JP2012068158A - Current sensor and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure stability and reliability of current detecting accuracy by preventing a stress from acting on a magnetic sensor such as a hall element or on a junction part of the magnetic sensor and a circuit board, even when the expansion or contraction of a mold member due to temperature change occurs.SOLUTION: A container-shaped member 30 is installed in a gap 21 of a core 20 stored in a casing 10, and a resin mold member 60 is filled in the casing 10 so as to seal the core 20 in a state that an opening end part of the container-shaped member 30 is exposed to the outside. A magnetic sensor 40 is inserted from the opening of the container-shaped member 30 into the container-shaped member 30, and is arranged in the gap 21 of the core 20 inside the container-shaped member 30.

Description

  The present invention relates to a current sensor including an annular core having a gap formed therein and a magnetic sensor disposed in the gap of the core.

  An annular core having a gap formed therein and a magnetic sensor, for example, a hall element, disposed in the gap of the core, the magnetic flux generated in the core by the current flowing through the conductor passing through the core portion of the core is caused by the hall element. Conventionally, current sensors that convert electrical signals are known.

  In this type of current sensor, as seen in, for example, Patent Document 1, a core, a hall element, and a circuit board on which the hall element is mounted are accommodated in a casing, and a molded member made of a synthetic resin material ( It is generally known that the core and the Hall element are sealed and fixed in the mold member by filling and sealing the sealing material.

JP 2005-308526 A

  This type of current sensor is used in a wide variety of environments and is often used in an environment where a relatively large temperature change occurs. In such an environment, when a current sensor such as that disclosed in Patent Document 1 is used, expansion or contraction due to a temperature change of the mold member enclosing the core or the Hall element is likely to occur. Excessive stress may act on the Hall element enclosed in the mold member due to expansion or contraction.

  When the stress is applied to the Hall element in this way, the output characteristics of the Hall element change, which may cause a decrease in detection accuracy of the Hall element.

  In addition, when the Hall element and the circuit board are joined by soldering, stress is also applied to the joint between the Hall element and the circuit board due to expansion or contraction of the mold member due to a temperature change. There is also a risk of causing cracks and poor conduction.

  The present invention has been made in view of such a background, and even if expansion or contraction of a mold member due to a temperature change occurs, a magnetic sensor such as a Hall element or a joint between the magnetic sensor and a circuit board is thereby generated. It is an object of the present invention to provide a current sensor that can prevent stress from acting on the substrate and, in turn, can ensure stability and reliability of current detection accuracy. Furthermore, it aims at providing the method which can manufacture such a current sensor easily.

  In order to achieve the above object, a current sensor according to the present invention includes an annular core having a gap formed therein, and a magnetic sensor disposed in the gap of the core, the inner side of the inner peripheral surface of the core. An inner wall portion that forms a through-hole in the thickness direction of the core and an outer wall portion that surrounds the outer peripheral surface of the core, and the core is accommodated in a space between the inner wall portion and the outer wall portion. A container-like member interposed in a gap between a housing and a core accommodated in the housing, wherein one end in the thickness direction of the core is opened so that the magnetic sensor can be inserted, and the other end is closed; A resin mold member filled in a space between the outer wall portion and the inner wall portion of the casing so as to enclose the core in the state where the opening end portion of the container-like member is exposed to the outside. The magnetic sensor from an opening of the container-like member Is inserted into the container-like member, characterized in that it is arranged in the gap of the core within the container-like member (first invention).

  According to the current sensor of the first aspect of the present invention, the core accommodated in the space between the outer wall portion and the inner wall portion of the casing (hereinafter sometimes referred to as the core accommodating space) is contained in the core accommodating space. It will be enclosed in the resin mold member to be filled.

  In this case, the mold member is filled in the core housing space of the casing with the open end of the container-like member interposed in the gap of the core exposed to the outside. For this reason, the internal space of the container-like member interposed in the gap of the core becomes a space in which the mold member does not exist, and becomes a space that opens to the outside through the opening end portion of the container-like member.

  Then, the magnetic sensor is inserted into the container-like member from the opening of the container-like member, so that the magnetic sensor is disposed in the gap of the core in the space inside the container-like member where no mold member is present. Will be.

