WO2012035906A1

WO2012035906A1 - Current sensor

Info

Publication number: WO2012035906A1
Application number: PCT/JP2011/067889
Authority: WO
Inventors: 蛇口　広行
Original assignee: アルプス・グリーンデバイス株式会社
Priority date: 2010-09-17
Filing date: 2011-08-04
Publication date: 2012-03-22

Abstract

The purpose of the present invention is to provide a current sensor which can reduce the influence of magnetic disturbances and suppress a drop in current measuring accuracy, when using a magnetic sensor element, such as a GMR element, which has sensitivity in the direction orthogonal to the sensitive axis. This current sensor (1) is equipped with: a pair of magnetic sensors (12a, 12b) which are arranged around an electric wire (11) through which the current being measured flows, and which output a reversed phase output signal by means of the induction field from the current flowing through the electric wire (11), and which each have sensitivity in the direction orthogonal to the sensitive axis; and a calculation device (13) which is connected to the pair of magnetic sensors (12a, 12b), and which carries out a differential calculation on the output signals from the pair of magnetic sensors (12a, 12b). The current sensor (1) is characterised in that the magnetic sensors (12a, 12b) are arranged such that the non-sensitive axes thereof face in the direction of the induction field from the current flowing through an electric wire (adjacent electric wire (21)) which is adjacent to the electric wire (11).

Description

Current sensor

The present invention relates to a current sensor that measures the magnitude of current. In particular, the present invention relates to a current sensor in which a decrease in measurement accuracy due to a disturbance magnetic field is suppressed.

In fields such as motor drive technology in electric vehicles and hybrid cars, a relatively large current is handled, and thus a current sensor capable of measuring a large current in a non-contact manner is required for such applications. As such a current sensor, a system that detects a change in a magnetic field caused by a current to be measured by a magnetic sensor has been put into practical use. A current sensor using a magnetic sensor has a problem in that the measurement accuracy is deteriorated due to the influence of a disturbing magnetic field.

As a method for suppressing a decrease in measurement accuracy due to the influence of a disturbance magnetic field, for example, a method of taking a differential between output signals of two magnetic sensors has been proposed (see Patent Document 1). In this configuration, in the output signals of the two magnetic sensors, the influence of the magnetic field formed by the current to be measured appears in the opposite phase, and the influence of the disturbance magnetic field appears in the same phase. Can be removed.

JP 2002-131342 A

Incidentally, as a magnetic sensor used for the above-described current sensor, a GMR (Giant Magneto Resistance) element or the like can be used in addition to the Hall element. The GMR element may have sensitivity in a direction orthogonal to the sensitivity axis because of its structure. For example, the sensitivity may be about several tens of percent of the sensitivity in the sensitivity axis direction. When such a magnetic sensor element having sensitivity also in the direction orthogonal to the sensitivity axis is used for the current sensor, the influence of the disturbance magnetic field is sufficiently suppressed even if the technique described in Patent Document 1 is simply applied. It ’s difficult. This is based on the premise that the technique described in Patent Document 1 uses a magnetic sensor element that does not have sensitivity in a direction orthogonal to the sensitivity axis, such as a magnetic impedance element or a Hall element. This is because the use of a magnetic sensor element having sensitivity also in the direction orthogonal to the sensitivity axis is not considered.

The present invention has been made in view of such points, and in the case of using a magnetic sensor element having sensitivity in a direction orthogonal to the sensitivity axis, such as a GMR element, the influence of a disturbance magnetic field is reduced, and current measurement accuracy is reduced. An object is to provide a current sensor that can be suppressed.

The current sensor according to the present invention is arranged around a current line through which a current to be measured flows, and outputs an output signal having a reverse phase by an induced magnetic field from the current flowing through the current line. A pair of magnetic sensors each having sensitivity, and an arithmetic device connected to the pair of magnetic sensors and differentially calculating output signals of the pair of magnetic sensors, the magnetic sensor having its insensitive axis Is arranged so as to face the direction of the induced magnetic field from the current flowing through the current line adjacent to the current line.

According to this configuration, the sensitivity axis and the axis that faces the direction in which the sensitivity is minimum among the directions orthogonal to the sensitivity axis (hereinafter sometimes referred to as an insensitive axis) are provided. The insensitive axis of the magnetic sensor having sensitivity also in a direction orthogonal to the direction of current flows from a current passing through a current line adjacent to the current line through which the current to be measured flows (hereinafter sometimes referred to as an adjacent current line). The magnetic sensor is arranged so as to face the direction of the induction magnetic field. For this reason, the influence of the induced magnetic field from the current flowing through the adjacent current line can be sufficiently reduced, and the decrease in current measurement accuracy due to the influence of the current flowing through the adjacent current line can be suppressed.

In the present specification, the term “current line” merely indicates a component capable of guiding current, and is not used for the purpose of limiting that the shape is a “line” shape. For example, the “current line” includes a plate-shaped conductive member, a thin-film conductive member (conductive pattern), and the like. In this specification, the “sensitivity axis” refers to an axis that faces the direction in which the sensitivity of the magnetic sensor (or magnetic sensor element) is maximized, and the “insensitive axis” refers to a direction orthogonal to the sensitivity axis. Of these, the axis oriented in the direction where the sensitivity is minimized is assumed.

In the current sensor of the present invention, the magnetic sensor may be arranged such that a direction perpendicular to the sensitivity axis and having sensitivity coincides with a direction in which the current line extends. Since the direction of the induced magnetic field is orthogonal to the direction of the current, that is, the direction of the current line, the direction perpendicular to the sensitivity axis and having the sensitivity extends the current line through which the current to be measured flows. By matching with the direction in which the adjacent current line extends (same as the direction in which the adjacent current line extends), the influence of the induced magnetic field from the current flowing through the adjacent current line can be sufficiently reduced. That is, it is possible to suppress a decrease in current measurement accuracy due to the influence of the adjacent current line.

In the present specification, the expression “coincidence” in the direction is used to include a substantial coincidence that does not lose the effect of the invention. For example, a deviation in a direction that does not affect the measurement accuracy is allowed.

