JP2013117447A - Current sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current sensor which suppresses reduction in current detection accuracy.SOLUTION: A current sensor which measures target current on the basis of variation of an electrical signal from a magneto-electric transducer (20) due to a magnetic field induced by the target current includes; a sensor substrate (10); the magneto-electric transducer (20) which is formed on one surface (10a) of the sensor substrate (10) and converts a magnetic field applied thereto into an electrical signal; and a magnetic shield section (30) which magnetically shields the internal section from external space by surrounding the sensor substrate (10) and a target conductor (90) through which the target current flows. The magnetic shield section (30) has at least one air gap (33) formed thereon and is provided with suppression means for preventing either or both of an air-gap magnetic field generated in the air gap (33) and an external magnetic field generated outside the magnetic shield section (30) from reaching the magneto-electric transducer (20).

Description

  The present invention relates to a current sensor that measures a current to be measured based on a change in an output signal of a magnetoelectric transducer due to a magnetic field generated from the current to be measured.

  Conventionally, for example, as disclosed in Patent Document 1, a current sensor including a bus bar through which a current to be measured flows, a magnetic detection element fixedly arranged with respect to the bus bar, and a magnetic shield body that magnetically shields the magnetic detection element is provided. Proposed. The magnetic shield body has an annular enclosure that encloses the bus bar and the magnetic detection element inside, and a gap for suppressing magnetic saturation of the magnetic shield body is formed in the annular enclosure.

JP 2010-2277 A

  As described above, in the current sensor disclosed in Patent Document 1, a gap is formed in the annular enclosure (magnetic shield body). The magnetic flux flowing in the magnetic shield body is released in the above-described gap and forms a magnetic field outside. Therefore, a magnetic field generated in the air gap (hereinafter referred to as an air gap magnetic field) is applied to the magnetic detection element, which may reduce the current detection accuracy. In addition, among the external magnetic field generated outside the magnetic shield body, a magnetic field that is not completely absorbed by the magnetic shield body and is transmitted through the magnetic shield body is applied to the magnetic detection element, thereby reducing current detection accuracy. There is a fear.

  In view of the above problems, an object of the present invention is to provide a current sensor in which a decrease in current detection accuracy is suppressed.

  In order to achieve the above-described object, the invention according to claim 1 is a magneto-electric device in which an output signal varies depending on an applied magnetic field formed on a sensor substrate (10) and one surface (10a) of the sensor substrate (10). A magnetic shield part (30) that magnetically shields the outside and the inside by surrounding both the conversion element (20), the sensor substrate (10), and the measured conductor (90) through which the measured current flows. And a current sensor for measuring the current to be measured based on the fluctuation of the output signal of the magnetoelectric conversion element (20) due to the magnetic field generated by the current to be measured. At least one air gap (33) for suppressing magnetic saturation in the magnetic shield part (30) is formed, and the magnetic shield part (30) has an air gap magnetic field generated in the air gap (33) and a magnetic field. Outside the shield (30) At least one of the Flip external magnetic field, characterized in that the suppression means for suppressing from being applied to the magnetoelectric transducer (20) is formed.

  According to this, it is suppressed by the suppression means that at least one of a gap magnetic field and an external magnetic field is applied to the magnetoelectric conversion element (20). Thereby, the fall of the detection accuracy of an electric current is suppressed.

It is sectional drawing which shows schematic structure of the current sensor which concerns on 1st Embodiment. It is sectional drawing for demonstrating a space | gap magnetic field. It is sectional drawing for demonstrating the magnetic field applied to a magnetoelectric conversion element. It is sectional drawing for demonstrating the air gap magnetic field by an external magnetic field. It is sectional drawing for demonstrating the magnetic field applied to a magnetoelectric conversion element. It is sectional drawing which shows schematic structure of the current sensor which concerns on 2nd Embodiment. It is sectional drawing which shows schematic structure of the current sensor which concerns on 3rd Embodiment. It is sectional drawing which shows the modification of a convex part. It is sectional drawing which shows the modification of a convex part. It is sectional drawing which shows schematic structure of the current sensor which concerns on 4th Embodiment. It is sectional drawing which shows the modification of a current sensor. It is sectional drawing which shows the modification of a current sensor. It is sectional drawing which shows the modification of a current sensor. It is sectional drawing which shows the modification of a current sensor. It is sectional drawing which shows the modification of a current sensor. It is sectional drawing which shows the modification of a current sensor. It is sectional drawing which shows the modification of a current sensor. It is sectional drawing which shows the modification of a current sensor.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
The present embodiment mainly aims to provide a current sensor in which application of an external magnetic field to a sensor substrate is suppressed.

[1]
A sensor substrate (10);
A magnetoelectric transducer (20) formed on one surface (10a) of the sensor substrate (10), the output signal of which varies with an applied magnetic field;
A magnetic shield portion (30) that magnetically shields the outside and the inside by surrounding the sensor substrate (10) and the conductor to be measured (90) through which the current to be measured flows;
A current sensor for measuring the current to be measured based on a change in an output signal of the magnetoelectric transducer (20) due to a magnetic field generated by the current to be measured;
In the magnetic shield part (30), at least one air gap (33) for suppressing magnetic saturation in the magnetic shield part (30) is formed,
The magnetic shield part (30) has at least one of a gap magnetic field generated in the gap (33) and an external magnetic field generated outside the magnetic shield part (30). The current sensor is characterized in that a suppression means for suppressing the application to the above is formed.

[1-1]
The magnetic shield part (30) includes a first part (31) and a second part (32) having a higher magnetic permeability than the first part (31), and the gap (33) includes the first part (31). The current sensor according to [1], wherein the current sensor is formed by two parts (32), and the suppression means includes the second part (32).

  The part that forms the air gap (33) constantly emits the magnetic field absorbed in the magnetic shield part (30), and therefore has a property that the magnetic saturation is difficult. Moreover, when the magnetic resistance of the magnetic shield part (30) is low, the magnetic shield part (30) is likely to be magnetically saturated, but the shielding performance for shielding an external magnetic field is improved. On the other hand, in [1-1], the air gap (33) is constituted by the second part (32) having a higher magnetic permeability (lower magnetic resistance) than the first part (31). Thereby, the shielding property which shields an external magnetic field is improved, suppressing the magnetic saturation of a magnetic shield part (30). As a result, application of an external magnetic field to the sensor substrate (10) is suppressed.

