JP2013066259A - Electric power conversion apparatus for electric vehicle and electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power conversion apparatus for an electric vehicle which suppresses the temperature increase of a circuit board controlling a switching element.SOLUTION: An electric power conversion apparatus 10 includes: a reactor 8; a power module 22 housing a switching element SW; a cooler 25; and a circuit board 3 where a circuit controlling the switching element is mounted. The cooler 25 is integrated with the power module 22 to form a PE unit 20. The electric power conversion apparatus 10 includes a first bracket 5 and a second bracket 6. The first bracket 5 supports the circuit board 3 and supports the PE unit 20 so that the PE unit 20 is positioned below the circuit board 3. One end of the second bracket 6 is fixed to the cooler 25 and the second bracket 6 supports the reactor 8 so that the reactor 8 is positioned below the circuit board 3. The first bracket 5 does not directly contact with the second bracket 6, and heat of the reactor 8 is not easily transmitted to the circuit board 3.

Description

  The present invention relates to a power conversion device that converts battery power into power suitable for a traveling motor, and an electric vehicle equipped with the power conversion device. The “electric vehicle” in this specification includes a hybrid vehicle and a fuel cell vehicle.

  Since a vehicle drive motor for an electric vehicle outputs a large torque, a large amount of current is required. For this reason, the power conversion device that converts the power of the main battery into power suitable for driving the motor also handles a large current and generates a large amount of heat. On the other hand, vehicle devices are also required to be compact. Electric power converters for electric vehicles are required to be both heat-resistant and compact. Note that the power conversion device is typically an inverter that converts direct current to alternating current, or a combination of an inverter and a voltage converter that converts the voltage of direct current power to a different voltage.

  Among the power conversion devices, the heat source is particularly a switching element (a so-called power transistor such as an IGBT or a power element such as a free wheel diode connected in parallel thereto) and a reactor. As is well known, the reactor is in a power conversion device and forms a voltage conversion circuit together with a switching element. Patent Document 1 proposes a power conversion device in which a switching element, a reactor, and a cooler for cooling them are housed in a compact manner. The cooler of the power converter has a plurality of flat refrigerant passages, and has a structure in which a plurality of flat power modules containing switching elements and refrigerant passages are alternately stacked. The reactor is sandwiched between two outermost adjacent refrigerant passages. That is, in the power converter, a reactor and a plurality of power modules are sandwiched between flat refrigerant passages. The reason why the switching element is separated from other circuits (such as a circuit for controlling the switching element) as a power module is to cool the switching element intensively.

JP 2010-225723 A

  In recent years, the performance of electric vehicles, in particular, hybrid vehicles has been improved, and the motors mounted on them have also become high output. The power conversion apparatus is further increased in current, and accordingly, a higher cooling capacity is required than ever. On the other hand, compactness is also required for in-vehicle devices. On the other hand, the power conversion device includes a circuit board on which a circuit for controlling a switching element in the power module is mounted in addition to the power module. The circuit board is disposed in the vicinity of the power module in order to minimize the power loss between the power module and the circuit board and the switching element on the circuit board are preferably mounted on a single board. Are mounted on separate boards for cooling the switching elements). In order to make the entire power conversion device compact, the circuit board is naturally close to the reactor. According to the inventors' investigation, it has been found that the circuit board is not a large heat source, but if the ambient temperature rises due to the heat generated by the power module or the reactor, the heat damage to the circuit board cannot be ignored. The present specification solves the above problems. The technology disclosed in this specification provides a technology for suppressing a temperature rise of a circuit board that controls a switching element in a power conversion device.

  In the technology disclosed in this specification, the cooler cools not only the power module but also the reactor and the circuit board, but separates the heat transfer path from the reactor to the cooler and the heat transfer path from the circuit board to the cooler, Makes it difficult for heat to accumulate around the circuit board. Since the member that mainly supports the component can be a heat transfer path, the technology disclosed in this specification completely separates the bracket that supports the cooler and the circuit board and the bracket that supports the reactor so that the heat transfer path is separated. To separate. The technology disclosed in the present specification separates the heat transfer path between the reactor and the circuit board by adopting two brackets, and suppresses the temperature rise of the circuit board. The “bracket” is a term generally indicating a member for fixing a component (in this case, a reactor or the like). It should be noted that there are no particular restrictions on the shape other than the shape described in the specification.

