Electric current sensor

Abstract

An electric current sensor 1 according to the present invention comprises a busbar 11 through which an electric current to be measured flows, a magnetic detection unit 12 capable of detecting a magnetic field generated when the electric current to be measured flows through the busbar 11, a case 13 that holds the busbar 11, a first magnetic shield 14A capable of reducing a disturbance magnetic field noise entering the magnetic detection unit 12, and a substrate 15 having the magnetic detection unit 12 disposed on a surface thereof on an X1 side in the X-axis direction, wherein the busbar 11, the magnetic detection unit 12, the substrate 15, and the first magnetic shield 14A are arranged in the noted order from the X1 side. The electric current sensor 1 further comprises a spacer unit 16 that is provided between the case 13 and the substrate 15 to space apart the busbar 11 and the magnetic detection unit 12 in the X-axis direction. The substrate 15 has a protruding portion 151 that protrudes from a position at which the substrate 15 is held by the spacer unit 16, in a protruding direction that is at least one of the Y-axis direction and the Z-axis direction, so that the electronic components such as the magnetic detection unit are prevented from reaching high temperatures due to heat generation from the busbar. Thus, the electric current sensor 1 is suitable for measuring high electric currents.

Description

Current Sensor

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

[0002] In recent years, with the growing demand for decarbonization, there has been a shift from engines to motors to reduce CO2 emissions during vehicle operation, i.e., a shift away from gasoline-powered vehicles and toward electrification (EV shift). Current sensors are used as current measurement devices to measure the current supplied to three-phase motors. As the shift to EVs spreads to large commercial vehicles such as trucks and buses, the motor capacity in hybrid and electric vehicles has increased, leading to larger measured currents in current sensors used for motor control. Furthermore, opportunities for continuous operation under high-load conditions have also increased, resulting in larger continuously flowing currents. Bus bars, which are the current paths for the measured current, generate heat in an amount proportional to the square of the current magnitude. Therefore, as the continuously flowing measured current increases, the amount of heat generated from the bus bars increases, resulting in the problem of electronic components, such as magnetic detectors, located near the bus bars becoming hot. Patent Document 1 describes a current sensor with heat dissipation irregularities on the insulating material of the case, which aims to prevent a decrease in the detection accuracy of the current sensor due to high temperatures. Patent Document 2 describes a current sensor that aims to be compact and has a magnetic detection unit provided inside a cover into which a shield is insert-molded.

[0003] International Publication No. WO2019 / 092912 International Publication No. WO2019 / 117169

[0004] The current sensor described in Patent Document 1 has a problem in that the heat dissipation unevenness provided on the cover increases the product size and manufacturing costs. The current sensor described in Patent Document 2, in which the magnetic detection unit is provided inside the cover, has a risk of causing the temperature inside the storage space to rise above the heat-resistant temperature of the magnetic detection unit due to heat generated by the bus bar, resulting in problems such as reduced measurement accuracy and a shortened product life. Therefore, the present invention aims to provide a current sensor suitable for measuring large currents, in which electronic components such as the magnetic detection unit are less likely to become hot due to heat generated by the bus bar. Another object of the present invention is to provide a current sensor that can be miniaturized without reducing measurement accuracy.

[0005] The present invention provides a current sensor that includes a bus bar through which a current to be measured flows, a magnetic detection unit capable of detecting a magnetic field generated when the current to be measured flows through the bus bar, a case that holds the bus bar, a first magnetic shield that suppresses disturbance magnetic field noise applied to the magnetic detection unit, and a substrate on one side of which the magnetic detection unit is disposed in the first direction, where three mutually orthogonal directions are defined as a first direction, a second direction, and a third direction, the current sensor including the bus bar, the magnetic detection unit, the substrate, and the first magnetic shield arranged in this order from one side of the first direction in the first direction, further including a spacer that is provided between the case and the substrate and separates the bus bar from the magnetic detection unit in the first direction, and a protrusion that protrudes from a position where the substrate is held by the spacer in at least one of the second direction and the third direction.

[0006] The board can dissipate heat generated by the bus bar due to the current being measured from the protrusion to the outside, thereby reducing the temperature rise of the magnetic detection unit disposed on the board due to heat generated by the bus bar.

[0007] The spacer portion may be provided integrally with the case. By forming the spacer portion integrally with the case, the strength of the spacer portion is increased, and the spacer portion can be manufactured efficiently because it can be formed simultaneously with the case.

