Current sensor
Patent Information
- Application Number
- JP2025541298
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Priority Date
- 2023-08-24
- Filing Date
- 2024-02-21
- Publication Date
- 2025-02-27
Abstract
Description
Current Sensor
[0001] The present invention relates to a current sensor equipped with a magnetic shield, which measures a current to be measured flowing through a bus bar.
[0002] In recent years, current sensors have been used to measure the current flowing through various devices in order to control the power supply systems of vehicles and other devices. Patent Document 1 describes a current sensor with a pair of magnetic shield plates sandwiching a conductor and a magnetoelectric transducer, aiming to reduce wasted space between the pair of magnetic shield plates and improve the accuracy of the current sensor. The pair of magnetic shields in the current sensor described in this document are integrally formed with a resin package serving as a housing, along with a sensor substrate and bus bars. However, a configuration in which the magnetic shield plates and the housing are integrally formed, as in this current sensor, makes it difficult to reduce the size, weight, and cost of the current sensor. Patent Document 2 describes a current sensor in which, for the purpose of high-precision current detection, the magnetic shield on the magnetic detection unit side, which includes a magnetic detection element, of the pair of magnetic shields that block external magnetic fields is fixed to a circuit board by a fixing member.
[0003] International Publication No. WO2016 / 148032 Japanese Patent Application Laid-Open No. 2018-96793
[0004] The current sensor described in Patent Document 2 has an advantage over the current sensor described in Patent Document 1 in terms of size, weight, and cost because the magnetic shield installed on the magnetic detection unit side is configured separately from the housing. In the current sensor described in Patent Document 2, the relative positions of the magnetic shield and the circuit board on which the magnetic detection element is provided are fixed by inserting fixing members into fixing holes provided at the four corners of the magnetic shield. That is, the fixing holes of the magnetic shield are aligned with through holes formed in the circuit board, and fixing members are inserted into the holes to fix the magnetic shield to the circuit board. In this way, the magnetic shield is positioned at a predetermined position on the circuit board based on the position of the holes. Therefore, an object of the present invention is to provide a current sensor in which a magnetic shield configured separately from the housing can be easily positioned at a predetermined position on the board when fixed to the board on which the magnetic detection unit is provided.
[0005] To solve the above-described problems, the present invention has the following configuration: a current sensor including a bus bar through which a current to be measured flows, a magnetic sensor disposed opposite the bus bar and configured to detect a magnetic field generated by the bus bar, a substrate on which the magnetic sensor is provided, a pair of flat first and second magnetic shields sandwiching the bus bar, the magnetic sensor, and the substrate, and a case on which the bus bar and the second magnetic shield are provided, the current sensor being stacked in this order: the first magnetic shield, the substrate, and the case; the first magnetic shield having a protrusion protruding from a first surface facing the substrate and a first reference portion for positioning; the substrate having an engaging portion engageable with the protrusion and a second reference portion for positioning; the case having a third reference portion for positioning; and when the protrusion and the engaging portion are engaged, the first reference portion, the second reference portion, and the third reference portion are aligned on a straight line parallel to a stacking direction of the first magnetic shield, the substrate, and the case. By engaging the protrusion on the first magnetic shield with the engaging portion on the substrate, it becomes easier to align the first magnetic shield with the substrate.
[0006] The first magnetic shield may be formed by stacking a plurality of thin plate members, and the protruding portion may be a press-jointed portion formed by crimping the plurality of thin plate members in the stacking direction. By using the press-jointed portion formed when crimping the first magnetic shield, which is formed by stacking a plurality of thin plate members, as the protruding portion and engaging it with an engaging portion of the substrate, it is possible to reduce component processing costs and man-hours, and suppress manufacturing costs.
[0007] The first reference portion may be provided on a first thin plate member adjacent to the substrate among the plurality of thin plate members included in the first magnetic shield. By providing a first reference portion for positioning on a first thin plate member among the plurality of thin plate members constituting the first magnetic shield, it becomes easier to position the first magnetic shield at a predetermined position on the substrate than if the first reference portion were provided on all thin plate members. For example, if a shield hole penetrating the first magnetic shield is used as the first reference portion, providing the first reference portion only on the first thin plate member can shorten the length of the shield hole. This allows for easier insertion of a fixing member. Furthermore, the shortened length of the member improves the strength with which the first magnetic shield is fixed and is advantageous for reducing the size and height of the current sensor.
[0008] A plurality of pairs of the protrusions and the engaging portions may be provided. By providing a plurality of pairs of the protrusions and the engaging portions and engaging each pair, it becomes easier to position the first magnetic shield and the substrate, and the positioned state can be maintained.
