Current sensor

Abstract

A current sensor 1 according to the present invention comprises: a core member 2 that has a first gap 22 sandwiched by end surfaces 21, is formed in an annular shape through which a busbar 4 can be inserted, and concentrates a magnetic field generated when current flows through the busbar 4; and a magnetic detection unit 3 capable of detecting the magnetic field collected by the core member 2. The magnetic detection unit 3 has a detection surface 31 for detecting the magnetic field and is capable of detecting a magnetic field component parallel to the detection surface 31. As a result of the detection surface 31 being arranged parallel to the direction in which the two end surfaces 21 forming the first gap 22 face each other, it is possible to stably maintain the position of a magnetoelectric conversion element even when vibration occurs, thus making the present invention suitable for reducing size and thickness.

Description

Current Sensor

[0001] The present invention relates to a current sensor that detects a magnetic field generated by a current to be measured flowing through a conductor and measures the current value of the current to be measured from the detected magnetic field.

[0002] In recent years, current sensors have been used to control and monitor various devices by attaching them to measure the current flowing through them. Known current sensors of this type use a magnetoelectric transducer that senses the magnetic field generated by the current flowing through the current path. Another type of current sensor is known, which has a core member surrounding the current path to facilitate magnetic field detection, and a Hall element as a magnetoelectric transducer located within the gap of the core member.

[0003] Patent Document 1 describes a current detection device including a magnetic core and a Hall element, with the aim of avoiding current detection errors caused by pressure applied to the magnetic core, etc. Patent Document 2 describes a current detection device with a magnetic core formed in series around a hollow portion with both ends facing each other across a gap, and a Hall element disposed in the gap to detect magnetic flux that changes in accordance with the current passing through the hollow portion, with the aim of achieving both miniaturization of the magnetic core and suppressing deterioration of detection accuracy caused by noise magnetic field lines.

[0004] JP 2013-142579 A JP 2012-247197 A

[0005] The current detection devices described in Patent Documents 1 and 2 suffer from variations in detection accuracy if the position of the Hall element within the gap of the core member is not stable. Therefore, a structure and components are required that can stably maintain the position of the Hall element when the current detection device vibrates. Furthermore, because the Hall element detects magnetic fields perpendicular to its detection surface, the detection surface of the Hall element must be positioned opposite the end face of the gap in the core member. Therefore, the end face defining the gap must have an area approximately the same as the detection surface of the Hall element. For these reasons, it has been difficult to reduce the size and thickness of current detection devices. Therefore, an object of the present invention is to provide a current sensor that can stably maintain the position of the magnetoelectric conversion element even when vibration occurs and is suitable for reducing the size and thickness.

[0006] The present invention provides a current sensor that solves the above-described problems by providing the following configuration: A current sensor includes a core member having a first gap sandwiched between end faces, formed in an annular shape so that a bus bar can be inserted therethrough, and configured to collect a magnetic field generated when a current to be measured flows through the bus bar; and a magnetic detector capable of detecting the magnetic field collected by the core member, wherein the magnetic detector has a detection surface that detects the magnetic field and is capable of detecting a magnetic field component parallel to the detection surface, and the detection surface is arranged parallel to the direction in which the two end faces that form the first gap face each other. This configuration eliminates the need to match the size of the end faces of the first gap with the size of the detection surfaces of the magnetic sensor, thereby enabling the height of the core member to be kept low.

[0007] The magnetic detector may be mounted on a substrate, and the surface of the substrate may be perpendicular to the end surface of the core member. With this configuration, even when vibration is applied to the magnetic sensor, the position of the magnetic detector is unlikely to shift in a direction parallel to the surface of the substrate, and even if the substrate is bent, the detection surface will not tilt with respect to the detection magnetic field. Therefore, it is possible to suppress a decrease in detection accuracy due to vibration without providing a structure or component for stably maintaining the position of the detection surface.

[0008] The substrate and the core member may be locked together. This configuration stabilizes the positional relationship between the magnetic detector and the core member, thereby reducing detection errors due to errors in attachment position.

[0009] The core member may have a second gap at a position different from the first gap. The second gap allows the magnitude of the magnetic field detected by the magnetic detector to be adjusted. Therefore, the measurable range of the current sensor can be changed using the same magnetic detector and substrate.

[0010] The current sensor includes a housing containing the magnetic detector and the core member, the housing having a busbar through hole through which the busbar can be inserted, the busbar through hole penetrating the inside of a ring formed by the core member, and the cross-sectional shape of the busbar through hole may have a first margin in a direction in which the two end faces forming the first gap face each other and a second margin in a direction perpendicular to the direction in which the two end faces face each other. Providing the first and second margins facilitates insertion of the busbar into the busbar through hole. Furthermore, by making the first margin larger than the second margin, the current sensor can exhibit a small deviation in measurement sensitivity even when the busbar is attached off-center in the busbar through hole.

