JP2015126674A - Electric power conversion system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure which enables a heat conduction rate to be improved between a capacitor case for storing capacitor elements and a housing of an electric power conversion system and makes the high heat conduction rate less likely to be deteriorated even under a high vibration environment in the electric power conversion system including the capacitor elements connected in parallel with a voltage converter circuit.SOLUTION: An electric power conversion system 2 disclosed by the specification includes: capacitor elements 13a, 13b connected in parallel with a voltage converter circuit; a capacitor case 12 which stores the capacitor elements; and a metal housing 3 which stores the capacitor case and a lamination unit 40 forming the voltage converter circuit. The capacitor case 12 is bonded to a storage part provided at the housing 3 by a heat radiation adhesive 15 and is fixed to the bottom side of the housing 3 at the opening side by bolts 16a to 16c.

Description

  The present invention relates to a power converter including a voltage converter circuit and an inverter circuit. In particular, the present invention relates to a power converter that supplies power to a traveling motor of an electric vehicle. The electric vehicle in this specification includes an electric vehicle or a fuel cell vehicle that includes a motor for traveling but does not include an engine, and a hybrid vehicle that includes both a motor and an engine for traveling.

  Power converters are used in various places. In recent years, hybrid vehicles have become widespread, but hybrid vehicles (electric vehicles including hybrid vehicles) are also equipped with a power conversion device that converts DC power of a battery into AC power for driving a driving motor. A typical power converter converts power by switching operation of a semiconductor element called a power transistor. In order to suppress current pulsation due to switching operation of a semiconductor element, or as a component of a voltage converter circuit, a power conversion device often includes a capacitor element. Since the power converter that supplies power to the motor for traveling uses a large amount of power, both the semiconductor element and the capacitor element generate a large amount of heat. In particular, a large-capacity capacitor element also increases in size. On the other hand, downsizing is also required for in-vehicle devices. That is, when the size of the electronic component is large, it is necessary to devise the layout in the casing of the power conversion device.

  An example of such an in-vehicle power converter is disclosed in Patent Documents 1 and 2. In the power converters disclosed in these documents, the capacitor element is housed in a dedicated case (capacitor case), and the capacitor case is bolted to the casing of the power converter. The capacitor case is bolted at the housing opening (upper surface). A resin sealing member is filled between the inner surface of the capacitor case and the capacitor element. Further, in the power conversion device of Patent Document 2, the internal space of the housing is divided into a cooler housing space for housing a semiconductor element and a cooler and a capacitor housing space for housing a capacitor element.

JP2013-9581A JP 2012-217322 A

  If the capacitor case is simply bolted to the housing, a microscopic gap is generated between the capacitor case and the housing, and high heat transfer characteristics cannot be obtained. It is conceivable to increase the heat transfer characteristics by filling a sealing material with high thermal conductivity between the capacitor case and the housing. However, since the vibration is continuously applied to the vehicle-mounted device, the sealing material may be peeled off. There is.

  The present specification relates to a power conversion device including a capacitor element connected in parallel to a voltage converter circuit. The power converter disclosed in the present specification improves the thermal conductivity (heat transfer coefficient) between the capacitor case that houses the capacitor element and the casing of the power converter, and the high thermal conductivity is sustained. Provides a structure that does not easily deteriorate even in a severe vibration environment.

  In the power converter disclosed in this specification, a capacitor element connected in parallel to the voltage converter circuit is housed in a dedicated case (capacitor case), and the capacitor case is bolted to the casing of the power converter. ing. A semiconductor element (an element electrically connected to the capacitor element) constituting the voltage converter circuit is also accommodated in the housing. The semiconductor element is a switching element (transistor) that constitutes a voltage converter circuit and an inverter circuit, and is typically molded with resin. The power conversion apparatus accommodates a capacitor element and a laminated unit in which a plurality of power cards in which semiconductor elements are molded with resin and a plurality of cooling plates are alternately laminated.

