Current sensor

Abstract

To provide a current sensor capable of effectively detecting a low current.SOLUTION: A bus bar 11 of a current sensor 1 includes: a first current-carrying portion 111 in which a pair of first linear portions 111a arranged along each other is connected so that a current I flows in directions opposite to each other; a second current-carrying portion 112 in which a pair of second linear portions 112a arranged along each other is connected so that the current I flows in the directions opposite to each other, and a first gap 111c and a second gap 112c are arranged to face each other; and a connecting portion 113 that connects the first gap 111c and the second gap 112c in a single-stroke shape so that a magnetic flux passes from one to the other of the gaps. A sensor portion 12 includes a hall element 121 that detects the current I through the magnetic flux.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a current sensor that uses a Hall element to detect the current of an object to be measured. [Background technology]

[0002] Conventionally, current sensors that use a Hall element to detect the current of a measurement target are known (see, for example, Patent Document 1). In many cases, current sensors such as those described in Patent Document 1 cause the current to be measured to flow through a bus bar, and detect the current via a magnetic flux generated when the current flows through the bus bar using a Hall element disposed near the bus bar. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-232246 Summary of the Invention [Problem to be solved by the invention]

[0004] Here, in the current sensor using the bus bar and Hall element described above, the magnetic flux generated around the bus bar is small, and when trying to measure a low current, the generated magnetic flux may fall below the lower detection limit of the Hall element, making detection difficult.

[0005] Therefore, the present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a current sensor that can effectively detect low currents. [Means for solving the problem]

[0006] In order to solve the above problem, a current sensor includes a bus bar formed of a conductive metal and through which a current to be measured flows, and a sensor unit that detects the current flowing through the bus bar, wherein the bus bar includes a first current-carrying portion in which a pair of first linear portions arranged along each other are connected at their ends so that the current flows in opposite directions, and a pair of second linear portions arranged along each other are connected at their ends so that the current flows in opposite directions, and a first gap and a second gap between the pair of first linear portions are formed. The sensor unit is characterized in that it comprises a second current-carrying portion arranged so that second gaps between the pair of second linear portions face each other, and a connecting portion that connects the first current-carrying portion and the second current-carrying portion in a unicursal shape so that when the current flows through the first current-carrying portion and the second current-carrying portion, the magnetic flux caused by the current passes from one of the first gap and the second gap to the other, and the sensor unit comprises a Hall element that is arranged between the first gap and the second gap and detects the current via the magnetic flux. [Effects of the Invention]

[0007] The current sensor described above can effectively detect low currents. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a perspective view showing a current sensor according to a first embodiment. [Figure 2] 2A to 2C are three-view diagrams illustrating the current sensor shown in FIG. 1. [Figure 3] 1 is a schematic diagram showing magnetic fluxes generated around a pair of first linear portions and a pair of second linear portions when current flows through a first current-carrying portion and a second current-carrying portion in a bus bar. FIG. [Figure 4] 10 is a schematic diagram showing magnetic fluxes generated around a connecting portion, a first terminal portion, and a second terminal portion when current flows through a first current-carrying portion and a second current-carrying portion in a bus bar. FIG. [Figure 5]FIG. 10 is a schematic diagram showing magnetic flux generated when current flows through a first current-carrying portion and a second current-carrying portion in a busbar, the magnetic flux generated around the first horizontal bar portion of the first current-carrying portion and the second horizontal bar portion of the second current-carrying portion. [Figure 6] FIG. 6 is a perspective view showing a current sensor of a first comparative example for comparison with the current sensor shown in FIGS. 1 to 5. [Figure 7] FIG. 6 is a perspective view showing a current sensor of a second comparative example for comparison with the current sensor shown in FIGS. 1 to 5. [Figure 8] 6 is a graph showing that in the current sensor shown in FIGS. 1 to 5, the magnetic flux at the position where the Hall element is arranged becomes a constructive magnetic flux compared to the conventional current sensor. [Figure 9] FIG. 10 is a perspective view showing a current sensor according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the current sensor will be described below. First, a first embodiment will be described.