  Therefore, according to the current sensor of the first invention, even if expansion or contraction due to a temperature change of the mold member filled in the core housing space of the casing occurs, stress is applied to the magnetic sensor. Can be prevented. In addition, since the joint between the circuit board on which the magnetic sensor is mounted and the magnetic sensor is disposed outside or inside the container-like member (and thus outside the mold member), expansion or contraction of the mold member occurs. Even so, it is possible to prevent stress from acting on the joint.

  Therefore, according to the current sensor of the first invention, even if the mold member expands or contracts due to the temperature change, the stress is applied to the magnetic sensor or the joint between the magnetic sensor and the circuit board on which the magnetic sensor is mounted. It can be prevented from acting. As a result, it is possible to ensure the stability and reliability of the current detection accuracy indicated by the output of the magnetic sensor.

  In the current sensor according to the first aspect of the present invention, the opening end of the container-like member is provided with a flexible flange formed so as to protrude toward the inner wall portion and the outer wall portion of the casing. The outer dimension of the flexible flange in the direction of the interval between the inner wall portion and the outer wall portion of the housing is determined when the container-like member is inserted into the gap of the core in the thickness direction of the core. It is preferable that the dimension is set to be larger than the distance between the inner wall portion and the outer wall portion of the casing so as to be slidably contacted with the inner wall portion and the outer wall portion of the casing ( Second invention).

  According to the current sensor of the second aspect of the invention, since the outer dimension of the flexible flange in the interval direction between the inner wall portion and the outer wall portion of the casing is set as described above, the current sensor At the time of manufacturing, after the core is accommodated in the core accommodating space of the housing, when the container-like member is inserted into the gap of the core in the thickness direction of the core, the flange of the container-like member is The inner wall portion and the outer wall portion of the housing are slidably contacted while being bent. Therefore, the flange is elastically pressed against the inner wall portion and the outer wall portion, and the container-like member is locked to the inner wall portion and the outer wall portion of the housing by the pressing force. .

  For this reason, after inserting and interposing a container-like member in the gap of the core, a component for fixing the container-like member to the casing or the core when the core containing space is filled with the liquid material of the mold member It is possible to prevent the container-like member from being lifted up by buoyancy without requiring a jig or a jig. Therefore, the workability at the time of manufacturing the current sensor can be improved, and the manufacturing cost can be suppressed.

  Further, in the current sensor of the first invention or the second invention, the container-like member is formed such that a cross-sectional area inside thereof increases from the other end side of the container-like member toward the opening end side. It is preferable (3rd invention).

  According to the current sensor of the third aspect of the invention, since the transverse area of the opening end of the container-like member is a large area, the magnetic sensor can be easily inserted into the container member. Workability at the time of manufacturing the sensor can be improved.

  Further, the current sensor manufacturing method of the present invention is the current sensor manufacturing method, wherein the first step of accommodating the core in a space between the inner wall portion and the outer wall portion of the housing, A second step of inserting the container-like member into the gap of the core by inserting the container-like member in the thickness direction of the core; Filling the space between the inner wall portion and the outer wall portion of the casing with the liquid material of the mold member and exposing the housing to the outside, the core member is sealed inside the mold member. 3 steps, and then, a fourth step of inserting the magnetic sensor from the open end of the container-like member and disposing the magnetic sensor in the gap of the core inside the container-like member. (4th invention).

  According to this 4th invention, the said current sensor can be manufactured efficiently. In particular, when the current sensor of the second invention is manufactured, in the second step, the flange of the container-like member is in sliding contact with the inner wall portion and the outer wall portion of the housing while being bent. Therefore, as described above, the container-like member is locked to the inner wall portion and the outer wall portion of the casing. For this reason, in the third step, when the liquid material of the mold member is filled in the space (core housing space) between the inner wall portion and the outer wall portion of the housing, the container-like member is removed from the housing or the core. It is possible to prevent the container-like member from being lifted by buoyancy without requiring parts and jigs for fixing to the container.

  When the current sensor of the third invention is manufactured, the magnetic sensor can be easily inserted from the opening end of the container-like member in the fourth step.

