Electric 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

Current Sensor

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

[0002] In a current sensor that uses a magnetic sensor to measure the amount of current flowing through a bus bar, a magnetic shield is sometimes provided to reduce the influence of an external magnetic field on the magnetic sensor. For example, Patent Documents 1 to 3 disclose a magnetic shield having a U-shaped cross section (U-shaped magnetic shield).

[0003] JP 2010-223868 A International Publication No. 2018-159229 JP 2021-107800 A

[0004] To ensure the measurement accuracy of the current sensor, it is important that the magnetic shield be appropriately positioned relative to the bus bar and the magnetic sensor, regardless of its shape. Here, the magnetic sensor is typically mounted on a circuit board, and the portion of the bus bar facing the magnetic sensor is generally flat. Therefore, the U-shaped magnetic shield has a three-dimensional shape compared to the other components that make up 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 of the U-shaped magnetic shield, and a protrusion provided on a resin housing is inserted into this through hole. The protrusion protruding from the through hole is thermally melted and then naturally cooled, thereby fixing 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 the sensor board and the main board, and the magnetic shield is fitted into a recess provided in this support member. In Patent Document 3, the U-shaped magnetic shield is fixed to the board by a resin part covering the bottom wall of the U-shaped magnetic shield and a shield fixing part having legs extending from the resin part along the side wall and claws provided at the tips of the legs to hook onto the board.

[0006] In the structure disclosed in Patent Document 1, a through hole is provided in part of the magnetic shield for attenuating the external magnetic field, which raises concerns that this may affect the external magnetic field attenuation function.In the structures disclosed in Patent Documents 2 and 3, the possibility of misalignment occurring between the resin that holds the magnetic shield and the magnetic shield cannot be eliminated.

[0007] The present invention aims to provide a current sensor having a U-shaped magnetic shield, in which the U-shaped magnetic shield can be fixed to the case with high positional accuracy without affecting the external magnetic field attenuation function of the U-shaped magnetic shield.

[0008] In order to solve the above problem, one aspect of the present invention provides a current sensor comprising: a bus bar extending in a first direction, a magnetic shield having a portion facing the bus bar along the third direction, when three mutually perpendicular directions are defined as a first direction, a second direction, and a third direction, respectively; a magnetic sensor facing the bus bar along the third direction on the side of the bus bar opposite to the side on which the magnetic shield is located; and a case integrally molded with a portion of the bus bar, wherein the magnetic shield has: a U-shaped portion having a bottom wall portion including a portion facing the bus bar along the third direction; and two side wall portions standing upright from an end of the bottom wall portion in the second direction along the third direction and arranged opposite each other in the second direction; an attachment portion connected to the U-shaped portion and fixed to the case; and a connecting portion connecting the U-shaped portion and the attachment portion.

[0009] By using an attachment section connected to the U-shaped section, which primarily performs the external magnetic field attenuation function in the magnetic shield, to fix the relative position of the U-shaped section to the case, i.e., when attaching the section, the U-shaped section can be shaped specifically for the external magnetic field attenuation function, while the attachment section can be specialized for the function of fixing the section to the case.This allows for increased positioning accuracy of the magnetic shield, and is expected to improve the measurement accuracy of the magnetic sensor.

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

[0011] In the current sensor, a plurality of the bus bars may be arranged in the case in the second direction. In this case, it is preferable that the magnetic shield has a plurality of the U-shaped portions corresponding to the plurality of the bus bars, and the plurality of the U-shaped portions are connected to the common mounting portion.

[0012] Since multiple U-shaped sections are connected to one mounting section, the multiple U-shaped sections can be accurately positioned simultaneously by positioning the mounting section. Furthermore, since the multiple U-shaped sections are integrated via the mounting section, relative positional deviation of the multiple U-shaped sections is unlikely to occur. Furthermore, the multiple U-shaped sections can be attached in a single attachment process.

[0013] In the current sensor including the magnetic shield having the plurality of U-shaped portions, the two U-shaped portions corresponding to two adjacent bus bars may be arranged offset in the first direction. Furthermore, the two U-shaped portions corresponding to two adjacent bus bars may partially overlap when viewed along the first direction. By arranging them in this manner, it is possible to narrow the distance in the second direction between the two adjacent bus bars.

