Current sensor

Abstract

This current sensor 1 includes a bus bar 2 through which a current to be measured flows, a magnetic sensor 3 that detects magnetism generated by the current to be measured, and a case 4 that holds the magnetic sensor 3. The current sensor comprises a fixture 5 that connects the bus bar 2 and the case 4 and holds the bus bar 2 at a position separated from the case 4. Therefore, even when heat generation from the bus bar 2 increases in conjunction with an increase in the current to be measured, the positional relationship between the bus bar 2 and a magnetic detection unit (magnetic sensor 3) can be maintained, and errors due to positional deviation are small, resulting in good measurement accuracy.

Description

Current sensor

[0001] The present invention relates to a current sensor suitable for measuring large currents.

[0002] In recent years, a power semiconductor (power module) has been used as a means for controlling a power supply system such as a vehicle equipped with various devices. The power semiconductor includes a current sensor used for measuring a measured current flowing through the device, and various types of such current sensors have been proposed.

[0003] Patent Document 1 aims to provide a technique for improving output characteristics and taking thermal countermeasures. It includes a circuit board carrying a conductive pattern and circuit elements constituting a current detection circuit, and a heat dissipation path that conducts heat from the conductive pattern to the outside of the circuit board when the circuit elements generate heat and releases it. The constituent member of the heat dissipation path is a shielding heat radiator that reduces capacitive coupling generated between the current detection circuit and the primary conductor.

[0004] Patent Document 2 aims to ensure the earthquake resistance of a current sensor while suppressing cost increase. A resin case is provided on a surface facing the circuit board, and in a direction along the circuit board, a plurality of pedestals that support the circuit board are arranged with a space between them across a current detection element. The plurality of pedestals include a first pedestal where a fastening member is arranged at a location where the circuit board is fastened to the resin case, and a second pedestal having a higher height from the facing surface than the first pedestal.

[0005] Patent Document 3 aims to provide a technique for realizing miniaturization of a connection box that integrates control circuits and the like of various electrical components of an automobile. A current sensor is described in which one of a plurality of busbars mounted on a battery pack, which is a detection object, has a special shape.

[0006] Japanese Patent Application Laid-Open No. 2020-85676, Japanese Patent Application Laid-Open No. 2024-10331, International Publication No. 2012 / 026509

[0007] The current supplied from power semiconductors to EV motors exceeds 1000 Arms at its maximum, and the continuously supplied current is several hundred Arms. However, with the advancement of motor miniaturization and increased power output, the continuously supplied current is expected to increase. Consequently, the current being measured, which is continuously supplied to the busbar that is the target of current sensors, will also increase.

[0008] Current sensors often employ configurations where the busbar is fixed by insert molding into the case or by sandwiching it between the case and cover, because the measurement accuracy decreases if the busbar and magnetic sensor are misaligned from their predetermined positions. When a current exceeding 500A is continuously passed through a current sensor with such a configuration, it is expected that the temperature will exceed 300°C due to self-heating, even when using a busbar with low resistance, such as one made of oxygen-free copper. Thermoplastic resins commonly used for cases usually soften at temperatures below 300°C. If the case in which the busbar is fixed by insert molding softens, there is a risk that the busbar will no longer be able to be held in its predetermined position. However, the current sensors (current detectors) described in Patent Documents 1 to 3 do not take into consideration the problem of misalignment between the busbar and magnetic sensor that may occur due to increased heat generation from the busbar as the current being measured increases. Therefore, the present invention aims to provide a current sensor with good measurement accuracy that can maintain the positional relationship between the busbar and the magnetic detection unit even when the heat generated from the busbar increases with the increase in the current being measured, thereby suppressing errors due to positional misalignment.

[0009] As a means to solve the above-mentioned problems, the present invention has the following configuration: a current sensor comprising a busbar through which a current to be measured flows, a magnetic sensor for detecting the magnetism generated by the current to be measured, and a case for holding the magnetic sensor, wherein the current sensor is equipped with a mounting device that connects the busbar and the case and holds the busbar at a position away from the case.

[0010] The busbar is held outside the case via a mounting bracket and positioned away from the case. This configuration prevents the heat generated by the current being measured flowing through the busbar from directly transferring to the case. In other words, even if a large current flows through the busbar and it heats up to a temperature that softens the case, the heat generated in the busbar will be transferred to the case via the mounting bracket and air. Therefore, the heat generated in the busbar will cool down before it reaches the case, suppressing the softening of the case. Thus, the softening of the case due to the heat generated by the busbar can be suppressed, and the positional relationship between the busbar and the magnetic sensor can be maintained.

[0011] The case may have a portion made of thermoplastic resin. By holding the busbar to the case via a mounting device, the impact of heat generated by the busbar on the case can be reduced, and softening of the portion made of thermoplastic resin can be suppressed.

[0012] The case has a base portion that supports the mounting fixture, and when the direction in which the busbar and the magnetic sensor face each other is designated as a first direction, the direction of current flow in the portion of the busbar facing the magnetic sensor is designated as a second direction, and the direction of current flow in the portion of the busbar facing the magnetic sensor is designated as a third direction, the mounting fixture comprises a holding portion that holds the busbar at one end in the first direction, a leg portion supported by the base portion at the other end in the first direction, and a connecting portion that extends to connect the leg portion and the holding portion, wherein the extending direction of the connecting portion has a component in the third direction, and the leg portion may be distal to the busbar than the holding portion when viewed in the first direction. The busbar has a plate-like portion whose normal to its main surface is along the first direction, and the holding portion may hold the busbar at the plate-like portion.

