JP2015154558A - Power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion device capable of effectively preventing stress concentration in the connection part between a bus bar and a terminal.SOLUTION: A power conversion device 10 comprises one or more semiconductor modules 30, and a capacitor 14 electrically connected to the one or more semiconductor modules. The capacitor 14 includes a positive electrode bus bar 46 and a negative electrode bus bar 48 each of which has a different path length. Each semiconductor module 30 includes a positive electrode terminal 32 connected to the positive electrode bus bar 46 and a negative electrode terminal 34 connected to the negative electrode bus bar 48. The negative electrode terminal 34 connected to the negative electrode bus bar 48 having a long path length has a larger cross-sectional area than the positive electrode terminal 32.

Description

  The present invention relates to a power conversion device including one or more semiconductor modules and a capacitor, and more particularly to electrical connection between a semiconductor module and a capacitor.

  2. Description of the Related Art A power conversion circuit that converts DC power to AC power and, conversely, converts AC power to DC power, a so-called inverter is known. Also known is a power conversion circuit that boosts or steps down a DC voltage, a so-called step-up or step-down converter. There is a case where one or more power conversion circuits that convert power characteristics (AC / DC, voltage, etc.) are combined to form one power conversion device.

  As a usage example of the power conversion device, a vehicle including a rotating electric machine, for example, a hybrid vehicle or an electric vehicle is known. In such a vehicle, a rotating electrical machine is used as a drive source (electric motor), or a generator that generates electric power by driving a rotating shaft by the inertia of the vehicle. An inverter is used to drive the rotating electrical machine with a DC power source such as a secondary battery mounted on a vehicle and to charge the secondary battery with electric power regenerated by the rotating electrical machine. In some cases, a boost converter is provided to boost the terminal voltage of the secondary battery and supply it to the motor. Furthermore, a hybrid vehicle including two rotating electric machines is also known, and in this case, an inverter is used corresponding to each of the two electric motors.

  In such a power converter, one or more semiconductor modules, capacitors, reactors, and the like are provided. Each semiconductor module and the capacitor are electrically connected by connecting a terminal protruding from each semiconductor module and a bus bar protruding from the capacitor. Techniques relating to such electrical connection between a semiconductor module and a capacitor are disclosed in Patent Documents 1 to 3 and the like.

JP 2006-295997 A JP 2011-151992 A JP 2011-109767 A

  By the way, two types of bus bars, that is, a positive bus bar and a negative bus bar extend from the capacitor, but due to the layout, one of the two types of bus bars has a longer path length than the other bus bar. Become. As a result, the rigidity of one bus bar is lower than that of the other bus bar. When external force such as vibration is applied, stress concentrates on one of the bus bars with poor rigidity, in particular, at the tip of one bus bar with the least rigidity (that is, the connection with the terminal of the corresponding pole). was there.

  Particularly, in recent years, it has been proposed to install a power conversion device on a transaxle case from the viewpoint of effective use of space. The transaxle is a unit in which a rotating electric machine and a gear train connected to these output shafts are unitized. In this case, the vibration generated by driving the transaxle is also transmitted to the power converter, and the capacitor and the semiconductor module vibrate. As a result, the problem of stress concentration at the connection portion between one bus bar and the terminal has become more serious.

  Therefore, an object of the present invention is to provide a power conversion device that can effectively prevent stress concentration at a connection portion between a bus bar and a terminal.

  The power conversion device of the present invention is a power conversion device including one or more semiconductor modules and a capacitor electrically connected to the one or more semiconductor modules, and the capacitors have different path lengths. Each semiconductor module has a positive electrode terminal connected to the positive electrode bus bar and a negative electrode terminal connected to the negative electrode bus bar. Of the positive electrode terminal and the negative electrode terminal, each of the semiconductor modules has the path length. The terminal connected to the long bus bar has a larger cross-sectional area than the terminal connected to the bus bar having a short path length.

  In a preferred aspect, of the positive terminal and the negative terminal, a terminal connected to the bus bar having a long path length is wider than a terminal connected to the bus bar having a short path length. In another preferred embodiment, the positive electrode terminal and the negative electrode terminal are arranged side by side and extend in a direction orthogonal to the arrangement direction, and the positive electrode bus bar and the negative electrode bus bar are the positive electrode terminal and the negative electrode terminal. It extends in the direction of arrangement of and is connected to the terminal of the corresponding pole. In another preferred aspect, a plurality of the semiconductor modules are stacked, and the capacitor includes a plurality of positive electrode bus bars and a plurality of negative electrode bus bars connected to positive and negative terminals extending from the plurality of semiconductor modules. In addition, the plurality of bus bars having the same polarity are formed by bending one conductor plate.