[1-2]
The magnetoelectric conversion element (20) has a property that an output signal varies due to an applied magnetic field along one surface (10a) of the sensor substrate (10),
The one surface (10a) is parallel to the xy plane defined by the x direction and the y direction that are orthogonal to each other, and is orthogonal to the z direction,
An outline formed by an inner wall surface of the magnetic shield part (30) divided by an xz plane defined by the x direction and the z direction passing through the one surface (10a) is along the x direction, In addition, a symmetric structure is formed through a reference line (BL) passing through the one surface (10a),
The height position of at least a part of the gap (33) in the z direction is the same as the height position of the sensor substrate (10) [1] or [1-1 ] The current sensor as described in.

  The magnetic flux flowing in the magnetic shield part (30) is released in the air gap (33) and forms a magnetic field outside. The magnetic field (gap magnetic field) generated in the air gap (33) varies depending on the shape of the magnetic shield part (30). On the other hand, in [1-2], the outline formed by the inner wall surface of the magnetic shield part (30) divided by the xz plane passing through one surface (10a) of the magnetoelectric conversion element (20) is a reference. A symmetrical structure is formed via the line (BL). And a space | gap (33) is formed in the site | part which comprises a symmetrical structure in a magnetic shield part (30), and the height position of the space | gap (33) in the z direction and the height position of a sensor board | substrate (10) are It is the same. Accordingly, the air gap magnetic field in the region surrounded by the portion having the symmetrical structure is symmetric through the reference line (BL), and the direction at the reference line (BL) is orthogonal to the reference line (BL). Therefore, the air gap magnetic field is applied perpendicularly to the magnetoelectric conversion element (20). The magnetoelectric conversion element (20) according to the present invention has the property that the output signal varies depending on the applied magnetic field along one surface (10a). Therefore, the output signal of the magnetoelectric conversion element (20) hardly fluctuates with respect to the air gap magnetic field. As described above, since the fluctuation of the output signal of the magnetoelectric conversion element (20) due to the air gap magnetic field is suppressed, a decrease in current detection accuracy is suppressed.

[1-3]
The current sensor according to [1-2], wherein a height position of all the gaps (33) in the z direction is the same as a height position of the sensor substrate (10).

  Unlike the configuration described in [1-3], in the configuration in which the height position of a part of the gap in the z direction is the same as the height position of the sensor substrate, the height is the same as that of the sensor substrate (10). A gap magnetic field is also formed from gaps (33) at different positions. Since the direction of the air gap magnetic field at the reference line (BL) is not always perpendicular to the reference line (BL), the air gap magnetic field in the direction along the one surface (10a) with respect to the magnetoelectric transducer (20). May be applied. When such a gap magnetic field is applied, the output signal of the magnetoelectric conversion element (20) fluctuates due to the gap magnetic field, and the current detection accuracy may be reduced. Therefore, as described in [1-3], a configuration in which the height position of all the gaps (33) in the z direction is the same as the height position of the sensor substrate (10) is preferable. In this case, the gap magnetic field in the direction along the one surface (10a) is suppressed from being applied to the magnetoelectric conversion element (20), and a decrease in current detection accuracy is suppressed.

[1-4]
[1-2] or [1-3], wherein the height position of the center of the gap (33) and the height position of the one surface (10a) in the z direction are the same. Current sensor.

  The air gap magnetic field is formed concentrically and elliptically outward from the center of the air gap (33). Therefore, as described in [1-4], it is preferable that the height position of the center of the gap (33) and the height position of the one surface (10a) in the z direction are the same. According to this, compared with the configuration in which the height position of the center of the gap in the z direction is different from the height position of the formation surface, the orientation at the reference line (BL) in the gap magnetic field is the reference line (BL). Closer to the direction perpendicular to Thereby, it is suppressed that the air gap magnetic field in the direction along the one surface (10a) is applied to the magnetoelectric conversion element (20), and a decrease in current detection accuracy is suppressed.

[1-5]
The sensor substrate (10) is located at the center of the magnetic shield part (30),
The current sensor according to any one of [1-2] to [1-4], wherein the two gaps (33) are arranged to face each other with the sensor substrate (10) interposed therebetween.

  The magnetic field generated from the conductor to be measured (90) propagates in the magnetic shield part (30), is then collected by the magnetic shield part (30), and rotates in the magnetic shield part (30) in one direction. Therefore, the direction of the air gap magnetic field generated in each of the air gaps (33) opposed to each other via the sensor substrate (10) is reversed, and the sensor substrate (10) positioned at the center of the magnetic shield part (30) is opposite to the sensor substrate (10). A gap magnetic field having the same direction and the same strength is applied. As a result, the air gap magnetic field is canceled in the sensor substrate (10). As described above, since the gap magnetic field in the direction along the one surface (10a) is suppressed from being applied to the magnetoelectric conversion element (20), a decrease in current detection accuracy is suppressed.

  In the case of the configuration described in [1-1], since the magnetic resistance of the magnetic shield part (30) is low, the air gap magnetic field increases. Therefore, when the configuration described in [1-2] to [1-5] is applied to the configuration described in [1-1], the influence of the gap magnetic field on the magnetoelectric conversion element (20) is suppressed. preferable.

  Hereinafter, the first embodiment will be described in detail with reference to FIGS. FIG. 1 is a cross-sectional view showing a schematic configuration of the current sensor according to the first embodiment. FIG. 2 is a cross-sectional view for explaining the air gap magnetic field. FIG. 3 is a cross-sectional view for explaining the magnetic field applied to the magnetoresistive effect element. FIG. 4 is a cross-sectional view for explaining a gap magnetic field due to an external magnetic field. FIG. 5 is a cross-sectional view for explaining a magnetic field applied to the magnetoresistive element. 2 and 4, the current sensor 100 is simplified in order to clarify the air gap magnetic field. In the following, along the formation surface 10a described later, directions orthogonal to each other are indicated as an x direction and ay direction, and a direction orthogonal to the formation surface 10a is indicated as a z direction.

