Current sensor

Abstract

A current sensor (10) according to the present invention, which is provided with a bus bar effective for low cost and weight reduction, is provided with: a bus bar (1) through which a current to be measured flows; and a magnetic detection unit (2) that is disposed so as to face the bus bar (1) and senses a magnetic field generated in the bus bar (1), the bus bar (1) comprising a laminated material in which a first metal-based material (3) and a second metal-based material (4), which are dissimilar metal-based materials, are laminated, the first metal-based material (3) having a higher density than the second metal-based material (4) and a lower electrical resistivity than the second metal-based material (4), and the second metal-based material (4) having a higher electrical resistivity than the first metal-based material (3). The magnetic detection unit (2) is disposed so as to face a surface (3S) of the bus bar (1) formed by the first metal material (3).

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 bus bar and measures the current value of the measured current based on the detected magnetic field. Background Art

[0002] In recent years, in order to control and monitor various devices, current sensors are used in various devices to measure the measured current flowing through the various devices. As such a current sensor, a current sensor using a magnetoelectric conversion element is known, and the magnetoelectric conversion element senses a magnetic field generated due to the measured current flowing through a bus bar that is a current path. In addition, corresponding to the increase in electric vehicles, hybrid vehicles, etc. that use a motor as a power source, requirements for the current sensor such as weight reduction and cost reduction for improving power consumption have been continuously heightened and advanced to a high level.

[0003] In Patent Document 1, the following is described: In a current sensor including a bus bar, a shielding plate, a magnetic detection element, and a conductive plate for the purpose of improving pulse responsiveness, as the bus bar, a plate-shaped good electrical conductor including copper, aluminum, etc. is used.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2019-109126 Summary of the Invention

[0007] -Problems to be Solved by the Invention-

[0008] However, the current sensor described in Patent Document 1 uses a bus bar formed by processing a single good electrical conductor, and does not describe the structure of the bus bar for making the current sensor lightweight and low-cost.

[0009] Therefore, an object of the present invention is to provide a current sensor having a bus bar effective for weight reduction and cost reduction.

[0010] -Means for Solving the Problems-

[0011] The present invention has the following structure as a means for solving the above problems.

[0012] A current sensor, characterized in that it includes a bus bar through which a current to be measured flows, and a magnetic detection unit disposed opposite to the bus bar and sensing a magnetic field generated in the bus bar, the bus bar including a laminated material in which a first metal-based material and a second metal-based material, which are dissimilar metal-based materials, are laminated, the density of the first metal-based material being greater than that of the second metal-based material, the resistivity of the first metal-based material being smaller than that of the second metal-based material, and the magnetic detection unit being disposed opposite to the surface formed by the first metal-based material in the bus bar.

[0013] Through a structure in which two types of metal-based materials are laminated, it is possible to adjust the proportion of metal-based materials with different densities and resistivities, and achieve a balance between reducing the heat generation of the bus bar when the current to be measured flows and lightening the weight of the bus bar.

[0014] Alternatively, in the lamination direction of the bus bar, the size of the second metal-based material may be larger than the size of the first metal-based material.

[0015] Alternatively, in the lamination direction of the bus bar, the size of the second metal-based material may be 80% or more of the size of the laminated material.

[0016] In the case where the magnetic detection unit is disposed opposite to the surface formed by the first metal-based material in the bus bar, through the above structure, it is possible to maintain the frequency characteristics of the bus bar relatively high while achieving heat generation suppression when the current to be measured flows based on the first metal-based material and weight reduction based on the second metal-based material.

[0017] A current sensor, characterized in that it includes a bus bar through which a current to be measured flows, and a magnetic detection unit disposed opposite to the bus bar and sensing a magnetic field generated in the bus bar, the bus bar including a laminated material in which a first metal-based material and a second metal-based material, which are dissimilar metal-based materials, are laminated, the density of the first metal-based material being greater than that of the second metal-based material, the resistivity of the first metal-based material being smaller than that of the second metal-based material, and the magnetic detection unit being disposed opposite to the surface formed by the second metal-based material in the bus bar.

[0018] Through a structure in which two types of metal-based materials are laminated, it is possible to achieve a balance between reducing the heat generation of the bus bar when the current to be measured flows and lightening the weight of the bus bar.

[0019] Alternatively, in the lamination direction of the bus bar, the size of the second metal-based material may be larger than the size of the first metal-based material.

[0020] Alternatively, in the lamination direction of the bus bar, the size of the second metal-based material may be 60% or more of the size of the laminated material.

[0021] In the case where the magnetic detection unit is disposed opposite to the surface of the bus bar formed of the second metal-based material, with the above-described structure, it is possible to maintain the frequency characteristics of the bus bar at a relatively high level, while achieving heat generation suppression when the measured current flows through the first metal-based material and weight reduction based on the second metal-based material.

[0022] A current sensor, characterized in that it includes a plurality of measurement phases, each of the measurement phases including a bus bar through which a measured current flows, and a magnetic detection unit disposed opposite to the bus bar and sensing a magnetic field generated in the bus bar, the bus bar including a laminated material in which a first metal-based material and a second metal-based material, which are different metal-based materials, are laminated, the density of the first metal-based material being greater than that of the second metal-based material, and the resistivity of the first metal-based material being smaller than that of the second metal-based material, the current sensor including: a first measurement phase in which the magnetic detection unit is disposed opposite to the surface of the bus bar formed of the first metal-based material; and a second measurement phase in which the magnetic detection unit is disposed opposite to the surface of the bus bar formed of the second metal-based material.

