Current detector

Abstract

The present invention provides a technique for ensuring a long creepage distance.　Provided is a current sensor 100, wherein a magnetic core 110, an inner coating part 120, and an outer coating part 130 are integrally provided by two-stage insert molding. As a result of the insert being fixed in the mold during molding, an inner opening 123 is formed in the inner coating 120, and an outer opening 134 is formed in the outer coating 130. However, since the outer opening 134 is separated from the inner opening 123 and does not overlap the inner opening 123, the magnetic core 110 is not exposed from the outer opening 134. Therefore, in the current sensor 100, it is possible to ensure a longer creepage distance than a current sensor in which the magnetic core is exposed from an opening formed in a wall part of a case body. In addition, since a circuit board on which a magnetosensitive element is mounted is positioned in relation to the inner covering part 120 formed integrally with the magnetic core 110, the positional accuracy of the magnetosensitive element with respect to the magnetic core 110 can be further improved.

Description

Current detector

[0001] The present invention relates to a current detector.

[0002] In a current detector, a case made of an insulating material is provided around the core to provide insulation between a primary conductor through which a current to be detected flows and a core made of a magnetic material. For example, a current sensor in which a magnetic core and a molded resin are integrally molded by insert molding is known (see, for example, Patent Document 1).

[0003] JP 2010-203910 A

[0004] In current detectors, in accordance with standards such as UL and IEC, a certain insulation distance (creepage distance and clearance distance) corresponding to the input voltage is required between the primary-side conductive part and the secondary-side conductive part. During insert molding, the core is inserted into a mold and held in place before the molding resin is injected to form the case, resulting in an opening in the case where the core is fixed. As a result, in current detectors with cases obtained by simple insert molding, the core is exposed from the opening, which limits the creepage distance that can be ensured and makes it difficult to guarantee high withstand voltage.

[0005] Therefore, an object of the present invention is to provide a technique for ensuring a long creepage distance.

[0006] In order to solve the above problems, the present invention employs the following current detector. Note that the following words in parentheses are merely examples, and the present invention is not limited thereto.

[0007] That is, the current detector of the present invention comprises a magnetic core having a gap formed in the middle of a ring-shaped magnetic path that converges a magnetic field generated by the conduction of a current to be detected; an inner covering portion that covers the surface of the magnetic core and has a first inner opening formed corresponding to the gap and a plurality of second inner openings different from the first inner opening; and an outer covering portion that covers the surface of the inner covering portion and bites into the second inner opening and has a first outer opening formed corresponding to the first inner opening and a plurality of second outer openings different from the first outer opening that are formed in positions that do not overlap with the second inner openings.

[0008] In this current detector, the case body is composed of an inner covering portion and an outer covering portion. As a result of the insert being fixed by a mold during molding of the case body, the inner covering portion and the outer covering portion each have an opening (a second inner opening and a second outer opening) formed at the fixing position of the insert, but the second outer opening of the outer covering portion is formed in a position that does not overlap the second inner opening of the inner covering portion, so that the magnetic core is not exposed from the second outer opening.

[0009] Therefore, with the current detector of this aspect, a longer creepage distance can be ensured by the distance from the second outer opening to the second inner opening, compared to when the magnetic core is exposed from the opening formed in the case body during molding as described above. Furthermore, by covering the surface of the magnetic core with the inner covering and the surface of the inner covering with the outer covering, the magnetic core, the inner covering, and the outer covering are in close contact with each other, which improves the accuracy of the position of the core relative to the case body.

[0010] More preferably, in the current detector of the above aspect, the inner covering portion has a plurality of protrusions on an inner circumferential wall surface surrounding a hole penetrating the center of the inner covering portion, and the outer covering portion has an outer circumferential wall surrounding the hole penetrating the center that is wedged into the protrusions. Also, the outer covering portion does not have a second outer opening formed in an outer circumferential wall located radially of the hole penetrating the center of the outer covering portion. Alternatively, the outer covering portion has an outer circumferential wall that is continuous and flush with the protrusions.

[0011] When molding the outer covering, the inner covering that covers the surface of the magnetic core is fixed in place using a mold. In this current detector, multiple protrusions are provided on the inner peripheral wall (the inner peripheral surface of the inner covering), and by inserting a part of the mold along these protrusions, the position of the central hole in the radial direction (= directions perpendicular to the central axis (Y axis) of the hole; X direction and Z direction) can be fixed. This allows the outer covering to be molded using a mold with a simple structure, reducing mold costs and reducing the number of second outer openings formed in the outer covering.