[0013] The direction in which heat from a busbar is most easily transferred is the first direction, where the busbar and the magnetic sensor face each other. If the busbar is a plate-like body and faces the magnetic sensor in the direction normal to the main surface of the plate-like body (first direction), the heat from the busbar is relatively less likely to be transferred in the direction tilted relative to the first direction. Since the busbar extends in the second direction, which is the direction of current flow, extending the connecting portion in a direction that has a component in the third direction, which is the width direction of the busbar, makes it difficult for the heat generated by the busbar to be transferred to the base of the case, thus suppressing the softening of the case due to the heat generated by the busbar. Furthermore, with a configuration in which the connecting portion extends in a direction that has a component in the third direction, it becomes unnecessary to take a distance that takes into account the effect of heat, compared to when the connecting portion is provided along the first direction, so the current sensor can be made lower in height to a size that prioritizes magnetic design over the effect of heat.

[0014] The extending direction of the connecting portion may have a component of the first direction. When the extending direction of the connecting portion has components of the first and third directions, the connecting portion extends away from both the main surface and the side surface of the plate-like portion. This arrangement of the connecting portion makes it particularly difficult for heat released from the busbar to be transferred to the connecting portion, and the possibility of heat transferred to the leg portion via the connecting portion softening the base portion can be particularly reduced. In addition, since the length of the connecting portion is larger than when the connecting portion is provided along the normal direction (first direction) of the busbar, the area of ​​the connecting portion that performs the heat dissipation action is increased, and the heat dissipation efficiency is improved.

[0015] The current sensor may have a plurality of mounting fixtures, and the plurality of mounting fixtures may include a first mounting fixture and a second mounting fixture that are aligned in the third direction when viewed in the second direction. By having two mounting fixtures that are aligned in the third direction when viewed in the second direction, the busbar can be held stably.

[0016] The holding portion of the first mounting bracket may hold one side of the plate-shaped portion in the third direction, and the holding portion of the second mounting bracket may hold the other side of the plate-shaped portion in the third direction. The holding portions of the first and second mounting brackets may hold both sides of the plate-shaped portion in the third direction at the same position in the second direction. By holding one side and the other side of the plate-shaped portion in the third direction, tilting of the busbar becomes less likely to occur compared to holding the central portion, and the amount of heat transmitted to the mounting bracket is reduced.

[0017] The first mounting fixture may have a bridging portion that connects the connecting portion of the first mounting fixture and the connecting portion of the second mounting fixture. Both the connecting portion of the first mounting fixture and the connecting portion of the second mounting fixture may be connected to the bridging portion at multiple points. The presence of the bridging portion provides greater stability in holding the busbar. Specifically, a truss structure is formed by the bridging portion and the mounting fixture, which suppresses vibration and deformation of the mounting fixture due to vibration and shock. Therefore, variations in measurement accuracy due to misalignment of the relative positions of the magnetic sensor and the busbar can be further reduced, thereby improving the measurement accuracy of the current sensor.

[0018] The bridging portion may have a support portion that contacts the busbar. In addition to the holding portion of the mounting fixture, supporting the busbar by contact with the support portion of the bridging portion improves the effect of suppressing busbar displacement, and a current sensor that is more resistant to vibration can be provided.

[0019] The bridging portion may be made of a plate material, and the support portion may be the end of the plate material on the busbar side in the first direction. By bringing the end of the bridging portion made of the plate material into contact with the busbar, the contact area can be reduced compared to when the main surface of the support portion made of the plate material is in contact with the busbar. In addition, because the support portion extends along the first direction, the case is less likely to receive heat from the busbar. Therefore, the transfer of heat from the busbar to the case can be suppressed.

[0020] Viewed in the second direction, the base portion may be distal to the busbar than the magnetic sensor. By providing the base portion in a part of the case that is farther from the busbar, the length of the mounting bracket increases. As a result, the surface area of ​​the mounting bracket increases, and the heat dissipation efficiency of the busbar via the mounting bracket improves. Therefore, the heat generated by the busbar is suppressed from being transmitted to the case via the base portion, and softening of the case can be effectively prevented.

[0021] If the current sensor has a magnetic shield, and the direction in which the busbar and the magnetic sensor face each other is defined as the first direction, and the direction of current flow in the portion of the busbar facing the magnetic sensor is defined as the second direction, then the busbar, the magnetic sensor, and the magnetic shield may be arranged in this order in the first direction when viewed in the second direction. By providing a magnetic shield, external magnetic noise can be suppressed, thereby improving the measurement accuracy of the current sensor.

[0022] The aforementioned mounting fixture may be made of stainless steel. Because stainless steel has high heat resistance and low thermal conductivity, it can firmly hold the busbar when it becomes very hot, and can also suppress the transfer of heat from the busbar to the case.

[0023] The current sensor may have multiple mounting fixtures, and these multiple mounting fixtures may include a first mounting fixture and a third mounting fixture that are aligned in the second direction when viewed in the third direction. Having two mounting fixtures that are aligned in the second direction when viewed in the third direction, that is, that are at different positions in the second direction, makes it easier to stabilize the holding of the busbar.

[0024] The plurality of mounting fixtures may include a second mounting fixture that overlaps with the first mounting fixture in the second direction when viewed in the third direction. With the above configuration, the mounting fixture can hold the busbar at three points, making it possible to hold the busbar more stably.

[0025] The plurality of mounting fixtures may include a fourth mounting fixture that, when viewed in the third direction, overlaps with the third mounting fixture in the second direction. With the above configuration, the mounting fixtures can hold the busbar at four points, making it possible to hold the busbar particularly stably.

[0026] The first and second mounting brackets may form a pair, and the third and fourth mounting brackets may also form a pair. By providing pairs of mounting brackets at positions where they overlap in the second direction, the busbar can be held stably and in a balanced manner.

[0027] The current sensor may have a bridging portion connecting the connecting portion of the first mounting fixture and the connecting portion of the second mounting fixture, and a bridging portion connecting the connecting portion of the third mounting fixture and the connecting portion of the fourth mounting fixture. Having a bridging portion provides more stable retention of the busbar.