The disassembled perspective view of the main components of the current sensor of one Embodiment of this invention. The figure which shows the product state obtained at the 1st process at the time of manufacture of the current sensor of embodiment. The figure which shows the product state obtained at the 2nd process at the time of manufacture of the current sensor of embodiment. The figure which shows the product state obtained at the 3rd process at the time of manufacture of the current sensor of embodiment. The figure which shows the AA line cross section of FIG. The figure which shows the BB sectional view of FIG. The figure which shows the product state obtained at the 4th process at the time of manufacture of the current sensor of embodiment.

  An embodiment of the present invention will be described below with reference to FIGS.

  As shown in FIG. 1, the current sensor 1 of the present embodiment includes a casing 10, a core 20, a container-like member 30, a magnetic sensor 40, and a circuit board 50 as main components.

  The core 20 is a ring-shaped member made of a magnetic material, and a gap 21 is formed in a part of a section of the entire length in the circumferential direction, which is a gap portion having a gap in the circumferential direction. In addition, although the core 20 of this embodiment is an annular thing, a square annular thing may be sufficient, for example.

  The housing 10 has a box-like shape opened upward, and includes a rectangular plate-like bottom plate 11, an outer wall portion 12 that is a rectangular frame that stands up from the outer peripheral edge of the bottom plate 11, and a bottom plate 11. The outer wall 12 is provided from the center of the upper surface and the inner wall 13 which is a rectangular frame that stands up with a gap, and the thickness direction of the core 20 (the axial center direction of the core 20) is the normal of the bottom plate 11 The core 20 is configured to be accommodated in the space between the outer wall portion 12 and the inner wall portion 13 in a direction (vertical direction). The housing state is a housing state in which the outer wall portion 12 surrounds the periphery of the outer peripheral surface of the core 20 and the inner wall portion 13 is disposed inside the inner peripheral surface of the core 20.

  In this case, the upper surface of the bottom plate 11 is disposed at a plurality of locations near the outer wall portion 12 in the space between the outer wall portion 12 and the inner wall portion 13 of the housing 10 (hereinafter, sometimes referred to as a core housing space). And an L-shaped pedestal 14 formed so as to protrude from the inner peripheral surface of the outer wall portion 12 is provided integrally with the bottom plate 11 and the outer wall portion 12 (or fixed to the bottom plate 11 and the outer wall portion 12). By placing the core 20 on the protruding portion on the bottom plate 11 side of the plurality of bases 14 and bringing the outer peripheral surface of the core 20 into contact with the protruding portion on the outer wall 12 side of the base 14 The accommodation position of the core 20 in the core accommodation space is defined.

  Further, bosses 15 having screw holes 15 a opened upward are provided so as to protrude from the bottom plate 11 at a plurality of locations near the outer wall portion 12 of the core housing space. The screw holes 15 a of these bosses 15 are for fastening the circuit board 50 with screws 52.

  Further, as shown in FIG. 5, a hole 11 a that communicates with the internal space of the inner wall portion 13 is formed in the center portion of the bottom plate 11 of the housing 10. For this reason, the internal space of the inner wall portion 13 becomes a through hole 13a penetrating in the thickness direction of the core 20 in a state where the core 20 is accommodated in the core accommodating space. This through-hole 13a is used as a hole for penetrating a conductor (not shown) through which a current to be detected by the current sensor 1 of the present embodiment is passed.

  In this embodiment, the magnetic sensor 40 is a Hall element (lead-type Hall element). The magnetic sensor 40 is mounted in advance on a circuit board 50 formed of a square plate-like printed wiring board by soldering. The circuit board 50 is formed in a size that can be accommodated in the core accommodating space of the housing 10 in a posture parallel to the bottom plate 11. The circuit board 50 is formed with holes 51 through which the screws 52 for fastening the same to the screw holes 15a of the boss 15 of the housing 10 are inserted.

  In addition to the magnetic sensor 40, a circuit element for shaping or outputting the detection signal of the magnetic sensor 40 may be mounted on the circuit board 50.

  The container-shaped member 30 is a container-shaped resin molded product having an open upper end as one end in the thickness direction of the core 20 and a closed lower end (the other end), and its open end (upper end). The magnetic sensor 40 can be inserted into the inside of the container 20 and the lower portion of the container-like member 30 is formed in a size that can be interposed in the gap 21 of the core 20. The material of the container member 30 is, for example, PET (Polyethylene terephthalate).

