WO2016002501A1

WO2016002501A1 - Current sensor

Info

Publication number: WO2016002501A1
Application number: PCT/JP2015/067266
Authority: WO
Inventors: 川浪　崇
Original assignee: 株式会社村田製作所
Priority date: 2014-07-02
Filing date: 2015-06-16
Publication date: 2016-01-07
Also published as: JPWO2016002501A1; JP6311790B2

Abstract

This current sensor (1) comprises a primary conductor (10) and a magnetic sensor (20). In a branching section (11), the primary conductor (10) branches into two branch wires (10A, 10B). Said branch wires are in a twisted positional relationship (a relationship in which said branch wires do not lie in the same plane) with each other. Specifically, in a planar view in a Z direction (the direction parallel to shortest-distance imaginary lines connecting the two branch wires), the branch wires are each substantially rectangular and are formed so as to intersect in the approximate centers thereof with a prescribed angle (θ) between the directions in which the branch wires extend. The magnetic sensor is positioned in the space between the centers of the branch wires, and the axis of sensitivity (S0) of the magnetic sensor is set to the direction in which the primary conductor extends.

Description

Current sensor

The present invention relates to a current sensor, and more particularly to a current sensor including a primary conductor (bus bar) through which a current to be measured flows and a magnetic sensor that detects the strength of a magnetic field around the primary conductor.

Japanese Patent Application Laid-Open No. 8-233864 (Patent Document 1) discloses a current sensor including a coil (bus bar) wound around a magnetic core and a hall element provided in a gap (magnetic gap) of the magnetic core. Has been. This current sensor has a problem that it is difficult to reduce the size because it includes a magnetic core. A current sensor that solves this problem is disclosed in, for example, Japanese Patent Laid-Open No. 6-294854 (Patent Document 2).

The current sensor disclosed in Patent Document 2 includes a magnetic sensor chip. This magnetic sensor chip is provided with a Wheatstone bridge type bridge circuit having four magnetoresistive elements for detecting the strength of the magnetic field around the primary conductor (bus bar). Since this current sensor does not include a magnetic core, it can be miniaturized.

JP-A-8-233864 JP-A-6-294854 JP 2010-175474 A

However, in the current sensor disclosed in Patent Document 2, the strength of the magnetic field detected by the four magnetoresistive elements included in the magnetic sensor chip is the square of the distance between the four magnetoresistive elements and the primary conductor. Inversely proportional. Therefore, the sensitivity to the positions of the four magnetoresistive elements tends to be too high. As a result, there is a problem that it is difficult to manufacture a magnetic sensor chip because it is necessary to accurately arrange four magnetoresistive elements at a predetermined reference position with respect to the primary conductor. That is, if the positional relationship between the primary conductor and the magnetic sensor chip changes even a little, the measurement result greatly differs from the original value, and there is a problem that highly stable measurement cannot be performed.

The present invention has been made in view of the above problems, and an object of the present invention is to provide stability against a change in the positional relationship between the primary conductor and the magnetic sensor in a current sensor including the primary conductor and the magnetic sensor. Is to enable high measurement.

The current sensor according to the present invention is a current sensor for detecting a current to be measured, and includes a primary conductor through which the current to be measured flows and a magnetic sensor for detecting a magnetic field generated around the primary conductor. The primary conductor includes a plurality of branch lines through which a plurality of branch currents each branching the current to be measured flow. Each of the plurality of branch lines has a twisted portion formed such that the paths of two adjacent branch currents are in a twisted relationship with each other. The magnetic sensor is disposed in a gap sandwiched between the twisted portions of two adjacent branch lines, and one branch when viewed in plan from a direction along a virtual line connecting the two adjacent branch lines with the shortest distance. A magnetic field acting in a direction between the direction of the branch current flowing through the twisted portion of the line and the direction of the branch current flowing through the twisted portion of the other branch line is detected.

Preferably, the plurality of branch lines include three or more branch lines. The magnetic sensor includes two or more magnetic sensors. The current sensor calculates a current to be measured based on outputs of two or more magnetic sensors.

Preferably, the current sensor includes a member for magnetically shielding the primary conductor and the magnetic sensor from the outside.

Preferably, the plurality of branch lines are substantially rectangular when viewed in plan from the direction along the virtual line. The twisted portion is formed by arranging the extending directions of two adjacent branch lines so as to be in a twisted position relationship with each other.

Preferably, the plurality of branch lines are arranged in parallel to each other. The twisted portion is formed by notching a part of two adjacent branch lines so that the paths of the two adjacent branch currents are twisted with respect to each other.