  As shown in FIG. 1, the current sensor 100 includes, as main parts, a sensor substrate 10, a magnetoelectric conversion element 20 formed on the sensor substrate 10, and a sensor substrate 10 and a measured conductor 90 through which a measured current flows. And a magnetic shield part 30 surrounding the periphery. The current sensor 100 measures the current to be measured based on a change in the output signal of the magnetoelectric transducer 20 due to a magnetic field generated from the current to be measured (hereinafter referred to as a measured magnetic field). The current sensor 100 according to the present embodiment includes a bias magnet 40, a circuit board 50, a support board 60, a mold resin 70, and a spacer 80 in addition to the constituent elements 10 to 30 described above.

  The sensor substrate 10 is a semiconductor substrate, and a magnetoelectric conversion element 20 is formed on one surface 10a thereof (hereinafter, the one surface 10a is referred to as a formation surface 10a). As shown in FIG. 1, the sensor substrate 10 is mounted on the support substrate 60 with the back surface of the formation surface 10a as the mounting surface. The sensor board 10 is electrically connected to the circuit board 50 through the wire 11, and an electric signal including a change in the output signal of the magnetoelectric transducer 20 is output to the circuit board 50 through the wire 11. The

  The magnetoelectric conversion element 20 according to the present embodiment is a magnetoresistive effect element whose resistance value varies depending on the applied magnetic field, and has a property that the resistance value varies only by the applied magnetic field along the formation surface 10a. Although not shown, the magnetoelectric conversion element 20 includes a free layer whose magnetization direction changes according to the applied magnetic field along the formation surface 10a, a nonmagnetic intermediate layer, a pinned layer whose magnetization direction is fixed, and the magnetization of the pinned layer. A magnet layer for fixing the direction is sequentially laminated. The intermediate layer according to the present embodiment has an insulating property, and the magnetoelectric conversion element 20 is a tunnel magnetoresistive effect element. When a voltage is applied between the free layer and the fixed layer, a current (tunnel current) flows through an intermediate layer between the free layer and the fixed layer due to the tunnel effect. The ease of flow of the tunnel current depends on the magnetization directions of the free layer and the fixed layer, and flows most easily when the magnetization directions of the free layer and the fixed layer are parallel to each other, and hardly flows when the magnetization directions are antiparallel. Therefore, the resistance value of the magnetoelectric conversion element 20 changes the smallest when the magnetization directions of the free layer and the fixed layer are parallel, and the resistance value changes the most when the magnetization direction is antiparallel.

  In the present embodiment, a half bridge circuit is configured by the two magnetoelectric conversion elements 20, and a full bridge circuit is configured by the two half bridge circuits. The magnetization directions of the fixed layers of the two magnetoelectric conversion elements 20 constituting the half bridge circuit are antiparallel, and the resistance values of the two magnetoelectric conversion elements 20 change in opposite directions. That is, when the resistance value of one of the two magnetoelectric transducers 20 is reduced, the resistance value of the other is increased. The difference between the midpoint potentials of the two half-bridge circuits constituting the full-bridge circuit is output to the circuit board 50 via the wire 11.

  The magnetic shield part 30 is made of a material having high magnetic permeability and has a cylindrical shape. The components 10, 20, 40 to 80 of the current sensor 100 and the conductor to be measured 90 are arranged inside, and serve to magnetically shield the inside and the outside. As shown by a solid line in FIG. 2, the magnetic field to be measured generated from the conductor 90 to be measured is propagated through the magnetic shield part 30 and then collected in the magnetic shield part 30, and the magnetic shield part 30 is unidirectionally moved in one direction. Rotate. Further, as indicated by a solid line in FIG. 4, the external magnetic field collected by the magnetic shield part 30 flows in both directions.

  The magnetic shield part 30 is formed with a gap 33 for suppressing magnetic saturation in the magnetic shield part 30, and the magnetic flux flowing in the magnetic shield part 30 is released in the gap 33. 2 and 4, the magnetic flux emitted from the gap 33 forms a magnetic field (hereinafter referred to as a gap magnetic field) outside. In the present embodiment, two air gaps 33 are formed in the magnetic shield part 30, and two air gap magnetic fields are applied to the magnetoelectric conversion element 20.

  The bias magnet 40 is a permanent magnet and functions to apply a bias magnetic field to the free layer. The initial value (zero point) of the magnetization direction of the free layer is determined by the bias magnetic field. The bias magnet 40 faces the sensor substrate 10 with the support substrate 60 interposed therebetween.

  The circuit board 50 is formed by forming a circuit for processing an output signal of the magnetoelectric conversion element 20 on a semiconductor substrate. The circuit board 50 functions to calculate the current value of the current to be measured based on the output signal of the full bridge circuit configured by the magnetoelectric transducer 20. The circuit board 50 is mounted on the support board 60 along with the sensor board 10.

  The support substrate 60 is made of a nonmagnetic material. The mold resin 70 integrally fixes and protects the sensor substrate 10, the bias magnet 40, the circuit substrate 50, and the support substrate 60. The spacer 80 fixes the sensor substrate 10, the bias magnet 40, the circuit substrate 50, and the support substrate 60 covered with the measured conductor 90 and the mold resin 70 in the magnetic shield part 30. The mold resin 70 and the spacer 80 are made of a material having nonmagnetic properties and insulating properties. As shown in FIG. 2, the current to be measured flows in the y direction.

  Next, feature points of the current sensor 100 according to the present embodiment will be described. The magnetic shield part 30 according to the present embodiment includes a first part 31 and a second part 32 having a higher magnetic permeability than the first part 31, and the first part 31 and the second part 32 are made of sintered material. It is joined by the diffusion technique. The gap 33 is formed by the second portion 32.

