Current sensor and method for manufacturing current sensor

Abstract

A current sensor 1 according to the present invention includes a soft magnetic body which is obtained by stacking a plurality of soft magnetic material plates, wherein a positional shift of the soft magnetic body occurring during insert molding is suppressed. This current sensor 1 has good measurement accuracy. This current sensor 1 includes: a housing 2; a core member 3 which is insert-molded in the housing 2 and is formed by stacking a plurality of soft magnetic material plates 30; and a magnetic sensor 4 for measuring magnetism. The core member 3 has a soft magnetic material plate 31 and a soft magnetic material plate 32 which has a different shape from the soft magnetic material plate 31. The soft magnetic material plate 32 includes an exposed part 32S that is exposed without being covered by the soft magnetic material plate 31 when viewed from the stacking direction of the soft magnetic material plates 30. In at least one surface of the core member 3, the outermost layer is composed of the soft magnetic material plate 31.

Description

Current sensor and method for manufacturing the same

[0001] The present invention relates to a current sensor that measures a current to be measured flowing through a bus bar, and a method for manufacturing the current sensor.

[0002] In recent years, current sensors that measure the current flowing through various devices have been used to control the power supply systems of vehicles and other devices. Patent Document 1 discloses a current sensor that has a hollow, annular magnetic core member with a gap in part and a shield plate, with the aim of achieving good detection accuracy and low manufacturing costs. The current sensor is designed to position the magnetic core member relative to the mold by fitting a protrusion on the mold into the hollow and gap in the core member, and then inject resin into the mold with the shield plate set in place to perform insert molding.

[0003] Patent Document 2 discloses a current sensor having a core member with a gap, which is intended for inexpensive and efficient manufacturing, and which is formed by alternately stacking two types of core members, first and second, each having a through hole for preventing the flow of magnetic flux into a member extending in the direction of the easy axis of magnetization.

[0004] Patent document 3 discloses a current sensor having a core member with a gap made by stacking multiple flat plates of magnetic material, with the aim of preventing the core member from becoming magnetically saturated even when the current becomes large, in which protrusions are provided on the flat plates at both ends in the stacking direction.

[0005] Patent Document 4 discloses a current sensor having a resin case and a core member made by laminating electromagnetic steel plates with gaps formed therein, with the aim of fixing the core member to the case with high positional accuracy using a simple structure.The current sensor discloses a configuration in which the core member is pressed into the case and is pressed from both sides by first convex portions formed on the inner wall of the case, thereby positioning and fixing the core member.

[0006] JP 2010-203910 A JP 2011-43422 A JP 2017-90126 A JP 2018-204978 A

[0007] When insert-molding a core member into a housing, the core member is held in a predetermined position within the molding die by a press pin provided on the molding die. Since there is variation in the external dimensions of the core member, it is necessary to be able to place even the largest core member within the tolerance range within the mold. Therefore, when the core member is placed, it is generally set so that there is a gap between the core member and the press pin.

[0008] In some cases, the core member is constructed from a plurality of stacked thin plate members. Each thin plate member has its own external dimension variation. Therefore, the dimensional variation of the core member in the stacking direction of the thin plate members is the cumulative result of the dimensional variation of the number of stacked thin plate members. If a core member is formed by stacking n thin plate members with a thickness variation of ±a [mm], the dimensional variation of the core member in the stacking direction is ±a × n [mm]. In other words, a difference of 2a × n [mm] will occur in the dimensions when a core member is formed only from the thinnest thin plate members and when a core member is formed only from the thickest thin plate members.

[0009] Therefore, when a core member is formed by stacking thin plate members, the greater the number of stacked layers, the greater the gap between the core member and the pressing pin in the stacking direction. The current sensors described in Patent Documents 1 to 4 do not take into consideration the dimensional variation of the core member in the stacking direction when using a core member formed by stacking multiple thin plate members. Therefore, if the gap between the pressing pin of the mold is large, the amount of positional deviation of the soft magnetic material that occurs during insert molding increases, which may lead to a decrease in the measurement accuracy of the current sensor.

[0010] Therefore, the present invention aims to provide a current sensor having a soft magnetic body formed by stacking multiple soft magnetic material plates, which has good measurement accuracy and in which the positional deviation of the soft magnetic body during insert molding is kept small, and a method for manufacturing the same.

[0011] As a means for solving the above-mentioned problems, the present invention has the following configuration: A current sensor including a housing, a soft magnetic body that is insert-molded into the housing and is formed by stacking a plurality of soft magnetic material plates, and a magnetic sensor that measures magnetism, wherein the soft magnetic body has a first soft magnetic material plate and a second soft magnetic material plate that has a shape different from that of the first soft magnetic material plate, the second soft magnetic material plate has an exposed portion that is not covered by the first soft magnetic material plate when viewed from the stacking direction of the soft magnetic material plates, and the soft magnetic body has an outermost layer on at least one surface that is the first soft magnetic material plate.

[0012] The current sensor may be configured such that the soft magnetic material is a core member and the magnetic sensor measures magnetic field collected by the core member.The current sensor may be configured such that the soft magnetic material is a magnetic shield.

[0013] With the above configuration, when positioning the soft magnetic material in a mold used to mold a housing, the mold's presser pins can be placed on exposed portions of the second soft magnetic material plates located near both ends of the soft magnetic material plates in the stacking direction. By using the first soft magnetic material plate as the outermost layer on at least one side, the number of laminations of soft magnetic material plates in the portion of the soft magnetic material sandwiched by the presser pins can be reduced compared to when the outermost soft magnetic material plates at both ends in the stacking direction are sandwiched by the presser pins. Therefore, the gap between the soft magnetic material and the presser pins, which is provided to accommodate variations in the thickness dimension of the soft magnetic material (size tolerance), can be reduced.

