Current sensor

Abstract

This electric current sensor 10 allows a U-shaped magnetic shield to be fixed to a case with high positional accuracy without affecting an external magnetic field attenuation function of the U-shaped magnetic shield. The electric current sensor comprises: a bus bar 10 that extends in a first direction; a magnetic shield 30 that has a portion facing the bus bar 10 along a third direction; a magnetic sensor 20 that faces the bus bar along the third direction, on the side of the bus bar opposite the side where the magnetic shield is disposed; and a case 40 in which a part of the busbar 10 is integrally formed. The magnetic shield 30 has: a U-shaped part 31 having a bottom wall section 31B that includes a portion facing the bus bar 10 along the third direction, and two side wall sections 31W, 31W that rise along the third direction from the end sections of the bottom wall section 31B in a second direction and are disposed opposite to each other in the second direction; an attachment section 32 that is connected to the U-shaped part 31 and is fixed to the case; and a connecting section 33 that connects that U-shaped part 31 and the attachment section 32.

Description

Technical Field

[0001] The present invention relates to a current sensor having a U-shaped magnetic shield.

Background Art

[0002] In a current sensor that measures the amount of current flowing through a bus bar using a magnetic sensor, a magnetic shield may be provided for the purpose of reducing the influence of an external magnetic field on the magnetic sensor. For example, Patent Documents 1 to 3 disclose a magnetic shield (U-shaped magnetic shield) having a U-shaped cross-sectional shape.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Disclosure of the Invention

Problems to be Solved by the Invention

[0004] From the viewpoint of ensuring the measurement accuracy of the current sensor, it is important that the relative positions of the magnetic shield with respect to the bus bar and the magnetic sensor are appropriately set regardless of its shape. Here, since the magnetic sensor is provided on a substrate and the portion of the bus bar facing the magnetic sensor is generally flat, the U-shaped magnetic shield has a three-dimensional shape compared to other members constituting the current sensor. For this reason, various studies have been conducted to appropriately fix the U-shaped magnetic shield to the case.

[0005] For example, in Patent Document 1, a through hole is provided in the bottom wall portion of a U-shaped magnetic shield, a convex portion provided on a resin housing is inserted into this through hole, and the convex portion protruding from the through hole is heat-melted and then naturally cooled to fix the U-shaped magnetic shield to the housing. In Patent Document 2, a support member made of an insulating material such as resin is provided between a sensor substrate and a main substrate, and a magnetic shield is fitted into a recess provided in this support member. In Patent Document 3, a U-shaped magnetic shield is fixed to a substrate by a resin portion covering the bottom wall portion of the U-shaped magnetic shield, a leg portion extending from the resin portion along the side wall portion, and a shield fixing portion having a claw portion hooked on the substrate provided at the tip of the leg portion.

[0006] In the structure disclosed in Patent Document 1, a partial through hole is provided in the magnetic shield for attenuating an external magnetic field, and there is a concern that it may affect the external magnetic field attenuation function. In the structures disclosed in Patent Document 2 and Patent Document 3, it is impossible to eliminate the possibility of a shift occurring between the resin holding the magnetic shield and the magnetic shield.

[0007] An object of the present invention is to provide a current sensor having a U-shaped magnetic shield, which can fix the U-shaped magnetic shield to a case with high positional accuracy without affecting the external magnetic field attenuation function of the U-shaped magnetic shield.

Means for Solving the Problems

[0008] A current sensor according to an aspect of the present invention for solving the above problems, when three mutually orthogonal directions are defined as a first direction, a second direction, and a third direction respectively, includes a bus bar extending in the first direction, a magnetic shield having a portion facing the bus bar along the third direction, a magnetic sensor facing the bus bar along the third direction on the side opposite to the side where the magnetic shield is disposed on the bus bar, and a case in which a part of the bus bar is integrally formed. The magnetic shield includes a bottom wall portion including a portion facing the bus bar along the third direction, and a U-shaped portion having two side wall portions standing along the third direction from an end portion of the bottom wall portion in the second direction and facing each other in the second direction. The magnetic shield further includes a mounting portion connected to the U-shaped portion and fixed to the case, and a connecting portion connecting the U-shaped portion and the mounting portion.

[0009] When fixing, that is, attaching, the relative position of the U-shaped portion, which mainly functions as an external magnetic field attenuation function in the magnetic shield, to the case, by using the mounting portion continuously provided from the U-shaped portion, the U-shaped portion can have a shape specialized for the external magnetic field attenuation function, while the mounting portion can be specialized for the fixing function to the case. Therefore, the arrangement accuracy of the magnetic shield can be improved, and an improvement in the measurement accuracy of the magnetic sensor is expected.

[0010] In the above current sensor, the mounting portion may be provided from the connecting portion located at an end portion of the bottom wall portion of the U-shaped portion in the first direction. In this case, since a part of a single metal plate can be bent to form a side wall portion of the U-shaped portion or a part thereof, and the bottom wall portion of the U-shaped portion or a part thereof, the connecting portion, and the mounting portion can be formed from the remaining flat portion, it is possible to efficiently form the magnetic shield.

[0011] In the above current sensor, a plurality of the bus bars may be provided side by side in the second direction in the case. In this case, the magnetic shield preferably has a plurality of U-shaped portions corresponding to each of the plurality of bus bars, and the plurality of U-shaped portions are continuously provided to a common mounting portion.

[0012] Since a plurality of U-shaped portions are continuously provided on one mounting portion, by positioning the mounting portion, the plurality of U-shaped portions can be accurately positioned simultaneously. Further, since the plurality of U-shaped portions are integrated via the mounting portion, relative displacement between the plurality of U-shaped portions is less likely to occur. Also, in one mounting process, the plurality of U-shaped portions can be mounted.

