JP2018160995A - Power converter - Google Patents

Abstract

The present specification provides a power converter that reduces stress generated in a bus bar connecting a capacitor and a semiconductor module. A power converter includes a laminated unit, a capacitor, and a positive bus bar. The positive electrode bus bar 31 is a conductor that electrically connects the capacitor and the terminal 22 of each semiconductor module. The positive electrode bus bar 31 is connected to a capacitor and extends in parallel with the XY plane, and a plurality of branch portions 31b extending from the edge of the base plate 31a on the stacked unit side and arranged in the X direction. And a plurality of tip portions 31 c that extend in the Z direction from the tips of the respective branch portions 31 b and extend toward the terminal 22, and whose tips are connected to the terminal 22. The rigidity of the branch part 31b is lower than the rigidity of the base plate 31a and lower than the rigidity of the tip part 31c. By reducing the rigidity of the branch part 31b, the stress generated in the branch part 31b is relaxed. [Selection] Figure 5

Description

  The technology disclosed in this specification relates to a power conversion device that is mounted on a vehicle and converts power supply power to drive power of a motor for traveling.

  A power conversion device that converts power supply power to drive power for a motor for traveling often includes a plurality of semiconductor modules that contain semiconductor elements for power conversion. The semiconductor element is typically a switching element used in a voltage converter circuit or an inverter circuit. The semiconductor module through which the driving power of the running motor flows generates a large amount of heat. For example, Patent Document 1 discloses a structure for effectively cooling a plurality of semiconductor modules. The power conversion device of Patent Literature 1 employs a structure in which a plurality of semiconductor modules and a plurality of coolers are stacked. Hereinafter, for convenience of description, a device in which a plurality of semiconductor modules and a plurality of coolers are stacked is referred to as a stacked unit.

  On the other hand, the power converter includes a capacitor that smoothes the power supplied from the DC power supply. Since the smoothing capacitor is inserted before the inverter circuit, the capacitor and the plurality of semiconductor elements of the inverter circuit are electrically connected. That is, the terminals of the plurality of semiconductor modules of the stacked unit and the capacitors are electrically connected.

  In the power conversion device disclosed in Patent Document 1, the capacitor having an elongated shape is arranged adjacent to the multilayer unit with the longitudinal direction thereof coinciding with the stacking direction of the multilayer unit. The capacitor is electrically connected to each terminal of the plurality of semiconductor modules in the stacked unit by a bus bar. The “bus bar” is an elongated metal plate (or metal bar) for transmitting a large amount of power with low loss.

  Hereinafter, for convenience of explanation, an orthogonal XYZ coordinate system is defined in which the stacking direction of the semiconductor module and the cooler in the stacking unit housed in the case is the X direction. The direction in which the multilayer unit and the capacitor are arranged is the Y direction. When the orthogonal XYZ coordinate system is used, the relationship among the capacitor, the multilayer unit, and the bus bar of the power conversion device of Patent Document 1 is as follows. The multilayer unit and the capacitor are arranged in the Y direction. The terminals of the semiconductor module extend in the Z direction. The bus bar is made of a single continuous plate material. For convenience of explanation, the bus bar will be described by dividing it into a base plate, a plurality of branch portions, and a plurality of tip portions. The base plate is a portion that is connected to the capacitor and extends parallel to the XY plane. The plurality of branch portions extend from the edge of the base plate stacking unit and are arranged in the X direction. Each of the plurality of tip portions extends in the Z direction from the tip of each branch portion and extends toward the terminal of the semiconductor module, and the tip is connected to the terminal of the semiconductor module.

JP2015-154558A

  By the way, since the power converter which supplies drive electric power to the motor for driving | running | working is mounted in a vehicle, it receives a vibration during driving | running | working. Furthermore, for example, the power converter may be supported on a housing that houses the motor. In this case, the motor is also subjected to vibration, and thus the power converter is subjected to considerable vibration.

