JP2015036636A - Current sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current sensor capable of suppressing deterioration of measurement accuracy due to an external magnetic field when measuring current flowing through a U-shaped bus bar.SOLUTION: A current sensor (10) comprises: a U-shaped bus bar (21) including a first conductive part (22), a second conductive part (23) and a third conductive part (24); and a first magnetoresistance effect element (31) and a second magnetoresistance effect element (32) arranged between the first conductive part and the second conductive part. The first magnetoresistance effect element and the second magnetoresistance effect element each have a main sensitivity axis and a sub-sensitivity axis orthogonal to the main sensitivity axis. Directions (31a, 32a) of the main sensitivity axes of the first magnetoresistance effect element (31) and the second magnetoresistance effect element (32) are set to be in parallel to each other, and directions (31b, 32b) of the sub-sensitivity axes of the first magnetoresistance effect element (31) and the second magnetoresistance effect element (32) are set to be reversed to each other.

Description

  The present invention relates to a current sensor, and more particularly to a current sensor that can suppress a decrease in measurement accuracy caused by an external magnetic field.

  In order to control and monitor various electronic devices, a current sensor that measures a current flowing through a bus bar (current path to be measured) is used. As such a current sensor, one using a magnetic sensor element that detects a magnetic field generated around a current is known. Patent Document 1 below discloses a current sensor using a Hall element or a magnetoresistive effect element as a magnetic sensor element.

  FIG. 11 is a perspective view of a current sensor 101 of a first conventional example described in Patent Document 1. As shown in FIG. As shown in FIG. 11, the current sensor 101 of the first conventional example includes a bus bar 102, a magnetic sensor 107 for detecting the strength of a magnetic field 126 generated by a current 104 flowing through the bus bar 102, and a magnetic sensor for changing a magnetic path. Road change units 160 and 161.

  The bus bar 102 includes a concave portion 120 provided in a U-shape, and attachment portions 124 attached to both ends of the concave portion 120. The concave portion 120 includes parallel portions 121 and 123 and a vertical portion 122, and a magnetic field 126 in the same direction is formed in the concave portion 120 by the current 104 flowing through the concave portion 120.

  As shown in FIG. 11, the magnetic sensor 107 and the magnetic path changing units 160 and 161 are provided in the recess 120. The magnetic path changing portions 160 and 161 are formed of a soft magnetic material such as permalloy, and the magnetic field 126 in the concave portion 120 is collected by the magnetic path changing portion 160 and penetrates the magnetic sensitive surface of the magnetic sensor 107, so that the magnetic path Exit from the changing unit 161. Thereby, the magnetic field 126 generated by the current flowing through the recess 120 can be effectively concentrated on the magnetic sensor 107, and the current 104 can be measured.

  In the current sensor 101 of the first conventional example shown in FIG. 11, a Hall element is used as the magnetic sensor 107. However, it is also possible to arrange the magnetoresistive effect element by changing the direction of arrangement by 90 °. It is.

JP 2010-44019 A International Publication No. 2012/120939

  However, in the current sensor 101 of the first conventional example, the influence of an external magnetic field from an adjacent current path or the like cannot be sufficiently suppressed, resulting in a problem that measurement accuracy is lowered.

  Patent Document 2 discloses a current sensor configured using a magnetoresistive element as a magnetic sensor. FIG. 12 is a schematic diagram for explaining the problem of the current sensor 201 of the second conventional example described in Patent Document 2. In FIG.

  As shown in FIG. 12, in the current sensor 201 of the second conventional example, two magnetic sensor elements 215a and 215b are provided with a measured current path (bus bar) 211 interposed therebetween. The magnetic sensor elements 215a and 215b are arranged so that the directions 216a and 216b of the sensitivity axes of the magnetic sensor elements 215a and 215b are parallel to the direction of the magnetic field 213 generated by the current 212 flowing through the measured current path (busbar) 211. The