  In the power conversion device disclosed in the present specification, the capacitor case is further bonded to a housing portion provided in the casing by a heat radiation adhesive, and the bottom side (lower part) and the opening side (upper part) of the casing. It is fixed with bolts. By filling the gap between the capacitor case and the housing with a heat radiation adhesive instead of a mere filler, high thermal conductivity is achieved between the capacitor case and the housing, and they are firmly fixed. The heat radiation adhesive is also called a heat conductive adhesive, and is an adhesive made of a material having high thermal conductivity. For example, an adhesive mainly composed of silicon or thermally conductive epoxy corresponds to these. In order to increase the thermal conductivity, a metal filler (small metal piece) may be mixed.

  Further, the above power conversion device not only fixes the capacitor case with a heat-dissipating adhesive, but also includes the bottom side (lower part) and the opening side (the case opening side into which the capacitor case is inserted). Fasten with bolts at the top of the housing. Since the casing is cylindrical with a bottom, “bottom side” can be rephrased as “lower part of the casing”, and “opening side” is “upper part of the casing” (the opposite side from the bottom side) ). The above power converter has high vibration resistance because the capacitor case is bolted at the top and bottom thereof. In the power converters disclosed in Patent Documents 1 and 2, since the capacitor case is bolted only at the upper part of the housing, the capacitor case is cantilevered, and the lower part of the capacitor case farthest from the fastening point easily vibrates. . On the other hand, in the power conversion device disclosed in this specification, the capacitor case is fastened with bolts at the upper and lower sides thereof, so that it is equivalent to a double-sided support and is difficult to vibrate. Since the capacitor case is difficult to vibrate, the heat-dissipating adhesive filled between the capacitor case and the housing is difficult to peel off. In other words, the power conversion device disclosed in the present specification achieves high thermal conductivity between the capacitor case and the housing, and the high thermal conductivity is unlikely to decrease even in an environment in which continuous vibrations are received.

  The technology disclosed in this specification relates to a power conversion device including a capacitor element connected in parallel to a voltage converter circuit, and improves thermal conductivity between a capacitor case that houses the capacitor element and a casing of the power conversion device. In addition, it provides a structure whose high thermal conductivity is not easily lowered even in an environment of continuous vibration. Details and further improvements of the technology disclosed in this specification will be described in the following “DETAILED DESCRIPTION”.

It is a block diagram of the electric power system of the hybrid vehicle containing the power converter device of an Example. It is a top view of a power converter. It is sectional drawing in the III-III line of FIG. It is sectional drawing in the IV-IV line of FIG.

  A power converter according to an embodiment will be described with reference to the drawings. The power conversion device according to the embodiment is a device that is mounted on a hybrid vehicle, converts DC power of a battery into AC power, and supplies the AC power to a traveling motor. First, a power system of a hybrid vehicle including a power conversion device will be described.

  FIG. 1 shows a block diagram of a power system of the hybrid vehicle 30. A main battery 31 is connected to the power conversion device 2 via a system main relay 32. The power converter 2 includes a voltage converter circuit 33 that boosts the power of the main battery 31 and an inverter circuit 35 that converts the boosted DC power into AC power. The output of the inverter circuit 35 corresponds to the output of the power conversion device 2 and is supplied to the motor 37. The output torque of the motor 37 and the output torque of the engine 36 are combined or distributed by the power distribution mechanism 38 and transmitted to the axle 39.

  The circuit configuration of the power converter 2 will be outlined. The voltage converter circuit 33 includes a series circuit of two power transistors 21 a and 22 a and a reactor 6 in which one end is connected to the midpoint of the series circuit and the other end is connected to the input terminal of the voltage converter circuit 33. And a filter capacitor 5a connected in parallel to the input terminal of the voltage converter circuit 33. The inverter circuit 35 has a circuit configuration in which three sets of series circuits of two power transistors 21b and 22b are connected in parallel. In FIG. 1, reference numerals for some power transistors are omitted. UVW-phase alternating current is output from the midpoint of the three sets of series circuits. A diode is connected in antiparallel to each power transistor 21a, 21b, 22a, 22b. The power transistor included in the voltage converter circuit 33 and the power transistor included in the inverter circuit operate by receiving a PWM signal from the controller board 34. Since the structures of the voltage converter circuit 33 and the inverter circuit 35 are well known, detailed description thereof will be omitted.