  On the other hand, the capacitor and the multilayer unit are individually fixed to the case of the power converter. The bus bar connects the capacitor and the multilayer unit. When the capacitor and the multilayer unit vibrate individually, the bus bar is deformed and strain (stress) is generated. As described above, in the bus bar, the base plate is connected to the capacitor, each of the plurality of tip portions is connected to the terminal of each semiconductor module, and the branch portion is connected between the edge and the tip portion of the base plate. Structure. The distortion (stress) of the bus bar concentrates on the branch part, and the branch part may be damaged. The present specification provides a technique for relieving the stress generated in the branch portion of the bus bar for the power converter having the bus bar described above.

  The power converter disclosed in this specification includes a capacitor, a multilayer unit, and a bus bar as described above. The capacitor, the multilayer unit, and the bus bar are accommodated in a case of the power conversion device. The stacked unit is a device in which a plurality of semiconductor modules and a plurality of coolers are stacked. The capacitors are arranged in the stacked unit in a direction crossing the stacking direction of the plurality of semiconductor modules and the plurality of coolers. The bus bar is a conductor that connects the capacitor and the terminal of each semiconductor module. As described above, for convenience of explanation, an orthogonal coordinate system is defined in which the stacking direction of the plurality of semiconductor modules and the plurality of coolers is the X direction, and the alignment direction of the stacking unit and the capacitor is the Y direction. The terminals of each semiconductor module extend in the Z direction. The bus bar is made of a single continuous plate. For convenience of explanation, the bus bar will be described as being divided into a base plate, a plurality of branches, and a plurality of tips. The base plate is connected to the capacitor and extends parallel to the XY plane between the capacitor and the multilayer unit. The plurality of branch portions extend from the edge of the base plate on the laminated unit side and are arranged in the X direction. Each of the plurality of tip portions extends in the Z direction from the tip of each branch portion and extends toward the terminal of the semiconductor module, and the tip is connected to the terminal. In the power conversion device disclosed in this specification, the rigidity of the branch portion is lower than the rigidity of the base plate and lower than the rigidity of the tip portion. By reducing the rigidity of the branch part, the stress generated in the branch part can be suppressed. Details and further improvements of the technology disclosed in this specification will be described in the following “DETAILED DESCRIPTION”.

It is a perspective view of the engine compartment of the hybrid vehicle containing the power converter device of an Example. It is a block diagram of the drive system of the hybrid vehicle including the power converter device of an Example. It is a top view which shows the component layout inside a power converter device. It is a perspective view of an assembly of a multilayer unit, a capacitor, and a bus bar. It is a perspective view of a bus bar. It is an expanded view of a bus bar. It is an expanded view of the bus bar of a 1st modification. It is an expanded view of the bus bar of a 2nd modification. It is case sectional drawing explaining the structure which suppresses the vibration of a bus bar. It is a case sectional view explaining another structure which controls vibration of a bus bar.

  A power converter according to an embodiment will be described with reference to the drawings. The power conversion apparatus 10 of the embodiment is mounted on a hybrid vehicle 100 that includes both two motors 92a and 92b for traveling and an engine 98. FIG. 1 shows the arrangement of devices in the engine compartment 90 of the hybrid vehicle 100. FIG. 1 is a perspective view of the engine compartment 90 as viewed obliquely from above. The engine compartment 90 of the hybrid vehicle 100 is located at the front of the vehicle. In the coordinate system in the figure, the X-axis indicates the front of the vehicle, the Z-axis indicates the upper side of the vehicle, and the Y-axis indicates the vehicle width direction (side of the vehicle). As will be described later, the X axis of the coordinate system corresponds to the stacking direction of the semiconductor module and the cooler in the case of the power conversion device 10. The Y direction corresponds to the direction in which the stacked body (stacked unit) of the semiconductor module and the cooler and the capacitor are arranged. The Z axis corresponds to the extending direction of the terminals of the semiconductor module.

  In the engine compartment 90, an engine 98, a power converter 10, a transaxle 91, and the like are arranged. Various other devices are arranged in the engine compartment 90, but the description thereof is omitted. In FIG. 1, the transaxle 91, the engine 98, and the like are schematically illustrated.

