Current sensor and method for manufacturing current sensor

Abstract

To strongly fix a magnetic detection element.SOLUTION: A current sensor includes: an annular core as an annular magnetic body having a magnetic gap which is a physical cut; a mold member for sealing the annular core at least partially; a magnetic detection element arranged in the magnetic gap; and a substrate connected to a terminal of the magnetic detection element. The mold member has a recessed trench in which the magnetic detection element is arranged. In the inner periphery of the recessed trench, a supporting unit for holding the magnetic detection element along the peripheral direction of the annular core is formed. A sealing material is filled between the inner periphery of the recessed trench and the magnetic detection element.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a current sensor and a method for manufacturing a current sensor. [Background technology]

[0002] Current sensors incorporated in various devices are required to be small, highly accurate, and durable. In particular, current sensors mounted on vibrating or moving objects are required to be protected against external forces. Patent Document 1 discloses a current sensor including a magnetic core surrounding a bus bar through which a current flows, a magnetic sensor having a notch in the magnetic core, a circuit board on which the magnetic sensor is mounted, and a case having a pair of opposing clamping pieces that fit into the notch in the magnetic core, the magnetic core and the circuit board being fixed to the case, the magnetic sensor standing up from the circuit board with its legs and positioned in the notch in the magnetic core, and the magnetic sensor being fitted between the pair of clamping pieces in the case to be positioned relative to the magnetic core. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-205194 A Summary of the Invention [Problem to be solved by the invention]

[0004] The invention described in Patent Document 1 leaves room for improvement in terms of how the magnetic detection element is fixed. [Means for solving the problem]

[0005] A current sensor according to a first aspect of the present invention comprises an annular core which is a ring-shaped magnetic body having a magnetic gap which is a physical break, a molding member which at least partially seals the annular core, a magnetic detection element arranged in the magnetic gap, and a substrate connected to the terminals of the magnetic detection element, wherein the molding member has a concave groove in which the magnetic detection element is arranged, a support portion is formed on the inner circumference of the concave groove which clamps the magnetic detection element along the circumferential direction of the annular core, and a sealing material is filled between the inner circumference of the concave groove and the magnetic detection element. A manufacturing method for a current sensor according to a second aspect of the present invention includes an annular core which is a ring-shaped magnetic body having a magnetic gap which is a physical break, a molding member which at least partially seals the annular core, a magnetic detection element arranged in the magnetic gap, and a substrate connected to a terminal of the magnetic detection element, wherein the molding member has a concave groove in which the magnetic detection element is arranged, and a support portion which holds the magnetic detection element along the circumferential direction of the annular core is formed on the inner circumference of the concave groove, and a sealant is filled between the inner circumference of the concave groove and the magnetic detection element, and includes a first step of arranging the sealant in the concave groove, a second step of arranging the magnetic detection element on the support portion, and a third step of connecting an element terminal which is a terminal of the magnetic detection element protruding outward from the concave groove to the substrate, and the order of the first step and the second step can be reversed. Effect of the Invention

[0006] According to the present invention, the magnetic detection element can be firmly fixed. [Brief description of the drawings]

[0007] [Figure 1] Perspective view of a current sensor [Diagram 2] Exploded perspective view of a current sensor [Diagram 3] Close-up of the concave groove [Figure 4] Cross-section of the current sensor [Diagram 5] A diagram showing two methods of manufacturing a current sensor. [Figure 6]Cross-sectional view of a current sensor according to a comparative example DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] --Embodiment-- Hereinafter, an embodiment of the current sensor will be described with reference to Fig. 1 to Fig. 6. In this embodiment, for convenience of explanation, mutually orthogonal X, Y and Z axes are also shown in each figure.

[0009] FIG. 1 is a perspective view of a current sensor 1. The current sensor 1 measures a three-phase AC current. Specifically, the current sensor 1 measures the current of each phase of a U-phase busbar 80U, a V-phase busbar 80V, and a W-phase busbar 80W independently. Since each busbar is not a component of the current sensor 1, each busbar is shown by a dashed line in FIG. 1. The current sensor 1 includes an annular core 2, a molded member 3, a magnetic detection element 4, and a substrate 5. However, the magnetic detection element 4 is not shown in FIG. 1, and only the end of an element terminal 41 connected to the magnetic detection element 4 is shown. The substrate 5 is a plate-shaped member having a thickness in the Z-axis direction.