[0011] The current sensor may have the bus bar through which the current to be measured can flow, the bus bar being disposed so as to penetrate the inside of a ring formed by the core member, and a housing that integrally holds the magnetic detection unit, the core member, and the bus bar. Forming the bus bar and the housing integrally prevents misalignment between the bus bar and the housing, resulting in a current sensor with high detection accuracy.

[0012] When viewed along the direction of the central axis of the ring of the core member, the magnetic detector may be positioned at a position offset from a line passing through the centers of the two end faces forming the first gap, and at least a portion of the magnetic detector may be positioned so as to overlap the first gap. With this configuration, the detection magnetic field generated by the current to be measured is reduced, thereby increasing the range of current that can be measured by the current sensor.

[0013] The detection element of the magnetic detector may be a magnetoresistive element. By using a magnetoresistive element, the detection surface can be arranged parallel to the direction in which the two end faces forming the first gap face each other, which is advantageous for miniaturizing the current sensor.

[0014] The magnetic detection unit may be disposed outside the first gap and overlap the first gap when viewed from a direction perpendicular to the detection surface. This configuration reduces the effect of heat generated by the bus bar on the magnetic detection unit when a current to be measured flows, thereby improving the detection accuracy and durability of the current sensor.

[0015] When viewed from a direction perpendicular to the direction in which the end faces forming the first gap face each other on the detection surface, the magnetic detector may be positioned offset from the first gap in a direction along the central axis of the ring of the core member, and may be positioned so as to overlap the first gap when viewed from a direction along the central axis of the ring of the core member. With this configuration, when the current sensor has multiple measurement phases, the magnetic field from adjacent measurement phases contains many components perpendicular to the sensitivity direction of the detector, thereby reducing the influence of adjacent measurement phases. This improves the detection accuracy of the current sensor.

[0016] A grounded substrate may be disposed between the core member and the magnetic detector. With this configuration, when the core member is subjected to electromagnetic noise, the electromagnetic noise can be shielded by the GND of the substrate, thereby improving the noise resistance of the current sensor.

[0017] A sub-magnetic detector may be disposed on the surface of the substrate opposite to the surface on which the magnetic detector is disposed. The detection element of the sub-magnetic detector may be a magnetoresistive element and may be disposed outside the first gap of the core member. By providing a sub-magnetic detector in addition to the magnetic detector, redundancy is improved, resulting in a highly reliable current sensor.

[0018] The detection element of the magnetic detector may be a magnetoresistive element, and the detection element of the sub-magnetic detector may be a Hall sensor, and the Hall sensor may be disposed in the first gap of the core member. By configuring the magnetic detector and the sub-magnetic detector with different detection elements, the possibility of problems occurring simultaneously in both detection elements is reduced, thereby improving the reliability of the current sensor.

[0019] According to the present invention, it is not necessary to make the end face of the core member have the same area as the detection surface of the magnetic detection unit, and the thickness of the core member can be adjusted according to the magnitude of the current to be detected, making it possible to provide a current sensor that is suitable for miniaturization and thinning.

[0020] 7A . FIG. 7B is a front view of the current sensor according to the first embodiment. FIG. 7C is a side view of the current sensor according to the first embodiment. FIG. 7D is a perspective view of a core in a current sensor according to a modified example. FIG. 7E is a front view of a current sensor according to another modified example. FIG. 7F is an exploded perspective view of the current sensor. FIG. 7G is a front view of a current sensor according to another modified example. FIG. 7H is a cross-sectional view showing an enlarged view of the busbar and the busbar through hole in the current sensor of FIG. 5A. FIG. 7I is a graph showing the effect of misalignment of the busbar on sensitivity in the current sensor according to the modified example of FIG. 5A. FIG. 7I is a front view of a current sensor according to another modified example. FIG. 7H is a cross-sectional view showing an enlarged view of the busbar and the busbar through hole in the current sensor of FIG. 7A. FIG. 7I is a front view of a current sensor according to another modified example. FIG. 7I is a front view of a current sensor according to a second embodiment. FIG. 7I is a side view of a current sensor according to the second embodiment. FIG. 7I is a side view and a graph explaining the relationship between the position of a magnetic detection unit in the current sensor and magnetic flux density. FIG. 7I is a vector diagram showing simulation results of magnetic fields generated in an energized phase and an adjacent phase by current flowing through the busbar of the energized phase. FIG. 7I is a front view of a current sensor according to a modified example. FIG. 7I is a side view of a current sensor according to a modified example. 10A and 10B are side views of a current sensor according to another modified example, a side view of a current sensor according to another modified example, a front view of a conventional current sensor, and a side view of a conventional current sensor.