[0012] More preferably, the current detector of any of the above aspects further includes a circuit board having a magnetic sensing element mounted thereon and disposed within the gap, the inner covering portion having a portion for determining the position of the circuit board inside the first inner opening, and the outer covering portion having the first outer opening larger than the first inner opening and surrounding the first inner opening.

[0013] In this current detector, when the circuit board is installed in the gap, the positioning of the circuit board is determined by the inner coating that covers and adheres to the magnetic core, and the outer coating is not involved in the positioning, which further improves the positioning accuracy of the magnetic sensing element relative to the magnetic core and stabilizes the performance of the current sensor.

[0014] As described above, according to the present invention, a long creepage distance can be ensured.

[0015] 1 is a perspective view of a current sensor 100 according to an embodiment; FIG. 2 is a diagram illustrating a manufacturing process for the current sensor 100; FIG. 3 is a diagram (1 / 3) illustrating an inner covering portion 120; FIG. 4 is a diagram (2 / 3) illustrating an inner covering portion 120; FIG. 5 is a diagram (3 / 3) illustrating an inner covering portion 120; FIG. 6 is a diagram (1 / 2) illustrating an outer covering portion 130; FIG. 7 is a diagram (2 / 2) illustrating an outer covering portion 130; A cross-sectional view illustrating the positional relationship between a core 110, the inner covering portion 120, and the outer covering portion 130; An exploded perspective view of the current sensor 100; A diagram illustrating an insulation distance in the current sensor 100; A diagram illustrating a current sensor 200′ as a first comparative example; A diagram illustrating a current sensor 300′ as a second comparative example.

[0016] [Configuration of Current Sensor] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a current sensor 100 according to one embodiment. FIG. 1A is a perspective view from the front side, and FIG. 1B is a perspective view from the rear side. For ease of explanation, in all figures, the up-down, left-right, and front-rear directions in FIG. 1 are defined as the up-down, left-right, and front-rear directions of each component, and the shape and structure will be described accordingly. Furthermore, the up-down, left-right, and front-rear directions of a component may be referred to as the Z direction, the X direction, and the Y direction, respectively.

[0017] Current sensor 100 includes a core and a circuit board housed in a case body 102. Case body 102 is made of resin and has a generally annular shape, with a through-hole 104 penetrating its center. A connector 106 is provided on the top of current sensor 100. A primary conductor (e.g., a bus bar) through which a current to be detected flows is inserted into through-hole 104 of current sensor 100, and an external connector having connection terminals connected to an external device or circuit board is inserted into connector 106.

[0018] To facilitate understanding of the structure of the current sensor 100, a manufacturing process for the current sensor 100 will be briefly described with reference to FIG.

[0019] 2A, the core 110 has a C-shape when viewed from the front, with a gap 112 between the opposing end faces. When the gap 112 is included, the core 110 has a substantially rectangular ring shape. The core 110 is made of a magnetic material (e.g., silicon steel).

[0020] First, in the first molding step, the core 110 is inserted into a mold and fixed, and then molten resin is injected to mold the inner covering portion 120 integrally with the core 110 (FIG. 2 (B)). Next, in the second molding step, the molded product obtained in the first step, i.e., the inner covering portion 120 molded integrally with the core 110, is inserted into a mold and fixed, and then molten resin is injected to mold the outer covering portion 130 integrally with the inner covering portion 120 (FIG. 2 (C)). In this way, the case body 102 is formed by two-step insert molding and is composed of the inner covering portion 120 that covers the surface of the core 110 and the outer covering portion 130 that covers the surface of the inner covering portion 120.

[0021] Then, the circuit board 140, on which the connector 106 and the magnetic sensing element are mounted, is inserted through an opening provided in the top of the case body 102 and placed in the gap 112 of the core 110. The circuit board 140 is then positioned relative to the inner covering part 120 (FIG. 2 (D)), and the circuit board 140 is fixed to the outer covering part 130 with screws 160 (FIG. 2 (E)). Finally, the cover part 170 is fitted into the outer covering part 130 (FIG. 2 (F)), completing the current sensor 100. The latter assembly process will be described further below with reference to another drawing.