[0010] FIG. 1 is a perspective view showing a current sensor according to a first embodiment, and FIG. 2 is a three-view diagram showing the current sensor shown in FIG.

[0011] The current sensor 1 of this embodiment detects the current I of the object to be measured using a Hall element 121, and is equipped with a bus bar 11 formed of a conductive metal through which the current I of the object to be measured flows, and a sensor unit 12 that detects the current I flowing through the bus bar 11.

[0012] The busbar 11 is a member formed by bending a conductive metal strip cut into a curved shape, and includes a first current-carrying portion 111, a second current-carrying portion 112, a connecting portion 113, a first terminal portion 114, and a second terminal portion 115.

[0013] The first current-carrying portion 111 is a portion in which a pair of first linear portions 111a arranged along each other are connected at their ends so that current I flows in opposite directions. Specifically, the first current-carrying portion 111 has a first horizontal bar portion 111b that connects one ends of the pair of first linear portions 111a and forms a horizontal bar of a U-shape with the pair of first linear portions 111a as two arm portions.

[0014] Similar to the first current-carrying portion 111, the second current-carrying portion 112 is a portion in which a pair of second linear portions 112a arranged along each other are connected at their ends so that current I flows in opposite directions. Specifically, the second current-carrying portion 112 has a second horizontal bar portion 112b that connects one ends of the pair of second linear portions 112a and forms a horizontal bar of a U-shape with the pair of second linear portions 112a as two arm portions. The second current-carrying portion 112 is disposed such that the first gap 111c between the pair of first linear portions 111a and the second gap 112c between the pair of second linear portions 112a in the first current-carrying portion 111 face each other. In this arrangement, the second horizontal bar portion 112b of the second current-carrying portion 112 extends along the first horizontal bar portion 111b of the first current-carrying portion 111.

[0015] The connecting portion 113 is a portion that connects the first current-carrying portion 111 and the second current-carrying portion 112 in a unicursal shape. Here, the pair of first linear portions 111a in the first current-carrying portion 111 and the pair of second linear portions 112a in the second current-carrying portion 112 are located at the vertices of a rectangle in plan view when viewed from a plane perpendicular to the linear portions. The connecting portion 113 is a portion that extends along a diagonal line of the rectangle so as to connect an end of the first linear portion 111a and an end of the second linear portion 112a that correspond to the vertices of the diagonal line.

[0016] The first terminal portion 114 is a portion that extends along the connecting portion 113 from the end of the first linear portion 111a on the non-connected side, which is different from the connected side by the connecting portion 113, of the pair of first linear portions 111a, and the extended end becomes an electrical connection terminal 114a.

[0017] The second terminal portion 115 is a portion that extends from the end of the second linear portion 112a on the non-connected side, which is different from the connected side by the connecting portion 113, along the connecting portion 113, and the extending end becomes an electrical connection terminal 115a.

[0018] Here, in busbar 11, due to the connection of connecting portion 113 in a unicursal shape, when current I flows, magnetic flux is generated due to the current I as follows.

[0019] Fig. 3 is a schematic diagram showing magnetic flux generated around a pair of first linear portions and a pair of second linear portions when current flows through the first and second current-carrying portions of the busbar. Fig. 4 is a schematic diagram showing magnetic flux generated around a connecting portion, a first terminal portion, and a second terminal portion when current flows through the first and second current-carrying portions of the busbar. Fig. 5 is a schematic diagram showing magnetic flux generated around a first horizontal portion of the first current-carrying portion and a second horizontal portion of the second current-carrying portion when current flows through the first and second current-carrying portions of the busbar. In Figs. 3 and 4, the magnetic flux at each portion is shown in a cross section perpendicular to the first linear portion 111a and the second linear portion 112a, and in Fig. 5, the magnetic flux is shown in a cross section perpendicular to the first horizontal portion 111b and the second horizontal portion 112b.