[0021] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The same components in each drawing are designated by the same reference numerals, and their description will be omitted. Reference coordinates are shown in each drawing as appropriate to indicate the positional relationship of each component. The reference coordinates are defined as the X direction, which is the direction in which the end faces defining the first gap of the core member face each other; the Y direction, which is the direction perpendicular to the X direction on the detection surface of the magnetic detector; and the Z direction, which is the direction of the central axis of the ring of the core member.

[0022] 1A and 1B are front and side views of a current sensor 1 according to this embodiment. The current sensor 1 includes a core member 2 and a magnetic detector 3. The core member 2 is made of a magnetic material and has a first gap 22 between end faces 21. The core member 2 is formed in an annular shape that allows a bus bar 4 to pass through. When a current to be measured flows through the bus bar 4, the magnetic field generated by the bus bar 4 is collected in the first gap 22, and the magnetic field in the first gap 22 is detected by the magnetic detector 3. Note that the following embodiments describe an embodiment in which the bus bar 4 passes through the core member 2. However, the present invention can also be implemented in an embodiment in which a conductor other than the bus bar 4 passes through the core member 2. In this case, the current sensor 1 measures the current to be measured flowing through the conductor. The core member 2 may be formed by stacking multiple annular plates in the Z direction, with the Z direction being the plate thickness direction.

[0023] The magnetic detector 3 detects a magnetic field across the first gap 22 that is generated when a current to be measured flows through the bus bar 4. The magnetic detector 3 is spaced apart from the bus bar 4 in the Y direction and is disposed so that its detection surface 31 is perpendicular to the plate surface of the bus bar 4. The bus bar 4 is made of a conductive material such as copper, brass, or aluminum, through which the current to be measured flows. The bus bar 4 is formed in a plate shape and is disposed so as to penetrate the core member 2, which is formed in an annular shape. Note that, although the bus bar 4 is plate-shaped in this embodiment, it is not limited to a plate shape. For example, the cross-sectional shape of the bus bar 4 parallel to the X-Y plane may be circular.

[0024] 16A and 16B are a plan view and a front view of a conventional current sensor 100. The current sensor 100 includes a Hall element 103 as a magnetic detection unit that detects the magnetic field across the first gap 22. A detection surface 131 of the Hall element 103 and an end surface 21 of the first gap 22 of the core member 2 are disposed opposite each other. Because the area of ​​the end surface 21 of the first gap 22 needs to be approximately the same as the area of ​​the detection surface 131 of the Hall element 103, it has been difficult to make the current sensor 100 smaller and thinner.

[0025] 1A and 1B, in the current sensor 1 of this embodiment, the detection surface 31 of the magnetic detection unit 3 can detect magnetic field components parallel to the detection surface 31. The detection surface 31 is arranged parallel to the direction in which the two end faces 21 that form the first gap 22 face each other, so that the sensitivity direction is the X direction and parallel to the XY plane.

[0026] With this configuration, in the current sensor 1, it is not necessary to adjust the size of the end surface 21 of the core member 2 that defines the first gap 22 to match the size of the detection surface 31 of the magnetic detection unit 3. Therefore, when the current flowing through the bus bar 4 is small, the height of the core member 2 in the Z direction can be reduced. On the other hand, when the current flowing through the bus bar 4 is large, this can be accommodated by increasing the width in the X direction without increasing the height of the core member 2.

[0027] The magnetic detector 3 is mounted on a substrate 5 made of epoxy glass, ceramic, etc. A surface 51 of the substrate 5, which is parallel to the XY plane, is perpendicular to the end surface 21 of the core member 2, which is parallel to the XZ plane.

[0028] A current sensor that is resistant to vibrations can be obtained by mounting the magnetic detector 3 on the substrate 5 in a planar manner, i.e., by providing the magnetic detector 3 so that the detection surface 31 is parallel to the plate surface 51 of the substrate 5. When the magnetic detector 3 includes a magnetoresistive effect element such as a GMR element or a TMR element as a detection element, it can be planarly mounted on the substrate 5.

[0029] 16A, a conventional current sensor 100 has a Hall element 103 as a magnetic detection unit attached to a holding member 105 that is long in the Y direction. Therefore, when vibration is applied to the current sensor 100, the position of the Hall element 103 may change, as indicated by the dashed line in the figure. If the position of the Hall element 103 changes, the detection surface 131 will be tilted with respect to the detection magnetic field in the direction facing the end face 21 (X direction), and the detection accuracy of the current sensor 100 will decrease.

