Module with capacitor, power conversion circuit, and inverter for aircraft

Abstract

To provide a smoothing circuit for an inverter which has sufficient cooling performance while suppressing mass increase.SOLUTION: A smoothing circuit 2 for an inverter comprises: a parallel flat plate 21; a plurality of capacitors 22 arranged in matrix and mounted on the parallel flat plate 21; and a thermal conduction sheet 23 provided by being interposed between the parallel flat plate 21 and a housing 4 in an area overlapping with mounting areas 21c of the plurality of capacitors 22 when viewed along a normal direction of the parallel flat plate 21. The plurality of capacitors 22 are arranged in a row direction and a column direction and so that the adjacent terminals 221 of the adjacent capacitors 22 become the same polarity.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to A module having a capacitor, a power conversion circuit, The present invention also relates to inverters for aircraft. [Background technology]

[0002] As is well known, an inverter is composed of a rectifier circuit that rectifies AC power provided from an AC power source to generate DC power, a smoothing circuit that smoothes the generated DC power, and an inverse conversion circuit that converts the smoothed DC power into AC power by switching.

[0003] Various types of heat countermeasures are taken for inverters as necessary. For example, Patent Document 1 discloses a configuration in which a semiconductor module is attached to a heat sink and external air sent from a fan hits fins on the heat sink to dissipate heat generated by the semiconductor module. In this configuration, a smoothing capacitor is placed on the opposite side of the heat sink from the fan, and the external air sent from the fan hits the capacitor on the downstream side of the heat sink, which also promotes heat dissipation from the capacitor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-189869 A Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, technology to electrify propulsion fan motors in aircraft has been developed. To electrify propulsion fan motors, an inverter is required to drive the motor.

[0006] In an aircraft inverter, the amount of current that flows is significantly larger than, for example, an inverter for a vehicle, and therefore the loss that occurs in the smoothing capacitor is also large. Therefore, it cannot be said that a heat countermeasure such as that disclosed in Patent Document 1, which merely cools the capacitor in addition to cooling the semiconductor module with a fan, is sufficient.

[0007] Therefore, as a heat countermeasure for the smoothing capacitor in the inverter for aircraft, it is conceivable to place a thermal conductive sheet made of TIM (Thermal Interface Material) between the parallel plate on which the capacitor is mounted and the housing. With this configuration, it becomes possible to quickly transfer the heat generated in the capacitor and the parallel plate to the housing and dissipate it to the outside.

[0008] However, in the case of inverters for aircraft, there is a big problem in adopting a thermal countermeasure using a thermal conductive sheet. That is, weight reduction is strongly required for all parts installed in aircraft, and inverters for driving propulsion fan motors are no exception, and weight reduction in grams is also strongly required. However, when a thermal conductive sheet is provided for thermal countermeasures for smoothing capacitors, a thermal conductive sheet of a size that completely covers the mounting area of ​​the capacitor is required, and an increase in mass according to the size is unavoidable. In particular, in inverters for aircraft, the required capacitor capacity is orders of magnitude larger than that of inverters for vehicles, and therefore the number of capacitors to be mounted is also large. In other words, the mounting area for a group of capacitors is also large. Therefore, the required size of the thermal conductive sheet, and therefore the increase in mass due to the provision of the thermal conductive sheet, becomes large.

[0009] The present invention has been made to solve the above problems, and provides a cooling device that has sufficient cooling performance while suppressing an increase in mass. , a module including a capacitor, a power conversion circuit, and an inverter for an aircraft - Patents.com The purpose is to provide. [Means for solving the problem]

[0010] In order to achieve the above object, the present invention provides the following means.

[0011] That is, the present invention provides Module with capacitors And, Consists of laminated bus bars or thick copper substrates The device comprises a parallel plate, a plurality of capacitors arranged in a matrix and mounted on the parallel plate, and a thermally conductive sheet interposed between the parallel plate and a housing in an area overlapping with the mounting area of ​​the plurality of capacitors when viewed along the normal direction of the parallel plate, and is characterized in that the plurality of capacitors are arranged in the row and column directions such that adjacent terminals of adjacent capacitors have the same polarity.

[0012] For example, when all of the capacitors are arranged in the same orientation in a matrix, as illustrated in FIG. 7, the terminals 91 of adjacent capacitors 9 in either the row direction or the column direction (the column direction in the example of FIG. 7) have opposite polarities. In this case, it is necessary to provide a separation distance of a predetermined insulation distance d1 or more between the terminals 91 of adjacent capacitors 9 in that direction to ensure insulation between terminals of different polarities. In contrast, in the above configuration, the capacitors are arranged so that the terminals of adjacent capacitors have the same polarity in both the row direction and the column direction. According to this configuration, it is not necessary to provide such a separation distance of d1 or more between the terminals of adjacent capacitors in both the row direction and the column direction, and it is sufficient to provide a separation distance of a predetermined insulation distance d2 or more to ensure insulation between terminals of the same polarity (it goes without saying that "d1>d2"). Therefore, it is possible to increase the density of the capacitors, and the mounting area of ​​the capacitors can be reduced. This makes it possible to reduce the size of the thermally conductive sheet, and therefore the increase in mass due to the provision of the thermally conductive sheet. Therefore, sufficient cooling performance can be achieved while suppressing an increase in mass.

