Sensor unit

Abstract

To provide a sensor unit that can achieve both suppression of temperature rise of electronic components mounted on a circuit board and miniaturization of the sensor unit. [Solution] The sensor unit 1 comprises a shunt resistor 10 having a pair of busbars 11 and resistors 12 electrically connected to each of the pair of busbars 11, and a circuit board 20 having a conductor pattern connected to each of the pair of busbars 11 and an electronic component 21 that performs calculations using the potential difference between the pair of busbars 11. The circuit board 20 has insulating layers B1 to B5 and conductor layers L1 to L4 having a conductor pattern provided so as to pass through wiring target regions X1 to X4. The wiring target regions X1 to X4 have a first region Z1 that overlaps with the shunt resistor 10, a second region Z2 that overlaps with the electronic component 21, and a third region Z3 that is between the first and second regions Z1 and Z2 and is narrower than the first region Z1.

Description

Technical Field

[0001] The present invention relates to a sensor unit including a shunt resistor and a circuit board.

Background Art

[0002] Conventionally, current measurement devices using shunt resistors have been proposed. For example, in one of the conventional current measurement devices, in order to measure the magnitude of the current flowing through the circuit between a battery mounted on a vehicle or the like and an electrical load, a current measurement device having a shunt resistor and a circuit board connected to the shunt resistor for measuring the current is used (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the above-described type of current measurement device, generally, the Joule heat generated in the circuit (especially the bus bar) during energization is transmitted to the circuit board, so that the temperatures of various electronic components mounted on the circuit board increase. From the viewpoint of properly operating the electronic components, it is not preferable that the temperature of the electronic components increases excessively. On the other hand, if the circuit board is enlarged to move the electronic components far from the heat source such as the bus bar, the current measurement device itself will be enlarged. Thus, in a current measurement device using a shunt resistor, it is usually difficult to achieve both suppression of the temperature rise of the electronic components mounted on the circuit board and miniaturization of the current measurement device.

[0005] One object of the present invention is to provide a sensor unit capable of achieving both suppression of the temperature rise of the electronic components mounted on the circuit board and miniaturization of the sensor unit.

Means for Solving the Problems

[0006] To achieve the aforementioned objectives, the sensor unit according to the present invention has the following features.

[0007] A shunt resistor having a pair of conductors and a resistor sandwiched between the pair of conductors and electrically connected to each of the pair of conductors, A circuit board having a conductor pattern electrically connected to each of the pair of conductors, and an electronic component that performs calculations using the potential difference between the pair of conductors based on an input obtained through the conductor pattern, A sensor unit comprising, The aforementioned circuit board is The insulating layer has a wiring surface for providing the aforementioned conductor pattern, and the conductor layer is composed of the aforementioned conductor pattern arranged to pass through the wiring target region of the wiring surface, The aforementioned wiring target area is, The connection point between the shunt resistor and the circuit board has a first region in which the wiring target area overlaps in the thickness direction of the circuit board; the connection point between the shunt resistor and the circuit board has a second region in which the wiring target area overlaps in the thickness direction of the electronic component; and a third region between the first region and the second region, which is narrower than at least the first region of the first and second regions. It must be a sensor unit. [Effects of the Invention]