  The transaxle 91 is a device in which two motors 92 a and 92 b for traveling, a power distribution mechanism 93 and a differential gear 94 are combined. The power distribution mechanism 93 is a gear set that combines / distributes the output torque of the engine 98 and the output torque of the motors 92a and 92b. When high torque is required, the power distribution mechanism 93 combines the output torque of the engine 98 and the output torque of the motors 92a and 92b and transmits the combined torque to the differential gear 94. Further, the power distribution mechanism 93 divides the output torque of the engine 98 according to the situation and transmits it to the differential gear 94 and the one motor 92a. In that case, the hybrid vehicle 100 generates electric power with the motor 92a while traveling with engine torque. Since the transaxle 91 includes two motors 92a and 92b for traveling, the casing may be called a motor housing.

  The engine 98 and the transaxle 91 are connected so as to be adjacent in the vehicle width direction. The engine 98 and the transaxle 91 are suspended by two side members 97 that secure the structural strength of the vehicle. In FIG. 1, one side member is not visible.

  The power conversion apparatus 10 is a device that supplies driving power to the two motors 92a and 92b. More specifically, the power conversion device 10 boosts the power of a high-voltage battery (not shown), converts it to alternating current, and supplies it to the motors 92a and 92b. Further, the power conversion device 10 may convert AC power generated by the motor 92a or 92b into DC power, and may further step down the voltage. The high voltage battery is charged by the stepped down power.

  The power conversion device 10 is supported with a gap between the upper surface of the transaxle 91. The power converter 10 has a front side supported by a front bracket 96 and a rear side supported by a rear bracket 95.

  The reason why the power converter 10 is arranged above the transaxle 91 is to obtain the following two advantages. One is that the power cable for supplying power from the power converter 10 to the motors 92a and 92b can be shortened. The other is to protect the power conversion device 10 against a forward collision. The casing of the transaxle 91 is high in strength and large in size. Therefore, the space above the transaxle 91 is relatively safe against collisions.

  However, the device supported on the upper part of the transaxle 91 includes the vibrations of the motors 92a and 92b built in the transaxle 91 and the engine 98 connected to the transaxle 91 in addition to the running vibration of the vehicle. Vibration is applied. In order to reduce vibration transmitted to the power conversion device 10, vibration-proof bushings are sandwiched between the front bracket 96 and the power conversion device 10 and between the rear bracket 95 and the power conversion device 10. Although the vibration-proof bushing is adopted, the vibration transmitted to the power converter 10 via the transaxle 91 cannot be completely suppressed. The power conversion device 10 has a structure that reduces stress generated in components housed in the case by vibration, particularly, a bus bar described later. The vibration resistant structure of the bus bar will be described later.

  Next, the power system of the hybrid vehicle 100 including the power conversion device 10 will be described. FIG. 2 shows a block diagram of a power system of the hybrid vehicle 100 including the power conversion device 10 of the embodiment. The power converter 10 is a device that converts DC power of the battery 81 into driving power for the motors 92a and 92b for traveling. Since hybrid vehicle 100 includes two traveling motors 92a and 92b, power converter 10 includes two sets of inverter circuits 13a and 13b.

  The power conversion apparatus 10 includes a voltage converter circuit 12 that boosts the voltage of the battery 81 and two sets of inverter circuits 13a and 13b that convert the boosted DC power into AC.

  The voltage converter circuit 12 boosts the voltage applied to one terminal and outputs it to the other terminal, and the voltage converter circuit 12 steps down the voltage applied to the other terminal and outputs it to one terminal. Can be done. Such a voltage converter circuit is called a bidirectional DC-DC converter circuit. For convenience of explanation, a terminal on the low voltage side (battery side) is hereinafter referred to as an input end 18, and a terminal on the high voltage side (inverter circuit side) is referred to as an output end 19. Further, the positive electrode and the negative electrode of the input end 18 are referred to as an input positive electrode end 18a and an input negative electrode end 18b, respectively. The positive electrode and the negative electrode of the output end 19 are referred to as an output positive electrode end 19a and an output negative electrode end 19b, respectively. The notations "input terminal 18" and "output terminal 19" are for convenience of explanation, and as described above, the voltage converter circuit 12 is a bidirectional DC-DC converter. In some cases, power flows from 19 to the input terminal 18.