[0013] Preferably, in the inverter smoothing circuit, the thermal conduction sheet is composed of a plurality of sheet pieces having different thermal conductivities, and the sheet pieces having a relatively high thermal conductivity are arranged in areas where the amount of heat generated is relatively high.

[0014] When the thermal conductivity of the thermally conductive sheet is determined by the content of the thermally conductive filler, the higher the thermal conductivity, the larger the mass. In the above configuration, a sheet piece with a relatively low thermal conductivity is arranged in the area overlapping the mounting area where the heat generation is relatively small, so that the total mass of the thermally conductive sheet can be reduced compared to the case where a thermally conductive sheet with a thermal conductivity assuming a relatively large heat generation area is uniformly arranged in the entire area overlapping the mounting area. In addition, since multiple sheet pieces with different thermal conductivity are used according to the heat generation amount of each area, the heat is more easily transferred to the housing in the area where the heat generation amount is large, and the unevenness of the heat generation amount in the plane of the parallel plate is canceled out, and the uniformity of the temperature in the plane of the parallel plate is improved. By increasing the uniformity of the temperature in the plane of the parallel plate, it is possible to uniform the life of multiple capacitors mounted thereon, and the reliability of the product can be improved.

[0015]

[0016]

[0017] Preferably, Module with capacitors The present invention is characterized in that the plurality of capacitors are of the same type, and a sheet piece having a relatively high thermal conductivity is disposed in an area corresponding to an area in which a capacitor surrounded by other capacitors is mounted.

[0018] As described above, by arranging the multiple capacitors in both the row and column directions so that the adjacent terminals of adjacent capacitors have the same polarity, it is possible to increase the density of the multiple capacitors, but as the density of the multiple capacitors increases, it becomes difficult for heat generated by a capacitor that is surrounded by other capacitors to be dissipated to the surroundings. With the above configuration, a sheet piece with a relatively high thermal conductivity is arranged in an area corresponding to the area in which such a capacitor is mounted, so that the heat generated by such a capacitor can be effectively dissipated.

[0019] Preferably, It is preferable that a power conversion circuit is configured using a module including the capacitor.

[0020]

[0021] The present invention also relates to the Module with capacitors of Used Inverters for aircraft Suitable This is the target.

[0022] Aircraft inverters require high cooling performance while also being lightweight. Module with capacitors The FA-1000 series achieves sufficient cooling performance while minimizing the increase in mass, and is therefore able to meet both of these requirements. Effect of the Invention

[0023] According to the present invention, it is possible to suppress an increase in mass while maintaining sufficient cooling performance. Module with capacitor, power conversion circuit, and aircraft inverter can be obtained. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a block diagram of an inverter including a module including a capacitor according to an embodiment. [Diagram 2] FIG. [Diagram 3] Exploded view of the smoothing circuit. [Figure 4] FIG. [Diagram 5]FIG. 4 is a diagram for explaining an arrangement of a plurality of capacitors. [Figure 6] 11A and 11B are diagrams for explaining an aspect in which an area in which a thermally conductive sheet is disposed is divided according to the amount of heat generated. [Figure 7] FIG. 13 is a diagram showing an arrangement of a plurality of capacitors as a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0026] <Smoothing circuit configuration> The configuration of a smoothing circuit according to an embodiment will be described with reference to Fig. 1 to Fig. 4. Fig. 1 is a block diagram of an inverter INV provided with a smoothing circuit 2. Figs. 2, 3, and 4 are a perspective view, an exploded view, and a plan view of the smoothing circuit 2, respectively.

[0027] The smoothing circuit 2 is an inverter smoothing circuit, and is mounted on an inverter INV for an aircraft, specifically, for example, an inverter INV for driving a propulsion fan motor M of the aircraft. As shown in FIG. 1, the inverter INV includes a rectifier circuit 1, a smoothing circuit 2, and an inverse conversion circuit 3, and these components 1 to 3 are housed in a housing 4. The rectifier circuit 1 is connected to an AC power source AC, and rectifies AC power provided from the AC power source AC to generate DC power and output the DC power to the smoothing circuit 2. The smoothing circuit 2 smoothes the DC power provided from the rectifier circuit 1 and provides the DC power to the inverse conversion circuit 3. The inverse conversion circuit 3 includes a switching element and the like, and converts the DC power provided from the smoothing circuit 2 into AC power by switching, and outputs the AC power to the propulsion fan motor M of the aircraft. The configuration of the inverter INV is well known, so a detailed description thereof will be omitted.