  It is known that the magnetic sensor elements 215a and 215b have sensitivity in a direction (hereinafter, sub-sensitivity axis direction) orthogonal to the sensitivity axis directions 216a, 216b (hereinafter, main sensitivity axis direction). Therefore, when the adjacent current path 221 is provided adjacent to the current path to be measured (bus bar) 211, the measurement is performed by the components of the auxiliary sensitivity axis directions 217a and 217b of the induced magnetic field 223 from the current flowing through the adjacent current path 221. An error occurs. In the current sensor 201 of the second conventional example, by controlling the sub-sensitivity axis directions 217a and 217b of the two magnetic sensor elements 215a and 215b, the components 217a and 217b in the sub-sensitivity axis direction of the induced magnetic field 223 caused by the adjacent current 222 are controlled. Is canceled to prevent a decrease in measurement accuracy.

  However, the two magnetic sensor elements 215 a and 215 b are provided with a predetermined interval across the bus bar 211, and an external magnetic field is absorbed or reflected by the bus bar 211. For this reason, the components in the sub-sensitivity axis directions 217a and 217b of the external magnetic field passing through the magnetic sensor elements 215a and 215b have different angles and sizes, and may not be sufficiently canceled.

  For the bus bar 102 having the U-shaped concave portion 120 as shown in the current sensor 101 of the first conventional example, a method for suppressing a decrease in measurement accuracy due to an external magnetic field is disclosed in Patent Document 1 and Patent Document 2 described above. Is not listed.

  An object of the present invention is to solve the above-described problems and provide a current sensor capable of suppressing a decrease in measurement accuracy due to an external magnetic field when measuring a current flowing through a U-shaped bus bar.

  The current sensor according to the present invention includes a first conductive part and a second conductive part arranged at intervals, and a third conductive part that connects the first conductive part and the second conductive part. A U-shaped bus bar, a substrate disposed between the first conductive portion and the second conductive portion, a first magnetoresistance effect element and a second magnetoresistance mounted on the substrate Each of the first magnetoresistive effect element and the second magnetoresistive effect element includes a main sensitivity axis and a secondary sensitivity axis orthogonal to the main sensitivity axis. The directions of the main sensitivity axes of each of the magnetoresistive effect element and the second magnetoresistive effect element are provided in parallel to each other, and each of the first magnetoresistive effect element and the second magnetoresistive effect element is provided. The sub-sensitivity axes are provided in directions opposite to each other. That.

  According to this, since the first magnetoresistive element and the second magnetoresistive element are provided on the same substrate between the first conductive part and the second conductive part, The external magnetic field passing through each of the magnetoresistive element and the second magnetoresistive element has the same magnitude and the same direction. Since the directions of the sub-sensitivity axes of the first magnetoresistive effect element and the second magnetoresistive effect element are opposite to each other, the components of the external magnetic field in the sub-sensitivity axis direction have the same magnitude. At the opposite direction. Therefore, by taking the sum of the outputs of the first magnetoresistive effect element and the second magnetoresistive effect element, the first magnetoresistive effect element and the second magnetoresistive effect due to the component in the sub-sensitivity axis direction of the external magnetic field. The measurement error of the element is canceled out.

  Therefore, according to the current sensor of the present invention, it is possible to suppress a decrease in measurement accuracy due to an external magnetic field when measuring the current flowing through the U-shaped bus bar.

  The substrate has a first surface facing the first conductive portion and a second surface facing the second conductive portion, and the first magnetoresistance effect element is the first surface. And the second magnetoresistive element is provided on the second surface, and the first magnetoresistive element and the second magnetoresistive element are provided facing each other. It is preferable that According to this, the first magnetoresistive effect element and the second magnetoresistive effect element are arranged at the overlapping position in the substrate surface and the interval is reduced, so that the first magnetoresistive effect element and the second magnetic resistance effect element are reduced. It is possible to further reduce the difference between the components of the external magnetic field passing through each of the resistance effect elements in the sub-sensitivity axis direction. Therefore, the measurement error due to the external magnetic field can be surely canceled, and the decrease in measurement accuracy due to the external magnetic field can be suppressed.