Preferably, the magnetic sensor is a sensor that detects a current to be measured using a plurality of magnetoresistive elements.

According to the present invention, in a current sensor including a primary conductor and a magnetic sensor, highly stable measurement can be performed with respect to a change in the positional relationship between the primary conductor and the magnetic sensor.

It is a perspective view (the 1) of a current sensor. FIG. 3 is a three-side view (No. 1) showing the internal structure of the current sensor as seen through. FIG. 3 is a diagram (part 1) schematically illustrating magnetic flux generated around a magnetic sensor. It is a perspective view (the 2) of a current sensor. It is a figure which shows the structural example of a current sensor. It is the isointensity diagram (the 1) of the Y direction component of magnetic flux density. FIG. 3 is a diagram (part 1) illustrating a relationship between a position in a Z direction and a Y direction component of magnetic flux density. It is an isointensity diagram (the 2) of the Y direction component of magnetic flux density. It is a figure which shows the relationship between the position of a Y direction, and the Y direction component of magnetic flux density. It is the isointensity diagram (the 3) of the Y direction component of magnetic flux density. It is a figure which shows the relationship between the position of a X direction, and the Y direction component of magnetic flux density. It is the isointensity diagram (the 4) of the Y direction component of magnetic flux density. FIG. 6 is a diagram (part 2) illustrating a relationship between a position in the Z direction and a Y direction component of magnetic flux density. FIG. 6 is a three-view drawing (2) illustrating the internal structure of the current sensor as seen through. FIG. 5 is a diagram (part 2) schematically illustrating magnetic flux generated around the magnetic sensor.

Hereinafter, embodiments will be described with reference to the drawings. In the description of the embodiment, reference to the number, amount, and the like is not necessarily limited to the number, amount, and the like unless otherwise specified. In the drawings of the embodiments, the same reference numerals and reference numerals represent the same or corresponding parts. Further, in the description of the embodiments, the overlapping description may not be repeated for the portions with the same reference numerals and the like.

<Embodiment 1>
FIG. 1 is a perspective view of a current sensor 1 according to the present embodiment. FIG. 2 is a three-sided view showing the internal structure of the current sensor 1 in a transparent manner. FIG. 2A is a plan view of the current sensor 1. FIG. 2B is a cross-sectional view of the current sensor 1 taken along the line II of FIG. FIG. 2C is a cross-sectional view of the current sensor 1 taken along the line II-II in FIG.

The current sensor 1 according to the present embodiment will be described with reference to FIG. 1 and FIG. The current sensor 1 includes a primary conductor (bus bar) 10, a magnetic sensor 20, and a calculation unit (not shown). The current sensor 1 measures the value of the primary current i flowing through the primary conductor 10 based on the output of the magnetic sensor while maintaining insulation between the primary conductor 10 and the magnetic sensor 20.

The primary conductor 10 is a metal plate through which a primary current i to be measured flows. As a material of the primary conductor 10, copper, silver, aluminum, or the like can be used. The primary conductor 10 can be manufactured by a method such as pressing, cutting, casting, or forging. The surface of the primary conductor 10 may be subjected to a surface treatment such as plating with nickel, tin, copper, silver, or the like.

In the following, the current using an XYZ orthogonal coordinate system in which the plane parallel to the main surface of the primary conductor 10 is the XY plane, the direction in which the primary current i flows is the Y direction, and the direction perpendicular to the XY plane is the Z direction. The configuration of the sensor 1 will be described.

The number of primary conductors 10 is one on the upstream side of the branching section 11, but the branching section 11 branches into two branch lines 10 A and 10 B and becomes one again at the junction section 12. The two

branch lines

10A and 10B are formed such that the primary current i is branched almost equally into a branch current ia flowing through the branch line 10A and a branch current ib flowing through the branch line 10B in the branch section 11.

The two branch lines 10 A and 10 B are connected to each other at the branch portion 11 and the junction portion 12, but the connection method may be welding or fastening with a bolt and nut. Alternatively, it may be originally formed of a single metal plate, and may be three-dimensionally formed by pressing or drawing. It may be formed by shaving, casting or forging.

The two

branch lines

10A and 10B are in a twisted position relationship (a relationship that does not exist on the same plane). Specifically, as shown in FIG. 2A, two branches when viewed in plan from the Z direction (in other words, a direction along the virtual line connecting the two

branch lines

10A and 10B with the shortest distance). The

lines

10A and 10B are both formed so that the shape thereof is substantially rectangular, and the extending directions are inclined by a predetermined angle θ and intersect at substantially the center portion. As a result, the paths of the branch currents ia and ib when viewed in plan from the Z direction intersect at a predetermined angle θ at the center portions of the

branch lines

10A and 10B.