[0022] Next, a description will be given of the shapes and structures of the inner covering portion 120 and the outer covering portion 130 that constitute the case body 102. For ease of explanation, in the following figures, the inner covering portion 120 and the outer covering portion 130 are shown not as individual portions but as containing the core 110.

[0023] [Inner Covering Portion] Figures 3 to 5 show the inner covering portion 120. Figure 3 (A) is a perspective view from the upper right front, Figure 3 (B) is a perspective view from the lower left front, Figure 4 (A) is a plan view, Figure 4 (B) is a bottom view, Figure 4 (C) is a left side view, Figure 5 (A) is a front view, and Figure 5 (B) is an enlarged view of a portion of the inner circumferential surface. To make the opening in the inner covering portion 120 easier to see, in these figures, the core 110 exposed through the opening in the inner covering portion 120 is darkly shaded. Furthermore, since the back view is substantially the same as the plan view and the right side view is substantially the same as the left side view, the back view and the right side view are not shown.

[0024] 3A and 4A, a large opening 121 is provided in the upper part of the inner covering portion 120. The opening 121 is used when a circuit board is installed in the gap 112 of the core 110.

[0025] In the first molding stage, the core 110 inserted into the mold is pressed from the outside in the Y and Z directions, the position of the core 110 in the mold in the Y and Z directions is fixed, and then resin is injected to mold the inner covering portion 120, so that openings are formed at the positions pressed by the mold. As a result, in addition to the opening 121 for installing the circuit board described above, the inner covering portion 120 has two small rectangular openings 122 and two small circular openings 123 on each of the front and back surfaces as shown in Figures 3 and 5A, and four circular openings 123 on the bottom surface as shown in Figure 4B.

[0026] The positioning of the core 110 in the X direction within the mold is achieved simultaneously with the positioning in the Z direction by utilizing the gap 112 of the core 110, and since the core 110 is not pressed from the outside in the X direction, no openings are formed on the left and right sides of the inner covering portion 120, as shown in Fig. 4(C) . By fixing the position of the core 110 within the mold in this manner, the number of slide cores that make up the mold can be reduced, which reduces mold costs and also reduces the number of openings formed in the inner covering portion 120.

[0027] A plurality of protrusions are provided on the inner peripheral surface 124 of the inner covering portion 120. In other words, a plurality of protrusions protrude from the inner peripheral wall of the inner covering portion 120. Specifically, as shown in Fig. 3, three rectangular protrusions 125 protruding in a rectangular shape are provided at approximately equal intervals on each of the upper and lower surfaces of the inner peripheral surface 124, and one cross protrusion 126 protruding in a cross shape is provided on each of the left and right surfaces. As shown in Fig. 5(A), the protrusions 125, 126 provided on the inner peripheral surface 124 both have flat top surfaces and are the same height.

[0028] In the second molding stage, a part of the mold MD is inserted along the top surfaces of these protrusions 125, 126. This fixes the position of the inner covering portion 120 in the mold in the X and Z directions, eliminating the need to press and fix the inner covering portion 120 from the outside in the X and Z directions. This allows the mold to have a simple structure, reducing mold costs. Furthermore, the number of openings formed in the molded product obtained in the second stage, i.e., the outer covering portion 130, can be reduced.

[0029] In the second molding stage, resin for molding the outer covering part 130 is injected through gates GT facing the lower left and upper right parts of the front of the inner covering part 120 fixed to the mold (see (A) in FIG. 5). At this time, the inner covering part 120 may rotate due to the injection pressure of the resin, but the protrusions 125 and 126 provided on the inner circumferential surface 124 can reduce the effect of the injection pressure and prevent the inner covering part 120 from rotating.

[0030] More specifically, multiple rectangular protrusions 125 are provided on each of the upper and lower surfaces of the inner circumferential surface 124 due to ample space. By arranging multiple rectangular protrusions 125, each having a certain length, at a certain interval, rotation of the inner covering portion 120 around the X-axis, Y-axis, and Z-axis can be prevented. Meanwhile, one cross-shaped protrusion 126 is provided on each of the left and right surfaces of the inner circumferential surface 124 due to limited space. As shown in FIG. 5B , which is an enlarged view of the left side of the inner circumferential surface 124, the cross-shaped protrusion 126 has a portion 126y that extends a certain length in the Y-direction and a portion 126z that extends a certain length in the Z-direction. The presence of portion 126y prevents rotation of the inner covering portion 120 around the Y-axis, while the presence of portion 126z prevents rotation of the inner covering portion 120 around the Z-axis.