[0009] The first reference portion may be a shield hole penetrating the first magnetic shield, the second reference portion may be a board hole penetrating the board, and the third reference portion may be a fixing boss having a retaining portion at a tip of the fixing boss, and the first magnetic shield and the board may be fixed to the case by the retaining portion when the fixing boss is inserted into the shield hole and the board hole. By fixing the first magnetic shield and the board to the case by the retaining portion when the fixing boss is inserted into the shield hole and the board hole, the first magnetic shield, the board, and the case can be positioned in predetermined positions and fixed in a stacked state.
[0010] The first magnetic shield may be formed by stacking a plurality of thin plate members, and the anti-slip portion may be in contact with an exposed portion of a second surface opposite to a first surface facing the substrate of a thin plate member other than a second thin plate member that is the furthest from the substrate in the stacking direction among the plurality of thin plate members.
[0011] When any of the thin plate members arranged between the first thin plate member and the second thin plate member adjacent to the substrate is a third thin plate member, the first magnetic shield may have a hole or cutout portion formed continuously from the second thin plate member along the stacking direction to the third thin plate member, and the second surface exposed from the hole or cutout portion may be the exposed portion.
[0012] The magnetic shield may further include a fixing screw, the first reference portion being a shield hole penetrating the first magnetic shield, the second reference portion being a board hole penetrating the board, and the third reference portion being a screw hole that can be threadedly engaged with the fixing screw, and the first magnetic shield and the board may be fixed to the case by the screw head of the fixing screw when the fixing screw is inserted through the shield hole and the board hole. By inserting the fixing screw into the shield hole and the board hole and fixing the first magnetic shield and the board to the case by the screw head of the fixing screw, the first magnetic shield, the board, and the case can be fixed in a stacked state in predetermined positions.
[0013] The first magnetic shield may be formed by stacking a plurality of thin plate members, and the screw head may be in contact with an exposed portion of a second surface of a thin plate member other than the second thin plate member that is the furthest away from the substrate in the stacking direction, the second surface being opposite to the first surface facing the substrate.
[0014] When any of the thin plate members arranged between the first thin plate member and the second thin plate member adjacent to the substrate is a third thin plate member, the first magnetic shield may have a hole or cutout portion formed continuously from the second thin plate member along the stacking direction to the third thin plate member, and the second surface exposed from the hole or cutout portion may be the exposed portion.
[0015] The first magnetic shield may be formed by stacking a plurality of thin plate members, and of the plurality of thin plate members that the first magnetic shield has, the first thin plate member adjacent to the substrate may have an exposed portion that is exposed on the second surface opposite to the first surface facing the substrate, and the exposed portion may form part of a step portion or a recessed portion.
[0016] With the above configuration, the length of the fixing boss or fixing screw is shorter than when the retaining portion or screw head is located on the second surface of the second thin plate member of the first magnetic shield, which makes it easier to stack the first magnetic shield and also enables the first magnetic shield and the board to be more firmly fixed to the case.
[0017] The present invention makes it easy to align the first magnetic shield with the substrate, thereby providing a current sensor that can be easily positioned at a predetermined position on the substrate when the magnetic shield, which is configured as a separate part from the housing, is fixed to the substrate on which the magnetic detection unit is provided.
[0018] 1 is a perspective view schematically showing the appearance of the current sensor according to the first embodiment; FIG. 2 is a cross-sectional view schematically showing the configuration of a main part of the current sensor taken along line AA in FIG. 1; FIG. 3 is a cross-sectional view schematically showing the configuration of a modified example of the current sensor of FIG. 2; FIG. 4 is a plan view of the current sensor of FIG. 3; FIG. 5 is an explanatory diagram of the structure of a magnetic shield having a conventional laminated structure; FIG. 6 is an explanatory diagram of the structure of a magnetic shield having a laminated structure in the current sensor of the present invention; FIG. 7 is a cross-sectional view schematically showing the configuration of another modified example of the current sensor of FIG. 2; FIG. 8 is a cross-sectional view schematically showing the configuration of another modified example of the current sensor of FIG. 2; FIG. 9 is a plan view schematically showing the configuration of the current sensor of FIG. 8; FIG. 10 is a cross-sectional view schematically showing the configuration of a modified example of the current sensor of FIG. 10; FIG. 11 is a plan view schematically showing the configuration of the current sensor of FIG. 12; FIG. 12 is a cross-sectional view schematically showing the configuration of a conventional current sensor; FIG. 13 is a cross-sectional view schematically showing the configuration of a current sensor without a cover.
