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

Technical Field

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

Background Art

[0002] In recent years, for the control and monitoring of various devices, current sensors are used that are attached to various devices to measure the measured current flowing through the various devices. As this type of current sensor, a current sensor using a magnetoelectric conversion element that senses a magnetic field generated by a measured current flowing through a current path is known. Also known is a current sensor provided with a core member that surrounds the periphery of the current path to facilitate detection of the magnetic field, and a Hall element as a magnetoelectric conversion element provided in a gap of the core member.

[0003] Patent Document 1 describes a current detection device including a magnetic core and a Hall element for the purpose of avoiding a current detection error caused by pressure applied to the magnetic core or the like. Patent Document 2 describes a current detection device including a magnetic core having both ends facing each other through a gap and formed continuously surrounding the periphery of a hollow portion, and a Hall element disposed in the gap for detecting a magnetic flux that changes according to a current passing through the hollow portion, for the purpose of achieving both miniaturization of the magnetic core and suppression of deterioration in detection accuracy caused by noise magnetic lines.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Disclosure of the Invention

Problems to be Solved by the Invention

[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 unstable. Therefore, a structure and components are needed that can stably maintain the position of the Hall element when the current detection device vibrates. Furthermore, since the Hall element detects a magnetic field perpendicular to its detection surface, the detection surface of the Hall element and the end face of the gap in the core member must be positioned facing each other. Consequently, the end face defining the gap must have an area approximately the same as that of the detection surface of the Hall element. For these reasons, it has been difficult to miniaturize and thin the current detection device. Therefore, the present invention aims to provide a current sensor that can stably maintain the position of the magnetoelectric conversion element even when vibration occurs, and is suitable for miniaturization and thinning. [Means for solving the problem]

[0006] The present invention provides the following configuration as a means for solving the above-mentioned problems. A current sensor comprising: a core member formed in an annular shape through which a busbar can be inserted, having a first gap sandwiched between end faces, and which collects a magnetic field generated when a current to be measured flows through the busbar; and a magnetic detection unit capable of detecting the magnetic field collected by the core member, wherein the magnetic detection unit has a detection surface for detecting the magnetic field, is capable of detecting a magnetic field component parallel to the detection surface, and is arranged such that the detection surface is parallel to the direction in which the two end faces forming the first gap face each other. This configuration eliminates the need to match the size of the end face of the first gap to the size of the detection surface of the magnetic sensor, thus allowing the height of the core member to be kept low.

[0007] The magnetic detection unit is mounted on a substrate in a planar manner, and the surface of the substrate and the end face of the core member may be perpendicular to each other. This configuration ensures that even when vibrations are applied to the magnetic sensor, the position of the magnetic detection unit is less likely to shift in a direction parallel to the substrate surface, and even if the substrate flexes, the detection surface will not tilt relative to the detection magnetic field. Therefore, it is possible to suppress the decrease in detection accuracy due to vibration without providing structures or components to stably maintain 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 detection unit and the core member, thereby reducing detection errors caused by mounting position errors.

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

[0010] The current sensor has a housing that encloses the magnetic detection unit and the core member, the housing has a busbar through-hole through which the busbar can be inserted, the busbar through-hole is provided penetrating the inside of the ring formed by the core member, and the cross-sectional shape of the busbar through-hole may be such that the first clearance width in the direction in which the two end faces that form the first gap face each other is greater than the second clearance width in the direction perpendicular to the direction in which the two end faces face each other. By providing first and second clearance widths, it becomes easier to insert the busbar into the busbar through-hole. Furthermore, by making the first clearance width larger than the second clearance width, a current sensor can be made that exhibits minimal deviation in measurement sensitivity even when the busbar is mounted off-center from the busbar through-hole.

[0011] The current sensor has a busbar capable of carrying the current to be measured, the busbar is positioned to penetrate the inside of the ring formed by the core member, and the sensor may have a housing that integrally holds the magnetic detection unit, the core member, and the busbar. By integrally forming the busbar and the housing, misalignment between the busbar and the housing can be prevented, 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 sensing portion is positioned offset from a straight line passing through the centers of the two end faces that form the first gap, and at least a portion of the magnetic sensing portion may be positioned to overlap with the first gap. This configuration reduces the detection magnetic field generated by the current being measured, thereby widening the range of currents that can be measured by the current sensor.