[0031] In the illustrated example, of the three rectangular protrusions 125 arranged side by side on each of the upper and lower faces of the inner circumferential surface 124, the one sandwiched between them is larger than the two on either side, but the size of each rectangular protrusion 125 can be changed as appropriate. Also, a plurality of rectangular protrusions 125 are arranged on each of the upper and lower faces of the inner circumferential surface 124, and one cross protrusion 126 is arranged on each of the left and right faces, but the shape and number of the protrusions can be changed as appropriate depending on the size of each face that makes up the inner circumferential surface.

[0032] [Outer Coating Portion] Figures 6 and 7 show the outer coating portion 130. Figure 6(A) is a perspective view from the upper right front, Figure 6(B) is a front view, Figure 6(C) is a rear view, Figure 7(A) is a plan view, Figure 7(B) is a bottom view, Figure 7(C) is a left side view, and Figure 7(D) is a right side view. To make the opening in the outer coating portion 130 easier to see, in these figures, the inner coating portion 120 exposed from the opening in the outer coating portion 130 is lightly shaded, and the core 110 is darkly shaded.

[0033] As shown in Figures 6A and 7A, an opening 131 for installing a circuit board is provided in the upper part of the outer covering part 130. The opening 131 is slightly larger than the opening 121 in the inner covering part 120, and the periphery of the opening 121 in the inner covering part 120 is exposed through the opening 131. Two fastening parts 132 are provided at positions sandwiching the opening 121 from the front and rear. Each fastening part 132 is connected to a protective part 133 extending upward from the center of the upper end of each of the front and rear wall parts of the outer covering part 130. As shown in Figures 7C and 7D, each fastening part 132 has a fastening hole 132a that penetrates in the X direction. The fastening hole 132a is used to screw the circuit board.

[0034] In the second molding stage, the inner covering part 120 integrated with the core 110 is inserted into the mold, and as described above, a part of the mold is inserted along the multiple protrusions 125, 126 provided on the inner peripheral surface 124 to fix the position of the inner covering part 120 in the X direction and the Z direction within the mold (in other words, the radial position of the hole penetrating the center of the inner covering part 120 = the position in the direction perpendicular to the central axis of the hole), and the inner covering part 120 is further pressed in the Y direction to fix the position of the inner covering part 120 in the mold in the Y direction, and then resin is injected to mold the outer covering part 130, so that an opening is formed at the position pressed by the mold.

[0035] As a result, the outer covering portion 130 has four small circular openings 134 on its front surface as shown in FIGS. 6A and 6B, and also has four circular openings 134 on its back surface as shown in FIG. 6C, but does not have any circular openings 134 on its bottom surface, left side surface, or right side surface (in other words, on the outer peripheral wall located in the radial direction of the hole that penetrates the center of the outer covering portion 130) as shown in FIGS. 7B to 7D.

[0036] 6 and 7 (B), the multiple rectangular openings 122 and circular openings 123 of the inner covering portion 120 are all filled in and covered by the outer covering portion 130. In other words, the multiple circular openings 134 in the outer covering portion 130 do not overlap the multiple rectangular openings 122 and circular openings 123 in the inner covering portion 120, but are formed at positions away from these openings 122, 123, and the outer covering portion 130 bites into and is in close contact with the openings 122, 123 provided in the inner covering portion 120. This indicates that when the position of the inner covering portion 120 is fixed within the mold in the second molding stage, the inner covering portion 120 is pressed down at a position away from the openings 122, 123.

[0037] 6A, the protrusions 125, 126 of the inner covering portion 120 are embedded in the inner peripheral wall 135 of the outer covering portion 130, with only the top surfaces of the protrusions 125, 126 exposed from the outer covering portion 130. In other words, the protrusions 125, 126 provided on the inner peripheral surface of the inner covering portion 120 bite into and adhere tightly to the inner peripheral wall 135 of the outer covering portion 130.

[0038] 8 shows a cross section of the core 110, the inner coating portion 120, and the outer coating portion 130. In FIG. 8(A), VIII in FIG. Ａ -VIII Ａ 8B is a cross-sectional view taken along line VIII in FIG. Ｂ -VIII Ｂ FIG.

