JP6351210B2 - Current sensor - Google Patents

Description

  The present invention relates to a current sensor.

  A current sensor is known in which a part of a conductor through which a current to be measured flows is surrounded by an annular magnetic core, and a Hall element for measuring a magnetic field is disposed in the gap of the magnetic core (Patent Document 1). Known materials for the magnetic core include, for example, permalloy, ferrite, and high permeability nanocrystalline material.

JP-A-11-251167

  In the conventional current sensor, since a relatively expensive material is used for the magnetic core, reduction in manufacturing cost has been a problem. However, if the thickness of the magnetic core is simply reduced, the characteristics of the current sensor may deteriorate due to the influence of external noise.

  The present invention has been made in view of the above problems, and an object thereof is to provide a current sensor capable of reducing the cost while reducing the influence of external noise.

  In the above configuration, the thickness of the magnetic core in the direction along the current in the first gap of the magnetic core is equal to or less than the thickness of the region other than the first gap in the magnetic core. can do.

The current sensor of the present invention is disposed in an annular magnetic core divided into a first core and a second core surrounding a conductor through which a current flows, and a first gap formed in the first core. A first magnetic field measuring element that measures a magnetic field to be formed; a substrate on which the first magnetic field measuring element is mounted ; a first housing that accommodates the first core; and the second core; A housing having a second housing that can be opened and closed with respect to the housing. The first housing has a bearing, and the second housing is supported by a shaft inserted into the bearing. A first housing and a substrate, comprising: a middle housing that is engaged with a body so as to be openable and closable; and a lower housing that is engaged with the middle housing and has an opening that exposes a part of the substrate. It is accommodated in the middle housing engaged with each other and said lower housing, in the first gap Sectional area of the end portion of the serial first core, being smaller than the cross-sectional area of the magnetic core in the region other than the first gap of the magnetic core.
The said structure WHEREIN: The level | step-difference part which goes to the said 1st gap is formed in the said 1st core, The said board | substrate can be set as the structure arrange | positioned at the said level | step-difference part.

  ADVANTAGE OF THE INVENTION According to this invention, the magnetic body core in a current sensor can be attached or detached easily, and the versatility of a current sensor can be improved.

It is a figure which shows a current sensor. It is an exploded view of a current sensor. It is an external view of a current sensor. It is a figure which shows the detailed structure of a magnetic body core part. It is a figure which shows the comparison of the shape of a magnetic body core part. It is a perspective view of the magnetic body core which concerns on a 1st modification. It is a figure which shows the structure of the magnetic body core which concerns on a 2nd-3rd modification. It is a figure which shows the structure of the magnetic body core which concerns on a 4th-5th modification. It is a figure which shows the structure of the magnetic body core which concerns on a 6th-7th modification. It is a figure which shows the structure of the magnetic body core which concerns on the 8th-9th modification. It is a figure which shows the structure of the magnetic body core which concerns on a 10th-11th modification. It is a figure which shows the structure of the magnetic body core which concerns on the 12th-13th modification. It is a table | surface which shows the simulation result regarding noise. It is a figure which shows the detailed structure of the magnetic body core part of the current sensor which concerns on Example 2 and a comparative example. It is a figure which shows the detailed structure of the magnetic body core part of the current sensor which concerns on Example 3 and a comparative example. It is a table | surface which shows the simulation result regarding noise. It is a figure which shows a current sensor. It is a figure which shows the structure of the magnetic body core which concerns on Example 4 and a 1st-4th modification. It is a figure which shows the structure of the magnetic body core which concerns on the 5th-7th modification. It is a figure which shows the structure of the magnetic body core which concerns on an 8th modification.

  FIG. 1 is a diagram illustrating a configuration of a current sensor. FIG. 1A is a plan view seen from the direction of current bar penetration, and FIG. 1B is a side view seen from the direction of arrow A in FIG. As shown in FIGS. 1A and 1B, the current sensor includes an annular magnetic core 20 (a lower magnetic core 20a and an upper magnetic core 20b) that is divided into two vertically. The lower magnetic core 20a of the magnetic core 20 is further divided into two magnetic cores, and a Hall element 40 for detecting a magnetic field is provided apart from the magnetic core 20 in the divided space. Yes. In the following description, the cutout portion of the magnetic core 20 provided with the Hall element 40 is referred to as a gap 22. In addition, the two notches that divide the magnetic core 20 vertically are referred to as a first separator 24 and a second separator 26, respectively.