  Each of the first magnetoresistive element and the second magnetoresistive element includes a bias magnet that applies a bias magnetic field in a direction orthogonal to the main sensitivity axis, and the direction of the sub-sensitivity axis is the bias magnetic field. It is preferable that the direction is According to this, since the direction of the secondary sensitivity axis can be reliably controlled by providing the bias magnet, it is possible to realize a configuration capable of appropriately canceling the measurement error due to the component of the external magnetic field in the secondary sensitivity axis direction.

  The main sensitivity axis direction of each of the first magnetoresistive element and the second magnetoresistive element passes through the first conductive part, the second conductive part, and the third conductive part. It is preferable that a shield that is provided in a direction orthogonal to the virtual plane and that sandwiches the virtual plane in the main sensitivity axis direction is provided. According to this, since the external magnetic field which invades from the main sensitivity axis direction is shielded by the shield, it is possible to suppress a decrease in measurement accuracy.

  The directions of the main sensitivity axes of the first magnetoresistive element and the second magnetoresistive element are provided in the same direction, and the output of the first magnetoresistive element and the second magnetism It is preferable to have an arithmetic unit that takes the sum of the output of the resistive element. According to this, the error due to the component in the sub-sensitivity axis direction of the external magnetic field included in each of the output of the first magnetoresistive element and the output of the second magnetoresistive element is canceled, and the current sensor The decrease in measurement accuracy is suppressed.

  According to the current sensor of the present invention, it is possible to suppress a decrease in measurement accuracy due to an external magnetic field when measuring a current flowing through a U-shaped bus bar.

It is a perspective view when the current sensor in the 1st Embodiment of this invention is seen from the direction where the 1st magnetoresistive effect element is arrange | positioned. It is a perspective view when the current sensor in this embodiment is seen from the direction in which the second magnetoresistive element is arranged. FIG. 3 is a plan view of the current sensor when viewed from the Z1 direction in FIGS. 1 and 2. FIG. 3 is a front view of the current sensor when viewed from the X2 direction in FIGS. 1 and 2. It is sectional drawing of a current sensor when it cuts along the VV line | wire of FIG. 2, and it sees from the arrow direction. It is a model top view of the current sensor for demonstrating the external magnetic field which passes a magnetoresistive effect element. It is a block diagram which shows the circuit structural example of the current sensor of this embodiment. It is a top view of the current sensor of a 2nd embodiment. It is a front view (Drawing 9A) and a sectional view (Drawing 9B) of a current sensor of a 3rd embodiment. It is a schematic diagram which shows the magnetoresistive effect element which comprises the current sensor of 4th Embodiment. It is a perspective view of the current sensor of the 1st conventional example. It is a schematic diagram for demonstrating the subject of the current sensor of the 2nd prior art example.

  Hereinafter, specific embodiments of the current sensor of the present invention will be described with reference to the drawings. In addition, the dimension of each drawing is changed and shown suitably.

<First Embodiment>
FIG. 1 is a perspective view of the current sensor according to the first embodiment when viewed from the direction in which the first magnetoresistive element is disposed. FIG. 2 is a perspective view of the current sensor of the present embodiment as viewed from the direction in which the second magnetoresistive element is disposed. FIG. 3 is a plan view of the current sensor as viewed from the Z1 direction in FIGS. FIG. 4 is a front view of the current sensor when viewed from the X2 direction in FIGS. 1 and 2. FIG. 5 is a cross-sectional view of the current sensor as viewed from the direction of the arrow cut along the line VV in FIG.

  As shown in FIGS. 1 and 2, the current sensor 10 of the present embodiment includes a U-shaped bus bar 21, a substrate 30, a first magnetoresistive effect element 31 and a second magnetic element mounted on the substrate 30. A resistance effect element 32 is included.