[0008] The case may include a main body on one side of the spacer in the first direction, and the main body may include an extending portion extending from a location where the spacer is provided in a direction including the protruding direction. When viewed along the first direction, the extending portion may include an opposing portion that overlaps with the protruding portion and a protective portion located outward from an end of the protruding portion. The case may include a guard portion extending from the protective portion to the other side in the first direction, and the guard portion may be spaced apart from the protruding portion when viewed along the first direction. With the above configuration, the protruding portion can be protected by the extending portion and the guard portion, thereby reducing the risk of the protruding portion coming into contact with an external obstacle and damaging the circuit board when handling the current sensor.

[0009] The distance from the protective portion to the end of the guard portion in the first direction may be equal to or greater than the distance from the protective portion to the installation surface of the first magnetic shield of the circuit board and equal to or less than the distance from the protective portion to the top surface of the first magnetic shield. With the above configuration, the protrusion can be protected by the guard portion without increasing the dimension of the current sensor in the first direction.

[0010] When viewed along at least one of the second direction and the third direction, at least a portion of the guard portion may overlap with the protrusion. With the above configuration, the guard portion can cover the corner of the protrusion, thereby preventing the protrusion from coming into contact with the outside.

[0011] The guard portion may be a plurality of plate-like bodies, with gaps provided between adjacent plate-like bodies. With the above configuration, the gaps in the guard portion can adjust the air flow formed in the space surrounded by the guard portion, the protrusion, the spacer portion, and the opposing portion. Therefore, depending on the shape of the guard portion, it is possible to strike a balance between protecting the protrusion and cooling the substrate.

[0012] The first magnetic shield may be held on the substrate, and the side surfaces of the first magnetic shield may be covered with a coating. When the first magnetic shield is held on the substrate, the bottom surface (top surface) and side surfaces of the first magnetic shield opposite the substrate are exposed to the outside. Typically, an insulating coating is formed on the bottom surface, while the side surfaces are fractured surfaces. Therefore, by providing a coating that covers the side surfaces, rust generation from the fractured surfaces of the first magnetic shield can be suppressed.

[0013] The current sensor may have a plurality of measurement phases each including the bus bar and the magnetic detection unit, and the first magnetic shield may be provided independently for each measurement phase. This configuration makes the first magnetic shield less likely to become magnetically saturated than when a large first magnetic shield is used for multiple measurement phases. This increases the effectiveness of the first magnetic shield in suppressing disturbance magnetic field noise, improving the measurement accuracy of the current sensor.

[0014] The spacer portion may have a communication portion that opens in the second direction and / or the third direction. With the above configuration, it is possible to efficiently cool the space provided between the substrate and the bus bar located inside the spacer portion.

[0015] The spacer portion may surround the magnetic detection portion when viewed in the first direction. With the above configuration, the magnetic detection portion can be protected from the outside by the spacer portion.

[0016] The current sensor may further include a second magnetic shield, and the second magnetic shield, the bus bar, the magnetic detection unit, the substrate, and the first magnetic shield may be arranged in this order from one side of the first direction. With the above configuration, the effect of suppressing noise due to disturbance magnetic fields is improved, and the measurement accuracy of the current sensor is improved.

[0017] The distance in the first direction between the first magnetic shield and the bus bar may be greater than the distance in the first direction between the second magnetic shield and the bus bar, and the thickness of the first magnetic shield may be smaller than the thickness of the second magnetic shield. The thickness of each shield can be adjusted according to the distance from the bus bar to reduce the thickness of the magnetic shield in the first direction. This reduces the thickness of the magnetic shield, thereby enabling the current sensor to be miniaturized.

[0018] According to the present invention, heat generated by the bus bar can be dissipated to the outside through the protruding portion of the circuit board, thereby reducing the temperature rise of the circuit board and the magnetic detection unit. Therefore, a current sensor suitable for measuring large currents can be provided in which the temperature rise of electronic components such as the magnetic detection unit due to heat generated by the bus bar is suppressed.

[0019] 1. A perspective view of a current sensor according to a first embodiment. 2. A cross-sectional view of the current sensor taken along line AA in FIG. 1. 3. A plan view of the current sensor of FIG. 1. 4. A cross-sectional view of a modified example of the current sensor of FIG. 2. 5. A cross-sectional view of a current sensor according to a second embodiment. 6. A plan view of the current sensor of FIG. 4. 7. A plan view of a modified example of the current sensor of FIG. 4. 8. A cross-sectional view of another modified example of the current sensor of FIG. 4. 9. A cross-sectional view of a current sensor according to a third embodiment. 10. A cross-sectional view of a modified example of the current sensor of FIG. 8. 11. A cross-sectional view of another modified example of the current sensor of FIG. 12. 12. A cross-sectional view of a current sensor according to a fifth embodiment. 13. A cross-sectional view of a conventional current sensor. 14. A cross-sectional view of a conventional current sensor.