In the following, for convenience of explanation, a portion where the paths of the branch currents ia and ib intersect in plan view from the Z direction (in the present embodiment, the central portion of each

branch line

10A and 10B) is also referred to as a “twisted intersection portion”. Say.

The magnetic sensor 20 is disposed in a gap sandwiched between the twisted intersection portion (center portion) of the branch line 10A and the twisted intersection portion (center portion) of the branch line 10B. More specifically, the magnetic sensor 20 is disposed at an intermediate point between the twisted intersection portion of the branch line 10A and the twisted intersection portion of the branch line 10B. The magnetic sensor 20 measures the primary current i by detecting a magnetic field generated by the branch currents ia and ib.

The magnetic sensor 20 has a sensitivity axis S0. The direction of the sensitivity axis S0 of the magnetic sensor 20 is set in the Y direction (the extending direction of the primary conductor 10). More specifically, the direction of the sensitivity axis S0 flows through a twisted intersection portion of the branch line 10A when viewed in plan from the Z direction (a direction along a virtual line connecting the two

branch lines

10A and 10B with the shortest distance). The direction is set between the direction of the branch current ia and the direction of the branch current ib flowing through the twisted intersection of the branch line 10B. More specifically, the direction of the sensitivity axis S0 of the magnetic sensor 20 is set to be substantially parallel to the combined vector of the current vector indicating the branch current ia and the current vector indicating the branch current ia. The magnetic sensor 20 outputs a positive value when a magnetic flux directed in one direction of the sensitivity axis S0 is applied, and is negative when a magnetic flux directed in a direction opposite to the one direction of the sensitivity axis S0 is applied. Characteristic (hereinafter also referred to as “odd function input / output characteristics”).

The magnetic sensor 20 is an MR (Magneto Resistance) type magnetic sensor. The magnetic sensor 20 includes magnetoresistive elements such as AMR (Anisotropic Magneto Resistance), GMR (Giant Magneto Resistance), TMR (Tunnel Magneto Resistance), BMR (Ballistic Magneto Resistance), and CMR (Colossal Magneto Resistance), particularly AMR. A magnetic sensor comprising a Wheatstone bridge type bridge circuit or a half of the bridge circuit can be used as an element having an odd function input / output characteristic by providing a barber pole structure. In addition, as the magnetic sensor 20, a magnetic sensor using a Hall element, an MI (Magneto Impedance) magnetic sensor, a fluxgate magnetic sensor, or the like can be used.

When the magnetic sensor 20 is biased, the method is not limited to the method using the barber pole structure, and the magnetic sensor 20 may be biased using an induction magnetic field generated around the coil, a magnetic field of a permanent magnet, or a combination of these.

The magnetic sensor 20 may be of a type (open loop type) that outputs an output signal via an amplifier or a converter that calculates an output signal linearly or in a correction function, or drives an exciting coil via an amplifier or a converter. Thus, a type (closed loop type) in which feedback is always performed so that the magnetic field of the superposition of the magnetic field generated by the primary current i and the magnetic field generated by the exciting coil is fixed to a zero magnetic field or a constant magnetic field.

Although not shown, the magnetic sensor 20 and the

branch lines

10A and 10B are molded with an insulating resin and their mutual positional relationship is fixed. The type of resin for molding may be thermosetting or thermoplastic. Typically, PPS (polyphenylene sulfide), PCT (polycyclohexylene dimethylene terephthalate), LCP (liquid crystal polymer), nylon, epoxy resin, and the like, which are excellent in heat resistance and mold accuracy, are suitable.

The magnetic sensor 20 is electrically connected to a calculation unit (not shown) by connection wiring (not shown). The calculation unit calculates the value of the primary current i by removing and amplifying the offset (residual) of the output of the magnetic sensor 20. As the arithmetic unit, a non-inverting amplifier, a differential amplifier, an inverting amplifier, or the like can be used.

FIG. 3 is a diagram schematically showing a magnetic flux generated around the magnetic sensor 20 by the branch currents ia and ib. With reference to FIG. 3, the effect of the current sensor 1 by this Embodiment is demonstrated.