  The voltage converter circuit 12 includes four transistors 6a, 6b, 7a, 7b, a reactor 4, a filter capacitor 3, and a diode connected in antiparallel to each transistor. The two transistors 6a and 7a are connected in series, and the remaining two transistors 6b and 7b are also connected in series. Hereinafter, a circuit in which two transistors are connected in series may be simply referred to as a “series connection circuit”. In the following, the high potential side transistors 6a and 6b of the series connection circuit may be referred to as upper arm transistors, and the low potential side transistors 7a and 7b may be referred to as lower arm transistors.

  The two sets of series connection circuits are connected in parallel. The high potential side of the two sets of series connection circuits is connected to the output positive end 19a, and the low potential side is connected to the output negative end 19b. One end of the reactor 4 is connected to the input positive terminal 18a, and the other end is connected to the middle points Qa and Qb of the two series connection circuits. The filter capacitor 3 is connected between the input positive terminal 18a and the input negative terminal 18b. The input negative electrode end 18b is directly connected to the output negative electrode end 19b.

  The four transistors 6a, 6b, 7a and 7b are driven by a drive circuit mounted on a circuit board (not shown). The drive circuit supplies an upper arm switching command signal for turning on and off at the same timing to the two upper arm transistors 6a and 6b. The drive circuit supplies a lower arm switching command signal for turning on and off at the same timing to the two lower arm transistors 7a and 7b. That is, the two upper arm transistors 6a and 6b are driven to perform the same operation at the same timing, and the two lower arm transistors 7a and 7b are also driven to perform the same operation at the same timing. Performing the same operation at the same timing is called parallel operation. By operating in parallel two sets of series connection circuits connected in parallel, the two sets of series connection circuits operate as if they were one series connection circuit, while reducing the load on each transistor. it can.

  In FIG. 2, a circuit within a broken rectangle indicated by reference numeral 8 a is realized by a semiconductor module 8 a described later. A circuit in the range of a broken-line rectangle indicated by reference numeral 8b is realized by a semiconductor module 8b described later. The semiconductor module is a package containing a series connection circuit of two transistors and a diode connected in antiparallel to each transistor. The semiconductor module 8a accommodates a series connection circuit of two transistors 6a and 7a and a diode connected in antiparallel to each transistor. The semiconductor module 8b accommodates a series connection circuit of two transistors 6b and 7b and a diode connected in antiparallel to each transistor.

  Next, the inverter circuits 13a and 13b will be outlined. In FIG. 2, illustration of specific circuit configurations of the inverter circuits 13a and 13b is omitted, and only the semiconductor modules 8c-8h (described later) are schematically represented by broken-line rectangles. Each of the semiconductor modules 8c-8h corresponds to one series connection circuit.

  The inverter circuit 13a includes three sets of a series connection circuit of two transistors. A diode is connected in antiparallel to each transistor. The semiconductor modules 8c, 8d, and 8e correspond to three sets of series connection circuits. Therefore, hereinafter, the inverter circuit 13a will be described using the semiconductor modules 8c-8e. The three semiconductor modules 8c-8e are connected in parallel. The high potential side and the low potential side of the three semiconductor modules 8c-8e are connected to the output positive end 19a and the output negative end 19b of the voltage converter circuit 12, respectively. AC is output from the midpoint of each semiconductor module.

  The inverter circuit 13b has the same configuration as the inverter circuit 13a. That is, the inverter circuit 13b includes three semiconductor modules 8f, 8g, and 8h, and each of the semiconductor modules 8f, 8g, and 8h corresponds to a series connection circuit. AC is output from the midpoint of each series connection circuit. The AC outputs of the inverter circuits 13a and 13b are supplied to the motors 92a and 92b. The smoothing capacitor 5 is connected between the output positive terminal 19a and the output negative terminal 19b of the voltage converter circuit 12. The semiconductor modules 8c-8h of the inverter circuits 13a, 13b have the same structure as the semiconductor modules 8a, 8b of the voltage converter circuit 12.