  In this embodiment, the container-like member 30 has a width equal to or smaller than the gap 21 of the core 20 (width in the gap 21 gap direction), and has a bottom with a magnetic sensor 40 accommodated therein. The bottom side portion 31 of the core 20 and a width wider than the gap 21 of the core 20 (the width in the gap direction of the gap 21) and projecting laterally outward from the side surface portion of the bottom side portion 31 And a cylindrical opening-side portion 32 connected to the upper end of the bottom-side portion 31 via a step portion, and laterally outward from the outer peripheral edge of the upper-end portion of the opening-side portion 32 as the opening end portion of the container-like member 30. It is comprised from the flexible flange 33 formed so that it may protrude in the direction, and the bottom part 31 can be interposed in the gap 21 of the core 20. FIG.

  In this case, in this embodiment, the cross-sectional shape of the bottom side portion 31 and the opening side portion 32 is a square shape, and the shape of the flange 33 is a square ring shape. Further, the outer dimension (depth dimension) of the flange 33 in the radial direction of the core 20 (the distance direction between the outer wall 12 and the inner wall 13 of the housing 10) is the outer wall 12 of the housing 10. The dimension is set slightly larger than the distance between the inner peripheral surface of the inner wall surface and the outer peripheral surface of the inner wall portion 13. The outer dimension of the flange 33 in the radial direction of the core 20 is the dimension D1 shown in FIG. 1, and is between the inner peripheral surface of the outer wall portion 12 and the outer peripheral surface of the inner wall portion 13 of the housing 10. The interval is the dimension D2 (<D1) shown in FIG.

  Further, as shown in FIGS. 5 and 6, the side surface of the bottom portion 31 is formed so that the cross-sectional area of the bottom portion 31 decreases from the upper side to the lower side (in other words, the bottom side portion 31 The portion 31 is formed in a tapered surface shape so as to taper from the upper side toward the lower side. Similarly, the side surface of the opening side portion 32 is also formed in a tapered surface shape so that the cross-sectional area of the opening side portion 32 decreases from the upper side toward the lower side.

  In the present embodiment, as shown in FIG. 5, the bottom portion 31 of the container-like member 30 in the radial direction of the core 20 (the interval direction between the outer wall portion 12 and the inner wall portion 13 of the housing 10). The outer dimension (depth dimension) of the opening-side portion 32 is set to be smaller than the width in the radial direction of the core 20 (interval between the outer peripheral surface and the inner peripheral surface of the core 20).

  Supplementally, in the present embodiment, the flange 33 is formed on the entire circumference of the opening end of the container-like member 30, but only in a portion facing the outer wall 12 and the inner wall 13 of the housing 10. The flange 33 may be formed.

  The current sensor 1 including the casing 10, the core 20, the container-like member 30, the magnetic sensor 40, and the circuit board 50 is manufactured as follows.

  First, as shown in FIG. 2, the core 20 is accommodated in a space (core accommodating space) between the outer wall 12 and the inner wall 13 of the housing 10. At this time, the core 20 is placed on the protruding portion on the bottom plate 11 side of the plurality of pedestals 14, and the outer peripheral surface of the core 20 is brought into contact with the protruding portion on the outer wall 12 side of the pedestal 14. The accommodation position of the core 20 in the accommodation space is defined.

  Next, the bottom portion 31 of the container-like member 30 is inserted into the gap 21 of the core 20 from above, so that the bottom portion 31 is interposed in the gap 21 as shown in FIG. At this time, the depth dimension D1 of the flange 33 of the container-like member 30 (the outer dimension of the flange 33 in the radial direction of the core 20) is the inner peripheral surface and inner wall of the outer wall portion 12 of the housing 10 as described above. Since it is slightly larger than the distance between the outer peripheral surface of the portion 13 and the flange 33 is bent between the inner peripheral surface of the outer wall portion 12 and the outer peripheral surface of the inner wall portion 13 as shown in FIG. It is in sliding contact with the wall 12 and the inner wall 13. Accordingly, the flange 33 of the container-like member 30 is elastically pressed against the outer wall portion 12 and the inner wall portion 13, and the container-like member 30 is flanged against the outer wall portion 12 and the inner wall portion 13 by the pressing force. It is locked via 33. In FIG. 5, the casing 10 is filled with a mold member 60 to be described later. However, in the state shown in FIG. 3, the mold member 60 is not yet filled in the casing 10.