[0014] In the current sensor, the mounting portion may be made of a soft magnetic material and may be disposed between the U-shaped portion and a magnetic noise source, or may be provided on both ends of the U-shaped portion in the first direction. By making the mounting portion out of a soft magnetic material, the mounting portion can perform the function of attenuating an external magnetic field.

[0015] The current sensor may further include a cover that abuts against the case from the third direction. The provision of the cover reliably prevents foreign matter from entering the case. Furthermore, even if rust occurs on the components that make up the magnetic shield (particularly on the fractured surfaces after cutting the metal plate), the rust is less likely to leak to the outside of the current sensor, preventing problems caused by rust (such as short circuits).

[0016] In the current sensor, the magnetic shield may be made of a metal plate, and the side wall of the U-shaped portion may be formed by bending a portion of the metal plate. Such a magnetic shield is highly productive and has excellent quality stability, so that the quality of the current sensor can be expected to be stable.

[0017] In the current sensor, the U-shaped portion may be a laminated body made of a plurality of metal plates, 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 made of the metal plate that is the most distant from the bus bar among the metal plates that make up the laminated body.

[0018] The current sensor may include a plurality of magnetic shields, and the plurality of magnetic shields may be fixed to the case such that the plurality of bus bars corresponding to the plurality of U-shaped portions of the plurality of magnetic shields are aligned along the second direction. For example, if the magnetic shield has three U-shaped portions, the magnetic shield can be positioned as a measurement unit, such as to correspond to measurement of three-phase wiring, which may increase design freedom.

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

[0020] 1A is an explanatory diagram of a current sensor according to a first embodiment of the present invention; FIG. 1B is a diagram showing a cross section taken along line AA' in FIG. 1A; FIG. 1C is an explanatory diagram of a magnetic shield included in the current sensor according to the first embodiment of the present invention (as viewed along the Y1-Y2 direction (first direction)); FIG. 1D is an explanatory diagram of a magnetic shield included in the current sensor according to the first embodiment of the present invention (as viewed along the Z1-Z2 direction (third direction)); FIG. 1E is a diagram showing a simulation result for confirming the shielding effect of the magnetic shield included in the current sensor according to the first embodiment of the present invention, as viewed along the Y1-Y2 direction (first direction); FIG. 1F is a diagram showing a simulation result for confirming the shielding effect of the magnetic shield included in the current sensor according to the first embodiment of the present invention, as viewed along the Z1-Z2 direction (third direction); FIG. 1G is a diagram showing a simulation result for confirming the shielding effect of the magnetic shield included in a current sensor according to a conventional technology, as viewed along the Y1-Y2 direction (first direction); FIG. 1H is a diagram showing a simulation result for confirming the shielding effect of the magnetic shield included in a current sensor according to a conventional technology, as viewed along the Z1-Z2 direction (third direction). FIG. 1 is an explanatory view of a magnetic shield included in a current sensor according to a second embodiment of the present invention (viewed along the Z1-Z2 direction (third direction)). FIG. 2 is an explanatory view of a magnetic shield included in a current sensor according to a third embodiment of the present invention (viewed along the Z1-Z2 direction (third direction)). FIG. 3 is an explanatory view of a magnetic shield included in a current sensor according to a fourth embodiment of the present invention (viewed along the Z1-Z2 direction (third direction)). FIG. 4 is an explanatory view of a magnetic shield included in a current sensor according to a fourth embodiment of the present invention (viewed along the Y1-Y2 direction (first direction)). FIG. 5 is an explanatory view of a current sensor according to a fourth embodiment of the present invention (viewed along the Z1-Z2 direction (third direction)). FIG. 6 is an explanatory view of a method for manufacturing a portion of the magnetic shield included in a current sensor according to the fourth embodiment of the present invention (before bending). FIG. 7 is an explanatory view of a method for manufacturing a portion of the magnetic shield included in a current sensor according to the fourth embodiment of the present invention (viewed along the Z1-Z2 direction (third direction) after bending). FIG. 8 is an explanatory view of a method for manufacturing a portion of the magnetic shield included in a current sensor according to the fourth embodiment of the present invention (viewed along the Y1-Y2 direction (first direction)).FIG. 10 is an explanatory diagram of a current sensor according to a conventional technique corresponding to the current sensor according to the fourth embodiment of the present invention (viewed along the Z1-Z2 direction (third direction)). FIG. 11 is an explanatory diagram of a magnetic shield provided in the current sensor according to the fifth embodiment of the present invention (viewed along the Z1-Z2 direction (third direction)). FIG. 12 is an explanatory diagram of a magnetic shield provided in the current sensor according to the fifth embodiment of the present invention (viewed along the Y1-Y2 direction (first direction)). FIG. 13 is an explanatory diagram of a current sensor according to a sixth embodiment of the present invention (viewed along the Z1-Z2 direction (third direction)). FIG. 14 is an explanatory diagram of a current sensor according to a seventh embodiment of the present invention (cross-sectional view taken along the Y1-Y2 direction (first direction)). FIG. 15 is an explanatory diagram of a current sensor according to a modification of the seventh embodiment of the present invention (cross-sectional view taken along the Y1-Y2 direction (first direction)).

