JP6144597B2 - Current sensor - Google Patents

Description

  The present invention relates to a current sensor that detects a current based on an induced magnetic field of a current flowing through a conductor, and more particularly to a current sensor that detects a current using a magnetoelectric conversion element.

  As a method of detecting current, generally, a method of detecting a voltage drop of a resistor (shunt resistor) provided in a current path, a method of using a current transformer (CT), a magnetoelectric conversion element (Hall element, magnetic) A method using a resistance element or the like is known. Although the method of detecting the voltage drop of the resistor can detect a current in a wide frequency band of direct current and alternating current, a circuit such as a photocoupler must be added to insulate the measurement system from the system to be measured. On the other hand, the method using a current transformer is widely used mainly in equipment and facilities that handle alternating current because the measurement system and the system to be measured are insulated and the configuration is relatively simple and inexpensive. .

  On the other hand, a method using a magnetoelectric conversion element such as a Hall element detects current by converting a magnetic field generated in a current path to be detected into voltage or electrical resistance. This method has an excellent feature that, in addition to the measurement system and the system to be measured being insulated, the current can be detected in a wide frequency band of direct current and alternating current.

  Patent Document 1 below describes a current sensor configured to detect a current flowing in a conductive member (bus bar) attached to a terminal of an in-vehicle battery by a magnetoelectric conversion element. This current sensor has a slit for accommodating a conductive member through which a current to be detected flows, and a magnetoelectric conversion element and a bias magnet provided at a position orthogonal to the front surface or the back surface of the conductive member accommodated in the slit. . The magnetoelectric conversion element and the bias magnet are mounted on a circuit board.

JP 2011-242367 A

  Usually, a magnetoelectric conversion element has a sensitivity axis that maximizes the magnetic field detection sensitivity. However, some magneto-electric transducers with relatively high sensitivity (such as GMR elements with hard bias, TMR elements, and Hall elements with magnetic converging plates) affect the sensitivity of magnetic field detection in addition to this sensitivity axis. There is an axis (sensitivity influence axis) that gives When such a highly sensitive magnetoelectric conversion element is used, the magnetic field component of the sensitivity influence axis included in the induced magnetic field of the current to be detected becomes a factor that lowers the linearity of the detection sensitivity.

  FIG. 13 is a diagram illustrating an example of a configuration of a current sensor that detects a current flowing through an elongated plate-like bus bar, and is a diagram viewed from a cross-sectional direction of the bus bar. The current I of the bus bar 100 flows from the front side to the back side (Y direction). A dotted line drawn around the bus bar 100 represents a magnetic flux line of an induced magnetic field generated by the current I flowing through the bus bar 100. The magnetic flux lines are oval closed curves surrounding the bus bar 100.

  The current sensor shown in FIG. 13 has two magnetoelectric conversion elements (200A, 200B) arranged on the upper surface side and the lower surface side of the bus bar 100. These magnetoelectric transducers (200A, 200B) each have a sensitivity axis (S1A, S1B) at which the detection sensitivity is maximum and a sensitivity influence axis (S2A, S2B) orthogonal thereto. The sensitivity axes (S1A, S1B) face in the direction parallel to the surface of the bus bar 100 (X direction), and the sensitivity influence axes (S2A, S2B) face in the direction perpendicular to the surface of the bus bar 100 (Z direction). ing.

  FIG. 14 is a diagram illustrating a result of obtaining the direction of the induced magnetic field due to the current flowing in the long and narrow plate-like bus bar by simulation. As can be seen from the simulation results in FIG. 14, the direction of the magnetic field is nearly horizontal near the center in the width direction of the bus bar 100, and the magnetic field component in the X direction becomes dominant. Therefore, by directing the sensitivity axis (S1A, S1B) in the X direction, the induced magnetic field can be detected with high sensitivity.

On the other hand, FIG. 15 is a graph showing the result of the simulation for the strength of the induced magnetic field caused by the current flowing in the elongated plate-like bus bar. “Hx”, “Hy”, and “Hz” in FIG. 15 represent magnetic field components in the X, Y, and Z directions, respectively. The vertical axis in FIG. 15 indicates the strength of each magnetic field component, and the horizontal axis indicates the position [mm] in the X direction. The position of 20 [mm] on the horizontal axis corresponds to the center of the bus bar 100 in the width direction.
From the simulation result of FIG. 15, it can be seen that the magnetic field component Hx in the X direction is substantially larger than the other magnetic field components near the center in the width direction of the bus bar 100. However, there are not a few magnetic field components Hz parallel to the sensitivity influence axes (S2A, S2B). The magnetic field component Hz becomes zero at the center in the width direction of the bus bar 100 (position of 20 [mm] on the horizontal axis in FIG. 15), but increases linearly as the distance from the center increases. That is, the magnetic field component Hz is generated even at a position slightly deviated from the center of the bus bar 100 in the width direction, and increases linearly as the deviation increases.

  As described above, in the current sensor shown in FIG. 13, the magnetic field parallel to the sensitivity influence axis (S2A, S2B) is obtained only by slightly shifting the position of the magnetoelectric conversion element (200A, 200B) from the center in the width direction of the bus bar 100. There is a problem that the component Hz appears and the linearity of the detection sensitivity is lowered. If the sensitivity-inducing axis component is present in the induced magnetic field to be detected, it is difficult to improve the linearity by gain adjustment or offset adjustment in the subsequent circuit of the magnetoelectric transducer.

  The present invention has been made in view of such circumstances, and an object of the present invention is to reduce a magnetic field component parallel to the sensitivity influence axis of a magnetoelectric conversion element among magnetic field components included in an induced magnetic field of a detected current. It is to provide a sensor.

