Current sensor

Abstract

A current sensor 1 according to the present invention comprises a bus bar 11, a magnetic detecting unit 12 capable of detecting a magnetic field generated when a current being measured flows through the bus bar 11, and a magnetic shield 13 capable of suppressing disturbance magnetic field noise acting on the magnetic detecting unit 12, wherein: the bus bar 11 extends in an X-axis direction; the magnetic detecting unit 12 is disposed facing the bus bar on a Y1 side thereof in a Y-axis direction perpendicular to a plate surface of the bus bar 11; when seen in the X-axis direction, the magnetic shield 13 has a U-shape including a bottom portion 131 that is disposed facing the bus bar 11 on a Y2 side thereof in the Y-axis direction, and that extends in a Z-axis direction, and side wall portions 132 extending from both edges, in the Z-axis direction, of the bottom portion 131 toward the Y1 side in the Y-axis direction; the bus bar 11 is disposed between the pair of side wall portions 132; and a first dimension T1 of the bottom portion 131 is greater than a second dimension T2 of the side wall portions 132, and therefore a deterioration of a frequency characteristic of the magnetic shield due to an eddy current generated when the current being measured flows is reduced.

Description

Current Sensor

[0001] The present invention relates to a current sensor that detects a magnetic field generated by a current to be measured flowing through a bus bar and measures the current value of the current to be measured from the detected magnetic field.

[0002] In recent years, current sensors have been used to control and monitor various devices by attaching them to measure the current flowing through them. Well-known current sensors of this type use magnetoelectric conversion elements, such as magnetoresistance elements and Hall elements, to sense the magnetic field generated by the current flowing through the current path. To improve the measurement accuracy of these current sensors, magnetic shielding members are used to reduce the influence of external magnetic fields.

[0003] Patent Document 1 describes a current sensor that aims to achieve miniaturization while maintaining a high magnetic shielding effect, and that includes a current path and a magnetoelectric conversion element that detects a magnetic field generated when a current to be measured flows through the current path, and that has an inner magnetic shield member that surrounds at least a part of the current path and the magnetoelectric conversion element, and an outer magnetic shield member that surrounds at least a part of the inner magnetic shield member. Patent Document 2 describes a current detection device that aims to achieve miniaturization while accurately detecting current, and that includes a sensor unit that includes a current path, a magnetic shield member that surrounds the current path, and three magnetic detection elements that detect a current flowing through the current path, and a housing that is integrally formed with an accommodating chamber for accommodating the sensor unit.

[0004] JP 2014-98633 A JP 2016-6399 A

[0005] The current sensors (current detection devices) of Patent Documents 1 and 2 include a magnetic shield member surrounding the current path, and therefore eddy currents are generated in the magnetic shield member due to changes in the magnetic field when a current to be measured flows through the current path. These eddy currents cause degradation of the frequency characteristics of the current sensor. Therefore, an object of the present invention is to provide a current sensor in which degradation of frequency characteristics caused by eddy currents in the magnetic shield generated when a current to be measured flows is reduced.

[0006] The present invention provides a current sensor that solves the above-described problems, comprising: a bus bar through which a current to be measured flows; a magnetic detection unit capable of detecting a magnetic field generated when the current to be measured flows through the bus bar; and a magnetic shield capable of suppressing disturbance magnetic field noise applied to the magnetic detection unit, wherein, when a first direction is a direction in which the bus bar extends and a second direction and a third direction are two directions orthogonal to each other, the magnetic detection unit is disposed opposite one side of the bus bar in the second direction orthogonal to a plate surface of the bus bar, and the magnetic shield has a U-shape when viewed along the first direction, the U-shape having a bottom portion disposed opposite the other side of the bus bar in the second direction and extending in the third direction, and sidewall portions extending from both ends of the bottom portion in the third direction toward one side in the second direction, and the bus bar is disposed between the pair of sidewall portions, wherein, when viewed along the first direction, a first dimension of the bottom portion in the second direction is greater than a second dimension of the sidewall portions in the third direction.