[0030] In contrast, in the current sensor 1 of this embodiment, the magnetic detector 3 is planar-mounted on the substrate 5. Therefore, tilt of the detection surface 31 relative to the detection magnetic field can be suppressed without providing any components or structures to hold the magnetic detector 3. Furthermore, even when vibration is applied to the current sensor 1, the position of the magnetic detector 3 is unlikely to shift in a direction parallel to the plate surface 51 of the substrate 5. Even if the substrate 5 momentarily bends in the Z direction, the detection surface 31 does not tilt relative to the detection magnetic field. In other words, when no vibration is applied to the current sensor 1, the direction of the magnetic field generated in the first gap 22 is the X direction, and the direction in which the magnetic detector 3 can detect magnetic components at this time is also the X direction. When vibration is applied to the current sensor 1 and the substrate 5 bends in the Z direction, the position of the detection surface 31 of the magnetic detector 3 shifts along the side of a cylinder centered on an imaginary axis parallel to the X direction, while maintaining the sensitivity axis in the X direction. As a result, the detection surface 31 is in a state equivalent to being rotated about an imaginary axis parallel to the X direction from the position before the substrate 5 was bent in the Z direction. In other words, the magnetic component that can be detected by the magnetic detection unit 3 remains the magnetic component in the X direction. Therefore, it is possible to reduce the deterioration of the detection accuracy of the current sensor 1 due to vibration.

[0031] 2 is a perspective view of the core member 2 in a modified example of the current sensor 1. By engaging the core member 2 with the substrate 5, the positional relationship between the magnetic detector 3 provided on the substrate 5 and the core member 2 is stabilized. This makes it possible to prevent differences in the detection accuracy of the current sensor 1 from occurring due to differences in the relative positions of the magnetic detector 3 and the core member 2.

[0032] 2, the core member 2 and the substrate 5 are locked together by inserting the protrusion 23 of the core member 2 into the hole 52 of the substrate 5. However, the method of integrating the core member 2 and the substrate 5 is not limited to this. For example, there are a method of bonding the core member 2 and the substrate 5 together, a method of stacking the core member 2 and the substrate 5 by heating and pressurizing them in a vacuum, a method of plating the core member 2 and soldering it to the substrate 5, a method of crimping a pin into the core member 2 and soldering the pin to the substrate 5, and the like.

[0033] 3 is a plan view of a current sensor 1a according to another modification. The current sensor 1a shown in the figure differs from the current sensor 1 in that it includes a core member 2a having a second gap 25 different from the first gap 22. Note that the positional relationship between the core member 2a, magnetic detector 3, detection surface 31, bus bar 4, and substrate 5 when viewed in the Y direction is the same as that of the current sensor 1 shown in FIG. 1B.

[0034] By configuring the core member 2a to be divided, it is possible to measure a larger current to be measured using the same magnetic detector 3 and substrate 5 as when measuring a small current to be measured. In the case of a divided core member 2a, it is preferable to integrate the core member 2a and substrate 5 from the viewpoint of stabilizing the positional relationship between the core member 2a and the magnetic detector 3 (see FIG. 2).

[0035] The second gap 25 and the first gap 22 are formed on opposite sides of the core member 2a in the Y direction. The distance between the opposing end faces 24 that defines the second gap 25 is smaller than the distance between the opposing end faces 21 that defines the first gap 22. The distance between the end faces 24 and the distance between the end faces 21 may be set according to the magnitude of the current to be measured, and may be, for example, about 0.5 to 3 mm for the distance between the end faces 24 and about 3 to 10 mm for the distance between the end faces 21.

[0036] <Measurement Example> Measurements were performed using the current sensor 1 shown in Fig. 1A and the current sensor 1a shown in Fig. 3, with currents to be measured of different magnitudes flowing through the busbar 4. The magnetic flux densities detected by the magnetic detection unit 3 are shown in Table 1. The distance between the end faces 21 of the first gap 22 in the current sensor 1 and the current sensor 1a was 9 mm, and the distance between the end faces 24 of the second gap 25 in the current sensor 1a was 1 mm. As shown in Table 1, by using the divided core member 2a, it is possible to adjust the magnetic flux density of the magnetic field detected by the magnetic detector 3. Therefore, it is possible to adjust the measurable range of the current sensor.