  A current bar 10, which is an example of a conductor through which a current to be measured flows, is provided at the center portion of the annular structure formed by the magnetic core 20 so as to penetrate the annular structure. An annular magnetic field H is formed in the magnetic core 20 by the current I flowing through the current bar 10. In the current sensor, the current can be measured by detecting the magnetic field H by the Hall element 40.

  As a material of the magnetic core 20, for example, a material such as permalloy, ferrite, or a high permeability nanocrystal material can be used. Among these, when a relatively soft material such as a high permeability nanocrystal material is used, the contact between the magnetic cores 20 in the first separation part 24 and the second separation part 26 is improved, and the characteristics of the current sensor are improved. There is an advantage of doing. Note that a soft material such as a high-permeability nanocrystal material may be used only around the first separation unit 24 and the second separation unit 26, and a lower-cost material may be used for other portions.

  FIG. 2 is an exploded view of the current sensor. The current sensor includes three housings (lower housing 50, middle housing 52, and upper housing 54) for housing and fixing the magnetic core 20. The Hall element 40 is mounted so as to protrude from the surface of the substrate 42, and the substrate 42 is configured to be mounted below the magnetic core 20 in the lower housing 50. The lower housing 50 engages with the middle housing 52 and houses the lower magnetic core 20a and the substrate 42. The upper housing 54 engages with the middle housing 52 and accommodates the upper magnetic core 20b. The lower housing 50 and the middle housing 52 can be fixed by engaging corresponding convex portions and concave portions with each other, for example. Further, the upper housing 54 and the middle housing 52 can be fixed to each other so as to be rotatable around one side by inserting a shaft 58 into a bearing portion having a common central axis, for example. The method for fixing the casings is not limited to the above example as long as the magnetic core 20 and the Hall element 40 can be fixed at predetermined positions.

  3A and 3B are external perspective views of the current sensor. The lower housing 50 and the middle housing 52 are fixed to each other by a convex portion and a concave portion (not shown) so as to be freely opened and closed. The upper housing 54 and the middle housing 52 are fixed to each other so as to be openable and closable by a shaft and a bearing portion (not shown) and an engaging portion 56 having a snap fit structure. An opening 51 is formed in the lower housing 50. A part of the substrate 42 is exposed to the outside from the lower housing 50, and a connection terminal 44 for external connection is formed in the exposed portion. The connection terminal 44 is electrically connected to the Hall element 40 via a wiring (not shown) formed on the substrate 42.

  Here, since the above-described permalloy, ferrite, high permeability nanocrystalline material, etc. used as the material of the magnetic core 20 are relatively expensive materials, it is preferable to reduce the amount of use thereof as much as possible. On the other hand, when the thickness of the magnetic core 20 is reduced, the influence of external noise increases and the characteristics of the current sensor may be deteriorated. In the following description, the shape of the magnetic core 20 for solving the above problem will be described.

  FIG. 4 is a diagram showing the configuration of the magnetic core portion. 4A is a side view as seen from the penetration direction of the current bar 10, FIG. 4B is a side view as seen from the direction A of FIG. 4A, and FIG. 4C is an external perspective view. In any of the drawings, only the configuration of the magnetic core 20 is shown, and other components (current bar 10, Hall element 40, etc.) are omitted. 4B shows the shape of the end face in the gap 22 of the magnetic core 20 (the same applies to the subsequent drawings).

  As shown in FIGS. 4A to 4C, in the current sensor according to the first embodiment, the magnetic core 20 is formed so that the thickness of the magnetic core 20 is reduced in the vicinity of the gap 22. Thereby, the cross-sectional area of the end surface of the magnetic core 20 in the gap 22 is smaller than the cross-sectional area of the magnetic core 20 other than the gap 22 (for example, the first separator 24 and the second separator 26). Yes. As shown in FIG. 4C, in Example 1, the thickness of the magnetic core 20 in the direction along the current I (the dimension in the horizontal direction in FIG. 4C) is uniform throughout the entire magnetic core. It is. Moreover, the distance (for example, 50 μm) between the end surfaces of the magnetic core 20 in the first separation unit 24 and the second separation unit 26 is significantly smaller than the distance between the end surfaces in the gap 22 (for example, 1.7 mm). It has become.

