Current detector

Abstract

To provide a current detector which suppresses gap dimension change of a magnetic body core accompanying short-term temperature change and long-term changes due to aging, and suppresses change of output characteristics accompanying the same.SOLUTION: A current detector includes a resin case 220, wherein a magnetic body core 110 having a gap 112 is stored in the resin case 220, and a magnetic detection element used in detection of measured current is arranged in the gap 112. The resin case 220 and the magnetic body core 110 include a regulation member 260 for bonding and fixing them, the regulation member 260 is arranged at a position at 180 degrees relevant to the gap 112 between the resin case 220 and the magnetic body core 110 in a range of an F dimension in a core straight line part, and has groove parts 226a and 226b for storing the regulation member 260 at the right and left of a regulation member coating position 227.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present invention relates to a current detector that detects a current by arranging a magnetic detection element such as a Hall element in a gap of a magnetic core.

Background Art

[0002] In a conventional current detector (current sensor), in use in an environment where a large temperature change occurs, due to expansion or contraction caused by a temperature change of a filler that encapsulates a magnetic core or a Hall element, the gap width of the magnetic core fluctuates and the detection output of the Hall element fluctuates. As a countermeasure, a resin case (a resin case with a small dimensional change due to a temperature change) and a magnetic core are fixed using an adhesive at a position within a range from the gap of the annular magnetic core to 90 degrees, thereby suppressing the gap fluctuation of the magnetic core (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For example, Patent Document 1 states that resin cases are resistant to deformation due to temperature changes. However, in the case of resin cases made from commonly used crystalline resins, such as PBT (polybutylene terephthalate), if the operating environment temperature of the current detector using the resin case is higher than the mold temperature during molding, there is a problem that the crystallization of PBT is promoted, causing dimensional changes. To minimize dimensional changes due to temperature changes, it is necessary to raise the temperature to above the glass transition temperature and to the operating environment temperature of the current detector. However, this additional heating step increases the working time (for example, 100°C and 1.5 hours are required for resin cases using PBT) and increases costs. Furthermore, even with the above measures, it is not possible to completely suppress deformation of the resin case due to temperature changes.

[0005] If resin cases with insufficient crystallization or residual stress are used to reduce costs or shorten working time, the resin cases will expand or contract significantly due to temperature changes. The magnetic cores bonded to the resin cases with adhesive within a range of up to 90 degrees from the gap (close to the magnetic core gap) will also fluctuate similarly, resulting in changes in the dimensions of the magnetic core gap. In this case, the change in gap dimensions will cause a change in the magnetic flux density within the gap, affecting the output characteristics of Hall elements and other components. This is true not only for expansion and contraction of the resin cases due to short-term temperature changes, but also when dimensional changes occur in the resin cases due to aging.

[0006] The present invention aims to provide a current detector that suppresses changes in the gap dimensions of the magnetic core due to short-term temperature changes and long-term aging, and suppresses the resulting changes in output characteristics, without using a resin case heated to above the glass transition temperature and up to the operating temperature of the current detector. [Means for solving the problem]

[0007] The current detector of the present invention has a gap formed in a substantially rectangular magnetic core that collects the magnetic flux generated by the current to be measured, a magnetic detection element is placed within the gap of the magnetic core, and the magnetic core and magnetic detection element are housed in a resin case. The magnetic core has an inner circumferential straight section that is approximately straight from a position 180 degrees circumferentially from the center of the gap, at a predetermined angle to the inner circumference. The device includes a regulating member for bonding the magnetic core and the resin case. The bonding area between the magnetic core and the resin case by the regulating member does not exist within a 90-degree range in the circumferential direction relative to the gap center, based on the angle at the center of the magnetic core, but rather from a position 180 degrees circumferentially relative to the gap center. The aforementioned inner circumferential straight portion It is within the range of [the specified range]. [Effects of the Invention]