[0028] As shown in FIGS. 2 to 4, the smoothing circuit 2 includes a parallel plate 21, a plurality of capacitors (smoothing capacitors) 22, and a heat conductive sheet .

[0029] (parallel plate 21) The parallel plate 21 is formed of, for example, a laminated bus bar capable of handling a large current. The parallel plate 21 has a substantially rectangular shape in a plan view, and a connection area (first connection area) 21a to which the rectifier circuit 1 is connected is provided on one of a pair of opposing ends, and a connection area (second connection area) 21b to which the inverter circuit 3 is connected is provided on the other end. However, the second connection area 21b has a comb-like shape as a whole due to the extension of multiple connection pieces 211, and a semiconductor module 31 such as an IGBT, which is a component of the inverter circuit 3, is connected to each connection piece 211. The area excluding the connection areas 21a and 21b is a mounting area 21c for multiple capacitors 22, and the multiple capacitors 22 are mounted here.

[0030] (Capacitor 22) The multiple capacitors 22 are of the same type, and are, for example, film capacitors for mounting on a printed circuit board. As shown in Fig. 4, one or more pairs of terminals (terminal electrodes) 221 (two pairs in the illustrated example) are provided on the lower surface of the capacitor 22, one of the pair of terminals 221 is connected to the high voltage side, and the other is connected to the low voltage side. When distinguishing between the two terminals 221, the terminal 221 connected to the high voltage side and serving as the positive electrode side is called the "positive terminal 221a," and the terminal 221 connected to the low voltage side and serving as the negative electrode side is called the "negative terminal 221b."

[0031] Here, the arrangement of the plurality of capacitors 22 will be described in further detail with reference to Fig. 5 in addition to Fig. 2 to Fig. 4. Fig. 5 is a diagram for explaining the arrangement.

[0032] Now, if the direction parallel to the extension direction of each connection region 21a, 21b within the plane of parallel plate 21 is defined as the row direction, and the direction perpendicular to the row direction within the plane of parallel plate 21 is defined as the column direction, then the multiple capacitors 22 are mounted on parallel plate 21 by being arranged in a matrix along the row and column directions.

[0033] Each capacitor 22 is arranged in a position (first position) P1 in which the axial direction T from the negative terminal 221b to the positive terminal 221a is aligned with the column direction and the negative terminal 221b faces the first connection region 21a, or in the opposite position (second position) P2 in which the axial direction T is aligned with the column direction and the positive terminal 221a faces the first connection region 21a, where adjacent capacitors 22 in the row direction have the same position, and adjacent capacitors 22 in the column direction have the opposite position. By arranging each capacitor 22 in such a position, the multiple capacitors 22 are arranged such that adjacent terminals 221 of adjacent capacitors 22 have the same polarity in both the row direction and the column direction.

[0034] According to this arrangement, in both the row and column directions, there is no need to provide a separation distance between adjacent capacitors 22 that is equal to or greater than a predetermined insulation distance d1 (see FIG. 7) for ensuring insulation between terminals of different polarities, and it is sufficient to provide a separation distance equal to or greater than a predetermined insulation distance d2 for ensuring insulation between terminals of the same polarity (it goes without saying that "d1>d2"). This makes it possible to increase the density of the capacitors 22, and to reduce the area of ​​the mounting region 21c required for mounting the capacitors 22.

[0035] (Thermal Conduction Sheet 23) 2 to 4 are referred to again. As shown in FIG. 3, the thermally conductive sheet 23 is provided between the parallel plate 21 and the housing 4 (specifically, the bottom surface 41 of the housing 4) in which the parallel plate 21 is accommodated, in a region overlapping the mounting region 21c when viewed along the normal direction of the parallel plate 21. Specifically, the thermally conductive sheet 23 is disposed between the parallel plate 21 and the bottom surface 41 of the housing 4, and is provided in contact with the parallel plate 21 over the entire upper surface and in contact with the bottom surface 41 over the entire lower surface. By providing the thermally conductive sheet 23 between the parallel plate 21 and the housing 4, heat generated in the capacitor 22 and the parallel plate 21 is promptly transferred to the housing 4. The housing 4 is formed of a material (e.g., aluminum) having a sufficiently high thermal conductivity, and the heat transferred to the housing 4 is promptly dissipated to the outside.

[0036] The thermally conductive sheet 23 is made of a thermal interface material (TIM). The TIM is a material in which a thermally conductive additive (filler) is mixed into an insulating base material such as a silicone polymer, and the higher the content of the additive, the higher the thermal conductivity. Examples of additives that can be used include alumina, silica, and silicon nitride.

[0037] The thermally conductive sheet 23 is composed of a plurality of sheet pieces 231. The plurality of sheet pieces 231 include pieces with different thermal conductivities, and the sheet pieces 231 with relatively high thermal conductivity are arranged in an area with a relatively high amount of heat generation, and the sheet pieces 231 with relatively low thermal conductivity are arranged in an area with a relatively low amount of heat generation. Specifically, the area where the thermally conductive sheet 23 is arranged (i.e., the area overlapping with the mounting area 21c when viewed along the normal direction of the parallel plate 21) is divided into a plurality of types of areas according to the amount of heat generation, and the sheet pieces 231 with a thermal conductivity specified according to the amount of heat generation of the area are arranged in each divided area.