As branch currents ia and ib flow through

branch lines

10A and 10B, magnetic fluxes Φa and Φb corresponding to right-handed magnetic fields are generated around

branch lines

10A and 10B, respectively. The magnetic fluxes Φa and Φb are distributed on a plane whose normal is the direction of the branch currents ia and ib, respectively. Since the magnitudes of the branch currents ia and ib are substantially the same, if the directions of the branch currents ia and ib (current vector axes of the primary conductors) are parallel, the magnetic flux Φa, Φb cancels each other out with the “reason of superposition” and becomes zero.

However, in the present embodiment, the directions of the branch currents ia and ib are not parallel but intersect each other by a predetermined angle θ when viewed in plan from the Z direction. As described above, the branch currents ia and ib intersect each other by a predetermined angle θ in plan view, so that the magnetic fluxes Φa and Φb are in the X direction component at the intermediate point between the twisted intersection portion of the branch line 10A and the twisted intersection portion of the branch line 10B. Cancel each other by "superposition", but Y direction components are added together. A magnetic flux Φab acting in the Y direction is generated by adding the Y direction components of the magnetic fluxes Φa and Φb.

The magnitude of the magnetic flux Φab acting in the Y direction increases with an increase in the “predetermined angle θ” that is the crossing angle of the branch currents ia and ib when viewed in plan from the Z direction, and reaches a maximum at 180 degrees. Therefore, by adjusting the predetermined angle θ, the magnitude of the magnetic flux Φab acting in the Y direction can be freely set to a value proportional to sin (θ / 2). The sensitivity axis S0 of the magnetic sensor 20 is set in the positive direction of the Y direction (the same direction as the direction of the magnetic flux Φcd). Therefore, in the current sensor 1 according to the present embodiment, the primary current i having various magnitudes can be measured using the same magnetic sensor 20 by changing the predetermined angle θ according to the magnitude of the primary current i. Is possible.

In particular, in the present embodiment, since the shape of the

branch lines

10A and 10B when viewed in plan from the Z direction is substantially rectangular, the predetermined angle θ can be easily designed. Further, since the

branch lines

10A and 10B have a constant width and there is no narrow portion where the branch currents ia and ib concentrate, heat generation and the like can be minimized.

Further, at the position where the magnetic sensor 20 according to the present embodiment is arranged, that is, in the gap sandwiched between the twisted intersection portion of the branch line 10A and the twisted intersection portion of the branch line 10B, the Y direction (

branch lines

10A, 10B). No magnetic field other than the direction of extension) is generated. That is, the magnetic field in the X direction and the magnetic field in the Z direction, which may cause the output of the magnetic sensor 20 to become nonlinear or cause errors and noises, are not generated. Therefore, the current sensor 1 according to the present embodiment can realize high accuracy and can perform measurement with less influence of noise.

In addition, since the magnetic sensor 20 according to the present embodiment is disposed at the midpoint between the

branch lines

10A and 10B, it can be disposed at a sufficient distance from either of the

branch lines

10A and 10B. Therefore, the insulation between the magnetic sensor 20 and the

branch lines

10A and 10B can be easily and highly secured. As a result, the current sensor 1 realizing a high degree of insulation can be realized at low cost.

The magnetic sensor 20 according to the present embodiment is an MR type magnetic sensor. The sensitivity surface of the MR type magnetic sensor is parallel to the film forming surface, in other words, the mounting surface. Therefore, the substrate on which the functional film of the magnetic sensor 20 is formed can be parallel to the main surfaces of the

branch lines

10A and 10B. Therefore, the insulation between the magnetic sensor 20 and the

branch lines

In addition, since the current sensor 1 according to the present embodiment does not have a magnetic core, it can be reduced in size and weight, and the characteristics of the magnetic core (for example, frequency characteristics, nonlinearity, offset point due to residual magnetic flux density) In other words, the measurement can be performed without the influence of zero current drift and hysteresis.

Further, in the position where the magnetic sensor 20 according to the present embodiment is disposed, that is, in the gap sandwiched between the twisted intersection portion of the branch line 10A and the twisted intersection portion of the branch line 10B, the Y-direction component of the magnetic flux density with respect to the position. The amount of change is very small. Even if the current flowing in the

branch lines

10A and 10B is biased, the magnetic field generated at the position where the magnetic sensor 20 is disposed is almost unchanged and constant. Therefore, even if the position of the magnetic sensor 20 is shifted in any of the X direction, the Y direction, and the Z direction, and even if the current flowing through the

branch lines

10A and 10B is biased, measurement with high stability can be performed. It becomes possible. As a result, the current sensor 1 according to the present embodiment can perform measurement with high stability against a change in the position of the magnetic sensor 20 and a current bias between the

branch lines

10A and 10B, and a current with high reproducibility and productivity. The sensor 1 can be provided. This point will be described in detail in a simulation result described later.