[0013] The detection element of the magnetic detection unit may be a magnetoresistive element. By using a magnetoresistive element, the sensing surface can be positioned so that the two end faces forming the first gap are parallel to each other, which is advantageous for miniaturizing the current sensor.

[0014] The magnetic detection unit may be positioned outside the first gap and overlap the first gap when viewed from a direction perpendicular to the detection surface. This configuration mitigates the effect of heat generated by the busbar when the measured current flows on the magnetic sensing element, 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 on the sensing surface are facing each other, the magnetic sensing portion may be positioned offset from the first gap in a direction along the central axis of the ring of the core member, and when viewed from a direction along the central axis of the ring of the core member, the magnetic sensing portion may be positioned to overlap with the first gap. This configuration reduces the influence from adjacent measurement phases when the current sensor has multiple measurement phases, because the magnetic field from adjacent measurement phases contains a large component perpendicular to the sensitivity direction of the detection unit. As a result, the detection accuracy of the current sensor is improved.

[0016] A substrate grounded between the core member and the magnetic detection unit may be disposed. With this configuration, when the core member receives electromagnetic noise, the electromagnetic noise can be shielded by the GND of the substrate, so that the noise resistance of the current sensor is improved.

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

[0018] The detection element of the magnetic detection unit is a magnetoresistive effect element, the detection element of the sub-magnetic detection unit is a Hall sensor, and the Hall sensor may be disposed within the first gap of the core member. By configuring the magnetic detection unit and the sub-magnetic detection unit with different detection elements, the possibility that problems occur simultaneously in each detection element is reduced. For this reason, the reliability of the current sensor is improved.

Advantages of the Invention

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

Brief Description of the Drawings

[0020] [Figure 1A] It is a front view of a current sensor according to a first embodiment. [Figure 1B] It is a side view of a current sensor according to a first embodiment. [Figure 2] It is a perspective view of a core in a current sensor according to a modification. [Figure 3] This is a front view of a current sensor relating to another modified example. [Figure 4] This is a disassembled perspective view of a current sensor. [Figure 5A] This is a front view of a current sensor relating to another modified example. [Figure 5B] Figure 5A is a magnified cross-sectional view showing the busbar and busbar through-hole in the current sensor. [Figure 6] This graph shows the effect of busbar displacement on sensitivity in a modified current sensor shown in Figure 5A. [Figure 7A] This is a front view of a current sensor relating to another modified example. [Figure 7B] Figure 7A is a magnified cross-sectional view showing the busbar and busbar through-hole in the current sensor. [Figure 8] This is a front view of a current sensor relating to another modified example. [Figure 9] This is a front view showing the temperature of the core member and the first gap when the busbar is energized, indicated by shades of gray. [Figure 10A] This is a front view of the current sensor according to the second embodiment. [Figure 10B] This is a side view of the current sensor according to the second embodiment. [Figure 11] This is a side view and graph illustrating the relationship between the position of the magnetic sensing element in a current sensor and the magnetic flux density. [Figure 12] This vector diagram shows the simulation results of the magnetic fields generated in the energized phase and adjacent phases by the current flowing through the energized phase busbar. [Figure 13A] This is a front view of a modified current sensor. [Figure 13B] This is a side view of a modified current sensor. [Figure 14] This is a side view of a current sensor relating to another modified example. [Figure 15] This is a side view of a current sensor relating to another modified example. [Figure 16A] This is a front view of a conventional current sensor. [Figure 16B] This is a side view of a conventional current sensor. [Best Mode for Carrying Out the Invention]

[0021] Embodiments of the present invention will be described below with reference to the accompanying drawings. In each drawing, the same member is given the same number and its description is omitted. Reference coordinates are shown in each drawing as appropriate to indicate the positional relationship of each member. The reference coordinates are defined as follows: the X direction is the direction in which the end faces defining the first gap of the core member face each other; the Y direction is the direction perpendicular to the X direction at the detection surface of the magnetic detection unit; and the Z direction is the direction of the central axis of the ring of the core member.