[0038] Here, a mode of dividing the area where the thermally conductive sheet 23 is disposed according to the amount of heat generated will be specifically described with reference to Fig. 6. Fig. 6 is a diagram for explaining this mode.

[0039] If sheet pieces 231 with the same thermal conductivity are uniformly provided over the entire area overlapping with mounting area 21c when viewed along the normal direction of parallel plate 21 (or if thermally conductive sheet 23 is not provided), the in-plane temperature of parallel plate 21 tends to be higher the closer to second connection area 21b to which semiconductor module 31 is connected (i.e., closer to connection piece 211). Furthermore, the area where capacitors 22 surrounded by other capacitors 22 are mounted among the multiple capacitors 22 arranged in a matrix and the area nearby tend to be higher in temperature.

[0040] One of the reasons why the temperature tends to be higher near the second connection region 21b is thought to be the loss caused by the flow of AC current. That is, when AC current flows between the semiconductor module 31 and the parallel plate 21, a loss occurs there according to the effective value of the AC current. In particular, as shown in FIG. 4, when the connection piece 211 is narrow in width to expose the signal connection part 311 (that is, the signal connection part 311 for connecting a signal line for inputting a signal to the semiconductor module 31), the current density in the connection piece 211 is high, so that the loss generated here is likely to be particularly large. Furthermore, when the temperature of the copper foil provided on the parallel plate 21 rises due to the effect of the loss generated, the resistance increases, and the loss generated further increases, creating a vicious cycle. For these reasons, it is thought that the temperature tends to be higher near the second connection region 21b.

[0041] In addition, the semiconductor module 31 connected to the second connection region 21b generates more heat than the capacitor 22, and the connection piece 211 to which the semiconductor module 31 is connected and the surrounding area also rise in temperature due to the heat from the semiconductor module 31, which has a relatively high temperature. This is also thought to be one of the reasons why the temperature tends to rise closer to the second connection region 21b.

[0042] On the other hand, the reason why the area where the capacitor 22 surrounded by other capacitors 22 is mounted and the area nearby tend to become hot is considered to be because the heat generated by the capacitor 22 surrounded by other capacitors 22 is difficult to dissipate. Needless to say, the more the number of capacitors 22 around it, the more difficult it becomes to dissipate heat. In other words, when a plurality of capacitors 22 are arranged in a matrix, a capacitor 22 sandwiched between other capacitors 22 in all directions, including the row direction, column direction, and diagonal direction, that is, a capacitor 22 surrounded by eight capacitors 22, is the most difficult to dissipate heat. In particular, the plurality of capacitors 22 are arranged in such a way that the polarities of the adjacent terminals 221 of the capacitors 22 adjacent to each other in both the row direction and the column direction are the same, thereby increasing the density of the capacitors 22. Therefore, the heat dissipation of the capacitors 22 surrounded by other capacitors 22 is particularly easily hindered, and the area where such a capacitor 22 is mounted is particularly likely to become hot.

[0043] In consideration of these trends, in this embodiment, the area where the thermally conductive sheet 23 is disposed is divided into three types of areas, a first area Mx, a second area My, and a third area Mz, according to the amount of heat generated.

[0044] The first region Mx is a region corresponding to the vicinity of the second connection portion 21b (i.e., the portion where the connection piece 211 is provided) to which the semiconductor module 31 is connected. Here, the gap between the capacitors 22 in the first row and the capacitors 22 in the second row counting from the connection piece 211 side is defined as the boundary, and the region on the connection piece 211 side of this boundary is defined as the first region Mx.

[0045] The second region My is a region corresponding to a region in which a capacitor 22 surrounded by other capacitors 22 is mounted (i.e., a region overlapping with a region in which such a capacitor 22 is mounted when viewed along the normal direction of the parallel plate 21). However, here, a capacitor 22 that is sandwiched between other capacitors 22 in all directions, including the row direction, column direction, and diagonal direction, i.e., a capacitor 22 that is surrounded by eight capacitors 22, is defined as a "capacitor 22 surrounded by other capacitors 22."

[0046] The third region Mz is a region excluding the first region Mx and the second region My.

[0047] In each of the three regions Mx, My, and Mz thus defined, a sheet piece 231 having a thermal conductivity defined according to the amount of heat generated in the region is disposed. The manner in which the thermal conductivity of the sheet piece 231 disposed in each of the regions Mx, My, and Mz is defined will be described with reference to Figs. 3 and 6.