[0008] According to the present invention, from a position 180 degrees circumferentially with respect to the center of the gap The aforementioned inner circumferential straight portion By bonding the magnetic core to the resin case within this range, it is possible to suppress changes in the gap dimension of the magnetic core due to short-term or long-term dimensional changes of the resin case, and thereby suppress changes in the output characteristics of the current detector. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view showing a current detector in Embodiment 1 of the present invention. [Figure 2] This figure shows the position of the regulating member for the magnetic core inside the resin case in Embodiment 1 of the present invention. [Figure 3] This is a cross-sectional view along line II in Figure 2, in Embodiment 1 of the present invention. [Figure 4] This figure shows the state in which the magnetic core is restricted by a restricting member within the resin case in Embodiment 1 of the present invention. [Figure 5] This is a cross-sectional view along line II-II in Figure 4, according to Embodiment 1 of the present invention. [Figure 6] This is a cross-sectional view along line III-III in Figure 4, according to Embodiment 1 of the present invention. [Figure 7]It is a diagram showing a state in which a magnetic core is regulated by a regulating member within a resin case in a conventional example. [Figure 8] It is a cross-sectional view taken along line IV-IV in FIG. 7 in a conventional example. [Figure 9] It is a cross-sectional view taken along line V-V in FIG. 7 in a conventional example. [Figure 10] It shows a table and a graph presenting the results of simulating the change in magnetic flux of a detection element unit in a conventional example and in Embodiment 1. [Figure 11] It is a diagram showing a state in which the range of the application position of a regulating member in Embodiment 1 of the present invention is expanded. [Figure 12] It is a cross-sectional view taken along line VI-VI in FIG. 11 in Embodiment 1 of the present invention. [Figure 13] It is a table showing the results of simulating the change in magnetic flux of a detection element unit when the range of the application position of a regulating member in Embodiment 1 is expanded. [Figure 14] It is a table showing the results of simulating the peeling stress in Embodiment 1 of the present invention. [Figure 15] It is a cross-sectional view showing another shape for limiting the range of the application position of a regulating member in Embodiment 1. [Figure 16] It is a perspective view showing a current detector in Embodiment 2 of the present invention. [Figure 17] It is a diagram showing a state in which a magnetic core is regulated by a regulating member within a resin case in Embodiment 2 of the present invention. [Figure 18] It is a cross-sectional view taken along line VII-VII in FIG. 17 in Embodiment 2 of the present invention. [Figure 19] It is a cross-sectional view showing an example of a structure for increasing the adhesion strength between a magnetic core and a resin case in Embodiment 2 of the present invention. [Figure 20] It is a cross-sectional view used for simulating the peeling stress of a structure with increased adhesion strength between a magnetic core and a resin case in Embodiment 2 of the present invention. [Figure 21] It is a table showing the results of simulating the peeling stress in Embodiment 2.

Best Mode for Carrying Out the Invention

[0010] Embodiment 1. FIG. 1 is a perspective view showing the current detector 100 in Embodiment 1 of the present invention disassembled into components. The current detector 100 includes a resin case 120 made of, for example, PBT resin. In the core housing portion 121 of the resin case 120, a magnetic core 110 having an annular or rectangular shape with R at the corners is housed. This magnetic core 110 having an annular or rectangular shape with R at the corners has a gap 112 at one location in the circumferential direction. The magnetic core 110 is, for example, a laminated core plate having an outer shape with a gap 112 formed by punching a flat plate such as an electromagnetic steel sheet with a press mold, or a magnetic core 110 provided with a gap 112 in a spiral-wound electromagnetic steel sheet or the like. The magnetic core 110 is adhesively fixed to the core housing portion 121, and is not filled and fixed with a conventionally used filler or the like.

[0011] The resin case 120 has an insertion hole 122 for passing a primary conductor (not shown) through which a measured current flows. The core housing portion 121 has an opening on one surface (the surface on the arrow A side in FIG. 1) in the primary conductor insertion direction, and the other surface forms a closed container shape. Further, a circuit board housing portion is formed in the resin case 120, and a circuit board portion 130 is to be housed in the circuit board housing portion 123. Also, by fitting a resin cover or the like (not shown) to the opened surface of the resin case 120, all directions may be closed. Further, the resin case 120 has an inner peripheral wall 124 around the insertion hole 122 for passing the primary conductor. When the magnetic core 110 is housed in the core housing portion 121 of the resin case 120, the resin case 120 has an outer peripheral wall 125 so as to surround the outer periphery of the magnetic core 110. Also, the inner peripheral wall 124 and the outer peripheral wall 125 have a shape along the shape of the magnetic core 110 having an annular or rectangular shape with R at the corners.