  As shown in FIGS. 1 to 3, the bus bar 21 includes a first conductive portion 22, a second conductive portion 23, and a third conductive portion 24, and the first conductive portion 22 and the second conductive portion 24. The conductive portions 23 extend in the X1-X2 direction, and are arranged in parallel at intervals in the Y1-Y2 direction. The third conductive portion 24 extends in the Y1-Y2 direction, and connects the first conductive portion 22 and the second conductive portion 23. The bus bar 21 is configured in a U shape in plan view by connecting the first conductive portion 22, the second conductive portion 23, and the third conductive portion 24. As shown in FIGS. 4 and 5, the first conductive portion 22, the second conductive portion 23, and the third conductive portion 24 are formed in a rectangular cross section. The cross-sectional shape of each conductive portion may be other than a rectangle, and may be formed in an oval shape, a circular shape, or the like.

  The bus bar 21 is formed from a conductive material such as a metal material or an alloy material. When the current sensor 10 is used, the end portions in the X2 direction of the first conductive portion 22 and the second conductive portion 23 are connected to an external device (for example, an automobile motor or a battery) to be measured, A current to be measured 25 is continuously passed through the first conductive portion 22, the third conductive portion 24, and the second conductive portion 23 of the bus bar 21.

  As shown in FIGS. 1 to 3, the substrate 30 is disposed between the first conductive portion 22 and the second conductive portion 23. The substrate 30 is provided in parallel to the first conductive part 22 and the second conductive part 23 and orthogonal to the third conductive part 24, and the first conductive part 22 is opposed to the first conductive part 22. It has a surface 30 a and a second surface 30 b that faces the second conductive portion 23.

  In the current sensor 10 of the present embodiment, a printed wiring board (PWB, Printed Wiring Board) formed of a glass epoxy material or the like can be used as the substrate 30. Alternatively, a ceramic substrate such as an alumina substrate can be used.

  As shown in FIGS. 1 and 2, the first magnetoresistive element 31 is mounted on the first surface 30a of the substrate 30, and the second magnetoresistive element 32 is mounted on the second surface 30b. ing. The first magnetoresistive effect element 31 and the second magnetoresistive effect element 32 are arranged to face each other with the substrate 30 interposed therebetween. As shown in FIG. 3, in the plan view of the current sensor 10, the first magnetoresistive element 31 and the second magnetoresistive element 32 are disposed between the first conductive part 22 and the second conductive part 23. Has been placed. As shown in FIG. 4, when viewed from the front, it passes through the first conductive portion 22, the second conductive portion 23, and the third conductive portion 24, and is parallel to each conductive portion 22, 23, 24. When the virtual plane 37 is set, the first magnetoresistive element 31 and the second magnetoresistive element 32 are arranged so as to intersect the virtual plane 37. In other words, the first magnetoresistive effect element 31 and the second magnetoresistive effect element 32 are arranged at the same height as the first conductive portion 22 and the second conductive portion 23.

  In the present embodiment, a GMR (Giant Magneto Resistance) element is used as the first magnetoresistive effect element 31 and the second magnetoresistive effect element 32.

  The arrows 31a and 31b attached to the first magnetoresistive effect element 31 and the arrows 32a and 32b attached to the second magnetoresistive effect element 32 shown in FIGS. 32a and sub-sensitivity axis directions 31b and 32b are shown. Here, the “main sensitivity axis” refers to an axis that faces the direction in which the sensitivity of the first and second magnetoresistive elements 31 and 32 is maximized, and the “sub sensitivity axis” is orthogonal to the main sensitivity axis. This is the axis that faces the direction with the highest sensitivity among the directions.

  Of the magnetic field passing through the first magnetoresistive effect element 31 and the second magnetoresistive effect element 32, the magnetic field components in the same direction as the arrow directions of the main sensitivity axis directions 31a and 32a and the sub sensitivity axis directions 31b and 32b are positive. The negative output voltage is output by the magnetic field component in the direction opposite to the arrow direction of the main sensitivity axis directions 31a and 32a and the sub sensitivity axis directions 31b and 32b.

  As shown in FIG. 4, the main sensitivity axis direction 31a of the first magnetoresistance effect element 31 and the main sensitivity axis direction 32a of the second magnetoresistance effect element 32 are provided in parallel and in the same direction, All are directed in the Z1 direction, that is, the direction orthogonal to the first conductive portion 22, the second conductive portion 23, and the third conductive portion 24.