In the current sensor according to the present invention, the pair of magnetic sensors may be arranged such that directions that are perpendicular to the sensitivity axis and have sensitivity are opposite to each other. According to this configuration, the influence from the current line extending in the direction orthogonal to the sensitivity axis and not parallel to the direction having sensitivity (for example, the direction orthogonal) is canceled by differential calculation. There are things that can be done. For this reason, it is possible to suppress a decrease in current measurement accuracy.

In the current sensor of the present invention, the magnetic sensor may include a GMR element. According to this configuration, sufficient current measurement accuracy can be ensured by using the GMR element.

In the current sensor of the present invention, the direction of the sensitivity axis and the direction perpendicular to the sensitivity axis and having sensitivity coincide with one of the directions parallel to the main surface of the substrate on which the GMR element is provided, The direction of the insensitive axis may coincide with the direction perpendicular to the main surface of the substrate. In this configuration, since the current line and the main surface of the substrate on which the GMR element is provided are parallel, it is possible to save the space of the current sensor.

In the current sensor of the present invention, the pair of magnetic sensors is mounted, and includes a circuit board disposed in a plane perpendicular to the current line, and the direction of the sensitivity axis and the direction of the insensitive axis are: It may coincide with one of the directions parallel to the main surface of the circuit board. In this configuration, since the direction of the insensitive axis of the magnetic sensor coincides with the direction parallel to the main surface of the circuit board, it is possible to save the space of the current sensor.

In the current sensor of the present invention, the influence of the induced magnetic field from the current flowing through the adjacent current line is sufficiently reduced by devising the arrangement of the magnetic sensor having sensitivity in the direction orthogonal to the sensitivity axis. For this reason, even when such a magnetic sensor is used, it is possible to suppress a decrease in current measurement accuracy due to the influence of the current flowing through the adjacent current line.

It is a schematic diagram which shows the structural example of a current sensor. It is a schematic diagram which shows the structural example of a current sensor. It is a figure which shows the mode of a magnetic field in case two adjacent current lines exist. It is a figure which shows the circuit structural example of a current sensor. It is a cross-sectional schematic diagram which shows the laminated structure of a GMR element. It is a schematic diagram which shows the structural example of a current sensor. It is a schematic diagram which shows the structural example of a current sensor. It is a schematic diagram which shows the structural example of a current sensor. It is a figure which shows the measurement system in an Example. It is a figure which shows the measurement error in the structure of an Example and a comparative example.

The present inventors have sensitivity in a direction perpendicular to a sensitivity axis of a GMR element or the like in an environment where a current line (adjacent current line) adjacent to the current sensor such as a switchboard or a three-phase motor exists. When using a magnetic sensor element, the magnetic sensor including the magnetic sensor element is arranged so as to reduce the influence of the induced magnetic field from the current flowing through the adjacent current line, thereby suppressing a decrease in current measurement accuracy. Found that you can. In particular, the magnetic sensor is arranged such that the insensitive axis of the magnetic sensor faces the direction of the induced magnetic field from the current flowing through the adjacent current line, or the direction that is perpendicular to the sensitivity axis of the magnetic sensor and is sensitive. By arranging so that the direction with the current line coincides with the direction in which the adjacent current line extends, the influence of the induced magnetic field from the current flowing through the adjacent current line can be sufficiently reduced to reduce the current measurement accuracy. It was found that it can be effectively suppressed.

That is, the essence of the present invention is that the current sensor of the type that removes the influence of the disturbance magnetic field by differential calculation uses a magnetic sensor having sensitivity also in the direction orthogonal to the sensitivity axis. However, the magnetic sensor is arranged so as to face the direction of the induced magnetic field from the current flowing through the adjacent current line, or the direction having the sensitivity perpendicular to the sensitivity axis of the magnetic sensor is the adjacent current line. It is intended to suppress a decrease in current measurement accuracy by arranging it so as to coincide with the extending direction. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
In the present embodiment, an example of the current sensor 1 of the present invention will be described. FIG. 1 is a schematic diagram showing the current sensor 1 of the present embodiment. FIG. 1A is a perspective view schematically showing the configuration of the current sensor 1 and its periphery, and FIG. 1B is a plan view thereof. In FIG. 1A, solid arrows given to the current line 11 and the adjacent current line 21 indicate that the direction of the current flowing through them is upward on the page. That is, here, the current to be measured and the adjacent current flow in directions parallel to each other. In FIGS. 1A and 1B, a long solid arrow 14a, a short solid arrow 14b, and a broken arrow 14c applied to the first magnetic sensor 12a and the second magnetic sensor 12b are , The direction of the sensitivity axis, the direction perpendicular to the sensitivity axis and having sensitivity, and the direction of the insensitive axis, respectively. For example, two long and short solid arrows and a broken arrow attached to the first magnetic sensor 12a indicate that the direction of the sensitivity axis of the first magnetic sensor 12a is the upper right direction in FIG. 14a), the sensitivity is also upward in FIG. 1A (short arrow 14b), and the insensitive axis is rightward in FIG. 1A (dashed arrow 14c). Further, in FIG. 1B, a mark given to the current line 11 and the adjacent current line 21 indicates that current flows forward in the drawing.

In addition, the direction of the current flowing through the current line 11 and the adjacent current line 21 and the direction of the sensitivity axis of the magnetic sensor may be reversed. Since FIG. 1 is a schematic diagram, the size, quantity, arrangement, and the like of each component can be changed as appropriate. Moreover, since FIG. 1 is a figure for showing the feature point of this Embodiment in an easy-to-understand manner, a part of the configuration of the current sensor 1 may be omitted in FIG.

As shown in FIG. 1, the current sensor 1 includes a current line 11 through which a current to be measured flows, and a first magnetic sensor 12a and a second magnetic sensor 12b arranged around the current line 11. Here, the current line 11 extends in a predetermined direction (the vertical direction in FIG. 1A). In addition, the current sensor 1 includes an arithmetic device (not shown) that differentially calculates the output signals of the first magnetic sensor 12a and the second magnetic sensor 12b.