  According to the present invention, since the cross-sectional area of the terminal connected to the bus bar having a long path length is increased, the rigidity of the entire connection path of the pole can be increased. As a result, since the rigidity of the connection path of the positive electrode and the rigidity of the connection path of the negative electrode are made uniform, stress concentration at the connection portion can be effectively prevented.

It is a circuit block diagram of the control system containing the power converter device which is embodiment of this invention. It is a perspective view which shows the one part external appearance of a power converter device. It is sectional drawing orthogonal to the lamination direction of a semiconductor module. It is a figure which shows the positive electrode bus bar before bending. It is a figure which shows the negative electrode bus bar before bending. It is a figure which shows the positive electrode bus bar and negative electrode bus bar after bending.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit configuration diagram of a control system including a power conversion device 10 of the present embodiment. FIG. 1 is a diagram showing a control system for driving first and second rotating electric machines 72 and 74 as driving motors for a hybrid vehicle. The two rotating electric machines 72 and 74 are rotationally driven by the electric power from the secondary battery 70, and the electric power generated by the rotating electric machines 72 and 74 is charged in the secondary battery 70. The power converter 10 performs this driving and charging. The power conversion device 10 converts the DC power of the booster converter 12 that boosts the voltage of the secondary battery 70 and the DC power of the secondary battery 70 into three-phase AC power, and converts the AC power generated by the rotating electrical machines 72 and 74 into DC power. And inverters 16 and 18 for converting to. A first inverter 16 is provided for the first rotating electrical machine 72, and a second inverter 18 is provided for the second rotating electricity 74. Boost converter 12 is a power converter or circuit that converts a characteristic value of power called voltage, and inverters 16 and 18 are power converters or circuits that convert a characteristic of power such as alternating current and direct current. The two rotating electric machines 72 and 74 of this embodiment both function as an electric motor and a generator, but may be rotating electric machines that function as either one of an electric motor or an electric generator.

  Boost converter 12 includes a semiconductor module 30 including a reactor 20 and a power transistor such as an IGBT. The semiconductor module 30 has a positive terminal 32 connected to the positive terminals of the inverters 16 and 18, a negative terminal 34 connected to the negative terminals of the inverters 16 and 18, and an output terminal 36 connected to the reactor 20.

  The first inverter 16 and the second inverter 18 have substantially the same configuration. That is, the first and second inverters 16 and 18 have three semiconductor modules 30 having the same structure including power transistors such as IGBTs. Each of the three semiconductor modules 30 corresponds to each phase of three-phase AC power supplied to the rotating electrical machines 72 and 74. The semiconductor module 30 has a positive terminal 32, a negative terminal 34, and an output terminal 36. The positive terminals 32 of the three semiconductor modules 30 are connected to each other by a bus 38, and further connected to the positive terminal 32 of the boost converter 12 by the bus 38. On the other hand, the negative terminals 34 of the three semiconductor modules 30 are connected by a bus 40, and further connected by a bus 40 to the negative terminal 34 of the boost converter 12. The three output terminals 36 are connected to three-phase power lines that supply power to the coils of the rotating electrical machines 72 and 74, respectively.

  A smoothing capacitor 14 is disposed between the bus bar 38 and the bus bar 40. Furthermore, the power conversion device 10 includes a control device 49 that controls operations of the boost converter 12 and the first and second inverters 16 and 18. The control device 49 controls the operation of the boost converter 12, the first and second inverters 16, 18 by controlling the power transistor of each semiconductor module 30.

  FIG. 2 is a perspective view showing an overview of a part of the power conversion apparatus 10. FIG. 3 is a view showing a cross section orthogonal to the stacking direction of the semiconductor modules 30.

  As shown in FIG. 2, the semiconductor modules 30 are stacked in the thickness direction. Preferably, the semiconductor modules 30 are stacked at an equal pitch. In the present embodiment, three semiconductor modules 30 belonging to the first inverter 16 and three semiconductor modules 30 belonging to the second inverter 18 are arranged on both sides in the stacking direction, and one of them belongs to the boost converter 12 therebetween. The semiconductor module 30 is arranged. The semiconductor module 30 belonging to the first and second inverters 16 and 18 is a set of three corresponding to the number of phases of the three-phase AC power, but for the boost converter 12, the number of semiconductor modules 30 is one. It is not limited. The number of semiconductor modules 30 is determined by the allowable current value of elements such as transistors belonging to the semiconductor module 30. By increasing the number of semiconductor modules 30, the current per one can be reduced, and the number of modules is determined based on usage conditions.