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following description, the same components will be assigned the same reference numerals, and the description of components that have already been described will be omitted as appropriate. In the following description, the Y1-Y2 direction will be defined as the first direction, the X1-X2 direction as the second direction, and the Z1-Z2 direction as the third direction. In some cases, the Z1 side of the Z1-Z2 direction (third direction) will be referred to as "upper," and the Z2 side of the Z1-Z2 direction (third direction) will be referred to as "lower."

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

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

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

[0025] The U-shaped portion 31 has a bottom wall portion 31B including a portion facing the busbar 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 an end of the bottom wall portion 31B in the second direction (X1-X2 direction) and are arranged opposite each other in the second direction (X1-X2 direction). Therefore, the U-shaped portion 31 has a U-shape when viewed along the first direction (Y1-Y2 direction).

[0026] The U-shaped portion 31 attenuates the external magnetic field directed toward the magnetic sensor 20 from the side opposite to the side facing the magnetic sensor 20, thereby improving the measurement accuracy of the magnetic sensor 20 that detects the induced magnetic field generated from the busbar 10. The U-shaped portion 31 has a U-shaped cross section, and the side wall portion 31W extends to the Z1 side in the Z1-Z2 direction. Therefore, the U-shaped portion 31 can attenuate not only the external magnetic field from the Z2 side of the bottom wall portion 31B in the Z1-Z2 direction, but also the external magnetic field from the sides of the side wall portion 31W (the X1 side in the X1-X2 direction and the X2 side in the X1-X2 direction).

[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 walls 31W, 31W. When viewed along the first direction (Y1-Y2 direction), the bus bar 10 is located between the two side walls 31W, 31W, and therefore the U-shaped portion 31 not only has the function of attenuating an external magnetic field but also serves as a yoke that preferentially passes the induced magnetic field from the bus bar 10.

[0028] In this embodiment, when viewed along the first direction (Y1-Y2 direction), the magnetic sensor 20 is not located between the two sidewalls 31W, 31W, but is located slightly above the upper ends (the ends on the Z1 side in the Z1-Z2 direction) of the two sidewalls 31W, 31W (see FIG. 1B ). This arrangement allows the induced magnetic field from the busbar 10 to pass through the interior of the U-shaped portion 31, exit from the upper end of one sidewall 31W, and pass through a magnetic circuit that enters the interior of the U-shaped portion 31 from the upper end of the other sidewall 31W. In this magnetic circuit, the magnetic path that exits from the upper end of one sidewall 31W and heads toward the upper end of the other sidewall 31W has a larger component that passes 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 busbar 10 is efficiently applied to the magnetic sensor 20.

[0029] The magnetic sensor 20 may be located between the two side walls 31W, 31W when viewed along the first direction (Y1-Y2 direction). When the magnetic sensor 20 is located in this manner, it is expected that the external magnetic field attenuation function of the U-shaped portion 31 will be particularly enhanced.

[0030] In this embodiment, the U-shaped portion 31 is made of a bent body of three soft magnetic metal plates 301, 302, and 303, and is a multilayer body in which two metal plates 302 and 303 are stacked in the Z1-Z2 direction on top of the metal plate 301 (on the Z1 side in the Z1-Z2 direction). Note that the metal plate 302 is disposed in close contact with the inner surface of the metal plate 301, and the metal plate 303 is disposed in close contact with the inner surface of the metal plate 302. The metal plates 301, 302, and 303 are held together by caulking or the like.

[0031] Of the three metal plates 301, 302, and 303 constituting the laminate, the metal plate 301 located furthest from the busbar 10 (on the 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 portion of the metal plate 301 is bent to form part of the U-shaped portion 31, and the unbent portion constitutes the connecting portion 33 and the mounting portion 32. The presence of the connecting portion 33 reduces the possibility that, when the metal plate 301 is bent to raise the portion constituting the side wall portion 31W, the portion constituting the side wall portion 31W will not rise properly due to interference with other surrounding portions or that unexpected deformation will occur in the surrounding portions.