[0013] In the current sensor including the magnetic shield having the plurality of U-shaped portions described above, the two U-shaped portions corresponding to two adjacent busbars may be arranged so as to be displaced in the first direction. Further, the two U-shaped portions corresponding to two adjacent busbars may partially overlap when viewed along the first direction. By adopting such an arrangement, it is possible to narrow the interval in the second direction between two adjacent busbars.

[0014] In the current sensor described above, the mounting portion may be made of a soft magnetic material and may be arranged so as to be located between the U-shaped portion and the magnetic noise source, or may be continuously provided at both ends of the U-shaped portion in the first direction. Since the mounting portion is made of a soft magnetic material, the mounting portion can function as an external magnetic field attenuation.

[0015] In the current sensor described above, the case may further include a cover that abuts against the case from the third direction. By providing the cover, it is stably prevented that foreign matter enters the inside of the case. Also, even if rust occurs from a member constituting the magnetic shield (especially the broken cross section after cutting a metal plate), the rust is unlikely to come out to the outside of the current sensor, so problems caused by rust (such as a short circuit as a specific example) are prevented.

[0016] In the current sensor described above, the magnetic shield may be made of a metal plate, and the side wall portion of the U-shaped portion may be formed by bending a part of the metal plate. Such a magnetic shield is excellent in productivity and also in quality stability, so quality stability of the current sensor is expected.

[0017] In the above current sensor, the U-shaped portion is formed of a laminate in which a plurality of metal plates are stacked, and the mounting portion may be connected to at least one of the plurality of metal plates by the connecting portion. In this case, the mounting portion may be formed of the metal plate that is the farthest from the bus bar among the metal plates constituting the laminate.

[0018] The above current sensor may include a plurality of magnetic shields, and the plurality of magnetic shields may be fixed to the case such that a plurality of bus bars corresponding to the plurality of U-shaped portions of the plurality of magnetic shields are arranged along the second direction. For example, when a magnetic shield has three U-shaped portions, it is possible to position the magnetic shield as a measurement unit, such as corresponding to the measurement of three-phase wiring, and the design freedom may be increased.

Advantages of the Invention

[0019] According to the present invention, there is provided a current sensor having a U-shaped magnetic shield, which can fix the U-shaped magnetic shield to the case with high positional accuracy without affecting the external magnetic field attenuation function of the U-shaped magnetic shield.

Brief Description of the Drawings

[0020]

Figure 1A

Figure 1B

Figure 2A

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Figure 3A

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Figure 4A

Figure 4B

Figure 5

Figure 6

Figure 7A

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Figure 7C

Figure 8A

Figure 8B

Figure 8C

Figure 9

Figure 10A

Figure 10B

Figure 11

Figure 12A

Figure 12B

[0021] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same members and the like are denoted by the same reference numerals, and the description of the members and the like that have been described once will be omitted as appropriate. In the following description, the Y1 - Y2 direction is defined as the first direction, the X1 - X2 direction is defined as the second direction, and the Z1 - Z2 direction is defined as the third direction. In some cases, the Z1 side in the Z1 - Z2 direction (third direction) is referred to as "upper" and the Z2 side in the Z1 - Z2 direction (third direction) is referred to as "lower".

[0022] (First Embodiment) FIG. 1A is an explanatory view of a current sensor according to a first embodiment of the present invention. FIG. 1B is a view showing a cross section taken along line A-A' of FIG. 1A. The A-A' line has two portions where the direction changes. In FIG. 1B, for the sake of explanation, the lid portion, the fixing member, and the substrate are not shown, and the magnetic sensor is shown as a virtual line. FIG. 2A is an explanatory view of a magnetic shield included in the current sensor according to the first embodiment of the present invention (a view seen along the Y1 - Y2 direction (first direction)). FIG. 2B is an explanatory view of a magnetic shield included in the current sensor according to the first embodiment of the present invention (a view seen along the Z1 - Z2 direction (third direction)).

[0023] As shown in FIGS. 1A and 1B, the current sensor 100 according to the first embodiment of the present invention includes a bus bar 10, a magnetic sensor 20, a magnetic shield 30, a case 40, a substrate 50, and a fixing member 60. The bus bar 10 extends in the first direction (Y1 - Y2 direction), and a current to be measured flows in the first direction through the bus bar 10. More specifically, for example, when measuring the current flowing from an inverter to a motor in an electric vehicle or the like, one end of the bus bar 10 in the first direction is connected to the inverter, and the other end is connected to the motor. The magnetic sensor 20 has a sensitivity axis along the second direction (X1 - X2 direction) and faces the bus bar 10 along the third direction (Z1 - Z2 direction) that intersects (orthogonal in this embodiment) the first direction (Y1 - Y2 direction). Specifically, the magnetic sensor 20 is disposed to face the Z1 side of the bus bar 10 in the Z1 - Z2 direction.

[0024] As shown in FIGS. 2A and 2B, the magnetic shield 30 includes a U-shaped portion 31, a mounting portion 32, and a connecting portion 33 that connects the U-shaped portion 31 and the mounting portion 32, and is formed of a bent body of a metal plate made of a soft magnetic material in this embodiment.