[0028] The current sensor of the present invention separates the busbar through which the current to be measured flows from the case that holds the magnetic sensor, and holds the busbar at a position away from the case by a mounting device that connects the busbar and the case. Therefore, the effect of heat generated from the busbar when a large current flows on the case is suppressed, and a current sensor with good measurement accuracy can be provided with small errors due to misalignment between the busbar and the magnetic detection unit.

[0029] This is a schematic perspective view showing the main parts of a current sensor according to an embodiment of the present invention. This is a schematic plan view showing the main parts of the current sensor in Figure 1. This is a schematic front view showing the main parts of the current sensor in Figure 1. This is a schematic side view showing the main parts of the current sensor in Figure 1. This figure shows the simulation results of how heat spreads from the plate-shaped part of the busbar. This is a schematic perspective view showing the mounting fixture in the current sensor in Figure 1. This is a schematic front view showing the mounting fixture in the current sensor in Figure 1. This is a schematic perspective view showing the main parts of a modified example of the current sensor according to an embodiment of the present invention. This is a schematic perspective view showing the mounting fixture in the current sensor in Figure 8. This is a schematic front view showing the mounting fixture in the current sensor in Figure 8.

[0030] Embodiments of the present invention will be described below with reference to the accompanying drawings. The same number is assigned to the same component in each drawing, and the description will be omitted as appropriate. Reference coordinates will be shown in each drawing as appropriate to indicate the positional relationship of each component. In the reference coordinates, the direction of the extension of the busbar, i.e., the direction of the current to be measured in the portion of the busbar facing the magnetic sensor, is defined as the X direction (second direction), and the direction of the width dimension of the busbar perpendicular to the X direction is defined as the Y direction (third direction). The direction perpendicular to the X and Y directions, in which the busbar and the magnetic detection unit face each other, is defined as the Z direction (first direction).

[0031] Figure 1 is a schematic perspective view showing the main parts of a current sensor 1 according to an embodiment of the present invention. Figures 2, 3, and 4 are a plan view, a front view, and a side view, respectively, showing the main parts of the current sensor 1 shown in Figure 1.

[0032] The current sensor 1 comprises a busbar 2, a magnetic sensor 3, and a case 4. It has a mounting fixture 5 that connects the busbar 2 and the case 4, and holds the busbar 2 at a position away from the case 4 (outside the case 4). An example of the current sensor 1 is a magnetic balance type current sensor 1 that measures the feedback current when the magnetic flux generated by the current under test and the magnetic flux generated by the feedback current cancel each other out, by passing a feedback current that cancels out the magnetic flux generated by the current under test.

[0033] The busbar 2 is held on the outside of the case 4 via a mounting bracket (stay) 5 and positioned away from the case 4. This prevents the heat generated in the busbar 2 when the measured current flows from being directly transferred to the case 4. In other words, when a high voltage flows, the heat generated from the busbar 2 is transferred to the case 4 via the mounting bracket 5 and the air, and the heat is cooled before it reaches the case 4. Thus, softening of the case 4 due to the heat generated by the busbar 2 is prevented, and the positional relationship between the busbar 2 and the magnetic sensor 3 can be maintained. Consequently, the current sensor 1 can suppress errors due to misalignment between the busbar 2 and the magnetic sensor 3, resulting in improved measurement accuracy.

[0034] The busbar 2 is a conductor through which the current to be measured flows, made of copper, brass, aluminum, or the like, and extends in the X direction (second direction). The busbar 2 is not limited to a plate-like body in which the entire body is a plate-like portion 22, but may have a plate-like portion 22 in part, with the normal L of the main surface 21 aligning with the Z direction (first direction). For example, the constricted portion facing the magnetic sensor 3 may be a plate-like portion 22, and the other parts may be cylindrical in shape, etc.

[0035] In Figures 1 and 2, an example is shown in which both ends of the busbar 2 in the X direction (second direction) are flat plate shapes with through holes. However, both ends or one end in the X direction may be made of a shape other than a flat plate shape. For example, considering joining with external members, a bent portion or a notched portion may be provided at the end of the busbar 2 in the X direction.

[0036] The magnetic sensor 3 is provided on the substrate 6 so as to face the main surface 21 of the plate-shaped portion 22 of the busbar 2, and detects the magnetism generated by the current being measured flowing through the busbar 2. The magnetic sensor 3 can be, for example, a Hall element, a giant magnetoresistance element (GMR element), a tunnel magnetoresistance element (TMR element), or other magnetoresistive elements. The configuration shown in Figure 1 is an example where a GMR element is used as the magnetic sensor 3, but when using other magnetic detection elements, the orientation of the detection surface and other aspects should be appropriately changed during placement. The magnetic sensor 3 may also be a differential type that outputs the difference between the first output and the second output.

[0037] The case 4 holds the magnetic sensor 3 in a predetermined position by holding the substrate 6 on which the magnetic sensor 3 is provided, and also holds the busbar 2 in a predetermined position via the mounting fixture 5, and is made of thermoplastic resin. In this embodiment, the mounting fixture 5 is partially held in the case 4 by insert molding, thereby holding the busbar 2 to the case 4. By holding the busbar 2 to the case 4 via the mounting fixture 5, the heat generated in the busbar 2 is transmitted to the case 4 via the mounting fixture 5, but the heat is cooled before it reaches the case 4. Therefore, the influence of heat from the busbar 2 on the case 4 can be reduced, and the softening of the thermoplastic resin of the case 4 due to the heat generated by the busbar 2 can be suppressed. Thus, it is possible to prevent the mounting fixture 5 from tilting due to the softening of the case 4 and causing the busbar 2 to shift from its predetermined position, and a deterioration in measurement accuracy can be prevented.