  According to this configuration, since the amount of the material constituting the magnetic core 20 can be reduced by the amount that the cross-sectional area of the magnetic core 20 is reduced, the manufacturing cost of the magnetic core 20 can be reduced. it can. Further, the configuration in which the cross-sectional area of the magnetic core 20 is reduced only in the vicinity of the gap 22 is excellent in terms of reducing the influence of external noise, which will be described in detail below. Note that the “cross-sectional area” refers to a cross-sectional area of a cross section perpendicular to the magnetic field H formed by the current I flowing through the current bar 10 in the cross section of the magnetic core 20.

  FIG. 5 is a diagram showing a comparison of the shapes of the magnetic core portions. FIG. 5A is the same as FIG. 4A and shows a magnetic core according to this example. FIG. 5B is a view showing a first comparative example in which the cross-sectional area of the magnetic core 20 near the gap 22 is made uniform without reducing it, and the cross-sectional area of the magnetic core 80 is shown in FIG. The cross-sectional areas of the magnetic cores 20 of the first separator 24 and the second separator 26 are the same. FIG. 5C is a view showing a second comparative example in which the cross-sectional area of the magnetic core is uniformly reduced, and the cross-sectional area of the magnetic core 80 is the cross-sectional area of the gap 22 portion of FIG. Is the same. In the first comparative example and the second comparative example, as a configuration corresponding to the magnetic core 20, the gap 22, the first separation portion 24, and the second separation portion 26 of the first embodiment, the magnetic core 80, the gap 82, the first A separation part 84 and a second separation part 86 are provided.

  Generally, in the current sensor, the influence of external noise can be reduced as the thickness of the magnetic core 20 increases. In the first comparative example of FIG. 5B, the cross-sectional area of the magnetic core 80 is uniform, and the cross-sectional areas of the first separation part 24 and the second separation part 26 of Example 1 (FIG. 5A). It is the same. For this reason, although the influence of external noise can be reduced, it is difficult to reduce the usage amount of the material constituting the magnetic core 80 and the manufacturing cost of the magnetic core 80.

  On the other hand, in the second comparative example of FIG. 5C, the cross-sectional area of the magnetic core 80 including the gap 82 is uniform and is the same as the cross-sectional area of the gap 22 of Example 1 (FIG. 5A). It has become. For this reason, although the amount of material used and the manufacturing cost of the magnetic core 80 can be reduced, the influence of external noise increases, and the characteristics as a current sensor deteriorate.

  On the other hand, in Example 1 of FIG. 5A, the cross-sectional area of the magnetic core 20 is reduced only in the vicinity of the gap 22, and the cross-sectional area of the magnetic core 20 is the same as that of the first comparative example in other regions. It is trying to be equivalent. Thereby, reduction of the material usage-amount and manufacturing cost of the magnetic body core 20 can be aimed at, reducing the influence of external noise. Various methods other than those described in the first embodiment are conceivable as a method for reducing the cross-sectional area of the magnetic core 20 in the vicinity of the gap 22. Hereinafter, the current sensor according to the modification of the first embodiment will be described with reference to FIGS. 6 to 12, and the simulation result using the current sensor according to the first embodiment and the modification will be shown in FIG.

  FIG. 6 is a perspective view of a magnetic core according to a first modification. In this modification, the thickness of the magnetic core 20 at the end face of the gap 22 is smaller not only in the direction perpendicular to the current I through direction but also in the direction along the current I than in the other portions. ing. More specifically, the thickness (width) of the magnetic core 20 in the current I direction is configured to gradually decrease toward the end face of the gap 22. Thereby, compared with the structure of Example 1 (FIG.4 (c)), since the usage-amount of the magnetic body core 20 can further be reduced, the further reduction of manufacturing cost can be aimed at.

  FIG. 7 is a diagram illustrating a configuration of a magnetic core according to the second modification and the third modification. FIG. 7A is a side view of the magnetic core according to the second and third modifications viewed from the penetration direction of the current I, and FIG. 7B is the first view viewed from the direction of arrow A in FIG. It is a side view of the magnetic body core by 2 modifications. FIG. 7C is a perspective view of the magnetic core according to the second modification, and FIG. 7D is a perspective view of the magnetic core according to the third modification.