[0037] 4 is an exploded perspective view of the current sensor 1. As shown in the figure, the current sensor 1 has a housing 6 that houses the core member 2, the magnetic detector 3, and the substrate 5. The housing 6 has a bus bar through hole 61 through which the bus bar 4 can be inserted. In the current sensor 1, the magnetic detector 3 measures the current to be measured flowing through the bus bar 4 in a state in which the bus bar 4 is inserted into the bus bar through hole 61 that is provided so as to penetrate the inside of the ring formed by the core member 2.

[0038] Fig. 5A is a front view of a current sensor 1b according to another modification. Fig. 5B is an enlarged cross-sectional view of the busbar 4 and busbar through hole 61b of the current sensor 1b in Fig. 5A, taken along line AA in Fig. 4, in an assembled state. As shown in these figures, the cross section of the busbar through hole 61b in the XY plane is a rectangle elongated in the X direction, with the two end faces 21 that define the first gap 22 facing each other. This reduces the effect of misalignment of the busbar 4 inserted into the busbar through hole 61b on the measurement sensitivity of the current sensor 1b.

[0039] Fig. 6 is a graph showing the effect of misalignment of the bus bar 4 on the sensitivity of the current sensor 1b according to the modification of Fig. 5A. The graph shows the sensitivity variation rate of the current sensor 1b when the bus bar 4 is misaligned in the X direction, Y direction, or XY direction from a predetermined position where the center O4 of the bus bar 4 and the center O61b of the bus bar through hole 61b are aligned.

[0040] 6, when the bus bar 4 is misaligned in the X direction, the influence of the misalignment on the sensitivity of the current sensor 1b is small. In contrast, when the bus bar 4 is misaligned in the Y direction or the XY direction (see FIG. 5A), the influence of the misalignment on the sensitivity of the current sensor 1b is large.

[0041] 5A and 5B , the cross-sectional shape of the busbar through hole 61b in the housing 6b has a first marginal width MX in the X direction that is larger than a second marginal width MY in the Y direction. That is, when the busbar 4 is inserted into a predetermined position in the busbar through hole 61b, the first marginal width MX in the X direction, in which the end faces 21 that define the first gap 22 face each other, is larger than the second marginal width MY in the Y direction that is perpendicular to the direction in which the end faces 21 face each other.

[0042] Providing the first margin width MX and the second margin width MY in the busbar through hole 61b makes it easier to insert the busbar 4 into the busbar through hole 61b. Furthermore, even if the position of the busbar 4 in the busbar through hole 61b deviates from the predetermined position, the direction of the deviation is the X direction, which has the least effect on the sensitivity of the current sensor 1b. Therefore, even if the busbar 4 deviates from the predetermined position, the current sensor 1b can have the predetermined sensitivity.

[0043] FIG. 7A is a front view of a current sensor 1c according to another modification. FIG. 7B is an enlarged cross-sectional view of the busbar 4 and busbar through-hole 61c of the current sensor 1c in an assembled state, taken along line AA in FIG. 4 . Current sensor 1c differs from current sensor 1b in that the busbar 4 is integrally held in a housing 6c, which also integrally holds the core member 2a, the magnetic detector 3, and the substrate 5. For example, the busbar 4 can be integrally held in the housing 6c by integrally forming a portion of the busbar 4 with the housing 6c by insert molding. The current sensor 1c and current sensor 1b share the same configuration in which the busbar 4 penetrates the inside of the ring formed by the core member 2a. By integrally holding the busbar 4 in the housing 6c, misalignment between the center O61c of the busbar through-hole 61c and the center O4 of the busbar 4 can be reduced, making it less likely that sensitivity fluctuations due to misalignment of the busbar 4, as shown in FIG. 6, will occur.

[0044] 8 is a front view of a current sensor 1d according to another modification. The current sensor 1d differs from the current sensor 1 of FIG. 1A in that the magnetic detector 3 is disposed at a position offset with respect to the first gap 22 when viewed in the Z direction, which is the direction along the central axis of the ring of the core member 2 and the extension direction of the bus bar 4. That is, the magnetic detector 3 of the current sensor 1d is disposed at a position where the X-direction center line C2 passing through the center of the width of the magnetic detector 3 in the Y direction is offset from the X-direction center line C1 passing through the center of the width of the two end faces 21 forming the first gap 22 in the Y direction.

[0045] By configuring the magnetic detector 3 to be offset from the center of the first gap 22, it is possible to measure a larger current to be measured using the same core member 2, magnetic detector 3, and substrate 5 as when measuring a small current to be measured. The distance in the Y direction between the center lines C1 and C2 may be set according to the magnitude of the current to be measured, and may be, for example, about 1 to 10 mm.

[0046] The magnetic detector 3 is positioned so that at least a portion of it overlaps with the first gap 22 when viewed in the Z direction, so that the magnetic field formed in the first gap 22 formed by the two end faces 21 can be measured with high accuracy.