[0032] In this embodiment, the mounting portion 32 and the connecting portion 33 are provided only on the metal plate 301. However, they may also be provided on the three metal plates 301, 302, and 303. In this case, it is desirable that the mounting portions 32 and the connecting portions 33 provided on the metal plates 301, 302, and 303 are provided in overlapping positions and have the same shape when viewed from the Z1-Z2 direction. Alternatively, 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 accommodating recess 41 provided in the case 40. Therefore, by providing the mounting portion 32 and the connecting portion 33 only on the metal plate 301 as in this embodiment, the amount by which the U-shaped portion 31 protrudes from the accommodating recess 41 toward the Z2 side in the Z1-Z2 direction can be minimized, thereby reducing the external size of the current sensor 100 in the Z1-Z2 direction.

[0033] 2B shows the shape of the portion of side wall 31W made of metal plate 301 before it is bent. As the shape of portion 301W indicates, in metal plate 301 before it is bent to form U-shaped portion 31, the end of the portion that will become U-shaped portion 31 in the X1-X2 direction and the end of mounting portion 32 in the X1-X2 direction are in the same position in the X1-X2 direction. Therefore, little material is wasted when processing metal plate 301.

[0034] The mounting portion 32 is connected to the U-shaped portion 31 via a connecting portion 33, and is fixed to the case 40 at the mounting portion 32. In this embodiment, the mounting portion 32 has a plurality of through holes 32h (two in this embodiment), and a fixing member 60 is inserted through these through holes 32h and fixed to the case 40, thereby fixing the mounting portion 32 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 portion of the busbar 10 is embedded in the case 40, for example, by insert molding. The lower side (Z2 side in the Z1-Z2 direction) of the case 40 is provided with an accommodation recess 41 that is recessed to match the shape of the U-shaped portion 31 and accommodates the U-shaped portion 31. Furthermore, the lower side (Z2 side in the Z1-Z2 direction) of the case 40 is provided with a fixing hole 43 that receives a fixing member 60 inserted through the through hole 32h of the mounting portion 32 to maintain the U-shaped portion 31 positioned within the accommodation recess 41. Fixing the mounting portion 32 to the case 40 using the fixing member 60 fixes a flat member (the mounting portion 32) to a flat surface (the underside of the case 40), making it easy to increase positioning accuracy. However, it is not easy to accurately position the U-shaped portion 31, which has a three-dimensional shape, within the accommodation recess 41. Therefore, by positioning and fixing the mounting portion 32 relative to the case 40, the U-shaped portion 31 connected to the mounting portion 32 via the connecting portion 33 can be accurately positioned relative to the case 40.

[0036] On the upper side (Z1 side in the Z1-Z2 direction) of the case 40, there is provided a cavity 42 that houses the magnetic sensor 20 fixed to the substrate 50, and a fixing hole 44 for fixing the substrate 50. Since the magnetic sensor 20 is positioned and fixed to the substrate 50, by fixing a fixing member 60 that has passed through a 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 42 is covered by the substrate 50 to form a closed space.

[0037] 3A is a view taken along the Y1-Y2 direction (first direction) showing the results of a simulation performed to confirm 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 taken along the Z1-Z2 direction (third direction) showing the results of a simulation performed to confirm 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 from a single metal plate, a side wall portion 31W that is longer than that of the magnetic shield 30 shown in FIGS. 1A and 1B, and the magnetic sensor 20 is located between the two side wall portions 31W, 31W when viewed along the first direction (Y1-Y2 direction).

[0038] 4A is a view taken along the Y1-Y2 direction (first direction) showing the results of a simulation performed to confirm the shielding effect of a magnetic shield provided in a current sensor according to the prior art. FIG. 4B is a view taken along the Z1-Z2 direction (third direction) showing the results of a simulation performed to confirm the shielding effect of a magnetic shield provided in a current sensor according to the prior art. The magnetic shield 30X shown in FIGS. 4A and 4B does not have the connecting portion 33 and the mounting portion 32 of the magnetic shield 30a shown in FIGS. 2A and 2B, and has a structure in which the entire shield is made up of a U-shaped portion 31.