[0022] [First Embodiment] Figures 1A and 1B are a front view and a side view of the current sensor 1 according to this embodiment. The current sensor 1 comprises a core member 2 and a magnetic detection unit 3. The core member 2 is made of a magnetic material and has a first gap 22 sandwiched between its end faces 21, and is formed in an annular shape through which the busbar 4 can be inserted. When the current to be measured flows through the busbar 4, the magnetic field generated from the busbar 4 is collected between the first gap 22, and the magnetic field between the first gap 22 is detected by the magnetic detection unit 3. In the following embodiments, the configuration in which the busbar 4 is inserted through the core member 2 will be described, but the present invention can also be carried out in a configuration in which a conductor other than the busbar 4 is inserted through the core member 2. In this case, the current sensor 1 measures the current to be measured flowing through the conductor. Furthermore, the core member 2 may be constructed by stacking multiple annular plate materials in the Z direction, with the Z direction being the thickness direction.

[0023] The magnetic detection unit 3 detects the magnetic field in the first gap 22 that is generated when the current to be measured flows through the busbar 4. The magnetic detection unit 3 is spaced apart from the busbar 4 in the Y direction, and its detection surface 31 is positioned perpendicular to the plate surface of the busbar 4. The busbar 4 is a conductive material, such as copper, brass, or aluminum, through which the current to be measured flows. The busbar 4 is formed in a plate shape and is arranged to penetrate the annularly formed core member 2. In this embodiment, the busbar 4 is described as being plate-shaped, but it is not limited to a plate shape. For example, the cross-sectional shape of the busbar 4 parallel to the XY plane may be circular.

[0024] Figures 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 between the first gap 22. The detection surface 131 of the Hall element 103 and the end face 21 of the first gap 22 of the core member 2 are positioned facing each other. Because the area of ​​the end face 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 miniaturize and thin the current sensor 100.

[0025] In contrast, as shown in Figures 1A and 1B, in the current sensor 1 of this embodiment, the detection surface 31 of the magnetic detection unit 3 is capable of detecting 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 of the detection surface 31 is in the X direction and parallel to the XY plane.

[0026] This configuration eliminates the need for the end face 21 of the core member 2, which defines the first gap 22, to match the size of the detection surface 31 of the magnetic detection unit 3 in the current sensor 1. Therefore, when the current flowing through the busbar 4 is small, the height of the core member 2 in the Z direction can be reduced. Furthermore, when the current flowing through the busbar 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 detection unit 3 is planar mounted on a substrate 5 made of epoxy glass, ceramic, or the like. The surface 51 of the substrate 5, which is parallel to the XY plane, is perpendicular to the end face 21 of the core member 2, which is parallel to the XZ plane.

[0028] By mounting the magnetic detection unit 3 on the substrate 5 in a planar manner, that is, by positioning the magnetic detection unit 3 so that its detection surface 31 is parallel to the surface 51 of the substrate 5, a vibration-resistant current sensor is created. If the magnetic detection unit 3 is equipped with magnetoresistive effect elements such as GMR elements and TMR elements as detection elements, it can be planar mounted on the substrate 5.

[0029] In the conventional current sensor 100 shown in Figure 16A, the Hall element 103, which serves as the magnetic detection unit, is attached to a holding member 105 that is long in the Y direction. Therefore, if vibration is applied to the current sensor 100, the position of the Hall element 103 may change, as shown by the dashed line in the figure. When the position of the Hall element 103 changes, the detection surface 131 tilts with respect to the detection magnetic field in the direction opposite to the end face 21 (X direction), and the detection accuracy of the current sensor 100 decreases.