[0007] By configuring the magnetic shield so that the first dimension of the bottom is larger than the second dimension of the side wall, the eddy current loss that occurs when the current to be measured flows through the bus bar is suppressed, thereby reducing deterioration of the frequency characteristics of the current sensor.

[0008] Preferably, the first dimension is greater than the second dimension and is equal to or less than 2.0 times the second dimension. With this configuration, it is possible to reduce the size of the magnetic shield while suppressing eddy current loss that occurs in the magnetic shield when the current to be measured flows through the bus bar.

[0009] The magnetic shield may be configured by stacking reference plates, which are flat plates formed into a U-shape, in the first direction so that the outer shapes overlap. With this configuration, by forming the reference plates into an outer shape corresponding to the shape of the magnetic shield and stacking them, it is possible to easily form a magnetic shield in which the first dimension of the bottom is greater than the second dimension of the sidewall.

[0010] An insulating layer may be provided between adjacent reference plates. By providing an insulating layer between adjacent reference plates, the electrical resistance of the path of eddy currents generated in the magnetic shield increases, thereby suppressing eddy current loss.

[0011] The magnetic shield may include a first magnetic shield plate bent into a U-shape and a second magnetic shield plate formed in a flat plate shape, and the first magnetic shield plate and the second magnetic shield plate may be stacked at the bottom. By forming the bottom by stacking the second magnetic shield plate formed in a flat plate shape on a portion of the first magnetic shield plate bent into a U-shape and having a uniform thickness, a magnetic shield in which a first dimension of the bottom is larger than a second dimension of the side wall portion can be easily formed.

[0012] According to the present invention, it is possible to reduce the degradation of the frequency characteristics of the current sensor caused by the eddy current generated in the magnetic shield due to the change in the magnetic field generated when the current to be measured flows, thereby providing a current sensor with high measurement accuracy.

[0013] 5 is a perspective view of a current sensor according to a first embodiment; FIG. 6 is a cross-sectional view of the current sensor taken along line AA in FIG. 1; FIG. 7 is a cross-sectional view of the magnetic shield in the current sensor of FIG. 2A; FIG. 8 is a perspective view of a modified magnetic shield and a reference plate in FIG. 2B; FIG. 9 is a cross-sectional view of another modified magnetic shield in FIG. 2B; FIG. 10 is a perspective view of a current sensor according to a second embodiment; FIG. 11 is a cross-sectional view of the current sensor taken along line AA in FIG. 12; FIG. 13 is a graph showing frequency and phase characteristics of an example and a comparative example; FIG. 14 is a graph showing frequency and gain characteristics of an example and a comparative example; FIG. 15 is a graph showing the ratio (T1 / T2) of dimensions of the magnetic shield and the phase and gain characteristics of the example and the comparative example; FIG. 16 is a perspective view schematically illustrating the generation of eddy current in a magnetic shield; FIG. 17 is a cross-sectional view of a conventional current sensor; FIG. 18 is a perspective view showing simulation results of eddy currents generated in the magnetic shield of a conventional current sensor.

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. The same components in each drawing are designated by the same numbers, and their description will be omitted. Reference coordinates are shown in each drawing as appropriate to indicate the positional relationship of each component. The reference coordinates are defined as the X-axis direction (first direction) as the extension direction of the bus bar, the Y-axis direction (second direction) as the normal direction to the bus bar's plate surface, and the Z-axis direction (third direction) as the direction perpendicular to the bus bar's extension direction on the bus bar's plate surface. The Y-axis direction and the Z-axis direction are perpendicular to the X-axis direction and are also perpendicular to each other.

[0015] [First embodiment] Fig. 1 is a perspective view of a current sensor 1 according to this embodiment. Fig. 2A is a cross-sectional view taken along line AA in Fig. 1, and Fig. 2B is a cross-sectional view showing only the magnetic shield 13 extracted from the current sensor 1 of Fig. 2A. The current sensor 1 includes a bus bar 11, a magnetic detection unit 12, and the magnetic shield 13.