  A power conversion device that is an object of the technology disclosed in this specification includes a circuit board on which a reactor, a power module containing a switching element, and a circuit that controls the switching element are mounted. Here, the “power module” means a substrate in which elements (IGBTs and freewheeling diodes) to be intensively cooled from among the circuits of the voltage converter and the inverter are made independent of other control circuits. One aspect of the power conversion device disclosed in this specification includes a cooler and first and second brackets. The cooler is integrated with the power module. This is because the most important element to be cooled is the switching element. Hereinafter, a unit in which a power module containing a switching element and a first cooler that cools the power module are integrated is referred to as a power element unit, abbreviated as a PE unit. The first bracket supports the circuit board and supports the PE unit so as to be positioned below the circuit board. One end of the second bracket is fixed to the cooler, supports the reactor so as to be positioned below the circuit board, and covers the top of the reactor. Here, the first bracket and the second bracket are not in direct contact with each other. In the following, the portion of the second bracket that covers the top of the reactor is referred to as a “covering portion”.

  The heat of the circuit board is transferred to the cooler through the first bracket. The heat of the reactor is transferred to the cooler through the second bracket. Since the first bracket and the second bracket are not in direct contact with each other, the heat of the reactor is hardly transmitted to the circuit board. In addition, the ambient air is also heated by the heat of the reactor, but the covered portion of the second bracket covers the upper portion of the reactor, so that the heated air is difficult to move above the covering portion. Although the circuit board is disposed above the cover portion, the air heated by the heat of the reactor is difficult to reach the circuit board. With the above configuration, the temperature rise of the circuit board is suppressed.

  In another aspect of the power conversion device disclosed in the present specification, it is preferable that a gap is secured between the reactor cover portion of the second bracket and the circuit board. Since the air gap also has a heat insulating effect, providing the air gap makes it difficult for the heat of the reactor to be transmitted to the circuit board.

  In the power conversion device disclosed in the present specification, an insulating sheet may be further disposed between the inside of the cover portion and the reactor. By arrange | positioning an insulating sheet, the clearance gap between a cover part and a reactor can be narrowed. Thereby, the whole power converter device can be made compact. Or the thickness of a cover part can be thickened by the part which narrowed the clearance gap between a cover part and a reactor, and the thermal conductivity of a cover part can be raised.

  One aspect of the cooler has a structure in which a plurality of flat refrigerant passages are arranged in parallel. Each of the plurality of flat power modules is sandwiched between adjacent flat refrigerant passages to form a laminate. At this time, the first bracket may support the laminated body sandwiched from both sides. Moreover, it is good for the end of a 2nd bracket to be fixed to the flat refrigerant path located in the end of a laminated body. That is, the flat refrigerant passage located at the end of the laminated body mainly contributes to the cooling of the reactor and the cooling of the circuit board. The other flat refrigerant passage can be dedicated to cooling the power element module (switching element). Separating the flat refrigerant passage responsible for cooling the power element module and the flat refrigerant passage responsible for cooling the reactor / circuit board facilitates heat transfer simulation and facilitates thermal design. The ease of thermal design means that precise thermal design is possible, and improvement in cooling efficiency can be expected.

  The above power conversion device is also advantageous in being mounted on an electric vehicle in combination with a drive train having an inclined upper surface. That is, the power converter is preferably fixed to the inclined upper surface so that the PE unit is located on the lower side and the reactor is located on the higher side. When the reactor is positioned on the higher side, the warm air inside the case of the power conversion device collects above the reactor. However, in the above power converter, the heat of the reactor is efficiently radiated from the lower side of the reactor, so that the heat remaining inside the case is reduced, and it is difficult for the heat to be accumulated above the reactor. And since a 2nd cooler is located in the bottom part of a power converter device, the thermal interference with a reactor or PE unit, and a drive train can be interrupted | blocked.

It is a side view of the power converter device of an Example. It is a top view of the power converter device of an Example. It is a typical perspective view of a PE unit. It is a side view of the power converter device of a modification. It is a perspective view which shows the device layout in an engine compartment. It is a typical side view of a drive train carrying a power converter.

  A power conversion device 10 according to an embodiment will be described with reference to the drawings. Although FIG. 1 is a side view, in order to help understanding, FIG. 1 depicts the case 4 and its cover 2 in cross section (hatched), and the parts inside the case are depicted as side views. FIG. 2 is a plan view, but shows a state where the cover 2 and the circuit board 3 located above the power converter 10 are removed.