[0008] According to the sensor unit of the present invention, the conductor layer of the circuit board is composed of a conductor pattern arranged to pass through a specific wiring target region. Here, the wiring target region is composed of a first region in which the wiring target region overlaps in the thickness direction of the circuit board with the connection point between the shunt resistor and the circuit board, a second region in which the wiring target region overlaps in the thickness direction with the electronic component, and a third region located between the first and second regions and narrower than at least the first region of the first and second regions. Conductor patterns are generally formed of metal (e.g., copper), and therefore have a higher thermal conductivity than insulating layers formed of resin or the like. In other words, the shape of the wiring target region where the conductor pattern is arranged affects heat transfer from the shunt resistor to the electronic component via the circuit board. The sensor unit with this configuration has a third region that is narrower than the first region between the first and second regions of the wiring target region, so heat transfer to the electronic component can be suppressed compared to when there is no third region. Furthermore, as another effect, since it is not necessary to excessively separate the conductor and the electronic component, the influence of external noise on the conductor pattern can also be reduced. The wiring target area refers to, for example, an area where a predetermined conductor pattern can be provided during the design of a circuit board, or an area where wiring is possible, estimated from the wiring density and shape of numerous conductor patterns actually provided on the circuit board (for example, if the wiring density is defined as the ratio of the area occupied by conductor patterns to a unit area of ​​the wiring surface, then an area where the wiring density is greater than or equal to a predetermined value). Therefore, this sensor unit configuration makes it possible to suppress the temperature rise of electronic components mounted on the circuit board and to miniaturize the sensor unit.

[0009] The present invention has been briefly described above. Further details of the present invention will be clarified by referring to the accompanying drawings and reading through the embodiments for carrying out the invention described below. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a perspective view showing a sensor unit according to an embodiment of the present invention and a pair of external busbars assembled to the sensor unit. [Figure 2] Figure 2 is a perspective view showing the shunt resistor and circuit board that constitute the sensor unit shown in Figure 1. [Figure 3] Figure 3 is a cross-sectional view showing a portion of the AA section in Figure 2. [Figure 4] Figures 4(a) to 4(d) are top views showing the wiring regions of each of the multiple conductor layers included in the circuit board shown in Figure 2. [Figure 5] Figures 5(a) to 5(d) are top views showing the wiring target areas of each of the multiple conductor layers included in the circuit board of the sensor unit according to the first modified example. [Figure 6] Figures 6(a) to 6(d) are top views showing the wiring target areas of each of the multiple conductive layers included in the circuit board of the sensor unit according to the second modified example. [Figure 7] Figures 7(a) to 7(d) are top views showing the wiring target areas of each of the multiple conductive layers included in the circuit board of the sensor unit according to the third modified example. [Figure 8] Figure 8 is a perspective view showing a sensor unit according to the fourth modified example. [Figure 9] Figures 9(a) to 9(d) are top views showing the wiring regions of each of the multiple conductive layers included in the circuit board of the sensor unit according to the fourth modified example shown in Figure 8. [Figure 10] Figure 10 is a perspective view showing a sensor unit according to the fifth modified example. [Figure 11] Figures 11(a) to 11(d) are top views showing the wiring target areas of each of the multiple conductive layers included in the circuit board of the sensor unit according to the fifth modified example shown in Figure 10. [Modes for carrying out the invention]

[0011] <Embodiment> Hereinafter, the sensor unit 1 according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 2, the sensor unit 1 according to an embodiment of the present invention includes a shunt resistor 10 and a circuit board 20 arranged to overlap the shunt resistor 10. The sensor unit 1 is mounted, for example, on an electric vehicle, a hybrid vehicle, etc., and measures the magnitude of the current flowing through the circuit between the drive battery mounted on the vehicle and an electrical load such as a motor (that is, the current charged and discharged from the battery). It is used as a current measuring device using the shunt resistor 10.

[0012] Hereinafter, for convenience of explanation, as shown in FIG. 1 etc., "front", "rear", "left", "right", "up", and "down" are defined. The "front-rear direction", "left-right direction", and "up-down direction" are orthogonal to each other. The front-rear direction, left-right direction, and up-down direction do not necessarily have to coincide with the front-rear direction, left-right direction, and up-down direction of the vehicle on which the sensor unit 1 is mounted. Hereinafter, each component constituting the sensor unit 1 will be described in order.