[0016] The bus bar 11 is a conductive material formed into a plate shape, with two opposing plate surfaces provided to correspond to the top and bottom (both sides in the Y-axis direction) of the case 14. The bus bar 11 is made of copper, brass, aluminum, or the like, and carries the current to be measured. The bus bar 11 is held in the case 14, and a portion of the bus bar 11 is formed integrally with the case 14 by insert molding.

[0017] The ends of the busbar 11 in the X-axis direction, which are the connection portions with the outside, do not necessarily have to be symmetrical with respect to the X-axis. Also, the portion of the busbar 11 facing the magnetic detection unit 12 may be set to have a smaller dimension in the Z-axis direction than the other portions. The portions of the busbar 11 other than the portion facing the magnetic detection unit 12 do not have to be flat, and may be bent, for example.

[0018] The magnetic detection unit 12 can detect a magnetic field generated when a current to be measured flows through the bus bar 11. A magnetoresistive element, a Hall element, or the like can be used as the detection element. In this embodiment, a magnetoresistive element is used as the detection element. The magnetic detection unit 12 is spaced apart from the bus bar 11 in the Y-axis direction and is disposed facing the Y1-side plate surface of the bus bar 11 in the Y-axis direction. In this embodiment, the Y2-side surface of the magnetic detection unit 12 is a detection surface capable of detecting magnetic fields, and can detect magnetic components along a sensitivity axis parallel to the detection surface. The magnetic detection unit 12 is mounted on the Y2-side surface of the substrate 15, which is disposed on the Y1-side of the magnetic detection unit 12, so that the sensitivity axis direction is perpendicular to the direction of the current to be measured flowing through the bus bar (the sensitivity axis direction is the Z-axis direction). The substrate 15 can be made of, for example, epoxy glass, ceramic, or the like.

[0019] In FIG. 2A , the magnetic detection unit 12 is positioned so that the center of its width in the Z-axis direction overlaps with the center of its width in the Z-axis direction of the busbar 11 when viewed along the X-axis direction. However, the magnetic detection unit 12 only needs to be positioned so that it can measure the magnetic field generated when a current to be measured flows through the busbar 11. Therefore, the magnetic detection unit 12 may be positioned at a position shifted from the busbar 11 rather than being entirely overlapped with it. For example, even if the magnetic detection unit 12 is positioned at a position shifted toward the Z2 side from the position shown in FIG. 2A and does not overlap the busbar 11 when viewed along the Y-axis direction, it is sufficient that the magnetic field generated when a current to be measured flows through the busbar 11 can be measured. However, it is preferable that a portion of the magnetic detection unit 12 overlaps the opposing busbar 11 when viewed along the Y-axis direction.

[0020] 2A , the magnetic detection unit 12 is not positioned between the side wall portions 132 of the magnetic shield 13, but the magnetic detection unit 12 may be positioned between the side wall portions 132. That is, the magnetic detection unit 12 may be positioned so that it overlaps with the side wall portions 132 when viewed along the Z-axis direction. By positioning the magnetic detection unit 12 between the side wall portions 132, the magnetic shield 13 can effectively suppress disturbance magnetic fields with respect to the magnetic detection unit 12.

[0021] When viewed along the X-axis direction, the magnetic shield 13 has a U-shape including a bottom 131 and two sidewalls 132 extending from both ends of the bottom 131 toward the Y1 side. The bottom 131 is made of a flat plate having a surface parallel to the XZ plane, extends in the Z-axis direction, and is disposed opposite the Y2 side in the Y-axis direction with respect to the bus bar 11. The sidewalls 132 are made of a flat plate having a surface parallel to the XY plane, and extend from both ends of the bottom 131 in the Z-axis direction toward the Y1 side in the Y-axis direction.

[0022] The magnetic shield 13 may be, for example, a stack of multiple metal plates of the same shape. The magnetic shield 13 blocks disturbance magnetic field noise and reduces the disturbance magnetic field noise applied to the magnetic detection unit 12, thereby improving the disturbance magnetic field noise resistance of the magnetic detection unit 12.