  Supplementally, since the opening-side portion 32 of the container-like member 30 has a width larger than the gap 21 of the core 20, the container-like member 30 does not enter the gap 21 of the core 20. Only the bottom portion 31 of the container-like member 30 is inserted into the gap 21.

  Further, in FIG. 5, the container-like member 30 is locked to the outer wall portion 12 and the inner wall portion 13 via the flange 33 with the lower end of the opening side portion 32 slightly separated from the upper surface of the core 20. However, the bottom side portion 31 of the container-like member 30 may be inserted into the gap 21 of the core 20 until the lower end of the opening-side portion 32 of the container-like member 30 contacts the upper surface of the core 20.

  Next, as shown in FIG. 4, the liquid of the mold member 60 made of a synthetic resin material is formed in a space (core housing space) between the inner peripheral surface of the outer wall portion 12 and the outer peripheral surface of the inner wall portion 13 of the housing 10. Fill and harden. Thereby, the core 20 is sealed inside the mold member 60. The synthetic resin material constituting the mold member 60 is, for example, a urethane resin.

  In this case, as shown in FIGS. 5 and 6, the depth (thickness) of the mold member 60 filled in the core housing space is such that the entire core 20 is buried in the mold member 60. The distance between the bottom plate 11 of the housing 10 and the opening end of the container-shaped member 30 and the height of the boss 15 (height from the upper surface of the bottom plate 11) are set to be smaller. Thereby, the upper surface of the mold member 60 is positioned lower than the opening end of the container-like member 30 and the upper end face of the boss 15, and the opening end of the container-like member 30 and the upper end face of the boss 15 (and thus screw holes 15a) is exposed to the outside of the mold member 60, and the mold member 60 is not supplied into the container-like member 30 or the screw holes 15a of the boss 15. Further, the bottom side portion 31 embedded in the mold member 60 of the container-like member 30 is fixed to the housing 10 and the core 20 through the cured mold member 60.

  Since the container-like member 30 is locked to the outer wall portion 12 and the inner wall portion 13 of the housing 10 via the flange 33 as described above, the mold member 60 is placed in the core housing space of the housing 10. When the liquid material is filled, it is possible to prevent the container-like member 30 from being lifted by buoyancy. As a result, the container-like member 30 is prevented from being displaced when the liquid material in the mold member 60 is filled.

  Next, as shown in FIGS. 5 and 6, the magnetic sensor 40 and the circuit board 50 are placed on the container-like member 30 in a state where the magnetic sensor 40 mounted on the circuit board 50 is positioned below the circuit board 50. The magnetic sensor 40 is moved from above the opening end to below, and the magnetic sensor 40 is inserted from the opening end of the container-like member 30 to the inside of the bottom portion 31. This insertion is performed until each circuit board 50 comes into contact with the upper end surface of each boss 15 such that each hole 51 of the circuit board 50 faces the screw hole 15 a of each boss 15 of the housing 10. Then, the circuit board 50 is fastened (fixed) to the housing 10 by inserting a screw 52 into each hole 51 of the circuit board 50 and screwing the screw 52 into the screw hole 15 a of the boss 15.

  By inserting the magnetic sensor 40 into the bottom portion 31 of the container-shaped member 30 as described above, the magnetic sensor 40 is disposed in the gap 21 of the core 20. Thereby, the current sensor 1 shown in FIG. 7 is manufactured.

  In this case, the side surfaces of the bottom side portion 31 and the opening side portion 32 of the container-like member 30 are formed in a tapered surface as described above, and the upper side of the container-like member 30 is crossed by the container-like member 30. Since the area has a larger area than the size of the magnetic sensor 40, the magnetic sensor 40 can be easily and smoothly inserted into the bottom portion 31.

