WO2015019160A1

WO2015019160A1 - Power conversion device

Info

Publication number: WO2015019160A1
Application number: PCT/IB2014/001472
Authority: WO
Inventors: Kenshi YAMANAKA
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2013-08-08
Filing date: 2014-08-06
Publication date: 2015-02-12
Anticipated expiration: 2016-02-08
Also published as: JP2015035862A

Abstract

An inverter 5 includes power card 31 and a capacitor module 20. The capacitor module 20 is formed in a rectangular parallelepiped in the entire external shape and constituted of two capacitor elements 23, 24 which are divided by a plane parallel to a plane containing a short side that is the shortest side and a long side that is one of the other side of the rectangular parallelepiped. A positive and negative terminals of each capacitor element are provided on side faces which oppose each other across the short side. One of a bus bar 21 on a high potential side and a bus bar 22 on a low potential side extending from terminals of the power card is connected to a terminal of a capacitor element which opposes the power card while the other thereof passes between two capacitor elements and is connected to a terminal on a side face on an opposite side.

Description

POWER CONVERSION DEVICE

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present invention relates to a power conversion device such as an inverter and a voltage converter.

2. Description of Related Art

[0002] In many cases, the power conversion device such as the inverter and the voltage converter includes a plurality of transistors such as insulated gate bipolar transistors (IGBT). For example, in an inverter for driving a three-phase AC motor, three sets of series circuits each composed of two transistors are connected in parallel to each other and AC power is output from a midpoint of each series circuit. Further, a step-up/step-down converter also includes a series circuit composed of two transistors. In the inverter or the voltage converter, a capacitor for suppressing pulsation of current or a capacitor for storing electric energy by using a circuit which steps up or down a voltage is often connected to the series circuit each composed of two transistors in parallel to each other.

[0003] The power conversion device is used also in a motor drive system of an electric vehicle including a hybrid vehicle. Because^" electric power which the electric vehicle handles is large, the amount of heat generated from a transistor or a capacitor is large. Further, not a small-diameter cable but a plate-like or a bar-like metal member is used to connect the transistor with the capacitor because such a large current is handled. The plate-like or the bar-like metal member which allows a large current to pass with low resistance is generally called bus bar. An example in which the transistor and the capacitor are connected through the bus bar in a power conversion device configured to drive a traveling motor mounted on an electric vehicle has been disclosed in Japanese Patent Application Publication No. 2013-009581 (JP 2013-009581 A). [0004] The technology disclosed in JP 2013-009581 A includes a multilayered cooling unit in which a plurality of power cards in which transistors are sealed with resin are stacked with a plurality of flat cooling devices (cooling plates), and terminals of the transistors extending from the power card are connected to capacitors through the bus bar. Each of two bus bars on a high potential side (for positive electrode) and a low potential side (for negative electrode) extending from the power card is divided into two ways just in front of the capacitor so that the divided parts are connected to each of the terminals on both ends of the capacitor.

SUMMARY OF THE INVENTION

[0005] The present specification relates to a power conversion device which includes a power card in which transistors are sealed with resin and capacitors connected in parallel to the power card through a bus bar, and provides a power conversion device in which the shape of the capacitor and the layout of the bus bar are devised to reduce the equivalent series resistance (ESR) and the equivalent series inductance (ESL) of the capacitors containing the bus bars. . .

[0006] In the power conversion device according to an embodiment of the present specification, the capacitor component to be connected to the power card in parallel is constructed with not a single capacitor but a capacitor group in which two capacitor are connected in parallel. Hereinafter, for convenience for description, individual capacitors are called capacitor elements and a module in which two capacitor elements are connected in parallel to each other is called capacitor module. The capacitor module can be regarded as a capacitor when it is arranged on an electric circuit. The capacitor module is formed in a rectangular parallelepiped in the entire external shape and constituted of two capacitor elements which are divided by a plane parallel to a plane containing a short side that is the shortest side and a long side that is one of the other side of the rectangular parallelepiped. Then, a positive terminal and a negative terminal of each capacitor element are provided on side' faces thereof which oppose each other across the short side. On the other hand, the power card is arranged to face the side face on which one side terminal of the capacitor element is provided. One of a bus bar on the high potential side and a bus bar on the low potential side extending from terminals of the power card is connected to the terminal of a capacitor element which opposes the power card, while the other thereof passes; between the two capacitor elements and is connected to the terminal on a side face on the opposite side.