[0025] The U-shaped portion 31 has a bottom wall portion 31B including a portion facing the bus bar 10 along the third direction (Z1 - Z2 direction), and two side wall portions 31W, 31W that stand upright along the third direction (Z1 - Z2 direction) from the end portions of the bottom wall portion 31B in the second direction (X1 - X2 direction) and are disposed to face each other in the second direction (X1 - X2 direction). Therefore, the U-shaped portion 31 has a U-shaped shape when viewed along the first direction (Y1 - Y2 direction).

[0026] The U-shaped portion 31 can attenuate an external magnetic field directed from the side opposite to the side facing the magnetic sensor 20 in itself toward the magnetic sensor 20, and can improve the measurement accuracy of the magnetic sensor 20 that detects the induced magnetic field generated from the bus bar 10. Since the U-shaped portion 31 has a U-shaped cross section and the side wall portions 31W extend in the Z1 side in the Z1-Z2 direction, not only the external magnetic field from the Z2 side in the Z1-Z2 direction of the bottom wall portion 31B but also the external magnetic fields from the sides (the X1 side in the X1-X2 direction and the X2 side in the X1-X2 direction) of the side wall portions 31W can be attenuated.

[0027] When viewed along the third direction (Z1-Z2 direction), the bus bar 10 and the magnetic sensor 20 are located between the two side wall portions 31W, 31W. When viewed along the first direction (Y1-Y2 direction), since the bus bar 10 is located between the two side wall portions 31W, 31W, the U-shaped portion 31 can function not only as an external magnetic field attenuation function but also as a yoke that preferentially passes the induced magnetic field from the bus bar 10.

[0028] In the present embodiment, when viewed along the first direction (Y1-Y2 direction), the magnetic sensor 20 is not located between the two side wall portions 31W, 31W, but is located slightly above the upper ends (the ends on the Z1 side in the Z1-Z2 direction) of the two side wall portions 31W, 31W (see FIG. 1B). By being arranged in this way, the induced magnetic field from the bus bar 10 passes through the inside of the U-shaped portion 31, is emitted from the upper end of one side wall portion 31W, and passes through a magnetic circuit that enters the inside of the U-shaped portion 31 from the upper end of the other side wall portion 31W. In this magnetic circuit, the magnetic path emitted from the upper end of one side wall portion 31W and directed toward the upper end of the other side wall portion 31W has a larger component passing in the second direction (X1-X2 direction) which is the sensitivity axis direction of the magnetic sensor 20. Therefore, the induced magnetic field from the bus bar 10 is efficiently applied to the magnetic sensor 20.

[0029] Note that the magnetic sensor 20 may be located between the two side wall portions 31W, 31W when viewed along the first direction (Y1-Y2 direction). When arranged in that way, it is expected that the external magnetic field attenuation function of the U-shaped portion 31 will be particularly high.

[0030] In this embodiment, the U-shaped portion 31 is formed by bending three metal plates 301, 302, and 303 having soft magnetism, and is a laminate in which two metal plates 302 and 303 are stacked in the Z1-Z2 direction on the upper side (Z1 side in the Z1-Z2 direction) of the metal plate 301. The metal plate 302 is disposed in a state of being in close contact with the inner surface of the metal plate 301, and the metal plate 303 is disposed in a state of being in close contact with the inner surface of the metal plate 302. The metal plates 301, 302, and 303 are integrally held by caulking or the like.

[0031] Among the three metal plates 301, 302, and 303 constituting the laminate, the metal plate 301 farthest from the bus bar 10 (Z2 side in the Z1-Z2 direction) has a connecting portion 33 at an end in the first direction (Y1-Y2 direction) of a portion constituting the bottom wall portion 31B of the U-shaped portion 31. The metal plate 301 has a portion extending further in the first direction (Y1-Y2 direction) from the connecting portion 33, and this portion constitutes the mounting portion 32. That is, a part of the metal plate 301 is bent to form a part of the U-shaped portion 31, and the unbent part constitutes the connecting portion 33 and the mounting portion 32. By having the connecting portion 33, when the portion that bends the metal plate 301 to form the side wall portion 31W is raised, the possibility that the portion that forms the side wall portion 31W interferes with other portions located around and does not rise appropriately, or that unexpected deformation occurs in other portions around can be reduced.

[0032] In this embodiment, the mounting portion 32 and the connecting portion 33 are provided only on the metal plate 301, but they may be provided on three metal plates 301, 302, and 303. In that case, it is desirable that the mounting portion 32 and the connecting portion 33 provided on the metal plates 301, 302, and 303 have the same shape and overlap each other when viewed in the Z1-Z2 direction. Further, the mounting portion 32 and the connecting portion 33 may be provided only on the metal plate 302 or the metal plate 303. As shown in FIG. 1A, the metal plate 301 is fixed to the case 40 with the U-shaped portion 31 inserted into the housing recess 41 provided in the case 40. Therefore, by adopting the configuration in which the mounting portion 32 and the connecting portion 33 are provided only on the metal plate 301 as in this embodiment, the amount by which the U-shaped portion 31 protrudes from the housing recess 41 toward the Z2 side in the Z1-Z2 direction can be minimized, and the outer size of the current sensor 100 in the Z1-Z2 direction can be reduced.

[0033] A portion 301W indicated by a virtual line in FIG. 2B is the shape of the side wall portion 31W before the portion constituted by the metal plate 301 is bent. As shown by the shape of this portion 301W, the metal plate 301 in the state before being bent to form the U-shaped portion 31 has the end portion in the X1-X2 direction of the portion that becomes the U-shaped portion 31 and the end portion in the X1-X2 direction of the mounting portion 32 at the same position in the X1-X2 direction. Therefore, there is little waste of material when processing the metal plate 301.