The first magnetic sensor 12a and the second magnetic sensor 12b are preferably a magnetic proportional sensor or a magnetic balanced sensor. The magnetic proportional sensor is configured to include, for example, a bridge circuit including two magnetoresistive elements that are magnetic sensor elements and two fixed resistance elements. In addition, the magnetic balance sensor is, for example, a bridge circuit composed of two magnetoresistive elements and two fixed resistance elements that are magnetic sensor elements, and a magnetic field in a direction that cancels the magnetic field generated by the current to be measured. And a feedback coil. When a magnetic proportional sensor is employed, a configuration relating to a feedback coil and its control, such as a magnetic balance sensor, is not required, so that the configuration can be simplified and the current sensor can be reduced in size. On the other hand, when a magnetic balance sensor is employed, a current sensor having a high response speed and a small temperature dependence can be easily realized.

The magnetoresistive effect element used for the first magnetic sensor 12a and the second magnetic sensor 12b includes a GMR (Giant Magneto Resistance) element and a TMR (Tunnel Magneto Resistance) element. Here, the magnetoresistive effect element is orthogonal to the sensitivity axis. A GMR element having sensitivity also in the direction to be used is used. A magnetoresistive element such as a GMR element has a property that a resistance value changes by application of an induced magnetic field from a current to be measured, and this is used for the first magnetic sensor 12a and the second magnetic sensor 12b. Thus, sufficient current measurement accuracy can be ensured. In the current sensor 1 of the present embodiment, the magnetoresistive effect element used for the first magnetic sensor 12a and the second magnetic sensor 12b is a GMR as long as it has sensitivity in the direction orthogonal to the sensitivity axis. It is not limited to being an element.

In the current sensor 1, the first magnetic sensor 12 a and the second magnetic sensor 12 b are arranged such that an output signal having a reverse phase is output by an induced magnetic field from a current flowing through the current line 11. For example, in FIG. 1, the current line 11 is sandwiched between the first magnetic sensor 12a and the second magnetic sensor 12b, and the sensitivity of the first magnetic sensor 12a and the second magnetic sensor 12b. The same direction (FIG. 1B) in the plane perpendicular to the direction in which the current line 11 extends (see FIG. 1B) so that the axis is in a direction perpendicular to the direction in which the current line 11 extends. (See the arrow 14a in FIG. 1). With such an arrangement, an output signal having a reverse phase due to the induced magnetic field from the current flowing through the current line 11 can be obtained, so that the influence of the disturbance magnetic field by the differential operation can be easily canceled. Here, the “reverse phase output signal” means an output signal in which the positive and negative voltages are reversed except for noise components. However, since it is sufficient if the relationship is such that current measurement can be performed with a desired accuracy, it is not required that the voltage value be strictly reversed in polarity.

Also, the first magnetic sensor 12a and the second magnetic sensor 12b are arranged so that the influence of the induced magnetic field from the current flowing through the adjacent current line 21 is reduced. More specifically, the insensitive axes of the first magnetic sensor 12a and the second magnetic sensor 12b are directed to the direction of the induced magnetic field from the current flowing through the adjacent current line (see arrow 14c in FIG. 1). Or the direction perpendicular to the sensitivity axes of the first magnetic sensor 12a and the second magnetic sensor 12b and having sensitivity coincides with the direction in which the adjacent current line extends (arrow in FIG. 1). 14b), the first magnetic sensor 12a and the second magnetic sensor 12b are arranged. The insensitive axis here does not require that the sensitivity be strictly zero.

For example, in FIG. 1, the magnetic sensor 12 a and the magnetic sensor 12 b have an induced magnetic field 31 from a current flowing through the adjacent current line 21 in the direction of the sensitivity axis and the direction perpendicular to the sensitivity axis and having sensitivity. They are arranged so as not to coincide with the direction (see FIG. 1B). The insensitive axis is oriented in a direction perpendicular to the current line 11 and the adjacent current line 13 (in a direction perpendicular to the plane 32 including the current line 11 and the adjacent current line 13 (see FIG. 1A)). It may be said that it is arranged. If the direction of the sensitivity axis or the direction perpendicular to the sensitivity axis and having sensitivity matches the direction of the induced magnetic field 31 from the current flowing through the adjacent current line 21, the current flows through the adjacent current line 21. This is because the current measurement accuracy is degraded under the influence of the induced magnetic field from the current to be generated.

Further, the magnetic sensor 12a and the magnetic sensor 12b are arranged so that the direction perpendicular to the sensitivity axis and having sensitivity coincides with the direction of the current flowing through the adjacent current line 21. Since the direction in which the current line 11 extends and the direction in which the adjacent current line 21 adjacent to the current line 11 extend are the same, the direction perpendicular to the sensitivity axis and having sensitivity is the current line 11. It can also be said that they are arranged so as to coincide with the direction of the current flowing therethrough. When the direction that is orthogonal to the sensitivity axis and has sensitivity matches the direction of the current that flows through the adjacent current line 21, at least in the above direction, the current that flows through the adjacent current line 21 This is because there is no need to be affected by the induced magnetic field, and the decrease in accuracy of current measurement can be suppressed.

When the circuit board 15 is arranged in a plane perpendicular to the current line 11 in relation to the circuit board 15 on which the magnetic sensor 12a and the magnetic sensor 12b are mounted, the direction of the sensitivity axis and the insensitive axis It can also be said that the direction coincides with one of the directions parallel to the main surface of the circuit board 15. In some cases, such an arrangement can save space.

With the configuration as described above, for example, the influence of the induced magnetic field from the current flowing through the adjacent current line 21 can be reduced as compared with the current sensor 2 shown in FIG. That is, a decrease in current measurement accuracy can be suppressed. Note that the current sensor 2 shown in FIG. 2 includes a current line 11 through which a current to be measured flows and a first magnetic sensor 12a and a second magnetic sensor 12b arranged around the current line 11. 1 is common to the current sensor 1 shown in FIG. On the other hand, in the current sensor 2, the direction (indicated by the arrow 14b) perpendicular to the sensitivity axes of the first magnetic sensor 12a and the second magnetic sensor 12b and having sensitivity passes through the adjacent current line 21. It differs from the current sensor 1 in that it is arranged so as to coincide with the direction 31 of the induced magnetic field from the flowing current.