[0014] The soft magnetic body may include a non-exposed layer formed by stacking a plurality of the first soft magnetic material plates together, and an exposed layer formed by the second soft magnetic material plate, and the non-exposed layer may be stacked on at least one of the exposed layers. By adjusting the number of stacked soft magnetic material plates constituting the non-exposed layer and the exposed layer, a soft magnetic body suitable for the configuration of the current sensor can be obtained.

[0015] The non-exposed layer and the exposed layer may each be formed by laminating a plurality of soft magnetic material plates. By forming the non-exposed layer by laminating a plurality of soft magnetic material plates, the number of laminations of soft magnetic material plates constituting the exposed layer can be reduced compared to when the non-exposed layer is formed by a single soft magnetic material plate. By reducing the number of laminations of soft magnetic material plates constituting the exposed layer, the variation in thickness of the exposed layer, which increases in proportion to the number of laminations, can be reduced. Therefore, the gap between the soft magnetic body and the pressure pin, which is provided to accommodate the variation in thickness of the exposed layer, can be reduced, resulting in a current sensor with high measurement accuracy in which misalignment of the soft magnetic body is suppressed. Furthermore, by forming the exposed layer by laminating a plurality of soft magnetic material plates, the number of laminations of soft magnetic material plates constituting the non-exposed layer can be reduced compared to when the exposed layer is formed by a single soft magnetic material plate. Therefore, the length of the pressure pin that clamps the soft magnetic body can be shortened, corresponding to the number of laminations of the non-exposed layers, thereby reducing the risk of the pressure pin being damaged during insert molding.

[0016] A non-exposed layer may be provided on each side of the exposed layer sandwiched between the exposed portions in the lamination direction of the soft magnetic material plate. By providing a non-exposed layer on each side of the exposed layer, one of the two pressure pins sandwiching the exposed layer is less likely to be extremely long compared to the other pressure pin. Therefore, the risk of the pressure pins being damaged during insert molding can be reduced.

[0017] The non-exposed layers provided on both sides of the exposed layer in the lamination direction of the soft magnetic material plate may have the same number of laminations of the first soft magnetic material plate. By using the non-exposed layers provided on both sides of the exposed layer as first soft magnetic material plates with the same number of laminations, the soft magnetic material has a symmetrical shape with respect to the center in the lamination direction and does not have a front or back. Therefore, it is no longer necessary to consider the lamination direction orientation of the soft magnetic material when arranging it in a mold, improving productivity.

[0018] The exposed layer may be formed from one plate of the second soft magnetic material. By forming the exposed layer from one plate of the second soft magnetic material, the portion of the soft magnetic body that is sandwiched by the pressing pins becomes a single layer, thereby minimizing the variation in the thickness dimension of the soft magnetic body. Therefore, the gap between the soft magnetic body and the pressing pins, which is provided to accommodate the variation, can be reduced.

[0019] The magnetic sensor may be disposed inside or near the notch, and the soft magnetic material may be a core member, the core member being formed in an annular shape with a notch, the housing having an insertion hole penetrating the inside of the ring formed by the core member, and the magnetic sensor may be disposed inside or near the notch. With the above configuration, the magnetic field resulting from the current to be measured that is collected in the core member can be detected by the magnetic sensor.

[0020] The magnetic sensor may be an MR sensor capable of detecting a magnetic field parallel to a magnetic detection surface, and may be disposed outside the notch so that the magnetic detection surface is parallel to the separation direction of the notch. By disposing the MR sensor outside the notch, the MR sensor can be disposed at a position where a magnetic field corresponding to the measurement sensitivity is generated based on the magnitude of the generated magnetic field. This improves the measurement accuracy of the current sensor.

[0021] The housing may have a recess on a surface of the housing that intersects with the lamination direction of the soft magnetic material plates, and the exposed portion may be exposed at the innermost portion of the recess. By exposing the exposed portion of the soft magnetic material from the innermost portion of the recess recessed from the surface of the housing, the risk of corrosion of the soft magnetic material plate is reduced compared to when the exposed portion is exposed from the surface of the housing.

[0022] The housing may include a covering portion disposed inside the recess and covering the exposed portion exposed in the recess. The covering portion covering the exposed portion can more reliably prevent liquid from seeping into the housing through a gap between the resin forming the housing and the soft magnetic material plate.

[0023] The method for manufacturing a current sensor is a method for insert-molding a soft magnetic body formed by stacking a plurality of soft magnetic material plates into a housing, wherein the soft magnetic body has a first soft magnetic material plate provided as the outermost layer on at least one side, and a second soft magnetic material plate that has a shape different from the first soft magnetic material plate and has an exposed portion that is not covered by the first soft magnetic material plate, and when a pair of pressure pins of a molding die clamp the soft magnetic body, at least one of the pair of pressure pins is brought into contact with the exposed portion, and while at least one of the pair of pressure pins is in contact with the exposed portion, molten molding resin is filled into the molding die.

[0024] By bringing at least one of the pair of pressing pins into contact with the exposed portion, it is possible to clamp a portion having a smaller number of layers than the number of layers of the soft magnetic material plates that form the soft magnetic material plate, thereby making it possible to reduce the gap between the soft magnetic material and the pressing pin, which is provided to accommodate variations in the thickness dimension of the soft magnetic material.

[0025] The present invention makes it possible to reduce the gap between the pressing pin of the mold used in insert molding and the soft magnetic material plate. By reducing this gap, it is possible to reduce the positional deviation of the soft magnetic material that may occur during insert molding, thereby providing a current sensor with good measurement accuracy in which the decrease in measurement accuracy due to positional deviation is suppressed.