[0048] In determining the thermal conductivity Kz of the sheet piece 231 (referred to as the "third sheet piece 231z" when distinguishing it from the other sheet pieces 231) arranged in the third region Mz, first, the average generated loss A (W) of the entire parallel plate 21 is estimated based on the average temperature of the entire parallel plate 21, etc. From the estimated generated loss A (W) and the allowable temperature rise To (℃) of the parallel plate 21, the thermal resistance α=To / A required for the sheet piece 231z is specified. Between the thermal resistance α (℃ / W) and the thermal conductivity Kz, the relationship "α=d / (Kz×So)" is established (where "So" is the entire area of ​​the parallel plate 21, and "d" is the thickness of the sheet piece 231, and all the multiple sheet pieces 231 have the same thickness). Therefore, the thermal conductivity Kz (W / m·K) calculated based on this relational expression is set as the thermal conductivity Kz of the third sheet piece 231z.

[0049] Next, when defining the thermal conductivity Kx of the sheet piece 231 disposed in the first region Mx (also referred to as "the first sheet piece 231x" when distinguishing it from other sheet pieces 231), first, based on the difference between the temperature of the first region Mx and the average temperature of the entire parallel plate 21, etc., in the first region Mx, the additional generated loss B (W) generated from the average generated loss A is estimated. From the estimated additional generated loss B (W) and the allowable temperature rise To (°C) of the parallel plate 21, the thermal resistance β = To / (A + B) required for the sheet piece 231x is specified. Between the thermal resistance β (°C / W) and the thermal conductivity Kx, the relationship of "β = d / (Kx × Sx)" holds (where "Sx" is the area of the first region Mx and "d" is the thickness of the sheet piece 231). Therefore, the thermal conductivity Kx (W / m·K) calculated based on this relational expression is taken as the thermal conductivity Kx of the first sheet piece 231x.

[0050] Also, when defining the thermal conductivity Ky of the sheet piece 231 disposed in the second region My (also referred to as "the second sheet piece 231y" when distinguishing it from other sheet pieces 231), first, based on the difference between the temperature of the second region My and the average temperature of the entire parallel plate 21, etc., in the second region My, the additional generated loss C (W) generated from the average generated loss A is estimated (in many cases, "C < B"). From the estimated additional generated loss C (W) and the allowable temperature rise To (°C) of the parallel plate 21, the thermal resistance γ = To / (A + C) required for the sheet piece 231y is specified. Between the thermal resistance γ (°C / W) and the thermal conductivity Ky, the relationship of "γ = d / (Ky × Sy)" holds (where "Sy" is the area of the second region My and "d" is the thickness of the sheet piece 231). Therefore, the thermal conductivity Ky (W / m·K) calculated based on this relational expression is taken as the thermal conductivity Ky of the second sheet piece 231y.

[0051] In this way, the thermal conductivity Ki (i=x, y, z) of each of the first to third sheet pieces 231i (i=x, y, z) is specified based on the amount of heat generated in the region Mi (i=x, y, z) in which the sheet piece 231i is disposed. According to the above-mentioned specified embodiment, the amount of heat generated per unit area of ​​each region Mi (i.e., the loss generated per unit area) and the thermal conductivity Ki of the corresponding sheet piece 231i are proportional to each other. Therefore, when the amount of heat generated per unit area is larger in the order of the first region Mx, the second region My, and the third region Mz, the thermal conductivity of the sheet piece 231 is larger in the order of the first sheet piece 231x, the second sheet piece 231y, and the third sheet piece 231z, and the area with the larger amount of heat generated is more likely to transfer heat to the housing 4. Also, in the above example, the thermal conductivity Ki of each sheet piece 231i is specified so that the temperature, which is the product of the loss generated and the thermal resistance in each region Mi, is the same value. That is, the thermal conductivity Ki of each sheet piece 231i is specified so that the temperature in each region Mi becomes equal as a result of the transfer of the heat amount according to the heat generation amount to the housing 4. Therefore, the unevenness of the heat generation amount in the plane of the parallel plate 21 is appropriately canceled, and the uniformity of the temperature in the plane of the parallel plate 21 is sufficiently increased. However, since the housing 4 is formed of a material having a sufficiently high thermal conductivity compared to the sheet piece 231, the heat transferred to the housing 4 is quickly uniformized inside the housing 4 and dissipated to the outside.

[0052] <Effects> The smoothing circuit 2 for an inverter according to the above embodiment comprises a parallel plate 21, a plurality of capacitors 22 arranged in a matrix and mounted on the parallel plate 21, and a thermally conductive sheet 23 interposed between the parallel plate 21 and the housing 4 in an area overlapping with the mounting area 21c of the plurality of capacitors 22 when viewed along the normal direction of the parallel plate 21, and the plurality of capacitors 22 are arranged in the row and column directions such that adjacent terminals 221 of adjacent capacitors 22 have the same polarity.