  The electric power converter 10 includes a voltage converter that converts battery voltage and an inverter that converts direct current to alternating current in terms of electrical circuits. Specifically, the electric circuit of the voltage converter and the inverter includes a reactor 8, a smoothing capacitor 9, a switching element SW in the plurality of power modules 22, and a circuit board 3 that controls the switching elements SW in the power module 22. Consists of. As is well known, a reactor is in a power conversion device and forms a voltage conversion circuit together with a switching element. Both the voltage converter and the inverter have a plurality of switching circuits in which a power transistor and a free-wheeling diode are connected in parallel. A power transistor and a free wheel diode constituting the switching circuit correspond to the switching element SW. One or two switching circuits are mounted on one independent substrate, which is referred to as one power module 22. 1 to 3 illustrate only six power modules for easy understanding of the drawings, the power conversion apparatus 10 may include more power modules. As other members constituting the power conversion device 10, there are a cooler 25 that cools the power module 22, a first bracket 5, and a second bracket 6. The cooler 25 also cools the reactor 8 and the circuit board 3. The first bracket 5 is a member that supports the unit (PE unit) of the circuit board 3, the cooler 25, and the power module 22 with respect to the case 4. The second bracket 6 is a member that connects the cooler 25 and the reactor 8. The second bracket 6 supports the reactor 8 with respect to the cooler 25.

  The cooler 25 and the power module 22 are integrated, and this is referred to as a PE unit 20. The PE unit 20 will be described. FIG. 3 shows a schematic perspective view of the PE unit 20. In the cooler 25, two pipes 29a and 29b pass through a plurality of flat refrigerant passages 21, and support the plurality of refrigerant passages 21 so that they are arranged in parallel. The two pipes 29a and 29b and the respective refrigerant passages 21 communicate with each other, and the refrigerant supplied from one pipe 29a passes through each refrigerant passage 21 and is discharged from the other pipe 29b. The refrigerant may typically be water. The power module 22 containing the switching element SW is sandwiched between two adjacent refrigerant passages. That is, the PE unit 20 is configured by alternately laminating a plurality of flat power modules 22 and a plurality of flat refrigerant passages 21 of the cooler 25. In the PE unit 20, since the refrigerant passes through both surfaces of the flat power module 22, the switching element SW can be efficiently cooled. A lead wire 22a extends from each power module 22 (switching element SW). The lead wire 22a is connected to the circuit board 3 as shown in FIG. A flat refrigerant passage corresponding to the rear end of the PE unit 20 is particularly denoted by reference numeral 21e.

  Returning to FIG. 1 and FIG. The smoothing capacitor 9, the PE unit 20, and the circuit board 3 are supported by the first bracket 5. The reactor 8 is supported by the second bracket 6. The smoothing capacitor 9, the PE unit 20, the circuit board 3, and the reactor 8 are supported by any bracket and accommodated in the case 4. The first bracket 5 is fixed above the case 4 and is pressed and fixed by the cover 2 from above. As shown in FIG. 2, the first bracket 5 surrounds the PE unit 20 and the reactor 8 when viewed in plan.

  As shown in FIG. 1, the PE unit 20 is fixed by being sandwiched between two stays 5 b extending downward from the first bracket 5. That is, the PE unit 20 is supported by the first bracket 5 from above. In FIG. 1, a spring 13 is inserted between the left stay 2b and the end of the PE unit 20, and this spring 13 urges the PE unit 20 between the two stays 5b to fix it. doing. The spring 13 presses the refrigerant passage 21 and the power module 22 in the stacking direction, whereby the refrigerant passage 21 and the power module 22 are firmly adhered, and the heat of the power module 22 is well transmitted to the refrigerant passage 21. Is done.

  A circuit for controlling elements in the power module 22 is mounted on the circuit board 3. The circuit board 3 is supported above the PE unit 20 and the reactor 8 by a stay 5 a extending upward from the first bracket 5. As shown in FIG. 1, lead wires 22 a extending from the power module 22 are connected to the circuit board 3.

  The reactor 8 is supported by the second bracket 6. The second bracket 6 includes a stay 6a and a cover 6b, and the end of the stay 6a corresponding to the end of the second bracket 6 is located on the end surface of the end refrigerant passage 21e of the laminate of the PE unit 20. Fixed. A cover 6b is connected to the tip of the stay 6a. The cover portion 6 b has a shape in which a rectangular box (container) is turned upside down, and covers almost the upper half of the reactor 8. A stay 6c extends from the ceiling of the cover 6b, and the reactor 8 is supported by the stay 6c. The reactor 8 includes two coils arranged in parallel (one winding) and one core passing through them.

