50. When the gap 33 is wide, the magnetic flux density in the gap 33 decreases, so that the detection sensitivity of the Hall element 5 needs to be increased. However, when the detection sensitivity is increased, the Hall element 5 is more easily affected by the disturbance magnetic field than before being increased. As a result, there is a problem that the SN ratio of the current sensor is lowered and the resistance to the disturbance magnetic field is lowered.

  On the other hand, the current sensor 1 of the present embodiment is arranged in the arrangement region 100 on the inner peripheral side where the influence of the disturbance magnetic field is small, and is further arranged shifted to the end surface 31 or the end surface 32 side. That is, the Hall element 5 is not arranged so that the magnetic sensitive point 51 is positioned on the gap center 10. Therefore, the current sensor 1 can narrow the gap 33 as close to the thickness of the magnetic sensor 6, and can be configured such that the decrease in magnetic flux density is suppressed and the detection sensitivity does not need to be increased.

  2B, when the gap 33 is narrowed to the thickness of the magnetic sensor 6 as shown in FIG. 2B, the end face 31 or the end face 32 than the arrangement region 100 where the magnetosensitive point 51 is near the gap center 10 is used. The Hall element 5 is arranged so as to be located in the arrangement region 101 surrounded by the dotted line, which is close to. In this arrangement region 101, the influence of the disturbance magnetic field 9 is larger than that near the gap center 10, but the influence of the disturbance magnetic field 9 is reduced by narrowing the gap 33, and the detection accuracy obtained by increasing the magnetic flux density is improved. Compared with, the influence on detection accuracy is small.

  Further, the Hall element 5 is arranged such that the magnetosensitive point 51 is located in a region near the end face 32 where the magnetic flux 81 of the magnetic field 8 in the gap 33 is sucked (for example, the arrangement region 101 on the left side in FIG. 2A). Is preferred. This is because the direction of the magnetic vector 90 in the gap 33 and the direction of the magnetic flux 81 in the gap 33 caused by the current 7 flowing in the bus bar 2 are matched as shown in FIGS. 1 (a) and 2 (a). is there. This is because if both directions are opposite directions, the detection sensitivity may be slightly reduced due to cancellation even though they are small.

(Effect of embodiment)
The current sensor 1 according to the present embodiment can be downsized and the detection accuracy can be increased. Specifically, the current sensor 1 is arranged such that the magnetic sensitive point 51 of the Hall element 5 mounted on the substrate 4 is shifted to the inner peripheral side of the core 3 and to the end face 31 or the end face 32 side. 10, it is not necessary to position the magnetic sensitive point 51, and the gap 33 can be narrowed to increase the magnetic flux density of the gap 33. In the current sensor 1, since the magnetic flux density in the gap 33 is increased, it is not necessary to increase the detection sensitivity, the SN ratio is increased, and the detection accuracy is improved. In addition, the current sensor 1 has the Hall element 5 disposed so that the magnetosensitive point 51 is located at a position where the influence of the disturbance magnetic field is small, and the SN ratio is large, so that the resistance to the disturbance magnetic field is improved.

  Since the Hall element 5 is mounted on the substrate 4 in the current sensor 1, the gap 33 is widened by arranging the magnetic sensor 6 so that the magnetic sensitive point 51 is positioned at the gap center 10. However, the current sensor 1 does not require the magnetic sensor 6 to be disposed so that the magnetic sensitive point 51 is positioned at the gap center 10, and therefore the gap 33 can be narrowed and the size can be reduced.

  In the current sensor 1, the Hall element 5 is arranged near the end face 32 where the magnetic flux 81 in the gap 33 is sucked so that the magnetic sensitive point 51 is located. Therefore, the direction of the magnetic vector 90 by the disturbance magnetic field 9 and the magnetic flux 81 are arranged. As compared with the case where both directions are substantially the same and the directions are opposite to each other, it is possible to suppress a decrease in detection accuracy.

  Although the embodiment of the present invention has been described above, this embodiment is merely an example, and does not limit the invention according to the claims. The novel embodiment can be implemented in various other forms, and various omissions, replacements, changes, and the like can be made without departing from the gist of the present invention. In addition, not all the combinations of features described in the embodiments are essential to the means for solving the problems of the invention. Further, the embodiments are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Current sensor 2 ... Bus bar 3 ... Core 4 ... Board | substrate 5 ... Hall element 6 ... Magnetic sensor 7 ... Current 8 ... Magnetic field 9 ... Disturbance magnetic field 10 ... Gap center 11 ... Thickness center 30 ... Through-hole 31 ... End surface 32 ... End surface 33 ... Gap 50 ... Magnetic sensitive surface 51 ... Magnetic sensitive point 80 ... Magnetic path 81 ... Magnetic flux 90 ... Magnetic vector 100 ... Arrangement area 101 ... Arrangement area

Claims (3)

A core having a ring shape in which a gap is formed and arranged to surround a conductor;
Mounted on a substrate having a magnetic sensitive surface that reacts to a magnetic field generated in the gap based on a current flowing through the conductor, the center of the magnetic sensitive surface being on the inner peripheral side of the thickness center of the core, and the A magnetic detecting element arranged to be shifted to one of the opposing end faces in the gap;
With current sensor. The magnetic detection element is arranged such that the center of the magnetosensitive surface is located in a region closer to the end face than the center of the gap.
The current sensor according to claim 1. The magnetic detection element is arranged such that the center of the magnetosensitive surface is located in a region near the end surface where the magnetic flux of the magnetic field in the gap is sucked.
The current sensor according to claim 2.

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