  A total of six semiconductor modules 8 c-8 h of the inverter circuits 13 a, 13 b and two semiconductor modules 8 a, 8 b of the voltage converter circuit 12 are connected in parallel with the smoothing capacitor 5. More specifically, the high-potential side and the low-potential side of the series connection circuit accommodated in a total of eight semiconductor modules 8a-8h are connected to the smoothing capacitor 5. A total of eight semiconductor modules 8a-8h and the smoothing capacitor 5 are connected by a metal member called a bus bar. Next, the hardware structure of the power conversion device 10 including the bus bar will be described.

  FIG. 3 is a plan view of the power conversion device 10. FIG. 3 is a plan view of the power conversion device 10 with the cover removed, and shows the layout of components housed in the case 40. In the case 40, a filter capacitor unit 103, a reactor unit 104, a multilayer unit 20, a smoothing capacitor unit 105, and the like are accommodated.

  A capacitor element corresponding to the filter capacitor 3 shown in FIG. 2 is accommodated in the filter capacitor unit 103. The reactor unit 104 accommodates a reactor device corresponding to the reactor 4 shown in FIG. A capacitor element corresponding to the smoothing capacitor 5 described with reference to FIG. Since a large current flows through the filter capacitor 3, the smoothing capacitor 5, and the reactor 4, the hardware corresponding to them has a large physique.

  A laminated unit 20 is disposed adjacent to the smoothing capacitor unit 105. The stacked unit 20 is a unit in which a plurality of semiconductor modules 8a-8h and a plurality of coolers 44 are stacked. In FIG. 3, only the rightmost two coolers are denoted by reference numeral 44, and the remaining coolers are omitted. Each of the semiconductor modules 8a-8h is a package containing a series connection circuit of two transistors and a diode connected in antiparallel to each transistor, as described above. The plurality of semiconductor modules 8a-8h and the plurality of coolers 44 are alternately stacked one by one. Each of the semiconductor modules 8a-8h includes a positive terminal 22 connected to the high potential side of the series connection circuit of transistors, a negative terminal 23 connected to the low potential side, and a midpoint terminal 24 connected to the midpoint. It has. In FIG. 3, only the semiconductor module 8a at the left end and the semiconductor module 8h at the right end are denoted by reference numerals 22, 23, and 24 indicating the positive terminal, the negative terminal, and the middle terminal, and the other semiconductor modules 8b-8g These symbols are omitted.

  For convenience of explanation, an orthogonal coordinate system is defined in which the stacking direction of the plurality of semiconductor modules 8a-8h and the plurality of coolers 44 is defined as the X axis and the alignment direction of the stacked unit 20 and the smoothing capacitor unit 105 is defined as the Y axis. The terminals 22, 23, 24 of the semiconductor modules 8a-8h extend in the Z direction.

  The stacked unit 20 is inserted between a support wall 43 provided in the case 40 and the two support pillars 45. Although not shown, a leaf spring is inserted between the support pillar 45 and the laminated unit 20, and the laminated unit 20 is supported by the case 40 while being pressed in the laminating direction by the leaf spring. ing. The pressure in the stacking direction increases the adhesion between the semiconductor modules 8a-8h and the cooler 44, and the cooling performance is improved. In addition, a refrigerant supply pipe 41 and a refrigerant discharge pipe 42 are connected to one end of the laminated unit 20, and these pipes penetrate the case 40. The refrigerant supplied from the refrigerant supply pipe 41 is distributed to each cooler 44. The refrigerant absorbs heat from the adjacent semiconductor modules 8a-8h while passing through the inside of each cooler 44. The refrigerant that has passed through the cooler 44 is discharged out of the power converter 10 through the refrigerant discharge pipe 42.

  As described with reference to the circuit diagram of FIG. 2, the high potential side (positive terminal 22) of all the semiconductor modules 8a-8h are connected to each other, and the low potential side (negative terminal 23) is connected to each other. . The smoothing capacitor 5 (smoothing capacitor unit 105) is connected in parallel between the high potential side (positive electrode terminal 22) and the low potential side (negative electrode terminal 23) of all the semiconductor modules 8a-8h. The positive terminals 22 of all the semiconductor modules 8 a to 8 h are connected to each other by the positive bus bar 31 and are connected to one electrode of the smoothing capacitor unit 105. The negative terminals 23 of all the semiconductor modules 8 a to 8 h are connected to each other by the negative bus bar 32 and to the other electrode of the smoothing capacitor unit 105. The bus bar means a metal plate (or metal bar) that transmits power with a small internal resistance.