[0023] Since the resistivity of the first metal-based material is smaller than that of the second metal-based material, more of the measured current flows through the first metal-based material. Therefore, by disposing the magnetic detection unit opposite to the surface formed of the first metal-based material, the magnetic field density sensed by the magnetic detection unit becomes larger, and the sensing accuracy of the first measurement phase becomes better than that of the second measurement phase. Therefore, by setting the measurement phase that requires a higher sensing accuracy as the first measurement phase, it is possible to arrange a plurality of measurement phases according to the required sensing accuracy.

[0024] Alternatively, the second measurement phases may be disposed on both adjacent sides of the first measurement phase.

[0025] In the case where three or more measurement phases are provided, the measurement error of the measurement phase affected by the measurement phases on the adjacent two sides becomes larger. For this reason, in the case where measurement phases are provided on the adjacent two sides, by setting the measurement phases on the adjacent two sides as the second measurement phases and setting the middle measurement phase as the first measurement phase, it is possible to suppress a decrease in the sensing accuracy of the first measurement phase and reduce the difference in the measurement accuracy of the plurality of measurement phases.

[0026] Alternatively, in the stacking direction of the bus bar, the size of the second metal-based material may be larger than the size of the first metal-based material.

[0027] With this structure, it is possible to maintain the frequency characteristics obtained by laminating the second metal-based material and the first metal-based material at a relatively high level, while achieving a balance between weight reduction based on the second metal-based material and heat generation suppression based on the first metal-based material.

[0028] Alternatively, in at least one of the measurement phases, the bus bar has a bent portion, and the magnetic detection portion is arranged at a position where it can sense the induced magnetic fields from two portions of the bus bar that are arranged sandwiching the bent portion.

[0029] With this structure, since the magnetic detection portion can sense the induced magnetic fields from the two portions arranged sandwiching the bent portion, the sensing accuracy of the current sensor is improved.

[0030] Alternatively, a layer of the first metal-based material is provided on the side where the bus bar bends at the bent portion, and the magnetic detection portion is opposed to the layer of the first metal-based material of the bus bar.

[0031] By providing a layer of the first metal-based material on the side where the bent portion bends, the magnetic flux density of the induced magnetic field sensed by the magnetic detection portion increases, and thus the sensing accuracy of the current sensor is improved.

[0032] Alternatively, the first metal-based material is a copper-based material, and the second metal-based material is an aluminum-based material.

[0033] By laminating a copper-based material with a lower resistivity and an aluminum-based material with a smaller density, a lightweight bus bar with excellent frequency characteristics and reduced heat generation is obtained.

[0034] -Advantages of the Invention-

[0035] According to the present invention, by using a laminated material in which different metal-based materials are laminated, the properties of the bus bar can be adjusted, and thus a current sensor suitable for miniaturization and thinning can be provided. Description of the Drawings

[0036] Figure 1A is a top view of the current sensor according to the first embodiment.

[0037] Figure 1B is Figure 1A a cross-sectional view of the current sensor taken along line AA of

[0038] Figure 2 is a graph showing the ratio of the thickness T4 of Al to the total thickness T1 and the simulation results of the bus bar phase characteristics in the case of a bus bar composed of Cu and Al Figure 1B

[0039] Figure 3 is a cross-sectional view of the current sensor provided with a magnetic shield Figure 1B

[0040] Figure 4 is a cross-sectional view of the current sensor according to the second embodiment.

[0041] Figure 5 ​​It shows the ratio of the thickness T4 of Al to the total thickness T1 in the case of a bus bar composed of Cu and Al and the simulation results of the bus bar phase characteristics. Figure 4

[0042] Figure 6 It is a cross-sectional view of a current sensor provided with a magnetic shield. Figure 4

[0043] Figure 7A It is a graph showing the difference in magnetic flux density caused by the lamination order and Al ratio in a bus bar laminated with Al and Cu.

[0044] Figure 7B It is a graph showing the difference in the influence on adjacent bus bars caused by the lamination order and Al ratio in a bus bar laminated with Al and Cu.

[0045] Figure 8 It is a cross-sectional view of a polyphase type current sensor according to the third embodiment.

[0046] Figure 9 It is a perspective view of a polyphase type current sensor according to a modified example.

[0047] Figure 10 It is a perspective view of a polyphase type current sensor according to another modified example.

[0048] Figure 11A It is a top view of a current sensor according to a reference example.

[0049] Figure 11B It is Figure 11A a cross-sectional view of the current sensor at the BB line.

[0050] Figure 12A It shows Figure 11A a graph of the relationship between the frequency and phase angle of the current flowing through the bus bar of the reference example.

[0051] Figure 12B It shows Figure 11A a graph of the relationship between the frequency and gain of the current flowing through the bus bar of the reference example.

[0052] Figure 13A It is a graph showing the temperature change over time when a measured current flows through an existing bus bar with the fastening part made of Al and the main body part made of Al.

[0053] Figure 13B It is a graph showing the temperature change over time when a measured current flows through an existing bus bar with the fastening part made of Cu and the main body part made of Cu.

[0054] Figure 13C It is a graph showing the temperature change over time when a measured current flows through a bus bar in a reference example where the fastening part is made of Cu and the main body part is made of Al.

[0055] Figure 14A It is a top view of a current sensor according to another reference example.

[0056] Figure 14B It is Figure 14A A cross-sectional view of the current sensor at the BB line of

[0057] Figure 15A It is a top view of an existing current sensor.

[0058] Figure 15B It is Figure 15A A cross-sectional view of the current sensor at the AA line of

[0059] Figure 15C It is Figure 15A A cross-sectional view of the current sensor at the BB line of Detailed Description of the Invention

[0060] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same components are given the same reference numerals in each drawing, and the description thereof is omitted. In order to show the positional relationship of each component, a reference coordinate system is appropriately shown in each drawing. The reference coordinate system has the extending direction of the bus bar as the X direction, the direction orthogonal to the X direction on the opposing surface of the bus bar opposing the magnetic detection part as the Y direction, and the direction orthogonal to the X direction and the Y direction as the Z direction. The Y direction is the direction of the sensitivity axis of the magnetic detection part, and the X direction and the Z direction are orthogonal to the sensitivity axis.