A current sensor according to a first aspect of the present invention includes at least one magnetoresistive element having a sensitivity axis that maximizes the magnetic field detection sensitivity, a sensitivity influence axis that affects the magnetic field detection sensitivity, A conductive member that extends linearly in the direction in which the current flows, and that has a cross section perpendicular to the extending direction and a shape that is symmetric with respect to a virtual first symmetry axis. The conductive member includes a first conductive portion and a second conductive portion that are spaced apart from each other with a gap through which the first axis of symmetry passes, and the shunt currents of the detected current flow in the same direction. The magnetoresistive element is in a posture before Symbol sensitivity effect axis is parallel to the first axis of symmetry, an outer region of the gap, the viewed from the first axis of symmetry parallel to direction It arrange | positions in the area | region which overlaps with a space | gap .

  According to the above configuration, in the region outside the gap and overlapping with the gap as viewed from the direction parallel to the first symmetry axis, no current flows in the gap, and thus the gap The magnetic field component in the direction parallel to the first axis of symmetry passing through is reduced. Therefore, by arranging the magnetoelectric conversion element in this region and giving the posture that the sensitivity influence axis is parallel to the first symmetry axis, the magnetic field component of the sensitivity influence axis is reduced, and the detection sensitivity The decrease in linearity is effectively suppressed.

  Preferably, the magnetoresistive effect element may be arranged at a position where the sensitivity influence axis overlaps the first symmetry axis and a magnetic field component parallel to the sensitivity influence axis is minimized. Thereby, the fall of the linearity of a detection sensitivity is suppressed more effectively.

  Suitably, the said magnetoresistive effect element may be arrange | positioned in the center of the said space | gap in the said extending | stretching direction seeing from the direction parallel to the said 1st symmetry axis. Thereby, the influence on the magnetic field component of the sensitivity influence axis by the disturbance of the magnetic field symmetry at the end of the gap is reduced.

  Suitably, the cross section of the said 1st electroconductive part in the said extending | stretching direction and the said 2nd electroconductive part may have the shape symmetrical with respect to the 2nd symmetry axis orthogonal to the said 1st symmetry axis. In this case, the current sensor according to the first aspect includes a pair of the magnetoresistive effect elements disposed at positions facing each other with the gap in a direction parallel to the first symmetry axis, and the pair of magnetic sensors. And a calculation unit that calculates a detected current value based on an output signal of the resistance effect element.

  Suitably, the current sensor which concerns on the said 1st viewpoint may have a circuit board arrange | positioned along the plane orthogonal to the said extending | stretching direction of the said electrically-conductive member. The circuit board may include a first arm portion and a second arm portion facing each other with the gap of the conductive member interposed therebetween. One of the pair of magnetoresistive elements may be attached to the first arm, and the other of the pair of magnetoresistive elements may be attached to the second arm. This improves the accuracy of relative positioning of the pair of magnetoresistive elements.

  Preferably, the current sensor according to the first aspect may include a pair of magnetic shields disposed at positions facing each other with the pair of magnetoresistive elements interposed therebetween. Thereby, the influence on the detection accuracy of the external magnetic field is mitigated.

  Preferably, the first conductive portion and the second conductive portion may have a rectangular shape in cross section perpendicular to the extending direction. In this case, one side surface of the first conductive part and the one side surface of the second conductive part that form the gap may be parallel to each other.

A current sensor according to a second aspect of the present invention includes at least one magnetoresistive element having a sensitivity axis that maximizes magnetic field detection sensitivity and a sensitivity influence axis that affects magnetic field detection sensitivity;
A conductive member that extends linearly in the direction in which the current to be detected flows and whose cross section perpendicular to the extending direction has a line-symmetric shape with respect to a virtual first symmetry axis. The conductive member has a groove that passes through the first axis of symmetry and is recessed in the direction of the first axis of symmetry. The magnetoresistive element is in a posture before Symbol sensitivity effect axis is parallel to the first axis of symmetry, wherein a region outside the groove, the viewed from the first axis of symmetry parallel to direction It arrange | positions in the area | region which overlaps with a groove | channel .

  According to the above configuration, in the region outside the groove and overlapping the groove when viewed from the direction parallel to the first symmetry axis, no current flows in the groove space, The magnetic field component in the direction parallel to the first axis of symmetry passing through the groove is reduced. Therefore, by arranging the magnetoelectric conversion element in this region and giving the posture that the sensitivity influence axis is parallel to the first symmetry axis, the magnetic field component of the sensitivity influence axis is reduced, and the detection sensitivity The decrease in linearity is effectively suppressed.

  Preferably, the magnetoresistive effect element may be arranged at a position where the sensitivity influence axis overlaps the first symmetry axis and a magnetic field component parallel to the sensitivity influence axis is minimized. Thereby, the fall of the linearity of a detection sensitivity is suppressed more effectively.

  Preferably, the magnetoresistive effect element may be disposed at the center of the groove in the extending direction when viewed from a direction parallel to the first symmetry axis. Thereby, the influence on the magnetic field component of the sensitivity influence axis by the disturbance of the magnetic field symmetry at the end of the gap is reduced.

  Suitably, the cross section of the said electrically-conductive member in the said extending | stretching direction may have the shape symmetrical with respect to the 2nd symmetry axis orthogonal to the said 1st symmetry axis. In this case, the conductive member may have a pair of grooves extending in the extending direction. The current sensor according to the second aspect includes a pair of the magnetoresistive elements disposed at positions facing each other across the pair of grooves in a direction parallel to the first symmetry axis, and the pair of magnetoresistive elements. A calculation unit that calculates a detected current value based on an output signal of the effect element.