  The semiconductor modules 8c-8h are used in an inverter circuit, and an alternating current is output from the midpoint terminal 24 thereof. The midpoint terminal 24 of the semiconductor module 8c-8h is connected to the output bus bar 33, and one end of the output bus bar 33 constitutes the output terminal 46 of the power converter 10.

  As described with reference to the circuit diagram of FIG. 2, the semiconductor modules 8 a and 8 b are connected in parallel and used in the voltage converter circuit 12. The positive terminals 22 of the semiconductor modules 8a and 8b are connected to each other by the positive bus bar 31 and are connected to one electrode of the smoothing capacitor unit 105 in the same manner as the other semiconductor modules 8c-8h. The negative terminals 23 of the semiconductor modules 8a and 8b are connected to each other by the negative bus bar 32 and connected to the other electrode of the smoothing capacitor unit 105 in the same manner as the other semiconductor modules 8c to 8h.

  The midpoint terminals 24 of the semiconductor modules 8 a and 8 b are connected to each other by a midpoint connection bus bar 34 and to one terminal of the reactor unit 104. Thus, the positive terminals 22, the negative terminals 23, and the midpoint terminals 24 of the semiconductor modules 8 a and 8 b are connected. The other terminal of the reactor unit 104 is connected to one electrode of the filter capacitor unit 103 by the bus bar 35. One end of the bus bar 35 constitutes an input end 47 (positive electrode end) of the power conversion device 10. A bus bar 36 is connected to the other electrode of the filter capacitor unit 103, and one end of the bus bar 36 constitutes an input end 47 (negative electrode end).

  The relationship among the smoothing capacitor unit 105, the multilayer unit 20, and the positive electrode bus bar 31 will be described with reference to FIGS. 4 is a perspective view in which only the smoothing capacitor unit 105, the multilayer unit 20, and the positive electrode bus bar 31 are taken out from the power conversion device 10. FIG. In FIG. 4, the negative electrode bus bar 32 is not shown. FIG. 5 is a perspective view of a portion of the positive electrode bus bar 31 exposed from the smoothing capacitor unit 105. The positive electrode bus bar 31 is formed from a single metal plate. FIG. 6 is a development view of the positive electrode bus bar 31 in a portion exposed from the smoothing capacitor unit 105. In FIG. 4, the semiconductor modules 8 a to 8 h are denoted as the semiconductor module 8. In FIG. 4, reference numerals 8 and 44 are attached only to the leftmost semiconductor module and the cooler, and reference numerals are omitted for the other semiconductor modules and the cooler. Further, only the semiconductor module 8 at the left end is provided with reference numerals 22, 23, and 24 indicating the respective terminals, and the reference numerals are omitted for the terminals of the other semiconductor modules. 2 and the subsequent drawings, the X direction of the coordinate system indicates the stacking direction of the semiconductor modules 8a-8h and the cooler 44.

  For convenience of explanation, the positive electrode bus bar 31 is divided into a base plate 31a, a plurality of branch portions 31b, and a plurality of tip portions 31c. In FIG. 4, the branch part 31b is hidden and cannot be seen. The base plate 31a is a plate member that extends from the smoothing capacitor unit 105 toward the multilayer unit 20 and extends in the XY plane. The plurality of branch portions 31b extend from the end of the base plate 31a close to the stacked unit 20. The plurality of branch portions 31b are arranged in the X direction. 5 and FIG. 6, the broken line 31d indicates “the end of the base plate 31a on the side close to the laminated unit 20”. Each of the plurality of branch portions 31b has a tip portion 31c. The distal end portion 31 c extends from the distal end of the branch portion 31 b so as to be bent at a right angle in the Z direction of the coordinate system in the drawing, and extends toward the positive electrode terminal 22 of the semiconductor module 8. Each of the plurality of tip portions 31 c is joined to each positive electrode terminal 22 of the plurality of semiconductor modules 8. The tip 31c and the positive terminal 22 are joined by solder.