[0019] [First Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. The same components in each drawing are designated by the same numbers, and descriptions thereof will be omitted where appropriate. Reference coordinates are shown in each drawing as appropriate to indicate the positional relationship of each component. In the reference coordinates, the width dimension direction of the bus bar is defined as the X direction (third direction), the extension direction of the bus bar perpendicular to the X direction is defined as the Y direction (second direction), and the stacking direction of the bus bar and magnetic sensor perpendicular to the X and Y directions is defined as the Z direction (first direction). The X direction is the direction of the sensitivity axis of the magnetic sensor, and the Y and Z directions are perpendicular to the sensitivity axis.
[0020] FIG. 14 is a cross-sectional view schematically illustrating the configuration of a conventional current sensor 100. The current sensor 100 shown in the figure includes a bus bar 101 through which a current to be measured flows, and a pair of parallel plate-shaped magnetic shields 104A and 104B sandwiching a magnetic sensor 102 mounted on a substrate 103. The magnetic shield 104A is insert-molded into a cover 106, and the magnetic shield 104B is insert-molded into a case 105. This configuration, which includes a case 105 and a cover 106 and magnetic shields 104B and 104A, respectively, makes it difficult to reduce the size and thickness of the current sensor 100 and is also disadvantageous in terms of cost reduction. Therefore, the following describes an embodiment of the present invention, which is a current sensor that does not include a cover 106 that holds the magnetic shield 104A, but which is advantageous in terms of size, thickness, and cost reduction.
[0021] FIG. 15 is a cross-sectional view schematically illustrating the configuration of a current sensor 110 without a cover. Because the current sensor 110 shown in the figure does not include a cover, the magnetic shield 104A, out of the pair of magnetic shields 104A and 104B, is directly attached to the substrate 103. In this manner, when the magnetic shield 104A provided on the magnetic sensor 102 side is directly attached to the substrate 103 using the bus bar 101 as a reference, it is difficult to position the magnetic shield 104A at a predetermined position on the substrate 103. Therefore, the current sensor of the present invention is configured to stably, easily, and accurately determine the position of the magnetic shield 104A relative to the substrate 103. Embodiments of the current sensor of the present invention are described below.
[0022] Fig. 1 is a perspective view schematically illustrating the appearance of a current sensor 10 according to this embodiment. Fig. 2 is a cross-sectional view schematically illustrating the configuration of a main part of the current sensor 10 taken along line AA in Fig. 1. The current sensor 10 includes a bus bar 11, a magnetic sensor 12, a substrate 13, a pair of flat-plate-type magnetic shields 14A (first magnetic shield) and 14B (second magnetic shield), and a case 15. The magnetic shield 14A, substrate 13, magnetic sensor 12, bus bar 11, and magnetic shield 14B are stacked in this order in the Z2 to Z1 direction, and the bus bar 11 and magnetic shield 14B are provided in the case 15.
[0023] The bus bar 11 is a plate-shaped conductor through which the current to be measured flows, and is made of, for example, copper, brass, aluminum, or the like. The magnetic sensor 12 detects the magnetic field generated by the bus bar 11 when the current to be measured flows through it, and is provided on the Z1-side surface 13a of the substrate 13 so as to face the bus bar 11 in the Z direction. The detection surface of the magnetic sensor 12 faces the bus bar 11, and its sensitivity axis is parallel to the detection surface. The induced magnetic field generated near the detection surface of the magnetic sensor 12 when the current to be measured flows through the bus bar 11 contains a large component in the X direction. Therefore, by positioning the magnetic sensor 12 so that its sensitivity axis is parallel to the X direction, the magnetic field generated by the bus bar 11 can be detected with high accuracy.
[0024] A magnetoresistive effect element, a Hall element, or the like can be used as the detection element in the magnetic sensor 12. Note that the above-described configuration exemplifies the case where a magnetoresistive effect element is used as the detection element of the magnetic sensor 12. When using other detection elements, it is necessary to appropriately change the orientation of the detection surface, etc., before placing the element.
[0025] The magnetic shields 14A and 14B are arranged in the Z direction to sandwich the bus bar 11, the magnetic sensor 12, and the substrate 13, and are made of metal plates or the like. The magnetic shields 14A and 14B can suppress magnetic noise to the magnetic sensor 12, thereby improving the measurement accuracy of the current sensor 10.
[0026] Case 15 may be configured such that bus bar 11 and magnetic shield 14B are integrally formed by, for example, insert molding, etc. Alternatively, bus bar 11 may be provided by inserting bus bar 11 into case 15 that has been integrally molded with magnetic shield 14B by insert molding.
[0027] The magnetic shield 14A has a protrusion 141 that protrudes from an opposing surface 14Aa (first surface) that faces the substrate 13. The magnetic shield 14A also has, as a first reference portion, a hole 142 (shield hole) that penetrates in the Z direction and through which a fixing boss 152 (described later) can be inserted.