  As shown in FIG. 4, measured magnetic fields 26 a and 26 b are induced so as to surround each conductive portion by a measured current 25 flowing through the first conductive portion 22 and the second conductive portion 23. The measured magnetic field 26a passes through the first magnetoresistive element 31 in the main sensitivity axis direction 31a. Similarly, the measured magnetic field 26b passes through the second magnetoresistive element 32 in the main sensitivity axis direction 32a. Further, as shown in FIG. 5, the first magnetoresistive effect element 31 and the second magnetic field 26c in the main sensitivity axis directions 31a and 32a are also measured with respect to the measured magnetic field 26c generated by the measured current 25 flowing through the third conductive portion 24. The magnetoresistive effect element 32 passes through.

  The measured magnetic fields 26a to 26c of the first conductive portion 22, the second conductive portion 23, and the third conductive portion 24 are in the main sensitivity axis directions 31a and 32a, respectively. Passes through the magnetoresistive element 32. Therefore, the output signal of the current sensor 10 can be obtained by taking the sum of the output signal of the first magnetoresistive effect element 31 and the output signal of the second magnetoresistive effect element 32. As described above, the current to be measured 25 flowing through the bus bar 21 (the first conductive part 22, the second conductive part 23, and the third conductive part 24) is supplied to the first magnetoresistive element 31 and the second magnetic element. It is detected by the resistance effect element 32.

  In addition, the measured magnetic fields 26 of the first conductive portion 22, the second conductive portion 23, and the third conductive portion 24 are respectively connected to the first magnetoresistive effect element 31 and the first magnetoresistance effect element 31 in the main sensitivity axis directions 31a and 32a. Since the second magnetoresistive effect element 32 is passed through, the maximum detected magnetic field of the current sensor 10 is increased. Therefore, the offset fluctuation width due to the temperature characteristics of the first magnetoresistive element 31 and the second magnetoresistive element 32 is relatively small with respect to the maximum detection magnetic field, so that the measurement accuracy of the current sensor 10 is improved. .

  As shown in FIGS. 4 and 5, the first magnetoresistive element 31 and the second magnetoresistive element 32 are provided at positions intersecting the virtual plane 37, and the main sensitivity axis directions 31a, 32a are provided. Is directed in a direction orthogonal to the virtual plane 37. The sub-sensitivity axis direction 31b of the first magnetoresistance effect element 31 and the sub-sensitivity axis direction 32b of the second magnetoresistance effect element 32 are parallel to the first conductive portion 22 and the second conductive portion 23, respectively. And it is provided in the mutually opposite direction. Therefore, the measured magnetic fields 26a to 26c generated by the measured current 25 flowing through the bus bar 21 pass through the first magnetoresistive effect element 31 and the second magnetoresistive effect element 32 in the main sensitivity axis directions 31a and 32a. Magnetic field components in the sensitivity axis directions 31b and 32b are not generated or are very small even if generated. Therefore, the measurement accuracy of the current sensor 10 can be improved.

  FIG. 6 is a schematic plan view of a current sensor for explaining an external magnetic field passing through the magnetoresistive effect element. In the current sensor 10 of the present embodiment, the first magnetoresistive effect element 31 and the second magnetoresistive effect element 32 are disposed to face each other with the substrate 30 interposed therebetween, and the first magnetoresistive effect element 31 is disposed. And the second magnetoresistive element 32 are small. Therefore, the angle and magnitude of the external magnetic field 29 passing through the first magnetoresistive element 31 and the second magnetoresistive element 32 are substantially equal.