  The components of the semiconductor module 30 such as an IGBT are housed in a case and modularized. The appearance of the semiconductor module 30 is common. From the upper surface of each semiconductor module 30, a positive terminal 32, a negative terminal 34, and an output terminal 36 protrude in order from the back side (capacitor 14 side). Each terminal 32, 34, 36 extends in a direction orthogonal to the terminal arrangement direction and the stacking direction. The three terminals 32, 34, and 36 are all arranged side by side in the same plane orthogonal to the stacking direction. Therefore, when the semiconductor modules 30 are stacked at an equal pitch, the terminals 32, 34, and 36 are also arranged at an equal pitch.

  The power conversion device 10 is further provided with a cooler that cools each semiconductor module 30. The cooler includes a cooling plate 22 and liquid feeding pipes 23 and 24 arranged so as to sandwich each semiconductor module 30. The cooling plate 22 is hollow, and the internal space communicates with the liquid feeding pipes 23 and 24. The cooling liquid sent from one liquid supply pipe 23 is distributed to a plurality of cooling plates 22, flows through each cooling plate 22, and reaches the other liquid supply pipe 24. The coolant flowing through the cooling plate 22 takes heat from the semiconductor modules 30, and these semiconductor modules 30 are cooled. The cooling liquid collected in the liquid feeding pipe 24 is sent to a radiator (not shown) through the liquid feeding pipe 24 and is sent again to the cooling plate 22 through the liquid feeding pipe 23 after heat radiation.

  A capacitor 14 is disposed on the side of the semiconductor module 30. A plurality of positive bus bars 46 connected to the positive terminal 32 of the semiconductor module 30 and a plurality of negative bus bars 48 connected to the negative terminal 34 protrude from the end face of the capacitor 14. The plurality of positive electrode bus bars 46 and the plurality of negative electrode bus bars 48 are integrated with the capacitor 14. Each of the positive electrode bus bar 46 and the negative electrode bus bar 48 is a bus bar connected to the terminal of the corresponding electrode, and is provided in the same number as the semiconductor modules 30.

  The positive electrode bus bar 46 is fixed to and supported by the upper surface of the fixed base 26. The negative electrode bus bar 48 is fixed to and supported by the lower surface of the fixed base 26. The positive bus bar 46 is connected to the positive terminal inside the capacitor 14, and the negative bus bar 48 is connected to the negative terminal inside the capacitor 14. The positive terminal and the negative terminal of the capacitor 14 are connected to the capacitor 14 housed in the capacitor case 14a inside the case.

  Here, as is apparent from FIG. 2, the plurality of positive electrode bus bars 46 are arranged at intervals in the stacking direction of the semiconductor modules 30, and each positive electrode bus bar 46 extends in the terminal arrangement direction. In other words, each positive electrode bus bar 46 extends in a direction orthogonal to the positive electrode terminal 32 and is connected to the positive electrode terminal 32 (attachment, fastening, etc.) in a state of forming approximately 90 degrees with the positive electrode terminal 32.

  The plurality of positive electrode bus bars 46 are configured by forming cuts and bending in one conductor plate. FIG. 4 is a diagram illustrating an example of the positive electrode conductor plate 50 constituting the plurality of positive electrode bus bars 46. The positive conductor plate 50 is a conductor plate that is connected to the positive terminal of the capacitor 14 and is accommodated in the capacitor case 14 a together with the capacitor 14. A plurality of cuts are formed at one end of the positive electrode conductor plate 50, and a plurality of cantilevered positive electrode bus bars 46 are formed by the cuts. The positive electrode bus bar 46 extends so as to extend from one side 50a of the positive electrode conductor plate 50, and is bent approximately 90 degrees along a broken line 46a extending in the extending direction. As a result, each positive electrode bus bar 46 is located in substantially the same plane as the positive electrode terminal 32 of the semiconductor module 30. By connecting the tip of the positive bus bar 46 and the tip of the positive terminal 32 to each other, the positive terminal 32 of each semiconductor module 30 and the positive terminal 42 of the capacitor 14 are electrically connected.

  Here, as a matter of course, the arrangement pitch of the plurality of positive electrode bus bars 46 is the same as the arrangement pitch of the positive electrode terminals 32 (stacking pitch of the semiconductor modules 30). Further, in the stage before bending, the plurality of positive electrode bus bars 46 are in a plane parallel to the stacking direction of the semiconductor modules 30. Therefore, the widths of the plurality of positive electrode bus bars 46 are limited to values that do not exceed the stacking pitch of the semiconductor modules 30.