[0026] 1 is a perspective view showing the appearance of a current sensor according to a first embodiment of the present invention. FIG. 1 is an exploded perspective view schematically showing the configuration of the current sensor of FIG. 1. FIG. 2 is a perspective view showing an example of the configuration of a conventional core member. FIG. 3 is a plan view schematically showing the relationship between the core member and the presser pins of a mold in region P of FIG. 3. FIG. 4 is a perspective view showing the configuration of the core member of the current sensor of FIG. 1. FIG. 5 is a partial cross-sectional view schematically showing the relationship between the core member and the presser pins of a mold in region P of FIG. 5. FIG. 6 is a partial cross-sectional view schematically showing the relationship between the core member, the housing, and the presser pins of the mold taken along line A-A of FIG. 1. FIG. 7 is a partial cross-sectional view schematically showing a modified example of the relationship between the core member and the housing taken along line A-A of FIG. 1. FIG. 8 is a partial cross-sectional view schematically showing a modified example of the relationship between the core member and the housing of FIG. 8. FIG. 10 is a side view schematically showing the configuration of a modified example of the core member of FIG. 10. FIG. 11 is a side view schematically showing the configuration of a modified example of the core member of FIG. 10. FIG. 12 is a side view schematically showing the configuration of a modified example of the core member of FIG. 10. 16 is a flowchart illustrating a manufacturing method of an embodiment of the present invention. It is a perspective view showing the appearance of a current sensor according to a second embodiment of the present invention. It is a cross-sectional view schematically showing the configuration of the current sensor taken along line AA in FIG.

[0027] [First Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. The same components in each drawing will be assigned the same numbers, and descriptions thereof will be omitted where appropriate. Reference coordinates will be 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, the extension direction of the bus bar perpendicular to the X direction is defined as the Y 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. 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.

[0028] Fig. 1 is a perspective view showing the appearance of a current sensor 1 according to this embodiment. Fig. 2 is an exploded perspective view schematically showing the configuration of the current sensor 1 of Fig. 1. Note that the core member 3 is insert-molded into the housing 2, and the core member 3 and the housing 2 are formed integrally, but for ease of explanation, the exploded perspective view of Fig. 2 shows the core member 3 removed from the housing 2.

[0029] The current sensor 1 includes a housing 2, a core member 3 (soft magnetic material), and a magnetic sensor 4. The housing 2 is formed from a material such as resin, and the core member 3 is insert-molded into the housing 2. The housing 2 has an insertion hole 21 that penetrates the inside of a ring formed by the core member 3, and the bus bar 6 is inserted into the insertion hole 21.

[0030] The core member 3 is made of a soft magnetic material and is formed by stacking multiple soft magnetic material plates 30. The soft magnetic material plates 30 are fixed to one another by laser welding, crimping, or the like. The core member 3 has a notch 3G sandwiched between two end faces 3E facing each other in the X direction, and is formed into an annular shape through which the bus bar 6 can be inserted when viewed along the stacking direction. A recess 22 is formed on a surface 2S of the housing 2 that intersects with the stacking direction of the core member 3, in a portion where a pressing pin was located during insert molding.

[0031] When a current to be measured flows through the bus bar 6, a magnetic field is formed along the core member 3. That is, a magnetic field that is not easily affected by external disturbances is generated between the end faces 3E of the core member 3, and the magnetic field between the end faces 3E is detected by the magnetic sensor 4. Note that, although the following describes an embodiment in which the bus bar 6 is inserted through the core member 3, the present invention can also be implemented in an embodiment in which a conductor other than the bus bar 6 is inserted through the core member 3. In this case, the current sensor 1 measures the current to be measured flowing through the conductor.

[0032] The magnetic sensor 4 is an MR sensor (magnetoresistive sensor) capable of detecting a magnetic field in a predetermined direction parallel to the magnetic detection surface 41 and can be planar-mounted on the substrate 5. The direction in which the magnetic sensor 4 can detect a magnetic field is referred to as the sensitivity axis direction. In this embodiment, the magnetic detection surface 41 is disposed outside (on the Y1 side) of the notch 3G in the core member 3 so that it is parallel to the X direction along which the two end faces 3E face each other, and the sensitivity axis direction is also parallel to the X direction. By disposing the magnetic sensor 4 outside the notch 3G, the magnetic sensor 4 can be positioned at a location where a magnetic field corresponding to the measurement sensitivity is generated based on the magnitude of the generated magnetic field, thereby improving the measurement accuracy of the current sensor 1. However, the magnetic sensor 4 may also be disposed inside or near (on the Y2 side or Z1 side, etc.) the notch 3G of the core member 3.

[0033] Examples of the magnetic detection element included in the magnetic sensor 4 include magnetoresistive elements such as GMR elements and TMR elements. Note that the magnetic sensor 4 may include a Hall element or the like instead of a magnetoresistive element for magnetic detection.

[0034] The sensitivity axis of the magnetic detection surface 41 of the magnetic sensor 4 is oriented in a direction parallel to the X-axis facing the end surface 3E of the core member 3. The induced magnetic field generated near the magnetic detection surface 41 of the magnetic sensor 4 when a current to be measured flows through the bus bar 6 and collected by the core member 3 contains a large component in the X-axis. Therefore, by positioning the magnetic sensor 4 so that the sensitivity axis is parallel to the X-axis, the magnetism emitted by the bus bar 6 can be detected with high accuracy.

[0035] The bus bar 6 is a conductive material made of copper, brass, aluminum, or the like, through which the current to be measured flows. The bus bar 6 is formed in a plate shape and is arranged so as to penetrate the core member 3, which is formed in an annular shape. Note that, although the bus bar 6 in the current sensor 1 is plate-shaped, it is not limited to a plate shape. For example, the cross section of the bus bar 6 when cut in the X-Z plane may be circular.