[0007] With the above-described structure, the bus bar is passed between two capacitor elements in the direction of the short side of the rectangular parallelepiped structure of the capacitor module, so that the bus bar can be connected to both the terminals without detoiiring around the capacitor entirely. That is, the above-described structure enables the bus bar which connects the power card to the capacitor elements to be reduced in length. As a result, the equivalent series inductance. (ESL) of the capacitor module containing the bus bar can be reduced. Further, by providing the terminals of the capacitor element on the side faces containing the long side, , that is, the side faces which oppose each other in the direction of the short side of the rectangular parallelepiped, a distance between the terminals can be reduced. Further, by providing the terminals of the capacitor elements on side faces having a larger area in the side faces of the rectangular parallelepiped, the area of the terminal can be increased so that a conducting area between the bus bar and the terminal can be increased. Due to both increase in the conducting area between the bus bar and the terminal and reduction in the distance between the terminals, the equivalent series resistance (ESR) of the capacitor module containing the bus bars is synergistically reduced.

[0008] Further, if a multilayered cooling unit in which a plurality of power cards are stacked alternately with a plurality of cooling plates is adopted, any one of the two following layouts may be adopted as the layout of the multilayered cooling unit and the capacitor module. According to a first layout, the capacitor module is arranged in a direction intersecting with an extension direction of the terminals of the power card to be connected to the capacitor module through the bus bar. According to a second layout, the capacitor module is arranged in the extension direction of the terminals of the power card to be connected to the capacitor module through the bus bar. In the meantime, the terminals of the power card extend in the first direction intersecting with the stacking direction of the power card and the cooling plates. According to the first layout, furthermore, the capacitor module is arranged such that the long side thereof extends along the stacking direction (stacking direction of the multilayered unit) while the short side extends in a direction intersecting with each of the stacking direction and the first direction. According to the second layout, furthermore, the capacitor module is arranged such that the long side thereof extends along the stacking direction while the short side extends in the first direction. The above-described arrangement enables the entire size of the assembly including the multilayered cooling unit and the capacitor module to be reduced into a compact size. As regards the size of the assembly, the first layout never increases the length of the terminal of the power card in the extension direction. The second layout never increases the length of the assembly in a direction intersecting with each of the extension directions of the stacking unit and the terminal of the power card.

[0009] In the meantime, the "rectangular parallelepiped" mentioned in the present specification may be provided with roundness at edges thereof or roughness, and the shape may be any shape as long as it can be approximated to a rectangular parallelepiped.

[00.10] The technology disclosed in the present specification relates to the power conversion device which includes the a power card in which transistors are sealed with resin and the capacitors which are connected in parallel to the power card through the bus bars and can reduce the equivalent series resistance (ESR) and the equivalent series inductance (ESL) of the capacitors and the bus bars.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a system diagram of a drive system of a hybrid vehicle; FIG. 2 is a perspective view of an assembly including a multilayered cooling unit and a capacitor module;

FIG. 3 is an exploded perspective view of the capacitor module;

FIG. 4 is a side view of the assembly including the multilayered cooling unit and the capacitor module; and

FIG. 5 is a side view showing a modification example of the layout of the assembly including the multilayered cooling unit and the capacitor module.

DETAILED DESCRIPTION OF EMBODIMENTS

[0012] A power conversion device according to an embodiment of the present invention will be described with reference to drawings. The power conversion device is an inverter which is mounted on a hybrid vehicle including a traveling motor and an engine to convert DC power of a battery to AC, power suitable for driving the motor. First, a driving system of a hybrid vehicle 2 including the inverter 5 (power conversion device) will be described with reference to FIG. 1. The hybrid vehicle 2 includes an engine 6 and a motor 8 for traveling. An output of the engine 6 and an output of the motor 8 are synthesized by a power distribution mechanism 7 and transmitted to an axle 9. In some case, the power distribution mechanism 7 distributes the output of the engine 6 to the axle 9 and the motor 8. In that case, the hybrid vehicle 2 generates electric power using the motor 8 as a generator while traveling with the output of the engine 6.