[0039] As shown in Figure 8 (A), the protrusions 125, 126 provided on the inner circumferential surface 124 of the inner covering portion 120 (protruding from the inner circumferential wall 127) bite into and adhere closely to the inner circumferential wall 135 of the outer covering portion 130, so that the inner circumferential wall 135 and the protrusions 125, 126 are flush with each other. Also, as shown in Figures 8 (A) and (B), there are no gaps between the core 110 and the inner covering portion 120, or between the inner covering portion 120 and the outer covering portion 130. In this way, by forming each part of the case body that houses the core by insert molding, the core and the case body can be adhered to each other, and variation in the position of the core 110 relative to the case body can be reduced.

[0040] 9 is an exploded perspective view of the current sensor 100. As shown in Fig. 9(A), an IC 150 (e.g., a Hall IC) incorporating a magnetic sensing element is mounted on a front surface 140a of the circuit board 140, and a connector 106 for receiving an external connector is mounted on a back surface 140b.

[0041] The circuit board 140 is inserted into the gap 112 of the core 110, and is positioned by abutting the back surface 140b and side surfaces of the circuit board 140 with the positioning groove 121a in the opening 121 formed in the inner covering portion 120. A step is provided between the edge of the opening 121 in the inner covering portion 120 and the edge of the opening 131 in the outer covering portion 130, so that only the inner covering portion 120 is involved in the positioning, and the outer covering portion 130 does not interfere. By positioning the circuit board 140 relative to the inner covering portion 120, which is molded integrally with the core 110 in this way, it is possible to further reduce variation in the position of the magnetic sensing element relative to the core 110.

[0042] 9B, screws 160 are fastened to the fastening holes 132a to fix the circuit board 140 to the outer covering part 130. Finally, the cover part 170 is placed over the circuit board 140, fitted into the protective part 133, and fixed to the outer covering part 130.

[0043] [Ensuring Creepage Distance] Fig. 10 is a diagram illustrating the insulation distance in the current sensor 100. Fig. 10A is an enlarged plan view of the lower part of the current sensor 100.

[0044] When a current to be detected flows through a primary conductor (not shown) inserted through through hole 104 of current sensor 100, a magnetic field generated around the primary conductor is converged on core 110. In current sensor 100, the creepage distance is the shortest distance along the insulator between the primary conductor and core 110, i.e., the shortest distance along inner covering 120 and outer covering 130 from through hole 104 to core 110.

[0045] (B) in Figure 10 is a cross-sectional view (cross-sectional view along line X-X) of the current sensor 100 cut at a position passing through circular opening 134 (hereinafter may be referred to as the "outer opening 134"), which is the opening of the outer covering portion 130 that is closest to the through hole 104, and circular opening 123 (hereinafter may be referred to as the "inner opening 123"), which is the opening of the inner covering portion 120 that is closest to the outer opening 134.

[0046] As described above, the outer opening 134 is formed at a position that does not overlap with the inner opening 123, and therefore there is no portion of the core 110 that is directly exposed to the outside. As shown in Fig. 10 (A), the outer opening 134 is separated from the through hole 104 by a distance L1. Furthermore, when traveling from the outer opening 134 to the core 110 along the interface between the outer covering portion 130 and the inner covering portion 120, as shown in Fig. 10 (B), the shortest path is from point a, the outermost end of the outer opening 134, via point b, the innermost end of the outer opening 134 and point c, the outermost end of the inner opening 123, to point d, the innermost end of the inner opening 123.

[0047] Therefore, the sum of the distance L1 from the through hole 104 to the outer opening 134, the depth L2 of the outer opening 134 (the thickness of the outer covering portion 130), the distance L3 from the outer opening 134 to the inner opening 123, and the depth L4 of the inner opening 123 (the thickness of the inner covering portion 120) is the creepage distance CD in the current sensor 100. If the path of the creepage distance CD were shown as a continuous line, it would look like the thick line in Figure 10 (C).