[0034] The mounting portion 32 is connected to the U-shaped portion 31 via the connecting portion 33 and is fixed to the case 40 at the mounting portion 32. In this embodiment, a plurality (two in this embodiment) of through holes 32h are provided in the mounting portion 32, and the mounting portion 32 is fixed to the case 40 by fixing a fixing member 60 inserted through the through holes 32h to the case 40. Specific examples of the fixing member 60 are screws and bolts.

[0035] The case 40 is made of, for example, a resin-based material. A part of the bus bar 10 is embedded in the case 40 by, for example, insert molding. On the lower side (Z2 side in the Z1-Z2 direction) of the case 40, a recess 41 that accommodates the U-shaped portion 31 is provided in accordance with the shape of the U-shaped portion 31. Further, on the lower side (Z2 side in the Z1-Z2 direction) of the case 40, a fixing hole 43 for receiving the fixing member 60 inserted through the through hole 32h of the mounting portion 32 is provided in order to hold the state in which the U-shaped portion 31 is disposed inside the accommodating recess 41. Fixing the mounting portion 32 to the case 40 using the fixing member 60 is to fix the flat member (mounting portion 32) to the plane (the lower surface of the case 40), and it is easy to improve the positioning accuracy. On the other hand, it is not easy to accurately position the U-shaped portion 31 having a three-dimensional shape inside the accommodating recess 41. Therefore, by positioning and fixing the mounting portion 32 with respect to the case 40, the U-shaped portion 31 connected via the connecting portion 33 to the mounting portion 32 can be accurately positioned with respect to the case 40.

[0036] On the upper side (Z1 side in the Z1-Z2 direction) of the case 40, a cavity portion 42 that accommodates the magnetic sensor 20 fixed to the substrate 50 and a fixing hole 44 for fixing the substrate 50 are provided. Since the magnetic sensor 20 is positioned and fixed with respect to the substrate 50, by fixing the fixing member 60 inserted through the through hole 50h of the substrate 50 to the fixing hole 44, the magnetic sensor 20 is accurately positioned with respect to the case 40, and the cavity portion 42 is covered with the substrate 50 to form a closed space.

[0037] FIG. 3A is a view seen along the Y1 - Y2 direction (first direction) showing simulation results for confirming the shielding effect of the magnetic shield included in the current sensor according to the first embodiment of the present invention. FIG. 3B is a view seen along the Z1 - Z2 direction (third direction) showing simulation results for confirming the shielding effect of the magnetic shield included in the current sensor according to the first embodiment of the present invention. The magnetic shield 30a shown in FIGS. 3A and 3B has a U - shaped portion 31 formed of a single metal plate, and the side wall portions 31W are longer than those of the magnetic shield 30 shown in FIGS. 1A and 1B. When viewed along the first direction (Y1 - Y2 direction), the magnetic sensor 20 is positioned between the two side wall portions 31W, 31W.

[0038] FIG. 4A is a view seen along the Y1 - Y2 direction (first direction) showing simulation results for confirming the shielding effect of the magnetic shield included in the current sensor according to the prior art. FIG. 4B is a view seen along the Z1 - Z2 direction (third direction) showing simulation results for confirming the shielding effect of the magnetic shield included in the current sensor according to the prior art. The magnetic shield 30X shown in FIGS. 4A and 4B has a structure in which, in the magnetic shield 30a shown in FIGS. 2A and 2B, the connecting portion 33 and the mounting portion 32 are not provided, and the whole is composed of the U - shaped portion 31.

[0039] The plurality of arrows shown in FIGS. 3A and 3B showing the simulation results indicate the directions at each position of the external magnetic field. Note that since the basic models of the simulations shown in FIGS. 3A and 3B and the simulations shown in FIGS. 4A and 4B are different, the arrangement density of the arrows showing the simulation results is different, but the direction and strength (magnetic flux density) of the magnetic flux can be compared.

[0040] As shown in FIGS. 3A and 3B, in the magnetic shield 30a, an external magnetic field directed from the X1 side to the X2 side in the X1-X2 direction is attenuated by two side wall portions 31W, 31W standing on the Z1 side in the Z1-Z2 direction. Further, since the mounting portion 32 having a high magnetic permeability exists adjacent to the U-shaped portion 31, the magnetic field flowing between the two side wall portions 31W, 31W of the U-shaped portion 31 tends to flow preferentially through the mounting portion 32 rather than in the air. That is, a part of the magnetic field flowing between the two side wall portions 31W, 31W is attracted to the mounting portion 32.

[0041] Therefore, in the magnetic shield 30a, although the external magnetic field flowing into the region where the magnetic sensor 20 is located bypasses the side wall portion 31W, relatively more external magnetic field flows into the magnetic shield 30X. Reflecting this, when comparing the regions on the Y2 side in the Y1-Y2 direction of the magnetic sensor 20 between the two side wall portions 31W, in the simulation result of the magnetic shield 30a shown in FIG. 3B, the penetration of the external magnetic field is shallower than the simulation result of the magnetic shield 30X shown in FIG. 4B (see the dashed arrow).

[0042] Since the magnetic shield 30a has less penetration of the external magnetic field in this way, the magnetic flux density passing through the magnetic sensor 20 is lower for the magnetic shield 30a. Specifically, in this simulation where the magnetic flux density of the applied external magnetic field is 500 μT, the magnetic flux density passing through the magnetic sensor 20 is about 100 μT in the case of the magnetic shield 30X (FIGS. 4A and 4B), whereas it is about 30 μT in the case of the magnetic shield 30a (FIGS. 3A and 3B). Note that since FIGS. 3A to 4B are originally black-and-white conversions of color figures, the shading of the arrows does not correspond to the strength of the magnetic flux density.