The configuration shown in FIG. 2 is adopted because it is advantageous when the magnetic sensor 12a and the magnetic sensor 12b are mounted on the circuit board 15. In the current sensor 2 having such a configuration, the adjacent current line 21 is connected. Under the influence of the induced magnetic field from the flowing current, the current measurement accuracy decreases. Therefore, in the current sensor 1 according to the present embodiment, the insensitive axes of the magnetic sensor 12a and the magnetic sensor 12b are directed to the direction of the induced magnetic field from the current flowing through the adjacent current line. Or the direction perpendicular to the sensitivity axis of the magnetic sensor 12a and the magnetic sensor 12b and having the sensitivity coincides with the direction in which the adjacent current line extends, and the magnetic sensor 12a and the magnetic sensor 12b. By sufficiently arranging, the influence of the induced magnetic field from the current flowing through the adjacent current line is sufficiently reduced, and the decrease in current measurement accuracy is effectively suppressed.

In the present embodiment, it is assumed that there is one adjacent current line 21, but a plurality of adjacent current lines 21 may exist. When there are a plurality of adjacent current lines 21, the first magnetic sensor 12 a and the second magnetic sensor 12 a and the second magnetic sensor 12 a are reduced so that the influence of the combined magnetic field obtained by combining the induced magnetic fields from the currents flowing through the adjacent current lines 21 is reduced. The magnetic sensor 12b may be disposed. For example, as shown in FIG. 3, when a first adjacent current line 21a and a second adjacent current line 21b exist, it is considered that a magnetic sensor is disposed at a point A. In this case, the magnetic sensor is magnetically oriented such that the insensitive axis of the magnetic sensor faces the direction of the combined magnetic field 23 of the induced magnetic field 22a by the first adjacent current line 21a and the induced magnetic field 22b by the second adjacent current line 21b. What is necessary is just to arrange | position a sensor. Alternatively, in the induced magnetic field from the current flowing through the adjacent current line 21 in consideration of the magnitude of the current flowing through each adjacent current line 21 and the distance between the current line 11 and each adjacent current line 21. You may arrange | position the 1st magnetic sensor 12a and the 2nd magnetic sensor 12b so that the influence of the largest may be reduced. For example, the insensitive axes of the first magnetic sensor 12a and the second magnetic sensor 12b are directed to the direction of the maximum of the induced magnetic fields from the currents flowing through the plurality of adjacent current lines. One magnetic sensor 12a and second magnetic sensor 12b can be arranged. In any case, a decrease in current measurement accuracy can be effectively suppressed by making the direction of the insensitive axis coincide with the direction of the magnetic field that is likely to adversely affect the current measurement.

FIG. 4 shows a block diagram relating to the circuit configuration of the current sensor 1. As shown in FIG. 4, the current sensor 1 has an arithmetic device 13 connected to the output terminals of the first magnetic sensor 12 a and the second magnetic sensor 12 b. Here, the arithmetic device 13 has at least a function of differentially calculating the output signals of the first magnetic sensor 12a and the second magnetic sensor 12b. As a result, when a current flows through the current line 11 and an induced magnetic field is generated around the current line 11, an output signal corresponding to the current is output from the first magnetic sensor 12a and the second magnetic sensor 12b. Receiving the output signal, the arithmetic unit 13 can calculate and output the difference between the two output signals. Then, by taking the difference between the two output signals, the influence of the disturbance magnetic field can be canceled and the current measurement accuracy can be improved. Note that the function of the arithmetic device 13 may be realized by hardware or software.

Note that the cancellation of the influence of the disturbance magnetic field is realized by the following principle. First, the output of the first magnetic sensor 12a caused only by the magnetic flux φ when the magnetic flux φ is generated around the current line by the current i flowing through the current line 11 is defined as O ₁ . Since the first magnetic sensor 12a and the second magnetic sensor 12b are arranged so that output signals of opposite phases are output, the output of the second magnetic sensor 12b caused only by the magnetic flux φ is − O ₁ . On the other hand, the output of the first magnetic sensor 12a according to a uniform magnetic field disturbance (noise) When N _1, the output of the second magnetic sensor 12b is likewise N _1. Therefore, the output of the first magnetic sensor 12a including the noise component is O ₁ + N ₁ , and the output of the second magnetic sensor 12b including the noise component is −O ₁ + N ₁ . Since the difference between the outputs of the two magnetic sensors is (O ₁ + N ₁ ) − (− O ₁ + N ₁ ) = 2 · O ₁ , it is uniform by taking the differential value of the outputs of the two magnetic sensors. Noise components due to the disturbance magnetic field are removed.

FIG. 5 shows an example of the film configuration of the GMR element used for the first magnetic sensor 12a and the second magnetic sensor 12b. As shown in FIG. 5, the GMR element has a laminated structure of a plurality of films provided on the substrate 101. That is, the GMR element includes a seed layer 102, a first ferromagnetic film 103, an antiparallel coupling film 104, a second ferromagnetic film 105, a nonmagnetic intermediate layer 106, a soft magnetic free layer (free magnetic layer) 107, and A protective layer 108 is included. In FIG. 5, for simplicity of explanation, a base layer other than the GMR element is omitted, but, for example, Ta, Hf, Nb, Zr, and the like are interposed between the substrate 101 and the seed layer 102. An underlayer composed of a nonmagnetic material containing at least one element of Ti, Mo, W, or the like may be provided.

The seed layer 102 is made of NiFeCr or Cr. The first ferromagnetic film 103 is preferably made of a CoFe alloy containing 40 atomic% to 80 atomic% of Fe. This is because a CoFe alloy having this composition range has a large coercive force and can stably maintain magnetization with respect to an external magnetic field. The antiparallel coupling film 104 of the ferromagnetic fixed layer is made of Ru or the like. The second ferromagnetic film 105 is preferably made of a CoFe alloy containing 0 atomic% to 40 atomic% of Fe. This is because a CoFe alloy having this composition range has a small coercive force, and is easily magnetized in an antiparallel direction (direction different by 180 °) with respect to the direction in which the first ferromagnetic film 103 is preferentially magnetized. is there. The nonmagnetic intermediate layer 106 is made of Cu or the like. The soft magnetic free layer (free layer) 107 is made of a magnetic material such as a CoFe alloy, a NiFe alloy, or a CoFeNi alloy. The soft magnetic free layer 107 is preferably applied with a magnetic field in the longitudinal direction of the meander-shaped stripe during the film formation, and induced magnetic anisotropy is imparted to the soft magnetic free layer 107 after the film formation. Thereby, in the magnetoresistive effect element, the resistance is linearly changed with respect to the external magnetic field in the stripe width direction, and the hysteresis can be reduced. The protective layer 108 is made of Ta, Ru, or the like.