  The branch part 31b is a part that connects the base plate 31a and the tip part 31c. The branch part 31b has a rigidity lower than that of the base plate 31a and lower than that of the tip part 31c. The rigidity here means bending rigidity in the Z-axis direction, torsional rigidity around the X axis, and torsional rigidity around the Y axis. As shown in FIG. 6, in the positive electrode bus bar 31, the width of the branch portion 31b in the developed view is small, and thereby the cross-sectional secondary moment related to the bending rigidity and the cross-sectional area related to the torsional rigidity are reduced. Since the secondary moment and the cross-sectional area are small, both the bending rigidity and the torsional rigidity are reduced.

  In the positive electrode bus bar 31, the base plate 31 a is restrained by the smoothing capacitor unit 105, and the plurality of tip portions 31 c are restrained by the laminated unit 20. The power conversion apparatus 10 is fixed on a transaxle 91 that houses motors 92a and 92b, and receives vibrations in various modes. When the smoothing capacitor unit 105 and the multilayer unit 20 vibrate, the positive electrode bus bar 31 constrained by both is also deformed in various modes. Stress is generated at the deformed part. In particular, the stress tends to concentrate on the branch part 31b connecting the base plate 31a and the tip part 31c. In the power conversion device 10 of the embodiment, the stress generated in the branch portion 31b is suppressed by suppressing the rigidity of the branch portion 31b of the positive bus bar 31 to be low.

  A modification of the positive bus bar will be described with reference to FIGS. FIG. 7 is a development view of the bus bar 131 of the first modification. The positive bus bar 131 has an end in the positive direction of the X-axis located inside the case 40 and near the center of the case (see FIG. 3). The vicinity of the center of the case corresponds to the antinode of the positive bus bar 131 in the Z-axis direction. In the positive electrode bus bar 131 of the modification, the branch portions 131b1, 131b2, 131b3 close to the end in the positive direction of the X axis are longer in this order. By increasing the length of the branch portions 131b1, 131b2, 131b3 close to the vibration antinode, the sectional moment of inertia is reduced, and the bending rigidity in the Z-axis direction is further reduced. In the positive electrode bus bar 131 of the modified example, the bending rigidity of the branch portions 131b1, 131b2, 131b3 corresponding to the antinodes of vibration in the Z-axis direction is made smaller than that of the branch portions 131b at other positions, and stress concentration on the branch portions is reduced. Relieve effectively.

  FIG. 8 is a development view of the positive electrode bus bar 231 of the second modified example. In the positive electrode bus bar 231, a through hole 231e is provided in the vicinity of the boundary between each branch portion 231b and the base plate 31a. By providing the through-hole 231e, the cross-sectional secondary moment and the cross-sectional area of the branch portion 231b are reduced. As a result, the bending rigidity and torsional rigidity of the branch portion 231b are reduced.

  In the above embodiment, the positive electrode bus bar has been described in detail. With respect to the negative electrode bus bar, the rigidity of the branch portion is low due to the same structure.

  Next, a technique for suppressing vibration of the bus bar (stress generated in the bus bar) by utilizing the components in the case of the power conversion device will be described. FIG. 9 is a cross-sectional view of the case 140 of the power conversion device 10a. In FIG. 9, the case 140 is hatched to show a cross section, but the other parts (reactor unit 104 and laminated unit 20) are not shown to have a cross section. In this example, the case 140 is divided into an upper case 141 and a lower case 142, and an inner plate 140c divides the internal space of the case 140 into an upper space and a lower space. Reactor unit 104, laminated unit 20, smoothing capacitor unit 105, and filter capacitor unit 103 (not shown in FIG. 9) are arranged in the upper space. Although not shown, the positive electrode bus bar 31 and the negative electrode bus bar are also accommodated in the upper space. In the lower space, a voltage converter unit or the like not described is accommodated.