[0043] In order to effectively utilize the external magnetic field attenuation function of the mounting portion 32, it is preferable that the mounting portion 32 is arranged close to the noise source. That is, the mounting portion 32 is preferably arranged to be located between the U-shaped portion 31 and the magnetic noise source.

[0044] (Second Embodiment) FIG. 5 is an explanatory diagram of the magnetic shield included in the current sensor according to the second embodiment of the present invention (a view seen along the Z1-Z2 direction (third direction)). Since the current sensor according to the second embodiment of the present invention is basically the same as the current sensor 100 according to the first embodiment except for the magnetic shield 30A, only the magnetic shield 30A will be described, and the description of other configurations will be omitted.

[0045] The magnetic shield 30A of the current sensor according to the second embodiment of the present invention has a different shape of the mounting portion 32A because a metal plate 301A is used instead of the metal plate 301 in comparison with the magnetic shield 30 of the current sensor 100 according to the first embodiment. Specifically, the mounting portion 32A of the magnetic shield 30A extends further in the Y1 direction of the Y1-Y2 direction on both sides in the second direction (X1-X2 direction) of the mounting portion 32 of the magnetic shield 30, and four through holes 32h are provided, which is two more than in the case of the first embodiment. Since the mounting portion 32A has more through holes 32h in this way, in the magnetic shield 30A, the fixing of the mounting portion 32A to the case 40 is stabilized. This means that the current sensor according to the second embodiment can have higher measurement accuracy than the current sensor 100 according to the first embodiment.

[0046] Also, similar to the metal plate 301 of the magnetic shield 30 (see FIG. 2B), the metal plate 301A in the state before being bent to form the U-shaped portion 31 has an end portion in the X1-X2 direction of the portion that will become the U-shaped portion 31 arranged close to the portion that extends further in the Y1 direction of the Y1-Y2 direction of the mounting portion 32A and has a rectangular shape. Also, a connecting portion 33 is formed with the same length as the width dimension of the cutting margin for forming the outer shape of the U-shaped portion 31 from the metal plate 301A. That is, there is less waste of material when processing the metal plate 301A.

[0047] (Third Embodiment) FIG. 6 is an explanatory diagram of a magnetic shield included in the current sensor according to the third embodiment of the present invention (a view seen along the Z1-Z2 direction (third direction)). Since the current sensor according to the third embodiment of the present invention is basically the same as the current sensor 100 according to the first embodiment except for the magnetic shield 30B, only the magnetic shield 30B will be described, and the description of other configurations will be omitted.

[0048] The magnetic shield 30B of the current sensor according to the third embodiment of the present invention has a different shape other than the U-shaped portion 31 because a metal plate 301B is used instead of the metal plate 301 in comparison with the magnetic shield 30 of the current sensor 100 according to the first embodiment. Specifically, in the magnetic shield 30, a connecting portion 33 was provided at the end on the Y2 side in the Y1-Y2 direction of the bottom wall portion 31B, but in the magnetic shield 30B, connecting portions 33B are provided at both ends in the Y1-Y2 direction of the bottom wall portion 31B. Accordingly, the mounting portions 32B are provided on both sides of the bottom wall portion 31B in the first direction (Y1-Y2 direction).

[0049] As described with reference to FIGS. 3A to 4B, the mounting portion 32 has an external magnetic field attenuation function. Therefore, by being located on both sides in the first direction (Y1-Y2 direction) in which the bus bar 10 extends, the portion where the magnetic sensor 20 is provided is less affected by the external magnetic field.

[0050] (Fourth Embodiment) FIG. 7A is an explanatory diagram of a magnetic shield included in the current sensor according to the fourth embodiment of the present invention (a view seen along the Z1-Z2 direction (third direction)). FIG. 7B is an explanatory diagram of a magnetic shield included in the current sensor according to the fourth embodiment of the present invention (a view seen along the Y1-Y2 direction (first direction)). FIG. 7C is an explanatory diagram of the current sensor according to the fourth embodiment of the present invention (a view seen along the Z1-Z2 direction (third direction)). Since the current sensor 110 according to the fourth embodiment of the present invention is basically the same as the current sensor 100 according to the first embodiment except for the magnetic shield 30C, only the magnetic shield 30C will be described, and the description of other configurations will be omitted or simplified. In FIG. 7C, only the arrangement of the bus bar 10, the magnetic sensor 20, and the magnetic shield 30C is shown.

[0051] In the current sensor according to the fourth embodiment of the present invention, a plurality (specifically, three) of busbars 10 are provided side by side in the second direction (X1-X2 direction) in the case 40. The magnetic shield 30C has three U-shaped portions 31C1, 31C2, and 31C3 corresponding to each of the three busbars 10, and these three U-shaped portions 31C1, 31C2, and 31C3 are connected to a common mounting portion 32C via their respective connecting portions 33C.

[0052] Since a plurality of U-shaped portions 31C1, 31C2, and 31C3 are connected in series to one mounting portion 32C, by positioning the mounting portion 32C, the plurality of U-shaped portions 31C1, 31C2, and 31C3 can be accurately positioned simultaneously. Further, since the plurality of U-shaped portions 31C1, 31C2, and 31C3 are integrated via the mounting portion 32C, relative displacement between the plurality of U-shaped portions 31C1, 31C2, and 31C3 is less likely to occur. Furthermore, since the plurality of U-shaped portions 31C1, 31C2, and 31C3 can be mounted in a single mounting process, it is also advantageous from the viewpoint of productivity.