[0036] The soft magnetic material plates 30 constituting the core member 3 are made up of two types of plate-shaped bodies: a soft magnetic material plate 31 (first soft magnetic material plate) and a soft magnetic material plate 32 (second soft magnetic material plate). The soft magnetic material plate 32 has a different shape from the soft magnetic material plate 31. The soft magnetic material plate 32 has an exposed portion 32S that is not covered by the soft magnetic material plate 31 when viewed along the Y direction, which is the lamination direction of the soft magnetic material plate 30. In the core member 3 shown in FIG. 2 , the soft magnetic material plate 30 constituting the outermost layer is the soft magnetic material plate 31 on both the Y1 side and the Y2 side. However, as will be described later as a modified example, it is sufficient that the outermost layer on at least one of the Y1 side and the Y2 side is the soft magnetic material plate 31.

[0037] The magnetic flux collection characteristics of the core member 3 are improved by laminating thin soft magnetic material plates 30. The thickness and number of laminations of the soft magnetic material plates 30 may be designed in relation to the performance required of the core member 3.

[0038] FIG. 3 is a perspective view showing an example of the configuration of a conventional core member 103. FIG. 4 is a plan view schematically showing the relationship between the core member 103 and the press pins of the mold in region P of FIG. 3 . Referring to these figures, the inventors will now describe the issues they discovered when insert-molding a core member 103 formed by stacking multiple soft magnetic material plates 130 into a housing 2. The following explanation uses the terms "design reference dimension" and "size tolerance," so we will provide additional information on these terms. For example, if the dimension s (mm) of a certain portion is controlled as s = p (mm) ± q (mm), then p (mm) is the design reference dimension and ±q (mm) is the size tolerance. The size tolerance may have different positive and negative values, such as +0.05 (mm) / −0.02 (mm).

[0039] When the core member 103 is fixed at a predetermined position within a mold and insert-molded into the housing 2 (see FIGS. 1 and 2 ), the core member 103 is clamped by the presser pins 71 of the mold to position the core member 103 in the Y direction, which is the stacking direction. At this time, the distance between the presser pins 71 is set slightly larger than the predetermined thickness dimension to account for variations in the thickness dimension of the core member 103. In other words, even if the thickness dimension of the core member 103 is larger than the design standard dimension within the size tolerance range, it is necessary to place the core member 103 within the mold and perform insert molding. Therefore, the mold is designed so that when the core member 103 processed to the design standard thickness dimension is placed within the mold, a gap (clearance) C is formed between the presser pins 71 and the core member 103. In other words, a gap C is provided between the presser pins 71 and the core member 103 to accommodate variations in the thickness dimension of the core member 103. In other words, even if the thickness dimension of the core member 103 is the largest dimension within the range of the size tolerance, the gap C is provided so that the core member 103 can be placed in the mold. This makes it possible to prevent problems related to the mold from occurring when positioning the core member 103, even if the thickness dimension of the core member 103 increases due to variations.

[0040] In the case of a core member 103 formed by stacking multiple soft magnetic material plates 130, the range of variation in thickness is likely to be larger than in a core member formed in the shape of a single block. For example, if the thickness dimension T of the soft magnetic material plates 130 is controlled by the design standard dimension D and a size tolerance of ±A, and the core member 103 is formed by stacking N soft magnetic material plates 130, the thickness dimension T' of the core member 103 must be controlled by T' = (N × D) ± (N × A). In other words, compared to the design standard dimension N × D, there is a possibility of variation within a range of up to ± (N × A). Therefore, taking into account the case where the thickness dimension of the core member 103 is the largest dimension (N × (D + A)) within the range of the size tolerance, the above-mentioned gap C must be set to N × A.

[0041] Assuming that the thickness dimension, i.e., thickness dimension T, of the soft magnetic material plates 130-1 to 130-N forming the core member 103 were all thinner than the design reference dimension D by A, the thickness dimension T' of the core member 103 would be N×A smaller than the design reference dimension N×D. In this case, a gap of 2N×A would be created between the mold retainer pin 71 and the core member 103, which is the sum of the N×A variation and the N×A gap C. As a result, there is a risk that the core member 103 will be pushed by the resin injected into the mold during insert molding, causing the position of the core member 103 to shift (2N×A) in the Y direction. For example, in a core member 103 formed by stacking 12 soft magnetic material plates 130, if the design reference dimension D for the thickness of the soft magnetic material plates 130 is 0.5 mm and the thickness dimensions of the soft magnetic material plates 130, which are managed with a size tolerance of ±0.04 mm, are all machined to 0.5-0.04 mm, there is a risk that the position of the core member 103 will shift by up to 0.96 mm in the Y direction.

[0042] If the position of the core member 103 in the housing 2 is shifted during insert molding, a shift in the positional relationship between the core member 103 and the magnetic sensor 4 occurs, which reduces the measurement accuracy of the current sensor 1.

[0043] Therefore, the core member 3 of the current sensor 1 of this embodiment has a structure for reducing the gap C between the core member 3 and the press pin 71 of the mold to accommodate the variations, and for reducing the variations in the thickness dimension of the portion sandwiched by the press pin 71. By reducing the gap C and the variations in the thickness dimension, the amount of positional deviation of the core member 3 that may occur during insert molding can be reduced, and the current sensor 1 can be made to have good measurement accuracy, with the core member 103 and magnetic sensor 4 arranged in predetermined positions.

[0044] Fig. 5 is a perspective view showing the configuration of the core member 3 of the current sensor 1 of Fig. 1. Fig. 6 is a partial cross-sectional view schematically showing the relationship between the core member 3 and the pressing pin 71 of the mold in region P of Fig. 5. This figure is a partial cross-sectional view in which a part of the exposed portion 32S of the soft magnetic material plate 32 is cut by the rectangular surface shown as region P, and the part of the soft magnetic material plate 32 that protrudes from the side that forms the outer frame on the Z2 side is shown with oblique lines. Fig. 7 is a partial cross-sectional view schematically showing the relationship between the core member 3, the housing 2, and the pressing pin 71 of the mold 7 along line A-A of Fig. 1.