As shown in FIG. 6, the angle between the sub-sensitivity axis 31b and the external magnetic field 29 of the first magnetoresistive element 31 and theta _1, sub sensitivity axis 32b and the outside of the second magnetoresistance effect element 32 the angle between the magnetic field 29 and theta _2. Assuming that the magnitude of the external magnetic field 29 is H, the component H ₁ of the external magnetic field 29 passing through the first magnetoresistive element 31 in the sub-sensitivity axis direction 31 b is expressed as H ₁ = H · cos θ ₁ . Further, the component H ₂ of the external magnetic field 29 passing through the second magnetoresistive element 32 in the sub-sensitivity axis direction 32 b is expressed as H ₂ = H · cos θ ₂ . In the present embodiment, the sub-sensitivity axis directions 31b and 32b are provided in directions opposite to each other, and thus have a relationship of θ ₂ = 180−θ ₁ . _{Thus, H 2 = H · cos (} 180-θ 1) = - Hcosθ 1 = -H 1 , and the sub-sensitivity axis 31b of the external magnetic field 29, the component of 32b, the positive and negative are opposite the same size.

Therefore, by using the sum of the output signal of the first magnetoresistive effect element 31 and the output signal of the second magnetoresistive effect element 32 as the output signal of the current sensor 10, H ₁ and H ₂ are canceled out. . Therefore, the measurement error due to the components in the sub-sensitivity axis directions 31b and 32b of the external magnetic field 29 is surely canceled, and a decrease in output accuracy of the current sensor 10 is suppressed.

FIG. 7 is a block diagram illustrating a circuit configuration example of the current sensor according to the present embodiment. As shown in FIG. 7, the first magnetoresistive effect element 31 and the second magnetoresistive effect element 32 each constitute a bridge circuit. The output of each bridge circuit is amplified by arithmetic circuits 33 and 34 such as a differential amplifier circuit, respectively, and the output signal V _{s1 of} the first magnetoresistive element 31 and the output signal V of the second magnetoresistive element 32. _This is input to the arithmetic circuit 35 as _s2 . As the arithmetic circuit 35, for example, an addition circuit that calculates the sum of the output voltage V _s1 and the output voltage V _s2 is configured, so that the sum of V _s1 and V _s2 is output as the output signal V _out of the current sensor 10. . By calculating the sum of V _s1 and V _s2 in the arithmetic circuit 35, the error component due to the external magnetic field 29 is canceled and the measurement accuracy of the current sensor 10 can be improved.

  As described above, according to the current sensor 10 of the present embodiment, the first magnetoresistive effect element 31 and the second magnetoresistive effect element 32 are connected between the first conductive portion 22 and the second conductive portion 23. In between, they are provided on the same substrate 30. Therefore, the external magnetic field 29 that passes through each of the first magnetoresistive element 31 and the second magnetoresistive element 32 has the same magnitude and direction. Since the sub-sensitivity axis directions 31b and 32b of the first magnetoresistive element 31 and the second magnetoresistive element 32 are provided in opposite directions, the sub-sensitivity axis direction 31b of the external magnetic field 29, The components of 32b are the same size and reverse. Therefore, by taking the sum of the outputs of the first magnetoresistive effect element 31 and the second magnetoresistive effect element 32, the first magnetoresistive effect element 31 and the second magnetoresistive effect element 32 caused by the external magnetic field 29 are used. Measurement errors are offset.

  Therefore, according to the current sensor 10 of the present embodiment, it is possible to suppress a decrease in measurement accuracy due to the external magnetic field 29 when measuring the current flowing through the U-shaped bus bar 21.

  As shown in FIGS. 3 and 4, the first magnetoresistive element 31 and the second magnetoresistive element 32 are in the center between the first conductive part 22 and the second conductive part 23. Although provided, it is not limited to this. The main sensitivity axis directions 31a and 32a are provided in the same direction. As shown in FIG. 7, the sum of the output of the first magnetoresistive element 31 and the output of the second magnetoresistive element 32 is calculated. Therefore, even if the positions of the first magnetoresistive effect element 31 and the second magnetoresistive effect element 32 are appropriately changed, the same sensor output can be obtained.

  In the present embodiment, a GMR (Giant Magneto Resistance) element is used as the first magnetoresistive effect element 31 and the second magnetoresistive effect element 32, but is orthogonal to the main sensitivity axis directions 31a and 32a. There is no particular limitation as long as the magnetoresistive effect elements 31 and 32 have the sub-sensitivity axis directions 31b and 32b in the direction. For example, a TMR (Tunnel Magneto Resistance) element or the like can be used.