[0013] The hybrid vehicle 2 also includes a battery 3 for storing electric power for driving the motor 8. The battery 3 is connected' to the inverter 5 through a system main relay 4. The inverter 5 is constituted of a filter capacitor for smoothing a current from the battery 3, six transistors 14 and six diodes 15. In the meantime, in the drawing, only two transistors and two diode's are provided with reference numerals while the reference numerals of other transistors and diodes are omitted. Further, although a circuit for controlling the transistors 14 and the like are incorporated as well as the above-mentioned components inside the inverter 5, representation thereof is omitted. The filter capacitor 16 is physically structured by connecting two capacitors 12a, 12b in parallel to each other. In the six transistors 14, two thereof are connected in series as a pair, and further the three sets of the series-connected circuits are connected in parallel. The diode 15 is connected to each transistor 14 in antiparallel. AC power is output from a midpoint of the series connection of the two transistors as a pair. That is, the transistor 14 is a device which generates electric power to be supplied to the motor 8. Because the circuit structure of the inverter has been well known, a detailed description thereof is omitted.

[0014] The series circuit of the transistors 14a, 14b is expressed with reference numeral 13a. Other two series circuits are expressed with reference numerals 13b, 13c. AC powers are output from each of the three series circuits with a phase shift of 120° with respect to each other. In the meantime, the respective series circuits 13a, 13b, 13c correspond to power card 31 described below.

[0015] The three series circuits 13a, 13b, 13c and the filter capacitor 16 are connected, in parallel through a positive electrode bus bar 21 (bus bar on the high potential side) and a negative electrode bus bar 22 (bus bar on the low potential side). In the meantime, in a circuit diagram of FIG. 1 , the bus bars 21, 22 are represented with a rectangular shape to distinguish from other wiring cables in order to help understanding of technology in the present specification.

[0016] The structural features of the filter capacitor 16 constituted of the two capacitors 12a, 12b, the three series circuits 13a, 13b, 13c each of which is constituted of a pair of transistors, and the bus bars 21 , 22 will be described below.

[0017] FIG. 2 is a perspective view of an assembly including a multilayered cooling unit 30 and a capacitor module 20. FIG. 3 shows an exploded perspective view of the capacitor module 20. The multilayered cooling unit 30 is constructed by stacking a plurality of flat power cards 31 and a plurality of cooling plates 32 alternately. The plural cooling plates 32 are connected to each other at two positions via a pipe 35 each (in the drawing, one pipe thereof is invisible because it is hidden by the power card). Further, a refrigerant supply pipe 33 and a refrigerant discharge pipe 34 are connected to the cooling plate 32 at one side end in the stacking direction. A refrigerant circulation device (not shown) is connected to the refrigerant supply pipe 33 and the refrigerant discharge pipe 34. Refrigerant supplied from the refrigerant supply pipe 33 flows separately to all the cooling plates 32 through the pipe 35. After passing through each cooling plate 32, the refrigerant returns to the refrigerant circulation device (not shown) through the other pipe and the refrigerant discharge pipe 34. While refrigerant passes the inside of the cooling plates 32, the power cards 31 sandwiched by the cooling plates 32 are cooled.

[0018] Each of the power cards 31 is formed by sealing two transistors and two diodes with resin. The two transistors are connected in series inside a resin package. The two diodes are connected to each of the two transistors in antiparallel inside the resin package. The three power cards 31 correspond to the respective series circuits 13a, 13b, 13c described with FIG. 1. Three terminals 31a, 31b, 31c project from each of the power cards 31. The terminal 31b corresponds to a terminal on the high potential side of the series circuit 13 in FIG. 1 and the terminal 31a corresponds to a terminal on the low potential side of the series circuit 13. The terminal 31c corresponds to a midpoint of the series circuit 13. That is, AC power is output from the terminal 31c.