[0038] Case 4 does not need to be entirely made of thermoplastic resin; it is sufficient to have a portion made of thermoplastic resin. Examples of thermoplastic resins include polyphenylene sulfide (PPS) and butylene terephthalate (PBT). A thin metal sheet, such as copper, may be attached to the surface of Case 4. The thin metal sheet shields the heat from the busbar 2, thereby improving the effect of suppressing the softening of the thermoplastic resin.

[0039] Case 4 has a base portion 41, on which the mounting fixture 5 is supported. The method of fixing the mounting fixture 5 to the base portion 41 is not particularly limited, but examples include insert molding, fitting, bonding, welding, etc.

[0040] Viewed in the X direction, the base portion 41 is located further from the busbar 2 than the magnetic sensor 3. By providing the base portion 41 in a part of the case 4 that is far from the busbar 2, the length of the mounting fixture 5 increases. As a result, the surface area of ​​the mounting fixture 5 increases, and the efficiency of dissipating the heat generated by the busbar 2 via the mounting fixture 5 is improved. Therefore, the heat generated by the busbar 2 is suppressed from being transmitted to the case 4 via the base portion 41, and softening of the case 4 (base portion 41) can be effectively prevented. Note that the base portion 41 is not limited to the position shown in the figure, and may be provided in a location closer to the busbar 2, such as the top surface of the case 4.

[0041] When the magnetic sensor 3 is provided on the busbar 2 side of case 4, it is preferable to have a configuration where there is space between the busbar 2 and the magnetic sensor 3, as shown in Figures 1 and 3, and the magnetic sensor 3 is exposed. By creating a space between the busbar 2 and the magnetic sensor 3, heat from the busbar 2 can dissipate more easily, and the effect of heat generated by the busbar 2 on the magnetic sensor 3 is suppressed compared to when the magnetic sensor 3 is sealed with resin. Note that the magnetic sensor 3 may be provided not on the busbar 2 side (Z2 side) of the substrate 6, but on the opposite side of the busbar 2 (Z1 side) of the substrate 6 or on the Z1 side of case 4.

[0042] As shown in Figures 3 and 4, the base portion 41 is provided near the center 4C of the case 4 in the Z direction (first direction, vertical direction in Figure 3). However, assuming that the relative position of the busbar 2 and the magnetic sensor 3 is not changed, the position of the base portion 41 in the case 4 is not limited to this, and the base portion 41 may be positioned on the Z1 side (lower side in Figure 3) of the center 4C. By providing it on the Z1 side, the length of the mounting fixture 5 in the Z direction becomes longer, so the effect of heat generation from the busbar 2 on the base portion 41, which is made of thermoplastic resin, is further suppressed. Therefore, the risk of the relative position of the busbar 2 and the magnetic sensor 3 of the case 4 shifting due to softening of the base portion 41 can be reduced. Note that the base portion 41 may also be provided at a position other than near the center 4C or on the Z1 side of the center 4C, for example, on the Z2 side surface (upper side in Figure 3) of the case 4.

[0043] In this case, since the length of the fixture 5 in the Z direction becomes shorter, it is preferable to set the distance such that no relative displacement occurs between the bus bar 2 and the magnetic sensor 3 of the case 4 due to the softening of the base portion 41. In a state where periodic vibration is applied, the variation in the relative position between the bus bar 2 and the magnetic sensor 3 due to vibration can be suppressed as compared with the case where the length of the fixture 5 in the Z direction is long.

[0044] The current sensor 1 has a magnetic shield 7 on the Z1 side of the substrate 6. In the current sensor 1 shown in FIGS. 3 and 4, it has a flat magnetic shield 7. When viewed in the X direction (second direction), the bus bar 2, the magnetic sensor 3, and the magnetic shield 7 are arranged in this order in the Z direction (first direction) from Z2 to Z1. In the current sensor 1 shown in FIGS. 3 and 4, the magnetic shield 7 is held inside the case 4 by insert molding, but it may be held on the lower surface (the surface on the Z1 side) of the case 4.

[0045] The magnetic shield 7 can be formed, for example, by stacking a plurality of plate-like metals of the same shape. By suppressing external magnetic noise to the magnetic sensor 3 by the magnetic shield 7, the measurement accuracy of the current sensor 1 is improved. When the magnetic shield 7 is arranged on the bus bar 2 side, for example, it can be attached to the end on the Z2 side of the fixture 5.

[0046] In FIGS. 3 and 4, the magnetic shield 7 is shown only on the opposite side (Z1 side) of the bus bar 2 with respect to the magnetic sensor 3, but it may be a pair of flat magnetic shields 7 arranged on the opposite side and the bus bar 2 side (Z2 side) of the bus bar 2. Also, the magnetic shield 7 may have a U-shaped configuration when viewed along the X direction.

[0047] When using a U-shaped magnetic shield, it is preferable that the magnetic sensor 3 is arranged in a region between a pair of flat portions B (not shown) arranged to face each other in the Y direction extending in the Z2 direction from both ends in the Y direction of the flat portion A (not shown) of the magnetic shield arranged on the Z1 side of the magnetic sensor 3.

[0048] FIG. 5 is a diagram showing the simulation result of how heat spreads from the plate-like portion 22 of the bus bar 2, and shows the influence of the heat generated when the measured current flows through the plate-like portion 22 on the surroundings. Note that this figure shows the simulation result when the influence of the gravitational direction is ignored from the viewpoint of facilitating the comparison between the Z direction and the Y direction.

[0049] The influence of the heat generation of the bus bar 2 spreads so as to approach a perfect circle from an ellipse as the distance D from the plate-like portion 22 increases. For this reason, the rate at which the influence of heat decreases as the distance D from the plate-like portion 22 increases is greater in the direction horizontal to the main surface 21 (Y direction) than in the direction perpendicular to the main surface 21 of the plate-like portion 22 (Z direction) when viewed in the X direction. That is, if the distance D from the plate-like portion 22 of the bus bar 2 is the same, the influence of the heat generation of the bus bar 2 is smaller in the direction horizontal to the main surface 21. For this reason, if the distance D from the surface of the plate-like portion 22 is the same, the influence of the heat generation from the plate-like portion 22 can be made smaller by moving away in the Y direction than by moving away in the Z direction.