[0053] As shown in FIG. 7A, among the three U-shaped portions 31C1, 31C2, and 31C3 arranged in the second direction (X1-X2 direction), the central U-shaped portion 31C2 is located on the Y2 side in the Y1-Y2 direction with respect to the two U-shaped portions 31C1 and 31C3 at both ends. That is, the three U-shaped portions 31C1, 31C2, and 31C3 are arranged in a so-called staggered pattern. For this reason, as shown in FIG. 7B, when viewed along the first direction (Y2 side in the Y1-Y2 direction), the side wall portion 31W on the X1 side in the X1-X2 direction of the U-shaped portion 31C1 overlaps with the side wall portion 31W on the X2 side in the X1-X2 direction of the U-shaped portion 31C3 located on the X1 side in the X1-X2 direction of the U-shaped portion 31C1, and the side wall portion 31W on the X2 side in the X1-X2 direction of the U-shaped portion 31C1 overlaps with the side wall portion 31W on the X1 side in the X1-X2 direction of the U-shaped portion 31C2 located on the X2 side in the X1-X2 direction of the U-shaped portion 31C1. By arranging the three U-shaped portions 31C1, 31C2, and 31C3 in this way, as shown in FIG. 7C, the interval between adjacent busbars 10 can be narrowed, and miniaturization of the current sensor 110 in the Y1-Y2 direction is realized.

[0054] As shown in FIG. 7B, the magnetic shield 30C includes three metal plates 301C, 302, and 303. The metal plate 301C constitutes a part of three U-shaped portions 31C1, 31C2, 31C3, three connecting portions 33C, and a mounting portion 32C. The two metal plates 302 and 303 are arranged so as to overlap the metal plate 301C that forms a part of the U-shaped portion 31C1, and the three U-shaped portions 31C1, 31C2, and 31C3 are a laminate of these metal plates 301C, 302, and 303.

[0055] FIG. 8A is an explanatory view (before bending) of a manufacturing method of a part of a magnetic shield included in the current sensor according to the fourth embodiment of the present invention. FIG. 8B is an explanatory view (viewed along the Z1-Z2 direction (third direction) after bending) of a manufacturing method of a part of a magnetic shield included in the current sensor according to the fourth embodiment of the present invention. FIG. 8C is an explanatory view (viewed along the Y1-Y2 direction (first direction) after bending) of a manufacturing method of a part of a magnetic shield included in the current sensor according to the fourth embodiment of the present invention.

[0056] Before the shaping of the U-shaped portions 31C1, 31C2, and 31C3, the entire metal plate 301C is flat. As shown in FIG. 8A, the gaps between the U-shaped portion 31C1 and the U-shaped portion 31C2, the gaps between the U-shaped portion 31C1 and the U-shaped portion 31C3, further the gaps between the U-shaped portion 31C2 and the mounting portion 32C, and the gaps between the U-shaped portion 31C3 and the mounting portion 32C are formed by punching. Thereby, three connecting portions 33C located between the U-shaped portions 31C1, 31C2, 31C3 and the mounting portion 32 are formed. By providing such gaps, in other words, by providing the connecting portions 33C, when raising the portion constituting the side wall portion 31W in the subsequent bending process, the possibility that the portion constituting the side wall portion 31W does not rise appropriately due to interference with other portions located around or that unexpected deformation occurs in other portions around can be reduced.

[0057] Further, similar to the metal plate 301 of the magnetic shield 30 and the metal plate 301A of the magnetic shield 30A described above, the metal plate 301C in the state before being bent to form the U-shaped portion 31 has the end portion on the X2 side in the X1-X2 direction of the portion that becomes the side wall portion 31W on the X2 side of the U-shaped portion 31C2 and the end portion on the X2 side in the X1-X2 direction of the attachment portion 32C at the same position in the X1-X2 direction. Similarly, the end portion on the X1 side in the X1-X2 direction of the portion that becomes the side wall portion 31W on the X1 side of the U-shaped portion 31C3 and the end portion on the X1 side in the X1-X2 direction of the attachment portion 32C are at the same position in the X1-X2 direction. Also, instead of providing the attachment portions 32C corresponding to the U-shaped portions 31C1 to 31C3 individually, they are connected by the connecting portion 33C to the common attachment portion 32C. Therefore, there is less waste of material when processing the metal plate 301C.

[0058] When the bending process is performed, as shown in FIGS. 8B and 8C, the portions constituting the side wall portion 31W rise in the third direction. After the portions constituting the side wall portion 31W and the portions constituting the bottom wall portion 31B are thus formed, the metal plates 302 and 303 that have been bent in the same manner are sequentially laminated to form the U-shaped portion 31 made of a laminate, and the manufacturing of the magnetic shield 30C is completed.

[0059] FIG. 9 is an explanatory view of a current sensor according to the prior art corresponding to the current sensor according to the fourth embodiment of the present invention (a view seen along the Z1-Z2 direction (third direction)). In the current sensor 110X shown in FIG. 9, there are three magnetic shields 30X each consisting of a U-shaped portion 31 without the attachment portion 32 and the connecting portion 33, and they are arranged in a staggered manner similar to the three U-shaped portions 31C1, 31C2, and 31C3 of the magnetic shield 30C of the current sensor 110 according to the fourth embodiment of the present invention. As a result of measuring the influence of an external magnetic field on the current sensor 110X, it became 1.8% of the external magnetic field strength. On the other hand, in the case of the current sensor 110 according to the fourth embodiment of the present invention, when the influence of the same external magnetic field was measured, it became 0.8% of the external magnetic field strength. That is, the influence of the external magnetic field strength became 1 / 2 or less.