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. The same components in each drawing are designated by the same reference numerals, and their description will be omitted. Reference coordinates are indicated in each drawing as appropriate to indicate the positional relationship of each component. The reference coordinates are defined as the X-axis direction (first direction) perpendicular to the bus bar plate surface, the Y-axis direction (second direction) perpendicular to the bus bar extension direction on the bus bar plate surface, and the Z-axis direction (third direction) in the bus bar extension direction.

[0021] 1, 2A, and 2B are a perspective view, a cross-sectional view, and a plan view of a current sensor 1 according to this embodiment, with Fig. 2A showing a cross section taken along line AA in Fig. 1. As shown in these figures, the current sensor 1 according to this embodiment includes a bus bar 11, a magnetic detection unit 12, a case 13, a first magnetic shield 14A, and a substrate 15. The components are arranged in this order from the X1 side (one side) to the X2 side (the other side) in the X-axis direction (first direction): bus bar 11, magnetic detection unit 12, substrate 15, and first magnetic shield 14A.

[0022] The bus bar 11 is a conductive material formed in a plate shape, through which the current to be measured flows. The bus bar 11 is provided so that two opposing plate surfaces correspond to the top and bottom of the case 13 (both sides in the X-axis direction), and is made of, for example, copper, brass, aluminum, or the like.

[0023] The ends of the busbar 11 in the Z-axis direction, which are the connection portions with the outside, do not necessarily have to be symmetrical with respect to the Z-axis. Also, the portion of the busbar 11 facing the magnetic detection unit 12 may be set to have a smaller dimension in the Y-axis direction than the other portions. The portions of the busbar 11 other than the portion facing the magnetic detection unit 12 do not have to be flat, and may be bent, for example.

[0024] The magnetic detection unit 12 can detect a magnetic field generated when a current to be measured flows through the busbar 11. The magnetic detection unit 12 is positioned away from the busbar 11 and facing the busbar 11, with its sensitivity axis perpendicular to the direction of the current to be measured flowing through the busbar. In FIGS. 2A and 2B , the magnetic detection unit 12 is positioned so that the center of its width in the Y-axis direction overlaps with the center of its width in the Y-axis direction of the busbar 11 when viewed along the X-axis. However, the magnetic detection unit 12 only needs to be positioned so that it can measure the magnetic field generated when a current to be measured flows through the busbar 11. Therefore, the magnetic detection unit 12 may be positioned at a position offset from the busbar 11 rather than being entirely overlapped with it. However, it is preferable that a portion of the magnetic detection unit 12 overlaps with the opposing busbar 11 when viewed along the X-axis. The magnetic detection element of the magnetic detection unit 12 can be a magnetoresistive effect element, a Hall element, or the like.

[0025] The case 13 holds the bus bar 11. In the current sensor 1, a part of the bus bar 11 is integrally formed with the case 13 by insert molding.

[0026] The first magnetic shield 14A may be, for example, a stack of multiple metal plates of the same shape. The first magnetic shield 14A blocks disturbance magnetic field noise and reduces the disturbance magnetic field noise applied to the magnetic detection unit 12, thereby improving the disturbance magnetic field noise resistance of the magnetic detection unit 12.

[0027] In the current sensor 1, a first magnetic shield 14A is provided on the surface of the substrate 15 on the X2 side (the other side) in the X-axis direction. The first magnetic shield 14A provided on the X2 side can reduce disturbance magnetic field noise, but a magnetic shield may also be provided on the X1 side of the bus bar 11. By arranging the magnetic detection unit 12 and the bus bar 11 between a pair of flat magnetic shields, the resistance of the magnetic detection unit 12 to disturbance magnetic fields is further improved.

[0028] 15 is a cross-sectional view showing the configuration of a conventional current sensor 90. As shown in the figure, in the current sensor 90, a first magnetic shield 14A is integrally molded with a case 93A, and the first magnetic shield 14A and a substrate 15 are spaced apart.

[0029] 2, in the current sensor 1, the first magnetic shield 14A is held on the surface of the substrate 15 on the X2 side. Therefore, in the current sensor 1, the distance between the first magnetic shield 14A and the substrate 15 is closer than in the current sensor 90 in which the first magnetic shield 14A is spaced apart from the substrate 15, and the dimension in the height direction (X-axis direction) can be reduced, thereby making the current sensor 1 more compact. Furthermore, by positioning the first magnetic shield 14A closer to the magnetic detection unit 12, the shielding effect of the first magnetic shield 14A against external magnetic fields is improved, making the current sensor 1 less susceptible to the influence of external magnetic fields, thereby improving the measurement accuracy of the current sensor 1.