[0047] <Measurement Example> Measurements were performed using the current sensor 1 shown in Fig. 1A and the current sensor 1d shown in Fig. 8, with currents to be measured of different magnitudes flowing through the busbar 4. The magnetic flux densities of the magnetic fields detected by the magnetic detection unit 3 in these measurements are shown in the table below. The distance between the end faces 21 of the first gap 22 in the current sensor 1 and the current sensor 1d was 9 mm, and the end faces 21 were squares with sides of 15 mm. The distance in the Y direction between the center line C1 and the center line C2 in the current sensor 1d was 5 mm.

[0048] As shown in Table 2, by positioning the magnetic detector 3 so as not to deviate from the center of the first gap 22 in the Y direction, it is possible to adjust the magnetic flux density of the magnetic field detected by the magnetic detector 3. Therefore, the above configuration makes it easier to replace the Hall sensor used as the magnetoresistive effect element of the magnetic detector 3 with a magnetoresistive effect element having a narrower dynamic range than the Hall sensor.

[0049] Second Embodiment Fig. 9 is a front view showing the temperature of the core member 2 with shading when a current is applied to the bus bar 4. As shown in the figure, when a current to be measured flows through the bus bar 4, the bus bar 4 generates heat. The heat generated at this time is called thermal heat. The larger the current to be measured, the higher the thermal heat becomes. Due to the influence of the thermal heat from the bus bar 4, the first gap 22 of the core member 2 becomes almost the same temperature as the core member 2, and the space in the first gap 22 also becomes hot. Therefore, in the current sensor of this embodiment, the magnetic detection unit 3 is disposed outside the first gap 22 to suppress the influence of the thermal heat from the bus bar 4 that passes through the core member 2.

[0050] 10A and 10B are front and side views of a current sensor 1e according to this embodiment. The magnetic detection unit 3 of the current sensor 1e is disposed outside the first gap 22. As shown in FIG. 10B , the current sensor 1e differs from the current sensor 1 in that, when viewed in the Y direction, the magnetic detection unit 3 is disposed at a position offset in the Z direction from the position of the first gap 22 sandwiched between the end faces 21. In the current sensor 1e, the magnetic detection unit 3 is planar-mounted on the substrate 5, and the plate surface 51 of the substrate 5 and the end face 21 that forms the first gap 22 are orthogonal to each other. Furthermore, when viewed in a direction orthogonal to the detection surface 31, i.e., the Z direction, the magnetic detection unit 3 is disposed so as to overlap the first gap 22. The configuration of the current sensor 1e is similar to that of the current sensor 1.

[0051] 11 is an explanatory diagram illustrating the relationship between the position of the magnetic detector 3 and the magnetic flux density in the current sensor 1d. As shown in the figure, the current sensor 1e has the magnetic detector 3 disposed outside the region of the first gap 22 indicated in gray in FIG. 11, which makes it possible to suppress the effect on the magnetic detector 3 of the heat generated by Joule heat generated in the busbar 4 when current is applied. Therefore, the current sensor 1e has excellent detection accuracy and durability, with detection errors due to temperature drift of the magnetic detector 3 suppressed.

[0052] Furthermore, when the current to be measured flowing through the busbar 4 is large, the magnetic flux density in the region within the first gap 22 may exceed the upper limit detectable by the magnetic detector 3. Depending on the magnitude of the current to be measured flowing through the busbar 4, the magnetic flux density may also exceed the upper limit detectable by the magnetic detector 3 in a region outside the first gap 22 near the side surface 26 of the core member 2, as illustrated in the graph shown in FIG. 11 . Therefore, in the current sensor 1d, the magnetic detector 3 is disposed in a region where the magnetic flux density is equal to or less than the upper limit detectable by the magnetic detector 3 when the current to be measured in the busbar 4 to be detected reaches its maximum value. That is, the detection surface 31 of the magnetic detector 3 is disposed at a position at least a distance from the side surface 26 of the core member 2 at which the magnetic flux density is equal to or less than the upper limit detectable by the magnetic detector 3. This arrangement enables the current sensor 1e to handle large currents.

[0053] If the distance from the side surface 26 of the core member 2 to the detection surface 31 at which the magnetic flux density reaches the upper limit of detection in the direction along the central axis of the ring of the core member 2 (Z direction) is D, then the distance Dz from the side surface of the core member 2 to the detection surface 31 is preferably 1.0D to 1.5D, more preferably 1.0D to 1.3D, and even more preferably 1.0D to 1.2D. With this configuration, it is possible to provide a current sensor 1e that is capable of handling large currents and has excellent detection accuracy.