The GMR element as described above has sensitivity in a direction parallel to the film constituting the laminated structure. That is, the direction of the sensitivity axis and the direction orthogonal to the sensitivity axis and having sensitivity coincide with either the direction parallel to the main surface of the substrate 101 provided with the GMR element. On the other hand, there is no substantial sensitivity in the direction perpendicular to the film. That is, the direction of the insensitive axis coincides with the direction perpendicular to the main surface of the substrate 101. For example, in FIG. 5, the X-axis direction is the direction of the sensitivity axis, the Y-axis direction is the direction perpendicular to the sensitivity axis and having sensitivity, and the Z-axis direction is the direction of the insensitive axis. In consideration of this, the magnetic sensor 12a and the magnetic sensor 12b include a direction parallel to the direction in which the current line 11 or the adjacent current line 21 extends (that is, the direction in which the current flows), the magnetic sensor 12a, and the magnetic sensor. It can also be said that the direction parallel to the main surface 101 of the substrate on which the GMR element is formed in 12b coincides.

Since the magnetic sensor using the GMR element described above has a small size in the direction perpendicular to the main surface of the substrate 101, the configuration shown in FIG. 1 is adopted to save the space of the current sensor. There is also an advantage of being able to.

(Embodiment 2)
In the present embodiment, another example of the current sensor 1 of the present invention will be described. FIG. 6 is a schematic diagram showing the current sensor 1 of the present embodiment. FIG. 6A is a perspective view schematically showing the configuration of the current sensor 1 and its periphery, and FIG. 6B is a plan view of the current sensor 1 as viewed from the direction in which adjacent current lines extend. In FIG. 6A, the solid arrow given to the current line 11 indicates that the direction of the current flowing through the current line 11 is upward, and the solid arrow given to the adjacent current line 21 is This indicates that the direction of the current flowing through is downward left on the page. That is, here, the direction of the current to be measured and the direction of the adjacent current are orthogonal. In FIGS. 6A and 6B, a long solid arrow 14a, a short solid arrow 14b, and a broken arrow 14c applied to the first magnetic sensor 12a and the second magnetic sensor 12b are , The direction of the sensitivity axis, the direction perpendicular to the sensitivity axis and having sensitivity, and the direction of the insensitive axis, respectively. For example, two long and short solid arrows and a dashed arrow attached to the first magnetic sensor 12a indicate that the direction of the sensitivity axis of the first magnetic sensor 12a is the upper right direction in FIG. 6A (long arrow). 14a), the sensitivity is also upward in FIG. 6A (short arrow 14b), and the insensitive axis is rightward in FIG. 6A (dashed arrow 14c). In FIG. 6B, the solid arrow given to the current line 11 indicates that the direction of the current flowing through the current line 11 is upward, and the mark given to the adjacent current line 21 is Indicates that current flows forward.

In addition, the direction of the current flowing through the current line 11 and the adjacent current line 21 and the direction of the sensitivity axis of the magnetic sensor may be reversed. Since FIG. 6 is a schematic diagram, the size, quantity, arrangement, and the like of each component can be changed as appropriate. In addition, FIG. 6 is a diagram for easy understanding of the feature points of the present embodiment, and therefore, part of the configuration of the current sensor 1 may be omitted in FIG. 6.

As shown in FIG. 6, the current sensor 1 includes a current line 11 through which a current to be measured flows, and a first magnetic sensor 12 a and a second magnetic sensor 12 b arranged around the current line 11. In addition, the current sensor 1 includes an arithmetic device (not shown) that differentially calculates the output signals of the first magnetic sensor 12a and the second magnetic sensor 12b.

The first magnetic sensor 12a and the second magnetic sensor 12b are preferably a magnetic proportional sensor or a magnetic balanced sensor. Further, as the magnetoresistive effect element, a GMR element having sensitivity also in the direction orthogonal to the sensitivity axis is used. The magnetoresistive element is not limited to a GMR element as long as it has sensitivity in a direction orthogonal to the sensitivity axis. For details, the description of Embodiment Mode 1 can be referred to, and thus the description thereof is omitted here.

In the current sensor 1, the first magnetic sensor 12 a and the second magnetic sensor 12 b are arranged such that an output signal having a reverse phase is output by an induced magnetic field from a current flowing through the current line 11. For example, in FIG. 6, the current line 11 is sandwiched between the first magnetic sensor 12a and the second magnetic sensor 12b, and the sensitivity of the first magnetic sensor 12a and the second magnetic sensor 12b. The axes are respectively arranged so as to face the direction perpendicular to the direction in which the current line 11 extends (see arrow 14a in FIG. 6). With such an arrangement, an output signal having a reverse phase due to the induced magnetic field from the current flowing through the current line 11 can be obtained, so that the influence of the disturbance magnetic field by the differential operation can be easily canceled.

Also, the first magnetic sensor 12a and the second magnetic sensor 12b are arranged so that the influence of the induced magnetic field from the current flowing through the adjacent current line 21 is reduced. More specifically, the insensitive axes of the first magnetic sensor 12a and the second magnetic sensor 12b are directed to the direction of the induced magnetic field from the current flowing through the adjacent current line (see arrow 14c in FIG. 6). The direction perpendicular to the sensitivity axis of the first magnetic sensor 12a and having sensitivity is opposite to the direction perpendicular to the sensitivity axis of the second magnetic sensor 12b and having sensitivity. (Refer to arrow 14b in FIG. 6), the first magnetic sensor 12a and the second magnetic sensor 12b are arranged.