  Similarly to the positive electrode bus bar 46, the plurality of negative electrode bus bars 48 are configured by forming a cut in a single conductor plate and bending it. However, in the present embodiment, the negative terminal 34 of the semiconductor module 30 is farther from the capacitor 14 than the positive terminal 32. Therefore, the negative electrode bus bar 48 is longer than the positive electrode bus bar 46. Further, the negative electrode bus bar 48 is slightly different from the positive electrode bus bar 46 in the bending manner in order to avoid interference with the positive electrode bus bar 46 and the positive electrode terminal 32. This will be described with reference to FIGS. FIG. 5 is a view showing an example of the negative electrode conductor plate 52 constituting the plurality of negative electrode bus bars 48. FIG. 6 is a view when the bent positive electrode bus bar 46 and negative electrode bus bar 48 are overlapped. Similar to the positive electrode bus bar 46, the negative electrode bus bar 48 extends so as to extend from one side 52 a of the negative electrode conductor plate 52. The negative electrode bus bar 48 extending from the capacitor 14 is bent approximately 90 degrees along the broken line 48a at a position beyond the positive electrode terminal 32, and further bent along a plurality of bent lines 48b. Thereby, as shown in FIG. 6, the negative electrode bus bar 48 is located in the same plane as the positive electrode terminal 32 and the negative electrode terminal 34. Then, by connecting the tip of the negative bus bar 48 and the tip of the negative terminal 34 to each other, the negative terminal 34 of each semiconductor module 30 and the negative terminal 44 of the capacitor 14 are electrically connected. The width of the negative electrode bus bar 48 is also limited to a value that does not exceed the stacking pitch of the semiconductor modules 30, as with the positive electrode bus bar 46.

  Note that the shapes of the positive electrode bus bar 46 and the negative electrode bus bar 48 described here are merely examples, and they extend from the capacitor 14 in the terminal arrangement direction of the semiconductor module 30 and are connected to the corresponding electrode terminals 32 and 34. For example, the shapes of the bus bars 46 and 48 may be changed as appropriate. However, in any case, the widths of the positive electrode bus bar 46 and the negative electrode bus bar 48 are always limited to be equal to or less than the stacking pitch of the semiconductor modules 30.

  Incidentally, as is apparent from the above description, in this embodiment, since the negative electrode terminal 34 of the semiconductor module 30 is farther from the capacitor 14 than the positive electrode terminal 32, the negative electrode bus bar 48 connected to the negative electrode terminal 34 has The path length is longer than that of the positive electrode bus bar 46. As a result, the negative electrode bus bar 48 is less rigid than the positive electrode bus bar 46. When an external force such as vibration is applied, there is a problem that stress concentrates on the negative electrode bus bar 48 with poor rigidity, in particular, on the tip portion of the negative electrode bus bar 48 with the lowest rigidity (that is, the connection portion with the negative electrode terminal 34). It was.

  In particular, in recent years, it has been proposed to install the power converter 10 on a transaxle case from the viewpoint of effective use of space. In this case, the vibration generated with the driving of the transaxle is transmitted to the power converter 10 and the capacitor 14 and the semiconductor module 30 vibrate. As a result, the problem of stress concentration at the connection portion between the negative electrode terminal 34 and the negative electrode bus bar 48 has become more serious.

  In order to avoid such a problem, it is conceivable to increase the rigidity of the negative electrode bus bar 48 by increasing the width of the negative electrode bus bar 48. However, as described above, the plurality of negative electrode bus bars 48 are composed of one negative electrode conductor plate 52, and the width of the plurality of negative electrode bus bars 48 cannot exceed the stacking pitch of the semiconductor modules 30. In particular, in recent years, the stacking pitch of the semiconductor modules 30 is kept as small as possible in order to reduce the size of the power conversion device 10, and there is almost no room for expanding the width of the negative electrode bus bar 48.