[0019] As described with FIG. 1 above, the terminals on the high potential side of the three series circuits 13 (high potential terminals 31b of the power card) are connected through the positive electrode bus bar 21 , and the terminals on the low potential side thereof (low potential terminals 31a of the power card) are connected through the negative electrode bus bar 22. A filter capacitor 16 is connected between the positive electrode bus bar 21 and the negative electrode bus bar 22. That is, the filter capacitor 16 and the three power cards 31 are connected in parallel through the two bus bars 21 , 22. Although another bus bar is connected to the terminal 31c, representation thereof is omitted.

[0020] A capacitor module 20 is constituted of two rectangular parallelepiped capacitor elements 23„ 24. The two capacitor elements 23, 24 correspond to the two capacitors 12a, 12b in FIG. 1. The entire external shape including the two capacitor elements 23, 24 arranged adjacent to each other (i.e., external shape of the capacitor module 20) is also rectangular parallelepiped. Hereinafter, the longest side of the rectangular parallelepiped of the external shape of the capacitor module 20 is called module long side and the shortest side is called module short side. A reference numeral HI, in the drawing corresponds to the module long side and a reference numeral H2 corresponds to the module short side. Each of the two capacitor elements 23, 24 has two sides each having the same length as the module long side and the module short side. The two capacitor elements 23, 24 are adjacent to each other such that their faces constituted of two sides corresponding to the module long side and the module short side oppose each other. In other words, the capacitor module 20 is formed in a rectangular parallelepiped in the entire external shape and constituted of the two capacitor elements 23, 24 which are divided by a plane parallel to a plane (X-Y plane on the coordinate system in the figure) containing the longest side (module long side) and the shortest side (module short side) of the rectangular parallelepiped.

[0021] Each of the capacitor elements 23, 24 is produced by winding sheet-like positive electrode body, separator and negative electrode body in this order so that they are laminated on each other. Such a capacitor is called wound type capacitor also. The terminals (positive electrode terminal 23a and negative electrode terminal 23b) of the capacitor element 23 are provided on each of the side faces which oppose each other across the side corresponding to the module short side. The terminals (positive electrode terminal 24a and negative electrode terminal 24b) of the capacitor element 24 are also provided on each of the side faces which oppose each other across the side corresponding to the module short side. Eventually, the terminals of the two capacitor elements are provided on the side faces located across the short side of the rectangular parallelepiped which is the external shape of the capacitor module 20. In other words, the terminals of the capacitor elements are provided on each of the opposing faces having the shortest gap in the rectangular parallelepiped of the capacitor module 20. In the meantime, the terminals of the capacitor element are produced according to metal spraying method which is called Metallikon. [0022] As shown in FIGs. 2, 3, the power cards 31 are arranged to face the side faces on which the positive electrode terminals 23a, 24a of the capacitor elements 23, 24 are provided. The positive electrode bus bar 21 is a bent metal plate and an end 21a thereof is connected to the high potential terminal 31b of the power card 31 while the other ends (21b, 21c) thereof contact the capacitor positive electrode terminals 23a, 24a which face the power cards 31. More specifically, the other ends of the bus bar are bent vertically to two ways, so that one side end 21b is connected to the positive electrode terminal 23a of the capacitor element 23 while the other side end 21c is connected to the positive electrode terminal 24a of the capacitor element 24.

[0023] The negative electrode bus bar 22 is also a bent metal plate. An end 22a of the negative electrode bus bar 22 is connected to the low potential terminal 31a of the power card 31 and the other ends (22b, 22c) are connected to the negative electrode terminals 23b, 24b. More specifically, the other ends of the bus bar 22 are bent vertically to two ways, so that the one side end 22b is connected to the negative electrode terminal 23b of the capacitor element 23 while the other side end 22c is connected to the negative electrode terrninal 24b of the capacitor element 24. The halfway portion of the negative electrode bus bar 22 passes between the two capacitor elements 23 and 24. In other words, one of the positive electrode bus bar 21 and the negative electrode bus bar 22 extending from the terminals 31a, 31b of the power card 31 is connected to the terminals 23a, 24a which oppose the power card 31, while the other one thereof passes between the two capacitor elements so that it is connected to the terminals 23b, 24b arranged on the side faces on the opposite side.