  Further, as shown in FIGS. 1 and 2, the inner wall surface of the magnetic shield part 30 divided by the xz plane passing through the formation surface 10a (the magnetoelectric conversion element 20) and defined by the x direction and the z direction. The contour line and the cross-sectional shape formed have a symmetric structure along a reference line BL (broken line shown in the drawing) along the x direction and passing through the formation surface 10a. And the space | gap 33 is formed in the site | part which comprises the symmetrical structure in the magnetic shield part 30, and the height position of the space | gap 33 and the height position of the sensor board | substrate 10 in the z direction are the same.

  In the present embodiment, all the height positions of the gap 33 and the height position of the sensor substrate 10 are the same, and further, the height position of the center of the gap 33 and the height position of the formation surface 10a. Are the same. Further, the sensor substrate 10 is located at the center of a portion forming a symmetrical structure in the magnetic shield part 30, and the two gaps 33 are arranged to face each other with the sensor substrate 10 interposed therebetween.

  Next, the function and effect of the current sensor 100 according to this embodiment will be described. As described above, the magnetic field to be measured propagates in the magnetic shield part 30, is then collected in the magnetic shield part 30, and rotates in the magnetic shield part 30 in one direction. And the magnetic flux which flows through the inside of the magnetic shield part 30 is discharged | emitted in the space | gap 33, and a space | gap magnetic field is formed outside.

  As described above, the portion forming the air gap 33 constantly emits the magnetic field absorbed in the magnetic shield part 30 and thus has a property that the magnetic saturation is difficult. Moreover, if the magnetic resistance of the magnetic shield part 30 is low, the magnetic shield part 30 is likely to be magnetically saturated, but the shielding performance for shielding an external magnetic field is improved. On the other hand, in this embodiment, the air gap 33 is constituted by the second portion 32 having a higher magnetic permeability (lower magnetic resistance) than the first portion 31. Thereby, the shielding property which shields an external magnetic field is improved, suppressing the magnetic saturation of the magnetic shield part 30. FIG. As a result, application of an external magnetic field to the sensor substrate is suppressed.

  By the way, although the air gap magnetic field varies depending on the shape of the magnetic shield part 30, in the present embodiment, the air gap 33 is formed in a part of the magnetic shield part 30 having a symmetrical structure via the reference line BL. Therefore, the gap magnetic field in the region surrounded by the portion having the symmetrical structure is symmetric through the reference line BL, and the direction at the reference line BL is the direction orthogonal to the reference line BL.

  On the other hand, in the present embodiment, the height position of the gap 33 and the height position of the sensor substrate 10 in the z direction are the same. Therefore, as shown in FIGS. 3 and 5, the air gap magnetic field is applied perpendicularly to the magnetoelectric conversion element 20. As described above, the magnetoelectric conversion element 20 has a property that the resistance value varies depending on the applied magnetic field along the formation surface 10a. Therefore, the resistance value of the magnetoelectric conversion element 20 is unlikely to fluctuate with respect to the air gap magnetic field. As described above, since the fluctuation of the resistance value of the magnetoelectric conversion element 20 due to the air gap magnetic field is suppressed, a decrease in current detection accuracy is suppressed.

  In the case where the height position of a part of the gap in the z direction is the same as the height position of the sensor substrate, a gap magnetic field is also formed from a gap having a height position different from that of the sensor substrate. Since the direction of the air gap magnetic field at the reference line BL is not always perpendicular to the reference line BL, the air gap magnetic field in the direction along the formation surface 10a may be applied to the magnetoelectric transducer 20. . When such a gap magnetic field is applied, the resistance value of the magnetoelectric conversion element 20 varies due to the gap magnetic field, and the current detection accuracy may be reduced.

  On the other hand, in the present embodiment, the height position of all the gaps 33 and the height position of the sensor substrate 10 in the z direction are the same. In this case, the gap magnetic field in the direction along the formation surface 10a is suppressed from being applied to the magnetoelectric conversion element 20, and a decrease in current detection accuracy is suppressed.

  As shown in FIG. 2, the air gap magnetic field is formed concentrically and elliptically outward from the center of the air gap 33. In contrast, in the present embodiment, the height position of the center of the gap 33 and the height position of the formation surface 10a in the z direction are the same. According to this, the orientation of the air gap magnetic field at the reference line BL is orthogonal to the reference line BL, compared to a configuration in which the height position of the center of the air gap 33 and the height position of the formation surface 10a are different in the z direction. The closer you are to Thereby, it is suppressed that the air gap magnetic field in the direction along the formation surface 10a is applied to the magnetoelectric conversion element 20, and a decrease in current detection accuracy is suppressed.

  The sensor substrate 10 is located at the center of a portion forming a symmetric structure in the magnetic shield part 30, and two gaps 33 are arranged to face each other with the sensor substrate 10 interposed therebetween. As described above, the magnetic field to be measured propagates in the magnetic shield part 30, is then collected by the magnetic shield part 30, and rotates in the magnetic shield part 30 in one direction. Therefore, as shown in FIGS. 2 and 3, the direction of the air gap magnetic field generated in each of the air gaps 33 facing each other via the sensor substrate 10 is reversed, and the sensor substrate 10 located at the center of the magnetic shield part 30 has The gap magnetic field is applied in the opposite direction and with the same strength. As a result, the air gap magnetic field is canceled in the sensor substrate 10. Thus, since the gap magnetic field in the direction along the formation surface 10a is suppressed to the magnetoelectric conversion element 20, a decrease in current detection accuracy is suppressed.

  As shown in FIG. 4, the external magnetic field collected by the magnetic shield part 30 flows not only in one direction in the magnetic shield part 30 but also in both directions. Therefore, as shown in FIG. 5, the direction of the air gap magnetic field caused by the external magnetic field generated in each of the air gaps 33 arranged to face each other via the sensor substrate 10 is the same, and the sensor located at the center of the magnetic shield part 30 A gap magnetic field having the same direction and the same strength is applied to the substrate 10. However, as described above, the magnetoelectric conversion element 20 has a property that the resistance value varies depending on the applied magnetic field along the formation surface 10a. Accordingly, the resistance value of the magnetoelectric conversion element 20 hardly fluctuates with respect to the air gap magnetic field caused by the external magnetic field, and the fluctuation of the resistance value of the magnetoelectric conversion element 20 is suppressed, so that a decrease in current detection accuracy is suppressed. .