[0048] Comparison with First Comparative Example FIG. 11 shows a current sensor 200' as a first comparative example. (A) in FIG. 11 is an enlarged plan view of the lower portion of the current sensor 200'. The case body 220' of the current sensor 200' has a similar appearance to the case body 102 of the above-described embodiment. However, because it is obtained by a single insert molding process, the core 110' is exposed through each opening 222' formed at the mold press position. The distance L1' from the opening 222' in the case body 220' to the through hole 204' is the same as the distance L1 from the outer opening 134 to the through hole 104 in the case body 102. The thickness L2' of the case body 220' is the same as that of the case body 102, i.e., the sum of the thickness L2 of the outer covering portion 130 and the thickness L4 of the inner covering portion 120.

[0049] 11B is a longitudinal cross-sectional view (cross-sectional view taken along line XI-XI) of the current sensor 200' taken through the opening 222' of the case body 220', which is the opening closest to the through-hole 204'. In the current sensor 200', the creepage distance CD' is the sum of the distance L1' from the through-hole 204' to the opening 222' and the depth L2' of the opening 222' (the thickness of the case body 220'). As described above, in the current sensor 200', the core 110' is exposed through the opening formed in the case body 220', making it difficult to ensure a sufficient creepage distance.

[0050] In contrast, in the current sensor 100 of the above-described embodiment, the case body 102 has a two-layer structure in which the inner covering portion 120 and the outer covering portion 130 are integrated, and the outer opening 134 is formed at a position away from the inner opening 123. Therefore, it is possible to ensure an insulation distance longer than that of the current sensor 200′ of the first comparative example by the distance L3 connecting the outer opening 134 and the inner opening 123.

[0051] Comparison with Second Comparative Example Fig. 12 shows a current sensor 300' as a second comparative example. For ease of explanation, only the core and case body of the current sensor 300' are shown. Fig. 12A is an exploded perspective view showing a simplified structure of the case body, and Fig. 12B is a cross-sectional view taken along line XII-XII.

[0052] As shown in Figure 12 (A), in the current sensor 300', the case body is composed of a housing section 320' that houses a core 310' and a lid section 330' that covers the housing section 320'. Since there are individual differences in dimensions for any component, clearance is necessary in the space for housing the component. Therefore, a space slightly larger than the dimensions of the core 310' is provided inside the housing section 320', and a space slightly larger than the dimensions of the housing section 320' is provided inside the lid section 330'.

[0053] Specifically, as shown in FIG. 12B, the current sensor 300' has clearances at at least eight locations in the vertical direction and at least four locations in the front-to-rear direction. Although not shown, there are also clearances at least eight locations in the left-to-right direction. The presence of such clearances can cause variations in the position of the core relative to the case body and the position of the magnetic sensing element relative to the core. In addition to the clearances, the current sensor 300' also requires a structure for fixing the components.

[0054] In contrast, in the current sensor 100 of the above-described embodiment, the core 110, the inner covering portion 120, and the outer covering portion 130 are integrally provided, so that neither clearance nor a structure for fixing the components is required, thereby making it possible to reduce the size of the case body and, in turn, the current sensor 100. Furthermore, because the core 110 is in close contact with the case body, variation in the position of the core is reduced, and therefore variation in the position of the magnetic sensing element relative to the core 110 can also be reduced, making it possible to stabilize the performance of the current sensor 100.

[0055] The current sensor 100 of the above-described embodiment has the following advantages.

[0056] (1) The case body 102 that houses the core 110 is composed of an inner covering portion 120 and an outer covering portion 130, and the openings 122, 123 (inner openings) formed in the wall of the inner covering portion 120 and the opening 134 (outer opening) formed in the wall of the outer covering portion 130 are spaced apart, and the core 110 is not exposed from the outer opening. Therefore, compared to a case where the case body is formed by simple insert molding and the core is exposed from an opening formed in the wall of the case body, a longer creepage distance can be ensured by the distance from the outer opening to the inner opening, making it possible to sufficiently ensure insulation performance and guarantee high withstand voltage.

[0057] (2) The inner peripheral surface 124 of the inner covering portion 120 is provided with a plurality of rectangular protrusions 125 and cross protrusions 126. When the outer covering portion 130 is integrally molded with the inner covering portion 120, a part of the mold is inserted along these protrusions 125, 126, thereby fixing the position of the inner covering portion 120 in the X direction and Z direction within the mold. This eliminates the need to press and fix the inner covering portion 120 from the outside in the X direction and Z direction. This allows the mold to have a simple structure, reducing mold costs and enabling the number of openings formed in the outer covering portion 130 to be reduced.