[0013] First, the shunt resistor 10 will be described. As shown in FIG. 2, the shunt resistor 10 is composed of a pair of left and right bus bars 11 and a resistor body 12 inserted between the pair of left and right bus bars 11 and electrically connected to each of the pair of bus bars 11. In this example, each bus bar 11 is composed of a substantially rectangular flat plate made of metal (for example, made of copper (Cu)) extending in a strip shape in the left-right direction. Therefore, the entire shunt resistor 10 also has a substantially rectangular flat plate shape extending in a strip shape in the left-right direction. The resistor body 12 is composed of, for example, an alloy of copper (Cu) and manganese (Mn) (Cu-Mn alloy), or an alloy of nickel (Ni) and chromium (Cr) (Ni-Cr alloy). The electrical resistance value per unit volume of the resistor body 12 is larger than the electrical resistance value per unit volume of the bus bar 11.

[0014] To each of the pair of left and right busbars 11, each of the pair of left and right metallic external busbars 30 is connected (see FIG. 1). Specifically, using bolts (not shown) inserted through bolt insertion holes 13 provided at the outer ends in the left-right direction of each busbar 11 and bolt insertion holes 31 provided in the corresponding external busbar 30, each busbar 11 and the corresponding external busbar 30 are fastened and fixed. Of the pair of left and right external busbars 30 respectively connected to the pair of left and right busbars 11, one external busbar 30 is connected to a driving battery mounted on an automobile, and the other external busbar 30 is to be connected to an electrical load such as a motor mounted on the automobile.

[0015] Next, the circuit board 20 will be described. As shown in FIG. 2, the circuit board 20 as a whole has a rectangular flat plate shape that is long in the front-rear direction (hereinafter referred to as the "entire board rectangular shape"). As shown in FIG. 3, the circuit board 20 has a multilayer structure in which five insulating layers B1 to B5 and four conductor layers L1 to L4 are alternately laminated. Specifically, the five insulating layers B1, B2, B3, B4, B5 are laminated in this order from bottom to top, the conductor layer L1 is disposed between the insulating layers B1 and B2, the conductor layer L2 is disposed between the insulating layers B2 and B3, the conductor layer L3 is disposed between the insulating layers B3 and B4, and the conductor layer L4 is disposed between the insulating layers B4 and B5. The insulating layer B1 constitutes the lowermost layer (the layer exposed downward) of the circuit board 20, and the insulating layer B5 constitutes the uppermost layer (the layer exposed upward) of the circuit board 20.

[0016] As shown in FIGS. 1 and 2, the circuit board 20 is directly connected to the shunt resistor 10 such that the vicinity of its rear end region overlaps the shunt resistor 10 (the pair of busbars 11 + the resistor body 12). Thereby, compared with the case of using a separate component (for example, a relay board for heat transfer suppression) for suppressing heat transfer, the entire sensor unit 1 can be miniaturized.

[0017] In this example, the conductor patterns provided on conductor layers L1 and L4 of the conductor layers L1 to L4 that constitute the circuit board 20 function as grounded layers (so-called GND layers). The conductor patterns provided on conductor layer L2 or conductor layer L3 are electrically connected to a pair of busbars 11 via through-holes or via holes by solder. Furthermore, these conductor patterns are electrically connected to the electronic components 21, which will be described later, mounted on the circuit board 20 by solder.

[0018] Electronic components 21 are mounted on the area in front of the center in the front-to-back direction on the upper surface of the circuit board 20 (see Figures 1 and 2). Electronic components 21 have the function of measuring the voltage (V) between the pair of busbars 11 (i.e., between the conductor layers L2 and L3) when the pair of busbars 11 are energized (i.e., when the battery is charged or discharged), and calculating the current (I) flowing through the resistor 12 of the shunt resistor 10 (i.e., the current representing the current used to charge or discharge the battery) using the measured voltage (V), the known resistance value (R) of the resistor 12, and Ohm's law (V = R·I). Since the resistance value (R) of the resistor 12 is extremely small, an amplifier for amplifying the measured voltage (V) and an analog-to-digital converter (ADC) for digitizing the measured voltage (V) may be built into the electronic component 21, or they may be mounted on the circuit board 20 as separate components. Furthermore, the temperature sensor (thermistor) required for temperature correction of the measured voltage (V) may be built into the electronic component 21, or it may be mounted on the circuit board 20 as a separate component.