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

[0040] 3A and 3B, in the magnetic shield 30a, the external magnetic field flowing from the X1 side in the X1-X2 direction to the X2 side in the X1-X2 direction is attenuated by the two side walls 31W, 31W that stand upright on the Z1 side in the Z1-Z2 direction. Furthermore, because the mounting portion 32, which has high magnetic permeability, is located adjacent to the U-shaped portion 31, the magnetic field flowing between the two side walls 31W, 31W of the U-shaped portion 31 tends to flow preferentially through the mounting portion 32 rather than through the air. In other words, part of the magnetic field flowing between the two side walls 31W, 31W is attracted to the mounting portion 32.

[0041] For this reason, in the magnetic shield 30a, only a small amount of the external magnetic field flows around the side wall portion 31W into the region where the magnetic sensor 20 is located, but a relatively large amount of the external magnetic field flows in the magnetic shield 30X. Reflecting this, when comparing the region on the Y2 side of the magnetic sensor 20 in the Y1-Y2 direction between the two side wall portions 31W, the simulation result for the magnetic shield 30a shown in Fig. 3B shows that the external magnetic field penetrates shallower than the simulation result for the magnetic shield 30X shown in Fig. 4B (see dashed arrows).

[0042] Because magnetic shield 30a allows less external magnetic field to penetrate, the magnetic flux density passing through magnetic sensor 20 is lower for magnetic shield 30a. Specifically, in this simulation, in which the magnetic flux density of the applied external magnetic field is 500 μT, the magnetic flux density passing through magnetic sensor 20 is approximately 100 μT for magnetic shield 30X ( FIGS. 4A and 4B ), while it is approximately 30 μT for magnetic shield 30a ( FIGS. 3A and 3B ). Note that, because FIGS. 3A to 4B are originally color figures converted to monochrome, the shading of the arrows does not correspond to the strength of the magnetic flux density.

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

[0044] 5 is an explanatory diagram (viewed along the Z1-Z2 direction (third direction)) of a magnetic shield provided in a current sensor according to a second embodiment of the present invention. 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. Therefore, only the magnetic shield 30A will be described, and descriptions of the other components will be omitted.

[0045] The magnetic shield 30A of the current sensor according to the second embodiment of the present invention differs from the magnetic shield 30 of the current sensor 100 according to the first embodiment in that a metal plate 301A is used instead of the metal plate 301, resulting in a different shape for the mounting portion 32A. Specifically, the mounting portion 32A of the magnetic shield 30A extends further toward the Y1 side in the Y1-Y2 direction on both sides of the mounting portion 32 of the magnetic shield 30 in the second direction (X1-X2 direction), and has four through holes 32h, two more than in the first embodiment. Because the mounting portion 32A has more through holes 32h, the mounting portion 32A of the magnetic shield 30A is more stably fixed to the case 40. 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] Similarly to the metal plate 301 of the magnetic shield 30 (see FIG. 2B), the metal plate 301A before being bent to form the U-shaped portion 31 has a rectangular shape in which the end in the X1-X2 direction of the portion that will become the U-shaped portion 31 is located close to a portion of the mounting portion 32A that extends further toward the Y1 side in the Y1-Y2 direction. Furthermore, the connecting portion 33 is formed from the metal plate 301A with a length equal to the width of the cutting margin for forming the outer shape of the U-shaped portion 31. In other words, little material is wasted when processing the metal plate 301A.

[0047] 6 is an explanatory diagram (viewed along the Z1-Z2 direction (third direction)) of a magnetic shield provided in a current sensor according to a third embodiment of the present invention. 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. Therefore, only the magnetic shield 30B will be described, and descriptions of the other components will be omitted.

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

[0049] 3A to 4B, the mounting portion 32 has an external magnetic field attenuation function. Therefore, by being positioned on both sides of the first direction (Y1-Y2 direction) in which the busbar 10 extends, the portion where the magnetic sensor 20 is provided becomes less susceptible to the influence of the external magnetic field.

[0050] Fourth Embodiment FIG. 7A is an explanatory diagram of a magnetic shield included in a current sensor according to a fourth embodiment of the present invention (as viewed along the Z1-Z2 direction (third direction)). FIG. 7B is an explanatory diagram of a magnetic shield included in a current sensor according to a fourth embodiment of the present invention (as viewed along the Y1-Y2 direction (first direction)). FIG. 7C is an explanatory diagram of a current sensor according to a fourth embodiment of the present invention (as viewed along the Z1-Z2 direction (third direction)). A 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. Therefore, only the magnetic shield 30C will be described, and descriptions of the other components will be omitted or simplified. FIG. 7C shows only the arrangement of the busbar 10, the magnetic sensor 20, and the magnetic shield 30C.