[0061] [First Embodiment]

[0062] Figure 15A It is a top view of an existing current sensor 60, Figure 15B It is Figure 15A A cross-sectional view of the current sensor 60 at the AA line of. As shown in these figures, in the existing current sensor 60 including a bus bar 61 and a magnetic detection part 62, as the bus bar 61 through which a measured current flows, a plate-shaped conductor is used. As the material of the conductor, copper, aluminum, etc. are listed, and mostly copper with good conductivity is used alone. However, in the case where the bus bar 61 is composed only of copper, it is sometimes difficult to meet the requirements of high-level and high-level current sensors such as cost reduction and weight reduction. For this reason, in order to achieve cost reduction and weight reduction of the current sensor, the present invention uses a bus bar including a laminated material in which different metal-based materials are laminated.

[0063] Figure 1A AndFigure 1B is a top view of the current sensor 10 according to the present embodiment and Figure 1A a cross-sectional view of the current sensor 10 taken along line AA in the figure. As shown in these figures, the current sensor 10 includes: a bus bar 1 through which a current to be measured flows; and a magnetic detection unit 2 disposed opposite to the bus bar 1 to detect a magnetic field generated in the bus bar 1.

[0064] The bus bar 1 includes a laminated material in which a first metal-based material 3 and a second metal-based material 4, which are dissimilar metal-based materials, are laminated. In the bus bar 1 of the present embodiment, both the first metal-based material 3 and the second metal-based material 4 are formed as layers having a uniform thickness in the Z direction.

[0065] The density of the first metal-based material 3 is greater than that of the second metal-based material 4 (in other words, the first metal-based material 3 is heavier than the second metal-based material 4), and the resistivity (hereinafter, appropriately referred to as "resistivity") is less than that of the second metal-based material 4.

[0066] The magnetic detection unit 2 of the current sensor 10 is disposed opposite to the surface 3S formed by the first metal-based material 3 in the bus bar 1.

[0067] As the first metal-based material 3, for example, a copper-based material can be used, and as the second metal-based material 4, an aluminum-based material can be used. The copper-based material refers to pure copper, copper alloy, and conductive materials containing them, and the aluminum-based material refers to pure aluminum, aluminum alloy, and conductive materials containing them.

[0068] Hereinafter, a case where Cu (pure copper) is used as the copper-based material and Al (pure aluminum) is used as the aluminum-based material will be described as an example. Since Al has a smaller specific gravity and density and is cheaper than Cu, a bus bar including Al is advantageous in terms of weight reduction and cost reduction compared to a bus bar including Cu.

[0069] However, since the resistivity of Al is 2.65×10 -8 [Ω·m], which is greater than the resistivity of Cu of 1.68×10 -8 [Ω·m], when the material of the bus bar is Al, the resistivity of the bus bar becomes larger. Therefore, due to the influence of the heat generation of the bus bar when the current to be measured flows, the temperature of the magnetic detection unit 2 rises, and when it exceeds its heat-resistant temperature, there is a concern that a problem such as a decrease in the sensing accuracy of the current sensor 10 may occur.

[0070] Figure 2 shows for Figure 1BA graph of the results of simulations in which the thicknesses T3 of Cu and T4 of Al in the Z direction were varied for the bus bar 1 of the laminated material shown. The horizontal axis in this graph represents the ratio T4 / T1×100 (%) of the thickness T4 of Al to the total thickness T1 = T3 + T4 of Cu and Al.

[0071] The simulation was performed on Figure 2 bus bar 1 having a laminated structure as shown in Figure 1B which, on the Z2 side as the magnetic detection unit 2 side, a Cu layer as the first metal-based material 3 is disposed, and on the Z1 side opposite to the magnetic detection unit 2, an Al layer as the second metal-based material 4 is disposed.

[0072] Figure 2 The graph shows that when the phase characteristic on the vertical axis is 0.0°, it is an ideal state where there is no delay in the output voltage of the current sensor 10 with respect to the measured current. The further downward on the vertical axis (-1.0° side), the greater the delay in the output voltage. When this delay is large, the time delay of the output voltage of the current sensor 10 with respect to the measured current becomes large in the high frequency band. Therefore, it can be said that the phase characteristic on the vertical axis preferably approaches 0.0°. In this graph, it is shown that the delay of the output voltage of the current sensor 10 is minimized in the case of the bus bar 1 having an Al ratio of 100%, and there is an inflection point in the phase characteristic in the Al ratio of 60 - 80%.

[0073] According to Figure 2 the results shown, from the viewpoints of suppressing the deterioration of the frequency characteristics of the bus bar 1 related to the delay of the output voltage of the current sensor 10 and achieving weight reduction, it can be said that the size of the second metal-based material 4 in the lamination direction, i.e., the thickness T4, is preferably larger than the size of the first metal-based material 3, i.e., the thickness T3. Further, when the size of the bus bar 1 including the laminated material in the lamination direction, i.e., the thickness T1 (= T3 + T4), is set to 100%, it is more preferable that the thickness T4 of the second metal-based material 4 is 80% or more.

[0074] Figure 3 A cross-sectional view of the current sensor 10 provided with magnetic shields 5A and 5B. As shown in this figure, the current sensor 10 can also be provided with magnetic shields 5A and 5B on both sides in the Z direction so as to sandwich the bus bar 1 and the magnetic detection unit 2. Since the magnetic noise from the outside to the magnetic detection unit 2 can be suppressed by the magnetic shields 5A and 5B, the measurement accuracy of the current sensor 10 is improved. In addition, it can also be configured such that a magnetic shield is provided only on the Z1 side of the bus bar 1 or only on the Z2 side of the magnetic detection unit 2 (a structure in which only either of the magnetic shields 5A and 5B is provided).