  As shown in FIG. 7A, in this modification, the magnetic core 20 has a tapered shape that widens from the end face of the gap 22 toward the opposite side. Thus, by processing the vicinity of the gap 22 into a tapered shape, the amount of material used for the magnetic core 20 can be reduced while reducing the influence of external noise, as in the first embodiment. In the second modification (FIG. 7C), the thickness of the magnetic core 20 in the direction along the current I is uniform in all regions, but in the third modification (FIG. 7D). The thickness of the magnetic core 20 in the direction along the current I is smaller than the other regions on the end face of the gap 22. In the third modification, the thickness (width) of the magnetic core 20 in the current I direction is gradually reduced toward the end face of the gap 22. For this reason, the 3rd modification can further reduce the material usage-amount of the magnetic body core 20 compared with the 2nd modification.

  FIG. 8 is a diagram illustrating a configuration of a magnetic core according to the fourth modification and the fifth modification. FIG. 8A is a side view of a magnetic core according to a fourth modification viewed from the direction of current I penetration, and FIG. 8B is a side view viewed from the direction of arrow A in FIG. FIG. 8C is a perspective view of the magnetic core according to the fourth modification, and FIG. 8D is a perspective view of the magnetic core according to the fifth modification.

  In the magnetic core 20 shown in FIG. 8A, the end face of the gap 22 is chamfered. In other words, the end surface of the gap 22 includes both a surface perpendicular to the magnetic field and a surface inclined with respect to the magnetic field. Thus, by chamfering the end face of the gap 22, the amount of material used for the magnetic core 20 can be reduced while reducing the influence of external noise, as in the first embodiment.

  In the fourth modification (FIG. 8C), the thickness of the magnetic core 20 in the direction along the current I is uniform in all regions, but in the fifth modification (FIG. 8D). The thickness of the magnetic core 20 in the direction along the current I is smaller than the other regions on the end face of the gap 22 (see reference numeral 29). For this reason, the 5th modification can further reduce the material usage-amount of the magnetic body core 20 compared with the 4th modification.

  FIG. 9 is a diagram illustrating a configuration of a magnetic core according to a sixth modification and a seventh modification. FIG. 9A is a side view of a magnetic core according to a sixth modification viewed from the penetration direction of the current I, and FIG. 9B is a side view viewed from the direction of arrow A in FIG. FIG. 9C is a perspective view of a magnetic core according to a sixth modification, and FIG. 9D is a perspective view of a magnetic core according to a seventh modification.

  As shown in FIG. 9A, in this modification, the corner portion of the end face of the gap 22 in the magnetic core 20 is curved. Thus, by processing the end face of the gap 22 as well, the amount of material used for the magnetic core 20 can be reduced while reducing the influence of external noise, as in the first embodiment. In the sixth modification (FIG. 9C), the thickness of the magnetic core 20 in the direction along the current I is uniform in all regions, but in the seventh modification (FIG. 9D). The thickness of the magnetic core 20 in the direction along the current I is smaller than the other regions on the end face of the gap 22. For this reason, the seventh modification can further reduce the amount of material used for the magnetic core 20 compared to the sixth modification.

  FIG. 10 is a diagram illustrating a configuration of a magnetic core according to the eighth modification and the ninth modification. FIG. 10A is a side view of a magnetic core according to an eighth modification viewed from the penetration direction of the current I, and FIG. 10B is a side view viewed from the direction of arrow A in FIG. FIG. 10C is a perspective view of the magnetic core according to the eighth modification, and FIG. 10D is a perspective view of the magnetic core according to the ninth modification.

  As shown in FIG. 10A, in the present modification, a stepped portion 28 toward the gap 22 is formed in the vicinity of the gap 22 in the magnetic core 20. The step portion 28 is formed so that the thickness of the magnetic core 20 in the direction orthogonal to the current I direction gradually decreases toward the gap 22 that is the end face of the magnetic core 20. As described above, the configuration in which the step portion 28 is formed in the vicinity of the gap 22 can also reduce the amount of material used for the magnetic core 20 while reducing the influence of external noise as in the first embodiment. In the eighth modification (FIG. 10C), the thickness of the magnetic core 20 in the direction along the current I is uniform in all regions, but in the ninth modification (FIG. 10D). The thickness of the magnetic core 20 in the direction along the current I is smaller than the other regions on the end face of the gap 22. For this reason, the ninth modification can further reduce the material usage of the magnetic core 20 compared to the eighth modification. The stepped portion 28 may be formed on both upper and lower surfaces of the magnetic core 20 as shown in FIG. 10, or may be formed only on one side of the upper surface or the lower surface.