[0030] Furthermore, in the conventional current sensor 90, the substrate 15 on which the magnetic detection unit 12 is mounted is disposed in the space between the cases 93A and 93B. Therefore, when a large current flows through the bus bar 11, there is a risk that the heat generated by the bus bar 11 will heat the air in the space to a temperature exceeding the upper limit operating temperature of the magnetic detection unit 12.

[0031] In contrast, in the current sensor 1, at least a portion of the substrate 15 is exposed to the outside of the resin case 13, and therefore heat can be easily released to the outside via the substrate 15. Therefore, it is possible to prevent the temperature of the space in which the magnetic detection unit 12 is provided from rising due to heat generation by the bus bar 11.

[0032] Furthermore, in the current sensor 1, the first magnetic shield 14A held by the substrate 15 has the other side (X2 side) of the bottom surface facing the substrate 15 exposed to the outside. Therefore, even if a portion of the substrate 15 is covered with the first magnetic shield 14A, the substrate 15 can release heat to the outside via the first magnetic shield 14A. This reduces the temperature rise around the magnetic detection unit 12 due to heat generation by the busbar 11. The substrate 15 can be made of, for example, epoxy glass or ceramic.

[0033] Methods for forming the first magnetic shield 14A on the substrate 15 include, for example, a method of gluing and fixing the first magnetic shield 14A to the substrate 15, a method of stacking the substrate 15 and the first magnetic shield 14A and heating and pressurizing them in a vacuum state (lamination press), a method of printing a paste or the like with magnetic shielding properties on the substrate 15 to form the first magnetic shield 14A, a method of plating the first magnetic shield 14A and soldering it to the substrate 15, and a method of crimping a pin into the first magnetic shield 14A and soldering it to the substrate 15.

[0034] The current sensor 1 includes a spacer 16 between the case 13 and the substrate 15. The spacer 16 separates the bus bar 11 and the magnetic detection unit 12 in the X-axis direction and separates the substrate 15 from the case 13. In the current sensor 1, the spacer 16 is provided integrally with the case 13, so that the spacer 16 can be efficiently manufactured with excellent strength. Note that, although manufacturing efficiency is improved by providing at least a portion of the spacer 16 integrally with the case 13, the spacer 16 may also be formed using a member separate from the case 13.

[0035] 2A and 2B , in the current sensor 1, when viewed along the X-axis direction, the magnetic detection unit 12 is surrounded by the spacer portion 16. Therefore, the magnetic detection unit 12 can be protected by the spacer portion 16.

[0036] The substrate 15 has a protrusion 151 that protrudes in a protrusion direction that is at least one of the Y-axis direction and the Z-axis direction from a position where the substrate 15 is held by the spacer portion 16. In this embodiment, the Y-axis direction (second direction) and the Z-axis direction (third direction) are two directions that are perpendicular to the X-axis direction (first direction) and are also perpendicular to each other.

[0037] 2A , in a cross section of the current sensor 1 cut along the XY plane, if the protrusion 151 is in the Y-axis direction, the protrusion direction includes the Y-axis direction. Furthermore, in a cross section of the current sensor 1 cut along the XZ plane, if the protrusion is present (not shown), the protrusion direction includes the Z-axis direction. The protrusion 151 may protrude in either the Y-axis direction or the Z-axis direction, or in both the Y-axis direction and the Z-axis direction. In this embodiment, the protrusion 151 is provided to protrude in both the Y-axis direction and the Z-axis direction, and the substrate 15 is formed in a rectangular shape when viewed along the X-axis direction.

[0038] Since both surfaces of the protrusion 151 in the X-axis direction, i.e., the two surfaces whose perpendiculars are parallel to the X-axis, are exposed without contacting the case 13 and the spacer portion 16, the heat of the substrate 15 can be efficiently dissipated to the outside from the protrusion 151. This heat dissipation from the protrusion 151 can reduce the temperature rise around the magnetic detection unit 12 provided on the substrate 15 caused by the heat generated by the busbar 11. Therefore, it is possible to suppress deterioration of the measurement accuracy of the current sensor 1 caused by the heat generated by the busbar 11.

[0039] The case 13 has a main body 17 on the X1 side in the X-axis direction of the spacer portion 16. The main body 17 has an extension portion 18 that extends in a direction including the protruding direction from the location where the spacer portion 16 is provided. By providing the extension portion 18 on the main body 17, the protruding portion 151 is protected by the extension portion 18, and when handling the current sensor 1, the risk of the protruding portion 151 colliding with an external obstacle and damaging the board 15 or components provided on the board 15 can be reduced.