  A circuit board 50 is provided in the magnetic shield part 30. According to this, an increase in the physique of the current sensor 100 is suppressed as compared with the configuration in which the circuit board is provided outside the magnetic shield part. Further, application of an external magnetic field to the circuit board 50 is suppressed.

  The sensor substrate 10, the bias magnet 40, the circuit substrate 50, and the support substrate 60 are integrally fixed by the mold resin 70 and are covered and protected. According to this, it is suppressed that the site | part which is not intended is electrically connected through the foreign material which has electroconductivity. Further, the mechanical connection strength of the sensor substrate 10, the bias magnet 40, the circuit substrate 50, and the support substrate 60 is improved.

  The measured conductor 90, the sensor substrate 10 covered with the mold resin 70, the bias magnet 40, the circuit substrate 50, and the support substrate 60 are fixed in the magnetic shield part 30 via the spacer 80. According to this, compared with the configuration in which the conductor under measurement and the sensor substrate are each independently fixed to the magnetic shield part, the relative position fluctuation between the conductor under measurement 90 and the sensor substrate 10 is suppressed. Thereby, the fall of the detection accuracy of the electric current by the fluctuation | variation of a relative position is suppressed.

  The two magnetoelectric conversion elements 20 constitute a half bridge circuit, and the two half bridge circuits constitute a full bridge circuit. Then, the difference between the midpoint potentials of the two half bridge circuits constituting the full bridge circuit is output to the circuit board 50. According to this, compared with the structure which detects an electric current based on the midpoint potential of one half bridge circuit, the electric current detection accuracy is improved.

  In the present embodiment, an initial value (zero point) of the magnetization direction of the free layer is determined by applying a bias magnetic field generated from the bias magnet 40 to the free layer. On the other hand, in order to determine the application direction of the air gap magnetic field applied to the magnetoresistive effect element, a configuration in which a magnetic flux collecting core is arranged in the magnetic shield part is also conceivable. However, in the case of this configuration, the above-described bias magnetic field passes through the magnetic flux collecting core, so that the zero point in the magnetization direction of the free layer cannot be determined. Therefore, the current sensor 100 according to the present embodiment is fundamentally different from the current sensor in which the magnetic flux collecting core is provided in the magnetic shield part.

(Second Embodiment)
The present embodiment mainly aims to provide a current sensor in which application of an external magnetic field to a sensor substrate is suppressed.

[2-1]
Projections (34) facing each other are formed on the outer surface of the magnetic shield part (30),
The opposing surfaces of the protrusion (34) facing each other are continuous with the wall surface forming the open end of the gap (33),
The current sensor according to [1] or [1-1], wherein the suppression unit includes the protrusion (34).

  The part that forms the air gap (33) constantly emits the magnetic field absorbed in the magnetic shield part (30), and therefore has a property that the magnetic saturation is difficult. Moreover, when the magnetic resistance of the magnetic shield part (30) is low, the magnetic shield part (30) is likely to be magnetically saturated, but the shielding performance for shielding an external magnetic field is improved. On the other hand, in [2-1], the wall surface constituting the opening end of the air gap (33) and the facing surface are continuous, and the protruding portions (34) facing each other are formed on the outer surface of the magnetic shield portion (30). Yes. According to this, since the magnetic field is also emitted from the protrusion (34), the surface area of the end surface forming the gap (33) is substantially increased. The air gap magnetic field is perpendicular to the end face, and the magnetic resistance is in inverse proportion to the area perpendicular to the air gap magnetic field. Therefore, according to the above configuration, the magnetic resistance of the portion forming the air gap (33) is reduced, so that the shielding property for shielding the external magnetic field can be improved while suppressing the magnetic saturation of the magnetic shield part (30). As a result, application of an external magnetic field to the sensor substrate (10) is suppressed.

[2-2]
The magnetic shield part (30) includes a first part (31) and a second part (32) having a higher magnetic permeability than the first part (31),
The current sensor according to [2-1], wherein the protrusion (34) includes the second part (32).

  According to this, compared with the structure which a projection part consists of a 1st site | part, the shielding performance which shields an external magnetic field can be improved. As a result, application of an external magnetic field to the sensor substrate (10) is suppressed.

[2-3]
The magnetoelectric conversion element (20) has a property that an output signal varies due to an applied magnetic field along one surface (10a) of the sensor substrate (10),
The one surface (10a) is parallel to the xy plane defined by the x direction and the y direction that are orthogonal to each other, and is orthogonal to the z direction,
An outline formed by an inner wall surface of the magnetic shield part (30) divided by an xz plane defined by the x direction and the z direction passing through the one surface (10a) is along the x direction, In addition, a symmetric structure is formed through a reference line (BL) passing through the one surface (10a),
[2-1] or [2], wherein a height position of at least a part of the gap (33) in the z direction is the same as a height position of the sensor substrate (10). -2].

[2-4]
The current sensor according to [2-3], wherein a height position of all the gaps (33) and a height position of the sensor substrate (10) in the z direction are the same.

[2-5]
[2-3] or [2-4], wherein the height position of the center of the gap (33) and the height position of the one surface (10a) in the z direction are the same. Current sensor.

[2-6]
The sensor substrate (10) is located at the center of the magnetic shield part (30),
The current sensor according to any one of [2-3] to [2-5], wherein the two gaps (33) are arranged to face each other via the sensor substrate (10).

  The operational effects achieved by the configurations described in [2-3] to [2-6] are the same as the operational effects exhibited by the configurations described in [1-2] to [1-5] described in the first embodiment. Since it is equivalent, the description is omitted. In the case of the configurations described in [2-1] and [2-2], the magnetic resistance of the magnetic shield part (30) is low, so that the air gap magnetic field increases. Therefore, when the configuration described in [2-3] to [2-6] is applied to the configuration described in [2-1] and [2-2], the influence of the void magnetic field on the magnetoelectric conversion element (20) is affected. Since it is suppressed, it is especially preferable.