[0012] The circuit board section 130 is equipped with, for example, magnetic detection elements 140 such as Hall elements, other electronic components (not shown), and connector terminals for sending output to the outside. The magnetic core 110 is housed in the core housing section 121 of the resin case 120, and the magnetic detection elements 140 are assembled to the resin case 120 so that they are positioned within the gap 112 of the magnetic core 110. The assembly method is not limited to screw fixing or press-fitting.

[0013] This section describes the method for bonding the magnetic core 110 and the resin case 120. Figure 2 is a view of the resin case 120 from the direction of arrow A in Figure 1, showing the state in which a restricting member 160, which is an adhesive made of, for example, a silicone-based resin, has been applied to the resin case 120 as a preliminary step before housing and bonding the magnetic core 110 to the core housing portion 121 of the resin case 120. Figure 3 is a cross-sectional view along II in Figure 2, in which there is a restricting member application position 127 with a predetermined area on the central bottom surface, and grooves 126a and 126b with predetermined depth and width are located between the inner circumferential wall 124 and the outer circumferential wall 125 (see Figure 2) on the left and right sides of the restricting member application position 127. The restricting member 160 is applied to the restricting member application position 127.

[0014] Figure 4 is a view from the direction of arrow A in Figure 1, showing the magnetic core 110 inserted into the core housing section 121 of the resin case 120 coated with the restricting member 160, and the magnetic core 110 being bonded by the restricting member 160.

[0015] As shown in Figure 4, the regulating member 160 is positioned at an angle at the center of the magnetic core 110, within a predetermined angle range (away from the gap 112) from a position 180 degrees circumferentially with respect to the center of the gap 112.

[0016] Figure 5 is a cross-sectional view along the line II-II in Figure 4. The regulating member 160, which has flowed when the magnetic core 110 is pressed downwards, is stored in grooves 126a and 126b, and the regulating member 160 adheres the magnetic core 110 and the resin case 120 within the regulating member application position 127.

[0017] Figure 6 is a cross-sectional view taken along the line III-III in Figure 4. Here, 114a and 114b in Figure 6 represent the space between the magnetic core 110 and the outer peripheral wall 125, while 115a and 115b in Figure 4 represent the space between the magnetic core 110 and the inner peripheral wall 124. These spaces are clearances provided so that the two do not come into contact at the operating ambient temperature, taking into account the coefficients of thermal expansion and dimensional accuracy of the resin case 120 and the magnetic core 110. As shown in Figures 4, 5, and 6, it is desirable that the resin case 120 and the magnetic core 110 do not come into contact in direction B where the width dimension of the gap 112 changes, except at the regulating member application position 127.

[0018] In the current detector 100 configured in this way, the magnetic flux generated by conducting the current to be measured through the primary conductor is collected by the magnetic core 110, and a magnetic detection element 140 mounted on the circuit board 130 and positioned in the gap 112 is used to output a voltage corresponding to the magnetic flux density in the gap 112. This output is amplified to a predetermined level and output to the outside of the current detector 100 via a connector (not shown) on the circuit board 130.

[0019] In the operating environment of the current detector 100, temperature changes cause the resin case 120 to repeatedly expand and contract. At this time, a force acts on the magnetic core 110, which is bonded to the resin case 120 via the restricting member 160, causing it to deform in the direction of the expansion and contraction of the resin case 120.