  Suitably, the current sensor which concerns on the said 2nd viewpoint may have a circuit board arrange | positioned along the plane orthogonal to the said extending | stretching direction of the said electrically-conductive member. The circuit board may include a first arm portion and a second arm portion facing each other with the pair of grooves interposed therebetween. One of the pair of magnetoresistive elements may be attached to the first arm, and the other of the pair of magnetoresistive elements may be attached to the second arm. This improves the accuracy of relative positioning of the pair of magnetoresistive elements.

  Preferably, the current sensor according to the second aspect may include a pair of magnetic shields disposed at positions facing each other with the pair of magnetoresistive elements interposed therebetween. Thereby, the influence on the detection accuracy of the external magnetic field is mitigated.

Preferably, the groove may have a rectangular or trapezoidal cross section perpendicular to the extending direction.
Preferably, the magnetoresistive effect element may be arranged at a position where a magnetic flux line generated by the detected current becomes flat.

  According to the present invention, among magnetic field components included in the induced magnetic field of the current to be detected, magnetic field components parallel to the sensitivity influence axis of the magnetoelectric conversion element can be reduced.

It is a figure which shows an example of a structure of the current sensor which concerns on the 1st Embodiment of this invention, and is the figure seen from the direction perpendicular | vertical with respect to the extending | stretching direction of an electrically-conductive member. It is a figure which shows an example of a structure of the current sensor which concerns on the 1st Embodiment of this invention, and is sectional drawing in the Y1-Y1 line | wire of FIG. It is a figure which shows an example of the circuit structure of the current sensor which concerns on the 1st Embodiment of this invention. It is a figure which shows an example of a structure of the current sensor which concerns on the 1st Embodiment of this invention, and is the figure which illustrated the circuit board and magnetic shield in which a magnetoelectric conversion element is mounted with a conductive member. It is a figure which shows an example of the result of having calculated | required the direction of the induction magnetic field in the current sensor shown in FIG. 1 by simulation. It is a figure which shows an example of the result of having calculated | required the intensity | strength of the induction magnetic field in the current sensor shown in FIG. 1 by simulation. It is a figure which shows the modification of the current sensor which concerns on 1st Embodiment. It is a figure which shows an example of a structure of the current sensor which concerns on the 2nd Embodiment of this invention, and is the figure seen from the direction perpendicular | vertical with respect to the extending | stretching direction of an electrically-conductive member. It is a figure which shows an example of a structure of the current sensor which concerns on the 2nd Embodiment of this invention, and is sectional drawing in the Y2-Y2 line | wire of FIG. It is a figure which shows an example of a structure of the current sensor which concerns on the 2nd Embodiment of this invention, and is the figure which illustrated the circuit board and magnetic shield in which a magnetoelectric conversion element is mounted with a conductive member. It is a figure which shows an example of the result of having calculated | required the direction of the induction magnetic field in the current sensor shown in FIG. 8 by simulation. It is a figure which shows an example of the result of having calculated | required the intensity | strength of the induction magnetic field in the current sensor shown in FIG. 8 by simulation. It is a figure which shows an example of a structure of the current sensor which detects the electric current which flows into an elongate plate-shaped bus bar, and is the figure seen from the cross-sectional direction of the bus bar. It is a figure which shows the result of having calculated | required the direction of the induced magnetic field by the electric current which flows into an elongate plate-shaped bus bar by simulation. It is a graph which shows the result of having calculated | required the intensity | strength of the induced magnetic field by the electric current which flows into an elongate plate-shaped bus bar by simulation.

<First Embodiment>
FIG. 1 is a diagram illustrating an example of the configuration of the current sensor 1 according to the first embodiment of the present invention, and is a diagram viewed from a direction perpendicular to the extending direction of the conductive member 10. 2 is a cross-sectional view taken along line Y1-Y1 of the current sensor 1 shown in FIG.
The current sensor 1 according to the present embodiment includes a conductive member 10 through which a current to be detected flows, and magnetoelectric conversion elements 20A and 20B that detect an induced magnetic field due to the current to be detected flowing through the conductive member 10.

  The conductive member 10 extends linearly (straightly), and a detected current flows in the extending direction. In the example of FIG. 1, the conductive member 10 extends in the vertical direction (Y direction) of the paper surface, and the detected current flows in the same direction.

  The cross section perpendicular to the extending direction of the conductive member 10 has a shape that is line symmetric with respect to the first symmetry axis L1 and the second symmetry axis L2 in FIG. The first symmetry axis L1 extends in the vertical direction (Z direction) of the paper surface of FIG. 2, and the second symmetry axis L2 extends in the horizontal direction (X direction) of the paper surface of FIG. In FIG. 2, the current to be detected of the conductive member 10 flows in the direction from the front to the back (Y direction).

  As shown in FIG. 2, since the cross section of the conductive member 10 perpendicular to the direction in which the detected current flows has a line-symmetric shape, the magnetic flux lines of the detected current surrounding this cross section are also connected to the conductive member 10. Similar to the cross section, a closed curve having a line-symmetric shape with respect to the first symmetry axis L1 and the second symmetry axis L2.

  In addition, the conductive member 10 includes a first conductor portion 11 and a second conductor portion 12 that are separated from each other with the gap 5 therebetween. The first symmetry axis L1 described above passes through the gap 5. Therefore, the cross sections of the first conductor portion 11 and the second conductor portion 12 perpendicular to the extending direction (Y direction) of the conductive member 10 have a symmetrical shape with respect to the first symmetry axis L1, as shown in FIG.

  The cross sections of the first conductor portion 11 and the second conductor portion 12 perpendicular to the extending direction (Y direction) of the conductive member 10 are uniform at each position in the extending direction (Y direction) of the conductive member 10. That is, the cross section perpendicular to the Y direction is the same at any position in the region AR1 (FIG. 1) where the first conductor portion 11 and the second conductor portion 12 are formed.