[0019] As can be seen from Figures 4(a) to 4(d), each of the insulating layers B1 to B4 has the same shape as the "rectangular shape of the entire circuit board" when viewed from the thickness direction (vertical direction) of the circuit board 20. Although not shown, the shape of insulating layer B5 is similar. Conductor layer L1 shown in Figure 3 is formed by a conductor pattern (not shown) that passes through the wiring target area X1 (area indicated by dots in Figure 4(a)) on the wiring surface of insulating layer B1. Similarly, conductor layer L2 shown in Figure 3 is formed by a conductor pattern (not shown) that passes through the wiring target area X2 (area indicated by dots in Figure 4(b)) on the wiring surface of insulating layer B2, conductor layer L3 shown in Figure 3 is formed by a conductor pattern (not shown) that passes through the wiring target area X3 (area indicated by dots in Figure 4(c)) on the wiring surface of insulating layer B3, and conductor layer L4 shown in Figure 3 is formed by a conductor pattern (not shown) that passes through the wiring target area X4 (area indicated by dots in Figure 4(b)) on the wiring surface of insulating layer B4. Although not shown in Figures 4(a) to 4(d), each conductor pattern is typically formed in each of the wiring target areas X1 to X4. The wiring target areas X1 to X4 refer to areas where predetermined conductor patterns can be provided, for example, when designing the circuit board 20, or areas that are considered wireable based on the wiring density and shape of the numerous conductor patterns actually provided on the circuit board 20 (for example, areas where the wiring density is greater than or equal to a predetermined value, if the wiring density is defined as the ratio of the area occupied by conductor patterns to the wiring surface area per unit area).

[0020] The wiring target areas X1 and X4 have a shape equivalent to a "rectangular shape across the entire substrate" when viewed from the thickness direction (vertical direction), as shown by the dotted areas in Figures 4(a) to 4(d). Therefore, the conductor layers L1 and L4 formed by the conductor patterns provided in the wiring target areas X1 and X4 will hereinafter be referred to as the "entire substrate conductor layer" (see Figures 4(a) and 4(d)). The wiring target areas X2 and X3 have a shape in which a portion of the area between the area that overlaps with the shunt resistor 10 in the thickness direction (vertical direction) of the circuit board 20 and the area that overlaps with the electronic component 21 in the thickness direction of the circuit board 20 (hereinafter referred to as the "intermediate region") is excluded from the entire substrate conductor layer. Therefore, the conductor layers L2 and L3 formed by the conductor patterns provided in the wiring target areas X1 and X4 will hereinafter be referred to as the "low heat transfer conductor layer" (see Figures 4(b) and 4(c)).

[0021] Specifically, in each of the wiring target areas X2 and X3, a pair of left and right notches 22 are formed in the intermediate area, recessed inward in the left-right direction. In this way, in the thickness direction of the circuit board 20, the low heat transfer conductor layers L2 and L3 are sandwiched between the full-surface conductor layers L1 and L4. As a result, by shielding against external electromagnetic waves etc. with the full-surface conductor layers L1 and L4, noise in the conductor patterns provided on the low heat transfer conductor layers L2 and L3 can be reduced.

[0022] The conductor patterns constituting the conductor layers L1 to L4 are arranged to pass through each of the wiring target areas X1 to X4. For example, the conductor layers L1 to L4 are composed of either a single conductor pattern or multiple conductor patterns arranged in close proximity. The wiring target areas X2 and X3 on which the conductor patterns constituting the low heat transfer conductor layers are arranged have, as shown in Figures 4(b) and 4(c), a first area Z1 in which the shunt resistor 10 and the wiring target areas X2 and X3 overlap in the thickness direction of the circuit board 20, a second area Z2 in which the electronic component 21 and the wiring target areas X2 and X3 overlap in the thickness direction of the circuit board 20, and a third area Z3 located between the first area Z1 and the second area Z2 and having a narrower width (length in the left-right direction) than the first area Z1 and the second area Z2. On the other hand, the wiring target regions X1 and X4, where the conductor patterns constituting the full-surface conductor layer are arranged, do not have a third region Z3, but rather a first region Z1 and a second region Z2, as shown in Figures 4(a) and 4(d).