[0050] Therefore, from the viewpoint of suppressing the influence of heat generation from the plate-like portion 22, it is preferable to extend the fixture 5 in a direction including a component in the Y direction rather than extending it in the Z direction. With this configuration, the influence of the heat generation of the bus bar 2 on the magnetic sensor 3, the case 4, and the substrate 6 can be suppressed. The current sensor 1 has found that the influence of the heat generation from the plate-like portion 22 varies depending on the direction with respect to the main surface 21 of the plate-like portion 22, and has devised the direction in which the fixture 5 is provided, that is, the extraction direction, to suppress the influence of the heat generation from the plate-like portion 22. Further, compared with the case where the fixture 5 is provided along the Z direction with the above configuration, there is no need to take a distance considering the influence of heat, so the length of the fixture 5 can be shortened to a size that gives priority to magnetic design over the influence of heat. Therefore, the current sensor 1 can be made low-profile and the amount of material used can be reduced.

[0051] FIG. 6 and FIG. 7 are a perspective view and a front view schematically showing the fixture 5 in the current sensor 1 of FIG. 1. As shown in these figures, the fixture 5 includes a holding portion 51, a leg portion 52, and a connecting portion 53.

[0052] As shown in Figures 1 to 4, the holding portion 51 holds the busbar 2 on the Z2 side (one end) in the Z direction of the mounting fixture 5. The current sensor 1 is provided with notches 23 on both sides in the width direction of the busbar 2, corresponding to the holding portion 51, and the busbar 2 is held by the mounting fixture 5 with the notches 23 and the holding portion 51 engaged.

[0053] The leg portion 52 is supported on the base portion 41 of the case 4 at the Z1 side (other end side) in the Z direction of the mounting fixture 5. For example, the mounting fixture 5 is supported on the base portion 41 of the case 4 by insert molding the leg portion 52 into the base portion 41 of the current sensor 1.

[0054] The connecting portion 53 is a part that extends to connect the leg portion 52 and the holding portion 51. As shown in Figure 7, the extension direction of the connecting portion 53 has a component in the Y direction (third direction) and a component in the Z direction (first direction). Here, the extension direction refers to the direction of the straight line E shown by a dashed line in the figure, which connects the midpoints in the Y direction in the portion of the connecting portion 53 where the width in the Y direction is equal. When the extension direction has a component in the Y direction, the straight line E intersects the XZ plane, and when the extension direction has a component in the Z direction, the straight line E intersects the XY plane.

[0055] As shown in the simulation results in Figure 5, the direction in which heat from the busbar 2 is most easily transferred is the Z direction, where the busbar 2 and the magnetic sensor 3 face each other. When the busbar 2 is a plate-like body and faces the magnetic sensor 3 in the direction normal to the main surface 21 of the busbar 2 (Z direction), heat from the busbar 2 is relatively less easily transferred in directions tilted with respect to the Z direction.

[0056] Since the busbar 2 extends in the X direction (second direction), which is perpendicular to the Z direction, the connecting portion 53 is extended to have a component in the Y direction (third direction), which is the width direction of the busbar 2. This makes it difficult for the heat generated by the busbar 2 to be transferred to the case 4 via the base portion 41 to which the legs 52 of the mounting fixture 5 are attached, thereby suppressing the softening of the case 4 due to the heat generated by the busbar 2.

[0057] Since the connecting portion 53 has components in the Z and Y directions in its extending direction, it extends away from both the main surface 21 and the side surface 24 of the plate-like portion 22 of the busbar 2 (see Figure 1). With this configuration, heat released from the busbar 2 is less likely to be transferred to the connecting portion 53, and the risk of heat transferred to the leg portion 52 via the connecting portion 53 softening the base portion 41 can be reduced. In addition, the heat dissipation effect of the connecting portion 53 is improved because the length and area of ​​the connecting portion 53 are larger than when the connecting portion 53 is extended along the direction of the normal L of the main surface 21 of the busbar 2 (Z direction).

[0058] The material used to form the mounting bracket 5 is not particularly limited, but stainless steel can be used, for example. Because stainless steel has high heat resistance and low thermal conductivity, it can firmly hold the busbar 2 when high heat is generated in the busbar 2, and can also suppress the transfer of heat from the busbar 2 to the case 4. Furthermore, if the mounting bracket 5 is formed from magnetic stainless steel, the mounting bracket 5 can function as a magnetic shield 7 to suppress magnetic noise. Examples of magnetic stainless steel include austenitic stainless steel.

[0059] As shown in Figures 6 and 7, the connecting portion 53 has a configuration in which a hollow portion 53B is formed along the extending direction when viewed in the X direction. This configuration reduces the cross-sectional area of ​​the connecting portion 53 in the XY plane, thereby suppressing heat conduction through the connecting portion 53, and thus reducing the thermal influence from the busbar 2 on the case 4.

[0060] As shown in Figures 1 and 2, the current sensor 1 is equipped with multiple mounting fixtures 5 as described above. Hereinafter, when multiple mounting fixtures 5 are to be distinguished as such, they will be referred to as mounting fixtures 5a to 5d with subscripts a to d, and when they are not to be distinguished as such, they will be referred to as mounting fixture 5. Similarly, the holding part 51, leg part 52, and connecting part 53 will be referred to as holding part 51a to 51d, leg part 52a to 52d, and connecting part 53a to 53d, respectively, with subscripts a to d as such.