  In the current sensor 1 of the present embodiment manufactured as described above, the magnetic sensor 40 (the Hall element) is inserted into the container-like member 30 interposed in the gap 21 of the core 20 so that the magnetic sensor 40 is placed in the container. It is arranged in the gap 21 of the core 20 inside the shaped member 30. In this case, the core 20 accommodated in the core accommodating space of the housing 10 is enclosed in the mold member 60 filled in the core accommodating space, but the mold member 60 exists in the container-like member 30. do not do. Further, the circuit board 50 on which the magnetic sensor 40 is mounted is also arranged outside the mold member 60.

  For this reason, even if expansion or contraction of the mold member 60 due to a temperature change occurs, no stress acts on the magnetic sensor 40 or the joint between the magnetic sensor 40 and the circuit board 50. As a result, the characteristic change of the magnetic sensor 40 and the occurrence of cracks at the joint between the magnetic sensor 40 and the circuit board 50 can be prevented. As a result, the stability and reliability of the detection accuracy of the manufactured current sensor 1 can be ensured.

  In the embodiment described above, the container-like member 30 has a shape having a step between the opening-side portion 32 and the bottom-side portion 31, but may have a shape without the step.

  Moreover, in the said embodiment, although the outer side wall part 12 and the inner side wall part 13 of the housing | casing 10 were a rectangular frame shape, both or one of them may be a circular frame shape, for example.

  In the above embodiment, the circuit board 50 is fastened to the boss 15 of the housing 10 with the screw 52. However, the circuit board 50 is fixed to the housing 10 with an adhesive or an appropriate locking structure. Also good.

  Moreover, although the magnetic sensor 40 in the said embodiment is a Hall element, magnetic sensors other than a Hall element, for example, a magnetoresistive element, may be sufficient.

  DESCRIPTION OF SYMBOLS 1 ... Current sensor, 10 ... Housing | casing, 12 ... Outer wall part of housing | casing, 13 ... Inner side wall part of housing | casing, 13a ... Through-hole, 20 ... Core, 21 ... Core gap, 30 ... Container-shaped member, 33 ... Flange, 40 ... Magnetic sensor (Hall element), 60 ... Mold member.

Claims (4)

In an electric current sensor comprising an annular core having a gap formed therein and a magnetic sensor disposed in the gap of the core,
An inner wall portion that forms a through hole in the thickness direction of the core on the inner side of the inner peripheral surface of the core and an outer wall portion that surrounds the outer peripheral surface of the core, and between the inner wall portion and the outer wall portion A housing that accommodates the core in the space;
A container-like member interposed in the gap of the core accommodated in the housing, having one end in the thickness direction of the core opened so that the magnetic sensor can be inserted, and the other end closed;
A resin mold member filled in a space between the outer wall portion and the inner wall portion of the casing so as to enclose the core in the state where the opening end portion of the container-like member is exposed to the outside. And
The current sensor, wherein the magnetic sensor is inserted into the container-like member through an opening of the container-like member, and is disposed in the gap of the core inside the container-like member. The current sensor according to claim 1,
The opening end of the container-like member is provided with a flexible flange formed so as to protrude toward the inner wall and the outer wall of the casing, and the inner wall of the casing The outer dimension of the flexible flange in the spacing direction between the outer wall and the outer wall is such that when the container-like member is inserted into the gap of the core in the thickness direction of the core, A current sensor characterized in that the dimension is set to be larger than the interval between the inner wall portion and the outer wall portion of the casing so as to be in sliding contact with the outer wall portion while being bent. The current sensor according to claim 1 or 2,
The said container-like member is formed so that the cross-sectional area of the inside may become large toward the opening edge part side from the other end side of this container-like member, The current sensor characterized by the above-mentioned. It is a manufacturing method of the current sensor given in any 1 paragraph of Claims 1-3,
A first step of accommodating the core in a space between an inner wall portion and an outer wall portion of the housing;
Next, a second step of interposing the container-like member in the gap by inserting the container-like member into the gap of the core in the thickness direction of the core;
Then, while exposing the open end of the container-like member to the outside, filling the liquid material of the mold member into the space between the inner wall portion and the outer wall portion of the housing to cure the container-like member, A third step of encapsulating the core in the mold member;
And a fourth step of inserting the magnetic sensor from the open end of the container-like member and disposing the magnetic sensor in the gap of the core inside the container-like member. Manufacturing method.

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