[0030] In contrast, in this embodiment, the current sensor 1 has the magnetic detection unit 3 mounted planarly on the substrate 5. Therefore, the tilt of the detection surface 31 relative to the detection magnetic field can be suppressed without providing a member or structure to hold the magnetic detection unit 3. Furthermore, even when vibration is applied to the current sensor 1, the position of the magnetic detection unit 3 is unlikely to shift in a direction parallel to the surface 51 of the substrate 5. Also, even if the substrate 5 momentarily bends in the Z direction, the detection surface 31 will 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 in the X direction, and the direction in which the magnetic detection unit 3 can detect magnetic components at this time is also in 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 detection unit 3 shifts along the side surface of a cylinder centered on a virtual axis parallel to the X direction, while maintaining the sensitivity axis in the X direction. Therefore, the detection surface 31 is in a state similar to that of rotating around a virtual axis parallel to the X direction from the position before the substrate 5 bends in the Z direction. In other words, the magnetic component that the magnetic detection unit 3 can detect remains the magnetic component in the X direction. Consequently, the decrease in detection accuracy of the current sensor 1 due to vibration can be reduced.

[0031] Figure 2 is a perspective view of the core member 2 in a modified example of the current sensor 1. By locking the core member 2 to the substrate 5, the positional relationship between the magnetic detection unit 3 provided on the substrate 5 and the core member 2 is stabilized. Therefore, it is possible to suppress differences in the detection accuracy of the current sensor 1 due to differences in the relative positions of the magnetic detection unit 3 and the core member 2.

[0032] Figure 2 shows that the core member 2 and the substrate 5 are locked together and integrated 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, methods include bonding the core member 2 and the substrate 5 together, stacking the core member 2 and the substrate 5 and then heating and pressurizing them in a vacuum to laminate them, plating the core member 2 and soldering it to the substrate 5, or crimping pins onto the core member 2 and then soldering the pins to the substrate 5.

[0033] Figure 3 is a plan view of a current sensor 1a according to another modified example. The current sensor 1a shown in this figure differs from the current sensor 1 in that it has a core member 2a having a second gap 25 that is different from the first gap 22. The positional relationship of the core member 2a, magnetic detection unit 3, detection surface 31, busbar 4, and substrate 5 when viewed in the Y direction is the same as that of the current sensor 1 shown in Figure 1B.

[0034] By configuring the core member 2a in a divided state, it is possible to measure a larger current using the same magnetic detection unit 3 and substrate 5 as when measuring a small current. In the case of a divided core member 2a, it is preferable to integrate the core member 2a and the substrate 5 from the viewpoint of stabilizing the positional relationship between the core member 2a and the magnetic detection unit 3 (see Figure 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 define the second gap 25 is smaller than the distance between the opposing end faces 21 that define the first gap 22. The distances between the end faces 24 and the distance between the end faces 21 can be set according to the magnitude of the current being measured, but for example, the distance between the end faces 24 can be set to about 0.5 to 3 mm and the distance between the end faces 21 to about 3 to 10 mm.

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

[0037] Figure 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 encloses a core member 2, a magnetic detection unit 3, and a substrate 5. The housing 6 has a busbar through-hole 61 through which a busbar 4 can be inserted. The current sensor 1 measures the current to be measured flowing through the busbar 4 using the magnetic detection unit 3 when the busbar 4 is inserted through the busbar through-hole 61 which is provided penetrating the inside of the ring formed by the core member 2.

[0038] Figure 5A is a front view of the current sensor 1b according to another modified example. Figure 5B is a cross-sectional view of the busbar 4 and busbar through-hole 61b of the current sensor 1b in Figure 5A, showing an enlarged view of the portion corresponding to line AA in Figure 4 in its assembled state. As shown in these figures, the cross-section of the busbar through-hole 61b in the XY plane is a rectangle that is long in the X direction, with two end faces 21 that define the first gap 22 facing each other. This makes it possible to suppress the effect of displacement of the busbar 4 inserted into the busbar through-hole 61b on the measurement sensitivity of the current sensor 1b.

[0039] Figure 6 is a graph showing the effect of busbar displacement on sensitivity in a modified current sensor 1b of Figure 5A. This figure shows the sensitivity fluctuation rate of the current sensor 1b when the busbar 4 is shifted in the X direction, Y direction, or XY direction from a predetermined position where the center O4 of the busbar 4 and the center O61b of the busbar through-hole 61b overlap.