[0023] The current sensor 1 is used, for example, in a battery management system (BMS) that monitors the remaining charge level of a battery to measure the current flowing in and out of the battery. In this case, high accuracy is important. Therefore, the current sensor 1 is provided with a U-shaped magnetic shield 13 that is highly effective in protecting the magnetic detection unit 12 from external magnetic disturbances.

[0024] The components are arranged in the order of bottom 131 of magnetic shield 13, bus bar 11, and magnetic detection unit 12, from the Y2 side to the Y1 side in the Y-axis direction. The bus bar 11 is provided between two side wall portions 132 of the magnetic shield 13 in the Z-axis direction. Therefore, an eddy current is generated in the magnetic shield 13 by an induced magnetic field generated by the current to be measured flowing through the bus bar 11.

[0025] FIG. 9 is a perspective view that schematically illustrates eddy currents generated in the magnetic shield 13 when a current to be measured flows through the bus bar 11 (see FIG. 2A ). The eddy currents generated in the magnetic shield 13 due to changes in the magnetic field will be described with reference to the same figure, which shows a portion of the bottom 131 of the magnetic shield 13. When the magnet N is moved closer to the magnetic shield 13, a magnetic field C is generated at point A on the magnetic shield 13 in a direction that reduces the magnetic field B that increases due to the movement of the magnet N. This generation of the magnetic field C generates a current Y at point A in the direction indicated by the arrow. The change in the magnetic field generates a current like the current Y indicated by the arrow at every point in the magnetic shield 13. Therefore, when the magnetic shield 13 is viewed as a whole, an eddy current is generated that flows counterclockwise, centered on the intersection O of the perpendicular line from the magnet N and the magnetic shield 13.

[0026] When a current to be measured flows through the bus bar 11, an induced magnetic field is generated, which causes a change in the magnetic field in the magnetic shield 13, generating an eddy current. This eddy current causes deterioration of the frequency characteristics of the current sensor 1. Therefore, from the viewpoint of providing a current sensor 1 with excellent measurement accuracy, it is preferable to reduce eddy current loss as much as possible.

[0027] 10 is a cross-sectional view of conventional current sensor 100, showing a cross section corresponding to the portion indicated by line AA of current sensor 1 in FIG. 1. U-shaped magnetic shield 103 is manufactured by bending a single plate, so that a first dimension T1 in the Y-axis direction of bottom portion 1031 is equal to a second dimension T2 in the Z-axis direction of side wall portion 1032. In conventional current sensor 100 including U-shaped magnetic shield 103 having the same thickness as first dimension T1 and second dimension T2, a simulation was performed of the magnetic flux density generated in magnetic shield 103 when a current to be measured is passed through bus bar 11.

[0028] 11 is a perspective view showing the simulation results. The simulation results shown in the figure reveal that in the U-shaped magnetic shield 103, when a current to be measured is passed through the bus bar 11, the magnetic flux density generated is higher at the bottom 1031 than at the side wall 1032.

[0029] The eddy current loss in the magnetic shield 103 is expressed by the following formula (1), and the square of the maximum magnetic flux density affects the eddy current loss. P e : Eddy current loss (W), K e : proportionality constant, f: frequency (Hz), B M : maximum magnetic flux density (T), t: thickness of magnetic shield (m), V: volume of magnetic shield (m 3 )

[0030] 2A and 2B , in order to reduce the influence of eddy current loss, the current sensor 1 has a first dimension T1 of the bottom portion 131, where the magnetic flux density is high, that is larger than a second dimension T2 of the side wall portion 132. Increasing the second dimension T2 of the side wall portion 132 increases the magnetic collecting effect on the magnetic field generated when a current to be measured flows through the bus bar 11, and therefore the magnetic shield 13 has an increased first dimension T1 only of the bottom portion 131, where the magnetic flux density is high. By using a U-shaped magnetic shield 13 in which the first dimension T1 of the bottom 131 in the Y-axis direction is larger than the second dimension T2 of the side wall portion 132 in the Z-axis direction, it is possible to reduce deterioration of the frequency characteristics of the current sensor 1.