[0040] 3 is a cross-sectional view of a current sensor 2 that is a modification of the current sensor 1. As shown in the drawing, the current sensor 2 differs from the current sensor 1 in that the extension portion 18 includes an opposing portion 181 and a protective portion 182.

[0041] The facing portion 181 is a portion of the extending portion 18 that is disposed opposite the protruding portion 151, i.e., that portion of the extending portion 18 that overlaps with the protruding portion 151 when viewed along the X-axis direction. The protective portion 182 is a portion that is located outside the end portion 151E of the protruding portion 151 when viewed along the X-axis direction and does not overlap with the protruding portion 151. By providing the extending portion 18 with the protective portion 182 in addition to the facing portion 181, the extending portion 18 is more likely to come into contact with the outside before the protruding portion 151. This reduces the risk of the protruding portion 151 coming into contact with the outside and damaging the substrate 15, etc.

[0042] Current sensor 2 also differs from current sensor 1 in that current sensor 2 includes second magnetic shield 14B in addition to first magnetic shield 14A. The components are arranged in the following order from the X1 side to the X2 side in the X-axis direction: second magnetic shield 14B, bus bar 11, magnetic detection unit 12, substrate 15, and first magnetic shield 14A.

[0043] The second magnetic shield 14B, which is disposed proximal to the bus bar 11, is integrally formed with the main body 17 of the case 13 together with the bus bar 11. By providing the bus bar 11 and the magnetic detection unit 12 between the first magnetic shield 14A and the second magnetic shield 14B, noise due to disturbance magnetic fields can be effectively suppressed, resulting in a current sensor 2 with high measurement accuracy.

[0044] 4 and 5 are a cross-sectional view and a plan view of a current sensor 3 according to this embodiment. As shown in these figures, the current sensor 3 differs from the current sensors 1 and 2 in that the main body 37 of the case 33 includes a guard portion 383 that extends from the protective portion 382 of the extension portion 38 toward the X2 side in the X-axis direction.

[0045] 4 , the distance L1 in the X-axis direction from the protective portion 382 to the end 383E of the guard portion 383 is equal to or greater than the distance L2 from the protective portion 382 to the installation surface 15S of the substrate 15 for the first magnetic shield 14A and is equal to or less than the distance L3 from the protective portion 382 to the upper surface 14AS of the first magnetic shield 14A (L2≦L1≦L3). Therefore, the end 383E of the guard portion 383 is located between the upper surface 14AS of the first magnetic shield 14A and the installation surface 15S of the substrate 15 for the first magnetic shield 14A.

[0046] 5, the guard portion 383 is spaced apart from the protruding portion 151 when viewed along the X-axis direction, and therefore the guard portion 383 is likely to come into contact with the outside before the protruding portion 151. Therefore, the guard portion 383 protects the protruding portion 151, and the risk of the protruding portion 151 colliding with an external obstacle and damaging the substrate 15, etc., can be reduced.

[0047] Current sensor 3 also differs from current sensors 1 and 2 in that the spacer portion 36 has a communication portion 39 that opens in a direction intersecting the X-axis direction. In current sensor 3, the spacer portion 36 is composed of four columns, and the gaps between adjacent columns correspond to communication portions 39Y that open in the Y-axis direction and communication portions 39Z that open in the Z-axis direction. Note that the spacer portion 36 may be composed of more than four columns, or may have communication portions 39 provided only in either the Y-axis direction or the Z-axis direction. Furthermore, the spacer portion 36 may be formed of a plate-like body with holes that function as communication portions 39. Providing communication portions 39 allows heat to be released to the outside through the communication portions 39, preventing the ambient temperature of the magnetic detection unit 12 from becoming too high.

[0048] <Modification> FIG. 6 is a plan view of a current sensor 4, which is a modification of the current sensor 3 shown in FIGS. 4 and 5 . In the current sensor 4 shown in FIG. 6, at least a portion of the guard portion 483 overlaps with the protrusion 151 when viewed along at least one of the Y-axis direction and the Z-axis direction. That is, the guard portion 483 includes a guard portion 483Y that overlaps with the protrusion 151 when viewed along the Y-axis direction and a guard portion 483Z that overlaps with the protrusion 151 when viewed along the Z-axis direction. With this configuration, the guard portions 483 provided at the four corners of the protective portion 482 of the extension portion 48 can surround each corner of the protrusion 151. This reduces the risk of the protrusion 151 coming into contact with the outside during handling, thereby damaging the substrate 15, etc.

[0049] In Figure 6, all of the guard portions 483 provided at the four corners are configured to include guard portion 483Y and guard portion 483Z, but some or all of the guard portions 483 may be configured to include either guard portion 483Y or guard portion 483Z.