[0040] As shown in the graph in Figure 6, when the busbar 4 is misaligned in the X direction, the effect of this misalignment on the sensitivity of the current sensor 1b is small. In contrast, when the busbar 4 is misaligned in the Y direction or the XY direction (see Figure 5A), the effect of this misalignment on the sensitivity of the current sensor 1b is large.

[0041] Therefore, as shown in Figures 5A and 5B, the cross-sectional shape of the busbar through-hole 61b in the housing 6b is such that the first clearance width MX in the X direction is greater than the second clearance 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 clearance width MX in the X direction, where the end faces 21 defining the first gap 22 face each other, is greater than the second clearance width MY in the Y direction, which is perpendicular to the direction in which the end faces 21 face each other.

[0042] By providing a first clearance width MX and a second clearance width MY in the busbar through-hole 61b, insertion of the busbar 4 into the busbar through-hole 61b becomes easier. Furthermore, even if the position of the busbar 4 in the busbar through-hole 61b shifts from its predetermined position, the direction of the shift will be the X direction, which has little effect on the sensitivity of the current sensor 1b. Therefore, even if the busbar 4 shifts from its predetermined position, the current sensor 1b can be made to have the predetermined sensitivity.

[0043] Figure 7A is a front view of a current sensor 1c relating to another modified example. Figure 7B is a cross-sectional view of the busbar 4 and busbar through-hole 61c of the current sensor 1c in Figure 7A, showing an enlarged view of the portion corresponding to line AA in Figure 4 in its assembled state. Current sensor 1c differs from current sensor 1b in that the busbar 4 is integrally held in a housing 6c that integrally holds the core member 2a, magnetic detection unit 3, and substrate 5. For example, the busbar 4 can be integrally held in the housing 6c by integrally forming a part of the busbar 4 with the housing 6c by insert molding. The configuration in which the busbar 4 is positioned penetrating the inside of the ring formed by the core member 2a is the same for both current sensor 1c and current sensor 1b. By integrally holding the busbar 4 in the housing 6c, the 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 for sensitivity fluctuations caused by the misalignment of the busbar 4, as shown in Figure 6, to occur.

[0044] Figure 8 is a front view of the current sensor 1d according to another modified example. The current sensor 1d differs from the current sensor 1 in Figure 1A in that, when viewed in the Z direction, which is the extension direction of the busbar 4 and is along the central axis of the ring of the core member 2, the magnetic detection unit 3 is positioned at a location offset from the first gap 22. Specifically, the magnetic detection unit 3 of the current sensor 1d is positioned such that the center line C2 in the X direction, which passes through the center of the width of the magnetic detection unit 3 in the Y direction, is offset from the center line C1 in the X direction, which passes through the center of the width of the two end faces 21 that form the first gap 22 in the Y direction.

[0045] By arranging the magnetic detection unit 3 offset from the center of the first gap 22, it becomes possible to measure larger currents using the same core member 2, magnetic detection unit 3, and substrate 5 as when measuring small currents. The distance in the Y direction between center line C1 and center line C2 should be set according to the magnitude of the current being measured, but for example, it should be around 1 to 10 mm.

[0046] Since the magnetic detection unit 3 is positioned such that at least a portion of it overlaps with the first gap 22 when viewed in the Z direction, it can accurately measure the magnetic field formed in the first gap 22 formed by the two end faces 21.

[0047] <Measurement Example> Measurements were performed by passing currents of different magnitudes through the busbar 4 using the current sensor 1 shown in Figure 1A and the current sensor 1d shown in Figure 8. The magnetic flux density of the magnetic field detected by the magnetic detection unit 3 in these measurements is shown in the table below. The distance between the end faces 21 of the first gap 22 in current sensor 1 and current sensor 1d was set to 9 mm, and the end face 21 was a square with sides of 15 mm. The distance in the Y direction between the center line C1 and the center line C2 in current sensor 1d was set to 5 mm.