[0023] Conductor patterns are generally made of metal (for example, copper foil) and therefore have high thermal conductivity. In other words, the shape of the wiring area affects heat transfer from the shunt resistor 10 to the electronic component 21 via the circuit board 20. In this example, among the conductor layers L1 to L4 of the circuit board 20, each of the wiring area X2 and X3 where the conductor patterns constituting the low heat-transfer conductor layer are placed has a third area Z3 between the first area Z1 and the second area Z2, which is narrower than the first area Z1 and the second area Z2. This suppresses heat transfer to the electronic component 21 via the circuit board 20 compared to when there is no third area Z3.

[0024] <Effects and Actions> As described above, according to the sensor unit 1 of this embodiment, the conductor layers L1 to L4 of the circuit board 20 are composed of conductor patterns arranged to pass through specific wiring target regions X1 to X4. Here, the wiring target regions X2 and X3 consist of a first region Z1 in which the wiring target regions X2 and X3 overlap in the thickness direction of the circuit board 20 at the connection point between the shunt resistor 10 and the circuit board 20, a second region Z2 in which the wiring target regions X1 to X4 overlap in the thickness direction with respect to the electronic components, and a third region Z3 located between the first region Z1 and the second region Z2, which is at least narrower than the first region Z1 of the first region Z1 and the second region Z2. Conductor patterns are generally formed of metal (for example, copper, etc.), and therefore have a higher thermal conductivity than insulating layers B1 to B5 formed of resin, etc. In other words, the shape of the wiring target regions X1 to X4 in which the conductor patterns are arranged affects the heat transfer from the shunt resistor 10 to the electronic components via the circuit board 20. In this configuration, the sensor unit 1 has a third region Z3 that is narrower than the first region Z1 between the first region Z1 and the second region Z2 of the wiring target regions X2 and X3. Therefore, heat transfer to the electronic components 21 can be suppressed compared to when the third region Z3 is absent. Accordingly, this configuration of the sensor unit 1 makes it possible to suppress the temperature rise of the electronic components 21 mounted on the circuit board 20 and to miniaturize the sensor unit 1.

[0025] Furthermore, according to the sensor unit 1 of this embodiment, the circuit board 20 is arranged so as to overlap the shunt resistor 10. This stacked structure allows the pair of busbars 11 of the shunt resistor 10 and the conductor pattern of the circuit board 20 to be directly connected, for example, via solder. This makes it possible to miniaturize the sensor unit 1 compared to the case where the shunt resistor 10 and the circuit board 20 are connected via a separate component for suppressing heat transfer (for example, a heat transfer suppression relay plate).

[0026] Furthermore, according to the sensor unit 1 of this embodiment, at least one of the plurality of conductor layers L1 to L4 is a low heat transfer conductor layer on which a conductor pattern is provided in the wiring target regions X1 to X4 having a first region Z1, a second region Z2, and a third region Z3. When the circuit board 20 has a plurality of conductor layers L1 to L4 (i.e., a so-called multilayer board), if at least a portion of the plurality of conductor layers L1 to L4 are low heat transfer conductor layers L2 and L3, heat transfer to the electronic component 21 via the circuit board 20 can be suppressed.

[0027] Furthermore, according to the sensor unit 1 of this embodiment, the low heat transfer conductor layers L2 and L3 are sandwiched between a pair of full-surface conductor layers L1 and L4 (for example, a GND layer) in the thickness direction of the circuit board 20. The electromagnetic shielding effect of the full-surface conductor layers L1 and L4 can reduce noise in the conductor patterns included in the low heat transfer conductor layers L2 and L3.