[0053] For example, as illustrated in FIG. 7, when all of the multiple capacitors 9 are arranged in a matrix in the same orientation (for example, a first orientation P1 in which the axial direction T from the negative terminal to the positive terminal is aligned with the column direction and the negative terminal faces the first connection region 21a), the adjacent terminals 91 of the capacitors 9 adjacent in either the row direction or the column direction (the column direction in the example of FIG. 7) have opposite polarities. In this case, it is necessary to provide a separation distance of a predetermined insulation distance d1 or more between the terminals 91 of the adjacent capacitors 9 in that direction to ensure insulation between terminals of different polarities. In contrast, in the above configuration, the multiple capacitors 22 are arranged such that the polarities of the adjacent terminals 221 of the adjacent capacitors 22 are the same in both the row direction and the column direction. According to this configuration, as illustrated in FIG. 4, there is no need to provide a distance of such insulation distance d1 or more between the terminals 221 of adjacent capacitors 22 in either the row direction or the column direction, and it is sufficient to provide a distance of a predetermined insulation distance d2 or more to ensure insulation between terminals of the same polarity (it goes without saying that "d1>d2"). Therefore, it is possible to increase the density of the multiple capacitors 22, and the mounting area 21c of the multiple capacitors 22 can be kept small. This makes it possible to keep the size of the thermally conductive sheet 23, and therefore the increase in mass due to the provision of the thermally conductive sheet 23, small. Therefore, it is possible to achieve sufficient cooling performance while suppressing the increase in mass.

[0054] In particular, when the inverter INV in which the smoothing circuit 2 is provided is an inverter for an aircraft, it is assumed that it will be used in an environment at high altitude (i.e., where the air is thin), so the predetermined insulation distance d1 for ensuring insulation between terminals of different poles is larger (for example, about 10 to 20 mm) than when it is assumed that it will be used on the ground. In the above configuration, it is not necessary to ensure such a large insulation distance d1, so it is possible to significantly improve the density of the multiple capacitors 22.

[0055] In addition, by increasing the density of the capacitors 22, the wiring length of the smoothing circuit 2 is shortened, and the wiring inductance is reduced. Therefore, in the inverter circuit 3, it is also possible to suppress a surge voltage generated during switching.

[0056] Furthermore, when the inverter INV in which the smoothing circuit 2 is provided is an inverter for an aircraft, it is often not permitted to use a fan to radiate heat generated in the smoothing circuit 2 to the outside of the housing 4 (i.e., inside the aircraft). Furthermore, aircraft inverters are often placed in highly polluted spaces, and in this case the inside of the housing 4 must be an airtight space, so that in this case too, a heat countermeasure using a fan cannot be adopted. In this regard, in the above embodiment, the heat conductive sheet 23 is used to move the heat generated in the capacitor 22 and the parallel plate 21 to the housing 4 and radiate it to the outside, so that it is possible to accommodate usage environments in which a fan cannot be used.

[0057] In addition, in the smoothing circuit 2 according to the above embodiment, the thermally conductive sheet 23 is configured to include a plurality of sheet pieces 231 having different thermal conductivities, and the sheet pieces having a relatively high thermal conductivity are arranged in areas where the amount of heat generated is relatively large.

[0058] In the case where the thermal conductivity of the thermally conductive sheet 23 is determined by the content of the thermally conductive filler, the higher the thermal conductivity, the greater the mass. In the above configuration, the sheet piece 231z having a relatively low thermal conductivity is disposed in the area overlapping with the mounting area 21c where the amount of heat generated is relatively small (for example, the third area Mz). Therefore, the total mass of the thermally conductive sheet 23 can be reduced compared to the case where a thermally conductive sheet having a thermal conductivity Kx assuming an area where the amount of heat generated is relatively large (for example, the first area Mx) is uniformly disposed in the entire area overlapping with the mounting area 21c. In addition, the higher the thermal conductivity of the thermally conductive sheet 23, the more expensive it becomes. However, according to the above configuration, the cost related to the thermally conductive sheet 23 can also be reduced. Furthermore, since multiple sheet pieces 231 with different thermal conductivities are used depending on the amount of heat generated in each of the regions Mx, My, Mz, the heat transfers more easily to the housing 4 in the region with a larger amount of heat generated, and unevenness in the amount of heat generated within the plane of the parallel plate 21 is eliminated, improving the uniformity of the in-plane temperature of the parallel plate 21. By improving the uniformity of the in-plane temperature of the parallel plate 21, it becomes possible to uniform the life spans of the multiple capacitors 22 mounted thereon, thereby improving the reliability of the product.

[0059] In the smoothing circuit 2 according to the above embodiment, the sheet piece 231x having a relatively high thermal conductivity is disposed in a vicinity region (first region) Mx of the connection portion where the parallel plate 21 and the semiconductor module 31 are connected.

[0060] Since the semiconductor module 31 tends to generate more heat than the capacitor 22, the vicinity of the semiconductor module 31 is likely to be heated by the heat. Furthermore, when an AC current flows through the connection between the semiconductor module 31 and the parallel plate 21, a loss occurs there according to the effective value of the AC current, and the connection and its vicinity are likely to be heated. According to the above configuration, the sheet piece 231x having a relatively high thermal conductivity is disposed in the first region Mx, which is a region in the vicinity of the connection where the parallel plate 21 and the semiconductor module 31 are connected, so that the heat generated in the vicinity region Mx can be effectively dissipated.