[0028] The substrate 13 has an engaging portion 131 that can engage with the protrusion 141 on an opposing surface 13b on the Z2 side that faces the magnetic shield 14A, opposite the surface 13a on which the magnetic sensor 12 is provided. Since the engaging portion 131 only needs to be able to engage with the protrusion 141, it may be, for example, a recess that does not penetrate in the Z direction and that corresponds to the shape of the protrusion 141, instead of a hole that penetrates in the Z direction.
[0029] By engaging the protrusions 141 of the magnetic shield 14A with the engagement portions 131 of the substrate 13, it becomes easy to determine the relative positional relationship between the magnetic shield 14A and the substrate 13. In other words, by fitting the protrusions 141 into the engagement portions 131, the magnetic shield 14A and the substrate 13 can be easily aligned.
[0030] 2, from the viewpoint of performing alignment reliably and easily, current sensor 10 preferably includes multiple pairs of protrusions 141 and engagement portions 131. By providing multiple pairs of protrusions 141 and engagement portions 131 and engaging each pair, it becomes easier to position magnetic shield 14A and substrate 13, and the aligned state can be reliably maintained.
[0031] The substrate 13 has a hole 132 that penetrates in the Z direction as a second reference portion for positioning, into which a fixing boss 152 (described later) can be inserted. By engaging the protrusion 141 with the engaging portion 131, the magnetic shield 14A is positioned at a predetermined position on the substrate 13, so that the hole 142 in the magnetic shield 14A overlaps with the hole 132 (substrate hole) in the substrate 13. In other words, when viewed along the Z direction, the hole 142 in the magnetic shield 14A and the hole 132 in the substrate 13 can be overlapped to form a continuous hole.
[0032] Case 15, made of resin or the like, is integrally formed with busbar 11 and magnetic shield 14B, which are insert-molded. Case 15 has a storage recess 151 on the side facing substrate 13. Inside storage recess 151, there is a fixing boss 152 that protrudes in the Z2 direction and serves as a third reference portion for positioning.
[0033] By engaging the protrusion 141 with the engaging portion 131, the holes 142 and 132 are aligned when viewed in the Z direction. This allows the fixing boss 152, which serves as a third reference portion, to be easily inserted into the holes 142 and 132. By inserting the fixing boss 152, the positional relationship between the magnetic shield 14A, the substrate 13, and the case 15 is determined. In this state, the holes 142, 132, and the fixing boss 152 are aligned on a straight line L that is parallel to the stacking direction (Z direction) of the magnetic shield 14A, the substrate 13, and the case 15.
[0034] With fixing boss 152 inserted through hole 142 and hole 132, magnetic shield 14A and substrate 13 are fixed to case 15 by retaining portion 153 provided at the Z2 side end (tip) of fixing boss 152. Note that retaining portion 153 is formed by, for example, heat caulking the Z2 side end (tip) of fixing boss 152 after fixing boss 152 is inserted through hole 142 and hole 132.
[0035] The outer dimension of retaining portion 153, as viewed in the Z direction, is larger than the inner diameters of holes 142 and 132. Retaining portion 153 is in close contact with surface 14Ab of magnetic shield 14A on the Z2 side. Therefore, retaining portion 153 functions as a retaining member that holds magnetic shield 14A and substrate 13 in predetermined positions in case 15.
[0036] The magnetic shield 14A, the substrate 13, and the case 15 are fixed in position by the retaining portion 153 with the magnetic sensor 12 on the substrate 13 positioned opposite the bus bar 11 in the storage recess 151.
[0037] As described above, in current sensor 10, the relative positions of magnetic shield 14A, substrate 13, bus bar 11, and magnetic shield 14B can be determined in a state where they are stacked and arranged in this order from Z2 to Z1. By fixing substrate 13 and magnetic shield 14A in predetermined positions using case 15 as a reference, it is possible to prevent misalignment of bus bar 11, magnetic shield 14A, and magnetic shield 14B with respect to magnetic sensor 12 provided on substrate 13. Therefore, errors due to misalignment are suppressed, resulting in current sensor 10 with good measurement accuracy.
[0038] 3 and 4 are cross-sectional and plan views schematically illustrating the configuration of a current sensor 20 that is a modification of the current sensor 10 in Fig. 2. The current sensor 20 shown in these figures differs from the current sensor 10 in Fig. 2 in that, instead of the magnetic shields 14A and 14B each made of a single metal plate, the current sensor 20 includes magnetic shields 24A and 24B each made of a plurality of stacked metal plates of the same shape.