[0075] The magnetic shielding members 5A and 5B use, for example, a member in which a plurality of metal plate-like bodies having the same shape are stacked. In addition, in each of the drawings used in the description, the member in which a plurality of plate-like bodies are stacked is simplified and the magnetic shielding members 5A and 5B are illustrated as a single plate-like body.

[0076] Instead of Figure 3 the flat plate type magnetic shielding members 5A and 5B shown, Figure 1A a U-shaped magnetic shielding member having a U-shaped cross section at the AA line may be used. More specifically, the shape of the bus bar 1 may be set to a U shape formed by both sides in the Y direction and the Z1 direction side of the bus bar 1, and a U-shaped magnetic shielding member that surrounds the magnetic detection unit 2 may be used.

[0077] [Second Embodiment]

[0078] Figure 4 is a cross-sectional view of the current sensor 11 according to the present embodiment.

[0079] The current sensor 11 of the present embodiment is the same in that the laminated material constituting the bus bar 1 is formed by laminating the first metal-based material 3 and the second metal-based material 4. However, the magnetic detection unit 2 is different from the current sensor 10 in that it is arranged to face the surface 4S formed of the second metal-based material 4 in the bus bar 1, and the magnetic detection unit 2 is arranged to face the surface 3S formed of the first metal-based material 3 in the bus bar 1.

[0080] Figure 5 is shown as Figure 4 In the case of using a laminated material in which the first metal-based material 3 is Cu and the second metal-based material 4 is Al as the bus bar 1 shown, a graph showing the results of simulation with the thickness T3 of Cu and the thickness T4 of Al in the Z direction changed. The horizontal axis in this graph represents the ratio of the thickness T4 of Al in the thickness T1 of the bus bar 1.

[0081] Figure 5 The bus bar 1 in which the simulation of the results was performed in Figure 4 has the laminated structure shown, and an Al layer as the second metal-based material 4 is arranged on the magnetic detection unit 2 side, and a Cu layer as the first metal-based material 3 is arranged on the opposite side of the magnetic detection unit 2 with the layer of the second metal-based material 4 interposed therebetween.

[0082] Figure 5 The vertical axis and the horizontal axis in the graph of Figure 2 represent the same content as the graph of

[0083] According toFigure 5 In the shown result, when the magnetic detection unit 2 side is arranged to face the surface 4S of the Al layer which is the second metal-based material 4, from the viewpoints of suppressing the deterioration of the frequency characteristics of the bus bar 1 related to the delay of the output voltage of the current sensor 10 and achieving weight reduction, it can be said that the size of the second metal-based material 4 in the stacking direction, that is, the Z direction, namely the thickness T4, is preferably greater than the size of the first metal-based material 3, that is, the thickness T3. Further, when the size of the bus bar 1 including the stacked material in the stacking direction, that is, the thickness T1, is set to 100%, it is more preferably that the thickness T4 of the second metal-based material 4 is 60% or more.

[0084] Figure 6 It is a cross-sectional view of the current sensor 11 provided with the magnetic shields 5A and 5B. As shown in this figure, the current sensor 11 can also be provided with the magnetic shields 5A and 5B on both sides in the Z direction so as to sandwich the bus bar 1 and the magnetic detection unit 2. Since the magnetic noise from the outside to the magnetic detection unit 2 can be suppressed by the magnetic shields, the measurement accuracy of the current sensor 10 is improved.

[0085] The current sensors of the first embodiment and the second embodiment described above include a bus bar formed by laminating two types of metal-based materials. Therefore, it is possible to adjust the ratio of the metal-based materials with different densities and resistivities, and achieve a reduction in the heat generation amount of the bus bar when the measured current flows through and a weight reduction of the bus bar.

[0086] [Third Embodiment]

[0087] In the present embodiment, a mode of implementing the present invention for a multi-phase type current sensor will be described.

[0088] Figure 7A It is a graph showing the simulation results of the difference in magnetic flux density near the bus bar 1 caused by the lamination order of Al and Cu and the Al ratio when Cu is used as the first metal-based material 3 and Al is used as the second metal-based material 4 in a multi-phase type current sensor having a plurality of measurement phases. The Al ratio in this figure represents the same content as the simulation related to the frequency characteristics in the first embodiment and the second embodiment.

[0089] The result shown as Cu / Al is the result of the simulation of the current sensor 10 (refer to FIG. 1) provided with the magnetic detection unit 2 on the surface 3S on the Cu side which is used as the first metal-based material 3.

[0090] The result shown as Al / Cu is for the current sensor 11 (refer to Figure 4 ) provided with the magnetic detection unit 2 on the surface 4S on the Al side which is used as the second metal-based material 4.

[0091] In addition, the simulations of Cu / Al and Al / Cu were carried out under the same conditions except for the stacking order.

[0092] As Figure 7A shown, it can be seen that the magnetic flux density near the bus bar 1 is different depending on whether the magnetic detection unit 2 is provided on the 3S surface on the Cu side or the 4S surface on the Al side. The reason for this result is considered to be that when the measured current flows through the bus bar 1 of the laminated material including dissimilar metals, more current flows through the Cu side with lower resistivity than the Al side with higher resistivity.

[0093] Furthermore, according to the results shown as Cu / Al, by using a laminated material, the magnetic flux density increases compared with the case where the bus bar 1 is composed only of Cu (Al ratio 0%) and the case where the bus bar 1 is composed only of Al (Al ratio 100%). Thus, by forming the bus bar 1 from a laminated material, the magnetic flux density detected by the magnetic detection unit 2 becomes larger, and the measurement accuracy of the current sensor is improved.

