JP6516058B1 - Current sensor and method of manufacturing bus bar used therefor - Google Patents

Abstract

An object of the present invention is to reduce a measurement error caused by a temperature difference of a bus bar in a current sensor capable of measuring a large current by dividing a current to be measured flowing through the bus bar. A current sensor according to the present invention includes a bus bar 10 through which a current to be measured I flows, and a magnetic sensor disposed in an area A. The bus bar 10 has a detection wiring portion 11 through which a part of the measurement target current I flows, and branch wiring portions 12A and 12B through which the remaining part of the measurement target current I flows. The detection wiring portion 11 has a longer current path than the branch wiring portions 12A and 12B, and the detection wiring portion 11 and the branch wiring portions 12A and 12B have the same cross-sectional shape perpendicular to the current direction. According to the present invention, it is possible to reduce the measurement error due to the temperature difference of the bus bars because the difference in heat generation amount due to the difference in the length of the current path is offset by the difference in heat capacity. [Selected figure] Figure 3

Description

  The present invention relates to a current sensor and a method of manufacturing a bus bar used therefor, and more particularly to a current sensor suitable for measuring a large current and a method of manufacturing a bus bar used therein.

  The current sensor is generally of a type in which a magnetic sensor detects a magnetic field generated by the current to be measured. For example, Patent Document 1 discloses a current sensor of a type in which a bus bar through which a current to be measured flows is branched into two and a magnetic sensor generates a magnetic field generated by a current flowing through one of the branch bars.

  In the current sensor described in Patent Document 1, since the bus bar is branched into two and the magnetic sensor is allocated to one of the branch bars, even if the current to be measured flowing through the bus bar is a large current, it flows to the branch bar Since the amount of current can be reduced, it is suitable for measuring a large current.

JP 2002-257866 A

  In the current sensor described in Patent Document 1, since the lengths of the two branched bars are the same, the current density per unit cross sectional area is the same, and accordingly, the calorific value per unit cross sectional area is also the same. is there. However, the two branch bars have different heat capacities because the cross-sectional areas themselves are different from each other. For this reason, a temperature difference actually occurs in the two branch bars, which causes a difference in the electrical resistivity, so that the diversion ratio of the current to be measured changes. As a result, there is a problem that an error occurs in the measured value of the current to be measured.

  Therefore, an object of the present invention is to reduce a measurement error caused by a temperature difference between bus bars in a current sensor that can measure a large current by dividing a current to be measured flowing through the bus bars. Another object of the present invention is to provide a method of manufacturing a bus bar used for such a current sensor.

  The current sensor according to the present invention includes a bus bar through which the current to be measured flows and a magnetic sensor detecting a magnetic field generated from the bus bar, and the bus bar has a detection wiring portion through which a part of the current to be measured flows and the rest of the current to be measured The magnetic sensor detects a magnetic field generated by a part of the current to be measured flowing through the detection wiring portion, and the detection wiring portion has a longer current path than the branch wiring portion, The detection wiring portion and the branch wiring portion are characterized in that the shapes of cross sections perpendicular to the current direction are equal to each other.

  According to the present invention, since the current path of the detection wiring portion is longer than the branch wiring portion, it is possible to further reduce the amount of current flowing in the detection wiring portion. This makes it possible to measure a large current. In addition, since the cross-sectional shapes of the detection wiring portion and the branch wiring portion are equal to each other, the difference in the amount of heat generation due to the difference in the length of the current path is offset by the difference in heat capacity. This makes it possible to reduce the measurement error caused by the temperature difference between the bus bars.

  In the present invention, the bus bar may have a plurality of branch wiring portions. According to this, since the amount of current flowing in the detection wiring portion is further reduced, it is possible to measure a larger current.

  In the present invention, the bus bar further includes an input wiring portion connected to one end of the detection wiring portion and one end of the branch wiring portion, and an output wiring portion connected to the other end of the detection wiring portion and the other end of the branch wiring portion. The portion including the detection wiring portion, the branch wiring portion, the input wiring portion, and the output wiring portion may be formed of a metal plate having a constant thickness. According to this, it is possible to easily manufacture the bus bar by punching a metal plate having a constant thickness.