[0061] As shown in Figures 2 and 3, the current sensor 1 has mounting fixtures (first mounting fixture) 5a and (second mounting fixture) 5b on the X2 side, and mounting fixtures (third mounting fixture) 5c and (fourth mounting fixture) 5d on the X1 side, which are aligned in the Y direction (third direction) when viewed in the X direction (second direction). Mounting fixtures 5a and 5c located on the Y1 side are aligned in the X direction (second direction) when viewed in the Y direction (third direction), and mounting fixtures 5b and 5d located on the Y2 side are aligned in the X direction when viewed in the Y direction.

[0062] By having multiple mounting fixtures 5 that are aligned in the Y direction when viewed in the X direction, that is, that are positioned differently in the Y direction, the busbar 2 is more easily held stably. "Aligned in the Y direction when viewed in the X direction" includes both mounting fixtures 5 that are positioned the same in the Y direction and mounting fixtures 5 that are positioned differently in the Y direction. For example, among mounting fixtures 5a to 5d, mounting fixtures 5a and 5b, mounting fixtures 5c and 5d, mounting fixtures 5a and 5d, and mounting fixtures 5b and 5c are all mounting fixtures 5 that are aligned in the Y direction when viewed in the X direction.

[0063] In this case, when viewed in the Y direction, the busbar 2 can be held more stably by providing one of the mounting fixtures 5 aligned in the Y direction and another mounting fixture 5 aligned in the X direction, i.e., at a different position in the X direction. With a configuration that includes mounting fixtures 5 aligned in the X direction in addition to mounting fixtures 5 aligned in the Y direction, the busbar 2 will be held by at least three mounting fixtures 5, thus allowing the busbar 2 to be held stably. "Aligned in the X direction when viewed in the Y direction" includes both mounting fixtures 5 at the same position in the Y direction and mounting fixtures 5 at different positions in the Y direction.

[0064] The holding portion 51a of the mounting bracket 5a holds the Y1 side (one side) of the busbar 2 in the Y direction, which is the width direction, and the holding portion 51b of the mounting bracket 5b holds the Y2 side (the other side) of the plate-shaped portion 22 in the Y direction. The holding portion 51a of the mounting bracket 5a and the holding portion 51b of the mounting bracket 5b hold both sides of the plate-shaped portion 22 in the Y direction (third direction) at the same position in the X direction (second direction).

[0065] Similarly, the holding portion 51c of the mounting fixture 5c holds the Y1 side of the plate-shaped portion 22 in the Y direction, which is the width direction, and the holding portion 51d of the mounting fixture 5d holds the Y2 side of the plate-shaped portion 22 in the Y direction. The holding portion 51c of the mounting fixture 5c and the holding portion 51d of the mounting fixture 5d hold both sides in the Y direction at the same position in the X direction of the plate-shaped portion 22.

[0066] By attaching the busbar 2 to the case 4 with the four mounting fixtures 5, the busbar 2 can be held more stably. In addition, by holding both sides (one side and the other side) of the plate-shaped portion 22 in the Y direction, tilting of the busbar 2 is less likely to occur compared to holding the central part of the busbar 2, and the amount of heat transferred from the busbar 2 to the mounting fixtures 5 can be reduced.

[0067] As shown in Figures 2 and 4, the current sensor 1 has mounting fixtures 5a and 5c that are aligned in the X direction when viewed in the Y direction. It also has mounting fixture 5b that overlaps with mounting fixture 5a in the X direction when viewed in the Y direction, and mounting fixture 5d that overlaps with mounting fixture 5c in the X direction. With this configuration, the mounting fixtures 5 can hold the busbar 2 at four points, making it possible to hold the busbar 2 particularly stably.

[0068] Furthermore, in this embodiment, the current sensor 1 has mounting brackets 5a and 5b in pairs, and mounting brackets 5c and 5d in pairs. By providing pairs of mounting brackets 5 at positions that overlap in the X direction when viewed in the Y direction, the busbar 2 can be held in a balanced manner relative to the case 4.

[0069] In this embodiment, the term "a pair" of mounting fixtures 5 means that, as shown in Figure 3, the holding portion 51, leg portion 52, and connecting portion 53 of the two mounting fixtures 5 aligned in the Y direction are provided symmetrically with respect to a center line C extending in the Z direction.

[0070] As shown in Figures 2 and 3, the mounting bracket 5 has its legs 52 located further from the busbar 2 than the holding portion 51 in the Z direction. The connecting portions 53 (connecting portions 53a and 53b, connecting portions 53c and 53d) of the pair of mounting brackets 5 (mounting brackets 5a and 5b, mounting brackets 5c and 5d) extend in a direction in which the distance between them in the Y direction increases as you move from the busbar 2 side (Z2 side) towards the base portion 41 side (Z1 side). This configuration improves the heat dissipation efficiency from the connecting portions 53.

[0071] By fixing the busbar 2 to the holding portion 51 of the mounting fixture 5 having the above configuration, and attaching the leg portion 52 to the base portion 41, the busbar 2 can be fixed to the case 4 so that the busbar 2 and the magnetic sensor 3 are in a predetermined positional relationship.

[0072] The current sensor 1 has a bridging portion 54 that connects the connecting portion 53a of the mounting fixture 5a and the connecting portion 53b of the mounting fixture 5b. Similarly, a bridging portion 54 is also provided between the connecting portion 53c of the mounting fixture 5c and the connecting portion 53d of the mounting fixture 5d. By having a bridging portion 54 that connects the connecting portions 53 of a pair of mounting fixtures 5, the holding of the busbar 2 by multiple mounting fixtures 5 becomes more stable.

[0073] Since a truss structure is formed by the bridging portion 54 and the mounting fixture 5, vibration and deformation of the mounting fixture 5 due to vibration and shock can be suppressed. This further reduces the variation in measurement accuracy due to the relative positional misalignment between the magnetic sensor 3 and the busbar 2, resulting in a current sensor 1 with good measurement accuracy.