[0058] (3) The two-stage insert molding allows the core 110, the inner covering portion 120, and the outer covering portion 130 to be integrally formed and adhered to each other, thereby improving the accuracy of the position of the core 110 relative to the case body.

[0059] (4) Since the circuit board 140 on which the magnetic sensing element is mounted is positioned relative to the inner covering portion 120 which is integrally molded with the core 110, the accuracy of the position of the magnetic sensing element relative to the core 110 can be further improved, and the performance of the current sensor 100 can be stabilized.

[0060] (5) The core 110, the inner covering portion 120, and the outer covering portion 130 are integrated and adhered to each other by the two-stage insert molding. This eliminates the need to provide clearances or the like inside the case body, as is the case when the core is housed in a case body consisting of a housing portion and a lid portion that are manufactured separately. This allows the current sensor 100 to be made smaller.

[0061] The present invention is not limited to the above-described embodiment and modifications, and can be implemented in various modified forms.

[0062] Although the core 110 has a substantially rectangular ring shape when viewed including the gap 112, the shape of the core is not limited to this and may be, for example, a substantially circular ring or another ring shape. In other words, the core may have any shape as long as a gap is formed midway along the ring-shaped magnetic path that converges the magnetic field generated by the conduction of the current to be detected.

[0063] Although the inner covering portion 120 and the outer covering portion 130 are made of resin, the material of the case body is not limited to resin as long as it is an insulating material.

[0064] By two-stage insert molding, the inner covering portion 120 is molded integrally with the core 110, and the outer covering portion 130 is molded integrally with the inner covering portion 120, so that the core 110, the inner covering portion 120, and the outer covering portion 130 are in close contact with each other. However, if technically possible, two case bodies having shapes similar to the inner covering portion 120 and the outer covering portion 130 described above may be produced by a method other than insert molding, and the core and these two case bodies may be in close contact with each other.

[0065] Furthermore, the structures illustrated in the embodiments are merely preferred examples, and it goes without saying that the present invention can be suitably implemented by adding various elements to the basic structure or by substituting parts thereof.

[0066] Providing technology to ensure long creepage distances.

[0067] REFERENCE SIGNS LIST 100 Current sensor (current detector) 110 Core (magnetic core) 112 Gap 120 Inner covering portion 121 Circuit board installation opening (first inner opening) 122 Rectangular opening (second inner opening) 123 Circular opening (second inner opening) 124 Inner peripheral surface 125 Rectangular protrusion (protrusion) 126 Cross protrusion (protrusion) 127 Inner peripheral wall (inner inner peripheral wall) 130 Outer covering portion 131 Circuit board installation opening (first outer opening) 134 Circular opening (second outer opening) 135 Inner peripheral wall (outer inner peripheral wall)

Claims

1. A current detector comprising: a magnetic core having a gap formed in the middle of a ring-shaped magnetic path that converges a magnetic field generated by the conduction of a current to be detected; an inner covering part covering a surface of the magnetic core and having a first inner opening formed corresponding to the gap and a plurality of second inner openings different from the first inner opening; and an outer covering part covering a surface of the inner covering part and biting into the second inner opening, having a first outer opening formed corresponding to the first inner opening and a plurality of second outer openings different from the first outer openings that are formed in a position not overlapping with the second inner opening.

2. A current detector as claimed in claim 1, wherein the inner covering portion has a plurality of protrusions on the inner circumferential wall surface surrounding a hole penetrating through the centre thereof, and the outer covering portion has an outer inner circumferential wall surrounding a hole penetrating through the centre thereof that is embedded into the protrusions.

3. A current detector as claimed in claim 2, characterized in that the second outer opening is not formed in the outer peripheral wall of the outer covering portion located in the radial direction of the hole passing through the centre of the outer covering portion.

4. A current detector as claimed in claim 2, characterized in that the outer inner peripheral wall of the outer covering portion is flush with and continuous with the projection.

5. A current detector as claimed in any one of claims 1 to 4, further comprising a circuit board on which a magnetic sensing element is mounted and which is disposed within the gap, and wherein the inner covering portion has a portion for determining the position of the circuit board inside the first inner opening.

6. A current detector as claimed in claim 5, characterized in that the outer covering portion is formed so that the first outer opening is larger than the first inner opening and surrounds the first inner opening.

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