  The smoothing capacitor 5 b is connected in parallel to the output end of the voltage converter circuit 33, in other words, the input end of the inverter circuit 35. The smoothing capacitor 5 b smoothes the pulsating component superimposed on the output current of the voltage converter circuit 33, in other words, the input current to the inverter circuit 35.

  Each element of the voltage converter circuit 33 and the inverter circuit 35 generates a large amount of heat because a large current supplied to the traveling motor 37 flows. Typical elements that generate a large amount of heat are the power transistors 21a, 21b, 22a, 22b, the filter capacitor 5a, the smoothing capacitor 5b, and the reactor 6 shown in FIG.

  The hardware layout inside the housing of the power conversion device 2 will be described. FIG. 2 is a top view of the power conversion device 2 (illustration of the cover is omitted). 3 is a cross-sectional view taken along line III-III in FIG. 4 is a cross-sectional view taken along line IV-IV in FIG.

  The inside of the housing 3 of the power conversion device 2 is partitioned into three spaces. A capacitor housing space Sp1, a cooler housing space Sp2, and a board housing space Sp3, respectively. Refer to FIG. 3 and FIG. 4 for the substrate accommodation space Sp3. The housing 3 is made of aluminum.

  The stacked unit 40 and the reactor unit 46 are accommodated in the cooler accommodating space Sp2. The stacking unit 40 is a device in which a plurality of flat plate type coolers 42 and a plurality of flat plate type power cards 20 are alternately stacked. One end of the stacking unit 40 in the stacking direction is in contact with the inner surface of the side wall of the housing 3, and the other end is pressed by a leaf spring 45. A reactor unit 46 is disposed on the opposite side of the laminated unit 40 with the leaf spring 45 interposed therebetween. Reactor unit 46 corresponds to reactor 6 in the circuit diagram of FIG. In FIG. 4, the reactor unit 46 is drawn in a simplified manner with a two-dot dashed rectangle.

  The power card 20 will be described. Each power card 20 is sealed with two power transistors. In addition, since the cross section of the power card | curd 20 is shown by FIG. 3, please refer. The two power transistors are sealed with a resin package 23. The two power transistors are an upper arm transistor 21 and a lower arm transistor 22, which are connected in series inside the resin package 23. Although not shown, the power card 20 is also sealed with a diode connected in antiparallel to each power transistor. The diode is located behind the power transistors 21 and 22 in FIG. One power card 20 corresponds to one series circuit. A series circuit of power transistors 21 and 22 in one power card 20 corresponds to, for example, the power transistors 21a and 22a of the voltage converter circuit in FIG. Alternatively, a series circuit of power transistors 21 and 22 in another power card 20 corresponds to the power transistors 21b and 22b of the inverter circuit of FIG.

  As shown in FIG. 3, three terminals 20 a, 20 b, and 20 c extend from the upper end of the resin package 23. The terminal 20a corresponds to the high potential side terminal of the series circuit of the power transistors, and the terminal 20b corresponds to the low potential side terminal. The terminal 20c corresponds to the midpoint of the series circuit. A bus bar is connected to each of the terminals 20a, 20b, and 20c, but the bus bar is not shown in FIG. In FIG. 3, the bus bars 8a and 8b connecting the terminals 20a and 20b and the capacitor element 13b are shown, but the bus bar connected to the terminal 20c is not shown. These bus bars will be described later. The capacitor element 13b corresponds to the smoothing capacitor 5b in the circuit diagram of FIG. The capacitor element 13a corresponds to the filter capacitor 5a in the circuit diagram of FIG.

  Further, from the lower end of the resin package 23, gate terminals 21d and 22d extending to the gates of the power transistors 21 and 22 extend. The gate terminals 21d and 22d extend from the cooler housing space Sp2 to the substrate housing space Sp3, and are connected to the controller substrate 34 stored in the substrate housing space Sp3. The controller board 34 is not shown.