  A method of manufacturing a bus bar according to the present invention is a method of manufacturing a bus bar used for a current sensor, wherein a metal plate having a constant thickness is prepared, and a metal plate is punched to form an input wiring portion and an output wiring portion. One end connected to the input wiring portion and the other end connected to the output wiring portion, and the branch wiring portion one end connected to the input wiring portion and the other end connected to the output wiring portion And the width of the detection wiring portion is equal to the width of the branch wiring portion.

  According to the present invention, by forming a bus bar having a detection wiring portion and a branch wiring portion having a constant processing width by punching a metal plate having a constant thickness, the detection wiring portion and the branch wiring are formed. The machining accuracy of the parts completely matches. For this reason, it becomes possible to reduce the measurement error resulting from the difference in processing accuracy.

  As described above, according to the present invention, it is possible to reduce the measurement error caused by the temperature difference of the bus bar in the current sensor that enables the measurement of a large current by dividing the current to be measured flowing through the bus bar. . Further, according to the present invention, it is possible to provide a method of manufacturing a bus bar used for such a current sensor.

FIG. 1 is a schematic perspective view showing the appearance of a current sensor according to a preferred embodiment of the present invention. FIG. 2 is a schematic perspective view showing a state in which the upper lid of the case 20 is removed in the current sensor according to the preferred embodiment of the present invention. FIG. 3 is a plan view for explaining the shape of bus bar 10. FIG. 4 is a plan view for explaining the shape of the bus bar 10A according to the modification. FIG. 5 is a schematic view for explaining the direction of the magnetic flux applied to the region A. As shown in FIG. FIG. 6 is a schematic view showing an example in which the magnetic sensor 40 having the magnetic core 41 is disposed in the area A. As shown in FIG.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic perspective view showing the appearance of a current sensor according to a preferred embodiment of the present invention.

  As shown in FIG. 1, the current sensor according to the present embodiment includes a bus bar 10 through which a current to be measured I flows, and a case 20 attached to the bus bar 10. The bus bar 10 is a metal plate made of a good conductor such as copper (Cu), and the thickness in the y direction is constant. Although not particularly limited, the current sensor according to the present embodiment uses two bus bars 10 in an overlapping manner on the assumption that the measurement target current I is a large current. The two bus bars 10 are fixed in the input wiring portion 13 and the output wiring portion 14 via the connection plate 18. For this reason, the two bus bars 10 are not in contact with each other, thereby preventing the occurrence of a measurement error caused by the contact resistance. Screw holes 19 are provided in the input wiring portion 13, the output wiring portion 14 and the connection plate 18, and the screw holes 19 are used to fix the device to be measured.

  A magnetic sensor is housed inside the case 20. FIG. 2 is a schematic perspective view showing a state in which the upper lid of the case 20 is removed. As shown in FIG. 2, the circuit board 30 and the magnetic sensor 40 mounted on the circuit board 30 are accommodated in the case 20. Case 20 may itself be a magnetic core. The type of the magnetic sensor 40 is not particularly limited, but a flux gate sensor, an MI (magnetic impedance) sensor, a Hall sensor, an AMR sensor, a GMR sensor, a TMR sensor, or the like can be used. The terminal electrodes E1 to E4 shown in FIG. 1 are derived from the circuit board 30, and are connected to predetermined elements according to the type of the magnetic sensor 40 to be used. For example, if the magnetic sensor 40 is a flux gate sensor, the terminal electrodes E1 and E2 are connected to one end and the other end of the detection coil, and the terminal electrodes E3 and E4 are connected to one end and the other end of the compensation coil.

  FIG. 3 is a plan view for explaining the shape of bus bar 10.

As shown in FIG. 3, the bus bar 10 has a detection wiring portion 11 and branch wiring portions 12A and 12B connected between the input wiring portion 13 and the output wiring portion 14. The detection wiring portion 11 and the branch wiring portions 12A and 12B are connected in parallel, and therefore, when the measurement target current I flows from the input wiring portion 13 to the output wiring portion 14, the current which is a part of the measurement target current I Id flows to the detection wiring portion 11, and currents Ib _A and Ib _B , which are the remaining portions of the measurement target current I, flow to the branch wiring portions 12A and 12B, respectively. Therefore, I = Id + Ib _A + Ib _B.