[0074] Furthermore, by forming a truss structure with the busbar 2 as the apex between the bridging portion 54 and the mounting bracket 5, it is possible to reduce the heat receiving area from the busbar 2 while increasing the area on the cooling side, the lower side (Z1 side). As a result, the bridging portion 54 and the mounting bracket 5 can suppress the influence of heat generated by the busbar 2 and dissipate heat efficiently, thereby reducing the impact of heat generated by the busbar 2 on the case 4 via the mounting bracket 5.

[0075] The connecting portion 53a of the mounting bracket 5a and the connecting portion 53b of the mounting bracket 5b are both connected to the bridging portion 54ab at two points. Similarly, the connecting portion 53c of the mounting bracket 5c and the connecting portion 53d of the mounting bracket 5d are both connected to the bridging portion 54cd at two points (see Figures 1 and 3). Because the mounting bracket 5 is connected to the bridging portion 54 at multiple points, the busbar 2 can be firmly fixed to the case 4 by the mounting bracket 5. As a result, the risk of the positional relationship between the busbar 2 and the magnetic sensor 3 shifting due to vibration is reduced, resulting in a highly reliable current sensor 1.

[0076] The bridging portion 54 has a support portion 541 that contacts the busbar 2. By supporting the busbar 2 through contact with the support portion 541 of the bridging portion 54, in addition to the holding portion 51 of the mounting fixture 5, the effect of suppressing displacement of the busbar 2 is improved, thereby providing a current sensor 1 that is more resistant to vibrations and the like.

[0077] As shown in Figure 6, the bridging portion 54 is made of a plate material, and the support portion 541 consists of the end portion 542 of the plate material on the busbar 2 side (Z2 side) in the Z direction (first direction). By bringing the end portion 542 of the bridging portion 54, which is made of a plate material, into contact with the busbar 2 (see Figure 3), the contact area can be reduced compared to when the main surface of the support portion 541, which is made of a plate material, is in contact with the busbar 2. In addition, because the support portion 541 extends along the Z direction, it is less likely to receive heat from the busbar 2. Therefore, the transfer of heat from the busbar 2 to the case 4 can be suppressed.

[0078] [Modified Examples] Figure 8 is a schematic perspective view showing the main parts of a modified example of the current sensor 1 according to an embodiment of the present invention. Figure 9 is a schematic perspective view showing the mounting bracket 5 in the current sensor 1 of Figure 8. Figure 10 is a schematic front view showing the mounting bracket 5 in the current sensor 1 of Figure 8.

[0079] The current sensor 1 shown in Figures 8 to 10 differs from the current sensor 1 shown in Figure 1 in the configuration of the mounting bracket 5 and the bridging portion 54. The holding portion 51 of the mounting bracket 5 holds the busbar 2 by clamping it in the Z direction. In addition, the L-shaped legs 52 are insert-molded into the base portion 41 and held in place. With these configurations, the holding portion 51 firmly holds the busbar 2 and the legs 52 are securely fixed to the base portion 41.

[0080] The connecting portion 53, which connects the holding portion 51 and the leg portion 52, is not entirely hollow but partially hollow, and is not visible when viewed in the X direction, but is visible when viewed in the Y and Z directions. The bridging portion 54 is configured to protrude in the X direction from a part of the connecting portion 53.

[0081] As described above, in this embodiment, the current sensor 1 connects the high-temperature busbar 2 and the sensing module including the magnetic sensor 3 with a mounting fixture 5 made of stainless steel or the like, which has high heat resistance and low thermal conductivity. This configuration allows the heat of the busbar 2 to be attenuated while maintaining the positional accuracy of the module including the magnetic sensor 3, making it possible to achieve both high positional accuracy between the magnetic sensor 3 and the busbar 2 and heat resistance of the magnetic sensor 3.

[0082] In the plate-shaped busbar 2, the temperature around the busbar 2 decreases more rapidly with increasing distance in the horizontal direction than in the direction perpendicular to the main surface 21 of the plate-shaped portion 22. Considering this characteristic, a configuration is not adopted in which the mounting bracket 5 extends directly from the busbar 2 perpendicular to the plane of the substrate 6 on which the magnetic sensor 3 is installed, connecting the busbar 2 and the case 4. Instead of this configuration, a configuration in which the connection is made by extending from the horizontal direction diagonally downward allows heat to be attenuated over a shorter distance.

[0083] Furthermore, the above configuration makes it possible to reduce the overall height of the current sensor 1. Economic efficiency can also be improved by reducing the amount of material used for the mounting fixtures 5 used as connecting stays. By connecting the mounting fixtures 5 diagonally and providing a bridging portion 54 that connects the connecting portion 53 of the mounting fixtures 5, a truss structure can be formed, making it possible to realize a current sensor 1 with high strength that has little risk of displacement of the busbar 2 due to vibration.

[0084] Furthermore, taking advantage of the characteristic that the temperature around the busbar 2 decreases more rapidly with increasing distance in the horizontal direction than in the vertical direction relative to the main surface 21 of the plate-shaped portion 22, the connecting portion 53 may be extended from the holding portion 51 in the Y direction first, and then in the Z direction.

[0085] Using the mounting fixture 5a as an example, the connecting portion 53a may be extended from the holding portion 51a in the Y1 direction, and further extended in the Z1 direction to be held by the base portion 41. Since the extension is in the direction that yields the greatest temperature reduction, and the total length of the connecting portion 53a is longer than when it is extended in the direction shown in Figure 3, the heat dissipation effect is further improved. However, the portion of the connecting portion 53a extending in the Y direction is more susceptible to vibration when vibrations are applied in the Y direction, so consideration must be given to vibrations occurring at the location where the current sensor 1 is placed.