<Modification 1 of Embodiment 1>
In the first embodiment described above, the above-described “twisted intersection portion” is formed by arranging the extending directions of the

branch lines

10A and 10B having a rectangular shape in a plan view so as to be in a twisted relationship with each other. It was.

However, the above-described method of forming the “twisted intersection” is not necessarily limited to disposing the extending directions of the branch lines 10 A and 10 B at the twisted positions.

FIG. 4 is a perspective view of the current sensor 1-1 according to this modification. The current sensor 1-1 shown in FIG. 4 is obtained by changing the

branch lines

10A and 10B to the branch lines 10A-1 and 10B-1 with respect to the current sensor 1 shown in FIG.

The branch lines 10A-1 and 10B-1 have a substantially rectangular shape when viewed in plan from the Z direction, and are arranged in parallel to each other. A plurality of notches are provided in the central portion of each branch line 10A-1, 10B-1. By these notches, the central portions of the branch lines 10A-1 and 10B-1 become the “twisted intersection” described above.

In other words, in the current sensor 1-1 according to the present modification, the extending directions of the branch lines 10A-1 and 10B-1 are not arranged at twisted positions, but instead of the branch lines 10A-1 and 10B-1. By cutting out a part of the central portion of each of the branch lines 10A-1 and 10B-1 so that the paths of the branch currents ia and ib flowing through the central portion are mutually twisted positions, Is formed.

Then, by adjusting the shape (depth, size, interval) of the notches, the paths of the branch currents ia and ib flowing through the central portions of the branch lines 10A-1 and 10B-1 (in plan view from the Z direction) The crossing angle of the branch currents ia and ib in this case can be freely set. Therefore, the measurable current value of the current sensor 1 can be adjusted without changing the outer shape of the current sensor 1 or the arrangement of its main components.

<Modification 2 of Embodiment 1>
The current sensor 1 according to the first embodiment and the current sensor 1-1 according to the first modification are not provided with a magnetic shield, but may be provided with a magnetic shield.

FIG. 5 is a diagram showing a configuration example of the current sensor 1-2 with a magnetic shield. A current sensor 1-2 shown in FIG. 5 is obtained by providing two sets of

magnetic shields

50 and 60 to the current sensor 1-1 according to the first modification described above.

The

magnetic shields

50 and 60 are each formed of a metal plate bent in a U-shape and arranged to face each other. The magnetic body used for the

magnetic shields

50 and 60 may be a metal such as iron, iron alloy, nickel or nickel alloy, such as permalloy, silicon steel, electromagnetic steel, soft iron steel, or pure iron. As magnetism, it is preferable that residual magnetic flux density and hysteresis are small. Moreover, it is preferable that the magnetic permeability is constant regardless of the magnetic flux density and the saturation magnetic flux density is large. In the second modification, the magnetic material used for the

magnetic shields

50 and 60 is permalloy.

Using the current sensor 1-2 according to the second modification, a simulation was performed in which the branch currents ia and ib were actually passed and the Y direction component of the magnetic flux density at that time was measured.

The simulation was performed with the current sensor 1-2 installed at the position shown in FIG. As shown in FIG. 5, in the current sensor 1-2, the width direction of the branch lines 10A-1 and 10B-1 is the X direction, the extending direction of the branch lines 10A-1 and 10B-1 is the Y direction, and the branch line 10A -1, 10B-1 are arranged on XYZ orthogonal coordinates with the Z direction as the thickness direction. In the following, the position of each part of the current sensor 1-2 is specified using the coordinates (X, Y, Z). The unit of the value of each coordinate is “mm (millimeter)”.

The sensitivity point of the magnetic sensor 20 is arranged at the position of the origin coordinates (0, 0, 0). The branch line 10A-1 is arranged at a position with the coordinates (0, −40, 2.5) as the center of the start point and the coordinates (0, 40, 2.5) as the center of the end point. The branch line 10B-1 is arranged at a position with the coordinates (0, −40, −2.5) as the center of the start point and the coordinates (0, 40, −2.5) as the center of the end point.