[0031] From the viewpoint of suppressing the influence of eddy currents generated in the magnetic shield 13 due to the current to be measured flowing through the bus bar 11, the first dimension T1 is greater than the second dimension T2 and is preferably 2.0 times or less than the second dimension T2, more preferably 1.1 times or more and 1.6 times or less than the second dimension T2, and even more preferably 1.2 times or more and 1.4 times or less than the second dimension T2. ​​With the above configuration, it is possible to suppress deterioration of the frequency characteristics of the current sensor 1.

[0032] The U-shaped magnetic shield 13 may have a longitudinal dimension L1 in the Z-axis direction that is, for example, 1 to 4 times, and preferably 1.5 to 3 times, the transverse dimension L2 in the Y-axis direction.

[0033] 3 is a perspective view of a magnetic shield 16 as a modification of the magnetic shield 13 shown in FIG. 2B and a reference plate 163 that constitutes the magnetic shield 16. As shown in the figure, the reference plate 163 is a flat plate whose outer shape is formed in a U-shape when viewed along the X-axis direction. The magnetic shield 16 is configured by stacking the reference plates 163 in the X-axis direction so that the outer shapes of the reference plates 163 overlap.

[0034] A U-shaped magnetic shield with varying thickness cannot be formed simply by bending a plate of uniform thickness. For this reason, after bending the plate, it is necessary to perform processing such as thinning the sidewalls and thickening the bottom. Furthermore, there is a risk of springback, in which the bent portions of the plate return to their original shape. Therefore, it is difficult to form a U-shaped magnetic shield with varying thicknesses between the bottom and sidewalls from a plate of uniform thickness.

[0035] Therefore, the magnetic shield 16 shown in FIG. 3 is formed by stacking reference plates 163. The reference plates 163 constituting the magnetic shield 16 can be easily formed into a predetermined outer shape by, for example, punching a metal plate into a U-shape using a press. That is, it is easy to form the first dimension T1 of the bottom portion 161 and the second dimension T2 of the side wall portion 162 to be different dimensions. Furthermore, unlike when the reference plates 163 are formed by bending a single plate using sheet metal processing, press processing, or the like, springback does not occur and the shape is stable. Therefore, by stacking reference plates 163 with a predetermined outer shape, it is easy to form a magnetic shield 16 having a predetermined first dimension T1 of the bottom portion 161 and a predetermined second dimension T2 of the side wall portion 162.

[0036] Furthermore, an insulating layer 164 may be provided between the reference plates 163 that constitute the magnetic shield 16. The provision of the insulating layer 164 between the reference plates 163 can further suppress eddy currents. That is, the insulating layer 164 that insulates between adjacent reference plates 163 increases the electrical resistance of the path of the eddy current generated in the magnetic shield 16, thereby suppressing the eddy current that occurs when the current to be measured flows through the bus bar 11.

[0037] The insulating layer 164 only needs to be provided so as to insulate adjacent reference plates 163. For example, adjacent reference plates 163 can be insulated by stacking reference plates 163 in which the insulating layer 164 is formed only on the surface on the X1 side in the X-axis direction. Alternatively, reference plates 163 in which the insulating layer 164 is formed on both the X1 side and the X2 side in the X-axis direction and reference plates 163 in which the insulating layer 164 is not formed may be stacked alternately.

[0038] As described above, the magnetic shield 16 having a shape that can suppress the generation of eddy currents can be easily formed by stacking the reference plates 163. Furthermore, since the magnetic shield 16 does not undergo springback, the shape can be stably maintained.

[0039] 4 is a cross-sectional view of a magnetic shield 17, which is another modification of the magnetic shield 13 of FIG. 2B . As shown in the figure, the magnetic shield 17 includes a first magnetic shield plate 18 bent into a U-shape and a second magnetic shield plate 19 formed in a flat plate shape. The first magnetic shield plate 18 has a base 181 and opposing portions 182 extending from both ends of the base 181 in a direction intersecting the surface of the base 181. The two opposing portions 182 face each other in the Z-axis direction. The second magnetic shield plate 19 is stacked on the base 181 of the first magnetic shield plate 18. In this way, the magnetic shield 17 includes the first magnetic shield plate 18 and the second magnetic shield plate 19 stacked on the bottom 171 of the magnetic shield 17.