[0050] Fig. 7 is a plan view of a current sensor 5, which is another modified example of the current sensor 3 of Fig. 4. The guard portion 583 of the current sensor 5 shown in the figure is made up of a plurality of plate-like bodies 584, with gaps 585 provided between adjacent plate-like bodies 584. With this configuration, it is possible to adjust the ratio of the plate-like bodies 584 and the gaps 585 that make up the guard portion 583, thereby achieving a balance between protecting the protrusion 151 and the cooling effect of the substrate 15.

[0051] 7, gap 585 is provided between guard portion 583 and plate-like body 584, but gap 585 may be eliminated. This is also true in Fig. 6. Even without gap 585, board 15 and spacer portion 36 are spaced from guard portion 583, so an air passage is ensured and heat can be sufficiently released.

[0052] 8 is a cross-sectional view of a current sensor 6 according to this embodiment. As shown in the drawing, the current sensor 6 differs from the current sensor 1 in FIG. 2A in that the side surface 14AL of the first magnetic shield 14A held by the substrate 65 is covered by the substrate 65.

[0053] The first magnetic shield 14A is formed by punching the outer shape of a plate material that has been surface-treated, such as by plating, on both sides using a press die or the like. Therefore, while the plate surfaces (top surface 14AS and bottom surface) of the first magnetic shield 14A are surface-treated, the side surface 14AL, which becomes the fracture surface caused by the punching process, is not surface-treated. Therefore, if the side surface 14AL is left exposed without undergoing secondary processing such as plating, rust may form on the side surface 14AL, which may then fall onto the surrounding wiring and cause a short circuit or the like.

[0054] Therefore, the current sensor 6 according to this embodiment includes a covering 64 that covers the side surface 14AL of the first magnetic shield 14. In the current sensor 6 shown in Fig. 8, the side surface 14AL of the first magnetic shield 14A is covered with a substrate 65, and the substrate 65 functions as the covering 64. Therefore, even if the side surface 14AL is a fracture surface, it is possible to reduce the occurrence of rust on the side surface 14AL of the first magnetic shield 14A.

[0055] The current sensor 6 covers the side surface 14AL by embedding the first magnetic shield 14A in the substrate 65. Therefore, there is no need to provide a separate cover to cover the side surface 14AL, which makes it possible to reduce the size of the current sensor 6. Note that, since the upper surface 14AS of the first magnetic shield 14A exposed from the substrate 65 is usually subjected to a surface treatment as described above, covering the side surface 14AL consisting of a fractured surface with the substrate 65 (embedding the first magnetic shield 14A in the substrate 65) can prevent the fractured surface from being exposed.

[0056] 9 and 10 are cross-sectional views of a current sensor 6a that is a modified example of the current sensor 6 in Fig. 8 and a current sensor 6b that is another modified example. In the current sensor 6a shown in Fig. 9, the side surface 14AL of the first magnetic shield 14A is covered with an adhesive 66 that bonds the first magnetic shield 14A to the substrate 15, and the adhesive 66 functions as a covering portion 64.

[0057] 10 , a current sensor 6b is attached to a substrate 15 using solder 68 with plating 67 applied to the surface of a first magnetic shield 14A, and a side surface 14AL of the first magnetic shield 14A is covered with the plating 67. Note that, because the first magnetic shield 14A is covered with plating 67 as the covering portion 64, the side surface 14AL does not rust. For this reason, the first magnetic shield 14A may be adhered to the substrate 15 using an adhesive 66 or the like instead of solder 68. Furthermore, when solder 68 is used, the first magnetic shield 14A may be soldered and fixed to the substrate 15 along the entire periphery of the first magnetic shield 14A, only along the side walls, or at points (multiple points).

[0058] 8 to 10 , without attaching a cover to cover the side surface 14AL of the first magnetic shield 14A, the side surface 14AL is covered with the covering portion 64, and the fracture surface of the first magnetic shield 14A can be prevented from being exposed to the outside. Therefore, rusting of the first magnetic shield 14A can be suppressed without increasing the size of the current sensors 6, 6a, 6b.

[0059] 11 and 12 are a perspective view and a cross-sectional view of a current sensor 7 according to this embodiment. FIG. 12 shows a cross section taken along line AA in FIG. 11 . Current sensor 7 differs from current sensors 1 and 2 in that it includes three measurement phases 71, each having a bus bar 11 and a magnetic detection unit 12. The three bus bars 11 are provided in a case 73, and the three magnetic detection units 12 are provided on a substrate 75. While FIGS. 11 and 12 illustrate a current sensor 7 including three measurement phases 71, the present invention may also be implemented as a current sensor including two, four, or more measurement phases 71.