[0094] Figure 7B is a graph showing the differences in the effects of the stacking order of Al and Cu and the Al ratio on adjacent bus bars in a multi-phase type current sensor having a plurality of measurement phases. The results shown in this figure show the magnitude of the error generated in the middle current sensor when the current sensors having bus bars are arranged in three phases and measured under the same conditions, and the bus bar includes the same laminated material. In addition, Cu / Al and Al / Cu represent the differences in the stacking order of the bus bars described Figure 7A above.

[0095] According to Figure 7B the results of Cu / Al shown, in the case of a multi-phase type current sensor, by using a laminated material for the bus bar, it is more strongly affected by the adjacent bus bar compared with the case where the bus bar is composed only of Cu (Al ratio 0%) and the case where the bus bar is composed only of Al (Al ratio 100%). This is considered to be because, by using a laminated material in which different metal-based materials are laminated for the bus bar, the difference in the magnetic flux density in the Z direction in the induced magnetic field generated when the measured current flows is larger than that of the bus bar using a single metal-based material.

[0096] Furthermore, according to Figure 7BAs can be seen from the results shown, the influence from the adjacent bus bars is smaller for the Cu / Al with the magnetic detection unit 2 provided on the surface 3S on the Cu side than for the Al / Cu with the magnetic detection unit 2 provided on the surface 4S on the Al side. It is considered that this is because, in the bus bar 1, the current density of the measured current flowing through the side of the first metal-based material 3 with a lower resistivity is higher than that of the side of the second metal-based material 4 with a higher resistivity, and the magnetic flux density measured by the magnetic detection unit 2 increases.

[0097] Figure 8 FIG. is a cross-sectional view showing a polyphase type current sensor 30 of the present embodiment.

[0098] As shown in this figure, the current sensor 30 includes a plurality of measurement phases 20, and each measurement phase 20 includes a bus bar 1 through which a measured current flows, and a magnetic detection unit 2 that is disposed opposite to the bus bar 1 and senses the magnetic field generated in the bus bar 1.

[0099] The current sensor 30 includes a first measurement phase 20A and a second measurement phase 20B. The magnetic detection unit 2 of the first measurement phase 20A is disposed to face the surface 3S of the bus bar 1 formed of the first metal-based material 3, and the magnetic detection unit 2 of the second measurement phase 20B is disposed to face the surface 4S of the bus bar 1 formed of the second metal-based material 4.

[0100] Since the resistivity of the first metal-based material 3 is smaller than that of the second metal-based material 4, more of the measured current flows through the side of the first metal-based material 3. Therefore, by disposing the magnetic detection unit 2 to face the surface 3S formed of the first metal-based material 3, the magnetic field density of the induced magnetic field of the measured current sensed by the magnetic detection unit 2 becomes larger. Therefore, the first measurement phase 20A has better sensing accuracy than the second measurement phase 20B.

[0101] For example, when the sensing accuracies required for the respective measurement phases 20 in the current sensor 30 including a plurality of measurement phases 20 are different, the first measurement phase 20A or the second measurement phase 20B can be selectively disposed according to the required sensing accuracy.

[0102] In Figure 8 In the current sensor 30 shown, three measurement phases 20 are arranged in parallel along the Y direction. The measurement phase 20 disposed in the middle among the three measurement phases 20 is affected by the adjacent measurement phases 20 on both sides in the Y direction, and thus the error becomes larger. For this reason, the middle measurement phase 20 is set as the first measurement phase 20A, and the measurement phases 20 on both sides are set as the second measurement phase 20B, whereby it is possible to suppress a decrease in the sensing accuracy of the middle measurement phase 20 and reduce the difference in the measurement accuracy between the plurality of measurement phases 20.

[0103] In addition, in all of the plurality of measurement phases 20 of the current sensor 30, on the same side of the bus bar 1 ( Figure 8On the Z2 side (the middle one), a magnetic detection unit 2 is provided. In this case, with the structure where the second measurement phase 20B is arranged on both adjacent sides of the first measurement phase 20A, the distance between the magnetic detection unit 2 in the first measurement phase 20A and the first metal-based material 3 of the bus bar 1 in the second measurement phases 20B on both sides becomes larger. In addition, more of the measured current flowing through the bus bar 1 flows through the first metal-based material 3 side. Therefore, the distance between the generation source of the induced magnetic field in the second measurement phases 20B arranged on both sides of the first measurement phase 20A and the magnetic detection unit 2 in the first measurement phase 20A arranged in the middle becomes larger. Therefore, the influence of the magnetic field from the bus bar 1 of the adjacent second measurement phase 20B on the first measurement phase 20A can be reduced. Therefore, it is preferable that the bus bar 1 of the measurement phase 20 arranged on both adjacent sides of the first measurement phase 20A has the first metal-based material 3 laminated on the Z1 side at a distance farther from the magnetic detection unit 2 of the first measurement phase 20A.

[0104] From the viewpoint of achieving good frequency characteristics, the current sensor 30 having Figure 8 the plurality of measurement phases 20 shown preferably has the thickness T4 of the second metal-based material 4 greater than the thickness T3 of the first metal-based material 3 in the lamination direction of the first metal-based material 3 and the second metal-based material 4, that is, in the Z direction (refer to Figure 1B , Figure 4 ).

[0105] As described in the first embodiment and the second embodiment, when the magnetic detection unit 2 faces the surface 3S formed by the first metal-based material 3, the thickness T4 of the second metal-based material 4 is preferably greater than 50% of the thickness of the bus bar 1 in the lamination direction, and more preferably 80% or more. In addition, when the magnetic detection unit 2 faces the surface 4S formed by the second metal-based material 4, the thickness T4 of the second metal-based material 4 is preferably greater than 50% of the thickness of the bus bar 1 in the lamination direction, and more preferably 60% or more.