  The detected current flowing through the conductive member 10 is divided into the first conductor portion 11 and the second conductor portion 12. A shunt current I11 flows through the first conductor portion 11, and a shunt current I12 flows through the second conductor portion 12. Since the first conductor portion 11 and the second conductor portion 12 are made of the same conductive material and have a symmetrical shape as described above, the shunt current I11 of the first conductor portion 11 and the second conductor The shunt current I12 of the part 12 is substantially the same.

  The magnetic flux lines generated by the shunt currents I11 and I12 are closed curves having a symmetrical shape with respect to the first symmetry axis L1 passing through the center of the gap 5, as indicated by the dotted lines in FIG. Since no current flows through the gap 5, the magnetic field becomes weak in the vicinity of the gap 5. For example, as shown in FIG. 2, the magnetic flux lines close to the first conductor portion 11 and the second conductor portion 12 pass through the gap 5 and form a closed curve that individually surrounds the first conductor portion 11 and the second conductor portion 12. When slightly separated from the first conductor portion 11 and the second conductor portion 12, the magnetic flux lines do not penetrate the gap 5, and become a closed curve that surrounds both the first conductor portion 11 and the second conductor portion 12. However, since the magnetic field in the vicinity of the gap 5 is weak, the magnetic flux lines become a closed curve that is recessed toward the gap 5. As the distance from the first conductor portion 11 and the second conductor portion 12 increases, the dent of the magnetic flux line in the direction of the air gap 5 decreases, and the magnetic flux line is separated from the first conductor portion 11 and the second conductor portion 12 by a certain distance. Becomes almost flat. The flat magnetic flux line means that the magnetic field component in the direction (Z direction) parallel to the first axis of symmetry L1 passing through the air gap 5 is minimized.

  In the example of FIG. 2, the first conductor portion 11 and the second conductor portion 12 have a rectangular cross section perpendicular to the extending direction (Y direction) of the conductive member 10. Further, one side surface 51 of the first conductor part 11 and one side surface 52 of the second conductor part 12 forming the gap 5 are parallel to each other. Such a shape of the conductive member 10 can be easily formed by, for example, punching a hole in the center of an elongated plate-like conductive plate.

  The magnetoelectric conversion elements 20A and 30B are elements that output a change in resistance, voltage, or the like according to the induced magnetic field of the current to be detected as a detection signal. The magnetoresistive conversion element is configured. The magnetoelectric conversion elements 20A and 30B have a sensitivity influence axis that affects the detection sensitivity of the magnetic field in addition to the sensitivity axis that maximizes the detection sensitivity of the magnetic field. The magnetoelectric conversion element 20A has a sensitivity axis S1A and a sensitivity influence axis S2A that are orthogonal to each other. The magnetoelectric conversion element 20B has a sensitivity axis S1B and a sensitivity influence axis S2B that are orthogonal to each other.

For example, in a magnetoresistive change element such as a GMR element or a TMR element including a hard bias layer, the magnetization direction of the magnetization free layer with respect to the magnetization direction of the ferromagnetic pinned layer (PIN) is set to a certain direction by the bias magnetic field of the hard bias layer. To bias. Thereby, the range in which the resistance value changes linearly according to the magnetic field can be expanded. The same direction as the bias magnetic field corresponds to the sensitivity influence axis. When a magnetic field is applied in the same direction as the bias magnetic field, the bias magnetic field substantially fluctuates, so that the linearity of detection sensitivity decreases. The sensitivity influence axis by the bias magnetic field is generally orthogonal to the sensitivity axis.
Some magnetoelectric transducers with high sensitivity have detection sensitivity relatively weaker than the sensitivity axis in an axis orthogonal to the sensitivity axis. Such a weakly sensitive axis (sometimes called a secondary sensitivity axis) is also an axis that affects the detection sensitivity.

  The magnetoelectric conversion elements 20A and 20B are arranged in a region outside the gap 5 and overlapping the gap 5 when viewed from the direction parallel to the first symmetry axis L1. In this region, since no current flows through the gap 5, the magnetic field component (magnetic field component in the Z direction) in the direction parallel to the first symmetry axis L1 passing through the gap 5 is small. In this region, the magnetoelectric conversion elements 20A and 20B are arranged in such a posture that the sensitivity influence axes S2A and S2B are parallel to the first symmetry axis L1 (Z direction). Thereby, since the magnetic field component of sensitivity influence axis | shaft S2A and S2B becomes small, the fall of the linearity of detection sensitivity can be suppressed.

  Further, the magnetoelectric conversion elements 20A and 20B are positions where the sensitivity influence axes S2A and S2B overlap with the first symmetry axis L1, and the magnetic field component parallel to the first symmetry axis L1 (magnetic field component in the Z direction) is minimal. It is arranged at the position. That is, the magnetoelectric conversion elements 20 </ b> A and 20 </ b> B are respectively arranged on the first symmetry axis L <b> 1 and at an appropriate distance from the first conductor portion 11 and the second conductor portion 12. By disposing the magnetoelectric conversion elements 20A and 20B at this position, the magnetic field components of the sensitivity affecting axes S2A and S2B can be minimized.

  Furthermore, the magnetoelectric conversion elements 20A and 20B are viewed from the direction parallel to the first symmetry axis L1 (Z direction), and the center of the gap 5 in the extending direction (Y direction) of the conductive member 10 (in the region AR1 in FIG. 1). (Center). Near the end of the gap 5, the symmetry of the magnetic field in the Y direction is disturbed, so that a magnetic field component in the Z direction is likely to occur. At the center of the gap 5 farthest from both ends of the gap 5, the influence of this symmetry disturbance is alleviated, so that the magnetic field component in the Z direction parallel to the sensitivity influence axes S2A and S2B is suppressed. Therefore, by arranging the sensitivity influence axes S2A and S2B at this position, the magnetic field components of the sensitivity influence axes S2A and S2B can be further reduced.