  Hereinafter, a second embodiment will be described with reference to FIG. FIG. 6 is a cross-sectional view illustrating a schematic configuration of the current sensor according to the second embodiment, and corresponds to FIG. 1 illustrated in the first embodiment.

  Since the current sensor 100 according to the second embodiment is often in common with that according to the first embodiment, the detailed description of the common parts will be omitted below, and different parts will be mainly described. In addition, the same code | symbol is provided to the element same as the element shown in 1st Embodiment.

  The current sensor 100 according to the present embodiment is characterized in that a protrusion 34 is formed on the outer surface of the magnetic shield part 30. As shown in FIG. 6, the two protrusions 34 face each other in the z direction, and the facing surfaces of the protrusions 34 are continuous with the opening end of the gap 33.

  The portion forming the air gap 33 constantly emits the magnetic field absorbed in the magnetic shield part 30, and therefore has a property that it is difficult to be magnetically saturated. Moreover, if the magnetic resistance of the magnetic shield part 30 is low, the magnetic shield part 30 is likely to be magnetically saturated, but the shielding performance for shielding an external magnetic field is improved. On the other hand, in the present embodiment, the wall surface constituting the opening end of the air gap 33 and the opposing surface are connected, and the protruding portions 34 facing each other are formed on the outer surface of the magnetic shield portion 30. According to this, since the magnetic field is also emitted from the protrusions 34, the surface area of the end face that forms the gap 33 is substantially increased. The air gap magnetic field is perpendicular to the end face, and the magnetic resistance is in inverse proportion to the area perpendicular to the air gap magnetic field. Therefore, according to the above configuration, the magnetic resistance of the portion forming the gap 33 is reduced, so that the shielding property of shielding the external magnetic field can be improved while suppressing the magnetic saturation of the magnetic shield part 30. As a result, application of an external magnetic field to the sensor substrate is suppressed.

  In the present embodiment, the constituent material of the projecting portion 34 is not particularly limited, but the constituent material includes a second portion 32 having a higher magnetic permeability than the first portion 31 shown in the first embodiment. You can also According to this, compared with the structure which a projection part consists of a 1st site | part, the shielding performance which shields an external magnetic field can be improved. As a result, application of an external magnetic field to the sensor substrate 10 is suppressed.

(Third embodiment)
The present embodiment mainly aims to provide a current sensor in which the application of a gap magnetic field to a sensor substrate is suppressed.

[3-1]
In the magnetic shield part (30), the convex part (35) which protrudes from one said opposing surface toward the other said opposing surface in each of two opposing surfaces which comprise the said space | gap (33) and mutually oppose. And the tips of the two convex portions (35) formed on the two opposing surfaces are opposed to each other,
The tip of the convex portion (35) is located between the inner surface and the outer surface of the magnetic shield portion (30) on the facing surface, or on the outer surface side from the middle,
The current sensor according to [1], [1-1], [2-1], or [2-2], wherein the suppression unit includes the convex portion (35).

  The density distribution of the air gap magnetic field depends on the shape of the opposing surface and the convex portion (35) constituting the air gap (33), and the generation center thereof is located at the tip of the convex portion (35) facing each other. In [3-1], the tip of the convex portion (35) is located in the middle of the facing surface or outside the middle. Therefore, the density distribution of the gap magnetic field formed inside the magnetic shield part (30) is coarser than the density distribution of the gap magnetic field formed outside. According to this, application of the air gap magnetic field to the sensor substrate (10) is suppressed.

[3-2]
The magnetoelectric conversion element (20) has a property that an output signal varies due to an applied magnetic field along one surface (10a) of the sensor substrate (10),
The one surface (10a) is parallel to the xy plane defined by the x direction and the y direction that are orthogonal to each other, and is orthogonal to the z direction,
An outline formed by an inner wall surface of the magnetic shield part (30) divided by an xz plane defined by the x direction and the z direction passing through the one surface (10a) is along the x direction, In addition, a symmetric structure is formed through a reference line (BL) passing through the one surface (10a),
The height position of at least a part of the gap (33) and the height position of the sensor substrate (10) in the z direction are the same as described in [3-1]. Current sensor.

[3-3]
The current sensor according to [3-2], wherein the height position of all the gaps (33) in the z direction is the same as the height position of the sensor substrate (10).

[3-4]
[3-2] or [3-3], wherein the height position of the center of the gap (33) in the z direction is the same as the height position of the one surface (10a). Current sensor.

[3-5]
The sensor substrate (10) is located at the center of the magnetic shield part (30),
The current sensor according to any one of [3-2] to [3-4], wherein the two gaps (33) are arranged to face each other via the sensor substrate (10).

  The effects obtained by the configurations described in [3-2] to [3-5] are the same as the effects provided by the configurations described in [1-2] to [1-5] described in the first embodiment. Since it is equivalent, the description is omitted.

  Hereinafter, a third embodiment will be described with reference to FIG. FIG. 7 is a cross-sectional view showing a schematic configuration of the current sensor according to the third embodiment, and corresponds to FIG. 1 shown in the first embodiment.

  Since the current sensor according to the third embodiment is often in common with those according to the above-described embodiments, the detailed description of the common parts will be omitted below, and different parts will be described mainly. In addition, the same code | symbol is provided to the element same as the element shown by each above-mentioned embodiment.

  The current sensor 100 according to the present embodiment is characterized in that a convex portion 35 is formed on an end surface forming the gap 33. As shown in FIG. 7, the two convex portions 35 oppose each other in the z direction, and their tips are located outside the middle of the end surfaces forming the gap 33.

  The density distribution of the air gap magnetic field depends on the end face constituting the air gap 33 and the shape of the convex portion 35, and the generation center thereof is located at the tip of the convex portion 35 facing each other. In the present embodiment, the tip of the convex portion 35 is located outside the middle of the end surface. Therefore, the density distribution of the air gap magnetic field formed inside the magnetic shield part 30 is coarser than the density distribution of the air gap magnetic field formed outside. According to this, application of the air gap magnetic field to the sensor substrate 10 is suppressed.