The branch lines 10A-1 and 10B-1 have a width of 10 mm, a length of 80 mm, a thickness of 1 mm, and a pure copper material. The distance between the centers of the branch lines 10A-1 and 10B-1 is 5 mm, and the gap is 4 m. The magnetic shield 60 has an outer width of 44 mm, an extension length of 60 mm, and a folding height of 28 mm. The magnetic shield 50 has an outer width of 32 mm, an extension length of 60 mm, and a folding height of 23 mm. The material of the shield part is silicon steel.

6 to 13 show the results of simulations in which the branch currents ia and ib are actually passed through the current sensor 1-2 arranged as described above and the Y direction component of the magnetic flux density at that time is measured.

FIG. 6 is an isointensity diagram of the Y direction component of the magnetic flux density when the branch currents ia and ib are equally set to 150 amperes. The isointensity diagram shown in FIG. 6 is drawn with respect to the XZ plane passing through the coordinates (0, 0, 0) where the magnetic sensor 20 is arranged.

FIG. 7 is a diagram showing the relationship between the position in the Z direction from the start point coordinates (0, 0, −2) to the end point coordinates (0, 0, 2) and the Y direction component of the magnetic flux density shown in FIG.

Even if the position in the Z direction changes in the range of about ± 2 mm around the center of the horizontal axis of the graph shown in FIG. 7 (near the coordinates (0, 0, 0) where the magnetic sensor 20 is arranged), the magnetic flux density The Y direction component is substantially constant at about 6.2 mT. Therefore, even if the position of the magnetic sensor 20 is shifted by several millimeters in the Z direction, highly stable measurement is possible.

FIG. 8 is an isointensity diagram of the Y direction component of the magnetic flux density when the branch currents ia and ib are evenly set at 150 amperes. The isointensity diagram shown in FIG. 8 is drawn with respect to the XY plane passing through the coordinates (0, 0, 0) where the magnetic sensor 20 is arranged.

FIG. 9 is a diagram showing the relationship between the position in the Y direction from the start point coordinates (0, −20, 0) to the end point coordinates (0, 20, 0) shown in FIG. 8 and the Y direction component of the magnetic flux density.

Near the center of the horizontal axis of the graph shown in FIG. 9 (near the coordinates (0, 0, 0) where the magnetic sensor 20 is arranged), even if the position in the Y direction changes within a range of about ± 2 mm, the magnetic flux density The Y direction component of is approximately 6.2 mT and is substantially constant. Therefore, even if the position of the magnetic sensor 20 is shifted by several millimeters in the Y direction, highly stable measurement is possible.

FIG. 10 is an isointensity diagram of the Y direction component of the magnetic flux density when the branch currents ia and ib are evenly set at 150 amperes. The isointensity diagram shown in FIG. 10 is drawn with respect to the XY plane passing through the coordinates (0, 0, 0) where the magnetic sensor 20 is arranged. The isointensity lines themselves shown in FIG. 10 are the same as those shown in FIG.

FIG. 11 is a diagram showing the relationship between the position in the X direction from the start point coordinates (−5, 0, 0) to the end point coordinates (5, 0, 0) shown in FIG. 10 and the Y direction component of the magnetic flux density.

Near the center of the horizontal axis of the graph shown in FIG. 11 (near the coordinates (0, 0, 0) where the magnetic sensor 20 is arranged), even if the position in the X direction changes within a range of about ± 2 mm, the magnetic flux density The Y direction component of is approximately 6.2 mT and is substantially constant. Therefore, even if the position of the magnetic sensor 20 is shifted by several millimeters in the X direction, highly stable measurement is possible.

FIG. 12 is an isointensity diagram of the Y direction component of the magnetic flux density when the branch current ia is 270 amperes and the branch current ib is 30 amperes (that is, when the branch currents ia and ib are biased). It is. The isointensity diagram shown in FIG. 12 is drawn with respect to the XZ plane passing through the coordinates (0, 0, 0) where the magnetic sensor 20 is arranged.

Note that there are various reasons why the deviation between the branch currents ia and ib actually occurs. For example, there is an increase in contact resistance due to insufficient tightening torque during assembly by tightening bolts and nuts.

FIG. 13 is a diagram showing the relationship between the position in the Z direction from the start point coordinates (0, 0, −2) to the end point coordinates (0, 0, 2) shown in FIG. 12 and the Y direction component of the magnetic flux density.