[0051] In the current sensor according to the fourth embodiment of the present invention, a plurality of (specifically, three) bus bars 10 are arranged 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 the three bus bars 10, respectively, and these three U-shaped portions 31C1, 31C2, and 31C3 are connected to a common mounting portion 32C via respective connecting portions 33C.

[0052] Because the multiple U-shaped portions 31C1, 31C2, and 31C3 are connected to one mounting portion 32C, positioning the mounting portion 32C allows the multiple U-shaped portions 31C1, 31C2, and 31C3 to be accurately positioned simultaneously. Furthermore, because the multiple U-shaped portions 31C1, 31C2, and 31C3 are integrated via the mounting portion 32C, relative positional deviations among the multiple U-shaped portions 31C1, 31C2, and 31C3 are unlikely to occur. Furthermore, because the multiple U-shaped portions 31C1, 31C2, and 31C3 can be attached in a single attachment process, this is advantageous from the standpoint of productivity.

[0053] 7A, of the three U-shaped portions 31C1, 31C2, and 31C3 aligned in the second direction (X1-X2 direction), the central U-shaped portion 31C2 is positioned closer to the Y2 side in the Y1-Y2 direction than the two U-shaped portions 31C1 and 31C3 at both ends. In other words, the three U-shaped portions 31C1, 31C2, and 31C3 are arranged in a so-called staggered pattern. 7B , when viewed along the first direction (the Y2 side in the Y1-Y2 direction), the side wall 31W on the X1 side of the U-shaped portion 31C1 in the X1-X2 direction overlaps with the side wall 31W on the X2 side of the X1-X2 direction of the U-shaped portion 31C3 located on the X1 side of the U-shaped portion 31C1 in the X1-X2 direction, and the side wall 31W on the X2 side of the X1-X2 direction of the U-shaped portion 31C1 overlaps with the side wall 31W on the X1 side of the X1-X2 direction of the U-shaped portion 31C2 located on the X2 side of the U-shaped portion 31C1 in the X1-X2 direction. By arranging the three U-shaped portions 31C1, 31C2, and 31C3 in this manner, the spacing between adjacent busbars 10 can be narrowed, as shown in FIG. 7C , and the current sensor 110 can be made smaller in size in the Y1-Y2 direction.

[0054] 7B , the magnetic shield 30C includes three metal plates 301C, 302, and 303, and the metal plate 301C forms parts of the three U-shaped portions 31C1, 31C2, and 31C3, the three connecting portions 33C, and the mounting portion 32C. The two metal plates 302 and 303 are disposed on top of the metal plate 301C that forms part of the U-shaped portion 31C1, and the three U-shaped portions 31C1, 31C2, and 31C3 are formed as a layered body of these metal plates 301C, 302, and 303.

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

[0056] 8A , the metal plate 301C is flat as a whole before the U-shaped portions 31C1, 31C2, and 31C3 are shaped. As shown in FIG. 8A , the gaps between the U-shaped portions 31C1 and 31C2, the gaps between the U-shaped portions 31C1 and 31C3, the gaps between the U-shaped portions 31C2 and the mounting portion 32C, and the gaps between the U-shaped portions 31C3 and the mounting portion 32C are formed by punching. As a result, three connecting portions 33C are formed between the U-shaped portions 31C1, 31C2, and 31C3 and the mounting portion 32C. Providing these gaps, in other words, providing the connecting portions 33C, reduces the possibility that the portions constituting the side wall portion 31W will not properly rise due to interference with other surrounding portions or that unexpected deformation will occur in the surrounding portions when the portions constituting the side wall portion 31W are raised in the next step, which is the bending process.