For example, in FIG. 6, the first magnetic sensor 12 a and the second magnetic sensor 12 b pass through the adjacent current line 21 in the direction of the sensitivity axis and the direction perpendicular to the sensitivity axis and having sensitivity. It arrange | positions so that it may not correspond with the direction of the induction magnetic field 31 (refer FIG.6 (B)) from an electric current. If the direction of the sensitivity axis or the direction perpendicular to the sensitivity axis and having sensitivity matches the direction of the induced magnetic field 31 from the current flowing through the adjacent current line 21, the current flows through the adjacent current line 21. This is because the current measurement accuracy is degraded under the influence of the induced magnetic field from the current to be generated.

In the present embodiment, the first magnetic sensor 12a and the second magnetic sensor 12b have a direction that is perpendicular to the sensitivity axis and has sensitivity, and the direction of the current flowing through the adjacent current line 21 Is not parallel to (for example, orthogonal). In this case, it is affected by the induced magnetic field from the current flowing through the adjacent current line 21, but the components in the direction of the arrow 14b of the induced magnetic field 31 are the first magnetic sensor 12a and the second magnetic field. When the effect is reversed in the first magnetic sensor 12a and the second magnetic sensor 12b (see FIG. 5B) due to the reverse direction in the sensor 12b (see FIG. 5B), the first magnetic sensor 12a The adjacent current line 21 is arranged by arranging the direction perpendicular to the sensitivity axis and having sensitivity and the direction perpendicular to the sensitivity axis of the second magnetic sensor 12b and having sensitivity to each other in the opposite directions. The influence of the induced magnetic field from the flowing current can be canceled by differential calculation, and the decrease in current measurement accuracy can be suppressed.

From this point of view, in the current sensor of the present embodiment, the direction perpendicular to the sensitivity axis and having sensitivity is the sensitivity axis of the induced magnetic field 31 from the current flowing through the adjacent current line 21. It is possible to express that the component in the direction perpendicular to the direction and having sensitivity (the component in the direction of arrow 14b) is arranged so as to be canceled by the differential calculation. For example, the induced magnetic field 31 in FIG. 6B has a component upward in the drawing in the vicinity of the first magnetic sensor 12a, and has a component in the downward direction in the vicinity of the second magnetic sensor 12b. In this situation, the direction of the first magnetic sensor 12a and the second magnetic sensor 12b that is perpendicular to the sensitivity axis and has sensitivity (the direction of the arrow 14b) is the same direction as the component of the induction magnetic field 31 described above. The influence of the induction magnetic field 31 appears in the same phase in the first magnetic sensor 12a and the second magnetic sensor 12b, and cancellation by differential calculation becomes possible.

In the present embodiment, it is assumed that there is one adjacent current line 21, but a plurality of adjacent current lines 21 may exist. When there are a plurality of adjacent current lines 21, the first magnetic sensor 12 a and the second magnetic sensor 12 a and the second magnetic sensor 12 a are reduced so that the influence of the combined magnetic field obtained by combining the induced magnetic fields from the currents flowing through the adjacent current lines 21 is reduced. The magnetic sensor 12b may be disposed. For example, as shown in FIG. 3, in the case where the first adjacent current line 21a and the second adjacent current line 21b exist, if the magnetic sensor is arranged at the point A, the insensitive axis of the magnetic sensor is The magnetic sensor may be arranged so as to face the direction of the combined magnetic field 23 of the induced magnetic field 22a by the first adjacent current line 21a and the induced magnetic field 22b by the second adjacent current line 21b. Alternatively, in the induced magnetic field from the current flowing through the adjacent current line 21 in consideration of the magnitude of the current flowing through each adjacent current line 21 and the distance between the current line 11 and each adjacent current line 21. You may arrange | position the 1st magnetic sensor 12a and the 2nd magnetic sensor 12b so that the influence of the largest may be reduced. For example, the insensitive axes of the first magnetic sensor 12a and the second magnetic sensor 12b are directed to the direction of the maximum of the induced magnetic fields from the currents flowing through the plurality of adjacent current lines. One magnetic sensor 12a and second magnetic sensor 12b can be arranged. In any case, a decrease in current measurement accuracy can be effectively suppressed by making the direction of the insensitive axis coincide with the direction of the magnetic field that is likely to adversely affect the current measurement.

The circuit configuration of the current sensor 1 and the structure of the GMR element are the same as those in the first embodiment. For details, the description of Embodiment Mode 1, FIG. 4 and FIG.

As described above, the direction of the first magnetic sensor 12a and the second magnetic sensor 12b that is perpendicular to the sensitivity axis and has sensitivity is parallel to the direction of the current flowing through the adjacent current line 21. In the case where the influence of the induced magnetic field from the current flowing through the adjacent current line is reversed in the first magnetic sensor 12a and the second magnetic sensor 12b, the first magnetic sensor 12a By arranging the direction that is perpendicular to the sensitivity axis and has sensitivity and the direction that is perpendicular to the sensitivity axis of the second magnetic sensor 12b and has sensitivity, the current measurement accuracy is reversed. It may be possible to suppress the decrease in. The above arrangement can be applied without any problem even when the direction that is perpendicular to the sensitivity axis and has sensitivity and the direction of the current flowing through the adjacent current line 21 are in a parallel relationship. In this case, the direction that is perpendicular to the sensitivity axes of the first magnetic sensor 12a and the second magnetic sensor 12b and has sensitivity is directed in a direction parallel to the current flowing through the adjacent current line 21 (adjacent current). And the direction perpendicular to the sensitivity axis of the first magnetic sensor 12a and having sensitivity, and the direction perpendicular to the sensitivity axis of the second magnetic sensor 12b and sensitivity. What is necessary is just to arrange | position so that it may become a reverse direction.