[0086] Furthermore, in the current sensor 1 with the configuration shown in Figure 1, the busbar 2 may be held by the holding portion 51 by inserting the holding portion 51 into the notch portion 23 of the busbar 2 and then bending and crimping the tip of the holding portion 51 so that the busbar 2 is sandwiched between the support portion 541 and the holding portion 51. However, the following configuration is also acceptable.

[0087] The tip of the retaining portion 51 may be originally bent as shown in Figure 1, and the connecting portion 53 may be given elasticity that biases in the X direction. Specifically, the mounting fixtures 5a and 5b are given elasticity that biases in the X2 direction, and the mounting fixtures 5c and 5d are given elasticity that biases in the X1 direction. When inserting the retaining portion 51 into the notch portion 23 of the busbar 2, each mounting fixture 5 is inserted while bent in the opposite direction to its respective biasing direction. By releasing the mounting fixture 5 from the bent state, the busbar 2 can be clamped between the tip of the retaining portion 51 and the support portion 541 by the biasing force (see Figure 3).

[0088] The embodiments disclosed herein are illustrative in all respects and are not limited thereto. The scope of the invention is indicated by the claims rather than solely by the above-described embodiments, and all modifications within the meaning and scope equivalent to the claims are intended.

[0089] The present invention is useful, for example, as a current sensor for measuring the current flowing through equipment in order to control a power supply system such as a vehicle equipped with various devices.

[0090] 1 Current sensor 2 Busbar 21 Main surface 22 Plate-shaped part 23 Notch part 24 Side surface 3 Magnetic sensor 4 Case 41 Base part 4C Center in the Z direction 5, 5a-5d Mounting fixture 51, 51a-51d Holding part 52, 52a-52d Leg part 53, 53a-53d Connecting part 53B Hollow part 54, 54ab, 54cd Bridge part 541 Support part 542 End part 6 Substrate 7 Magnetic shield C Center line D Distance L Normal E Straight line

Claims

1. A current sensor comprising a busbar through which a current to be measured flows, a magnetic sensor for detecting the magnetism generated by the current to be measured, and a case for holding the magnetic sensor, wherein the current sensor is equipped with a mounting device that connects the busbar and the case and holds the busbar at a position away from the case.

2. The current sensor according to claim 1, wherein the case has a portion made of thermoplastic resin.

3. The case has a base portion that supports the mounting fixture, and when the direction in which the busbar and the magnetic sensor face each other is designated as a first direction, the direction of current flow in the portion of the busbar facing the magnetic sensor that is perpendicular to the first direction is designated as a second direction, and the direction perpendicular to the first direction and the second direction is designated as a third direction, the mounting fixture comprises: a holding portion that holds the busbar at one end in the first direction; a leg portion that is supported by the base portion at the other end in the first direction; and a connecting portion that extends to connect the leg portion and the holding portion, the direction in which the connecting portion extends has a component of the third direction, and when viewed in the first direction, the leg portion is distal to the busbar than the holding portion, the current sensor according to claim 1.

4. The current sensor according to claim 3, wherein the busbar has a plate-shaped portion whose normal to the main surface is aligned with the first direction, and the holding portion holds the busbar at the plate-shaped portion.

5. The current sensor according to claim 4, wherein the extending direction of the connecting portion has a component of the first direction.

6. The current sensor according to claim 4, comprising a plurality of mounting fixtures, wherein the plurality of mounting fixtures include a first mounting fixture and a second mounting fixture arranged in the third direction when viewed in the second direction.

7. The current sensor according to claim 6, wherein the holding portion of the first mounting fixture holds one side of the plate-shaped portion in the third direction, and the holding portion of the second mounting fixture holds the other side of the plate-shaped portion in the third direction.

8. The current sensor according to claim 7, wherein the holding portions of the first and second mounting fixtures hold both sides of the plate-shaped portion in the third direction at the same position in the second direction.

9. The current sensor according to claim 6, further comprising a bridging portion connecting the connecting portion of the first mounting fixture and the connecting portion of the second mounting fixture.

10. The current sensor according to claim 9, wherein the connecting portion of the first mounting fixture and the connecting portion of the second mounting fixture are both connected to the bridging portion at multiple locations.

11. The current sensor according to claim 9, wherein the bridging portion has a support portion that contacts the busbar.

12. The current sensor according to claim 11, wherein the bridging portion is made of a plate material, and the support portion is the end of the plate material on the busbar side in the first direction.

13. The current sensor according to claim 3, wherein, when viewed in the second direction, the base portion is distal to the busbar than the magnetic sensor.

14. A current sensor according to claim 1, having a magnetic shield, wherein when the direction in which the busbar and the magnetic sensor face each other is defined as a first direction, and the direction of current flow in the portion of the busbar facing the magnetic sensor is defined as a second direction perpendicular to the first direction, the busbar, the magnetic sensor, and the magnetic shield are arranged in this order in the first direction when viewed in the second direction.

15. The current sensor according to claim 1, wherein the mounting fixture is made of stainless steel.

16. The current sensor according to claim 3, comprising a plurality of mounting fixtures, wherein the plurality of mounting fixtures include a first mounting fixture and a third mounting fixture that are aligned in the second direction when viewed in the third direction.

17. The current sensor according to claim 16, wherein the plurality of mounting fixtures have a second mounting fixture that overlaps with the first mounting fixture in the second direction when viewed in the third direction.

18. The current sensor according to claim 17, wherein the plurality of mounting fixtures include a fourth mounting fixture that, when viewed in the third direction, overlaps with the third mounting fixture in the second direction.

19. The current sensor according to claim 18, wherein the first mounting bracket and the second mounting bracket form a pair, and the third mounting bracket and the fourth mounting bracket form a pair.

20. The current sensor according to claim 18, further comprising: a bridging portion connecting the connecting portion of the first mounting fixture and the connecting portion of the second mounting fixture; and a bridging portion connecting the connecting portion of the third mounting fixture and the connecting portion of the fourth mounting fixture.

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