[0039] Before describing the magnetic shield 24A included in the current sensor 20, the structure of a magnetic shield 114A having a typical conventional laminated structure will be described. Fig. 5 is an explanatory diagram of the structure of the magnetic shield 114A having a conventional laminated structure. As shown in Fig. 5(a), the magnetic shield 114A has a configuration in which multiple metal plates are stacked and hammered from above (Z2 side) with a punch to caulk them. Fig. 5(b) shows the cross-sectional structure of the portion indicated by line B-B in Fig. 5(a).
[0040] If multiple metal plates are simply stacked and hammered with a punch to secure them together, a shape like the protruding portion 141 of the magnetic shield 14A shown in the first embodiment will be created. If there is variation in the amount of protrusion or shape of such a portion, problems such as tilting may occur even when the plate is placed on a flat surface.
[0041] 5B, in the magnetic shield 114A having a conventional laminated structure, a hole 1141 is provided in the metal plate 114A1 arranged on the lowest side (Z1 side), and when viewed in the Z direction, the portion overlapping the hole 1141 is struck with a punch from the upper surface 114Ab to crimp the metal plates 114A1 to 114A4. At this time, the protrusion of the metal plate 114A2 adjacent to the metal plate 114A1 is press-fitted into the hole 1141. This prevents the formation of a convex portion protruding from the lower opposing surface 114Aa of the magnetic shield 114A, as indicated by the dashed dotted line.
[0042] 6 is an explanatory diagram of the structure of a magnetic shield 24A with a laminated structure included in the current sensor 20. As shown in (a) of the same figure, the magnetic shield 24A is the same as the conventional magnetic shield 114A of FIG. 5 in that multiple metal plates are stacked and hammered from above (Z2 side) with a punch to be crimped.
[0043] However, in the magnetic shield 24A, as shown in the cross-sectional view of FIG. 6B, no hole is provided in the bottommost metal plate 24A1 in the crimped portion indicated by line B-B in FIG. 6A. Therefore, in all of the metal plates 24A1 to 24A4, a recess is formed on the upper surface 24Ab of the crimped portion, and a protrusion is formed on the opposing surface 24Aa facing the lower substrate 13. Therefore, a press-jointed portion 241, which is formed when the magnetic shield 24A is crimped by hitting with a punch and protrudes from the lower opposing surface 24Aa indicated by the dashed line, is used to align the magnetic shield 24A with the substrate 13. In other words, the press-jointed portion 241 crimped in the stacking direction of the magnetic shield 24A is used as a protrusion that engages with the engaging portion 131 of the substrate 13.
[0044] As described above, in the magnetic shield 24A, a portion of the press-jointed portion 241 necessary for processing protrudes from the opposing surface 24Aa of the magnetic shield 24B that faces the substrate 13, and is used as a protrusion that engages with the engaging portion 131 of the substrate 13. By using the press-jointed portion 241 as a protrusion in this manner, it is possible to easily align the magnetic shield 24A with the substrate 13, reduce component processing costs and man-hours, and suppress the manufacturing cost of the magnetic shield 24A. Note that the magnetic shield 24B may have a structure that has a protrusion on one surface, like the magnetic shield 24A, or may have a structure that does not have a protrusion, like the conventional magnetic shield 114A.
[0045] Fig. 7 is a cross-sectional view schematically showing a current sensor 30, which is another modified example of the current sensor 20 in Fig. 3. The current sensor 30 is provided with a fixing screw 31, and differs from the current sensor 10 in that a screw hole 154 that can be threaded with the fixing screw 31 is provided in the case 15 as a third reference portion. When viewed along the Z direction, the inner diameters of the hole 242 (first shield hole) and the hole 132 are larger than the threaded portion of the fixing screw 31 and smaller than the outer diameter of the screw head 32.
[0046] In the current sensor 30, the magnetic shield 24A and the substrate 13 are fixed to the case 15 by the screw head 32 of the fixing screw 31 with the fixing screw 31 inserted through the hole 242 and the hole 132. This allows the magnetic shield 24A, the substrate 13, and the case 15 to be fixed in a stacked state in predetermined positions with the fixing screw 31 acting as a holding member.
[0047] 8 and 9 are a cross-sectional view and a plan view schematically showing the appearance of a current sensor 35, which is another modified example of the current sensor 20 in Fig. 3. As shown in these figures, the current sensor 35 differs from the current sensor 20 in that the magnetic shield 24A, the substrate 13, and the case 15 are fixed by two fixing bosses 152 and two fixing screws 31.