[0040] By using first magnetic shield plate 18, which is formed by bending a plate of uniform thickness into a U-shape, and second magnetic shield plate 19, which is formed in a flat plate shape, it is possible to easily form magnetic shield 17, which has different dimensions for bottom portion 171 and side wall portion 172. Furthermore, the ratio between first dimension T1 of bottom portion 171 and second dimension T2 of side wall portion 172 can be adjusted by changing the thickness of second magnetic shield plate 19, which is laminated on base portion 181 of first magnetic shield plate 18.

[0041] 4 shows a configuration in which the second magnetic shield plate 19 is provided on the inner surface (Y1 side in the Y-axis direction) of the base 181 of the first magnetic shield plate 18. However, the second magnetic shield plate 19 may also be provided on the outer surface (Y2 side in the Y-axis direction) of the base 181 of the first magnetic shield plate 18. The second magnetic shield plate 19 may be laminated on at least a portion of the base 181 of the first magnetic shield plate 18, but may also be laminated on the entire base 181. Both the first magnetic shield plate 18 and the second magnetic shield plate 19 may have a single-layer configuration or a laminated configuration.

[0042] Second Embodiment Fig. 5 is a perspective view of a current sensor 2 as a modified example of the current sensor 1. Fig. 6 is a cross-sectional view taken along line AA in Fig. 5. As shown in these figures, the current sensor 2 of this embodiment differs from the current sensor 1 in that it is a multi-phase type having a plurality of measurement phases 21 each having a bus bar 11, a magnetic detection unit 12, and a magnetic shield 13.

[0043] The U-shaped magnetic shield 13 allows the distance P between the bus bars 11 of the measurement phase 21 to be narrower than with a flat-type magnetic shield, and is therefore advantageous for miniaturizing the multiphase current sensor 2. However, the U-shaped magnetic shield 13 has a problem in that eddy currents generated when a current to be measured flows through the bus bars 11 tend to deteriorate the frequency characteristics of the current sensor 2.

[0044] Therefore, in the current sensor 2, the first dimension T1 of the bottom portion 131 of the U-shaped magnetic shield 13 is larger than the second dimension T2 of the side wall portion 132 (see FIG. 2B ). This suppresses eddy currents that occur in the magnetic shield 13 when a current to be measured flows through the bus bar 11, thereby reducing deterioration of the frequency characteristics of the current sensor 2. This reduces deterioration of the frequency characteristics and enables the multiphase current sensor 2 to be made smaller.

[0045] Example 1 In this example, a simulation was performed on the relationship between the frequency of the current to be measured flowing through the busbar 11 and the phase and gain characteristics for the current sensor 1 shown in FIG. 2A , which includes a magnetic shield 13 in which the first dimension T1 of the bottom 131 is larger than the second dimension T2 of the sidewall 132. The magnetic shield 13 had dimensions T1 = 2.6 mm, T2 = 2.0 mm, L1 = 13 mm, and L2 = 7 mm. As Comparative Example 1, a simulation was performed under the same conditions as in the example for the current sensor 100 shown in FIG. 10 , which includes a magnetic shield 103 in which the first dimension T1 of the bottom 1031 and the second dimension T2 of the sidewall 1032 are equal. The magnetic shield 103 had dimensions T1 = 2.0 mm, T2 = 2.0 mm, L1 = 13 mm, and L2 = 6.4 mm.

[0046] 7A and 7B are graphs showing simulation results of the phase and gain characteristics for the example and the comparative example. As shown in these figures, the current sensor 1 of the example exhibited less deterioration in the phase and gain characteristics as the frequency increased than the current sensor 100 of the comparative example. These results demonstrate that the use of a magnetic shield 13 in which the first dimension T1 of the bottom 131 is greater than the second dimension T2 of the sidewall 132 can suppress deterioration in the frequency characteristics of the current sensor due to the influence of eddy current loss.