[0045] As shown in these figures, the core member 3 of the current sensor 1 includes two types of soft magnetic material plates 30: a soft magnetic material plate 31 and a soft magnetic material plate 32. The soft magnetic material plate 32 includes an exposed portion 32S that is exposed when the core member 3 is viewed along the stacking direction (Y direction). In other words, when the soft magnetic material plates 31 and 32 are stacked adjacent to each other and viewed from the soft magnetic material plate 31 side, the exposed portion 32S is the portion not covered by the soft magnetic material plate 31 (protruding from the soft magnetic material plate 31). In the core member 3, the exposed portion 32S of the soft magnetic material plate 32 is configured as a circular surface, with a portion exposed through a recessed portion of the outline of the soft magnetic material plate 31 and a protruding portion. However, the outer shape of the exposed portion 32S is not limited to a circular shape, and it may be configured as only one of the portion exposed through the recessed portion or the portion protruding toward the Z2 side.

[0046] Furthermore, when the core member 3 of the current sensor 1 is laminated with the soft magnetic material plates 31 and 32, at least one end of the core member 3 in the lamination direction is formed of the soft magnetic material plate 31. When the core member 3 is placed in the mold 7, a press pin 71 is placed against the exposed portion 32S to hold it in place. With this configuration, at least the soft magnetic material plate 31 located at one end of the core member 3 in the lamination direction is not clamped by the press pin 71. Therefore, when providing a gap C between the core member 3 and the press pin 71, it is not necessary to consider variations in the thickness of the soft magnetic material plate 31 located at one end of the core member 3 in the lamination direction. This allows the size of the gap C to be reduced, and the negative dimensional variation of the portion clamped by the press pin 71 is also reduced. Therefore, the amount of positional misalignment of the core member 3 during insert molding can be reduced compared to when the core member 3 is formed with a single type of soft magnetic material plate 30. In addition, by increasing the number of layers of the soft magnetic material plate 31 arranged at one end or by arranging soft magnetic material plates 31 at both ends, the amount of positional deviation of the core member 3 during insert molding can be further reduced.

[0047] That is, even if the thickness dimension T of all of the soft magnetic material plates 30-1 to 30-N is made thinner by A than the design reference dimension D, it is the soft magnetic material plates 32-1 to 32-n that are clamped by the pressing pins 71 of the mold 7, as shown in Figures 5 and 6. For this reason, the gap C that is set in consideration of the maximum variation is n x A (n < N), where n is the number of layers of the soft magnetic material plates 32.

[0048] Here, if the thickness dimension T of all of the soft magnetic material plates 30-1 to 30-N is made thinner by A than the design standard dimension D, the thickness dimension T' of the core member 3 will be smaller by N×A than the design standard dimension N×D. In other words, when the core members 3 are sandwiched between the presser pins 71 of the mold 7 in the soft magnetic material plates 30 arranged at one end and the other end of the stacked soft magnetic material plates 30, the gap between the core members 3 and the presser pins 71 will be N×A wider than when the thickness dimension T of all of the soft magnetic material plates 30 is made to the design standard dimension D (see FIG. 4).

[0049] In contrast to this, when the exposed portion 32S of the core member 3 is configured to be sandwiched between the press pins 71 of the mold 7, the thickness dimension t' of the laminated layers of the soft magnetic material plates 32 located between the press pins 71 of the mold 7 is smaller by n×A than the design standard dimension n×D. In other words, when the exposed portion 32S of the core member 3 is configured to be sandwiched between the press pins 71 of the mold 7, the gap between the core member 3 and the press pins 71 is wider by n×A compared to when the thickness dimension T of the soft magnetic material plates 30 is entirely the design standard dimension D.

[0050] Since n<N, by configuring the exposed portion 32S of the core member 3 to be clamped by the pressing pin 71 of the mold 7, the amount of widening of the gap between the core member 3 and the pressing pin 71 can be reduced even if the thickness dimension T of the soft magnetic material plate 30 is all minimum within the size tolerance.

[0051] The configuration of this embodiment reduces the size of the gap C set between the press pin 71 and the core member 3, taking into account variations in the thickness dimension of the soft magnetic material plate 30, and also reduces the size of the gap C when the thickness dimension T of all the soft magnetic material plates 30 is at its minimum within the size tolerance. Therefore, it is possible to reduce the maximum amount of displacement of the position of the core member 103 in the Y direction, which may occur due to resin flow during insert molding.

[0052] For example, consider a core member 3 composed of 12 laminated soft magnetic material plates 30, each with a thickness T of 0.5 mm and a variation of 0.04 mm, with four of the 12 plates being continuously laminated soft magnetic material plates 32. In this case, the thickness t' of the portion sandwiched between the retaining pins 71 is a maximum of 0.16 mm (4 × 0.04 mm) smaller than the predetermined thickness of 2.0 mm (4 × 0.5 mm), resulting in a gap C of 0.16 mm (4 × 0.04 mm). Therefore, the maximum possible misalignment of the core member 3 during insert molding into the housing 2 is 0.32 mm. In this way, the possible misalignment of the core member 3 in the Y direction can be reduced to one-third of the 0.96 mm of the core member 103 shown in FIG. 4 .