[0020] First, as shown in FIG. 3, the current I flows in opposite directions in the pair of first linear portions 111a, so the magnetic flux φ11 reinforces each other in the first gap 111c. Similarly, the current I flows in opposite directions in the pair of second linear portions 112a, so the magnetic flux φ11 reinforces each other in the second gap 112c. Then, the magnetic flux φ11 flows in the same direction in the first gap 111c and the second gap 112c, so the reinforced magnetic flux φ12 passes from one of the first gap 111c and the second gap 112c to the other, as described above. In the example of FIG. 3, the current I flows from the first terminal portion 114 to the second terminal portion 115 in the busbar 1, so the reinforced magnetic flux φ12 passes from the second gap 112c to the first gap 111c.

[0021] 4, when a current I flows through the busbar 1, the magnetic flux φ11 reinforces each other between the connecting portion 113 and the first terminal portion 114 and between the connecting portion 113 and the second terminal portion 115. On the other hand, the magnetic flux φ13 between the connecting portion 113 and the first terminal portion 114 and the magnetic flux φ14 between the connecting portion 113 and the second terminal portion 115 are opposite in direction and cancel each other out. This cancellation reduces the influence of the magnetic fluxes φ13 and φ14 on the magnetic flux φ12 passing from the second gap 112c to the first gap 111c.

[0022] 5, when a current I flows through the busbar 1, the current I flows in the first horizontal bar portion 111b and the second horizontal bar portion 112b in the same direction. As a result, magnetic fluxes φ11 are generated between the first horizontal bar portion 111b and the second horizontal bar portion 112b in opposite directions, and cancel each other out. This cancellation reduces the influence of the magnetic flux φ11 on the magnetic flux φ12 passing from the second gap 112c to the first gap 111c.

[0023] In this embodiment, the sensor unit 12 detects the current I flowing through the bus bar 1 via the magnetic flux φ12 passing from the second gap 112c to the first gap 111c. The sensor unit 12 includes a Hall element 121 and a sensor substrate 122. The Hall element 121 is a rectangular flat-plate element that detects the current I flowing through the bus bar 1 via the magnetic flux φ12, and is disposed between the first gap 111c and the second gap 112c so that the magnetic flux φ12 passes through. The sensor substrate 122 is a rectangular flat-plate circuit board on which the Hall element 121 is mounted and on which a circuit for amplifying the detection result of the Hall element 121 is formed.

[0024] Fig. 6 is a perspective view showing a current sensor of a first comparative example for comparison with the current sensors shown in Figs. 1 to 5. Fig. 7 is a perspective view showing a current sensor of a second comparative example for comparison with the current sensors shown in Figs. 1 to 5. In Figs. 6 and 7, components equivalent to those in the perspective view of Fig. 1 are assigned the same reference numerals as in Fig. 1, and redundant explanations of these equivalent components will be omitted below.

[0025] 6 includes a bus bar 51 in the form of a straight strip plate, and a sensor unit 12 having a Hall element 121 equivalent to that of the above-described embodiment. The sensor unit 12 is disposed so as to overlap with the longitudinal center of the bus bar 51. When a current I5 flows through the bus bar 51, the Hall element 121 detects the current I5 via a magnetic flux φ51 generated around the bus bar 51.

[0026] The current sensor 6 of the second comparative example shown in FIG. 7 includes a sensor unit 12 having a linear strip-shaped bus bar 61 and a Hall element 121, as well as a C-shaped core 63 that converges magnetic flux φ61 to enhance the detection effect of the Hall element 121. The C-shaped core 63 is made of a material with high magnetic permeability, such as ferrite, and is formed into a C-shaped cross section. When a current I6 flows through the bus bar 61, the magnetic flux φ61 generated around the bus bar 61 passes through the bus bar 61 and converges in the gap. The sensor unit 12 is positioned so that the Hall element 121 can efficiently detect the current I6 via the magnetic flux φ61 converged in the gap.

[0027] In the current sensor 5 of the first comparative example shown in FIG. 6, the magnetic flux φ51 generated around the bus bar 51 is small, and when the target current I5 is low, the generated magnetic flux φ51 may fall below the lower detection limit of the Hall element 121, making detection difficult. In the current sensor 6 of the second comparative example shown in FIG. 7, the current I6 is detected via the magnetic flux φ61 converged by the C-shaped core 63, so the difficulty of detecting low currents is reduced compared to the current sensor 5 of the first comparative example. On the other hand, the C-shaped core 63 tends to be expensive due to the large number of steps required for manufacturing.