  A refrigerant supply pipe 43 and a refrigerant discharge pipe 44 pass through the plurality of coolers 42 constituting the stacked unit 40, and the refrigerant supply pipe 43 and the refrigerant discharge pipe 44 extend outside the housing 3. The inside of each cooler 42 is hollow, and the refrigerant supplied from the outside through the refrigerant supply pipe 43 passes through the inside of the cooler 42 and is discharged to the outside through the refrigerant discharge pipe 44. The cooler 42 at one end of the stacked unit 40 is in contact with the casing 3, and each cooler 42 cools the power transistors 21 and 22 in the power card in contact with both sides of the stacked unit 40, and a metal casing. The reactor unit 46 (reactor 6 in FIG. 1) and the capacitor elements 13a and 13b (filter capacitor 5a and smoothing capacitor 5b in FIG. 1) are cooled via the body 3.

  The capacitor accommodation space Sp <b> 1 and the cooler accommodation space Sp <b> 2 of the housing 3 are partitioned by a partition wall 4. The partition wall 4 is a part of the housing 3. A container-like capacitor housing space Sp <b> 1 is formed by a part of the inner wall of the housing 3 and the partition wall 4.

  The capacitor elements 13a and 13b are accommodated in a resin-made capacitor case 12, and the capacitor case 12 is accommodated in the capacitor accommodation space Sp1. The capacitor elements 13a and 13b and the capacitor case 12 are collectively referred to as a capacitor unit 10. The capacitor elements 13 a and 13 b are fixed with a potting resin 14 in the capacitor case 12. In other words, the space between the inner surface of the capacitor case 12 and the capacitor elements 13 a and 13 b is filled with the potting resin 14. The upper surfaces of the capacitor elements 13 a and 13 b are also covered with the potting resin 14. The potting resin 14 is an insulator. The potting resin 14 is a resin in which fluid resin is first poured into the above-described space and then solidified. That is, the potting resin 14 is filled by potting.

  The capacitor element 13 b includes electrodes on two surfaces parallel to the bottom surface of the housing 3. The electrodes and terminals 20a, 20b (power transistor terminals) of the power card 20 are connected to bus bars 8a, 8b (see FIG. 3). In addition, illustration of a bus bar is abbreviate | omitted in FIG. Further, in FIG. 3, the bus bar 8a is shown in cross section, and the connection portion of the bus bar 8b with the capacitor element 13b is hidden behind the bus bar 8a and cannot be seen. The bus bars 8a and 8b pass through the potting resin 14 and are connected to the capacitor element 13b. Bus bar 8 a is connected to the electrode of capacitor element 13 b on the side close to the bottom surface of housing 3. The bus bar 8b is connected to the electrode of the capacitor element 13b on the side far from the bottom surface of the housing. The bus bars 8a and 8b are conductive members for transmitting a large current with a low resistance, and are made of an elongated copper plate. The capacitor element 13a is connected in the same manner as the capacitor element 13b by another bus bar (not shown).

  The capacitor unit 10 is housed in the capacitor housing space Sp <b> 1 of the housing 3, and at that time, the space around the capacitor case 12 is filled with the heat radiation adhesive 15. In other words, the capacitor case 12 (capacitor unit) is fixed to the housing 3 with the heat radiation adhesive 15. The heat radiation adhesive 15 is a functional adhesive having excellent heat radiation characteristics. The main component is, for example, silicon resin, and the thermal conductivity is, for example, about 4 [W / m · K]. Some heat-dissipating adhesives contain a metal filler or a non-conductive filler in order to increase the thermal conductivity.

  The capacitor case 12 (capacitor unit 10) is not only fixed to the casing 3 with the heat radiation adhesive 15, but also fixed to the casing 3 with three bolts 16a, 16b, 16c. As shown in FIGS. 2 to 4, the capacitor case 12 is fixed with one bolt 16 a on the opening side of the housing 3, and two bolts on the bottom side of the housing 3. It is fixed at 16b and 16c. FIG. 4 shows a cross section passing through the bolt 16b. Here, the “opening side” indicates the opening of the housing 3. In other words, the “opening side” corresponds to the side on which the capacitor case 12 is inserted. The three fixed points by the bolts 16a to 16c are selected so that the center of gravity of the capacitor unit 10 is included in the triangle connecting the three points.