  FIG. 11 is a diagram illustrating a configuration of a magnetic core according to the tenth modification and the eleventh modification. FIG. 11A is a side view as seen from the penetration direction of the current I, and FIG. 11B is a side view as seen from the direction of arrow A in FIG. FIG. 11C is a perspective view of the tenth modification, and FIG. 11D is a perspective view of the eleventh modification.

  As shown in FIG. 11A, in the present modification, the thickness of the magnetic core 20 in the direction perpendicular to the current I is a taper shape that increases from the end face of the gap 22 toward the opposite side. Furthermore, the end of the magnetic core 20 in the gap 22 has an acute shape. As described above, the material usage of the magnetic core 20 can be reduced while reducing the influence of external noise, as in the first embodiment, by making the end of the magnetic core 20 have an acute shape. In the tenth modification (FIG. 11C), the thickness of the magnetic core 20 in the direction along the current I is uniform in all regions, but in the eleventh modification (FIG. 11D). The thickness of the magnetic core 20 in the direction along the current I is configured to gradually decrease toward the end face of the gap 22. For this reason, the 11th modification can further reduce the amount of material used for the magnetic core 20 compared to the 10th modification.

  FIG. 12 is a diagram illustrating a configuration of a magnetic core according to the twelfth modification and the thirteenth modification. 12A is a side view seen from the direction of current I penetration, and FIG. 12B is a side view seen from the direction of arrow A in FIG. FIG. 12C is a perspective view of the twelfth modification, and FIG. 12D is a perspective view of the thirteenth modification.

  As shown in FIG. 12A, in the present modification, a stepped portion 28 toward the gap 22 is formed in the vicinity of the gap 22 in the magnetic core 20. The step portion 28 is formed so that the thickness of the magnetic core 20 in the direction orthogonal to the current I direction gradually decreases toward the gap 22 that is the end face of the magnetic core 20. Furthermore, a part of the upper surface of the step portion 28 (inside of the magnetic core 20, reference numeral 27) has a chamfered corner, and the lower surface of the step portion 28 (the magnetic core 20 has In a part of the outer side (see reference numeral 29), the corner portion of the step portion is curved.

  As described in the first embodiment, even when the stepped portion 28 (see FIG. 10), the chamfered structure (see FIG. 8), and the curved structure (see FIG. 9) are combined, the effect of external noise is reduced. The usage amount of the body core 20 can be reduced. In the twelfth modification (FIG. 12C), the thickness of the magnetic core 20 in the direction along the current I is uniform in all regions, but in the thirteenth modification (FIG. 12D). The thickness of the magnetic core 20 in the direction along the current I gradually decreases toward the gap 22, and is smaller than the other regions at the end face of the gap 22. For this reason, the thirteenth modification can further reduce the amount of material used for the magnetic core 20 compared to the twelfth modification.

  FIG. 13 is a table showing simulation results regarding noise. Here, the first comparative example (FIG. 5B), the fourth modification (FIGS. 8A to 8C), the eighth modification (FIGS. 10A to 10C), and the tenth modification. For each of the examples (FIGS. 11A to 11C), A: magnetic flux density when a current of 100 A is passed through the current bar 10 (upper table), B: magnetic flux density when external noise of 1 mT is applied. (In the middle of the table) A simulation was performed on the ratio of noise calculated by dividing C: B by A.

  The magnetic core 20 used for the simulation was formed into a substantially square rectangular shape shown in FIGS. 5B, 8A, 10A, and 11A. As dimensions common to the comparative examples to the modified examples, the vertical and horizontal lengths (L1, L2) of the hollow portions were each 12 mm. Further, the thickness (L3) in the direction along the current I in the magnetic core 20 is 4 mm, and the thickness (L4) of the magnetic core 20 in the region other than the gap 22 portion in the thickness in the direction perpendicular to the current I is It was 3 mm. The distance (L5) between the end faces in the gap 22 portion was 1.7 mm.