  The magnetoelectric conversion element 20 </ b> A and the magnetoelectric conversion element 20 </ b> B are arranged at positions facing each other with the gap 5 of the conductive member 10 interposed therebetween. For example, as shown in FIG. 2, they are arranged on a common first symmetry axis L <b> 1 and at a position separated from the first conductor portion 11 and the second conductor portion 12 by a substantially equal distance. Since the cross sections of the first conductor portion 11 and the second conductor portion 12 have a line-symmetric shape with respect to the second symmetry axis L2, the induced magnetic field of the detected current in the magnetoelectric conversion element 20A and the magnetoelectric conversion element 20B. Are substantially equal in size.

  In the example of FIG. 2, the sensitivity axis S1A of the magnetoelectric conversion element 20A and the sensitivity axis S1B of the magnetoelectric conversion element 20B are in the same direction (X direction), and the sensitivity influence axis S2A of the magnetoelectric conversion element 20A and the magnetoelectric conversion element 20B The sensitivity affecting axis S2B is also directed in the same direction (Z direction). Therefore, the induced magnetic fields of the detected currents acting on the sensitivity axes (S1A, S1B) of the two magnetoelectric transducers (20A, 20B) are opposite to each other, and the detected fields acting on these sensitivity influence axes (S2A, S2B). The induced magnetic fields of the currents are also opposite to each other. Accordingly, the detection signals of the magnetoelectric conversion element 20A and the magnetoelectric conversion element 20B due to the induced magnetic field of the detected current have opposite polarities with respect to the sensitivity axes (S1A, S1B), and also with respect to the sensitivity influence axes (S2A, S2B). Become.

FIG. 3 is a diagram illustrating an example of a circuit configuration of the current sensor 1 according to the present embodiment.
The current sensor 1 according to the present embodiment includes a calculation unit 50 that calculates a detected current value based on the output signals of the pair of magnetoelectric conversion elements 20A and 20B. As shown in FIG. 2, when the sensitivity axis S1A and the sensitivity axis S1B are in the same direction and the sensitivity influence axis S2A and the sensitivity influence axis S2A are in the same direction, the calculation unit 50 outputs the output signals of the pair of magnetoelectric transducers 20A and 20B. The detected current value is calculated according to the difference. Thereby, the detection signals of the induced magnetic fields having opposite polarities in the pair of magnetoelectric conversion elements 20A and 20B are added together by calculating the difference. In addition, the detection signal generated in the pair of magnetoelectric transducers 20A and 20B by the external magnetic field unrelated to the detected current has the same polarity as in the case of the induced magnetic field of the detected current. Can be canceled by calculation.

FIG. 4 is a diagram showing an example of the configuration of the current sensor according to the present embodiment, and is a diagram illustrating the circuit board 30 on which the magnetoelectric conversion elements 20A and 20B are mounted and the magnetic shields 40A and 40B together with the conductive member 10. .
For example, as illustrated in FIG. 4, the current sensor 1 according to the present embodiment includes a circuit board 30 arranged along a plane orthogonal to the extending direction (Y direction) of the conductive member 10. The circuit board 30 includes a first arm portion 31 and a second arm portion 32 that face each other with the gap 5 of the conductive member 10 interposed therebetween. The magnetoelectric conversion element 20 </ b> A is attached to the first arm portion 31, and the magnetoelectric conversion element 20 </ b> B is attached to the second arm portion 32. In this way, by attaching the pair of magnetoelectric conversion elements 20A and 20B on the common circuit board 30, both can be positioned with high accuracy, and a decrease in detection accuracy due to misalignment can be suppressed.

  Moreover, the current sensor 1 according to the present embodiment includes a pair of magnetic shields 40A and 40B disposed at positions facing each other with the pair of magnetoelectric conversion elements 20A and 20B interposed therebetween, as shown in FIG. 4, for example. By providing the magnetic shields 40A and 40B outside the conductive member 10 and the pair of magnetoelectric conversion elements 20A and 20B, the influence of the external magnetic field can be effectively reduced.

  FIG. 5 is a diagram illustrating an example of a result of obtaining the direction of the induced magnetic field in the current sensor 1 by simulation. When FIG. 5 is compared with FIG. 14, the direction of the magnetic field in the vicinity of the center in the width direction of the conductive member 10 is closer to the horizontal in the simulation result shown in FIG.

FIG. 6 is a graph showing an example of the result of obtaining the strength of the induced magnetic field in the current sensor 1 by simulation. “Hx”, “Hy”, and “Hz” in FIG. 6 represent magnetic field components in the X, Y, and Z directions, respectively. The vertical axis in FIG. 6 indicates the strength of each magnetic field component, and the horizontal axis indicates the position [mm] in the X direction. The position of 20 [mm] on the horizontal axis corresponds to the center in the width direction of the conductive member 10.
6 and FIG. 15, in the simulation result of FIG. 6, the magnetic field component Hz in the Z direction is substantially zero near the center in the width direction of the conductive member 10 (near 20 [mm] on the horizontal axis). This zero range is about 2 mm near the center in the width direction. That is, the range in which the magnetic field component Hz in the Z direction is minimized is much wider than in the past.