  In the present embodiment, as shown in FIG. 7, an example in which the convex portion 35 having a triangular cross section is formed on the end surface is shown. However, the shape of the convex portion 35 is not limited to the above example. For example, as shown in FIG. 8, a quadrangular section can be adopted. FIG. 8 is a cross-sectional view showing a modified example of the convex portion.

  In this embodiment, the example which the front-end | tip of the convex part 35 was located outside the middle of the end surface was shown. However, the position of the tip of the convex portion 35 may be located in the middle of the end face or outside the middle. For example, as shown in FIG. 9, a configuration in which the tip of the convex portion 35 is continuous with the outer surface of the magnetic shield portion 30 can be adopted. FIG. 9 is a cross-sectional view showing a modified example of the convex portion.

(Fourth embodiment)
An object of the present embodiment is to provide a current sensor in which application of an air gap magnetic field to a sensor substrate is suppressed.

[4-1]
One surface (10a) of the sensor substrate (10) is parallel to an xy plane defined by an x direction and a y direction that are orthogonal to each other, and is orthogonal to the z direction,
The magnetic shield part (30) is formed with a first extension part and a second extension part extending in the z direction, and an outer wall surface of the first extension part and an inner wall surface of the second extension part. Are opposed to each other in the x direction, and the gap (33) is formed,
The suppressing means has the first extending portion and the second extending portion,
The current sensor according to [1] or [1-1], wherein the sensor substrate is separated in the z direction from a surface of the first extending portion facing the second extending portion. .

  According to this, the generation center of the air gap magnetic field is located at the center of the two extending portions facing each other, and the density distribution of the air gap magnetic field becomes coarser as the distance from the generation center increases. In [4-1], the sensor substrate (10) is separated in the z direction from the generation center of the air gap magnetic field. Therefore, the application of the air gap magnetic field to the sensor substrate (10) is suppressed as compared with the configuration in which the sensor substrate is located at the same position in the z direction as the generation center of the air gap magnetic field.

  Hereinafter, the fourth embodiment will be described with reference to FIG. FIG. 10 is a cross-sectional view showing a schematic configuration of the current sensor according to the fourth embodiment, and corresponds to FIG. 1 shown in the first embodiment.

  Since the current sensor according to the fourth embodiment is often in common with those according to each of the above-described embodiments, the detailed description of the common parts will be omitted below, and different parts will be mainly described. In addition, the same code | symbol is provided to the element same as the element shown by each above-mentioned embodiment.

  The current sensor 100 according to the present embodiment is characterized by the configuration of the magnetic shield unit 30 and the position of the sensor substrate 10. As shown in FIG. 10, the magnetic shield part 30 includes an upper shield 36 and a lower shield 37, and each of the shields 36 and 37 has a box shape having one opening. The distance between the outer wall surfaces of the side walls of the upper shield 36 is shorter than the distance between the inner wall surfaces of the side walls of the lower shield 37, and the bottom inner surfaces of the shields 36 and 37 face each other. A space for housing the sensor substrate 10 is configured in such a manner that the side wall of the upper shield 36 is disposed therein. The outer surface of the side wall of the upper shield 36 and the inner surface of the side wall of the lower shield 37 are opposed to each other in the direction along the xy plane to form the gap 33. An air gap magnetic field is generated on the opposing surfaces of the shields 36 and 37 constituting the air gap 33. As shown in FIG. 10, the sensor substrate 10 is separated in the z direction from the portion where the air gap magnetic field is generated, and the periphery thereof is surrounded by the upper shield 36. Note that the side walls of the shields 36 and 37 described above correspond to the extending portion described in [4-1].

  The density distribution of the air gap magnetic field becomes coarser as the distance from the opposing surface of the shields 36 and 37, which is the generation center thereof, increases. On the other hand, in the present embodiment, the sensor substrate 10 is separated in the z direction from the generation center of the air gap magnetic field. Therefore, the application of the air gap magnetic field to the sensor substrate 10 is suppressed as compared with the configuration in which the sensor substrate is in the same position in the z direction as the air gap magnetic field generation center.

  In this embodiment, the example in which the magnetic shield part 30 has the upper shield 36 and the lower shield 37 was shown. However, the magnetic shield part 30 shown in FIG. 11 can also achieve the same operational effects as the present embodiment. The magnetic shield portion 30 shown in FIG. 11 includes a bottom portion located on the left side of the paper, two side wall portions extending in the x direction from both end portions of the bottom portion, and two extending in the z direction from the respective end portions of the side wall portions. And the length of the two side wall portions in the x direction is different, and the outer surface of one of the extending portions and the inner surface of the other extending portion are opposed to each other. A gap 33 is formed on the opposing surface of the extended portion, and the sensor substrate 10 is arranged farther in the z direction than the gap 33. FIG. 11 is a cross-sectional view showing a modification of the magnetic shield part.

(Other embodiments)
As shown in FIG. 12, the first embodiment and the second embodiment can be combined. That is, it is possible to adopt a configuration in which the gap 33 is formed by the second portion 32 and the protrusion 34 is formed on the outer surface of the magnetic shield portion 30. As shown in FIG. 13, the protrusion 34 may be formed of the same material as the second part 32. 12 and 13 are cross-sectional views showing modifications of the current sensor.

  As shown in FIG. 14, it is possible to combine the first embodiment and the third embodiment. That is, a configuration in which the convex portion 35 is formed by the second portion 32 can be employed. FIG. 14 is a cross-sectional view showing a modification of the current sensor.

  As shown in FIG. 15, it is possible to combine the first embodiment and the fourth embodiment. That is, a configuration in which the tip of the side wall of the upper shield 36 and the tip of the side wall of the lower shield 37 that form the gap 33 by facing each other in the direction along the xy plane is formed by the second portion 32 is adopted. You can also FIG. 15 is a cross-sectional view showing a modification of the current sensor.