  Therefore, in the present embodiment, the width of the negative electrode terminal 34 connected to the negative electrode bus bar 48 having a long path length and a low strength in order to avoid the concentration of stress as described above without increasing the width of the negative electrode bus bar 48. Wn is made larger than the width Wp of the positive electrode terminal 32. More specifically, the width Wn of the negative electrode terminal 34 is set so that the rigidity of the entire negative electrode connection path composed of the negative electrode terminal 34 and the negative electrode bus bar 48 is equal to the entire positive electrode connection path composed of the positive electrode terminal 32 and the positive electrode bus bar 46. Increase the rigidity so that it is almost the same. By adopting such a configuration, the rigidity of the entire connection path is made uniform, so that stress concentration on one connection path is prevented. As a result, stress applied to the negative electrode bus bar 48 is reduced, and damage to the negative electrode bus bar 48 and breakage of the connection portion are effectively prevented. Further, by preventing stress concentration on one connection path, the stress input to each terminal 34, 36 and each bus bar 46, 48 can be evenly distributed, and the thickness of these terminals and bus bar can be reduced. Become. Furthermore, when the cross-sectional areas are equal, the connection path having a longer path length has a higher electrical resistance. However, in this embodiment, the width Wn of the terminal 34 of the negative path having a longer path length is increased. The difference in electrical resistance of the connection path at the positive electrode can also be reduced. Furthermore, if only the width Wn is changed without changing the thickness of the negative electrode terminal 34, the negative electrode terminal 34 and the positive electrode terminal 32 can be manufactured from a conductor plate having the same thickness, and the material can be shared. .

  However, as a matter of course, the wall thickness of the negative electrode terminal 34 may be increased in addition to or instead of increasing the width Wn of the negative electrode terminal 34. Even in this case, since the rigidity of the whole connection path of the negative electrode is improved, the rigidity of the whole connection path can be made uniform between the positive electrode and the negative electrode, and stress concentration on one side can be prevented. In addition to increasing the width Wn of the negative electrode terminal 34, the negative electrode terminal 34 may be shorter than the positive electrode terminal 32. If the negative electrode terminal 34 is shortened, the rigidity of the negative electrode terminal 34 is improved accordingly, so that the rigidity of the entire connection path can be made uniform between the positive electrode and the negative electrode, and stress concentration on one side can be prevented. Furthermore, in addition to increasing the width Wn of the negative electrode terminal 34, the thickness of the negative electrode bus bar 48 may be increased. Even in this case, the rigidity of the entire connection path of the negative electrode can be improved.

  In the example described above, the negative electrode terminal 34 is farther from the capacitor 14 than the positive electrode terminal 32, but this arrangement may be reversed. When the positive electrode terminal 32 is separated from the capacitor 14 more than the negative electrode terminal 34, the positive electrode bus bar 46 is longer than the negative electrode bus bar 48. Therefore, in this case, the width Wp of the positive electrode terminal 32 may be increased.

  In any case, by making the cross-sectional area of the terminal connected to the bus bar having a long path length larger than the cross-sectional area of the terminal connected to the bus bar having a short path length, the rigidity of the positive electrode connecting path and the negative electrode connecting path can be increased. Uniformity can be achieved, and stress concentration on one connection path can be prevented.

  DESCRIPTION OF SYMBOLS 10 Power converter, 12 Boost converter, 14 Capacitor, 16, 18 Inverter, 20 Reactor, 22 Cooling plate, 23, 24 Liquid supply pipe, 30 Semiconductor module, 32 Positive electrode terminal, 34 Negative electrode terminal, 36 Output terminal, 38, 40 Bus bar, 46 Positive bus bar, 48 Negative bus bar, 49 Control device, 50 Positive conductor plate, 52 Negative conductor plate, 70 Secondary battery, 72, 74 Rotating electric machine.

Claims (4)

A power conversion device comprising one or more semiconductor modules and a capacitor electrically connected to the one or more semiconductor modules,
The capacitor has a positive electrode bus bar and a negative electrode bus bar having different path lengths from each other,
Each semiconductor module has a positive terminal connected to the positive bus bar and a negative terminal connected to the negative bus bar,
Of the positive terminal and the negative terminal, a terminal connected to the bus bar having a long path length has a larger cross-sectional area than a terminal connected to the bus bar having a short path length.
The power converter characterized by the above-mentioned. The power conversion device according to claim 1,
Of the positive electrode terminal and the negative electrode terminal, a terminal connected to the bus bar having a long path length is wider than a terminal connected to the bus bar having a short path length. The power converter according to claim 1 or 2,
The positive electrode terminal and the negative electrode terminal are arranged side by side and extend in a direction orthogonal to the arrangement direction,
The positive electrode bus bar and the negative electrode bus bar extend toward the arrangement direction of the positive electrode terminal and the negative electrode terminal and are connected to corresponding terminal terminals.
The power converter characterized by the above-mentioned. The power conversion device according to any one of claims 1 to 3,
A plurality of the semiconductor modules are stacked,
The capacitor has a plurality of positive electrode bus bars and a plurality of negative electrode bus bars connected to a positive electrode terminal and a negative electrode terminal extending from a plurality of semiconductor modules,
A plurality of bus bars of the same polarity are formed by bending one conductor plate.
The power converter characterized by the above-mentioned.

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