  The first bracket 5 is manufactured by pressing from a single metal plate including the stays 5a and 5b. The second bracket 6 is manufactured by press working from a single metal plate including the stay 6a, the cover 6b, and the stay 6c.

  The PE unit 20 and the reactor 8 are supported by the second bracket 6 so as to be adjacent to each other with a gap Sp1 therebetween. Further, the circuit board 3 is supported above the PE unit 20 by the first bracket 5. As well shown in FIG. 1, the circuit board 3 is disposed above the reactor 8 (above the cover 6b) with a gap Sp2 therebetween. As well shown in FIG. 1, the second bracket 6 is in contact with the end refrigerant passage 21 e of the cooler 25 and the reactor 8 and is not in contact with other members. Moreover, the reactor 8 is only in contact with the cover portion 6b (stay 6c) of the second bracket 6 and a bus bar 7 (described later), and is not in contact with other members.

  As shown well in FIG. 2, four smoothing capacitors 9 are arranged on the side of the PE unit 20 and the reactor 8. The smoothing capacitor 9 is for smoothing the current flowing through the reactor 8. Voltage conversion (step-up or step-down) is achieved by chopping the current flowing through the reactor 8. Each time chopping, the current flowing through the reactor 8 pulsates, but the smoothing capacitor 9 suppresses the pulsation. The capacitor 9 is also supported by the first bracket 5. Reactor 8 and capacitor 9 are electrically connected by bus bar 7. The bus bar 7 exits from below the reactor 8, passes through the side of the reactor 8, and reaches the capacitor 9.

  The advantages of the structure of the power conversion device 10 will be described. The cooler 25 of the power conversion apparatus 10 mainly cools the power module 22, but also cools the circuit board 3 and the reactor 8. The heat of the circuit board 3 is transmitted to the cooler 25 through the first bracket 5. Further, the heat of the reactor 8 is transmitted to the cooler 25 through the second bracket 6. The first bracket 5 and the second bracket 6 are both made of metal plates and have good thermal conductivity. Since the second bracket 5 and the second bracket 6 are not in contact with each other, the heat transfer paths do not cross each other. In particular, the heat of the reactor 8 is not transmitted to the circuit board 3. Although the reactor 8 is adjacent to the circuit board 3 above the reactor 8, the upper part of the reactor 8 is covered with the covering portion 6 b of the second bracket 6, so that the ambient air heated by the reactor 8 is There is no flow around. Further, the gap Sp1 between the reactor 8 and the PE unit 20 and the gap Sp2 between the reactor 8 (covering portion 6b) and the circuit board 3 are also transferred from the reactor 8 and the heat transfer from the circuit board 3. It contributes to separating the path. As described above, the power conversion device 10 realizes a structure in which the heat of the reactor 8 is not easily transmitted to the circuit board 3. That is, the circuit board 3 is thermally protected by the above-described structure.

  Next, a modified example of the power conversion device will be described. FIG. 4 is a side view of a power converter 110 according to a modification. In addition to the configuration of the power conversion device 10 in FIG. 1, the power conversion device 110 includes an insulating sheet 112 disposed between the reactor 8 and the inside of the cover 6b. By disposing the insulating sheet 112, the gap between the cover 6b and the reactor 8 can be narrowed. Thereby, the whole power converter device can be made compact. Or the thickness of the cover part 6b can be thickened by the part which narrowed the clearance gap between the cover part 6b and the reactor 8, and the thermal conductivity of the cover part 6b can be raised. The insulating sheet 112 is preferably made of a material having a high thermal conductivity.