[0028] <Other forms> It should be noted that the present invention is not limited to the embodiments described above, and various modifications can be adopted within the scope of the present invention. For example, the present invention is not limited to the embodiments described above, and can be modified, improved, etc. as appropriate. Furthermore, the material, shape, dimensions, number, placement, etc. of each component in the embodiments described above are arbitrary and not limited as long as they can achieve the present invention.

[0029] For example, in the above embodiment, as shown in Figures 4(a) to 4(d), a pair of left and right notches 22 are formed in the intermediate region of each of the wiring target areas X2 and X3, so that a third region Z3, which is narrower than the first region Z1 and the second region Z2, is provided in each of the wiring target areas X2 and X3 (see Figures 4(b) and 4(c)). In contrast, as shown in Figures 5(a) to 5(d), a through hole 23 may be formed in the intermediate region of each of the wiring target areas X2 and X3, so that a third region Z3, which is narrower than the first region Z1 and the second region Z2, is provided in each of the wiring target areas X2 and X3 (see Figures 5(b) and 5(c)). According to the modified examples shown in Figures 5(a) to 5(d), the same effects and advantages as those described above in the above embodiment can be achieved.

[0030] Furthermore, as shown in Figures 6(a) to 6(d), all of the conductor layers L1 to L4 are low heat transfer conductor layers, and in each of the wiring target areas X1 to X4, a pair of left and right notches 22 are formed in the intermediate area, so that in each of the wiring target areas X1 to X4, a third area Z3 is provided that is narrower than the first area Z1 and the second area Z2. Similarly, as shown in Figures 7(a) to 7(d), all of the conductor layers L1 to L4 are low heat transfer conductor layers, and in each of the wiring target areas X1 to X4, through holes 23 are formed in the intermediate area, so that in each of the wiring target areas X1 to X4, a third area Z3 is provided that is narrower than the first area Z1 and the second area Z2. According to the modified examples shown in Figures 6(a) to 6(d) and Figures 7(a) to 7(d), the effects and benefits of the above-described embodiment can be achieved, excluding the shielding effect of external electromagnetic waves, etc., by the full-surface conductor layer.

[0031] Furthermore, as shown in Figures 8 and 9(a) to 9(d), a pair of left and right notches 22 corresponding to the pair of left and right notches 22 in the above embodiment may be formed on the circuit board 20 itself. As a result, in addition to all of the conductor layers L1 to L4 becoming low heat transfer conductor layers, a pair of left and right notches 22 are formed in each of the wiring target areas X1a to X4a, so that a third area Z3 narrower than the first area Z1 and the second area Z2 is provided in each of the wiring target areas X1a to X4a. Furthermore, a pair of left and right notches 22 are also formed in each of the insulating layers B1 to B5, so that each of the insulating layers B1 to B5 has a shape corresponding to the shape of each of the conductor layers L1 to L4.

[0032] Similarly, as shown in Figures 10 and 11(a) to 11(d), through-holes 23 corresponding to the through-holes 23 in the modified examples shown in Figures 5(a) to 5(d) and 7(a) to 7(d) may be formed in the circuit board 20 itself. As a result, all of the conductor layers L1 to L4 become low heat transfer conductor layers, and the formation of through-holes 23 in each of the wiring target areas X1b to X4b provides a third area Z3 in each of the wiring target areas X1b to X4b that is narrower than the first area Z1 and the second area Z2. Furthermore, by forming through-holes 23 in each of the insulating layers B1 to B5, each of the insulating layers B1 to B5 will have a shape corresponding to the shape of each of the conductor layers L1 to L4. According to the modified examples shown in Figures 8 and 9(a) to 9(d), and the modified examples shown in Figures 10 and 11(a) to 11(d), it is possible to suppress not only heat transfer through multiple conductor layers L1 to L4, but also heat transfer through multiple insulating layers B1 to B5. Therefore, heat transfer through the circuit board 20 can be further suppressed.