[0048] [Table 2] As shown in Table 2, the magnetic flux density of the magnetic field detected by the magnetic detection unit 3 can be adjusted by not shifting the position of the magnetic detection unit 3 from the center in the Y direction of the first gap 22. Therefore, with the above configuration, it becomes easier to replace the Hall sensor used as the magnetoresistive element of the magnetic detection unit 3 with a magnetoresistive element that has a narrower dynamic range compared to the Hall sensor.

[0049] [Second Embodiment] Figure 9 is a front view showing the temperature of the core member 2 when the busbar 4 is energized, indicated by shades of gray. As shown in the figure, when the current to be measured flows through the busbar 4, the busbar 4 generates heat. The heat generated at this time is called turbulence heat. The turbulence heat becomes higher as the current to be measured increases. Due to the turbulence heat from the busbar 4, the first gap 22 of the core member 2 becomes almost the same temperature as the core member 2, and the space of the first gap 22 also becomes hot. Therefore, in this embodiment, the current sensor has the magnetic detection unit 3 placed outside the first gap 22 in order to suppress the effect of turbulence heat from the busbar 4 via the core member 2.

[0050] Figures 10A and 10B are a front view and a side view of the current sensor 1e according to this embodiment. The magnetic detection unit 3 of the current sensor 1e is located outside the first gap 22. The current sensor 1e differs from the current sensor 1 in that, as shown in Figure 10B, when viewed in the Y direction, the magnetic detection unit 3 is located at a position shifted 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 board surface 51 of the substrate 5 and the end face 21 forming the first gap 22 are perpendicular. Also, when viewed from the direction perpendicular to the detection surface 31, i.e., the Z direction, the magnetic detection unit 3 is positioned to overlap with the first gap 22. These configurations of the current sensor 1e are the same as those of the current sensor 1.

[0051] Figure 11 is an explanatory diagram illustrating the relationship between the position of the magnetic detection unit 3 and the magnetic flux density in the current sensor 1d. As shown in the figure, the current sensor 1e has the magnetic detection unit 3 positioned outside the region of the first gap 22 shown in gray in Figure 11. This suppresses the influence of heat generated by Joule heating in the busbar 4 during energization on the magnetic detection unit 3. Therefore, the current sensor 1e has excellent detection accuracy and durability, with reduced detection errors due to temperature drift in the magnetic detection unit 3.

[0052] Furthermore, when the current being measured flowing through the busbar 4 is large, the magnetic flux density in the region within the first gap 22 may exceed the upper detection limit of the magnetic detection unit 3. Depending on the magnitude of the current being measured flowing through the busbar 4, the magnetic flux density may also exceed the upper detection limit of the magnetic detection unit 3 in the region outside the first gap 22, close to the side surface 26 of the core member 2, as illustrated in the graph shown in Figure 11. Therefore, in the current sensor 1d, the magnetic detection unit 3 is positioned in a region where the magnetic flux density at the maximum value of the current being measured in the busbar 4 to be detected is less than or equal to the upper detection limit of the magnetic detection unit 3. That is, the detection surface 31 of the magnetic detection unit 3 is provided at a distance greater than the distance from the side surface 26 of the core member 2 at which the magnetic flux density falls below the detection limit. This arrangement results in a current sensor 1e that can handle large currents.

[0053] When D is the distance from the side surface 26 of the core member 2 to the detection surface 31 in the direction along the central axis of the ring of the core member 2 (Z direction) where the magnetic flux density reaches the detection limit, 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, a current sensor 1e with excellent detection accuracy capable of handling large currents can be provided.

[0054] Figure 12 is a vector diagram showing the simulation results of the magnetic fields generated in the energized phase and adjacent phases when no current is passed through the adjacent phase busbar 4, and current is passed only through the energized phase busbar 4. It shows a current sensor 1f equipped with multiple measurement phases. When the current sensor 1f has multiple measuring phases, each having a core member 2 and a magnetic detection unit 3, it is preferable to suppress the influence on adjacent phases in order to improve the accuracy of magnetic field detection.