  An automobile 90 equipped with the power conversion device 10 will be described with reference to FIGS. 5 and 6. The automobile 90 is a hybrid car equipped with an engine EG and a motor. The automobile 90 is equipped with a power converter 10 (inverter) for driving a motor. The power conversion device 10 is mounted in the engine compartment EC together with the engine EG and the drive train 50. The engine EG and the drive train 50 are arranged behind the radiator RT. The engine EG and the drive train 50 are arranged side by side in the horizontal direction. A battery BT is disposed on the side of the drive train 50. The drive train 50 incorporates two motors MG1 and MG2 and a transmission TM that transmits the output of the power source (engine and motor) to the axle. The output shaft of the engine EG is also engaged with the transmission TM. As shown in FIG. 6, in the drive train 50, a total of three main shafts including the output shafts 51 and 52 of the two motors MG1 and MG2 and the main shaft 53 (corresponding to the engine output shaft) of the transmission TM are provided. It is parallel. As shown in FIG. 6, the motor MG1 is located slightly above. The two motors MG1, MG2 and the transmission TM are arranged in such a direction that three shafts extend in the lateral direction of the vehicle (Y-axis direction in the figure). With such an arrangement of the two motors MG1, MG2 and the transmission TM, the drive train 50 is low on the front side of the vehicle (in the figure, the positive direction of the X axis) and on the rear side of the vehicle (in the figure, in the negative direction of the X axis). Has an inclined upper surface 50a. The power converter 10 is fixed to the inclined upper surface 50a. The power conversion device 10 is fixed to the inclined upper surface 50a so that the PE unit 20 is located on the lower side (vehicle front side) and the reactor 8 is located on the higher side (vehicle rear side). Therefore, the pipe 29 that passes the refrigerant to the cooler 25 protrudes from the side surface of the power conversion device 10 on the vehicle front side. A refrigerant pipe 55 is connected to the pipe 29. The refrigerant is supplied to the cooler 25 through the refrigerant pipe 55 and discharged from the cooler 25.

  The power converter 10 is located on the side where the reactor 8 is high, and the circuit board 3 is located thereon. Hot air moves upward in the power converter 10. Here, since the upper part of the reactor 8 is covered with the cover part 6b of the second bracket 6, the heat generated by the reactor 8 stays inside the cover part 6b, and around the circuit board 3 positioned above the cover part 6b. Not reach. Therefore, the circuit board 3 is thermally protected.

  Points to be noted regarding the power conversion device 10 according to the embodiment will be described. The PE unit 20 is supported from above by the first bracket 5, and the reactor 8 is supported from above by the second bracket 6. The PE unit 20 and the reactor 8 may be supported from the side thereof. The PE unit 20 and the circuit board 3 are supported by the case 4 via the first bracket 5 and are thermally separated from the case 4. The reactor 8 is supported by the second bracket 6 with respect to the PE unit 20 and is also thermally separated from the case 4.

  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: Cover 3: Circuit board 4: Case 5: First bracket 6: Second bracket 6a, 6c: Stay 6b: Cover 7: Bus bar 8: Reactor 9: Smoothing capacitor 10: Power converter 13: Spring 20: Power Element unit (PE unit)
21: Refrigerant passage 22: Power module 25: Cooler 50: Drive train 50a: Inclined upper surface 90: Automobile 110: Power conversion device 112: Insulation sheet EC: Engine compartment EG: Engines MG1, MG2: Motor TM: Transmission

Claims (5)

A power conversion device for an electric vehicle,
Reactor,
A power module containing a switching element;
A cooler integrated with the power module;
A circuit board on which a circuit for controlling the switching element is mounted;
A first bracket supporting the circuit board and supporting the power module and the cooler unit so as to be positioned below the circuit board;
A second bracket having one end fixed to the cooler, supporting the reactor so as to be positioned below the circuit board, and covering the top of the reactor;
With
The power conversion device, wherein the first bracket and the second bracket are not in direct contact with each other.   The power converter according to claim 1, wherein a gap is secured between the reactor covering portion of the second bracket and the circuit board.   The power converter according to claim 1 or 2, wherein an insulating sheet is disposed between the reactor and the inside of the reactor cover. The cooler has a structure in which a plurality of flat refrigerant passages are arranged in parallel,
Each of the flat-type power modules is sandwiched between adjacent flat-type refrigerant passages,
The first bracket supports a laminated body of a plurality of flat refrigerant passages and a plurality of power modules sandwiched from both sides,
4. The power conversion device according to claim 1, wherein one end of the second bracket is fixed to a flat refrigerant passage located at an end of the stacked body. 5. The power conversion device according to any one of claims 1 to 4, wherein the power conversion device converts the battery power into power suitable for a traveling motor;
A drive train having an inclined top surface;
With
An electric vehicle characterized in that a power conversion device is fixed to the inclined upper surface so that a unit of a power module and a cooler is located on a low side and a reactor is located on a high side.

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