[0060] If this is further examined quantitatively, in the case of a rated current of 1000 A, a measurement error of up to 18 A will occur in the current sensor 110X. In contrast, the measurement error in the current sensor 110 is 8 A, and the difference is 10 A. Even if the rating is 1000 A, the normally used current range is about 100 A to 200 A. Therefore, assuming an abnormal state where the rated current flows through the bus bar 10 adjacent to the bus bar 10 in the normal current range, in the case of the current sensor 110X, the error due to the external magnetic field is about 10% to about 20%, while in the case of the current sensor 110, it is about 5% to about 10%. When the current sensor is applied to an electric vehicle, the difference in these errors, which is 5% to 10%, is significant enough that it cannot be ignored when calculating the cruising range (electricity cost) per unit of electric energy.

[0061] (Fifth Embodiment) FIG. 10A is an explanatory diagram of a magnetic shield provided in the current sensor according to the fifth embodiment of the present invention (a view seen along the Z1-Z2 direction (third direction)). FIG. 10B is an explanatory diagram of a magnetic shield provided in the current sensor according to the fifth embodiment of the present invention (a view seen along the Y1-Y2 direction (first direction)). Since the current sensor according to the fifth embodiment of the present invention is basically the same as the current sensor 100 according to the first embodiment except for the magnetic shield 30D, only the magnetic shield 30D will be described, and the description of other configurations will be omitted.

[0062] The magnetic shield 30D shown in FIGS. 10A and 10B has two U-shaped portions 31D1 and 31D2. In both of these two U-shaped portions 31D1 and 31D2, connecting portions 33D are provided at both ends in the first direction (Y1-Y2 direction) of the bottom wall portion 31B. As a result, for each of the two U-shaped portions 31D1 and 31D2, mounting portions 32D extend on both sides in the first direction (Y1-Y2 direction).

[0063] Moreover, the metal plate 301D that constitutes a part of the U-shaped portions 31D1 and 31D2, the connecting portion 33D, and the mounting portion 32D can form the side wall portion 31W by performing punching and bending operations on the flat plate, similar to the magnetic shield 30C of the fourth embodiment. By bending the metal plate located at the position of the gap portion HP on the X1 side in the X1-X2 direction of the U-shaped portion 31D1, a part of the side wall portion 31W on the X1 side in the X1-X2 direction of the U-shaped portion 31D1 is formed. By bending the metal plate located at the position of the gap portion HP on the X2 side in the X1-X2 direction of the U-shaped portion 31D2, a part of the side wall portion 31W on the X2 side in the X1-X2 direction of the U-shaped portion 31D2 is formed.

[0064] Furthermore, as shown in FIG. 10A, when viewed along the third direction (Z1-Z2 direction), the magnetic shield 30D has a point-symmetric shape. That is, with respect to the intersection point P of the virtual line L1 that bisects the magnetic shield 30D in the X1-X2 direction in FIG. 10A and the virtual line L2 that bisects the magnetic shield 30D in the Y1-Y2 direction, the two U-shaped portions 31D1 and 31D2, the two mounting portions 32D, etc. are arranged at positions that are point-symmetric. Such excellent symmetry can be advantageous from the perspective of productivity (manufacturing efficiency, shape workability, and assemblability of the metal plate 301D). More specifically, when attaching the magnetic shield 30D to a case (not shown), there are advantages such as making it difficult to misalign the attachment direction.

[0065] (Sixth Embodiment) FIG. 11 is an explanatory view of the current sensor according to the sixth embodiment of the present invention (a view seen along the Z1-Z2 direction (third direction)). The current sensor 200 according to this embodiment includes a plurality of busbars 10 and a plurality of magnetic shields. Specifically, as shown in FIG. 11, the magnetic shield 30B according to the third embodiment and the two magnetic shields 30C according to the fourth embodiment are arranged side by side in the second direction (X1-X2 direction).

[0066] In this way, by providing a plurality of magnetic shields corresponding to a plurality of bus bars 10 in one case 40, a current sensor 200 capable of measuring a large number of bus bars 10 can be easily formed.

[0067] Also, in the current sensor 200, by making bus bars 10 with common usage purposes correspond to the same magnetic shield, a measurement unit can be configured in units of magnetic shields. As a specific example, when the current sensor 200 is used in an electric vehicle, a unit U1 including a magnetic shield 30B having one U-shaped portion 31 is used for the purpose of detecting the current of a boost converter, and units U2 and U3 including a magnetic shield 30C having three U-shaped portions 31 are used for the purpose of measuring the currents of different three-phase motors, respectively. With this configuration, even if the rated current amounts are different between the three-phase motor measured by unit U2 and the three-phase motor measured by unit U3, since the magnetic shield 30C can be used as a unit to correspond to their respective rated current amounts, it is possible to facilitate the design of the current sensor 200.

[0068] FIG. 12A is an explanatory view of a current sensor according to a fourth embodiment of the present invention (a cross-sectional view seen in the Y1 - Y2 direction (first direction)). FIG. 12B is an explanatory view of a current sensor according to a seventh embodiment of the present invention (a cross-sectional view seen in the Y1 - Y2 direction (first direction)).