[0010] 2 is an exploded perspective view of the current sensor 1. The configuration for measuring each of the UVW phases in the current sensor 1 is the same, so the configuration for measuring the current of the V-phase busbar 80V will be described below. The molded member 3 has a concave groove 33 which is a non-through hole. The concave groove 33 penetrates the molded member 3 in the Z-axis direction, and has a support part 32 for fixing the magnetic detection element 4 on its inner circumference as described later. The magnetic detection element 4 is inserted into the concave groove 33, and is further filled with a potting material described later. The magnetic detection element 4 has a substantially rectangular cross section in the XY plane.

[0011] FIG. 3 is an enlarged view of the concave groove 33. However, for convenience of drawing, the bottom of the concave groove 33 is not shown. The left view of FIG. 3 is a view seen from the Z-axis plus side, and the right view of FIG. 3 is a view obtained by rotating the viewpoint around the Y-axis. The left view of FIG. 3 shows the magnetic detection element 4 by a broken line. The concave groove 33 has a first support portion 321, a second support portion 322, a third support portion 323, a fourth support portion 324, a fifth support portion 325, and a sixth support portion 326 on the inner periphery. The first support portion 321 to the sixth support portion 326 are also collectively referred to as the support portion 32. The support portion 32 supports the magnetic detection element 4. Specifically, the first support portion 321 and the fourth support portion 324 support the magnetic detection element 4 by sandwiching it from both sides of the Y-axis.

[0012] The second support portion 322, the third support portion 323, the fifth support portion 325, and the sixth support portion 326 sandwich and support the magnetic detection element 4 from both sides of the X-axis. Therefore, the positions of the magnetic detection element 4 in the X-axis and Y-axis directions are fixed. Note that, in order to prevent the magnetic detection element 4 from being misaligned due to rotation around the Z-axis, the second support portion 322 and the sixth support portion 326 are disposed closer to the positive side of the Y-axis, and the third support portion 323 and the fifth support portion 325 are disposed closer to the negative side of the Y-axis.

[0013] Furthermore, near the surface on the positive side of the Z axis of the molded member 3, the support parts 32 have a tapered shape with a cross-sectional area that decreases toward the surface. In other words, the groove 33 is formed so that the diameter of the opening side gradually increases toward the side where the substrate 5 is placed. This allows the magnetic detection element 4 to be smoothly inserted into the groove 33 from the positive side of the Z axis. The cross section of the magnetic detection element 4 is approximately rectangular, and the support parts 32 are discretely placed on the inner circumference of the groove 33. Therefore, even when the magnetic detection element 4 is placed in the groove 33, there are gaps. These gaps are filled with the potting member 7, which will be described later.

[0014] FIG. 4 is a cross-sectional view of the current sensor 1. However, in FIG. 4, the support portion 32 is omitted for convenience of drawing. The annular core 2 has a ring shape with a slit, and the slit area is called the magnetic gap 20. Of the end faces of the annular core 2 that form the magnetic gap 20, the negative side of the X-axis is called the first end face 21, and the positive side of the X-axis is called the second end face 22. The direction connecting the first end face 21 and the second end face 22, i.e., the direction parallel to the X-axis, is called the first direction. The first direction can also be called the "circumferential direction" of the annular core 2. The magnetic gap 20 is illustrated as the area indicated by the reference symbol 20 in the box on the right of FIG. 4.

[0015] Since the concave groove 33 is provided in the magnetic gap 20, the magnetic detection element 4 inserted into the concave groove 33 is ultimately disposed in the magnetic gap 20. When a current is applied to the V-phase bus bar 80V, a magnetic field is generated and magnetic flux flows in the annular core 2. The magnetic detection element 4 disposed in the magnetic gap 20 detects the magnetic flux flowing in the annular core 2. A signal of the magnetic flux detected by the magnetic detection element 4 is processed by a processing circuit (not shown) mounted on the substrate 5.

[0016] The magnetic detection element 4 has the element terminals 41 connected to the substrate 5. As described above, the magnetic detection element 4 is fixed in position in the X-axis and Y-axis directions by the support parts 32 of the concave grooves 33, so that the generation of strong stress at the portions of the element terminals 41 connected to the substrate 5 is prevented.

[0017] The potting member 7 is placed in the concave groove 33 prior to the magnetic detection element 4. When the magnetic detection element 4 is inserted into the concave groove 33, the potting member 7 is pushed out in the positive direction of the Z axis from the gap between the support portion 32 and the magnetic detection element 4, resulting in the state shown in Fig. 4. At this time, the magnetic detection element 4 abuts against the groove bottom 33B, which is the bottom of the concave groove 33, and the magnetic detection element 4 is simultaneously positioned in the Z axis direction. The potting member 7 is, for example, silicone curing rubber.