(Embodiment 3)
In the present embodiment, another example of the current sensor 1 of the present invention will be described. FIG. 7 is a schematic diagram showing an example of the current sensor 1 of the present embodiment. FIG. 7A is a perspective view schematically showing the configuration of the current sensor 1 and its periphery, and FIG. 7B is a plan view of the current sensor 1 as viewed from the direction in which adjacent current lines extend. In FIG. 7A, the solid line arrow given to the current line 11 indicates that the direction of the current flowing through the current line 11 is upward, and the solid line arrow given to the adjacent current line 21 is This indicates that the direction of the current flowing through is downward left on the page. That is, here, the direction of the current to be measured and the direction of the adjacent current are orthogonal. 7A and 7B, a long solid arrow 14a, a short solid arrow 14b, and a broken arrow 14c applied to the first magnetic sensor 12a and the second magnetic sensor 12b are , The direction of the sensitivity axis, the direction perpendicular to the sensitivity axis and having sensitivity, and the direction of the insensitive axis, respectively. For example, two long and short solid arrows and a broken arrow attached to the first magnetic sensor 12a indicate that the direction of the sensitivity axis of the first magnetic sensor 12a is the upper right direction in FIG. 7A (long arrow). 14a), the sensitivity is also upward in FIG. 7A (short arrow 14b), indicating that the insensitive axis is rightward in FIG. 7A (dashed arrow 14c). In FIG. 7B, the solid arrow given to the current line 11 indicates that the direction of the current flowing through the current line 11 is upward, and the mark given to the adjacent current line 21 is Indicates that current flows forward.

FIG. 8 is a schematic diagram showing another example of the current sensor 1 of the present embodiment. FIG. 8A is a perspective view schematically showing the configuration of the current sensor 1 and its periphery, and FIG. 8B is a plan view of the current sensor 1 as viewed from the direction in which adjacent current lines extend. In FIG. 8A, the solid line arrow given to the current line 11 indicates that the direction of the current flowing through the current line 11 is upward, and the solid line arrow given to the adjacent current line 21 is Indicates that the direction of the current flowing through is rightward on the page. That is, here, the direction of the current to be measured and the direction of the adjacent current are orthogonal. 8A and 8B, a long solid arrow 14a, a short solid arrow 14b, and a broken arrow 14c applied to the first magnetic sensor 12a and the second magnetic sensor 12b are , The direction of the sensitivity axis, the direction perpendicular to the sensitivity axis and having sensitivity, and the direction of the insensitive axis, respectively. For example, two long and short solid arrows and a dashed arrow attached to the first magnetic sensor 12a indicate that the direction of the sensitivity axis of the first magnetic sensor 12a is the upper right direction in FIG. 8A (long arrow). 14a), the sensitivity is also upward in FIG. 8A (short arrow 14b), and the insensitive axis is the right direction in FIG. 8A (dashed arrow 14c). In FIG. 8B, the solid arrow given to the current line 11 indicates that the direction of the current flowing through the current line 11 is upward, and the mark given to the adjacent current line 21 is Indicates that current flows forward.

In addition, the direction of the current flowing through the current line 11 and the adjacent current line 21 and the direction of the sensitivity axis of the magnetic sensor may be reversed. Moreover, since FIG.7 and FIG.8 is a schematic diagram, the magnitude | size, quantity, arrangement | positioning, etc. of each structure can be changed suitably. Moreover, since FIG.7 and FIG.8 is a figure for showing the feature point of this Embodiment intelligibly, a part of structure of the current sensor 1 may be abbreviate | omitted.

As shown in FIGS. 7 and 8, the current sensor 1 includes a current line 11 through which a current to be measured flows, and a first magnetic sensor 12a and a second magnetic sensor 12b arranged around the current line 11. Including. In addition, the current sensor 1 includes an arithmetic device (not shown) that differentially calculates the output signals of the first magnetic sensor 12a and the second magnetic sensor 12b.

In the current sensor 1, the first magnetic sensor 12 a and the second magnetic sensor 12 b are arranged such that an output signal having a reverse phase is output by an induced magnetic field from a current flowing through the current line 11. For example, in FIGS. 7 and 8, the current line 11 is sandwiched between the first magnetic sensor 12a and the second magnetic sensor 12b, and the first magnetic sensor 12a and the second magnetic sensor. The sensitivity axes of 12b are arranged so as to face the direction perpendicular to the direction in which the current line 11 extends (see the arrow 14a in FIGS. 7 and 8). With such an arrangement, an output signal having a reverse phase due to the induced magnetic field from the current flowing through the current line 11 can be obtained, so that the influence of the disturbance magnetic field by the differential operation can be easily canceled.

Also, the first magnetic sensor 12a and the second magnetic sensor 12b are arranged so that the influence of the induced magnetic field from the current flowing through the adjacent current line 21 is reduced. More specifically, the direction that is perpendicular to the sensitivity axes of the first magnetic sensor 12a and the second magnetic sensor 12b and has sensitivity is directed to the direction of the induced magnetic field from the current flowing through the adjacent current line. In the case (in the case of FIG. 7), or the sensitivity axes of the first magnetic sensor 12a and the second magnetic sensor 12b are directed in the direction of the induced magnetic field from the current flowing through the adjacent current line (in the case of FIG. 8). In the case where the influence of the induced magnetic field from the current flowing through the adjacent current line appears similarly in the first magnetic sensor 12a and the second magnetic sensor 12b, the sensitivity of the first magnetic sensor 12a The direction that is orthogonal to the axis and has sensitivity, and the direction that is orthogonal to the sensitivity axis of the second magnetic sensor 12b and has sensitivity have the same direction (see FIGS. 7 and 8). Arrow 14b), first magnetic sensor 12a and the second magnetic sensor 12b is disposed.

The configuration of the current sensor according to the present embodiment is such that the direction that is perpendicular to the sensitivity axis and has sensitivity is the direction that the induced magnetic field 31 from the current flowing through the adjacent current line 21 is perpendicular to the sensitivity axis. However, it may be expressed that the component in the direction having sensitivity (the component in the direction of the arrow 14b) is arranged so as to be canceled by the differential calculation. For example, the induction magnetic field 31 in FIG. 7B has a downward component in the drawing in the vicinity of the first magnetic sensor 12a, and has a downward component in the drawing in the vicinity of the second magnetic sensor 12b. In this situation, the direction of the first magnetic sensor 12a and the second magnetic sensor 12b that is perpendicular to the sensitivity axis and has sensitivity (the direction of the arrow 14b) is the same direction as the component of the induction magnetic field 31 described above. The influence of the induction magnetic field 31 appears in the same phase in the first magnetic sensor 12a and the second magnetic sensor 12b, and cancellation by differential calculation becomes possible.