As shown in the simulation result of FIG. 13, when the ratio of the branch current ia to the branch current ib is extremely biased to one side such as 9: 1, the Y-direction component of the magnetic flux density depends on the position in the Z-direction. Change. However, in the vicinity of the center of the horizontal axis of the graph of FIG. 13 (near the coordinates (0, 0, 0) where the magnetic sensor 20 is arranged), the Y direction component of the magnetic flux density is about 6.2 mT, and the branch When the ratio of the current ia and the branch current ib is uniformly 1: 1 (see FIG. 7 above), the values are almost the same. Therefore, even if a deviation occurs between the branch currents ia and ib, measurement that is not affected by the deviation is possible.

As is apparent from the simulation results shown in FIGS. 6 to 13, the magnetic sensor 20 is sandwiched between the position where the magnetic sensor 20 is disposed, that is, between the twisted intersection of the branch line 10A-1 and the twisted intersection of the branch line 10B-1. In the gap, the amount of change in the Y direction component of the magnetic flux density with respect to the position is very small. Even if the current flowing in the branch lines 10A-1 and 10B-1 is biased, the Y direction component of the magnetic flux density is almost unchanged and constant. Therefore, even if the position of the magnetic sensor 20 is shifted in any of the X direction, the Y direction, and the Z direction, and even if a deviation occurs between the branch currents ia and ib, highly stable measurement is possible. It becomes.

The current sensor 1 according to the first embodiment described above or the current sensor 1-1 according to the first modification has the point where the paths of the branch currents ia and ib intersect when viewed in plan from the Z direction. Is the same. Therefore, even when a similar simulation is performed on the current sensors 1 and 1-1, a result showing substantially the same characteristics as the simulation results shown in FIGS. 6 to 13 is obtained.

<Embodiment 2>
In the above-described embodiment, one magnetic sensor is disposed between two branch lines, but three or more branch lines are provided, and two or more magnetic sensors respectively disposed between adjacent branch lines are provided. You may make it provide.

FIG. 14 is a three-sided view showing an example of the internal structure of the current sensor 1-3 according to the second embodiment. FIG. 14A is a plan view of the current sensor 1-3. FIG. 14B is a cross-sectional view of the current sensor 1-3 taken along the line II of FIG. FIG. 14C is a cross-sectional view of the current sensor 1-3 taken along the line II-II in FIG.

Although the number of primary conductors 10 included in the current sensor 1-3 is one on the upstream side of the branching portion 11, the branching portion 11 branches into three

branch lines

10C, 10D, and 10E. It becomes one again. The three

branch lines

10C, 10D, and 10E include a branch current ic in which the primary current i flows through the branch line 10C in the branch portion 11, a branch current id that flows through the branch line 10D, and a branch current ie that flows through the branch line 10E. Are formed so as to be branched almost evenly. As a method for connecting the three

branch lines

10C, 10D, and 10E, the same direction as the method described in the above embodiment may be adopted.

Each of the

branch lines

10C, 10D, and 10E is formed in a rectangular shape when viewed in plan from the Z direction. The branch line 10D is disposed between the branch line 10C and the branch line 10E.

The branch line 10 C and the branch line 10 D are arranged so as to have a twisted position relative to each other. The two

branch lines

10C and 10D are formed such that, when viewed in plan from the Z direction, the extending directions are inclined with respect to each other by a predetermined angle θ and intersect at substantially the center portion.

The branch line 10 D and the branch line 10 E are arranged so as to have a twisted position relationship with each other. The two

branch lines

10D and 10E are formed such that, when viewed in plan from the Z direction, the extending directions are inclined with respect to each other by a predetermined angle θ and intersect substantially at the center portion.

The branch line 10C and the branch line 10E are arranged in parallel to each other. Note that the branch line 10C and the branch line 10E are not necessarily arranged in parallel to each other.

The current sensor 1-3 includes two independent

magnetic sensors

21 and 22, and a calculation unit (not shown) that calculates the value of the primary current i using the outputs of the two

magnetic sensors

21 and 22.

The magnetic sensor 21 is disposed at an intermediate point between the branch line 10C and the branch line 10D. The direction of the sensitivity axis S1 of the magnetic sensor 21 is set to the positive direction of the Y direction. The magnetic sensor 22 is disposed at an intermediate point between the branch line 10D and the branch line 10E. The direction of the sensitivity axis S 2 of the magnetic sensor 22 is also set to the positive direction of the Y direction, like the magnetic sensor 21. The types and structures of the

magnetic sensors

21 and 22 are the same as those of the magnetic sensor 20 according to the first embodiment.

The current sensor 1-3 having such a configuration basically exhibits the same operational effects as those of the current sensor according to the first embodiment described above.

FIG. 15 is a diagram schematically showing the magnetic flux generated around the

magnetic sensors

21 and 22 by the branch currents ic, id, and ie.