[0018] Molded member 3 includes a first molded portion 35 in contact with first end face 21 and second end face 22 of annular core 2, and a second molded portion 36 that covers substantially the entire circumference of the Z-axis positive half of annular core 2 and does not contact first end face 21 and second end face 22. In manufacturing molded member 3, first molded portion 35 is formed, and then second molded portion 36 is formed. However, it is not essential to provide first molded portion 35 and second molded portion 36, and first molded portion 35 and second molded portion 36 may be integrally formed.

[0019] FIG. 5 is a diagram showing two manufacturing methods of the current sensor 1. Both manufacturing methods consist of three steps, and the third step is common to both. FIG. 5 shows the concave groove 33 before the start of the first step, after the completion of the first step, after the completion of the second step, and after the completion of the third step. Before the start of the manufacturing steps described below, the concave groove 33 is formed in the mold member 3, and further, the support portion 32 is formed in the concave groove 33. Note that the manufacturing methods described below may be executed by a computer in which a processing procedure is registered, or may be executed by a human being.

[0020] <First manufacturing method> In the first manufacturing method, in the first step, the potting member 7 is placed in the groove 33 of the molded member 3. At this time, the potting member 7 is placed at the groove bottom 33B, not near the entrance of the groove 33. In the second step, the magnetic detection element 4 is inserted into the groove 33, and the magnetic detection element 4 is sandwiched by the support portion 32. When the magnetic detection element 4 is inserted into the groove 33, the potting member 7 that was previously inserted into the groove 33 moves from the gap between the magnetic detection element 4 and the support portion 32 to the upper portion of the groove 33. In FIG. 5, the potting member 7 is shown only above the magnetic detection element 4 for convenience of drawing, but in reality, it is also placed in the gap of the support portion 32. In the third step, the element terminal 41, which is the terminal of the magnetic detection element 4 protruding from the groove 33 to the outside, is connected to the substrate 5.

[0021] <Second manufacturing method> The second manufacturing method is a manufacturing method in which the potting member 7 is placed later. In the second manufacturing method, in a first step, the magnetic detection element 4 is placed inside the concave groove 33 so that the magnetic detection element 4 is sandwiched by the supports 32 formed on the inner circumference of the concave groove 33. In a second step, the potting member 7 is filled inside the concave groove 33, and the magnetic detection element 4 is fixed to the concave groove 33. The third step is similar to the first manufacturing method.

[0022] <Comparative Example> FIG. 6 is a cross-sectional view of the comparative current sensor 1Z. The comparative current sensor 1Z includes a comparative groove 33Z in the molded member 3. The comparative groove 33Z does not include a support portion 32, unlike the groove 33 in the present embodiment. Therefore, the magnetic detection element 4 may vibrate due to an external force, etc., and stress concentration is unavoidable at the base of the element terminal 41. In addition, the groove 33 needs to be large so that the magnetic detection element 4 does not collide with the wall surface of the groove 33 even if it vibrates, and the magnetic gap 20 needs to be widened. That is, the comparative current sensor 1Z has a lower degree of freedom in design than the current sensor 1 in the present embodiment.

[0023] According to the above-described embodiment, the following advantageous effects can be obtained. (1) The current sensor 1 includes an annular core 2, which is an annular magnetic body having a magnetic gap 20 that is a physical gap, a molded member 3 that at least partially seals the annular core 2, a magnetic detection element 4 disposed in the magnetic gap 20, and a substrate 5 that is connected to an element terminal 41 of the magnetic detection element 4. The molded member 3 has a concave groove 33 in which the magnetic detection element 4 is disposed. On the inner circumference of the concave groove 33, a support portion 32 that sandwiches the magnetic detection element 4 along the circumferential direction of the annular core 2, i.e., the X-axis direction, is formed, specifically, a second support portion 322, a third support portion 323, a fifth support portion 325, and a sixth support portion 326. A sealant is filled between the inner circumference of the concave groove 33 and the magnetic detection element 4. Therefore, the magnetic detection element 4 can be firmly fixed. The magnetic detection element 4 is firmly fixed, which has the following two advantages. First, it is possible to prevent stress from concentrating on the end of the element terminal 41 that supports the magnetic detection element 4 on the substrate 5 side. Secondly, since the position of the magnetic detection element 4 is fixed and there is no need to provide space between the magnetic detection element 4 and the concave groove 33 to accommodate movement of the magnetic detection element 4, the design freedom can be increased, for example, in terms of the length of the magnetic gap 20 and the detection accuracy of the magnetic detection element 4.