  As described above, in the current sensor 1 according to the present embodiment, the conductive member 10 extends linearly in the direction in which the current to be detected flows, and the cross section perpendicular to the extending direction is line symmetrical. have. In addition, the conductive member 10 includes a first conductor portion 11 and a first conductor portion 11 that are separated from each other with a gap 5 through which the first axis of symmetry L1 passes, and the shunt current of the detected current is the first conductor. The part 11 and the first conductor part 11 flow in the same direction. Therefore, in the area outside the gap 5 and overlapping the gap 5 when viewed from the direction parallel to the first symmetry axis L1, the first current passing through the gap 5 is not flowing through the gap 5. The magnetic field component (magnetic field component in the Z direction) in the direction parallel to the symmetry axis L1 is reduced. Accordingly, the magnetoelectric conversion elements 20A and 20B are arranged in this region, and the sensitivity influencing axes S2A and S2B are arranged such that the sensitivity influencing axes S2A and S2B are parallel to the first symmetry axis L1 (Z direction). The magnetic field component of S2B is reduced, and it is possible to effectively suppress a decrease in detection sensitivity linearity.

  In the above embodiment, one gap 5 is formed in the conductive member 10 and the current to be detected is divided into the two conductor portions (11, 12). However, the number of gaps may be larger. . FIG. 7 is a view showing a modification of the current sensor according to the present embodiment, and shows a current sensor 1A having a conductive member 10A provided with three gaps (5, 6, 7). The conductive member 10A shown in FIG. 7 is provided with gaps 6 and 7 on both sides of the gap 5 of the conductive member 10 shown in FIG. The first conductor portion 11 in the conductive member 10 </ b> A includes two conductor portions 101 and 102 separated by the gap 6. The second conductor portion 12 in the conductive member 10 </ b> A includes two conductor portions 103 and 104 separated by the gap 7. By these conductor portions, the detected current is divided into four currents (I101, I102, I103, and I104). Also in the current sensor 1A having the conductive member 10A as described above, the magnetic field components of the sensitivity affecting axes S2A and S2B can be reduced, and the same effect as the current sensor 1 can be obtained.

<Second Embodiment>
Next, a current sensor according to a second embodiment of the present invention will be described.
In the current sensor according to the first embodiment described above, a region where the magnetic field component of the sensitivity influence axis is reduced by forming a gap in the conductive member is formed. By forming the groove in the member, a region where the magnetic field component of the sensitivity influence axis is reduced is formed.

FIG. 8 is a diagram illustrating an example of the configuration of the current sensor 1B according to the second embodiment, and is a diagram viewed from a direction perpendicular to the extending direction of the conductive member 10B. FIG. 9 is a diagram illustrating an example of the configuration of the current sensor according to the second embodiment, and is a cross-sectional view taken along line Y2-Y2 of FIG. FIG. 10 is a diagram illustrating the circuit board 30 on which the magnetoelectric conversion elements 20A and 20B are mounted and the magnetic shields 40A and 40B together with the conductive member 10B.
The current sensor 1B according to the present embodiment includes a conductive member 10B through which a detected current flows, magnetoelectric conversion elements 20A and 20B that detect an induced magnetic field due to the detected current flowing through the conductive member 10B, and magnetoelectric conversion elements 20A and 20B. It has the calculating part 50 which processes an output signal, the circuit board 30 in which the magnetoelectric conversion elements 20A and 20B are mounted, and magnetic shields 40A and 40B. Since the magnetoelectric conversion elements 20A and 20B, the calculation unit 50, the circuit board 30, and the magnetic shields 40A and 40B are the same as those of the current sensor 1 according to the first embodiment already described, the description thereof is omitted.

  The conductive member 10B extends linearly (straight), and a current to be detected flows in the extending direction. In the example of FIG. 8, the conductive member 10 extends in the vertical direction (Y direction) of the paper surface, and the detected current flows in the same direction.

  The cross section perpendicular to the extending direction of the conductive member 10 has a symmetrical shape with respect to the first symmetry axis L1 and the second symmetry axis L2 in FIG. The first symmetry axis L1 extends in the vertical direction (Z direction) of the paper surface of FIG. 9, and the second symmetry axis L2 extends in the horizontal direction (X direction) of the paper surface of FIG. In FIG. 9, the detected current of the conductive member 10B flows from the front side to the back side (Y direction).

  As shown in FIG. 9, since the cross section of the conductive member 10B perpendicular to the direction in which the detected current flows has a line-symmetric shape, the magnetic flux lines of the detected current surrounding this cross section are also connected to the conductive member 10B. Similar to the cross section, a closed curve having a line-symmetric shape with respect to the first symmetry axis L1 and the second symmetry axis L2.

  Further, the conductive member 10B has a pair of grooves 13A and 13B that are recessed in the direction of the first axis of symmetry L1 on the surface thereof. In the example of FIG. 9, the conductive member 10 </ b> B is an elongated plate-like member, and the grooves 13 </ b> A and 13 </ b> B have a rectangular cross section perpendicular to the extending direction (Y direction) of the plate-like member. The first symmetry axis L1 passes through the grooves 13A and 13B. Therefore, the cross sections of the grooves 13A and 13B perpendicular to the extending direction (Y direction) of the conductive member 10 have a symmetrical shape with respect to the first symmetry axis L1, as shown in FIG. Further, the end surfaces of the grooves 13A and 13B have a symmetrical shape with respect to the second symmetry axis L2.

  In the area AR2 where the grooves 13A and 13B are formed, the cross section perpendicular to the extending direction (Y direction) of the conductive member 10B is uniform at each position in the extending direction (Y direction) of the conductive member 10B. That is, the cross section perpendicular to the Y direction is the same at any position in the region AR1 (FIG. 1) where the grooves 13A and 13B are formed.