  As described above, the capacitor case 12 (capacitor unit 10) is fixed by two different types of fixing means, ie, the heat radiation adhesive 15 and the three bolts 16a-16c. The advantages of this structure will be described. By fixing the capacitor case 12 with the heat radiation adhesive 15, the heat of the capacitor elements 13 a and 13 b is efficiently diffused to the housing 3.

  On the other hand, the power conversion device 2 is for in-vehicle use and continuously receives vibration during traveling. Although the capacitor case 12 (capacitor unit 10) is fixed to the housing 3 by the heat radiation adhesive 15, the capacitor case 12 deteriorates when subjected to continuous vibration, and the heat radiation adhesive 15 may be peeled off. Therefore, in the power converter 2, the capacitor case 12 is fixed with three bolts 16a-16c to suppress vibration. In particular, by fixing the capacitor case 12 at the upper part (opening side of the housing 3) and the lower part (bottom side of the housing 3), the capacitor case 12 is supported on both the upper and lower sides, and is resistant to vibration. The characteristics are enhanced. That is, the power conversion device 2 is unlikely to peel off the heat radiation adhesive 15 from the capacitor case 12 or the inner surface of the housing 3 even if the power conversion device 2 is used for a long time in an environment where continuous vibration is received.

  Other characteristics of the power conversion device 2 will be described. In the power conversion device 2, the bus bar 8 a extends along the partition wall 4. By causing the bus bar 8a connected to the capacitor elements 13a and 13b to run parallel to the partition wall 4 of the metal housing 3, a part of the magnetic field generated from the current flowing through the bus bar 8a can be absorbed by the partition wall 4, Inductance can be reduced. As a result, the loss of the power conversion device can be reduced.

  Points to be noted regarding the technology described in the embodiments will be described. The power transistors 21 and 22 correspond to an example of a semiconductor element. The power transistors 21a and 22a correspond to an example of a semiconductor element constituting the voltage converter circuit. Further, the capacitor case 12 may be made of metal or resin.

  A further advantage of increasing the heat dissipation efficiency of the capacitor element will be described. A film type capacitor element is suitable as a large-capacity capacitor element. In a film-type capacitor element, when the capacitance is the same, the smaller the film thickness, the smaller the capacitor element size. However, when the film thickness is reduced, the distance between the deposited films is reduced, and the withstand voltage performance is lowered. The withstand voltage performance decreases as the temperature increases. Therefore, increasing the heat dissipation efficiency of the capacitor element leads to lowering the upper limit of the environmental temperature range of the capacitor element. If the upper limit of the environmental temperature range is lowered, the required high temperature characteristics are relaxed, that is, the withstand voltage performance requirement at high temperatures is also relaxed, so that the film thickness can be reduced. The capacitor element can be reduced in size.

  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.

2: Power converter 3: Housing 4: Bulkhead 5a: Filter capacitor 5b: Smoothing capacitor 6: Reactor 8a, 8b: Bus bar 10: Capacitor unit 12: Capacitor case 13a, 13b: Capacitor element 14: Potting resin 15: Heat dissipation Adhesive 16a-16c: Bolt 20: Power card 20a, 20b, 20c: Terminal 21, 21a, 21b, 22, 22a, 22b: Power transistor (semiconductor element)
23: Resin package 30: Hybrid vehicle 31: Main battery 32: System main relay 33: Voltage converter circuit 34: Controller board 35: Inverter circuit 36: Engine 37: Motor 40: Stack unit 42: Cooler 43: Refrigerant supply pipe 44 : Refrigerant discharge pipe 45: Leaf spring 46: Reactor unit Sp1: Capacitor housing space Sp2: Cooler housing space Sp3: Board housing space

Claims (1)

A capacitor element connected in parallel to the voltage converter circuit;
A capacitor case containing the capacitor element;
A housing made of metal for housing the capacitor case and housing a semiconductor element constituting the voltage converter circuit;
With
The capacitor case is bonded to a housing portion provided in the casing with a heat radiation adhesive, and is fixed with bolts on the bottom side and the opening side of the casing. .

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