[0106] As described above, the following structure is adopted: in the middle measurement phase 20 among the three adjacent measurement phases 20 that is liable to be affected by the induced magnetic field of the adjacent measurement phase 20, the first metal-based material 3 is arranged on the magnetic detection unit 2 side of the bus bar 1, and the second metal-based material 4 is arranged on the magnetic detection unit 2 side of the bus bars 1 on both sides. According to this structure, the influence from the adjacent bus bar 1 on the magnetic detection unit 2 facing the bus bar 1 in the middle can be reduced.

[0107] In addition, in the case of a current sensor including two adjacent measurement phases 20, if the measurement phase 20 with relatively higher required precision is set as the first measurement phase 20A, and the measurement phase 20 with lower required precision is set as the second measurement phase 20B, a structure corresponding to the required precision can be achieved.

[0108] [Modification Example]

[0109] Figure 9 is a perspective view showing the multiphase current sensor 31 according to the modification example.

[0110] The current sensor 31 sets the middle measurement phase 20 among the three adjacent measurement phases 20 as the first measurement phase 20A, and the measurement phases 20 on both sides as the second measurement phase 20B. In addition, the bus bar 1 includes a first part 1X1 and a first part 1X2 extending in the X direction, and a second part 1Z extending in the Z direction. The first part 1X1 and the second part 1Z are connected by a bending part 1B1, and the first part 1X2 and the second part 1Z are connected by a bending part 1B2. When observing the bus bar 1 from the Y direction, the bending part 1B1 and the bending part 1B2 are configured in a crank shape bent 90 degrees in opposite directions.

[0111] The bus bar 1 of the first measurement phase 20A has a bending part 1B2 on the Z2 direction side and a bending part 1B1 on the Z1 direction side. The bending part 1B2 includes the second part 1Z and the first part 1X2 extending from the end on the Z2 direction side to the X2 side, and the bending part 1B1 includes the second part 1Z and the first part 1X1 extending from the end on the Z1 direction side to the X1 side. In the bending part 1B2 on the Z2 direction side, the second metal-based material 4 is inside the bending part 1B2, and in the bending part 1B1 on the Z1 direction side, the first metal-based material 3 is inside the bending part 1B1.

[0112] In addition, Figure 9 shows a bus bar 1 having two first parts 1X1, a first part 1X2, and a second part 1Z, and having bending parts 1B1 and 1B2 at both ends in the Z direction of the second part 1Z. However, it may also be configured to have a structure including the first part 1X1, the second part 1Z, and the bending part 1B1, or a structure including the first part 1X2, the second part 1Z, and the bending part 1B2. In addition, a mode in which all three measurement phases 20 are provided with bending parts 1B1 and 1B2 is shown, but it may also be configured such that one or two of the three measurement phases 20 are provided with at least one of the bending parts 1B1 and 1B2. In addition, in the case of the bus bar 1 having only the bending part 1B1 or the bending part 1B2, the magnetic detection part 2 is arranged on the inner side, that is, the side where the bending part 1B1 or the bending part 1B2 is bent.

[0113] The magnetic detection part 2 is arranged at a position where it can sense the induction magnetic field Mx from the first part 1X1 in contact with the bending part 1B1 and the induction magnetic field Mz from the second part 1Z. The two parts of the bus bar 1 provided with the bending part 1B1 interposed therebetween are the first part 1X1 in contact with the bending part 1B1 and the second part 1Z.

[0114] In addition, the induced magnetic fields Mx and Mz in this modification are magnetic fields each including a component in the Y direction, and the magnetic detection unit 2 is arranged such that the sensing direction of the magnetic detection unit 2 is parallel to the Y direction. That is, the magnetic detection unit 2 senses the combined component of the component in the Y direction of the induced magnetic field Mx and the component in the Y direction of the induced magnetic field Mz.

[0115] The position of the magnetic detection unit 2 is a position capable of sensing the aforementioned induced magnetic fields Mx and Mz, and the magnitude of the combined component of the component in the Y direction of the induced magnetic field Mx and the component in the Y direction of the induced magnetic field Mz is desirably a magnitude that can be easily sensed by the magnetic detection unit 2. According to this structure, the induced magnetic field generated when the measured current flows through the bus bar 1 can be efficiently detected by the magnetic detection unit 2. In addition, the magnetic detection unit 2 of the middle first measurement phase 20A is arranged to face the surface 3S of the layer of the first metal-based material 3 of the bus bar 1, so the magnetic flux density of the magnetic field generated when the measured current flows is high. Therefore, the magnetic sensing accuracy of the magnetic detection unit 2 is improved.

[0116] In the Z direction, when the magnetic detection units 2 are provided on the same side of the bus bar 1, by the structure in which the second measurement phases 20B are arranged on both adjacent sides of the first measurement phase 20A, the distance between the magnetic detection unit 2 of the first measurement phase 20A and the first metal-based material 3 of the bus bar 1 of the second measurement phase 20B becomes larger. Therefore, the influence of the magnetic field from the second measurement phase 20B on the middle first measurement phase 20A can be reduced. This effect is obtained in the first part 1X1 and the second part 1Z, so the sensing accuracy of the current sensor 31 becomes good.

[0117] Figure 10 is a perspective view showing a multi-phase type current sensor 32 according to another modification. In the current sensor 32 shown in this figure, the structure in which the magnetic detection units 2 are arranged inside the bending portions 1B2 in the two side measurement phases 20 is different from Figure 9 that of the current sensor 31.