<Second Embodiment>
FIG. 8 is a plan view of a current sensor according to the second embodiment. As shown in FIG. 8, in the current sensor 11 of the present embodiment, the first magnetoresistive element 31 and the second magnetoresistive element 32 are both mounted on the first surface 30 a of the substrate 30. Is different.

  The first magnetoresistive element 31 and the second magnetoresistive element 32 are disposed adjacent to each other on the first surface 30a. Also in this embodiment, the main sensitivity axis directions 31a and 32a are provided in parallel and in the same direction, and the sub sensitivity axis directions 31b and 32b are provided in the opposite direction. Therefore, the measured magnetic field 26 (not shown in FIG. 8) passing through each of the first magnetoresistive element 31 and the second magnetoresistive element 32 passes in the main sensitivity axis directions 31a and 32a. Therefore, the measured current 25 can be detected as in the first embodiment.

  Further, since the distance between the first magnetoresistive effect element 31 and the second magnetoresistive effect element 32 is small, the external magnetic field that passes through each of the first magnetoresistive effect element 31 and the second magnetoresistive effect element 32. 29 (not shown in FIG. 8) have approximately equal size and orientation. Thereby, even when the external magnetic field 29 passes through the first magnetoresistive effect element 31 and the second magnetoresistive effect element 32, the components in the sub-sensitivity axis directions 31b and 32b of the external magnetic field 29 have the same magnitude. Now the opposite direction. Therefore, also in the current sensor 11 of this embodiment, by taking the sum of the outputs of the first magnetoresistive effect element 31 and the second magnetoresistive effect element 32, the auxiliary sensitivity axial directions 31b and 32b of the external magnetic field 29 are obtained. The measurement error due to this component is canceled out, and a decrease in measurement accuracy of the current sensor 11 can be suppressed.

<Third Embodiment>
FIG. 9A is a front view of the current sensor according to the third embodiment, and FIG. 9B is a cross-sectional view of the current sensor. In the current sensor 12 of the present embodiment, a shield 36 that sandwiches the first magnetoresistive effect element 31 and the second magnetoresistive effect element 32 in the vertical direction is provided. As a result, electromagnetic noise incident from the outside in the vertical direction is shielded by the shield 36, and output fluctuation due to the electromagnetic noise can be prevented to suppress a decrease in measurement accuracy. Or it can suppress that the electromagnetic noise which generate | occur | produces with the electric current which flows through the bus-bar 21 is radiated | emitted outside.

  In the present embodiment, as in the first and second embodiments, the sub sensitivity axis directions 31b and 32b are provided in opposite directions, so that the components of the external magnetic field 29 in the sub sensitivity axis directions 31b and 32b cancel each other. Is done. Further, as shown in FIG. 9, only the shield 36 is provided between the first magnetoresistive effect element 31 and the second magnetoresistive effect element 32 in the main sensitivity axis directions 31a and 32a. Measurement errors due to components in the main sensitivity axis directions 31a and 32a of the magnetic field 29 can be suppressed. Therefore, the manufacturing cost can be reduced as compared with the case where the shield 36 is provided so as to surround the first magnetoresistive element 31 and the second magnetoresistive element 32.

  In the present embodiment, the shield 36 can be formed of a soft magnetic material such as permalloy, a silicon steel plate, or a Co-based amorphous material. In this case, the shield 36 is used as a magnetic shield, and since these materials are conductive materials, they also function as an electromagnetic shield. Alternatively, the shield 36 made of a conductor such as a metal material or alloy material containing Cu, Fe, or the like can be used as an electromagnetic shield.

<Fourth Embodiment>
FIG. 10 is a schematic diagram illustrating a magnetoresistive element constituting the current sensor of the fourth embodiment. As shown in FIG. 10, the first magnetoresistive effect element 31 and the second magnetoresistive effect element 32 in the present embodiment are composed of a laminated film 41 having a magnetoresistive effect. The laminated film 41 is composed of a plurality of strip-like long patterns, and the plurality of strip-like long patterns are arranged in parallel to each other at intervals, and a plurality of long patterns are folded and connected (a meander shape). Have. The directions orthogonal to the longitudinal direction of the strip-shaped long pattern are the main sensitivity axis directions 31 a and 32 a of the first magnetoresistive element 31 and the second magnetoresistive element 32.