[0060] 13 is a cross-sectional view of a current sensor 8, which is a modified example of the current sensor 7. The current sensor 8 is provided with a set of a first magnetic shield 84A and a second magnetic shield 84B for three measurement phases 71. In other words, the first magnetic shield 84A and the second magnetic shield 84B are provided so as to span the three measurement phases 71. In this way, the first magnetic shield 84A and the second magnetic shield 84B can be shared by multiple measurement phases 71.

[0061] However, when a plurality of measurement phases 71 are provided, if a set of first and second magnetic shields 84A and 84B is provided for the plurality of measurement phases 71 as in the current sensor 8, the first and second magnetic shields 84A and 84B are likely to become magnetically saturated. In contrast, if the first and second magnetic shields 14A and 14B are provided independently for each measurement phase 71 as in the current sensor 7, the first and second magnetic shields 14A and 14B are less likely to become magnetically saturated. Therefore, from the viewpoint of improving measurement accuracy, when a plurality of measurement phases 71 are provided, it is preferable to provide the first and second magnetic shields 14A and 14B independently for each measurement phase 71 as in the current sensor 7.

[0062] Fifth Embodiment FIG. 14 is a cross-sectional view of a current sensor 9 according to this embodiment. As shown in FIG. 14 , in the current sensor 9, the distance D1 in the X-axis direction between the first magnetic shield 94A and the bus bar 11 is greater than the distance D2 in the first direction between the second magnetic shield 94B and the bus bar 11 (D1 > D2). The thickness T1 of the first magnetic shield 94A is smaller than the thickness T2 of the second magnetic shield 94B (T1 < T2). By adjusting the thickness T1 of the first magnetic shield 94A and the thickness T2 of the second magnetic shield 94B according to the distances D1 and D2 from the bus bar 11, the size of the current sensor 9 in the X-axis direction can be reduced. Note that the distances D1 and D2 refer to the center-to-center distances of the respective components in the X-axis direction.

[0063] The performance of the magnetic shield varies depending on the distance from the bus bar 11, the shape of the magnetic shield, etc. Therefore, the thicknesses T1 and T2 may be adjusted to a range that provides an appropriate shielding function depending on the distances D1 and D2 and the shapes of the first magnetic shield 94A and the second magnetic shield 94B. For example, it is preferable to set T1 to about 1 / 2 to 2 / 3 of T2.

[0064] The embodiments disclosed in this specification are illustrative in all respects and are not limited to these embodiments. The scope of the present invention is defined by the claims rather than by the description of the above-mentioned embodiments alone, and is intended to include all modifications within the meaning and scope of the claims.

[0065] In this example, the relationship between the installation position of the first magnetic shield 14A and the error was measured. The measurement targets were the current sensor 7 according to the fourth embodiment shown in FIG. 12 and the conventional current sensor 100 shown in FIG. 16.

[0066] Fig. 16 is a cross-sectional view of a conventional current sensor 100 having three measurement phases. Current sensor 100 differs from current sensor 7 of Fig. 12 in that first magnetic shield 14A is integrally molded with case 103A. For current sensor 7 and current sensor 100, the distance between adjacent measurement phases 71 was set to 20 mm, and current was passed through bus bars 11 under the same conditions, and errors caused by the influence of adjacent bus bars 11 were measured.

[0067] The error of current sensor 7 was 0.03%, while the error of current sensor 100 was 0.1%. This result shows that by providing first magnetic shield 14A on substrate 15, it is possible to reduce errors caused by the influence of adjacent bus bars 11 more than when first magnetic shield 14A is formed integrally with case 103A.

[0068] INDUSTRIAL APPLICABILITY The present invention is useful as a current sensor provided with a bus bar through which a large current flows as a current to be measured.

[0069] DESCRIPTION OF SYMBOLS 1, 2, 3, 4, 5, 6, 6a, 6b, 7, 8, 9: Current sensor 11: Bus bar 12: Magnetic detection portion 13: Case 14A: First magnetic shield 14AL: Side surface 14AS: Top surface 14B: Second magnetic shield 15: Board 15S: Installation surface 151: Protrusion 151E: End portion 16: Spacer portion 17: Main body 18: Extension portion 181: Opposing portion 182: Protective portion 33: Case 36: Spacer portion 37: Main body 38: Extension portion 382: Protective portion 383: Guard portion 383E: End portion 39: Communication portion 39Y: Communication portion 39Z: Communication portion 48: Extension portion 482: Protective portion 483: Guard portion 483Y: Guard portion 483Z: Guard portion 583: Guard portion 584: Plate-shaped body 585: Gap 64: Covering portion 65: Substrate 66: Adhesive 67: Plating 68: Solder 71: Measurement phase 73: Case 75: Substrate 84A: First magnetic shield 84B: Second magnetic shield 90: Current sensor 93A: Case 93B: Case 94A: First magnetic shield 94B: Second magnetic shield 100: Current sensor 103A: Case D1: Distance D2: Distance L1: Distance L2: Distance L3: Distance T1: Thickness T2: Thickness