[0054] 12 is a vector diagram showing the simulation results of the magnetic field generated in the energized phase and the adjacent phase when current flows only through the busbar 4 of the energized phase and not through the busbar 4 of the adjacent phase, and shows a current sensor 1f having multiple measurement phases. When the current sensor 1f has multiple measurement phases each having a core member 2 and a magnetic detector 3, it is preferable to suppress the influence on the adjacent phase in order to improve the detection accuracy of the magnetic field.

[0055] In the current sensor 1f, the magnetic detector 3 is disposed outside the first gap 22, in the Z direction (upper side of the paper in FIG. 12 ). That is, when viewed in the Y direction (perpendicular to the X direction) in which the two end faces 21 forming the first gap 22 face each other, the detection surface 31 of the magnetic detector 3 is shifted relative to the first gap 22 in the Z direction along the central axis of the ring of the core member. Furthermore, when viewed in the Z direction, the detection surface 31 of the magnetic detector 3 is disposed so as to overlap the first gap 22 (see FIG. 10A ). In the region where the magnetic detector 3 is disposed in the adjacent phase, the magnetic field generated from the adjacent energized phase is oriented in the Z direction. The magnetic detector 3 of the adjacent phase, which detects the X-direction magnetic field generated near the first gap 22, has a sensitivity direction in the X direction. In this way, the magnetic detector 3 disposed in the adjacent phase is less susceptible to the influence of the adjacent energized phase because the magnetic field from the adjacent energized phase is oriented perpendicular to the sensitivity direction. 12, in the region of the energized phase where the magnetic detector 3 is located, the direction of the magnetic field generated from the adjacent phase is in the Z direction. Therefore, by locating the magnetic detector 3 at a position offset in the Z direction from the first gap 22, the influence of the magnetic field from the adjacent phase is suppressed, resulting in a multiphase current sensor 1f with good magnetic field detection accuracy.

[0056] 13A and 13B are front and side views of a current sensor 1g according to a modified example. Current sensor 1g differs from current sensor 1e shown in FIGS. 10A and 10B in that a grounded substrate 5 is disposed between core member 2 and magnetic detector 3. That is, magnetic detector 3 is planar-mounted on one surface 51A of substrate 5, and the other surface 51B of substrate 5 faces side surface 26 of core member 2. This configuration allows electromagnetic noise picked up by core member 2 to be shielded by solid GND surface 53 provided on substrate 5, resulting in current sensor 1g with excellent noise resistance.

[0057] 14 is a front view of a current sensor 1h according to another modification. In the current sensor 1h, a sub-magnetic detector 3S is arranged on a surface 51B of the substrate 5 opposite to a surface 51A on which the magnetic detector 3 is arranged. By mounting the magnetic detector 3 and the sub-magnetic detector 3S on both surfaces of the substrate 5 for duplication, redundancy is improved, and even if a problem occurs in the function of the magnetic detector 3, measurements can be made using the sub-magnetic detector 3S.

[0058] A magnetoresistive element can be used as the detection element of the sub-magnetic detection unit 3S of the current sensor 1h. As with the magnetic detection unit 3, by arranging the sub-magnetic detection unit 3S outside the first gap 22 of the core member 2, the influence of the heat generated by the bus bar 4 can be reduced.

[0059] 15 is a front view of a current sensor 1i according to another modification. As shown in the figure, a Hall sensor can be used as the detection element of the sub-magnetic detection unit 3S. When a Hall sensor is used as the detection element of the sub-magnetic detection unit 3S, the detection element of the sub-magnetic detection unit 3S is disposed within the first gap 22 of the core member 2.

[0060] If a Hall sensor is arranged as a sub-magnetic detection unit 3S on the surface 51B opposite to the surface 51A on which the magnetic detection unit 3 of the substrate 5 is mounted, functional safety can be achieved by redundancy, and the detection element method is different. Because the magnetic detection unit 3 and the sub-magnetic detection unit 3S have different failure modes, simultaneous failures of the magnetic detection unit 3 and the sub-magnetic detection unit 3S are unlikely to occur, resulting in a current sensor 1i with excellent reliability and safety.

[0061] The embodiments disclosed in this specification are illustrative in all respects and are not limited to these embodiments. The scope of the present invention is defined by the claims rather than by the description of the above-described embodiments alone, and is intended to include all modifications within the meaning and scope of the claims.

[0062] The present invention is useful as a current sensor that is attached to various devices to measure a current to be measured in order to control or monitor the devices.