[0048] As in the current sensor 35, different fixing means may be used in combination to fix the magnetic shield 24A, the substrate 13, and the case 15. The different fixing means may be combined and arranged differently from that shown in FIG. 9. For example, one fixing boss 152 may be combined with three fixing screws 31, or three fixing bosses 152 may be combined with one fixing screw 31. Also, a configuration may be adopted in which a retaining portion 153 is provided at the tip of all or part of each fixing boss 152. While FIG. 9 shows an example in which four fixing means are provided on the magnetic shield 24A, the number of fixing means is not limited to four and may be, for example, two, three, five or more.
[0049] 10 and 11 are a cross-sectional view and a plan view, respectively, illustrating a configuration of a current sensor 40 according to a second embodiment of the present invention. As shown in the drawings, the current sensor 40 differs from the current sensor 20 of FIG. 3 in that the current sensor 40 includes a magnetic shield 44A instead of the magnetic shield 24A.
[0050] The magnetic shield 44A has a hole 442 as a first reference portion provided only in the thin plate member 44A1 (first thin plate member) adjacent to the substrate 13 among the plurality of thin plate members 44A1, 44A2, 44A3, and 44A4 that the magnetic shield 44A has.
[0051] In other words, when the plurality of thin plate members 44A1, 44A2, 44A3, and 44A4 are viewed from the Z2 side, the thin plate member 44A1 has an exposed portion 444 that protrudes from the thin plate members 44A2, 44A3, and 44A4, and a hole 442 is provided in the exposed portion 444. Furthermore, when the Z2 side is considered to be the top, the exposed portion 444 is located at a lower position (on the Z1 side) than the upper surface of the thin plate member 44A4, and a step portion 445 is formed.
[0052] By forming the hole 442 in the exposed portion 444 of the thin plate member 44A1, the retaining portion 153 can be disposed in the step portion 445. This reduces the amount of protrusion of the retaining portion 153 from the upper surface of the thin plate member 44A4 compared to when the retaining portion 153 is disposed on the upper surface of the thin plate member 44A4. In other words, it is possible to achieve a smaller size and a lower height in the Z direction.
[0053] Furthermore, by forming the holes 442 in the exposed portions 444 of the thin plate member 44A1, the depth of the holes 442 in the stacking direction is reduced. This makes it easier to fit the holes 442 into the fixing bosses 152. Furthermore, the length of the fixing bosses 152 in the Z direction is reduced, improving the strength of the fixing bosses 152. Therefore, by fitting the holes 442 of the magnetic shield 44A and the holes 132 of the substrate 13 into the fixing bosses 152 of the case 15 and then fixing them, the magnetic shield 44A and the substrate 13 can be more firmly fixed to the case 15.
[0054] 10, the cutout portions 443 are formed continuously from the thin plate member 44A4 (second thin plate member) that is the farthest from the substrate 13 in the stacking direction (Z direction) among the thin plate members 44A1 to 44A4 to the thin plate member 44A2 (third thin film member) adjacent to the thin plate member 44A1. That is, the cutout portions 443 are formed in the thin plate members 44A2 to 44A4 other than the thin plate member 44A1, and the hole 442 is formed in the exposed portion 444 of the thin plate member 44A1 that is exposed when viewed from the surface 44Ab (second surface) of the magnetic shield 44A.
[0055] As described above, the magnetic shield 44A has a hole or cutout 443 formed in the thin plate members 44A2 and 44A3 (third thin plate members) arranged between the thin plate member 44A1 (first thin plate member) and the thin plate member 44A4 (second thin plate member) in the stacking direction (Z direction) from the thin plate member 44A4 to the thin plate member 44A2. When viewed from the Z2 to Z1 direction, the surface 44Ab exposed from the cutout 443 is the exposed portion 444.
[0056] In the magnetic shield 44A, a hole 442 serving as a first reference portion is provided only in the thin plate member 44A1 serving as the first thin plate member, and a step portion 445 is formed by an exposed portion 444 of the thin plate member 44A1 and the end faces of the thin plate members 44A2 to 44A4 in the Y direction. In other words, a part of the step portion 445 is formed by the exposed portion 444.
[0057] 11 , when viewed along the Z direction, the retaining portion 153 is brought into contact with the exposed portion 444, and the exposed portion 444 serves as a holding surface to hold the magnetic shield 44A and the substrate 13. In this way, the magnetic shield 44A can be fixed at a predetermined position in the case 15.
[0058] 10 and 11, when the magnetic shield 44A is viewed along the stacking direction, the thin plate member 44A1 in contact with the substrate 13 is formed larger than the other thin plate members 44A2 to 44A4. A hole 442 (shield hole) serving as a first reference portion is formed in an exposed portion 444 of the thin plate member 44A1 that protrudes from the other thin plate members 44A2 to 44A4.