[0028] In contrast to these comparative examples, the current sensor 1 of the first embodiment shown in FIGS. 1 to 5 can achieve the following effects. That is, according to the current sensor 1 of the present embodiment, when a current I to be measured flows through the busbar 11, a mutually strengthening magnetic flux φ12 is generated in the first gap 111c between the pair of first linear portions 111a through which the current I flows in opposite directions in the first current-carrying portion 111. A similar mutually strengthening magnetic flux φ12 is also generated in the second gap 112c between the pair of second linear portions 112a in the second current-carrying portion 112. Then, due to the uniaxial connection by the connecting portion 113, this mutually strengthening magnetic flux φ12 passes from one of the first gap 111c and the second gap 112c to the other.

[0029] FIG. 8 is a graph showing that the magnetic flux at the position where the Hall element is arranged in the current sensor shown in FIGS. 1 to 5 becomes a constructive magnetic flux compared to the conventional current sensor.

[0030] Graph G1 in Fig. 8 shows the magnetic flux density [mT] at the sensor position when the current sensor 5 of the first comparative example shown in Fig. 6 is a conventional type and the distance between the busbars 11, 51 and the Hall element 121 is the same. These magnetic flux densities are the magnetic flux densities when a current of 100 [A] flows through the busbars 11, 51. According to graph G1, the magnetic flux density at the sensor position in the conventional type (first comparative example) current sensor 5 is 3.85 [mT], whereas in the current sensor 1 of this embodiment, the magnetic flux density is increased to 7.98 [mT].

[0031] According to the current sensor 1 of the first embodiment described above, the Hall element 121 in the sensor unit 12 is disposed in the pass band of the magnetic flux φ12, that is, between the first gap 111c and the second gap 112c, so as to detect the current I via the strengthened magnetic flux φ12. Therefore, according to the current sensor 1 of this embodiment, even if the current I to be measured is low, this low current can be effectively detected by passing through the strengthened magnetic flux φ12.

[0032] In this embodiment, the shape of the busbar 11 that produces the effect of strengthening the magnetic flux φ12 is formed by a method of cutting and bending a curved conductive metal strip from a metal plate. These methods are less expensive than the formation of the C-shaped core 63 in the current sensor 6 of the second comparative example. Thus, the current sensor 1 of this embodiment can effectively detect low currents at a relatively low cost.

[0033] In this embodiment, the pair of first linear portions 111a and the pair of second linear portions 112a are located at the vertices of a rectangle in a plan view perpendicular to the linear portions. The connecting portion 113 extends along the diagonal line to connect the end of the first linear portion 111a and the end of the second linear portion 112a, which correspond to the vertices of the diagonal line. The busbar 1 includes a first terminal portion 114 and a second terminal portion 115 extending along the connecting portion 113. With this configuration, when a current I flows through the busbar 1, a magnetic flux φ13 generated in the gap between the connecting portion 113 and the first terminal portion 114 and a magnetic flux φ14 generated in the gap between the connecting portion 113 and the second terminal portion 115 are directed in opposite directions and cancel each other out. This cancellation reduces the effect of the magnetic fluxes φ13 and φ14 generated in the gap on the magnetic flux φ12 used for current detection by the Hall element 121. As a result, the current I can be detected via the more stable magnetic flux φ12.

[0034] In this embodiment, the first current-carrying portion 111 is formed so that a pair of the first linear portion 111a and the first horizontal portion 111b form a U-shape. Similarly, the second current-carrying portion 112 is formed so that a pair of the second linear portion 112a and the second horizontal portion 112b form a U-shape. The second horizontal portion 112b and the first horizontal portion 111b extend along each other. With this configuration, when a current flows through the busbar 1, the magnetic fluxes φ11 generated around the first horizontal portion 111b and the second horizontal portion 112b are oriented in opposite directions and cancel each other out. This cancellation reduces the effect of the magnetic flux φ11 generated around each horizontal portion on the magnetic flux φ12 used for current detection by the Hall element 121. As a result, the current I can be detected via a more stable magnetic flux φ12.