  The magnetic flux lines generated by the detected current flowing through the conductive member 10B are closed curves having a symmetrical shape with respect to the first symmetry axis L1 passing through the centers of the grooves 13A and 13B, as shown by the dotted lines in FIG. Since no current flows in the spaces of the grooves 13A and 13B, the magnetic field becomes weak in the vicinity of the grooves 13A and 13B. Therefore, the magnetic flux lines surrounding the conductive member 10B are closed curves that are recessed in a direction approaching the grooves 13A and 13B. As the distance from the conductive member 10B increases, the dents of the magnetic flux lines in the direction of the grooves 13A and 13B become smaller, and the magnetic flux lines become substantially flat at a distance from the conductive member 10B. The flat magnetic flux line means that the magnetic field component in the direction (Z direction) parallel to the first axis of symmetry L1 passing through the grooves 13A and 13B is minimized.

  The magnetoelectric conversion elements 20A and 20B are disposed in regions outside the grooves 13A and 13B and overlapping the grooves 13A and 13B when viewed from a direction parallel to the first symmetry axis L1. In this region, since no current flows in the spaces of the grooves 13A and 13B, the magnetic field component in the direction parallel to the first axis of symmetry L1 passing through the grooves 13A and 13B (the magnetic field component in the Z direction) is small. . In this region, the magnetoelectric conversion elements 20A and 20B are arranged in such a posture that the sensitivity influence axes S2A and S2B are parallel to the first symmetry axis L1 (Z direction). As a result, the magnetic field components of the sensitivity-affected axes S2A and S2B are reduced, so that a decrease in linearity of detection sensitivity can be suppressed.

  The magnetoelectric conversion elements 20A and 20B are positions where the sensitivity influence axes S2A and S2B overlap the first symmetry axis L1, and the magnetic field component parallel to the first symmetry axis L1 (magnetic field component in the Z direction) is minimized. Placed in position. That is, the magnetoelectric conversion elements 20A and 20B are respectively arranged on the first symmetry axis L1 and at an appropriate distance from the conductive member 10B. By disposing the magnetoelectric conversion elements 20A and 20B at this position, the magnetic field components of the sensitivity affecting axes S2A and S2B can be minimized.

  Furthermore, the magnetoelectric conversion elements 20A and 20B are viewed from the direction parallel to the first symmetry axis L1 (Z direction), and the center of the grooves 13A and 13B in the extending direction (Y direction) of the conductive member 10B (region in FIG. 8). Arranged at the center of AR2. Near the ends of the grooves 13A and 13B, the symmetry of the magnetic field in the Y direction is disturbed, so that a magnetic field component in the Z direction is likely to be generated. At the center of the grooves 13A and 13B farthest from both ends of the grooves 13A and 13B, the influence of this symmetry disturbance is alleviated, so that the magnetic field component in the Z direction parallel to the sensitivity affecting axes S2A and S2B is suppressed. Therefore, by arranging the sensitivity influence axes S2A and S2B at this position, the magnetic field components of the sensitivity influence axes S2A and S2B can be further reduced.

  The magnetoelectric conversion element 20A and the magnetoelectric conversion element 20B are arranged at positions facing each other across the grooves 13A and 13B of the conductive member 10B. For example, as shown in FIG. 9, it is arranged on the common first symmetry axis L1 and at a position away from the conductive member 10B by a substantially equal distance. Since the cross section of the conductive member 10B has a line-symmetric shape with respect to the second symmetry axis L2, the magnitudes of the induced magnetic fields of the detected currents in the magnetoelectric conversion element 20A and the magnetoelectric conversion element 20B are substantially equal.

  FIG. 11 is a diagram illustrating an example of a result of obtaining the direction of the induced magnetic field in the current sensor 1B by simulation. Comparing FIG. 11 and FIG. 14, in the simulation result shown in FIG. 11, the direction of the magnetic field near the center in the width direction of the conductive member 10B is closer to the horizontal.

FIG. 12 is a graph showing an example of the result of obtaining the strength of the induced magnetic field in the current sensor 1 by simulation. Similar to the simulation result shown in FIG. 6, the position of 20 [mm] on the horizontal axis corresponds to the center in the width direction of the conductive member 10B.
12 and FIG. 15, in the simulation result of FIG. 12, the magnetic field component Hz in the Z direction is substantially zero near the center in the width direction of the conductive member 10, and this zero range is near the center in the width direction. About 1 mm. That is, the range in which the magnetic field component Hz in the Z direction is minimized is much wider than in the past.

  As described above, in the current sensor 1B according to the present embodiment, the conductive member 10B extends linearly in the direction in which the current to be detected flows, and the cross section perpendicular to the extending direction is line symmetrical. have. Further, grooves 13A and 13B through which the first axis of symmetry L1 passes are provided on the surface of the conductive member 10B. Therefore, in the region outside the grooves 13A and 13B and overlapping with the grooves 13A and 13B when viewed from the direction parallel to the first symmetry axis L1, no current flows in the spaces of the grooves 13A and 13B. The magnetic field component (magnetic field component in the Z direction) in the direction parallel to the first axis of symmetry L1 passing through the grooves 13A and 13B is reduced. Accordingly, the magnetoelectric conversion elements 20A and 20B are arranged in this region, and the sensitivity influencing axes S2A and S2B are arranged such that the sensitivity influencing axes S2A and S2B are parallel to the first symmetry axis L1 (Z direction). The magnetic field component of S2B is reduced, and it is possible to effectively suppress a decrease in detection sensitivity linearity.

  As mentioned above, although several embodiment of this invention was described, this invention is not limited to embodiment mentioned above, Various modifications are included.

  In the above-described embodiment, the sensitivity axes (S1A, S1B) of the two magnetoelectric transducers (20A, 20B) are directed in the same direction, and the sensitivity influence axes (S2A, S2B) are also directed in the same direction. However, the present invention is not limited to this. In another embodiment of the present invention, the sensitivity axes (S1A, S1B) of the two magnetoelectric transducers (20A, 20B) are directed in opposite directions, and the sensitivity influence axes (S2A, S2B) are also directed in opposite directions. It's okay. In this case, the computing unit 50 computes the detected current value according to the sum of the output signals of the two magnetoelectric transducers (20A, 20B). As a result, a detection value corresponding to the current to be detected can be obtained, and an error in the detection value due to the external magnetic field can be canceled by calculating the sum.