  In the fourth modification (FIG. 8A), the length (L6) of the hypotenuse of the chamfered portion is 1 mm. In the eighth modification (FIG. 10A), the thickness (L7) of the magnetic core 20 at the end face of the gap 22 is 1 mm. Moreover, the length (L8) of the part in which the level | step difference is formed in the level | step-difference part 28 was 3.7 mm both up and down. In the tenth modification (FIG. 11A), the length (L9) of the inclined surface is 1.5 mm.

  As shown in FIG. 13, in the first comparative example, the fourth modified example, and the eighth modified example, there was almost no difference between the magnetic flux density when the current was applied and the magnetic flux density when the external noise was applied. For this reason, there was almost no difference in the ratio of noise. On the other hand, in the tenth modification in which the end face of the gap portion is an acute angle, a decrease in the magnetic flux density at the time of applying the current was observed, but the magnetic flux density at the time of applying the noise was similarly reduced. The results were almost the same as the comparative example, the fourth modified example, and the eighth modified example.

  As described above, according to this simulation, it has been demonstrated that the ratio of noise hardly changes compared to the comparative example even if the configuration in which the cross-sectional area of the magnetic core 20 is reduced only in the vicinity of the gap 22 is adopted. It was done. Therefore, according to the current sensor according to the first embodiment and the modification thereof, it is possible to reduce the usage amount and the manufacturing cost of the magnetic core 20 while reducing the influence of external noise.

  Example 2 is an example in which a substrate is arranged in a step portion near the gap.

  FIG. 14A is a diagram illustrating the configuration of the magnetic core portion of the current sensor according to the second embodiment, and FIG. 14B is a diagram illustrating the configuration according to the comparative example. As shown in FIG. 14A, in Example 2, the substrate 42 on which the Hall element 40 is mounted has a lower surface side (outside of the magnetic core 20) among the stepped portions 28 formed on the magnetic core 20. It is the structure arrange | positioned in the level | step difference of. The shape itself of the magnetic core 20 is the same as that of the eighth and ninth modifications shown in FIG. 10, and detailed description thereof is omitted here.

  On the other hand, in the comparative example shown in FIG. 14B, the step portion 28 is not formed on the magnetic core 20, and the substrate 42 is disposed outside the annular structure formed by the magnetic core 20. In the comparative example, the Hall element 40 is mounted on the substrate 42 via the spacer 43 in order to reach the Hall element 40 to the center position of the magnetic core 20.

  Comparing the current sensors according to the second embodiment and the comparative example, in the second embodiment, the substrate 42 can be accommodated in the annular structure formed by the magnetic core 20, so that the current sensor is equivalent to the thickness of the substrate 42. Can be miniaturized. Further, since the Hall element 40 can reach the center position of the magnetic core 20 without using the spacer 43, the number of parts can be reduced as compared with the comparative example. As described above, according to the current sensor according to the second embodiment, the current sensor can be further reduced in size and cost.

  Example 3 is an example in which the division position of the magnetic core is changed.

  FIGS. 15A to 15B are diagrams illustrating the configuration of the magnetic core portion of the current sensor according to the third embodiment, and FIGS. 15C to 15F are diagrams illustrating the configuration according to the comparative example. is there. 15 (a), (c), and (e) are side views as viewed from the penetration direction of the current I, and FIGS. 15 (b), (d), and (f) are FIG. 15 (a), respectively. It is the side view seen from the arrow A direction of (c), (e). As shown in FIGS. 15A to 15F, the thickness of the magnetic core 20 is uniform in the region including the end face of the gap 22.

  As shown in FIG. 15A, in the current sensor according to the third embodiment, the first separation portion 24 and the second separation portion 26 that separate the magnetic core 20 up and down are formed on the side close to the gap 22. Yes. In other words, the center line of the magnetic core 20a positioned between the gap 22 and the first separator 24 and the center line of the magnetic core 20b positioned between the gap 22 and the second separator 26 (both (Shown by dotted line C) is a straight line having no inflection point and a common configuration. Here, “common” means that the center line of the magnetic core 20a completely overlaps with the center line of the magnetic core 20b.