[0053] As described above, in the current sensor 1, the core member 3 is composed of the soft magnetic material plate 31 having a notch and the soft magnetic material plate 32 having no notch. This allows the presser pins 71 to sandwich only a portion of the soft magnetic material plate 32 (exposed portion 32S) rather than sandwiching all of the soft magnetic material plates 30 (soft magnetic material plates 31 and 32) that make up the core member 3, thereby reducing the number of soft magnetic material plates 30 sandwiched between the presser pins 71. This makes it possible to reduce variations in thickness of the portion sandwiched between the presser pins 71 when determining the position of the core member 3 in the stacking direction during insert molding.

[0054] That is, in the mold 7 used for insert molding, the core member 3 can be held by clamping a portion of the soft magnetic material plate 30 with a smaller number of layers than the total number of layers. This reduces the gap C between the core member 3 and the pressing pins 71 of the mold 7 and the variation in thickness in the portion where the soft magnetic material plate 32 is laminated. Therefore, it is possible to reduce the positional deviation that may occur in the core member 3 during insert molding into the housing 2, resulting in a current sensor 1 with excellent measurement accuracy.

[0055] 8 is a partial cross-sectional view schematically illustrating the relationship between the core member 3 and the housing 2 taken along line A-A in FIG. 1. As shown in the figure, when the core member 3 is insert-molded and the mold 7 is removed, the portion where the retaining pin 71 of the mold 7 was located becomes the recess 22. That is, the recess 22 is formed on the surface 2S of the housing 2 that intersects with the Y direction, which is the stacking direction of the core member 3, and the exposed portion 32S is exposed from the innermost portion of the recess 22. In the current sensor 1, the exposed portion 32S, which is the plated surface of the core member 3, is exposed at the innermost portion of the recess 22, so that corrosion of the core member 3 can be suppressed.

[0056] FIG. 9 is a partial cross-sectional view schematically illustrating the relationship between the core member 3 and the housing 2 in the current sensor 1 according to the modification of FIG. 8 . As shown in the figure, the housing 2 may include a covering portion 23 that covers the exposed portion 32S that is exposed from the innermost portion of the recess 22. The covering portion 23 covering the recess 22 can prevent liquid from seeping into the housing 2 through a gap between the resin forming the housing 2 and the core member 3. Note that any material can be used for the covering portion 23 as long as it can cover the recess 22; for example, a resin different from the resin used for insert molding can be used. In this modification, the covering portion 23 is formed by filling the recess 22 with resin, but the covering portion 23 may also be formed by press-fitting or attaching a separate member.

[0057] Fig. 10 is a side view schematically showing the configuration of the core member 3 in the current sensor 1 of Fig. 1. The figure shows the core member 3 having a configuration in which four layers of soft magnetic material plates 31, four layers of soft magnetic material plates 32, and four layers of soft magnetic material plates 31 are stacked in this order from the Y1 side to the Y2 side.

[0058] The core member 3 includes a non-exposed layer 10 formed by stacking a plurality of soft magnetic material plates 31 together, and an exposed layer 20 formed by stacking soft magnetic material plates 32 together and having exposed portions 32S at both ends in the Y direction, with the non-exposed layer 10 stacked on both sides of the exposed layer 20. The non-exposed layer 10 and the exposed layer 20 each include a plurality of soft magnetic material plates 30 stacked together.

[0059] As shown in Figure 10, the core member 3 has a configuration in which non-exposed layers 10 made of soft magnetic material plates 31 are provided on both sides of an exposed layer 20 made of several layers of soft magnetic material plates 30 (soft magnetic material plates 32), making it possible to make the core member 3 less susceptible to damage by the pressing pins 71.

[0060] For example, when a core member 3 having a non-exposed layer 10 only on one side (Y1 side) of the exposed layer 20 is placed in the mold 7 shown in FIG. 7 , the pressing pin 71 on the Y1 side will be longer than the pressing pin 71 on the Y2 side. Because the pressing pin 71 is a very thin metal rod, the longer it is, the more likely it is to break when a force is applied to the tip in the X or Z direction. In other words, with this configuration, the exposed layer 20 is located near the center in the stacking direction, and one pressing pin 71 (see FIGS. 6 and 7 ) is not extremely long, making the pressing pin 71 less likely to break. Furthermore, the number of laminations of the soft magnetic material plates 31 that make up the non-exposed layer 10 can be adjusted to adapt the core member 3 to the configuration of the current sensor 1.

[0061] 10, if the core member 3 is configured such that non-exposed layers 10 with the same number of layers are provided on both sides of the exposed layer 20, there is no need to consider the orientation (front and back) when placing the core member 3 in the mold 7 (see FIG. 7). This improves workability and productivity, and makes it possible to reduce production costs.

[0062] (Modification) Figure 11 is a side view schematically showing the configuration of a modification of the core member 3 of Figure 10. The figure shows a core member 3 configured such that, from the Y1 side to the Y2 side, a non-exposed layer 10 made up of two soft magnetic material plates 31, an exposed layer 20 made up of four soft magnetic material plates 32, and a non-exposed layer 10 made up of six soft magnetic material plates 31 are laminated in this order. In this way, a configuration may be adopted in which the number of laminations of soft magnetic material plates 31 constituting the non-exposed layers 10 provided on both sides of the exposed layer 20 is different.

[0063] Figure 12 is a side view schematically showing the configuration of a modified example of the core member 3 of Figure 10. The figure shows a core member 3 configured such that, from the Y1 side to the Y2 side, a non-exposed layer 10 made up of four soft magnetic material plates 31, an exposed layer 20 made up of one soft magnetic material plate 32, and a non-exposed layer 10 made up of seven soft magnetic material plates 31 are laminated in this order. In this way, the exposed layer 20 may be formed from a single soft magnetic material plate 32. This allows for insert molding that only requires consideration of the variation of one metal plate in the soft magnetic material plate 32, eliminating the need to consider stacking tolerances, thereby reducing positional deviation of the core member 3.