[0020] In this embodiment, the regulating member 160 is applied within a predetermined angle range from the regulating member application position 127 in Figure 2, that is, from a position 180 degrees from the gap 112 of the magnetic core 110. Spaces 114a and 114b (see Figure 6) are provided between the magnetic core 110 and the outer peripheral wall 125 of the resin case 120, and spaces 115a and 115b (see Figure 4) are provided between it and the inner peripheral wall 124. As a result, the gap 112 is not constrained in the direction of expansion and contraction of the resin case 120 indicated by arrow B in Figure 6. Consequently, the expansion and contraction of the resin case 120 only affects the regulating member application position 127 in the direction in which the width dimension of the gap 112 changes, that is, it is only affected by the linear expansion coefficient of the magnetic core 110. The linear expansion coefficient of the magnetic core 110 is minimal (for example, 1.2 × 10⁻⁶ in the case of electrical steel sheet). -5 When the temperature is / K and the dimension of the gap 112 is 2 mm, the change is 0.024 μm for a temperature change of 100°C. Therefore, the change in the width dimension of the gap 112 of the magnetic core 110 can be suppressed, and the change in the output of the magnetic detection element 140 can be suppressed.

[0021] Here, for comparison, we will describe a conventional example, that is, the case in which the regulating member 160 is applied near the gap 112 of the magnetic core 110. Figure 7 shows the magnetic core 110 and the resin case 120 bonded together using the regulating member 160 at the position of the upper half of the left arm 113a and the right arm 113b of the magnetic core 110, that is, within a 90-degree range from the gap 112.

[0022] Figure 8 is a cross-sectional view along the line IV-IV in Figure 7. Arrow C in the figure indicates the direction in which the width dimension of the gap 112 changes. Since the area including the arms 113a and 113b is fixed to the resin case 120 by the regulating member 160, the resin case 120 expands and contracts in the direction of arrow C, causing the magnetic core 110, which is bonded using the regulating member 160, to undergo the same dimensional changes as the resin case 120. This also causes a change in the width dimension of the gap 112 in the magnetic core 110, and the output of the magnetic detection element 140 changes as well.

[0023] Figure 9 is a cross-sectional view along the VV line in Figure 7. Due to the expansion and contraction of the resin case 120, the arms 113a and 113b of the magnetic core 110, which are bonded to the resin case 120 by the regulating member 160, change in size in the direction of arrow D. Consequently, the gap 112 changes in size in the direction of arrow D, and the output of the magnetic detection element 140 also changes.

[0024] Here, we will use simulation to verify the dimensional change of the gap 112 in the conventional example and in this embodiment 1, that is, the change in the detection output of the magnetic detection element 140. In the simulation, we will use static structural analysis to check the rate of change of the magnetic flux density within the gap 112 from the dimensional change of the gap 112 when the ambient temperature of the current detector is changed from 25°C to 85°C, 105°C, and 125°C. First, the simulation conditions for the conventional example will be explained using Figures 7 and 8. The dimensions of the magnetic core 110 are a=2mm, b=17mm, c=30mm as shown in Figure 7, and d=5mm as shown in Figure 8. The bonding position is in the range from gap 112 to 90 degrees, and the typical values ​​of the linear expansion coefficients of the various materials are as follows. Resin case 120...PBT resin: 6.15 x 10 -5 / K Regulating member 160... Silicone resin: 12 x 10 -5 / K Magnetic core 110... Electrical steel sheet: 1.2 x 10 -5 / K

[0025] The simulation results are shown in a table in Figure 10(a). As shown in Figure 10(a), when the ambient temperature of the conventional current detector is changed from 25°C to 125°C, the dimensional change of the gap 112 is 46.2 μm, and as a result, the change in magnetic flux density within the gap 112 detected by the magnetic detection element 140 is -2.31%. The dashed line in Figure 10(c) is a graph of this. It can be seen that as the resin case 120 expands in a direction that changes the width of the gap 112 in a high-temperature environment, the width dimension of the gap 112 of the magnetic core 110 increases, and the detection output of the magnetic detection element 140 decreases.