Detecting the wiring portion 11 includes first and second portions ₁₁ extending in the z direction 1, and 11 _2, and a third portion 11 ₃ which extends in the x-direction, current Id, the first portion 11 _1, it flows in the order of the third portion 11 ₃ and the second portion 11 _2. Therefore, the direction of current Id flowing in the first portion 11 _1, the direction of the current Id flowing through the _secondary second portion 11 is opposite to each other. The magnetic sensor 40 is disposed in the first portion 11 ₁ and the second portion 11 ₂ sandwiched by area A of the detection wire 11.

  On the other hand, the two branch wiring portions 12A and 12B both extend in the x direction, and connect the input wiring portion 13 and the output wiring portion 14 with the shortest distance. Therefore, as a length of the current path, the detection wiring portion 11 is longer than the branch wiring portions 12A and 12B. Thereby, the current Id flowing through the detection wiring portion 11 is further reduced. The two branch wiring portions 12A and 12B are provided in parallel in this embodiment in order to further reduce the current Id flowing through the detection wiring portion 11 by lowering the resistance value of the branch wiring portions 12A and 12B. The number of branch wiring portions is not limited to two, and three branch wiring portions 12A to 12C may be provided in parallel as in the bus bar 10A according to the modification shown in FIG.

As shown in FIG. 5 which is a schematic view, when the magnetic sensor 40 is disposed in the area A, the magnetic flux in the same direction is applied to the area A by the current Id flowing through the detection wiring portion 11. In the example shown in FIG. 5, clock by a first portion 11 counterclockwise magnetic flux φ1 is generated by a current Id flowing in _the current flowing through the ₂ second portion 11 of the detection wires 11 Id of the detection wire 11 Since the surrounding magnetic flux φ2 is generated, the directions of the magnetic flux applied to the region A are all in the y direction. Therefore, if the magnetic sensor 40 is disposed in the region A and the magnetic sensor 40 detects the strength of the magnetic field in the y direction, it is possible to detect the amount of the current Id flowing through the detection wiring portion 11. Then, since the current Id flowing through the detection wiring portion 11 and the division ratio of the currents Ib _A and Ib _B flowing through the branch wiring portions 12A and 12B are known, the measurement target current I is calculated based on the detected value of the current Id. It is possible to

  As shown in FIG. 6, the magnetic sensor 40 may have a magnetic core 41. In the example shown in FIG. 6, using the annular magnetic core 41 opened in the z direction, the detection wiring portion 11, the saturable magnetic material M and the detection coil C wound around the area are surrounded by the magnetic core 41. Is placed. That is, when the case 20 itself shown in FIGS. 1 and 2 is the magnetic core 41, such a configuration can be obtained. If such a magnetic core 41 is used, the disturbance magnetic field bypasses the magnetic core 41, so that the influence of the disturbance magnetic field can be reduced.

In the present embodiment, the thickness of the bus bar 10 in the y direction is constant, and the conductor width of the detection wiring portion 11 and the branch wiring portions 12A and 12B, that is, the width perpendicular to the current direction is also constant. Specifically, 1 first and second portions ₁₁ constituting the detection wires 11, 11 the width of ₂ in the x direction, the third portion 11 ₃ of the z width in a direction constituting the detection wire 11, the branch The widths of the wiring portions 12A and 12B in the z direction coincide with each other. This means that the cross-sectional shapes of the detection wiring portion 11 and the branch wiring portions 12A and 12B perpendicular to the current direction are equal to each other.

Therefore, assuming that the length of each of the branch wiring sections 12A and 12B is 2L and the length of the detection wiring section 11 is kL, the ratio of the resistance values of the detection wiring section 11, the branch wiring section 12A and the branch wiring section 12B is , K: 2: 2: Therefore, the ratio of the current Id flowing through the detection wiring portion 11, the current Ib _A flowing through the branch wiring portion 12A, and the current Ib _A flowing through the branch wiring portion 12A is 2: k: k. Since the detection wiring portion 11 and the branch wiring portions 12A and 12B have the same cross-sectional area, the ratio of the heat generation amount in the detection wiring portion 11, the branch wiring portion 12A and the branch wiring portion 12B is also 2: k : K.