[0024] The side view taken from the Y-axis direction of the coordinate system expressed in FIG. 3 is shown in FIG. 4. In the meantime, the capacitor elements 23, 24 are represented in a sectional view. As illustrated well in FIG. 3, a section (X-Z plane on the coordinate system in the figure) of the capacitor module 20 perpendicular to the module long side is rectangular and the two capacitor elements 23, 24 are arranged adjacent to each other such that they divide the rectangular shape of the section into two sections. The terminals (23a, 23b, 24a, 24b) of the respective capacitor elements 23, 24 are provided on two side faces which oppose each other across the short side of the rectangular shape of their sections (this short side corresponds to the module short side). Because this short side corresponds to the shortest side (module short side) of the rectangular parallelepiped of the capacitor module, it comes that a distance between the positive and negative terminals is the shortest. Further, the one bus bar (negative bus bar 22) passes between the two capacitor elements 23 and 24, so that it is connected to the terminals 23b, 24b on the opposite side of the power card 31.

[0025] In the inverter 5 according to the present embodiment, the negative electrode bus bar 22 is passed between the two capacitor elements 23 and 24 in the direction of the short side (X-direction in the figure) of the rectangular parallelepiped of the capacitor module 20. This structure allows the bus bar to be connected to both the terminals of the capacitor elements without detouring around the capacitor module entirely. That is, the structure of the capacitor module 20 according to the present embodiment enables the bus bar which connects the power card 31 to the capacitor elements 23, 24 to be reduced in length. As a result, the equivalent series inductance (ESL) of the capacitor module 20 containing the bus bar is reduced. Further, by providing the terminals (positive and negative terminals) of the capacitor elements on the capacitor element side face containing a side corresponding to the module long side, that is, on each of the capacitor element side faces opposing each other across the module short side, a distance between the terminals can be reduced. Further, by providing the terminals of the capacitor elements on side faces having a larger area in the side faces of the rectangular parallelepiped, the area of the terminal can be increased so that a conducting area between the bus bar and the terminal can be increased. Due to both increase in the conducting area between the bus bar and the terminal and reduction in the distance between the terminals, the equivalent series resistance (ESR) of the capacitor module containing the bus bars is synergistically reduced.

[0026] Further, as shown well in FIG. 3, the capacitor module 20 is arranged in a direction (X-axis direction in the figure) intersecting with an extension direction (Z-axis direction in the figure) of the terminals 31a, 31b of the power card 31 with respect to the multilayered cooling unit 30 and adjacent to the multilayered cooling unit 30. Further, according to the layout of FIG. 2, the capacitor module 20 is arranged such that the long side thereof extends along the "stacking direction (Y-axis direction in the figure) of the multilayered cooling unit 30 and the short side thereof extends in a direction (X-axis direction in the figure) perpendicular to each of the stacking direction and the extension direction of the terminal 31a, 31 b. This layout contributes to reduction in size in the Z-axis direction in the figure for the assembly including the multilayered cooling unif 30 and the capacitor module 20.

[0027] FIG. 5 shows a modification example of the layout of the capacitor module and the multilayered cooling unit. In the modification example of FIG. 5, the capacitor module 20a is arranged adjacent to the multilayered cooling unit 30 in the extension direction (Z-axis direction in the figure) of the terminals of the power card 31. The other features are the same as the examples shown in FIGs. 1 to 4, for example, in that the capacitor module 20a is constituted of the two capacitor elements 23, 24 and the one side bus bar passes between the two capacitor elements. According to the layout of FIG. 5, the capacitor module 20a is arranged such that a long side thereof extends in the stacking direction (Y-axis direction in the figure) of the multilayered cooling unit30 while a short side thereof extends in the extension direction (Z-axis direction in the figure) of the terminal 31 a, 31 b. The layout of FIG. 5 contributes to reduction in size in the X-axis direction in the figure of the assembly including the multilayered cooling unit 30 and the capacitor module 20a.