  On the other hand, in the first modified example (FIGS. 15C to 15D), the first separation unit 24 and the second separation unit 26 are formed near the center of the magnetic core 20. In the second modification (FIGS. 15E to 15F), the first separation portion 24 and the second separation portion 26 are formed on the side far from the gap 22 in the magnetic core 20. In any case, the center line (C1) of the magnetic core 20a located between the gap 22 and the first separation portion 24 and the center of the magnetic core 20b located between the gap 22 and the second separation portion 26. The line (C2) has an inflection point and is not common (the two center lines do not overlap after the inflection point).

  FIG. 16 is a table showing simulation results regarding noise. Here, Example 3 (FIGS. 15A to 15B), the first comparative example (FIGS. 15C to 15D), and the second comparative example (FIGS. 15E to 15F). For each, A: magnetic flux density when current of 100 A is passed through the current bar 10 (upper table), B: magnetic flux density when external noise of 1 mT is applied (middle table), and C: B divided by A. The same simulation as in Example 1 was performed for the calculated noise ratio.

  As shown in FIGS. 15A to 15F, the magnetic core 20 used in the simulation has a substantially square rectangular shape with a section cut out. The vertical and horizontal lengths (L1, L2) of the hollow portions were each 12 mm. The thickness (L3) in the direction along the current I in the magnetic core 20 was 4 mm, and the thickness (L4) in the direction perpendicular to the current I was 3 mm. The distance (L5) between the end faces in the gap 22 portion was 1.4 mm. Furthermore, the distance between the end surfaces of the magnetic core 20 in the first separation part 24 and the second separation part 26 was 50 μm.

  As shown in FIG. 16, there was almost no difference in the magnetic flux density at the time of current application in both Example 3 and Comparative Example. However, as shown in the middle part of the table, the magnetic flux density when external noise was applied was smallest in Example 3, and increased in the order of the first comparative example and the second comparative example. As a result, the ratio of noise was also the smallest in Example 3, and the result increased in the order of the first comparative example and the second comparative example. In particular, between Example 3 and the second comparative example, a significant difference of nearly twice as much was observed in the noise ratio.

  From the above, as in the third embodiment, the magnetic core 20a located between the gap 22 and the first separation portion 24 and the magnetic core 20a located between the gap 22 and the second separation portion 26 are used. By making the central line of the body core 20b a straight line having no inflection point and a common configuration, it is possible to reduce the influence of noise. The configuration of the third embodiment can be used in combination with the configuration of reducing the cross-sectional area of the magnetic core 20 in the gap 22 portion described in the first and second embodiments, thereby reducing noise and manufacturing cost. This can be achieved more effectively.

  Example 4 is an example using a differential signal type current sensor.

  FIG. 17 is a diagram illustrating a configuration of a differential signal type current sensor. FIG. 17A is a plan view seen from the direction of current bar penetration, and FIG. 17B is a side view seen from the direction of arrow A in FIG. Here, the description will focus on the differences from the first embodiment (FIG. 1), and a description of common parts will be omitted.

  In the current sensor shown in FIG. 17, the gap 30 is formed not only in the lower magnetic core 20 a but also in the upper magnetic core 20 b, and the Hall element 40 is disposed in the gap 30. In the following description, the gap formed in the lower magnetic core 20a is referred to as a first gap 22, and the gap formed in the upper magnetic core 20b is referred to as a second gap 30.

  The Hall element 40a disposed in the first gap 22 and the Hall element 40 disposed in the second gap 30 detect the magnetic field H formed by the current I, respectively. The detected magnetic field is converted into an electrical signal, and then output from the current sensor as a differential signal via a wiring board on which each Hall element is mounted. As described above, in the current sensor of FIG. 17, the accuracy of current measurement can be improved by using the differential signal. Also in the current sensor using the differential signal as shown in FIG. 17, noise and manufacturing cost can be reduced by the configuration described in the first to third embodiments. Hereinafter, this point will be described.

  FIG. 18A is a diagram illustrating a configuration of a magnetic core portion in the current sensor according to the fourth embodiment, and FIGS. 18B to 18E are diagrams illustrating configurations according to the modification. As shown in FIG. 18A, in Example 4, the cross-sectional areas of the end faces of the first gap 22 and the second gap 30 in the magnetic core 20 are smaller than the cross-sectional areas of other regions. . Thereby, for the same reason as described in the first embodiment, it is possible to reduce the usage amount and manufacturing cost of the magnetic core 20 while reducing the influence of external noise.