  As shown in FIG. 16, it is also possible to combine the second embodiment and the third embodiment. In other words, it is possible to adopt a configuration in which the convex portion 35 is formed on the opposing surface of the protruding portion 34 that substantially functions as an end surface that forms the gap 33. The apex of the convex portion 35 is located in the middle between the inner surface of the magnetic shield portion 30 and the outer surface of the protruding portion 34 or on the outer side of the middle. FIG. 16 is a cross-sectional view showing a modification of the current sensor.

  As shown in FIG. 17, the first to third embodiments can be combined. That is, the air gap 33 is formed by the second portion 32, and the protrusion 34 is formed on the outer surface of the magnetic shield portion 30, and substantially protrudes from the opposing surface of the protrusion 34 that functions as an end surface forming the air gap 33. A configuration in which the portion 35 is formed may be employed. The apex of the convex portion 35 is located in the middle between the inner surface of the magnetic shield portion 30 and the outer surface of the protruding portion 34 or on the outer side of the middle. As shown in FIG. 18, the protrusion 34 may be formed of the same material as the second part 32. 17 and 18 are cross-sectional views showing modifications of the current sensor.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  In the first to third embodiments, the cross-sectional shape of the magnetic shield part 30 divided by the xz plane passing through the formation surface 10a (magnetoelectric conversion element 20) forms a symmetric structure via the reference line BL. An example is shown. Therefore, the cross-sectional shape of the magnetic shield part 30 divided by the xz plane that does not pass through the formation surface 10a (the magnetoelectric conversion element 20) may not have a symmetric structure with respect to the reference line BL. That is, all of the magnetic shield portions 30 do not have to be symmetric with respect to the reference line BL. Furthermore, the outline of the outer wall surface of the magnetic shield part 30 divided by the xz plane passing through the formation surface 10a (the magnetoelectric conversion element 20) may not have a symmetric structure via the reference line BL. Also by this, the air gap magnetic field in the region surrounded by the portion having the symmetric structure (the region surrounded by the inner wall surface of the magnetic shield part 30 divided by the xz plane passing through the formation surface 10a) becomes the reference line BL. And the direction at the reference line BL is orthogonal to the reference line BL. Therefore, the air gap magnetic field is applied perpendicular to the magnetoelectric conversion element 20.

  In the first to third embodiments, the example in which all the height positions of the gap 33 and the height position of the sensor substrate 10 are the same is shown. However, a configuration in which the height position of a part of the gap 33 and the height position of the sensor substrate 10 are the same may be employed.

  In the first to third embodiments, the example in which the height position of the center of the gap 33 and the height position of the formation surface 10a are the same is shown. However, the height position of the center of the gap 33 may be different from the height position of the formation surface 10a.

  In 1st-3rd embodiment, the sensor board | substrate 10 showed the example located in the center of the site | part which comprises the symmetrical structure in the magnetic shield part 30. FIG. However, the sensor substrate 10 may not be located at the center.

  In the first to fourth embodiments, the example in which the two gaps 33 are disposed to face each other with the sensor substrate 10 interposed therebetween is shown. However, the two gaps 33 do not have to be opposed to each other with the sensor substrate 10 interposed therebetween.

  In the first to fourth embodiments, an example in which a magnetoresistive effect element is formed on the sensor substrate 10 as the magnetoelectric conversion element 20 has been described. However, the magnetoelectric conversion element 20 is not limited to the above example. For example, a Hall element whose voltage value varies depending on the applied magnetic field can be employed. In particular, in the case of the first to third embodiments, a Hall element whose voltage value varies only by an applied magnetic field along the formation surface 10a may be employed as the magnetoelectric conversion element 20.

  In the first to fourth embodiments, an example in which the intermediate layer has insulating properties and the magnetoelectric conversion element 20 is a tunnel magnetoresistive element has been described. However, the intermediate layer has conductivity, and the magnetoelectric transducer 20 may be a giant magnetoresistive element (GMR). AMR may also be used.

  In the first to fourth embodiments, an example in which a full bridge circuit is configured by the magnetoelectric conversion element 20 has been described. However, a configuration in which a half-bridge circuit is configured by the magnetoelectric conversion element 20 may be employed.

  In the first to fourth embodiments, an example in which the bias magnet 40 is a permanent magnet has been described. However, the bias magnet 40 may be a solenoid.

  In 1st-4th embodiment, the circuit board 50 and the sensor board | substrate 10 are electrically connected via the wire 11, and the example mounted in the support substrate 60 along with the circuit board 50 and the sensor board | substrate 10 is shown. It was. However, a stack structure in which the sensor substrate 10 is stacked on the circuit board 50 and is electrically and mechanically connected may be employed.

  In the first to fourth embodiments, the example in which the two air gaps 33 are formed in the magnetic shield part 30 is shown. However, a configuration in which one or three or more gaps 33 are formed in the magnetic shield part 30 can also be adopted.

DESCRIPTION OF SYMBOLS 10 ... Sensor substrate 20 ... Magnetoelectric conversion element 30 ... Magnetic shield part 31 ... 1st site | part 32 ... 2nd site | part 33 ... Gap 34 ... Projection part 35 ... Convex Portion 36 ... Upper shield 37 ... Lower shield 40 ... Bias magnet 50 ... Circuit board 60 ... Support substrate 70 ... Mold resin 80 ... Spacer 90 ... Conductor 100 to be measured ... Current sensors

Claims (1)

A sensor substrate (10);
A magnetoelectric transducer (20) formed on one surface (10a) of the sensor substrate (10), the output signal of which varies with an applied magnetic field;
A magnetic shield portion (30) that magnetically shields the outside and the inside by surrounding the sensor substrate (10) and the conductor to be measured (90) through which the current to be measured flows;
A current sensor for measuring the current to be measured based on a change in an output signal of the magnetoelectric transducer (20) due to a magnetic field generated by the current to be measured;
In the magnetic shield part (30), at least one air gap (33) for suppressing magnetic saturation in the magnetic shield part (30) is formed,
The magnetic shield part (30) has at least one of a gap magnetic field generated in the gap (33) and an external magnetic field generated outside the magnetic shield part (30). The current sensor is characterized in that a suppression means for suppressing the application to the above is formed.

Images