As branch currents ic, id, and ee flow through

branch lines

10C, 10D, and 10E, magnetic fluxes Φc, Φd, and Φe corresponding to a right-handed magnetic field are generated around

branch lines

10C, 10D, and 10E, respectively. . The magnetic fluxes Φc, Φd, and Φe are distributed on a plane whose normal is the direction of the branch currents ic, id, and ee, respectively.

The directions of the branch currents ic and id intersect by a predetermined angle θ when viewed in plan from the Z direction. Therefore, at the position where the magnetic sensor 21 is arranged, that is, at the midpoint between the twisted intersection of the branch line 10C and the twisted intersection of the branch line 10D, as shown in FIG. 15, the magnetic flux Φcd acting in the positive direction of the Y direction. Will occur. The sensitivity axis S1 of the magnetic sensor 21 is set in the positive direction of the Y direction (the same direction as the direction of the magnetic flux Φcd). Therefore, the output of the magnetic sensor 21 is a positive value.

The directions of the branch currents id and ie intersect by a predetermined angle θ when viewed in plan from the Z direction. Therefore, at a position where the magnetic sensor 22 is arranged, that is, at an intermediate point between the twisted intersection portion of the branch line 10D and the twisted intersection portion of the branch line 10E, as shown in FIG. 15, the magnetic flux Φde acting in the negative direction in the Y direction. Will occur. The sensitivity axis S2 of the magnetic sensor 22 is set in the positive direction in the Y direction (direction opposite to the direction of the magnetic flux Φcd). Therefore, the output of the magnetic sensor 22 is a negative value.

Since the branch currents ic, id, and ie have almost the same value, the output of the magnetic sensor 21 and the output of the magnetic sensor 22 are approximately the same magnitude, and the signs are reversed. Considering this point, the arithmetic unit included in the current sensor 1-3 according to the present embodiment subtracts the output of the magnetic sensor 21 and the output of the magnetic sensor 22 (takes a differential). As a result, the output of the magnetic sensor 21 and the output of the magnetic sensor 22 are added together, and unnecessary noise magnetic fields from outside, that is, disturbance magnetic fields, etc. are canceled out and canceled out. As a result, an unnecessary noise magnetic field from the outside can be canceled, and a current sensor that is strong against disturbance can be realized.

Note that the calculation unit may amplify the differential result instead of simply taking the difference between the output of the magnetic sensor 21 and the output of the magnetic sensor 22.

The above-described embodiment and its modifications can be combined as appropriate.
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 current sensor, 10 primary conductor, 10A, 10B, 10C, 10D, 10E branch line, 11 branch part, 12 merge part, 20, 21, 22 magnetic sensor, 50, 60 magnetic shield.

Claims

A current sensor for detecting a current to be measured,
A primary conductor through which the current to be measured flows;
A magnetic sensor for detecting a magnetic field generated around the primary conductor,
The primary conductor includes a plurality of branch lines through which a plurality of branch currents from which the current to be measured flows are branched,
Each of the plurality of branch lines has a twisted portion formed such that two adjacent branch current paths are in a twisted position relationship with each other,
The magnetic sensor is disposed in a gap sandwiched between the twisted portions of two adjacent branch lines, and when viewed in plan from a direction along an imaginary line connecting the two adjacent branch lines with the shortest distance, A current sensor for detecting a magnetic field acting in a direction between a direction of a branch current flowing through the twisted portion of the branch line and a direction of the branch current flowing through the twisted portion of the other branch line.
The plurality of branch lines includes three or more branch lines;
The magnetic sensor includes two or more magnetic sensors,
The current sensor according to claim 1, wherein the current sensor calculates the measured current based on outputs of the two or more magnetic sensors.
The current sensor according to claim 1 or 2, wherein the current sensor includes a member for magnetically shielding the primary conductor and the magnetic sensor from the outside.
The plurality of branch lines are substantially rectangular when viewed in plan from the direction along the virtual line,
The current sensor according to any one of claims 1 to 3, wherein the twisted portion is formed by arranging the extending directions of two adjacent branch lines so as to have a twisted position relative to each other.
The plurality of branch lines are arranged in parallel to each other,
The twisted portion is formed by cutting out a part of two adjacent branch lines so that paths of two adjacent branch currents are twisted with respect to each other. The current sensor described.
The current sensor according to any one of claims 1 to 5, wherein the magnetic sensor is a sensor that detects the measured current using a plurality of magnetoresistive elements.