  In the first modification of FIG. 18B, the cross section of the magnetic core 20 in the vicinity of the first gap 22 and the second gap 30 has a tapered shape that widens from the end face toward the opposite side. In the second modification of FIG. 18C, the corners of the end faces of the magnetic core 20 in the first gap 22 and the second gap 30 are chamfered. In the third modification of FIG. 18D, the corners of the end face of the magnetic core 20 in the first gap 22 and the second gap 30 are curved. 18 (e), the end face of the magnetic core 20 in the first gap 22 and the second gap 30 has an acute angle. The usage amount and manufacturing cost of the body core 20 can be reduced.

  FIG. 19 is a diagram illustrating another modification of the fourth embodiment. In the fifth modification of FIG. 19A, stepped portions 28 are formed in the vicinity of the first gap 22 and the second gap 30. In the sixth modified example of FIG. 19B, the corners of the stepped portion 28 are chamfered or curved, as in the twelfth to thirteenth modified examples (FIG. 12) in the first embodiment. Also in this configuration, similarly to the fourth embodiment, the usage amount and manufacturing cost of the magnetic core 20 can be reduced. In addition, in the seventh modified example of FIG. 19C, the substrate 42 on which the Hall element 40 is mounted is arranged in each stepped portion 28 as in the second embodiment (FIG. 14). . According to this configuration, the current sensor can be further reduced in size and cost compared to the fourth embodiment for the same reason as described in the second embodiment.

  FIG. 20 is a diagram illustrating another modification of the fourth embodiment. In the eighth modified example of FIG. 20, in addition to the first separation part 24 and the second separation part 26, a third separation part 32 and a fourth separation part 34 that separate the magnetic core 20 other than the gap part are formed. ing. Similar to the third embodiment (FIG. 15A), the center line of the magnetic core 20a located between the first gap 22 and the first separation portion 24, the first gap 22 and the second separation portion 26, and The center line of the magnetic core 20b located between the two (both shown by the dotted line C1) is a straight line having no inflection point and has a common configuration. In addition, the center line of the magnetic core 20c located between the second gap 30 and the third separator 32 and the center line of the magnetic core 20d located between the second gap 30 and the fourth separator 34 are shown. (Both are indicated by a dotted line C2) is a straight line having no inflection point and a common configuration. According to this configuration, as in the case of the third embodiment, an effect of reducing the influence of external noise can be expected.

  In Examples 1-4, although the example which made the shape of the magnetic body core 20 rectangular was demonstrated, it is also possible for the shape of the magnetic body core 20 to be other than a rectangle. For example, even when the shape of the magnetic core 20 is substantially circular when viewed from the direction of current I penetration, the cross-sectional area of the end face of the gap 22 portion is made smaller than the cross-sectional area of other regions, thereby The amount of magnetic core used can be reduced while reducing noise.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

10 Current bar 20 Magnetic core 22 Gap (first gap)
24 1st separation part 26 2nd separation part 28 Step part 30 2nd gap 32 3rd separation part 34 4th separation part 40 Hall element 42 Substrate 43 Spacer 44 Connection terminal 50 Lower housing 52 Middle housing 54 Upper housing 56 Engagement part 58 shaft

Claims (2)

An annular magnetic core divided into a first core and a second core surrounding a conductor through which a current flows;
A first magnetic field measuring element disposed in a first gap formed in the first core and measuring a magnetic field formed by the current;
A substrate on which the first magnetic field measuring element is mounted;
A housing having a first housing that houses the first core, and a second housing that houses the second core and engages the first housing so as to be openable and closable,
The first housing has a bearing, and is engaged with the second housing by an axis inserted into the bearing so as to be opened and closed, and is engaged with the middle housing, A lower housing having an opening for exposing a part thereof,
The first core and the substrate are accommodated in the middle casing and the lower casing engaged with each other,
The current sensor according to claim 1, wherein a cross-sectional area of an end portion of the first core in the first gap is smaller than a cross-sectional area of the magnetic core in a region other than the first gap in the magnetic core. The first core is formed with a step portion toward the first gap,
Current sensor according to claim 1 wherein the substrate is characterized in that disposed in the stepped portion.

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