[0061] One of the reasons why the amount of heat generated in the first region Mx is large is that the generated loss is large. Therefore, for example, it is possible to reduce the generated loss by increasing the thickness of the copper foil provided on the parallel plate 21. However, doing so would inevitably increase the mass of the parallel plate 21. In other words, with the above configuration, it is possible to suppress the local temperature rise in the region where the generated loss is large, without increasing the mass of the parallel plate 21.

[0062] Another reason why the amount of heat generated in the first region Mx becomes large is due to the heat received from the semiconductor module 31. Therefore, for example, it is possible to reduce the influence of the heat received from the semiconductor module 31 by providing the connection portion of the semiconductor module 31 (i.e., the connection piece 211) at a position away from the mounting region 21c. However, doing so would inevitably increase the size of the parallel plate 21. In other words, with the above configuration, it is possible to suppress the local temperature rise caused by the heat received from the semiconductor module 31 without increasing the size of the parallel plate 21.

[0063] Furthermore, in the smoothing circuit 2 according to the above embodiment, the multiple capacitors 22 are the same type of capacitors, and a sheet piece 231y having a relatively high thermal conductivity is arranged in an area corresponding to an area (second area) My in which the capacitor 22 is mounted and is surrounded by other capacitors 22.

[0064] As described above, the plurality of capacitors 22 are arranged in both the row and column directions such that adjacent terminals 221 of adjacent capacitors 22 have the same polarity, which makes it possible to increase the density of the plurality of capacitors 22, but when the density of the plurality of capacitors 22 increases, it becomes difficult for heat generated in a capacitor 22 that is surrounded by other capacitors 22 to be dissipated to the surroundings. According to the above configuration, a sheet piece 231y having a relatively high thermal conductivity is disposed in the second region My, which is a region corresponding to the region in which such a capacitor 22 is mounted, so that the heat generated in the capacitor 22 can be effectively dissipated.

[0065] The reason why the amount of heat generated in the second region My is large is that the condensers 22 that are surrounded by other condensers 22 have difficulty in dissipating heat. Therefore, for example, it is possible to increase the distance between adjacent condensers 22 so that sufficient heat can be dissipated from such condensers 22 as well. However, needless to say, this means that the density of the condensers 22 is reduced. In other words, with the above configuration, it is possible to suppress localized temperature rise in the region where the condensers 22 are densely packed, while maintaining the density of the condensers 22 high.

[0066] Furthermore, in the smoothing circuit 2 according to the above embodiment, the thermal conductivity Ki (i=x, y, z) of each of the multiple sheet pieces 231i (i=x, y, z) is defined based on the amount of heat generated in the area Mi (i=x, y, z) in which the sheet piece 231i is arranged.

[0067] According to this configuration, the unevenness of the amount of heat generated within the plane of the parallel plate 21 is appropriately cancelled out, and the uniformity of the temperature within the plane of the parallel plate 21 is sufficiently improved.

[0068] Moreover, the smoothing circuit 2 according to the above embodiment is mounted on an inverter INV for an aircraft.

[0069] Aircraft inverters INV require high cooling performance while also being strongly required to be lightweight. The smoothing circuit 2 according to the above embodiment achieves sufficient cooling performance while minimizing the increase in mass, and is therefore able to meet both of these requirements.

[0070] <Other embodiments> In the above embodiment, the thermally conductive sheet 23 includes a plurality of types of sheet pieces 231x, 231y, and 231x having different thermal conductivities, but all of the plurality of sheet pieces 231 that configure the thermally conductive sheet 23 may have the same thermal conductivity. That is, a plurality of sheet pieces 231 having the same thermal conductivity may be evenly arranged at the same pitch over the entire area overlapping with the mounting area 21c when viewed along the normal direction of the parallel plate 21. Also, in the above embodiment, the thermally conductive sheet 23 includes a plurality of sheet pieces 231, but the thermally conductive sheet 23 may be composed of a single sheet. That is, a single sheet may be disposed so as to cover the entire area overlapping with the mounting area 21c when viewed along the normal direction of the parallel plate 21.

[0071] Although the above configurations cannot suppress temperature unevenness, the heat generated in each capacitor 22 and parallel plate 21 is quickly transferred to the housing 4 via each sheet piece 231 and dissipated to the outside, similar to the above embodiment. Therefore, even with these configurations, it is possible to suppress the temperature rise of each capacitor 22 and parallel plate 21.

[0072] In the above embodiment, the number of sheet pieces 231 arranged in each of the regions Mx, My, and Mz is not limited to that illustrated in the drawing. For example, the sheet pieces 231x, 231y, and 231z arranged in each of the regions Mx, My, and Mz may each be composed of a single sheet piece that is congruent with the region in which it is arranged, or may each be composed of a plurality of sheet pieces that are sufficiently smaller than the region.