  Here, the detection wiring portion 11 has a length k / 2 times that of the branch wiring portions 12A and 12B, and the detection wiring portion 11 and the branch wiring portions 12A and 12B have the same cross-sectional area. Since it has, the ratio of the heat capacity of the volume of the detection wiring part 11, the branch wiring part 12A, and the branch wiring part 12B, ie, heat capacity, becomes k: 2: 2. This means that the branch wiring portions 12A and 12B release heat k / 2 times faster than the detection wiring portion 11. That is, since the branch wiring portions 12A and 12B each emit heat k / 2 times faster than the detection wiring portion 11 instead of generating heat by k / 2 times, the detection wiring portion 11 and the branch wiring portion 12A , 12B hardly cause temperature difference. As a result, since the change in resistance value due to the temperature difference can be suppressed, the current I to be measured can be shunted as designed, and the measurement error due to the temperature difference is reduced.

  The bus bar 10 prepares a metal plate having a constant thickness made of copper (Cu) or the like, and performs punching processing on this metal plate, whereby the detection wiring portion 11, the branch wiring portions 12A and 12B, and the input wiring portion The bus bar 10 composed of 13 and the output wiring portion 14 can be manufactured in one step. In punching processing on a metal plate, if the thickness and the processing width of the metal plate differ depending on the plane position, the punching conditions differ depending on the plane position, and it is difficult to process the shape as designed. On the other hand, in the bus bar 10 of the present embodiment, the thickness of the metal plate to be used is constant, and the processing widths of the detection wiring portion 11 and the branch wiring portions 12A and 12B are constant. It becomes possible to secure. As a result, it is possible to reduce the measurement error caused by the variation in machining accuracy.

  Further, when changing the diversion ratio, the number of branch wiring portions having the same conductor width may be changed. Even when the number of branch wiring parts is changed, if the conductor widths of the detection wiring part and the branch wiring part are made to be the same, the difference in heat generation amount is offset by the difference in heat capacity. Measurement error can be reduced.

  Further, in the present embodiment, by overlapping and using the two bus bars 10, the current density flowing through the bus bars 10 is suppressed to half. The same current density can also be obtained by using a bus bar having a double thickness, but in this case, since the thickness of the metal plate to be used is increased, the processing accuracy at the time of punching is reduced. In contrast to this, when the two bus bars 10 are stacked and used, the thickness of the metal plate is halved, so that it is possible to improve the processing accuracy at the time of punching processing. And since the thickness of a metal plate is thin, the measurement error resulting from the skin effect at the time of a high frequency current flowing is also suppressed.

  Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. It is needless to say that they are included in the scope.

10, 10A bus bar 11 detection wiring portion 11 ₁ first portion 11 ₂ second portion 11 ₃ third portion 12A to 12C branch wiring portion 13 input wiring portion 14 output wiring portion 18 connection plate 19 screw hole 20 case 30 circuit Substrate 40 Magnetic sensor 41 Magnetic core A region C Detection coil E1 to E4 Terminal electrode I Current to be measured M Saturable magnetic material φ1, φ2 Magnetic flux

Claims (3)

Bus bars through which the current to be measured flows,
And a magnetic sensor for detecting a magnetic field generated from the bus bar,
The bus bar includes a detection wiring portion in which a part of the current to be measured flows, and a plurality of branch wiring portions in which the remaining portion of the current to be measured flows.
The magnetic sensor detects a magnetic field generated by the part of the current to be measured flowing through the detection wiring portion,
The detection wiring portion has a longer current path than the plurality of branch wiring portions.
The current sensor, wherein the detection wiring portion and the plurality of branch wiring portions have the same cross-sectional shape perpendicular to the current direction. The bus bar, the detection wire portion and an input wiring portion having one end and connected to one end of said plurality of branch wiring portion, the detection wire portion the other end and an output connected to the other end of said plurality of branch wiring section A portion further comprising a wiring portion, and the portion including the detection wiring portion, the plurality of branch wiring portions, the input wiring portion, and the output wiring portion is made of a metal plate having a constant thickness. The current sensor according to 1 . A method of manufacturing a bus bar used for a current sensor, wherein a metal plate having a constant thickness is prepared, and the metal plate is punched to form an input wiring portion, an output wiring portion, and one end of the input wiring portion. are connected, and the detection wiring portion to which the other end is connected to the output interconnection, one end of which is connected to the input wiring section both, a plurality of branch wiring portion to which the other end is connected to the output interconnection none And manufacturing the bus bar having the same width of the detection wiring portion and the widths of the plurality of branch wiring portions.

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