[0118] In the current sensor 32, the arrangement of the bus bars of the three arranged measurement phases 20 is the same as that of the Figure 9 shown modification. Regarding the arrangement of the magnetic detection units 2, in the middle measurement phase 20, the magnetic detection unit 2 and Figure 9Similarly to the illustrated modification example, a magnetic detection unit 2 is disposed opposite to the surface 3S of the layer of the first metallic material 3 of the first part 1X1 on the Z1 side and the second part 1Z. In contrast, in the measurement phases 20 on both sides, a magnetic detection unit 2 is disposed opposite to the surface 3S of the layer of the first metallic material 3 of the first part 1X2 on the Z2 side of the bus bar 1 and the second part 1Z. That is, the magnetic detection unit 2 is disposed such that all three arranged measurement phases 20 become the first measurement phase 20A. In this way, by disposing the magnetic detection units 2 of the measurement phases 20 on both sides opposite to the surface 3S of the first metallic material 3 of the bus bar 1, the magnetic flux density detected by the magnetic detection unit 2 increases, and the sensing accuracy of the measurement phase 20 is improved.

[0119] [Reference Example]

[0120] Figure 11A It is a top view of the current sensor 50 according to the reference example.

[0121] Figure 11B is Figure 11A A cross-sectional view of the current sensor 50 at the BB line of.

[0122] As shown in these figures, a magnetic detection unit 52 is disposed opposite to the bus bar 51 in the current sensor 50. The bus bar 1 of the current sensor 50 is composed of different types of metallic materials for the fastening part 51A and the main body part 51B including the reduced-diameter part opposite to the magnetic detection unit 52.

[0123] For example, the fastening part 51A is set as Cu as the first metallic material 53, and the main body part 51B is set as Al as the second metallic material 54. Thus, compared with Figure 15C the case where the fastening part 61A and the main body part 61B of the bus bar 61 of the existing current sensor 60 shown are made of Al, the contact resistance of the fastening part 51A can be reduced, and the heat generation caused by the measured current can be suppressed. In addition, by suppressing the skin effect in the bus bar 51, the frequency characteristics of the magnetic flux density detected by the magnetic detection unit 52 can be improved.

[0124] The following table shows the frequency characteristics (phase characteristics) of Cu and Al.

[0125] [Table 1]

[0126]

[0127] [Table 2]

[0128]

[0129] The skin depth in Table 2 refers to the distance at which the electromagnetic field incident on a certain material attenuates to 1 / e (≈1 / 2.718≈ -8.7 db).

[0130] When a high-frequency current flows through a conductor, most of the current concentrates in an extremely narrow region near the surface of the conductor. This means that the resistance of the conductor substantially increases at high frequencies, and while a reduction in resistance due to thickening the conductor can be expected in the case of low frequencies, it has no effect at high frequencies. Therefore, from the perspective of frequency characteristics, it can be said that Al with a larger skin depth is more preferable than Cu.

[0131] Figure 12A It is a graph showing the simulation results of the relationship between the frequency of the measured current and the phase angle for a current sensor 50 which is a reference example with a bus bar 51 having a fastening part 51A made of Cu and a main body part 51B made of Al, and an existing current sensor 60 having a bus bar 61 with a fastening part 61A and a main body part 61B made of Cu.

[0132] Figure 12A The value (phase angle) on the vertical axis of the graph is larger (closer to 0), indicating a state where the detection voltage has no delay with respect to the measured current, that is, a good state. From this graph, it can be seen that compared with the current sensor 60, even when the frequency of the measured current increases, the phase angle of the current sensor 50 is larger and the detection voltage has no delay with respect to the measured current.

[0133] Figure 12B It is for Figures 11A to 11B the current sensor 50 of the reference example shown in Figures 15A to 15C and the existing current sensor 60 shown in

[0134] Figure 12B a graph showing the simulation results of the relationship between the frequency of the measured current and the gain. The larger the value (gain) on the vertical axis of the graph (closer to 1), the more it shows a state where a detection voltage equivalent to the measured current can be output, that is, a good state. From this graph, it can be seen that compared with the current sensor 60, even when the frequency of the measured current increases, the value on the vertical axis of the current sensor 50 is larger and it can output a detection voltage equivalent to the measured current.

[0135] According to Figure 12A and Figure 12B the results of these graphs shown in

[0136] Figure 13A It is a graph showing the measurement results of the temperature change of the necking parts of the fastening part 61A and the main body part 61B over time as a measured current flows through the existing current sensor 60 having a bus bar 61 with a fastening part 61A and a main body part 61B made of Al.

[0137] Figure 13B It is a graph showing the measurement results of the temperature changes in the necked-down portions of the fastening portion 61A and the main body portion 61B of the bus bar 61 having the fastening portion 61A made of Cu and the main body portion 61B with respect to the existing current sensor 60 as time passes while the measured current flows.

[0138] Figure 13C It is a graph showing the measurement results of the temperature changes in the necked-down portions of the fastening portion 51A and the main body portion 51B of the bus bar 51 of a reference example having the fastening portion 51A made of Cu and the main body portion 51B made of Al as time passes while the current flows under the same conditions.

[0139] According to Figures 13A to 13C the results shown, compared with the bus bar 61 made only of Cu, the temperature of the bus bar 61 made only of Al is more likely to rise due to the flow of the measured current. However, for the bus bar 51 having the fastening portion 51A made of Cu and the main body portion 51B made of Al, the necked-down portions of both the fastening portion 51A and the main body portion 51B suppressed the temperature rise caused by the flow of the measured current in the same manner as in the case of the bus bar 61 made only of Cu.

[0140] According to Figures 13A to 13C the comparison of the graphs, it can be seen the differences in the temperature changes of each part in the state where the measured current continuously flows due to the differences in the materials of the fastening portion and the main body portion. Figure 13A For the bus bar 61 made entirely of AI shown, compared with Figure 13B the bus bar 61 made entirely of Cu shown, the heat generation is very large. By simply maintaining the main body portion as Al and setting the fastening portion as Cu, as shown in Figure 13C the graph of, the heat generation of the bus bar 51 is significantly suppressed. In addition, in each graph, near 60 minutes, the final temperature drops because the measured current is stopped.