[0069] The current sensor 120 according to the fourth embodiment shown in FIG. 12A is different from the current sensor 100 according to the first embodiment shown in FIG. 1A in that the magnetic shield 30C has three U-shaped portions 31, but the basic configuration is common. Therefore, the fixing member 60 is fixed to the case 40 by passing through the through hole 32h of the mounting portion 32 or the through hole 50h provided in the substrate 50. On the other hand, the current sensor 130 according to the seventh embodiment shown in FIG. 12B is different from the current sensor 120 according to the fourth embodiment in that a cover member 71 is provided on the lower side (Z2 side in the Z1-Z2 direction) of the mounting portion 32, and a cover member 72 is also provided on the upper side (Z1 side in the Z1-Z2 direction) of the substrate 50. Since the entire mounting portion 32 is accommodated in the recess provided in the cover member 71, the magnetic shield 30C is not exposed to the outside.

[0070] In the current sensor 130 shown in FIG. 12B, through holes (through hole 71h, through hole 40h) are provided in the cover member 71 and the case 40, and the fixing member 60 passes through the through hole 71h of the cover member 71, the through hole 32h of the mounting portion 32, and the through hole 50h of the substrate 50 from the lower side (Z2 side in the Z1-Z2 direction). Then, by embedding the tip of the fixing member 60 in the cover member 72, the positions of the members constituting the current sensor 130 are fixed.

[0071] By providing the cover members 71 and 72 in this way, even when rust occurs from a part (especially the broken cross section) of the magnetic shield 30C, the rust does not spill out to the outside of the current sensor 130. Therefore, the problem that the spilled rust falls between the wirings and causes a short circuit is prevented.

[0072] The embodiments described above are described to facilitate the understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

[0073] For example, in the above embodiment, the connecting portion 33 is provided at the end of the bottom wall portion 31B, but it may be provided on the side wall portion 31W. As a specific example in such a case, the connecting portion 33 may be provided at the upper end of the side wall portion 31W (the end on the Z1 side in the Z1-Z2 direction), and the mounting portion 32 may extend outward in the second direction (X1-X2 direction).

Description of Signs

[0074] 100, 110, 110X, 120, 130, 200: Current sensors 10: Bus bar 20: Magnetic sensor 30, 30a, 30A, 30B, 30C, 30D, 30X: Magnetic shield 31, 31C1, 31C2, 31C3, 31D1, 31D2: U-shaped part 31B: Bottom wall part 31W: Side wall part 32, 32A, 32B, 32C, 32D: Mounting part 32h, 40h, 50h, 71h: Through hole 33, 33B, 33C, 33D: Connecting part 40: Case 41: Accommodation recess 42: Cavity part 43, 44: Fixing hole 50: Substrate 60: Fixing member 71, 72: Cover member 301, 301A, 301B, 301C, 301D, 302, 303: Metal plate 301W: Part of the metal plate 301 before bending HP: Gap part L1, L2: Virtual line P: Intersection point of the virtual line L1 and the virtual line L2 U1, U2, U3: Unit

Claims

1. When three mutually orthogonal directions are defined as a first direction, a second direction, and a third direction respectively, a bus bar extending in the first direction, a magnetic shield having a portion facing the bus bar along the third direction, a magnetic sensor facing the bus bar along the third direction on the side of the bus bar opposite to the side where the magnetic shield is disposed, a case in which a part of the bus bar is integrally formed, and a current sensor comprising: The magnetic shield has a bottom wall portion including a portion facing the bus bar along the third direction and two side wall portions standing along the third direction from an end portion of the bottom wall portion in the second direction and disposed opposite to each other in the second direction, forming a U-shaped portion; an attachment portion connected to the U-shaped portion and fixed to the case; a connecting portion connecting the U-shaped portion and the attachment portion; and has The case has a housing recess that houses the U-shaped portion and does not house the magnetic sensor, The magnetic shield is fixed to the outer surface of the case at the attachment portion in a state where the U-shaped portion is inserted into the housing recess. A current sensor characterized by the above.

2. The current sensor according to claim 1, wherein the attachment portion may be provided from the connecting portion located at an end portion of the bottom wall portion of the U-shaped portion in the first direction.

3. A plurality of the bus bars are provided side by side in the second direction in the case, The magnetic shield has a plurality of the U-shaped portions corresponding to each of the plurality of the bus bars, and the plurality of the U-shaped portions are connected to a common attachment portion. The current sensor according to claim 1.

4. The two U-shaped portions corresponding to two adjacent bus bars are arranged to be displaced in the first direction, the current sensor according to claim 3.

5. The two U-shaped portions corresponding to two adjacent bus bars partially overlap when viewed along the first direction, the current sensor according to claim 4.

6. The mounting portion is made of a soft magnetic material and is arranged to be located between the U-shaped portion and a magnetic noise source, the current sensor according to claim 1.

7. The mounting portion is made of a soft magnetic material and is continuously provided at both ends of the U-shaped portion in the first direction, the current sensor according to claim 1.

8. The current sensor according to claim 1 further includes a cover that abuts against the case from the third direction with respect to the case.

9. The magnetic shield is made of a metal plate, and the side wall portion of the U-shaped portion is formed by bending a part of the metal plate, the current sensor according to claim 1.

10. The U-shaped portion is composed of a laminate in which a plurality of metal plates are stacked, and the mounting portion is connected to at least one of the plurality of metal plates by the connecting portion, the current sensor according to claim 1.

11. The mounting portion is composed of the metal plate that is the farthest from the bus bar among the metal plates constituting the laminate, the current sensor according to claim 10.

12. A plurality of magnetic shields are provided, The plurality of magnetic shields are fixed to the case such that a plurality of bus bars corresponding to the plurality of U-shaped portions of the plurality of magnetic shields are arranged along the second direction, the current sensor according to claim 1 or claim 2.

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