[0059] 10, thin plate members 44A2 to 44A4 have the same shape and size, but are each formed in a different shape from thin plate member 44A1. However, this is not limiting, and for example, thin plate member 44A2 may be formed in the same shape and size as thin plate member 44A1, and thin plate members 44A3 to 44A4 may be formed in a different shape from thin plate member 44A1. In this case, when viewed from the Z2 to Z1 direction, the portion of the Z2-side surface of thin plate member 44A2 that protrudes from thin plate members 44A3 to 44A4 may be an exposed portion 444, and holes 442 may be provided that penetrate thin plate members 44A2 and 44A1.
[0060] In other words, when multiple thin plate members (large plate members) stacked in succession, including thin plate member 44A1, are formed to have the same shape and size and have portions that protrude from the remaining thin plate members (small plate members) including thin plate member 44A4, an exposed portion 444 may be formed on the Z2 side of the large plate member farthest from the substrate 13, and a hole 442 that penetrates all of the large plate members may be formed in exposed portion 444.
[0061] According to this configuration, when viewed along the stacking direction, any one of thin plate members 44A1 to 44A3 among thin plate members 44A1 to 44A4 is exposed. That is, an exposed portion 444 is formed on a thin plate member other than thin plate member 44A4 that is farthest from substrate 13 in the stacking direction, at 44Ab opposite to opposing surface 44Aa that faces substrate 13. Then, retaining portion 153 comes into contact with exposed portion 444, thereby fixing magnetic shield 44A, substrate 13, and case 15 together.
[0062] Furthermore, the hole 442 is shorter than when the exposed portion 444 is formed in the thin plate member 44A4. This allows the fixing boss 152 to be easily fitted into the hole 442. Furthermore, the shortening of the fixing boss 152 improves the strength of the current sensor 40.
[0063] 10 and 11 show an embodiment in which the retaining portions 153 are used for fastening, but the screw heads 32 may be used in place of some or all of the retaining portions 153. Even when the fixing screws 31 are used instead of the fixing bosses 152, by providing holes 442 in one or more of the thin plate members 44A1 to 44A3 other than the thin plate member 44A4, the length of the holes 442 in the Z direction is shortened, thereby reducing the workload of the work of fastening the magnetic shield 44A and the substrate 13 to the case 15 and improving the fastening strength.
[0064] 10 and 11, the cutout portion 443 is formed over the entire Y-direction ends, but it may be formed only around the first reference portion (hole 442). By reducing the cutout area, it is possible to suppress deterioration of the shielding performance.
[0065] 12 and 13 are cross-sectional and plan views schematically illustrating the configuration of a current sensor 50 that is a modification of the current sensor 40 of FIG. 10. The magnetic shield 44A of the current sensor 50 shown in these figures differs from the current sensor 40 in that holes 446 are formed in the thin plate members 44A2 to 44A4 instead of the cutouts 443. When viewed from the Z2 direction to the Z1 direction, the current sensor 50 defines recessed portions 447 by the exposed portions 444 of the thin plate member 44A1 exposed from the holes 446 and the Y-direction end faces of the thin plate members 44A2 to 44A4.
[0066] The magnetic shield 44A of the current sensor 50 has holes 446 formed continuously along the stacking direction from the thin plate members 44A4 to 44A2. The magnetic shield 44A and the substrate 13 are fixed to the case 15 by the retaining portion 153 coming into contact with the exposed portion 444 of the thin plate member 44A4 exposed from the hole 446.
[0067] When the holes 446 are formed in the thin plate members 44A2 to 44A4, similar to when the cutouts 443 are formed, the exposed portion 444 may be formed on the Z2 side surface of the large plate member farthest from the substrate 13, and the holes 442 that penetrate all of the large plate members may be formed in the exposed portion 444. With this configuration, the length in the stacking direction of the holes 442 formed in the exposed portion 444 is shorter than when the exposed portion 444 is formed in the thin plate member 44A4. Therefore, the holes 442 can be easily fitted into the fixing bosses 152, improving the strength of the current sensor 50.
[0068] The present invention is useful as a current sensor for measuring a current to be measured flowing through equipment, for example, to control a power supply system of a vehicle or the like equipped with various equipment.