[0063] DESCRIPTION OF SYMBOLS 1, 1a to 1i: Current sensor 2, 2a: Core member 21: End face 22: First gap 23: Convex portion 24: End face 25: Second gap 26: Side face 3: Magnetic detection unit 31: Detection surface 3S: Sub-magnetic detection unit 4: Bus bar 5: Board 51: Plate surface 51A, 51B: Surface 52: Hole 53: Plain surface 6, 6b, 6c: Housing 61, 61b, 61c: Bus bar through hole 100: Current sensor 103: Hall element 105: Holding member 131: Detection surface D, Dz: Distance C1, C2: Center line MX: First margin MY: Second margin O4, O61b, O61c: Center

Claims

1. a core member having a first gap between end surfaces, formed in an annular shape into which a bus bar can be inserted, and configured to collect a magnetic field generated when a current to be measured flows through the bus bar; a magnetic detection unit capable of detecting the magnetic field collected by the core member; A current sensor including a substrate having the magnetic detection unit planarly mounted on one surface thereof, the magnetic detection unit has a detection surface that detects the magnetic field and is capable of detecting a magnetic field component parallel to the detection surface; the detection surface is arranged so as to be parallel to a direction in which the two end surfaces forming the first gap face each other, the magnetic detection unit is disposed outside the first gap, a detection surface that is perpendicular to the detection surface and is disposed so as to overlap with the first gap; a plate surface of the substrate and the end surface of the core member are perpendicular to each other, the substrate has a solid ground surface provided along a surface parallel to the one surface at a location other than the one surface, A current sensor characterized in that the grounded substrate is disposed between the core member, which is not grounded, and the magnetic detection unit, so that the solid surface is disposed as a shield.

2. The current sensor according to claim 1 , wherein the substrate and the core member are anchored together.

3. The current sensor of claim 1 , wherein the core member has a second gap at a different location than the first gap.

4. a housing that contains the magnetic detection unit and the core member, the housing has a bus bar through hole through which the bus bar can be inserted, The bus bar through hole is provided to penetrate an inner side of a ring formed by the core member, 2. The current sensor according to claim 1, wherein a cross-sectional shape of the busbar through hole has a first margin in a direction in which the two end faces forming the first gap face each other, the first margin being larger than a second margin in a direction perpendicular to the direction in which the two end faces face each other.

5. The bus bar is provided so that the current to be measured can flow therethrough. The current sensor according to claim 1 , further comprising a housing that holds the magnetic detection unit, the core member, and the bus bar integrally, the bus bar being disposed to penetrate an inside of a ring formed by the core member.

6. When viewed along the central axis of the ring of the core member, the magnetic detector is disposed at a position offset from a straight line passing through the centers of the two end faces that define the first gap, The current sensor according to claim 1 , wherein at least a portion of the magnetic detection portion is disposed so as to overlap the first gap.

7. The current sensor according to claim 1 , wherein the detection element of the magnetic detection portion is a magnetoresistance effect element.

8. When viewed from a direction perpendicular to a direction in which the end faces forming the first gap face each other on the detection surface, the magnetic detector is disposed in a direction along a central axis of the ring of the core member with respect to the first gap; When viewed from a direction along the central axis of the ring of the core member, The current sensor according to claim 1 , wherein the magnetic detection portion is disposed so as to overlap the first gap.

9. The current sensor according to claim 1 , wherein a sub-magnetic detection portion is disposed on a surface of the substrate opposite to a surface on which the magnetic detection portion is disposed.

10. The current sensor according to claim 9 , wherein the detection element of the sub magnetic detection portion is a magnetoresistance effect element and is disposed outside the first gap of the core member.

11. a detection element of the magnetic detector is a magnetoresistance effect element, the detection element of the sub magnetic detection unit is a Hall sensor, The current sensor of claim 9 , wherein the Hall sensor is disposed in the first gap of the core member.

12. A core member having a first gap sandwiched between end faces, formed in a ring shape through which a bus bar can be inserted, and which collects a magnetic field generated when a current to be measured flows through the bus bar; a magnetic detection unit capable of detecting the magnetic field collected by the core member; In a current sensor comprising: the magnetic detection unit has a detection surface that detects the magnetic field and is capable of detecting a magnetic field component parallel to the detection surface; the detection surface is arranged so as to be parallel to a direction in which the two end surfaces forming the first gap face each other, the magnetic detection unit is disposed outside the first gap, a detection surface that is perpendicular to the detection surface and is disposed so as to overlap with the first gap; When viewed along the central axis of the ring of the core member, the magnetic detection unit is disposed at a position shifted in a direction away from the bus bar with respect to a straight line passing through centers of the two end faces that form the first gap, The current sensor according to claim 1 , wherein at least a portion of the magnetic detection portion is disposed so as to overlap the first gap.