[0035] This concludes the description of the first embodiment, and next, the second embodiment will be described.

[0036] Fig. 9 is a perspective view showing a current sensor according to a second embodiment. In Fig. 9, components equivalent to those shown in Fig. 1 are denoted by the same reference numerals as in Fig. 1 only if they are necessary for explanation, and redundant explanations of these equivalent components will be omitted below.

[0037] The current sensor 2 of this embodiment is obtained by adding an external magnetic shield 21 to the configuration of the first embodiment shown in Fig. 1. The external magnetic shield 21 is formed to define an accommodating space 211 that accommodates the first current-carrying portion 111 and the second current-carrying portion 112 of the bus bar 11 together with the Hall element 121 disposed therebetween, and is a portion that shields the accommodating space 211 from external magnetism. Note that Fig. 9 does not illustrate the sensor substrate 122 of the sensor unit 12 shown in Fig. 1. The external magnetic shield 21 is made of a soft magnetic material, particularly permalloy, which is a nickel-iron alloy containing 35 to 80% nickel (Ni), and is formed in a cylindrical shape with the accommodating space 211 on the inside.

[0038] The current sensor 2 of the second embodiment described above can effectively detect low currents as the current I to be measured, just like the first embodiment described above, and it goes without saying that such detection can be performed relatively inexpensively.

[0039] In addition, in this embodiment, an external magnetic shield 21 is provided that houses the first current-carrying portion 111 and the second current-carrying portion 112 in the housing space 211 to block them from external magnetism. With this configuration, external magnetic noise is blocked, so that the current I (low current) can be detected more effectively.

[0040] Furthermore, in this embodiment, the external magnetic shield 21 is a part formed in a tubular shape, specifically a cylindrical shape, with the inside of the accommodating space 211. With this configuration, the external magnetic shield 21 can be formed less expensively than, for example, a C-shaped shield, etc., and therefore the manufacturing cost can be reduced.

[0041] The first and second embodiments described above are merely representative examples of current sensors, and the current sensor is not limited to these and can be implemented in various modified forms.

[0042] For example, in the above-described first and second embodiments, as an example of a current sensor, the current sensors 1 and 2 are exemplified, without specifying a specific fixing method, in which the sensor unit 12 is fixed with the Hall element 121 positioned relative to the bus bar 11. However, the method for fixing the sensor unit in the current sensor is not limited to a specific method, and any fixing method can be adopted.

[0043] In the first and second embodiments described above, current sensors 1 and 2 are illustrated as examples of current sensors, in which a pair of first linear portions 111a and a pair of second linear portions 112a are located at the vertices of a rectangle in a plan view, and a connecting portion 113 extends along the diagonal of the rectangle. Furthermore, the busbar 1 of these current sensors 1 and 2 includes a first terminal portion 114 and a second terminal portion 115 extending along the connecting portion 113. However, the current sensor is not limited to this, and the relative positional relationship between the first linear portion and the second linear portion and the connecting form by the connecting portion are not limited to specific forms. Furthermore, the busbar does not necessarily have to include a first terminal portion and a second terminal portion along the connecting portion, and the specific terminal form is not limited to these forms. However, as described above, according to the above-described form, the influence of the magnetic fluxes φ13 and φ14 generated between the connecting portion 113, the first terminal portion 114, and the second terminal portion 115 is suppressed, and the current I can be detected via a more stable magnetic flux φ12.

[0044] In the first and second embodiments described above, the current sensors 1 and 2 are illustrated as examples of current sensors in which the first current-carrying portion 111 and the second current-carrying portion 112 form a U-shape and the second horizontal bar portion 112b and the first horizontal bar portion 111b extend parallel to each other. However, current sensors are not limited to this. The specific shapes of the first current-carrying portion and the second current-carrying portion may be shapes other than U-shapes as long as they include a pair of first linear portions and a pair of second linear portions arranged parallel to each other. Even when forming a U-shape, the relative positions of the second horizontal bar portion and the first horizontal bar portion may be such that they do not extend parallel to each other but extend in separate directions. However, as described above, by arranging the second horizontal bar portion 112b and the first horizontal bar portion 111b, each of which forms a part of a U-shape, parallel to each other, the influence of the magnetic flux φ11 generated around each horizontal bar portion is suppressed, and the current I can be detected via a more stable magnetic flux φ12.