[0026] Next, the simulation conditions for Embodiment 1 will be explained using Figures 4 and 5. The dimensions of the magnetic core 110 are the same as in the conventional example, with a=2mm, b=17mm, c=30mm shown in Figure 4, and d=5mm shown in Figure 5. In Figure 4, the bonding position is the regulating member coating position 127 (e=5mm), and the typical values ​​of the linear expansion coefficients of the various materials are the same as those in the simulation conditions for the conventional example described above. The simulation results are shown in a table in Figure 10(b). As shown in Figure 10(b), when the ambient temperature of the current detector 100 in Embodiment 1 is changed from 25°C to 125°C, the dimensional change of the gap 112 is 1.8 μm, and as a result, the change in magnetic flux density within the gap 112 detected by the magnetic detection element 140 is -0.09%. The solid line in Figure 10(c) is a graph of this. The influence of the resin case 120 expanding in the direction that changes the width of the gap 112 in a high-temperature environment on the direction in which the width of the gap 112 changes at the regulating member coating position 127 is minimal, as shown in Figure 10(c), and it can be seen that the change in the width dimension of the gap 112 of the magnetic core 110 is suppressed, and the change in the detection output of the magnetic detection element 140 is suppressed. Based on the above, by bonding and fixing the magnetic core 110 to the resin case 120 using the restricting member 160 within a predetermined angle range from a position 180 degrees relative to the gap 112, it is possible to suppress changes in the output of the magnetic detection element 140 even if the resin case 120 changes dimensions due to expansion and contraction.

[0027] Here, we simulate and verify the changes in the dimensions of the gap 112 and the detection output of the magnetic detection element 140 when the area of ​​the regulating member coating position 127 in this embodiment 1 is enlarged. Figures 11 and 12 show an enlarged view of the area of ​​the regulating member coating position 127 in Figures 4 and 5. The grooves 226a, 226b, and regulating member coating position 227 of the resin case 220 correspond to the grooves 126a, 126b, and regulating member coating position 127 in Figures 4 and 5. The grooves 226a and 226b are arranged such that the dimension g shown in Figure 12 falls within the range of dimension f, which is the straight inner circumference portion of the core (the straight inner circumference portion of the magnetic core 110) shown in Figure 11. In the simulation, the dimensions of the magnetic core 110 were the same as in the previous simulation (dimensions a=2mm, b=17mm, c=30mm, d=5mm shown in Figures 4 and 5), with the inner circumference straight section f=20mm, and the g dimension shown in Figure 12 being 10mm, 15mm, 20mm (dimension of the inner circumference straight section f), and 30mm (dimension to the outer circumference wall 225 of the core). The dimensional changes of the gap 112 and the changes in the detection output of the magnetic detection element 140 were verified when the ambient temperature was changed from 25°C to 125°C.

[0028] As shown in Figure 13, the simulation results were as follows: when g dimension was 10 mm, the gap dimension change was 0.2 μm and the magnetic flux density change rate was -0.01%; when g dimension was 15 mm, the gap dimension change was 2 μm and the magnetic flux density change rate was -0.1%; when g dimension was 20 mm, the gap dimension change was 3.2 μm and the magnetic flux density change rate was -0.16%; and when g dimension was 30 mm, the gap dimension change was 20 μm and the magnetic flux density change rate was -1%. In other words, if g dimension is within the range of f=20 mm, which is the straight inner circumference of the core shown in Figure 11, even if the bonding range by the restricting member 260 is expanded, the dimensional change of the gap 112 of the magnetic core 110 is small and the magnetic flux density change rate is also small, so the change in the detection output of the magnetic detection element 140 is small. However, when it exceeds the f dimension, the gap dimension change is large and the magnetic flux density change rate is also large, so the change in the detection output of the magnetic detection element 140 is large. Therefore, by keeping the bonding position within the range up to dimension f, which is the straight inner circumference of the core as shown in Figure 11, changes in the width dimension of the gap 112 can be suppressed, changes in the output of the magnetic detection element 140 can be suppressed, the coating area of ​​the regulating member 260 can be increased, and the bonding strength (strength against peeling) between the magnetic core 110 and the resin case 220 can be strengthened.