[0033] Furthermore, in the above embodiments and each of the above modifications, the third region Z3 located between the first region Z1 and the second region Z2 is configured to be narrower in width (length in the left-right direction) than the first region Z1 and the second region Z2. In contrast, the third region Z3 located between the first region Z1 and the second region Z2 only needs to be narrower in width (length in the left-right direction) than the first region Z1, and the width (length in the left-right direction) between it and the second region Z2 does not matter.

[0034] Herein, the features of the embodiment of the sensor unit 1 according to the present invention described above are briefly summarized below.

[0035] [1] A shunt resistor (10) having a pair of conductors (11) and a resistor (12) sandwiched between the pair of conductors (11) and electrically connected to each of the pair of conductors (11), A circuit board (20) having a conductor pattern electrically connected to each of the pair of conductors (11), and an electronic component (21) that performs calculations using the potential difference between the pair of conductors (11) based on an input obtained through the conductor pattern, A sensor unit (1) comprising, The circuit board (20) is The device comprises an insulating layer (B1 to B5) having a wiring surface for providing the aforementioned conductor pattern, and a conductor layer (L1 to L4) composed of the aforementioned conductor pattern arranged to pass through a wiring target region (X1 to X4) on the wiring surface, The aforementioned wiring target area (X2, X3) is The connection point between the shunt resistor (10) and the circuit board (20) has a first region (Z1) in which the wiring target area overlaps with the circuit board (20) in the thickness direction, the connection point between the shunt resistor (10) and the circuit board (20), a second region (Z2) in which the wiring target area overlaps with the electronic component (21) in the thickness direction, and a third region (Z3) between the first region (Z1) and the second region (Z2) that is narrower than at least the first region (Z1) of the first region (Z1) and the second region (Z2). Sensor unit (1).

[0036] According to the sensor unit described in [1] above, the conductor layer of the circuit board is composed of a conductor pattern arranged to pass through a specific wiring target area. Here, the wiring target area consists of a first area in which the wiring target area overlaps in the thickness direction of the circuit board at the connection point between the shunt resistor and the circuit board, a second area in which the wiring target area overlaps in the thickness direction with the electronic component, and a third area between the first and second areas that is narrower than at least the first area of ​​the first and second areas. Conductor patterns are generally formed of metal (e.g., copper), and therefore have a higher thermal conductivity than insulating layers formed of resin or the like. In other words, the shape of the wiring target area where the conductor pattern is arranged affects heat transfer from the shunt resistor to the electronic component via the circuit board. The sensor unit with this configuration has a third area that is narrower than the first area between the first and second areas of the wiring target area, so that heat transfer to the electronic component can be suppressed compared to when there is no third area. Therefore, this sensor unit configuration makes it possible to suppress the temperature rise of electronic components mounted on the circuit board and to miniaturize the sensor unit.

[0037] [2] In the sensor unit (1) described in [1] above, The circuit board (20) is positioned so as to overlap the shunt resistor (10). Sensor unit (1).

[0038] According to the sensor unit described in [2] above, the circuit board is positioned so as to overlap the shunt resistor. This stacked structure allows the pair of conductors of the shunt resistor and the conductor pattern of the circuit board to be directly connected, for example, via solder. This makes it possible to miniaturize the sensor unit compared to cases where the shunt resistor and the circuit board are connected via a separate component for suppressing heat transfer (for example, a heat transfer suppression relay plate).

[0039] [3] In the sensor unit (1) described in [1] above, The circuit board (20) has a plurality of conductor layers (L1 to L4), At least one of the plurality of conductor layers (L1 to L4) is a low heat transfer conductor layer (L2, L3) provided in the wiring target region having the conductor pattern a first region (Z1), a second region (Z2), and a third region (Z3). Sensor unit (1).