[0045] In the second embodiment described above, the current sensor 2 is illustrated as an example of a current sensor, including a cylindrical external magnetic shield 21. However, the current sensor is not limited to this, and may be one that does not include an external magnetic shield, as illustrated in the first embodiment. Even if an external magnetic shield is included, the shape of the shield is not limited to a cylindrical shape, and any specific shape is acceptable as long as it is formed to define an accommodation space that accommodates the first current-carrying portion and the second current-carrying portion together with the Hall element. However, as described above, providing the external magnetic shield 21 blocks external magnetic noise, thereby enabling more effective detection of the current I. Furthermore, as described above, manufacturing costs can be reduced by forming the external magnetic shield 21 in a cylindrical shape or a cylindrical shape other than a cylindrical shape. [Explanation of symbols]

[0046] 1,5,2 Current Sensor 11,51,61 Busbar 12 Sensor section 21 External magnetic shield 63 C-shaped core 111 1st energized part 111a 1st linear part 111b First horizontal bar 111c 1st gap 112 2nd energized part 112a Second linear part 112b Second horizontal bar 112c 2nd gap 113 Connecting part 114 1st terminal part 114a, 115a connection terminal 115 2nd terminal part 121 Hall element 122 Sensor board 211 Containment Space G1 graph I,I5,I6 current φ11,φ12,φ13,φ14,φ51,φ61 Magnetic flux

Claims

1. a bus bar formed of a conductive metal and through which a current to be measured flows; a sensor unit that detects the current flowing through the bus bar, The bus bar is a first current-carrying portion in which a pair of first linear portions arranged along each other are connected at their ends so that the current flows in opposite directions; a second current-carrying portion in which a pair of second linear portions arranged along each other are connected at their ends so that the current flows in opposite directions, and a first gap between the pair of first linear portions and a second gap between the pair of second linear portions are arranged to face each other; a connecting portion that connects the first current-carrying portion and the second current-carrying portion in a unicursal shape such that, when the current flows through the first current-carrying portion and the second current-carrying portion, a magnetic flux caused by the current passes from one of the first gap and the second gap to the other; Equipped with The sensor unit a Hall element disposed between the first gap and the second gap and configured to detect the current via the magnetic flux; A current sensor comprising:

2. the pair of first linear portions and the pair of second linear portions are located at vertices of a quadrangle in a plan view when a plane perpendicular to each linear portion is seen, the connecting portion is a portion extending along one diagonal line of the quadrangle so as to connect an end of a first linear portion and an end of a second linear portion corresponding to a vertex of the diagonal line, The bus bar is a first terminal portion extending from an end of the first linear portion of the pair of first linear portions on a non-connected side different from a side connected by the connecting portion along the connecting portion, the extending end serving as an electrical connection terminal; a second terminal portion extending from an end of the second linear portion of the pair of second linear portions on a non-connected side different from a side connected by the connecting portion along the connecting portion, the extending end serving as an electrical connection terminal; 2. The current sensor of claim 1, further comprising:

3. the first current-carrying portion has a first horizontal bar portion that connects one end of the pair of first linear portions to each other, forming a horizontal bar of a U-shape with the pair of first linear portions as two arm portions, The current sensor described in claim 1, characterized in that the second current-carrying portion has a second horizontal bar portion that connects one end of the pair of second linear portions to form a U-shaped horizontal bar with the pair of second linear portions as two arm portions, and the second horizontal bar portion is arranged so as to extend along the first horizontal bar portion.

4. 2. The current sensor according to claim 1, further comprising an external magnetic shield formed to define an accommodating space that accommodates the first and second current-carrying portions together with the Hall element disposed therebetween, and that insulates the accommodating space from external magnetic fields.

5. 5. The current sensor according to claim 4, wherein the external magnetic shield is a cylindrical part having the accommodation space on the inside.

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