[0029] Here, we will use simulation to verify the strength of the magnetic core 110 against delamination when it is pulled. In the simulation, the magnetic core 110 is bonded to the resin case 220, and the stress on the restricting member 260 when the magnetic core 110 is pulled in the opposite direction to the bonding direction is confirmed by static structural analysis. The simulation conditions are shown in Figure 12, and the results are shown in Figure 14. In Figure 12, the dimensions of the magnetic core 110 are the same as in the previous simulation (dimensions a=2mm, b=17mm, c=30mm, d=5mm shown in Figures 4 and 5), and the symbol g indicates the distance between grooves 226c and 226d. For example, when the symbol g is 4.5mm, 9mm, and 12mm, the average value of the stress generated on the restricting member 260 when the magnetic core 110 is pulled with a force of 100N in the upward direction (arrow F direction) shown in Figure 12, and the reduction rate based on g=4.5mm are shown in Figure 14. As shown in the figure, the stress on the restricting member 260 is 7.6 MPa when g = 4.5 mm and 3.3 MPa when g = 9 mm. By changing the g dimension from 4.5 mm to 9 mm, the stress on the restricting member can be reduced by approximately 56.6%. When g = 12 mm, the stress is 2.8 MPa, and by changing the g dimension from 4.5 mm to 12 mm, the stress on the restricting member can be reduced by 63.2%. As shown in the simulation results above, by increasing the contact area of ​​the restricting member 260 that adheres the resin case 220 and the magnetic core 110, the force acting in the direction of peeling off the magnetic core 110 can be made to be less than or equal to the tensile allowable strength of the restricting member 260, thereby ensuring the necessary peel strength.

[0030] In this embodiment, a rectangular magnetic core having a considerable length (e.g., 20 mm) of the inner circumferential straight portion (indicated by symbol f in Figure 11) was described as an example. However, even when the magnetic core is annular or otherwise has a shorter inner circumferential straight portion, as the coating area is increased, the change in the width dimension of the gap that causes the output change of the magnetic detection element increases, and the adhesive strength between the magnetic core and the resin case is strengthened. Therefore, the appropriate coating area of ​​the regulating member should be set based on the change in the width dimension of the gap that results in an acceptable change in the output of the magnetic detection element and the acceptable adhesive strength.

[0031] In this embodiment, the configuration is not limited to the above-described form. For example, the shape of the magnetic core 110 may be a square or rectangle with gaps and no rounded corners. There may be three or more grooves 126a and 126b for storing the regulating member 160. For example, as shown in Figure 15, instead of grooves 126a and 126b, inclined 128a and 128b (inclined downward from the left and right ends of the regulating member application position 127 toward the outer peripheral wall 125) may be provided. Furthermore, the values ​​of the coefficients of linear expansion of the various materials used, such as the resin case 120 and the regulating member 160, are examples only and can be appropriately changed depending on the materials used.

[0032] Embodiment 2. In Embodiment 1, the magnetic core 110 was housed in the insertion hole 122 of the resin case 120 in the direction in which the primary conductor was inserted. Here, however, we will describe a configuration in which the magnetic core is housed in a direction 90 degrees from the primary conductor insertion direction.

[0033] Figure 16 is a perspective view showing the current detector 300 in Embodiment 2 of the present invention, disassembled into its components. The current detector 300 includes a resin case 320 made of, for example, PBT resin, and a U-shaped or rectangular magnetic core 310 with rounded corners is housed in the core housing section 321 of the resin case 320. The magnetic core 310 has a gap 312 at one location in the circumferential direction. The magnetic core 310 may be made by laminating core plates, each having an outer shape with a gap 312 formed by punching out a flat plate such as an electromagnetic steel sheet with a press die, or by providing a gap 312 in a spiral-shaped electromagnetic steel sheet. The magnetic core 310 is adhesively fixed to the core housing section 321, and conventional filling and fixing methods such as fillers are not used.

[0034] The resin case 320 has an insertion section 322 for passing through a primary conductor (not shown) through which the current to be measured flows. The core housing section 321 has an open side (the side indicated by arrow E in Figure 16) perpendicular to the primary conductor insertion direction, and the other side is closed, forming a container shape. Furthermore, a circuit board housing section 323 is formed inside the resin case 320, and the circuit board section 330 is housed in the circuit board housing section 323. Alternatively, the open side of the resin case 320 may be closed by fitting a resin cover or the like (not shown). Furthermore, when the magnetic core 310 is housed in the core housing section 321 of the resin case 320, there is an outer peripheral wall 325 surrounding the outer circumference of the magnetic core 310.