[0055] In the current sensor 1f, the magnetic detection unit 3 is positioned outside the first gap 22, in the Z direction on the upper side of the paper in Figure 12. That is, when viewed in the Y direction perpendicular to the direction (X direction) in which the two end faces 21 forming the first gap 22 are facing each other on the detection surface 31, the detection surface 31 of the magnetic detection unit 3 is positioned offset from the first gap 22 in the direction along the central axis of the ring of the core member (Z direction). Also, when viewed in the Z direction, the detection surface 31 of the magnetic detection unit 3 is positioned to overlap with the first gap 22 (see Figure 10A). In the region where the magnetic detection unit 3 is positioned in an adjacent phase, the direction of the magnetic field generated from the adjacent energized phase is in the Z direction. The magnetic detection unit 3 of the adjacent phase that detects the magnetic field in the X direction generated near the first gap 22 has a sensitivity direction in the X direction. Thus, in the magnetic detection unit 3 positioned in an adjacent phase, the magnetic field from the adjacent energized phase is in a direction perpendicular to the sensitivity direction, so it is less susceptible to influence from the adjacent energized phase. Furthermore, when current is passed through the adjacent phase as shown in Figure 12, in the region where the magnetic detection unit 3 is located during the energized phase, the direction of the magnetic field generated from the adjacent phase will be in the Z direction. Therefore, by positioning the magnetic detection unit 3 at a location offset in the Z direction from the first gap 22, the influence of magnetic fields from adjacent phases is suppressed, resulting in a multiphase type current sensor 1f with good magnetic field detection accuracy.

[0056] Figures 13A and 13B are a front view and a side view of a modified current sensor 1g. Current sensor 1g differs from current sensor 1e shown in Figures 10A and 10B in that a grounded substrate 5 is placed between the core member 2 and the magnetic detection unit 3. Specifically, the magnetic detection unit 3 is planar mounted on one side 51A of the substrate 5, and the other side 51B of the substrate 5 faces the side surface 26 of the core member 2. With this configuration, electromagnetic noise picked up by the core member 2 can be shielded by the solid ground surface 53 of the substrate 5, resulting in current sensor 1g with excellent noise immunity.

[0057] Figure 14 is a front view of a current sensor 1h relating to another modified example. The current sensor 1h has a sub-magnetic detection unit 3S located on the opposite side 51B of the substrate 5 from the side 51A where the magnetic detection unit 3 is located. By mounting the magnetic detection unit 3 and the sub-magnetic detection unit 3S on both sides of the substrate 5 to create redundancy, redundancy is improved, and even if a problem occurs with the function of the magnetic detection unit 3, measurement can still be performed by the sub-magnetic detection unit 3S.

[0058] A magnetoresistive element can be used as the detection element for the sub-magnetic detection unit 3S of the current sensor 1h. Similar to the magnetic detection unit 3, by arranging the sub-magnetic detection unit 3S outside the first gap 22 of the core member 2, the effect of heat generated by the busbar 4 can be reduced.

[0059] Figure 15 is a front view of a current sensor 1i according to another modified example. 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 for the sub-magnetic detection unit 3S, the detection element of the sub-magnetic detection unit 3S is placed in the first gap 22 of the core member 2.

[0060] If a Hall sensor is positioned as a sub-magnetic detection unit 3S on the opposite side 51B of the substrate 5 from the side 51A on which the magnetic detection unit 3 is mounted, it becomes possible to implement functional safety through redundancy, and the detection element types are different. Since the magnetic detection unit 3 and the sub-magnetic detection unit 3S have different failure modes, it is unlikely that the magnetic detection unit 3 and the sub-magnetic detection unit 3S will fail simultaneously, resulting in a current sensor 1i with excellent reliability and safety.