[0024] 3, the groove 33 is formed so that the diameter of the opening side gradually increases toward the side where the substrate 5 is placed, i.e., the positive side of the Z axis. This allows the magnetic detection element 4 to be easily inserted into the groove 33 and prevents the magnetic detection element 4 from getting caught and causing an excessive load when inserted.

[0025] (3) The first support portion 321 and the fourth support portion 324 of the support portion 32 sandwich the magnetic detection element 4 in a direction perpendicular to the circumferential direction, i.e., along the Y-axis direction as well. This makes it possible to fix the magnetic detection element 4 even more firmly.

[0026] (Variation 1) In the embodiment described above, the supporting portion 32 sandwiches the magnetic detection element 4 in both the X-axis direction and the Y-axis direction. However, it is sufficient that the supporting portion 32 sandwiches the magnetic detection element 4 at least in the X-axis direction, and it is not necessary for the supporting portion 32 to sandwich the magnetic detection element 4 in the Y-axis direction. Specifically, the supporting portion 32 does not have to include the first supporting portion 321 and the fourth supporting portion 324.

[0027] (Variation 2) In the embodiment described above, the support portion 32 is formed so that the diameter of the opening side gradually increases toward the side where the substrate 5 is disposed. However, the cross section of the support portion 32 in the XY plane may be constant regardless of the Z-axis direction.

[0028] (Variation 3) In the embodiment described above, the molded member 3 covers only the positive half of the annular core 2 in the Z-axis direction. However, the molded member 3 may cover the entire annular core 2. In this case, the current sensor 1 becomes slightly larger, but since the molded member 3 completely covers the periphery of the annular core 2, the current sensor 1 becomes more robust.

[0029] (Variation 4) In the embodiment described above, the configuration for measuring each of the UVW phases in the current sensor 1 is the same. However, the configuration for measuring each phase does not have to be the same, and it is sufficient that the magnetic detection element 4 for measuring at least one phase is supported by the support portion 32.

[0030] (Variation 5) In the above embodiment, the current sensor 1 measures three phases. However, it is sufficient for the current sensor 1 to measure at least one phase, in other words, one current. The current sensor 1 may also measure four or more currents.

[0031] The above-mentioned embodiments and modifications may be combined with each other. Although various embodiments and modifications have been described above, the present invention is not limited to these. Other aspects that are conceivable within the scope of the technical idea of ​​the present invention are also included in the scope of the present invention. [Explanation of symbols]

[0032] 1: Current sensor 2: Annular core 3: Molding material 4: Magnetic detection element 5: Substrate 7: Potting material 20: Magnetic gap 21: First end surface 22: Second end surface 32: Support part 321: 1st support part 322:Second support part 323: Third support part 324: 4th support part 325: 5th support part 326: 6th support part 33: Concave groove 33B: Groove bottom 41: Element terminal

Claims

1. a ring-shaped core that is a ring-shaped magnetic body having a magnetic gap that is a physical gap; a mold member at least partially enclosing the annular core; a magnetic detection element disposed in the magnetic gap; a substrate connected to a terminal of the magnetic detection element; the molding member has a concave groove in which the magnetic detection element is disposed, a support portion is formed on an inner periphery of the recessed groove to sandwich the magnetic detection element along a circumferential direction of the annular core, A sealant is filled between the inner periphery of the concave groove and the magnetic detection element.

2. 2. The current sensor according to claim 1, The current sensor is such that the diameter of the opening side of the concave groove gradually increases toward the side on which the substrate is placed.

3. 2. The current sensor according to claim 1, The support portion also holds the magnetic detection element in a direction perpendicular to the circumferential direction.

4. A method for manufacturing a current sensor comprising: an annular core which is a ring-shaped magnetic body having a magnetic gap which is a physical break; a molding member which at least partially seals the annular core; a magnetic detection element which is disposed in the magnetic gap; and a substrate which is connected to a terminal of the magnetic detection element, the molding member having a concave groove in which the magnetic detection element is disposed, a support portion which holds the magnetic detection element in a circumferential direction of the annular core on an inner periphery of the concave groove, and a sealant which is filled between the inner periphery of the concave groove and the magnetic detection element, a first step of disposing the sealing material in the recessed groove; a second step of disposing the magnetic detection element on the support; a third step of connecting an element terminal of the magnetic detection element protruding from the concave groove to the substrate; The method for manufacturing a current sensor, wherein the first step and the second step can be interchanged in order.

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