  In the embodiment described above, an example in which a current sensor is configured using two magnetoelectric conversion elements 20A and 20B has been described, but the number of magnetoelectric conversion elements may be one or three or more.

  In the embodiment described above, the grooves 13A and 13B are rectangular, but may be trapezoidal.

DESCRIPTION OF SYMBOLS 1,1A, 1B ... Current sensor 10, 10A, 10B ... Conductive member, 11 ... 1st conductive part, 12 ... 2nd conductive part, 5, 6, 7 ... Air gap, 13A, 13B ... Groove, 20A, 20B ... Magnetoelectric conversion element, 30 ... circuit board, 31 ... first arm, 32 ... second arm, 40A, 40B ... magnetic shield, 50 ... arithmetic unit, S1A, S1B ... sensitivity axis, S2A, S2B ... sensitivity influence axis, L1 ... first symmetry axis, L2 ... second symmetry axis.

Claims (15)

At least one magnetoresistive element having a sensitivity axis that maximizes the magnetic field detection sensitivity and a sensitivity influence axis that affects the magnetic field detection sensitivity;
A conductive member extending linearly in the direction in which the current to be detected flows, and having a cross section perpendicular to the extending direction and a line symmetric shape with respect to a virtual first symmetry axis;
The conductive member includes a first conductive portion and a second conductive portion that are spaced apart from each other with a gap through which the first axis of symmetry passes, and the shunt currents of the detected current flow in the same direction,
The magnetoresistive element is in a posture before Symbol sensitivity effect axis is parallel to the first axis of symmetry, an outer region of the gap, the viewed from the first axis of symmetry parallel to direction A current sensor characterized in that it is arranged in a region that overlaps with the air gap . The magnetoresistive effect element is arranged at a position where the sensitivity influence axis overlaps the first symmetry axis and a magnetic field component parallel to the sensitivity influence axis is minimized. The current sensor according to 1. The current sensor according to claim 1, wherein the magnetoresistive element is disposed at a center of the gap in the extending direction when viewed from a direction parallel to the first symmetry axis. Cross sections of the first conductive portion and the second conductive portion in the extending direction have a shape that is line symmetric with respect to a second symmetry axis that is orthogonal to the first symmetry axis;
A pair of magnetoresistive elements disposed at positions facing each other across the gap in a direction parallel to the first symmetry axis;
The current sensor according to any one of claims 1 to 3, further comprising a calculation unit that calculates a detected current value based on output signals of the pair of magnetoresistive elements. A circuit board disposed along a plane orthogonal to the extending direction of the conductive member;
The circuit board includes a first arm portion and a second arm portion facing each other across the gap of the conductive member,
One of the pair of magnetoresistive elements is attached to the first arm,
The current sensor according to claim 4, wherein the other of the pair of magnetoresistive elements is attached to the second arm portion. 6. The current sensor according to claim 4, further comprising a pair of magnetic shields disposed at positions facing each other with the pair of magnetoresistive elements interposed therebetween. The first conductive part and the second conductive part have a rectangular cross section perpendicular to the extending direction,
The current sensor according to claim 1, wherein one side surface of the first conductive portion and one side surface of the second conductive portion that form the gap are parallel to each other. At least one magnetoresistive element having a sensitivity axis that maximizes the magnetic field detection sensitivity and a sensitivity influence axis that affects the magnetic field detection sensitivity;
A conductive member extending linearly in the direction in which the current to be detected flows, and having a cross section perpendicular to the extending direction and a line symmetric shape with respect to a virtual first symmetry axis;
The conductive member has a groove that passes through the first axis of symmetry and is recessed in the direction of the first axis of symmetry;
The magnetoresistive element is in a posture before Symbol sensitivity effect axis is parallel to the first axis of symmetry, wherein a region outside the groove, the viewed from the first axis of symmetry parallel to direction A current sensor characterized by being arranged in a region overlapping with a groove . The magnetoresistive effect element is arranged at a position where the sensitivity influence axis overlaps the first symmetry axis and a magnetic field component parallel to the sensitivity influence axis is minimized. The current sensor according to claim 8. 10. The current sensor according to claim 8, wherein the magnetoresistive element is arranged at a center in the extending direction of the groove when viewed from a direction parallel to the first symmetry axis. The cross section of the conductive member in the extending direction has a shape that is line symmetric with respect to a second symmetry axis that is orthogonal to the first symmetry axis;
The conductive member has a pair of grooves extending in the extending direction,
A pair of magnetoresistive elements disposed at positions facing each other across the pair of grooves in a direction parallel to the first symmetry axis;
The current sensor according to any one of claims 8 to 10, further comprising: an arithmetic unit that calculates a detected current value based on output signals of the pair of magnetoresistive elements. A circuit board disposed along a plane orthogonal to the extending direction of the conductive member;
The circuit board includes a first arm portion and a second arm portion facing each other across the pair of grooves,
One of the pair of magnetoresistive elements is attached to the first arm,
The current sensor according to claim 11, wherein the other of the pair of magnetoresistive elements is attached to the second arm portion. The current sensor according to claim 11, further comprising a pair of magnetic shields disposed at positions facing each other with the pair of magnetoresistive elements interposed therebetween. The groove is formed in a rectangular or trapezoidal cross section perpendicular to the extending direction.
The current sensor according to claim 8, wherein the current sensor is a current sensor. The magnetoresistive element is disposed at a position where a magnetic flux line generated by the detected current is flattened.
The current sensor according to claim 1, wherein the current sensor is a current sensor.