[0028] Points to be considered concerning the technology of the present embodiment will be described. The capacitor elements 23, 24 according to the present embodiment are represented each as a complete rectangular parallelepiped. The shape of the capacitor element may be of any shape as long as it is substantially rectangular parallelepiped, and for example, their edges may be round or the surface of the capacitor element may have roughness. Alternatively, the sectional shape of the capacitor element may be substantially elliptic. Because the^' ellipse is a shape which can be inscribed inside, a rectangle and can be approximated to the rectangular shape, even if the section is elliptical, it may be regarded as a rectangular parallelepiped in terms of its external shape.

[0029] The power conversion device according to the present embodiment is an inverter. The power conversion device may be a voltage converter configured to step up/down a voltage or may be a combination of an inverter and a voltage converter. The voltage converter also includes a series circuit of two transistors. In case where the technology disclosed in the present specification is applied to a power conversion device including both the inverter and the . voltage converter, each thereof includes a multilayered cooling unit in which four or more molded power cards containing transistor series circuit are stacked alternately with the cooling plates. The four power cards, and the capacitor module are connected in parallel through two bus bars.

[0030] In FIGs. 2 to 5, the Z-axis direction on the coordinate system in the figure corresponds to the extension direction of the terminals 31a, 31b, 31c of the power card 31 or "a first direction" in claims.

[0031] Although specific examples of the present invention have been described in detail above, they are just exemplifications but never restrict the scope of claims. The technology described in the scope of claims includes modifications and alterations of the specific examples described above. The technical components described in the present specification or drawings exert technical usefulness independently or by various combinations and are not restricted by combinations thereof described in claims upon filing. Further, the technology exemplified in the present specification or drawings can achieve a plurality of objects at the same time and has a technical usefulness just by achieving one of them

Claims

L A power conversion device comprising:

a power card in which transistors are sealed with resin; and

a capacitor module which is connected to the power card in parallel through bus bars, wherein

the capacitor module is formed in a rectangular parallelepiped in its entire external shape and includes two capacitor elements which are divided by a plane parallel to a plane containing a short side that is the shortest side and a long side that is one of the other side of the rectangular parallelepiped and a positive terminal and a negative terminal of the capacitor element are provided on each of side faces which oppose each other across the short side,

the power card is arranged to face the side face on which one side terminal of the capacitor element is provided, and

one of a high potential side bus bar and a low potential side bus bar extending from terminals of the power card is connected to a terminal of the capacitor element which opposes the power card while the other thereof passes between the two capacitor elements and is connected to a terminal on a side face on an opposite side.

2. The power conversion device according to claim 1 , wherein

a long side is the longest side of the rectangular.

3. The power conversion device according to claim 1 or 2, wherein

bus bars are a metal plate.

4. The power conversion device according to claim 1 or 2, wherein

bus bars are a bent metal plate.

5. The power conversion device according to claim 1 or 2, wherein the power card is sandwiched by cooling plates and the capacitor module is arranged in a direction intersecting with an extension direction of the terminals of the power card to be connected to the capacitor module through the bus bars.

6. The power conversion device according to claim 5, wherein

a plurality of power cards are stacked alternately with the cooling plates, wherein the terminals of the power card extend in a first direction perpendicular to a stacking direction of the power card and the cooling plates,

wherein the capacitor module is arranged such that the long side thereof extends along the stacking direction while the short side extends in a direction intersecting with each of the stacking direction and the first direction.

7. The power conversion device according to claim 1, wherein

the power card is sandwiched by the cooling plates and the capacitor module is arranged in the extension direction of the terminals of the power card to be connected to the capacitor module through the bus bars.

8. The power conversion device according to claim 7, wherein

a plurality of power cards are stacked alternately with the cooling, plates, wherein the terminals of the power card extend in the first direction perpendicular to the stacking direction of the power card and the cooling plates,

wherein the capacitor module is arranged such that the long side thereof extends in the stacking direction while the short side extends along the first direction.