[0035] The circuit board section 330 is equipped with, for example, a magnetic detection element 340 such as a Hall element, other electronic components (not shown), and connector terminals for sending output to the outside. The magnetic core 310 is housed in the core housing section 321 of the resin case 320, and the magnetic detection element 340 is assembled to the resin case 320 so that it is positioned within the gap 312 of the magnetic core 310. The assembly method is not limited to screw fixing or press-fitting.

[0036] This section describes the method for bonding the magnetic core 310 and the resin case 320. Figure 17 is a view from the direction of arrow E in Figure 16, showing the state in which the magnetic core 310 is inserted into the resin case 320 to which a restricting member 360, which is an adhesive made of, for example, a silicone-based resin, has been applied, and the magnetic core 310 is bonded by the restricting member 360.

[0037] Figure 18 is a cross-sectional view taken along the line VII-VII in Figure 17. When the magnetic core 310 is placed in the core housing portion 321 of the resin case 320, the regulating member 360 is applied to the area where the resin case 320 comes into contact with the core bottom surface (indicated by the symbol h in Figure 18, the straight outer circumference between the left and right corner R endpoints on the bottom surface side of the magnetic core, hereafter referred to as the core bottom surface) which is within a predetermined angle range from 180 degrees relative to the center of the gap 312, based on the angle at the center of the magnetic core 310. The amount of regulating member 360 applied is limited so that the excess regulating member 360 that protrudes when the magnetic core 310 is pressed does not adhere to the resin case 320, specifically the side surfaces of the left arm portion 313a and the right arm portion 313b of the magnetic core 310 (indicated by the symbol m in Figure 18, between the upper end of the magnetic core 310 and the corner R endpoint of the arm portion). At this time, by providing spaces 314a and 314b between the left arm 313a and the right arm 313b of the magnetic core 310 and the outer peripheral wall 325 of the resin case 320, the left arm 313a and the right arm 313b of the magnetic core are not constrained to expand and contract in the direction of expansion and contraction of the resin case 320 indicated by arrow F in the figure, thereby suppressing dimensional changes in the gap 312 of the magnetic core 310 and achieving the effect of suppressing changes in the output of the magnetic detection element 340.

[0038] Figure 19 shows an example of a structure related to increasing the adhesive strength between the magnetic core 310 and the resin case 320 in Embodiment 2. The resin case 420 is provided with a restricting structure 415 for applying a restricting member 460 to the bottom surface of the core housing portion 321 of the resin case 320 in Embodiment 2. The restricting structure 415 is provided with grooves 426a and 426b on a part of the bottom surface of the resin case 420 that is in contact with the core bottom surface portion (the outer linear portion between the left and right corner R endpoints on the bottom side of the magnetic core 410) which is within a predetermined angle range from a position 180 degrees from the gap 412 of the magnetic core 410. The magnetic core 410 is provided with a core protrusion shape 416 on the core bottom surface portion which is within a predetermined angle range from a position 180 degrees from the gap 312 of the magnetic core 310 in Embodiment 2. The core protrusion shapes 416a and 416b are formed to fit with the grooves 426a and 426b of the resin case 420. By bonding only the core bottom surface including the protruding shapes 416a and 416b with the restricting member 460, and by providing spaces 414a and 414b corresponding to spaces 314a and 314b between the magnetic core 410 and the outer peripheral wall 425 of the resin case 420, the left arm portion 413a and the right arm portion 413b of the magnetic core are not constrained in the direction of expansion and contraction due to the expansion and contraction of the resin case 420 due to temperature changes, thereby reducing the dimensional change of the gap 412, and the entire circumference of the core protruding shape 416 of the magnetic core 410 is covered by the restricting member 460, the bonding area is increased, and the strength against delamination between the magnetic core 410 and the resin case 420 can be increased.