[0064] Fig. 13 is a side view schematically showing the configuration of a modified example of the core member 3 of Fig. 10. The figure shows a core member 3 having a configuration in which, from the Y1 side to the Y2 side, an exposed layer 20 made of three soft magnetic material plates 32 and a non-exposed layer 10 made of nine soft magnetic material plates 31 are laminated in this order. In this way, a configuration in which the non-exposed layer 10 is provided only on one side of the exposed layer 20 may be used.

[0065] 13 , by providing the exposed layer 20 on the Y1 side closer to the magnetic sensor 4, it becomes easy to provide the magnetic sensor 4 and the core member 3 at predetermined positions. Therefore, from the viewpoint of manufacturing a current sensor 1 with good measurement accuracy, a configuration in which the non-exposed layer 10 is provided only on the opposite side of the magnetic sensor 4 (see FIGS. 2 and 5 ) with respect to the exposed layer 20 is preferable.

[0066] Figure 14 is a side view schematically illustrating the configuration of a modified example of the core member 3 of Figure 10. The figure shows a core member 3 configured such that, from the Y1 side to the Y2 side, a non-exposed layer 10 made of four soft magnetic material plates 31, an exposed layer 20 in which two soft magnetic material plates 31 are sandwiched between soft magnetic material plates 32, and a non-exposed layer 10 made of four soft magnetic material plates 31 are laminated in this order. In this way, the exposed layer 20 may be configured such that a soft magnetic material plate 32 is disposed between the soft magnetic material plates 32 at both ends in the lamination direction. This configuration increases the surface area of ​​the exposed layer 20 and the contact area with the resin, thereby improving adhesion between the resin injected during insert molding and the core member 3.

[0067] 15 is a flowchart showing a manufacturing method of this embodiment. As shown in the figure, the manufacturing method of this embodiment is a method for manufacturing a current sensor 1 in which a core member 3 (soft magnetic body) formed by stacking a plurality of soft magnetic material plates 30 is insert-molded into a housing 2. The core member 3 used in this manufacturing method has a soft magnetic material plate 31 provided as an outermost layer on at least one surface, and a soft magnetic material plate 32 that has a different shape from the soft magnetic material plate 31 and has an exposed portion 32S that is not covered by the soft magnetic material plate 31 and is exposed.

[0068] In insert molding, a component to be embedded in resin is positioned in a predetermined position in a mold using a press pin or the like, and then the mold is filled with resin. In the manufacturing method of this embodiment, first, when a pair of press pins 71 of a mold 7 (molding mold) clamps the core member 3, at least one of the pair of press pins 71 is brought into contact with the exposed portion 32S (S10). Next, with at least one of the pair of press pins 71 in contact with the exposed portion 32S, the mold 7 is filled with molten molding resin (S20, see FIGS. 5 to 7).

[0069] By bringing at least one of the pair of press pins 71 into contact with the exposed portion 32S, the number of layers of the soft magnetic material plate 30 to be sandwiched can be reduced compared to the number of layers when both ends of the soft magnetic material plate 30 forming the core member 3 are sandwiched. Therefore, the gap C between the core member 3 and the press pins 71 of the mold 7, which is provided to accommodate variations in the thickness dimension of the core member 3, can be reduced. Furthermore, because the number of layers of the soft magnetic material plate 30 sandwiched by the press pins 71 is reduced, the dimensional variation of the sandwiched portion is reduced. Therefore, the amount of positional deviation of the core member 3 that occurs during insert molding is reduced, and a current sensor 1 with high measurement accuracy can be manufactured.

[0070] Second Embodiment Fig. 16 is a perspective view showing the appearance of a current sensor 9 according to this embodiment. Fig. 17 is a cross-sectional view schematically showing the configuration of the current sensor 9 taken along line AA in Fig. 16 .

[0071] Current sensor 9 differs from current sensor 1 in that it does not include a core member 3, but includes magnetic shields 93A and 93B as soft magnetic materials. Current sensor 9 also differs from current sensor 1 in that it includes a housing 2 that is made up of a main body 2A that is provided with a bus bar 6 and has a magnetic shield 93A insert-molded therein, and a cover 2B that is insert-molded.

[0072] The magnetic sensor 4 detects the magnetism emitted by the bus bar 6 when a current to be measured flows. The magnetic sensor 4 is provided on the substrate 5 so as to face the bus bar 6 in the Z direction. The magnetic detection surface 41 of the magnetic sensor 4 is the surface directly facing the bus bar 6, and the sensitivity axis is oriented in a direction parallel to the magnetic detection surface 41. The magnetic field generated near the magnetic detection surface 41 of the magnetic sensor 4 when a current to be measured flows through the bus bar 6 contains many components in the X-axis direction near the magnetic sensor 4. Therefore, by arranging the magnetic sensor 4 so that the sensitivity axis is parallel to the X direction, the magnetism emitted by the bus bar 6 can be detected with high accuracy.

[0073] The magnetic shields 93A and 93B are arranged in the Z direction to sandwich the magnetic sensor 4 and the bus bar 6, and are made of soft magnetic materials such as metal plates. The magnetic shields 93A and 93B can suppress magnetic noise to the magnetic sensor 4, improving the measurement accuracy of the current sensor 9. Note that the current sensor 9 may include only one of the magnetic shields 93A and 93B.

[0074] The magnetic shields 93A, 93B include a soft magnetic material plate 931 (first soft magnetic material plate) and a soft magnetic material plate 932 (second soft magnetic material plate). The soft magnetic material plate 932 has a different shape from the soft magnetic material plate 931, and includes an exposed portion 932S that is not covered by the soft magnetic material plate 931 when viewed along the Z direction, which is the stacking direction of the soft magnetic material plate 930. The outermost soft magnetic material plate 930 constituting the magnetic shields 93A, 93B is composed of the soft magnetic material plate 931 on both the Z1 side and the Z2 side. However, as described as a modified example in the first embodiment, it is sufficient that the outermost layer on either the Z1 side or the Z2 side is the soft magnetic material plate 931.