[0057] Similarly to the metal plate 301 of the magnetic shield 30 and the metal plate 301A of the magnetic shield 30A, in the state before being bent to form the U-shaped portion 31, the X2-side end of the X1-X2 direction of the portion that will become the X2-side sidewall 31W of the U-shaped portion 31C2 in the X1-X2 direction and the X2-side end of the mounting portion 32C in the X1-X2 direction are located at the same position in the X1-X2 direction. Similarly, the X1-side end of the X1-X2 direction of the portion that will become the X1-side sidewall 31W of the U-shaped portion 31C3 in the X1-X2 direction and the X1-side end of the mounting portion 32C in the X1-X2 direction are located at the same position in the X1-X2 direction. Furthermore, instead of providing individual mounting portions 32C corresponding to the U-shaped portions 31C1 to 31C3, the U-shaped portions 31C1 to 31C3 are connected to a common mounting portion 32C by connecting portions 33C. Therefore, there is little waste of material when processing the metal plate 301C.

[0058] 8B and 8C, the portion that constitutes side wall portion 31W rises in the third direction. After the portion that constitutes side wall portion 31W and the portion that constitutes bottom wall portion 31B are formed in this manner, metal plates 302 and 303 that have been similarly bent are sequentially stacked to form U-shaped portion 31 made of a multilayer body, thereby completing the manufacture of magnetic shield 30C.

[0059] FIG. 9 is an explanatory diagram (viewed along the Z1-Z2 direction (third direction)) of a current sensor according to the prior art, corresponding to the current sensor according to the fourth embodiment of the present invention. In the current sensor 110X shown in FIG. 9, three magnetic shields 30X, each consisting of a U-shaped portion 31 and having no mounting portion 32 or connecting portion 33, are arranged in a staggered pattern, 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. The influence of an external magnetic field on the current sensor 110X was measured and found to be 1.8% of the external magnetic field strength. In contrast, the influence of a similar external magnetic field on the current sensor 110 according to the fourth embodiment of the present invention was measured and found to be 0.8% of the external magnetic field strength. In other words, the influence of the external magnetic field strength was reduced to less than half.

[0060] Considering this quantitatively further, when the rated current is 1000 A, current sensor 110X will have a measurement error of up to 18 A. In contrast, current sensor 110 will have a measurement error of 8 A, a difference of 10 A. Even if the rated current is 1000 A, the normal current range is approximately 100 A to 200 A. Therefore, assuming an abnormal state in which the full rated current flows through a busbar 10 adjacent to another busbar 10 used within this normal current range, the error due to the external magnetic field will be approximately 10% to 20% for current sensor 110X, while the error will be approximately 5% to 10% for current sensor 110. When the current sensor is applied to an electric vehicle, these differences in error, 5% to 10%, are significant enough to be ignored when calculating the driving range (electricity efficiency) per unit of power.

[0061] Fifth Embodiment FIG. 10A is an explanatory diagram (viewed along the Z1-Z2 direction (third direction)) of a magnetic shield provided in a current sensor according to a fifth embodiment of the present invention. FIG. 10B is an explanatory diagram (viewed along the Y1-Y2 direction (first direction)) of a magnetic shield provided in a current sensor according to a fifth embodiment of the present invention. 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, so only the magnetic shield 30D will be described, and descriptions of the other components will be omitted.

[0062] 10A and 10B has two U-shaped portions 31D1 and 31D2. Each of these two U-shaped portions 31D1 and 31D2 has a connecting portion 33D provided at both ends of the bottom wall portion 31B in the first direction (Y1-Y2 direction). As a result, each of the two U-shaped portions 31D1 and 31D2 has a structure in which an attachment portion 32D extends on both sides in the first direction (Y1-Y2 direction).

[0063] Furthermore, similar to the magnetic shield 30C of the fourth embodiment, the metal plate 301D constituting a portion of the U-shaped portions 31D1 and 31D2 and the connecting portion 33D and the mounting portion 32D can be punched and bent from a flat plate to form the side wall portion 31W. A portion of the side wall portion 31W on the X1 side of the U-shaped portion 31D1 in the X1-X2 direction is formed by bending the metal plate located at the position of the gap HP on the X1 side of the U-shaped portion 31D1 in the X1-X2 direction. A portion of the side wall portion 31W on the X2 side of the U-shaped portion 31D2 in the X1-X2 direction is formed by bending the metal plate located at the position of the gap HP on the X2 side of the U-shaped portion 31D2 in the X1-X2 direction.

[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, the two U-shaped portions 31D1 and 31D2 and the two mounting portions 32D are arranged at positions that are point-symmetric with respect to the intersection P between an imaginary line L1 that bisects the magnetic shield 30D in the X1-X2 direction and an imaginary line L2 that bisects the magnetic shield 30D in the Y1-Y2 direction in FIG. 10A . Such excellent symmetry can be advantageous from the standpoint of productivity (manufacturing efficiency, shape processability, and assembly ease of the metal plate 301D). More specifically, it has the advantage of making it less likely that the magnetic shield 30D will be mounted in the wrong direction when attached to a case (not shown).