  In the present embodiment, as shown in FIG. 10, bias magnets 42 and 43 that sandwich the laminated film 41 are provided in the longitudinal direction of the strip-like long pattern. A bias magnetic field is applied by the bias magnets 42 and 43 in a direction orthogonal to the main sensitivity axis directions 31a and 32a. The direction of this bias magnetic field is the sub-sensitivity axis directions 31b and 32b. Therefore, since the resistance values of the first magnetoresistive element 31 and the second magnetoresistive element 32 in the initial state where the measured current 25 (not shown in FIG. 10) does not flow are controlled by the bias magnetic field, The measurement sensitivity and offset of the current sensor can be controlled.

  Further, by providing the bias magnets 42 and 43, the direction of the secondary sensitivity axis can be reliably controlled, so that the components of the secondary sensitivity axis directions 31b and 32b of the external magnetic field 29 (not shown in FIG. 10) are appropriately set. A cancelable configuration can be realized. Therefore, it is possible to reduce the influence of the external magnetic field in the sub-sensitivity axis directions 31b and 32b, and to suppress a decrease in current measurement accuracy.

10, 11, 12 Current sensor 21 Bus bar 22 First conductive portion 23 Second conductive portion 24 Third conductive portion 25 Current to be measured 26, 26a to 26c Magnetic field to be measured 29 External magnetic field 30 Substrate 30a First surface 30b Second surface 31 First magnetoresistive element 31a Main sensitivity axis direction 31b Subsensitivity axis direction 32 Second magnetoresistive element 32a Main sensitivity axis direction 32b Subsensitivity axis direction 33, 34, 35 Arithmetic circuit 36 Shield 37 Virtual plane 41 Laminated film 42, 43 Bias magnet

Claims (5)

A U-shaped bus bar comprising a first conductive portion and a second conductive portion arranged at intervals, and a third conductive portion connecting the first conductive portion and the second conductive portion; ,
A substrate disposed between the first conductive portion and the second conductive portion;
A first magnetoresistive element and a second magnetoresistive element mounted on the substrate;
The first magnetoresistive element and the second magnetoresistive element each have a main sensitivity axis and a secondary sensitivity axis perpendicular to the main sensitivity axis,
The directions of the main sensitivity axes of the first magnetoresistive element and the second magnetoresistive element are provided in parallel to each other, and the first magnetoresistive element and the second magnetoresistive effect are provided. A current sensor, wherein directions of the sub-sensitivity axes of the elements are provided in opposite directions to each other. The substrate has a first surface facing the first conductive portion, and a second surface facing the second conductive portion,
The first magnetoresistive element is provided on the first surface, and the second magnetoresistive element is provided on the second surface, and the first magnetoresistive element and the first magnetoresistive element are provided. The current sensor according to claim 1, wherein the two magnetoresistive elements are provided to face each other. The first magnetoresistive element and the second magnetoresistive element each have a bias magnet that applies a bias magnetic field in a direction perpendicular to the main sensitivity axis,
The current sensor according to claim 1, wherein the direction of the auxiliary sensitivity axis is a direction of the bias magnetic field. The main sensitivity axis direction of each of the first magnetoresistive element and the second magnetoresistive element passes through the first conductive part, the second conductive part, and the third conductive part. Provided in a direction perpendicular to the virtual plane,
The current sensor according to any one of claims 1 to 3, further comprising a shield sandwiching the virtual plane in the main sensitivity axis direction.   The directions of the main sensitivity axes of the first magnetoresistive element and the second magnetoresistive element are provided in the same direction, and the output of the first magnetoresistive element and the second magnetism 5. The current sensor according to claim 1, further comprising an arithmetic unit that calculates a sum with an output of the resistance effect element. 6.

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