By adopting such an arrangement, it is possible to cancel the influence of the induced magnetic field from the current flowing through the adjacent current line 21 by differential calculation, and to suppress a decrease in current measurement accuracy.

As described above, when the insensitive axes of the first magnetic sensor 12a and the second magnetic sensor 12b cannot be arranged so as to face the direction of the induced magnetic field from the current flowing through the adjacent current line 21, When the influence of the induced magnetic field from the current flowing through the adjacent current line 21 appears similarly in the first magnetic sensor 12a and the second magnetic sensor 12b, it is orthogonal to the sensitivity axis of the first magnetic sensor 12a. The direction that is the direction and having the sensitivity and the direction that is perpendicular to the sensitivity axis of the second magnetic sensor 12b and that has the sensitivity are directed in the same direction, so that the current flowing through the adjacent current line 21 can be The influence of the induced magnetic field can be canceled by differential calculation, and a decrease in current measurement accuracy can be suppressed.

The current measurement accuracy in the current sensor 1 of the first embodiment was confirmed. As the measurement system, the current sensor 1 having the configuration shown in FIG. 1 was used. In addition, the cross section of the current line 11 and the adjacent current line 21 is a rectangular shape of 10 mm × 2 mm (see FIG. 9). The evaluation of the current measurement accuracy is based on the measurement result obtained in the state where current is not passed through the adjacent current line 21 as the reference value, and the measurement result obtained when current is passed through the adjacent current line 21 and the reference value. Was measured using the measurement error e (%) expressed as a percentage of the reference value and the center-to-center distance d (mm) between the current line 11 and the adjacent current line 21.

(Comparative example)
The current measurement accuracy in the current sensor 2 was confirmed under the same conditions as in the above example. The measurement system is the current sensor 2 having the configuration shown in FIG. Similarly, the cross sections of the current line 11 and the adjacent current line 21 have a rectangular shape of 10 mm × 2 mm.

The evaluation results of Examples and Comparative Examples are shown in FIG. In FIG. 10, the vertical axis represents the measurement error e (%), and the horizontal axis represents the center distance d (mm). As can be seen from FIG. 10, in the configuration of the example, that is, the current sensor 1, the measurement error is suppressed to less than 1% even when the distance between the centers is as close as about 40 mm. That is, a decrease in current measurement accuracy is suppressed. On the other hand, in the configuration of the comparative example, that is, the current sensor 2, the measurement error is close to 4% when the distance between the centers is close to about 40 mm. It can be seen that in order to achieve a measurement error of less than 1% in the current sensor 2, the center-to-center distance needs to be about 80 mm.

As described above, in the current sensor 2, the measurement accuracy decreases when the distance between the current sensor 2 and the adjacent current line 21 is small. Therefore, in order to ensure the measurement accuracy of the current sensor 2, The system including the current line 21 needs to be enlarged to some extent. On the other hand, in the current sensor 1 of the first embodiment, it is easy to ensure current measurement accuracy even when the distance between the current sensor 1 and the adjacent current line 21 is small. That is, there is an advantage that the system including the current sensor 1 and the adjacent current line 21 can be easily downsized. For example, when a measurement error of 1% is allowed in the above-described configuration, the system including the current sensor 1 and the adjacent current line 21 is simply calculated as compared with the system including the current sensor 2 and the adjacent current line 21. Therefore, it is possible to reduce the size and space by 40 mm.

As described above, the current sensor of the present invention sufficiently reduces the influence of the induced magnetic field from the current flowing through the adjacent current line by devising the arrangement of the magnetic sensor having sensitivity in the direction orthogonal to the sensitivity axis. is doing. For this reason, when such a magnetic sensor is used, the fall of the current measurement precision by the influence of the electric current which flows through an adjacent current line can be suppressed. This also makes it possible to reduce the size and space of the system including the current sensor.

Note that the present invention is not limited to the above embodiment, and can be implemented with various modifications. For example, the connection relationship, size, and the like of each element in the above embodiment can be changed as appropriate. Further, the structures shown in Embodiments 1 to 3 can be implemented in appropriate combination. In addition, the present invention can be implemented with appropriate modifications without departing from the scope of the present invention.

The current sensor of the present invention can be used, for example, to detect the magnitude of a current for driving a motor of an electric vehicle or a hybrid car.

This application is based on Japanese Patent Application No. 2010-209430 filed on Sep. 17, 2010. All this content is included here.

Claims

A pair of sensitivities that are arranged around the current line through which the current to be measured flows, and that output an output signal having a reverse phase by an induced magnetic field from the current flowing through the current line, each having sensitivity in a direction orthogonal to the sensitivity axis A magnetic sensor;
An arithmetic device connected to the pair of magnetic sensors and differentially calculating output signals of the pair of magnetic sensors;
Comprising
The current sensor, wherein the insensitive axis is arranged so as to face the direction of the induced magnetic field from the current flowing through the current line adjacent to the current line.
The current sensor according to claim 1, wherein the magnetic sensor is arranged so that a direction perpendicular to the sensitivity axis and having sensitivity coincides with a direction in which the current line extends. .
3. The current sensor according to claim 1, wherein the pair of magnetic sensors are arranged such that directions that are perpendicular to the sensitivity axis and have sensitivity are opposite to each other. 4. .
The current sensor according to any one of claims 1 to 3, wherein the magnetic sensor includes a GMR element.
The direction of the sensitivity axis and the direction perpendicular to the sensitivity axis and having sensitivity coincide with one of the directions parallel to the main surface of the substrate on which the GMR element is provided, and the direction of the insensitive axis is The current sensor according to claim 4, wherein the current sensor coincides with a direction perpendicular to the main surface of the substrate.
A pair of magnetic sensors are mounted and a circuit board is disposed in a plane perpendicular to the current line;
6. The current according to claim 1, wherein a direction of the sensitivity axis and a direction of the insensitivity axis coincide with any one of directions parallel to the main surface of the circuit board. Sensor.