[0069] 10: Current sensor 11: Bus bar 12: Magnetic sensor 13: Board 13a: Surface 13b: Opposing surface 131: Engagement portion 132: Hole 14A: Magnetic shield 14Aa: Opposing surface 14Ab: Surface 14B: Magnetic shield 141: Protrusion 142: Hole 15: Case 151: Storage recess 152: Fixing boss 153: Retaining portion 154: Screw hole 20: Current sensor 24A: Magnetic shield 24A1 to 24A4: Metal plate 24Aa: Opposing surface 24Ab: Surface 24B: Magnetic shield 241: Press-jointed portion 242: Hole 30: Current sensor 31: Fixing screw 32: Screw head 35: Current sensor 40: Current sensor 44A: Magnetic shield 44A1 to 44A4: Thin plate member 44Aa: Opposing surface 44Ab: Surface 442: Hole 443: Notch 444: Exposed portion 445: Step portion 446: Hole 447: Recessed portion 50: Current sensor 100: Current sensor 101: Bus bar 102: Magnetic sensor 103: Board 104A, 104B: Magnetic shield 105: Case 106: Cover 110: Current sensor 114A: Magnetic shield 114A1, 114A2: Metal plate 114Aa: Opposing surface 114Ab: Surface 1141: Hole L: Straight line
Claims
1. A current sensor comprising: a bus bar through which a current to be measured flows, a magnetic sensor disposed opposite the bus bar and detecting the magnetic field generated by the bus bar, a substrate on which the magnetic sensor is provided, a pair of flat-type first and second magnetic shields sandwiching the bus bar, the magnetic sensor, and the substrate, and a case in which the bus bar and the second magnetic shield are provided, the current sensor being stacked in the order of the first magnetic shield, the substrate, and the case, wherein: the first magnetic shield has a protrusion protruding from a first surface facing the substrate and a first reference portion for positioning, the substrate has an engagement portion engageable with the protrusion and a second reference portion for positioning, the case has a third reference portion for positioning, and when the protrusion and the engagement portion are engaged, the first reference portion, the second reference portion, and the third reference portion are aligned on a straight line parallel to the stacking direction of the first magnetic shield, the substrate, and the case.
2. The current sensor according to claim 1, wherein the first magnetic shield is formed by stacking a plurality of thin plate members, and the protrusion is a press joint formed by crimping the plurality of thin plate members in the stacking direction.
3. A current sensor as described in claim 2, wherein the first reference portion is provided on a first thin plate member adjacent to the substrate, among the plurality of thin plate members that the first magnetic shield has.
4. The current sensor according to claim 1, wherein a plurality of pairs of said protrusions and said engagement portions are provided.
5. A current sensor as described in claim 1, wherein the first reference portion is a shield hole penetrating the first magnetic shield, the second reference portion is a board hole penetrating the board, the third reference portion is a fixing boss having a retaining portion at a tip of the fixing boss, and the first magnetic shield and the board are fixed to the case by the retaining portion when the fixing boss is inserted into the shield hole and the board hole.
6. A current sensor as described in claim 5, wherein the first magnetic shield is formed by stacking a plurality of thin plate members, and the anti-slip portion is in contact with an exposed portion of a second surface of a thin plate member other than a second thin plate member that is farthest from the substrate in the stacking direction among the plurality of thin plate members, the second surface being opposite to a first surface that faces the substrate.
7. A current sensor as described in claim 6, wherein when any of the thin plate members arranged between the first thin plate member and the second thin plate member adjacent to the substrate is a third thin plate member, the first magnetic shield has a hole or cutout portion formed continuously from the second thin plate member to the third thin plate member along the stacking direction, and the second surface exposed from the hole or cutout portion is the exposed portion.
8. A current sensor as described in claim 1, comprising a fixing screw, the first reference portion being a shield hole penetrating the first magnetic shield, the second reference portion being a board hole penetrating the board, and the third reference portion being a screw hole capable of screwing into the fixing screw, and with the fixing screw inserted through the shield hole and the board hole, the first magnetic shield and the board are fixed to the case by the screw head of the fixing screw.
9. The current sensor described in claim 8, wherein the first magnetic shield is formed by stacking a plurality of thin plate members, and the screw head is in contact with an exposed portion of a second surface of a thin plate member other than a second thin plate member that is farthest from the substrate in the stacking direction among the plurality of thin plate members, the second surface being opposite to a first surface facing the substrate.
10. A current sensor as described in claim 9, wherein, when any of the thin plate members arranged between the first thin plate member and the second thin plate member adjacent to the substrate is a third thin plate member, the first magnetic shield has a hole or cutout portion formed continuously from the second thin plate member to the third thin plate member along the stacking direction, and the second surface exposed from the hole or cutout portion is the exposed portion.
11. A current sensor as described in claim 7 or 10, wherein the first magnetic shield is formed by stacking a plurality of the thin plate members, and among the plurality of the thin plate members of the first magnetic shield, a first thin plate member adjacent to the substrate has an exposed portion exposed on the second surface opposite to a first surface facing the substrate, and the exposed portion forms part of a step portion or a recessed portion.