[0075] The characteristics of the magnetic shields 93A and 93B are improved by laminating thin soft magnetic material plates 930. The number of laminations and the thickness of the soft magnetic material plates 930 may be appropriately designed in relation to the required performance.

[0076] Like the core member 3, the magnetic shields 93A, 93B are positioned by the press pins 71 of the mold 7 when they are insert-molded into the main body 2A and the cover 2B of the housing 2. At this time, by clamping the exposed portion 932S of the soft magnetic material plate 932 with the press pins 71, rather than the soft magnetic material plate 931 of the outermost layer in the stacking direction of the magnetic shields 93A, 93B, it is possible to suppress misalignment during insert molding, as with the core member 3. Therefore, it is possible to provide a current sensor 9 in which deterioration of measurement accuracy due to misalignment of the magnetic shields 93A, 93B is suppressed.

[0077] 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-described embodiments alone, and is intended to include all modifications within the meaning and scope of the claims.

[0078] The present invention is useful, for example, as a current sensor for measuring a current to be measured flowing through equipment in order to control the power supply system of a vehicle or the like equipped with various devices, and as a method for manufacturing the same.

[0079] DESCRIPTION OF SYMBOLS 1: Current sensor 2: Housing 2A: Main body 2B: Cover 2S: Surface 21: Insertion hole 22: Recess 23: Covering portion 3: Core member 3E: End face 3G: Notch 30: Soft magnetic material plate 30-1 to 30-N: Soft magnetic material plate 31: Soft magnetic material plate (first soft magnetic material plate) 32: Soft magnetic material plate (second soft magnetic material plate) 32-1 to 32-n: Soft magnetic material plate (second soft magnetic material plate) 32S: Exposed portion 4: Magnetic sensor 41: Magnetic detection surface 5: Substrate 6: Bus bar 7: Mold 71: Presser pin 9: Current sensor 93A: Magnetic shield 93B: Magnetic shield 930: Soft magnetic material plate 931 : Soft magnetic material plate (first soft magnetic material plate) 932 : Soft magnetic material plate (second soft magnetic material plate) 932S : Exposed portion 10 : Non-exposed layer 20 : Exposed layer 103 : Core member 130 : Soft magnetic material plate 130-1 to 130-N: Soft magnetic material plate C : Gap D : Design reference dimension T, T', t': Thickness dimension ±A : Size tolerance N : Number of sheets P : Area

Claims

1. A current sensor comprising a housing, a soft magnetic body formed by stacking a plurality of soft magnetic material plates and insert-molded into the housing, and a magnetic sensor for measuring magnetism, wherein the soft magnetic body has a first soft magnetic material plate and a second soft magnetic material plate having a shape different from that of the first soft magnetic material plate, the second soft magnetic material plate having an exposed portion that is not covered by the first soft magnetic material plate when viewed from the stacking direction of the soft magnetic material plates, and the soft magnetic body has an outermost layer on at least one surface that is the first soft magnetic material plate.

2. The current sensor according to claim 1, wherein the soft magnetic material is a core member, and the magnetic sensor measures magnetic field collected by the core member.

3. The current sensor according to claim 1, wherein the soft magnetic material is a magnetic shield.

4. A current sensor as described in claim 1, wherein the soft magnetic body comprises a non-exposed layer formed by stacking a plurality of the first soft magnetic material plates together, and an exposed layer formed by the second soft magnetic material plate, and the non-exposed layer is stacked on at least one of the exposed layers.

5. The current sensor according to claim 4, wherein the unexposed layer and the exposed layer are each formed by stacking a plurality of the soft magnetic material plates.

6. The current sensor according to claim 1, wherein a non-exposed layer is provided on each side of the exposed layer sandwiched between the exposed portions in the lamination direction of the soft magnetic material plate.

7. The current sensor according to claim 6, wherein the non-exposed layers provided on both sides of the exposed layer in the lamination direction of the soft magnetic material plates have the same number of laminations of the first soft magnetic material plates.

8. The current sensor according to claim 4, wherein said exposed layer is constituted by one of said second soft magnetic material plates.

9. A current sensor as described in claim 1, wherein the soft magnetic material is a core member, the core member is formed in an annular shape with a cutout portion, the housing has an insertion hole penetrating the inside of the ring formed by the core member, and the magnetic sensor is disposed inside or around the cutout portion.

10. A current sensor as described in claim 9, wherein the magnetic sensor is an MR sensor capable of detecting a magnetic field in a direction parallel to a magnetic detection surface, and the magnetic detection surface is arranged outside the cutout so as to be parallel to the separation direction of the cutout.

11. The current sensor according to claim 1, wherein the housing has a recess on a surface thereof intersecting with a lamination direction of the soft magnetic material plates, and the exposed portion is exposed at the innermost part of the recess.

12. The current sensor according to claim 11, wherein the housing is provided with a covering portion disposed inside the recess and covering the exposed portion exposed in the recess.

13. A method for manufacturing a current sensor in which a soft magnetic body formed by stacking a plurality of soft magnetic material plates is insert-molded into a housing, the soft magnetic body having a first soft magnetic material plate provided as an outermost layer on at least one surface, and a second soft magnetic material plate having a shape different from that of the first soft magnetic material plate and having an exposed portion that is not covered by the first soft magnetic material plate, the method being characterized in that when a pair of pressure pins of a molding die clamp the soft magnetic body, at least one of the pair of pressure pins is brought into contact with the exposed portion, and molten molding resin is filled into the molding die in a state in which at least one of the pair of pressure pins is in contact with the exposed portion.

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