[0047] Example 2: For the current sensor 1 of Example 1, a simulation of the phase characteristics and gain characteristics was performed, similar to Example 1, with the frequency of the current to be measured set to 1200 Hz and the ratio T1 / T2 of the T1 to T2 of the magnetic shield set to 1.0 (Comparative Example 1), 1.3, and 1.5. Figure 8 is a graph showing the simulation results of the phase characteristics and gain characteristics of this example. As shown in the figure, by setting T1 / T2 to be greater than 1.0, the phase characteristics and gain characteristics of the current sensor 1 were improved.

[0048] The phase and gain characteristics were significantly improved by setting T1 / T2 to 1.3 compared to when T1 / T2 was 1.0. However, even when T1 / T2 was set to 1.5, no further improvement in the phase and gain characteristics was observed compared to when T1 / T2 was 1.3. Based on these results, it can be said that from the perspective of improving frequency characteristics without increasing the size of the magnetic shield, it is preferable for T1 / T2 to be 1.2 or more and 1.4 or less.

[0049] INDUSTRIAL APPLICABILITY The present invention is useful as a current sensor equipped with a bus bar that is used to measure current flowing in and out of a battery in a BMS that monitors the remaining charge amount of a battery, etc.

[0050] DESCRIPTION OF SYMBOLS 1: Current sensor 2: Current sensor 11: Bus bar 12: Magnetic detection unit 13: Magnetic shield 14: Case 15: Substrate 16: Magnetic shield 17: Magnetic shield 18: First magnetic shield plate 19: Second magnetic shield plate 21: Measurement phase 100: Current sensor 103: Magnetic shield 131: Bottom 132: Side wall 161: Bottom 162: Side wall 163: Reference plate 164: Insulating layer 171: Bottom 172: Side wall 181: Base 182: Opposing portion 1031: Bottom 1032: Side wall T1: First dimension T2: Second dimension P: Distance O: Intersection A: Point B: Magnetic field C : Magnetic field L1: Longitudinal dimension L2: Shortitudinal dimension N: Magnet Y: Current

Claims

1. A bus bar through which a current to be measured flows; a magnetic detection unit capable of detecting a magnetic field generated when the current to be measured flows through the bus bar; a magnetic shield capable of suppressing disturbance magnetic field noise applied to the magnetic detection unit; When a direction in which the bus bars extend is defined as a first direction, and two directions that are perpendicular to the first direction and perpendicular to each other are defined as a second direction and a third direction, the magnetic detection unit is disposed to face one side in the second direction perpendicular to a plate surface of the bus bar, the magnetic shield has a U-shape when viewed along the first direction, the U-shape having a bottom portion disposed to face the other side of the bus bar in the second direction and extended in the third direction, and sidewall portions extending from both ends of the bottom portion in the third direction toward one side in the second direction, In the current sensor, the bus bar is disposed between the pair of side wall portions, When the magnetic shield is viewed along the first direction, a first dimension of the bottom portion in the second direction is larger than a second dimension of the sidewall portion in the third direction; the magnetic detection unit is located farther from the bottom in the second direction than the end portion on the one side in the second direction, and the bus bar is located closer to the bottom in the second direction than the end portion on the one side in the second direction, The current sensor, wherein a magnetic shield capable of suppressing the disturbance magnetic field noise is not disposed on the one side of the magnetic detection portion in the second direction.

2. 2. The current sensor of claim 1, wherein the first dimension is greater than the second dimension and is less than or equal to 2.0 times the second dimension.

3. The current sensor according to claim 1 , wherein the magnetic shield is configured by stacking reference plates, which are flat plates each having a U-shape, in the first direction so that the outer shapes overlap.

4. 4. The current sensor according to claim 3, further comprising an insulating layer between adjacent reference plates.

5. the magnetic shield includes a first magnetic shield plate bent into a U-shape, and a second magnetic shield plate made of the same material as the first magnetic shield plate and formed into a flat plate shape, The current sensor according to claim 1 , wherein the first magnetic shield plate and the second magnetic shield plate are laminated on the bottom portion.