[0061] The embodiments disclosed herein are illustrative in all respects and are not limited thereto. The scope of the invention is indicated by the claims rather than solely by the above-described embodiments, and all modifications within the meaning and scope equivalent to the claims are intended. [Industrial applicability]

[0062] The present invention is useful as a current sensor that can be attached to various devices to measure the current being measured, for the purpose of controlling and monitoring various devices. [Explanation of Symbols]

[0063] 1, 1a~1i: Current sensor 2, 2a: Core member 21: End face 22: The first gap 23: Convex part 24: End face 25: The second gap 26: Side view 3: Magnetic detection unit 31: Detection surface 3S: Sub-magnetic detection unit 4: Busba 5: Circuit board 51: Board surface 51A, 51B: Surface 52: Hole 53: Solid surface 6, 6b, 6c: Enclosure 61, 61b, 61c: Busbar through-holes 100: Current sensor 103: Hall element 105: Retaining 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 sandwiched between end faces, formed in an annular shape through which a busbar can be inserted, and which collects the magnetic field generated when the current to be measured flows through the busbar, A magnetic detection unit capable of detecting the magnetic field collected by the core member, A current sensor comprising a substrate on which the magnetic detection unit is planar mounted on one side, The magnetic detection unit has a detection surface for detecting the magnetic field, and is capable of detecting magnetic field components parallel to the detection surface. The detection surface is arranged such that it is parallel to the direction in which the two end faces that form the first gap face each other. The magnetic detection unit is located outside the first gap. When viewed from a direction perpendicular to the detection surface, it is arranged to overlap with the first gap, The plate surface of the substrate and the end surface of the core member are perpendicular to each other. The substrate has a grounding surface provided along a surface parallel to the one surface, in addition to the one surface. A current sensor characterized in that the grounded substrate is placed between the ungrounded core member and the magnetic detection unit, so that the solid surface acts as a shield.

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

3. The current sensor according to claim 1, wherein the core member has a second gap at a position different from the first gap.

4. The housing includes the magnetic detection unit and the core member, The housing has a busbar through hole through which the busbar can be inserted, The busbar through-hole is provided penetrating the inside of the ring formed by the core member, The current sensor according to claim 1, wherein the cross-sectional shape of the busbar through-hole is such that the first clearance width in the direction in which the two end faces forming the first gap face each other is greater than the second clearance width in the direction perpendicular to the direction in which the two end faces face each other.

5. The busbar has the aforementioned current to be measured and is capable of carrying the current, The current sensor according to claim 1, wherein the busbar is positioned to penetrate the inside of the ring formed by the core member, and the sensor has a housing that integrally holds the magnetic detection unit, the core member, and the busbar.

6. When viewed along the direction of the central axis of the ring of the core member, The magnetic detection unit is positioned at a location offset from the straight line passing through the 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 unit is arranged to overlap with the first gap.

7. The current sensor according to claim 1, wherein the detection element of the magnetic detection unit is a magnetoresistive element.

8. When viewed from a direction perpendicular to the direction in which the end faces forming the first gap in the detection surface are facing each other, The magnetic detection unit is positioned relative to the first gap in a direction along the central axis of the ring of the core member. 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 unit is arranged to overlap with the first gap.

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

10. The current sensor according to claim 9, wherein the detection element of the sub-magnetic detection unit is a magnetoresistive element and is located outside the first gap of the core member.

11. The detection element of the magnetic detection unit is a magnetoresistive element. The detection element of the sub-magnetic detection unit is a Hall sensor, The current sensor according to claim 9, wherein the Hall sensor is disposed within the first gap of the core member.

12. A core member having a first gap sandwiched between end faces, formed in an annular shape through which a busbar can be inserted, and which collects the magnetic field generated when a current to be measured flows through the busbar, A magnetic detection unit capable of detecting the magnetic field collected by the core member, In a current sensor equipped with, The magnetic detection unit has a detection surface for detecting the magnetic field, and is capable of detecting magnetic field components parallel to the detection surface. The detection surface is arranged such that it is parallel to the direction in which the two end faces that form the first gap face each other. The magnetic detection unit is located outside the first gap. When viewed from a direction perpendicular to the detection surface, it is arranged to overlap with the first gap, When viewed along the direction of the central axis of the ring of the core member, The magnetic detection unit is positioned at a location offset away from the busbar with respect to a straight line passing through the 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 unit is arranged to overlap with the first gap.

Images