[0073] In the above embodiment, the region where the thermally conductive sheet 23 is disposed is divided into three types of regions Mx, My, and Mz according to the amount of heat generated, but the manner of dividing the regions is not limited to this. For example, in the above embodiment, the region corresponding to the region where the capacitor 22 is mounted and surrounded by eight capacitors 22 is set as the second region My, but for example, the region corresponding to the region where the capacitor 22 is mounted and surrounded by seven or more capacitors 22 may be set as the second region My. Also, for example, the third region Mz may be further divided into a region closer to the second connection portion 21b and a region closer to the first connection portion 21a. As the total number of divided regions increases, the number of sheet pieces 231 included in the thermally conductive sheet 23 that have different thermal conductivities increases, making it possible to improve the uniformity of the in-plane temperature of the parallel plate 21.

[0074] In the above embodiment, the thermal conductivity of each sheet piece 231i is adjusted by the content of thermally conductive filler, etc., but the thermal conductivity may also be adjusted by the area of ​​each sheet piece 231i (the area ratio of each sheet piece 231i to the area Mi in which each sheet piece 231i is arranged).

[0075] In the above embodiment, the parallel plate 21 of the smoothing circuit 2 is configured by a laminated bus bar, but the parallel plate 21 is not limited to a laminated bus bar. For example, the parallel plate 21 may be configured by a substrate capable of handling a large current, such as a thick copper substrate.

[0076] In the above embodiment, the total number of capacitors 22 provided in the smoothing circuit 2 may be any number. Furthermore, the number of capacitors 22 arranged in each of the row and column directions may also be any number. Furthermore, the type of capacitor 22 is not limited to a film capacitor, and may be a ceramic capacitor, an electrolytic capacitor, or the like.

[0077] In the above embodiment, the inverter INV is connected to the AC power source AC, but the inverter may be connected to a battery. In this case, the inverter may be configured to include a smoothing circuit 2 and an inverse conversion circuit 3 without including the rectifier circuit 1. That is, in this case, the smoothing circuit 2 is connected to the battery, smoothes the DC power provided therefrom, and provides it to the inverse conversion circuit 3, which converts the provided DC power into AC power and outputs it to the propulsion fan motor M or the like. When the inverter is configured in this way, the first connection region 21a of the parallel plate 21 of the smoothing circuit 2 is connected to a battery.

[0078] In the above embodiment, the smoothing circuit 2 is an inverter smoothing circuit mounted on the inverter INV for driving the propulsion fan motor of the aircraft, but the smoothing circuit may be provided on various other inverters. In particular, it is effective to apply the smoothing circuit to inverters that require sufficient cooling performance while suppressing an increase in mass.

[0079] Other configurations can also be modified in various ways without departing from the spirit of the present invention. [Explanation of symbols]

[0080] INV Inverter 1 Rectifier circuit 2. Smoothing circuit for inverter (smoothing circuit) 21 parallel plate 21c Mounting area 22 Capacitor 221 Terminal 23 Thermal Conductive Sheet 231, 231x, 231y, 231z Sheet pieces 3. Reverse conversion circuit 31 Semiconductor Module 4. Chassis 41 Bottom

Claims

1. A parallel plate; A plurality of capacitors arranged in a matrix and mounted on the parallel plate; a thermally conductive sheet interposed between the parallel plate and a housing in a region overlapping a mounting region of the plurality of capacitors as viewed along a normal direction of the parallel plate; Equipped with The plurality of capacitors are arranged in row and column directions such that adjacent terminals of adjacent capacitors have the same polarity. A smoothing circuit for an inverter comprising:

2. 2. The inverter smoothing circuit according to claim 1, The thermally conductive sheet is The sheet is configured to include a plurality of sheet pieces having different thermal conductivities, A sheet piece having a relatively high thermal conductivity is disposed in an area where the amount of heat generated is relatively large. A smoothing circuit for an inverter comprising:

3. 3. The inverter smoothing circuit according to claim 1, a sheet piece having a relatively high thermal conductivity is disposed in a region adjacent to a connection portion where the parallel plate and the semiconductor module are connected; A smoothing circuit for an inverter comprising:

4. 4. A smoothing circuit for an inverter according to claim 1, the plurality of capacitors are of the same type; A sheet piece having a relatively high thermal conductivity is disposed in an area corresponding to an area in which a capacitor surrounded by other capacitors is mounted. A smoothing circuit for an inverter comprising:

5. 5. A smoothing circuit for an inverter according to claim 1, The thermal conductivity of each of the plurality of sheet pieces is defined based on the amount of heat generated in the region in which the sheet piece is disposed. A smoothing circuit for an inverter comprising:

6. 6. The inverter smoothing circuit according to claim 1, An inverter for an aircraft, comprising:

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