  In the power converter 10a, the reactor unit 104 is fastened to the top plate 141a of the upper case 141 at the fastening point 104c, and is fastened to the middle plate 140c at the two fastening points 104a and 104b. The top plate 141a and the middle plate 140c of the case 140 that accommodates the reactor unit 104, the multilayer unit 20, the smoothing capacitor unit 105, and the filter capacitor unit 103 (not shown) are fastened to each other via the reactor unit 104. The rigidity of the case 140 (upper case 141) is increased, and the vibration of the positive electrode bus bar 31 (and the negative electrode bus bar) is suppressed.

  FIG. 10 is a cross-sectional view of the case 240 of the power conversion device 10b. In FIG. 10, the case 240 is hatched to show a cross section, but the other parts (smoothing capacitor unit 105 and multilayer unit 20) are not shown to have a cross section. In this example, the case 240 is divided into an upper case 241 and a lower case 242, and an inner plate 240c divides the internal space of the case 240 into an upper space and a lower space. The smoothing capacitor unit 105, the multilayer unit 20, the reactor unit 104 (not shown in FIG. 10), and the filter capacitor unit 103 (not shown in FIG. 10) are arranged in the upper space. Although not shown, the positive electrode bus bar 31 and the negative electrode bus bar are also accommodated in the upper space. In the lower space, a voltage converter unit or the like not described is accommodated.

  In the power conversion device 10b, protrusions 105a and 105b are provided above and below the smoothing capacitor unit 105. The lower protrusion 105a is fitted in a groove provided in the middle plate 240c, and the upper protrusion 105b is fitted in a groove provided in the top plate 241a of the upper case 241. The top plate 241a and the middle plate 240c of the case 240 housing the reactor unit 104 (not shown), the multilayer unit 20, the smoothing capacitor unit 105, and the filter capacitor unit 103 (not shown) are mutually connected via the smoothing capacitor unit 105. By being connected, the rigidity of the case 240 (upper case 241) is increased, and the vibration of the positive electrode bus bar 31 (and the negative electrode bus bar) is suppressed.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

3: Filter capacitor 4: Reactor 5: Smoothing capacitors 6a, 6b, 7a, 7b: Transistors 8a-8h: Semiconductor modules 10, 10a, 10b: Power converter 12: Voltage converter circuits 13a, 13b: Inverter circuit 20: Multilayer unit 22: positive electrode terminal 23: negative electrode terminal 24: middle point terminals 31, 131, 231: positive electrode bus bar 31a: base plates 31b, 131b, 131b1, 131b2, 131b3, 231b: branch 31c: tip 32: negative electrode bus bars 40, 140 240: Case 41: Refrigerant supply pipe 42: Refrigerant discharge pipe 43: Support wall 44: Cooler 45: Support column 81: Battery 90: Engine compartment 91: Transaxle 92a, 92b: Motor 93: Power distribution mechanism 94: Differential Gear 95: Rear bracket 96: Front bracket 97: Side member 98: Engine 100: Hybrid vehicle 103: Filter capacitor unit 104: Reactor unit 104a, 104b, 104c: Fastening location 105: Smoothing capacitor unit 105a, 105b: Projection 140c, 240c: Middle plates 141, 241: Upper case 141a, 241a: Top plate 142, 242: Lower case 231e: Through hole

Claims (1)

It is a power conversion device that is mounted on a vehicle and converts power supply power into drive power for a motor for traveling,
Housed in the case of the power converter, a stacked unit in which a plurality of semiconductor modules and a plurality of coolers are stacked,
In the case, a capacitor aligned with the stacked unit in a direction intersecting the stacking direction of the plurality of semiconductor modules and the plurality of coolers,
A bus bar electrically connecting the terminals of each of the semiconductor modules and the capacitor;
When defining an orthogonal coordinate system in which the stacking direction is the X direction and the stacking unit and the capacitor are arranged in the Y direction,
The terminals of the semiconductor module extend in the Z direction;
The bus bar is connected to the capacitor and extends in parallel with the XY plane, and a plurality of branches extending from the edge of the base plate on the laminated unit side and arranged in the X direction, respectively. A distal end portion extending in the Z direction from the distal end of the branch portion and extending toward the terminal, the distal end being connected to the terminal;
With
The power conversion device, wherein the branch portion has a rigidity lower than that of the base plate and lower than that of the distal end portion.

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