[0039] Here, we will use simulation to verify the resistance to delamination when a restricting structure 415 is provided to increase adhesive strength. In the simulation, magnetic cores 310 and 410 are bonded to resin cases 320 and 420, and the stress on restricting members 360 and 460 when the magnetic cores 310 and 410 are pulled in the opposite direction to the bonding direction (upward direction in the illustration) will be confirmed by static structural analysis. The simulation conditions are shown in Figures 18 and 20, and the results are shown in Figure 21. In Figure 18, the core bottom surface (indicated as h) of the magnetic core 310 is a flat surface without the core protrusion shape 416, with h = 15 mm, and its entire surface is designated as the bonding area. Figure 20 shows the case where a core protrusion shape 416 is provided on the core bottom surface (symbol k) of the magnetic core 410. In Figure 20, the symbols i and j shown for the magnetic core 410 are the dimensions of the core protrusion shapes 416a and 416b, i=3mm and j=1.5mm, and the bonding area is the entire core bottom surface, with k=15mm. The dimensions in the depth direction (arrow Z direction) are 10 mm for the magnetic cores 310 and 410, 12 mm for the core housing section of the resin cases 320 and 420, and 10 mm for the adhesive area. Figure 21 shows the average stress generated on the restricting members 360 and 460 when the magnetic cores 310 and 410 are pulled with a force of 100 N in the upward direction (arrow Y direction) as shown in Figures 18 and 20, respectively, and the reduction rate of the average stress generated on the restricting member 460, based on the average stress generated on the restricting member 360. As shown in Figure 21, by providing the restricting structure 415 and core protrusion shape 416, the adhesive area is increased, and the stress generated on the restricting member 460 can be reduced by about 28%. The dimensions i, j, and k are not limited to these, and if the number of protrusions of the core protrusion shape 416 is N, h <k+j×2×N The shape should be such that the following relationship holds true.

[0040] In this embodiment, the core protrusion shapes 416a and 416b, which are intended to increase adhesive strength, are not limited to convex shapes. Any shape can be used as long as it increases the adhesive area between the magnetic core 410 and the regulating member 460 of the resin case 420, and the number of protrusions is not limited to two. [Explanation of symbols] 100, 300 Current Detectors 110, 310, 410 Magnetic Cores 112, 312, 412 gap 113a, 313a, 413a Left arm 113a, 313b, 413b Right arm 114a, 314a, 414a space (left side) 114b, 314b, 414b space (right side) 115a Space (left side) 115b Space (right side) 415 Regulatory Structure 416 Protrusion shape 120, 220, 320, 420 resin case 121, 321 Storage compartments 122, 322, 422 Insertion holes (insertion parts) 123, 323 Circuit board housing 124, 224 Inner peripheral wall 125, 225, 325, 425 outer wall 126a, 226a, 426a groove (left side) 126b, 226b, 426b Groove section (right side) 127, 227 Regulating member application position 128a Slope (left side) 128b Slope (right side) 130, 330 Circuit board section 140, 340 magnetic detection elements 160, 260, 360, 460 Regulating members

Claims

1. A current detector comprising a substantially rectangular magnetic core that collects magnetic flux generated by a current to be measured, a gap formed in the magnetic core, a magnetic detection element arranged within the gap of the magnetic core, and the magnetic core and the magnetic detection element housed in a resin case, wherein the magnetic core has an inner circumferential straight section at a predetermined angle from a position 180 degrees circumferentially with respect to the center of the gap, and is provided with a regulating member for bonding the magnetic core and the resin case, wherein the bonding region between the magnetic core and the resin case by the regulating member does not exist within a range of 90 degrees circumferentially with respect to the center of the gap at an angle at the center of the magnetic core, but rather exists within the range of the inner circumferential straight section in the width direction of the gap from a position 180 degrees circumferentially with respect to the center of the gap.

2. The current detector according to Claim 1, characterized in that the resin case is provided with grooves having a predetermined width and a predetermined depth at both ends within a predetermined angle range from a position 180 degrees circumferentially with respect to the center of the gap.

3. The current detector according to Claim 1, wherein the magnetic core has an outer peripheral straight portion in which the outer circumference is substantially straight within a predetermined angle range from a position 180 degrees circumferentially with respect to the center of the gap, the outer peripheral straight portion is provided with a convex or concave shape, the resin case has a shape molded to fit with the convex or concave shape, and there is an adhesive region between the magnetic core and the resin case by the regulating member in the outer peripheral straight portion.

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