Claims

1. A bus bar through which a current to be measured flows; a magnetic detection unit capable of detecting a magnetic field generated when the current to be measured flows through the bus bar; A case for holding the bus bar; a first magnetic shield capable of suppressing disturbance magnetic field noise applied to the magnetic detection unit; a substrate on one side of a first direction, a second direction, and a third direction, the first direction being three directions perpendicular to each other; and the magnetic detection unit is disposed on the one side of the first direction, a current sensor including the bus bar, the magnetic detection unit, the substrate, and the first magnetic shield arranged in this order from one side in the first direction, a spacer portion provided between the case and the substrate to separate the bus bar and the magnetic detection portion in the first direction; the substrate includes a protruding portion that protrudes in a protruding direction that is at least one of the second direction and the third direction from a position where the substrate is held by the spacer portion, the case includes a main body on one side of the spacer portion in the first direction, the main body includes an extension portion extending in a direction including the protruding direction from a position where the spacer portion is provided, When viewed in the first direction, the extension portion includes an opposing portion that overlaps with the protruding portion and a protective portion that is located outside an end of the protruding portion, the case includes a guard portion extending from the protection portion to the other side in the first direction, When viewed in the first direction, the guard portion is spaced from the protrusion, A current sensor characterized in that the distance from the protective part to the end of the guard part in the first direction is greater than or equal to the distance from the protective part to the installation surface of the first magnetic shield on the substrate and is less than or equal to the distance from the protective part to the top surface of the first magnetic shield.

2. A bus bar through which a current to be measured flows; a magnetic detection unit capable of detecting a magnetic field generated when the current to be measured flows through the bus bar; A case for holding the bus bar; a first magnetic shield capable of suppressing disturbance magnetic field noise applied to the magnetic detection unit; a substrate on one side of a first direction, a second direction, and a third direction, the first direction being three directions perpendicular to each other; and the magnetic detection unit is disposed on the one side of the first direction, a current sensor including the bus bar, the magnetic detection unit, the substrate, and the first magnetic shield arranged in this order from one side in the first direction, a spacer portion provided between the case and the substrate to separate the bus bar and the magnetic detection portion in the first direction; the substrate includes a protruding portion that protrudes in a protruding direction that is at least one of the second direction and the third direction from a position where the substrate is held by the spacer portion, the case includes a main body on one side of the spacer portion in the first direction, the main body includes an extension portion extending in a direction including the protruding direction from a position where the spacer portion is provided, When viewed in the first direction, the extension portion includes an opposing portion that overlaps with the protruding portion and a protective portion that is located outside an end of the protruding portion, the case includes a guard portion extending from the protection portion to the other side in the first direction, When viewed in the first direction, the guard portion is spaced from the protrusion, When viewed along at least one of the second direction and the third direction, at least a portion of the guard portion overlaps with the protruding portion, The current sensor according to claim 1, wherein the guard portion is a plurality of plate-like bodies, and gaps are provided between adjacent plate-like bodies.

3. The current sensor according to claim 1 , wherein the spacer portion is provided integrally with the case.

4. the first magnetic shield is supported by the substrate; The current sensor according to claim 1 , wherein a side surface of the first magnetic shield is covered by a covering portion.

5. a plurality of measurement phases each including the bus bar and the magnetic detection unit; The current sensor according to claim 1 , wherein the first magnetic shield is provided independently for each of the measurement phases.

6. The current sensor according to claim 1 , wherein the spacer portion has a communication portion that opens in the second direction and / or the third direction.

7. The current sensor according to claim 1 , wherein the spacer portion surrounds the magnetic detection portion when viewed in the first direction.

8. Further comprising a second magnetic shield; The current sensor according to claim 1 , wherein the second magnetic shield, the bus bar, the magnetic detection portion, the substrate, and the first magnetic shield are arranged in this order from one side in the first direction.

9. a distance in the first direction between the first magnetic shield and the bus bar is greater than a distance in the first direction between the second magnetic shield and the bus bar; The current sensor of claim 8 , wherein a thickness of the first magnetic shield is less than a thickness of the second magnetic shield.