[0040] According to the sensor unit described in [3] above, at least one of the multiple conductor layers is a low heat transfer conductor layer on which a conductor pattern is provided in a wiring target region having a first region, a second region, and a third region. When a circuit board has multiple conductor layers (i.e., a so-called multilayer board), if at least a portion of the multiple conductor layers are low heat transfer conductor layers, heat transfer to electronic components via the circuit board can be suppressed.

[0041] [4] In the sensor unit (1) described in [3] above, The plurality of conductor layers (L1 to L4) are, The conductor pattern includes a full-surface conductor layer (L1, L4) provided in the wiring target area (X1, X4) having a first region (Z1) and a second region (Z2) but not a third region (Z3), and is configured such that the low heat transfer conductor layer (L2, L3) is sandwiched between the pair of full-surface conductor layers (L1, L4) in the thickness direction. Sensor unit (1).

[0042] According to the sensor unit described in [4] above, the low heat transfer conductor layer is sandwiched between a pair of full-surface conductor layers (e.g., a GND layer) in the thickness direction of the circuit board. The electromagnetic shielding effect of the full-surface conductor layers reduces noise in the conductor pattern contained within the low heat transfer conductor layer.

[0043] [5] In the sensor unit (1) described in [3] above, All of the aforementioned plurality of conductor layers (L1 to L4) are the low heat transfer conductor layers. The insulating layers (B1 to B5) have a shape corresponding to the shape of the low heat-conducting layer. Sensor unit (1).

[0044] According to the sensor unit described in [5] above, all conductor layers are low heat transfer conductor layers, and the insulating layer also has a shape corresponding to the shape of the low heat transfer conductor layer. As a result, not only heat transfer through the conductor layers but also heat transfer through the insulating layer can be suppressed. Therefore, heat transfer through the circuit board can be suppressed even more effectively. [Explanation of Symbols]

[0045] 1 Sensor Unit 10 Shunt resistors 11 Busbar (conductor) 12 Resistors 20 Circuit boards 21 Electronic Components B1-B5 Insulating Layer L1~L4 Conductor Layers X1~X4 Wiring target area Z1 1st area Z2 2nd area Z3 3rd area

Claims

1. A shunt resistor having a pair of conductors and a resistor sandwiched between the pair of conductors and electrically connected to each of the pair of conductors, A circuit board having a conductor pattern electrically connected to each of the pair of conductors, and an electronic component that performs calculations using the potential difference between the pair of conductors based on an input obtained through the conductor pattern, A sensor unit comprising, The aforementioned circuit board is The insulating layer has a wiring surface for providing the aforementioned conductor pattern, and the conductor layer is composed of the aforementioned conductor pattern arranged to pass through the wiring target region of the wiring surface, The aforementioned wiring target area is, The connection point between the shunt resistor and the circuit board has a first region in which the wiring target area overlaps in the thickness direction of the circuit board; the connection point between the shunt resistor and the circuit board has a second region in which the wiring target area overlaps in the thickness direction of the electronic component; and a third region between the first region and the second region, which is narrower than at least the first region of the first and second regions. Sensor unit.

2. In the sensor unit according to claim 1, The circuit board is positioned so as to overlap the shunt resistor. Sensor unit.

3. In the sensor unit according to claim 1, The circuit board has a plurality of the conductor layers, At least one of the plurality of conductor layers is a low heat transfer conductor layer provided in the wiring target region having the conductor pattern in the first region, the second region and the third region. Sensor unit.

4. In the sensor unit according to claim 3, The plurality of conductor layers are The conductor pattern includes a full-surface conductor layer provided in the wiring target region having the first region and the second region but not the third region, and in the thickness direction, the low heat transfer conductor layer is sandwiched between a pair of the full-surface conductor layers. Sensor unit.

5. In the sensor unit according to claim 3, All of the aforementioned plurality of conductor layers are the low heat transfer conductor layers, The insulating layer has a shape corresponding to the shape of the low heat transfer conductor layer. Sensor unit.

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