[0065] Sixth Embodiment FIG. 11 is an explanatory diagram of a current sensor according to a sixth embodiment of the present invention (viewed along the Z1-Z2 direction (third direction)). A current sensor 200 according to this embodiment includes a plurality of bus bars 10 and a plurality of magnetic shields. Specifically, as shown in FIG. 11, a magnetic shield 30B according to the third embodiment and 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] Furthermore, in current sensor 200, by associating busbars 10 having a common purpose with the same magnetic shield, measurement units can be configured for each magnetic shield. As a specific example, when current sensor 200 is used in an electric vehicle, unit U1 including magnetic shield 30B with one U-shaped portion 31 can be used to detect the current of a boost converter, and units U2 and U3 including magnetic shield 30C with three U-shaped portions 31 can be used to measure the current of different three-phase motors. With this configuration, even if the rated current amounts of the three-phase motors measured by unit U2 and the three-phase motors measured by unit U3 differ, the rated current amounts can be measured using magnetic shield 30C as a unit, thereby simplifying the design of current sensor 200.

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

[0069] The current sensor 120 according to the fourth embodiment shown in FIG. 12A differs 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 the same. Therefore, the fixing member 60 is fixed to the case 40 by being inserted through the through-hole 32h of the mounting portion 32 or the through-hole 50h provided in the substrate 50. In contrast, the current sensor 130 according to the seventh embodiment shown in FIG. 12B differs from the current sensor 120 according to the fourth embodiment in that a cover member 71 is provided on the lower side (the Z2 side in the Z1-Z2 direction) of the mounting portion 32 and a cover member 72 is also provided on the upper side (the Z1 side in the Z1-Z2 direction) of the substrate 50. The mounting portion 32 is entirely housed in a recess provided in the cover member 71, so that the magnetic shield 30C is not exposed to the outside.

[0070] 12B, through holes (through hole 71h, through hole 40h) are provided in cover member 71 and case 40, and fixing member 60 is inserted from the bottom (Z2 side in the Z1-Z2 direction) through through hole 71h of cover member 71, through hole 32h of mounting portion 32, and through hole 50h of substrate 50. The tip of fixing member 60 is embedded in cover member 72, thereby fixing the positions of the components constituting current sensor 130.

[0071] By providing the cover members 71 and 72 in this manner, even if rust occurs on a part of the magnetic shield 30C (particularly on a fractured surface), the rust will not spill out to the outside of the current sensor 130. This prevents rust that has spilled to the outside from falling between the wiring and causing a short circuit.

[0072] The above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within 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 also be provided at the side wall portion 31W. As a specific example of such a case, the connecting portion 33 may be provided at the upper end (the end on the Z1 side in the Z1-Z2 direction) of the side wall portion 31W, and the attachment portion 32 may extend outward in the second direction (X1-X2 direction).

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

Claims

1. When the three mutually orthogonal directions are defined as a first direction, a second direction, and a third direction, 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 that faces the bus bar on a side opposite to a side of the bus bar on which the magnetic shield is disposed along the third direction; a case integrally formed with a portion of the bus bar; A current sensor comprising: The magnetic shield includes: a U-shaped portion including a bottom wall portion including a portion facing the bus bar along the third direction and two side wall portions standing upright 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; a mounting portion connected to the U-shaped portion and fixed to the case; A connecting portion that connects the U-shaped portion and the mounting portion; having the case has an accommodating recess that accommodates the U-shaped portion but does not accommodate the magnetic sensor, The magnetic shield is configured such that, in a state where the U-shaped portion is inserted into the receiving recess, The mounting portion is fixed to the outer surface of the case. A current sensor comprising:

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

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

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

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

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

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

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

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

10. 2. The current sensor according to claim 1, wherein the U-shaped portion is formed of a laminated body 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.

11. The current sensor according to claim 10 , wherein the mounting portion is formed from a metal plate that is the furthest from the bus bar among the metal plates that form the layered body.

12. A plurality of the magnetic shields are provided, 3. The current sensor according to claim 1, wherein the magnetic shields are fixed to the case such that the bus bars corresponding to the U-shaped portions of the magnetic shields are aligned along the second direction.