[0141] Based on this result, it can be said that the structure with the fastening portion 51A made of Cu and the main body portion 51B made of Al is effective for reducing the delay of the detection voltage with respect to the measured current, improving the gain, and suppressing the temperature rise when the measured current flows.

[0142] Figure 14A It is a top view of the current sensor 50 related to another reference example.

[0143] Figure 14B It is Figure 14A a cross-sectional view of the current sensor 50 at the BB line of.

[0144] As shown in these figures, even if the fastening portion 51A of the bus bar 51 in the current sensor 50 is configured such that the Z-axis direction surface of Al is covered with Cu, it is possible to reduce the temperature rise when the measured current flows.

[0145] The embodiments disclosed in this specification are illustrative in all aspects and are not limited to these embodiments. The scope of the present invention is shown not only by the description of the above embodiments but also by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0146] Industrial Applicability

[0147] The present invention is useful as a current sensor that is installed in various devices to measure a measured current in order to control or monitor the various devices.

[0148] - Symbol Explanation -

[0149] 1: Bus bar

[0150] 1B1: Bending portion

[0151] 1B2: Bending portion

[0152] 1X1: First portion

[0153] 1X2: First portion

[0154] 1Z: Second portion

[0155] 2: Magnetic detection portion

[0156] 3: First metal-based material

[0157] 3S: Surface

[0158] 4: Second metal-based material

[0159] 4S: Surface

[0160] 5A: Magnetic shield

[0161] 5B: Magnetic shield

[0162] 10: Current sensor

[0163] 11: Current sensor

[0164] 20: Measurement phase

[0165] 20A: First measurement phase

[0166] 20B: Second measurement phase

[0167] 30: Current sensor

[0168] 31: Current sensor

[0169] 32: Current sensor

[0170] 50: Current sensor

[0171] 51: Bus bar

[0172] 51A: Fastening part

[0173] 51B: Main body part

[0174] 52: Magnetic detection part

[0175] 53: First metal-based material

[0176] 54: Second metal-based material

[0177] 60: Current sensor

[0178] 61: Bus bar

[0179] 61A: Fastening part

[0180] 61B: Main body part

[0181] 62: Magnetic detection part

[0182] Mx: Induced magnetic field

[0183] Mz: Induced magnetic field

[0184] T1: Thickness

[0185] T3: Thickness

[0186] T4: Thickness.

Claims

1. A current sensor includes a bus bar through which a current to be measured flows, and a magnetic detection unit that is disposed opposite to the bus bar and senses a magnetic field generated in the bus bar. The bus bar includes a laminated material in which a first metal-based material and a second metal-based material, which are different metal-based materials, are laminated. The density of the first metal-based material is greater than that of the second metal-based material, and the resistivity of the first metal-based material is smaller than that of the second metal-based material. The magnetic detection unit is disposed opposite to the surface of the bus bar formed by the first metal-based material.

2. The current sensor according to claim 1, wherein in the lamination direction, the size of the second metal-based material is larger than the size of the first metal-based material.

3. The current sensor according to claim 1, wherein in the lamination direction, the size of the second metal-based material is 80% or more of the size of the laminated material.

4. A current sensor includes a bus bar through which a current to be measured flows, and a magnetic detection unit that is disposed opposite to the bus bar and senses a magnetic field generated in the bus bar. The bus bar includes a laminated material in which a first metal-based material and a second metal-based material, which are different metal-based materials, are laminated. The density of the first metal-based material is greater than that of the second metal-based material, and the resistivity of the first metal-based material is smaller than that of the second metal-based material. The magnetic detection unit is disposed opposite to the surface of the bus bar formed by the second metal-based material.

5. The current sensor according to claim 4, wherein in the lamination direction, the size of the second metal-based material is larger than the size of the first metal-based material.

6. The current sensor according to claim 4, wherein in the lamination direction, the size of the second metal-based material is 60% or more of the size of the laminated material.

7. A current sensor includes a plurality of measurement phases, and each measurement phase includes a bus bar through which a current to be measured flows, and a magnetic detection unit that is disposed opposite to the bus bar and senses a magnetic field generated in the bus bar. The bus bar includes a laminated material in which a first metal-based material and a second metal-based material, which are different metal-based materials, are laminated. The density of the first metal-based material is greater than that of the second metal-based material, and the resistivity of the first metal-based material is smaller than that of the second metal-based material. The current sensor includes: a first measurement phase in which the magnetic detection unit is disposed opposite to the surface of the bus bar formed by the first metal-based material; and a second measurement phase in which the magnetic detection unit is disposed opposite to the surface of the bus bar formed by the second metal-based material.

8. The current sensor according to claim 7, wherein the second measurement phases are disposed on both sides adjacent to the first measurement phase.

9. The current sensor according to claim 7, wherein in the lamination direction, the size of the second metal-based material is larger than the size of the first metal-based material.

10. The current sensor according to claim 7, wherein in at least one of the measurement phases, the bus bar has a bent portion. The magnetic detection unit is arranged at a position capable of sensing the induced magnetic fields from two portions of the bus bar that are arranged sandwiching the bent portion.

11. The current sensor according to claim 10, wherein a layer of the first metal-based material is provided on a side of the bus bar where the bus bar is bent at the bent portion, and the magnetic detection unit is opposed to the layer of the first metal-based material of the bus bar.

12. The current sensor according to claim 1, 4 or 7, wherein the first metal-based material is a copper-based material, and the second metal-based material is an aluminum-based material.

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