JP5952142B2 - Power control unit - Google Patents

Description

  The present invention relates to a power control unit that is mounted on an electric vehicle and supplies AC power to a traveling motor. The electric vehicle in this specification includes a hybrid vehicle and a fuel cell vehicle including a motor and an engine.

  An electric vehicle requires various electric devices such as an inverter circuit and a voltage converter circuit as devices for driving a motor. On the other hand, since the space (typically the engine compartment) in which these electric devices are mounted is limited, the electric devices are required to be downsized.

  As a measure for reducing the size of an electric device, there is a technique of housing an inverter circuit and a voltage converter circuit in one housing (for example, Patent Document 1). Note that an inverter circuit for an electric vehicle generates a large amount of heat and thus often includes a cooler. In the technique of Patent Document 1, the cooler is also housed in the casing.

JP 2005-032830 A

  If the electric device is downsized, the heat generated by the internal components is likely to enter the inside of the housing, and thus it is necessary to suppress the temperature rise. In particular, a power control unit (including an inverter circuit) that supplies AC power to a traveling motor handles a large current and therefore generates a large amount of heat. Hereinafter, for the sake of simplicity, the “power control unit” is abbreviated as “PCU (Power Control Unit)”.

  By assigning a part of the bus bar (a conductor through which a large current is passed, a conductor made of a rod-shaped metal member, which is usually routed in the PCU housing) to the outside of the PCU, It was proposed to suppress the PCU temperature rise (Japanese Patent Application No. 2011-112071, unpublished at the time of filing this application). The present specification further improves the technology proposed in Japanese Patent Application No. 2011-112071, and when a part of the bus bar is routed outside the PCU housing, the bus bar whose temperature rises due to heat inside the PCU is improved. Provide cooling technology.

  The technology disclosed in this specification is a PCU that supplies AC power to a traveling motor, and is intended for a PCU that includes a cooler for cooling an inverter circuit. In the technology disclosed in this specification, a bus bar that electrically connects a PCU and an external device is routed outside the casing of the PCU, and a part of the bus bar is disposed on the outer surface of the outer wall portion of the casing corresponding to the cooler. Contact. By adopting such a structure, the bus bar can be actively cooled. The housing outer wall portion corresponding to the cooler is an outer wall portion located in the vicinity of the cooler. More specifically, “contacting a part of the bus bar with the outer surface of the outer wall part of the housing corresponding to the cooler” means that a part of the bus bar and the cooler face each other across the outer wall of the housing, This corresponds to arranging the bus bar so that the bus bar and the cooler are in contact with the outer wall of the housing.

  In another aspect of the technology disclosed in this specification, a resin having a higher thermal conductivity than that of the material of the covering material may be embedded in a portion in contact with the casing portion of the covering material that covers the bus bar. By interposing a material having high thermal conductivity between the bus bar and the outer wall of the housing, the bus bar can be efficiently cooled.

  An example of a more specific aspect of the PCU includes a step-down circuit that steps down the output voltage of the main battery that stores electric power for the motor, and the cooler includes a switching element (typically an IGBT) of the inverter circuit. It is to be cooled. An example of a more specific aspect of the bus bar is a part of the conductive material for supplying the output of the step-down circuit to a low voltage battery (auxiliary battery) whose output voltage is lower than that of the main battery. The step-down circuit is a circuit that generates a large amount of heat, and the temperature of the bus bar rises due to the heat of the step-down circuit. A cooler facing the bus bar across the outer wall of the housing effectively cools the bus bar.

  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 electric vehicle of an Example. It is a perspective view of an example cooler. It is a typical external view of PCU. It is sectional drawing of the housing | casing side wall and bus bar of PCU.

  The PCU 2 (power control unit) of the embodiment will be described with reference to the drawings. The PCU 2 is a device mounted on a hybrid vehicle including two motors and an engine as driving forces. First, the power system of the hybrid vehicle 1 including the PCU 2 will be described. FIG. 1 shows a block diagram of a power system of the hybrid vehicle 1. In the hybrid vehicle 1, the drive shafts of the two motors 45, 46 and the drive shaft of the engine 43 are connected to the power distribution mechanism 44, and the output of the power distribution mechanism 44 is driven through the axle 47 and the differential 48 to drive wheels 49. Is transmitted to. Although a detailed description is omitted, the power distribution mechanism 44 is constituted by a planetary gear, and the output of the engine 43 and the outputs of the two motors 45 and 46 are appropriately combined / distributed and transmitted to the axle 47. In some cases, the power distribution mechanism 44 transmits the output of the engine 43 to the output shaft of one motor 45. In this case, the motor 45 is driven by the engine 43 and functions as a generator. Further, when the driver steps on the brake pedal, the power distribution mechanism 44 interlocks the axle 47 with the motor 45. In this case, the motor 45 rotates by obtaining a driving force from the kinetic energy of the vehicle. Generating electricity using the kinetic energy of the vehicle is generally called “regeneration”.

  The power system of the hybrid vehicle 1 mainly includes a main battery 40, a low voltage battery (auxiliary battery) 41, and a PCU (power control unit). In addition, for example, a system main relay is provided between the main battery 40 and the PCU 2. There are other devices that constitute the power system, but the description thereof is omitted here.

  The main battery 40 is a battery that stores electric power for driving the motor, and its output voltage is, for example, 300 volts. The low voltage battery 41 is a battery for supplying power to a device that is driven at a voltage lower than the output voltage of the main battery 40, such as a room lamp or a car navigation system, and the output voltage thereof is, for example, 12 volts. Devices that are driven at a low voltage, such as room lamps and car navigation systems, are sometimes collectively referred to as “auxiliaries”. Therefore, the “low voltage battery” is sometimes called an “auxiliary battery”. The control board 34 built in the PCU 2 also corresponds to an auxiliary machine.

  The PCU 2 includes a step-up / down converter 33, a step-down converter 37, two inverter circuits 35 and 36, two capacitors 31 and 32, and a control board 34. The main battery 40 is connected to the step-up / down converter 33 and the step-down converter 37. In other words, the output power of the main battery 40 is input to the step-up / down converter 33 and the step-down converter 37, respectively. The above device is stored in the housing of the PCU 2.

  The step-up / step-down converter 33 boosts the output voltage of the main battery 40 to a voltage suitable for driving the motor (for example, 600 volts). Further, the step-up / down converter 33 steps down the electric power to the voltage of the main battery 40 when the motor 45 generates power.

  The step-down converter 37 steps down the output voltage of the main battery 40 to a voltage suitable for charging the low voltage battery 41. The high voltage side of the step-down converter 37 is connected to the main battery 40, and the low voltage side is connected to the power line 42 of the auxiliary battery 41 via the repeaters 38 and 39. Although various auxiliary machines are connected to the power line 42, the letters “to AUX” in FIG. 1 simply indicate that various auxiliary machines are connected. The repeaters 38 and 39 are boxes installed on the side surface of the casing of the PCU 2, and a bar-shaped metal material is used as a conductor connecting between them. The rod-shaped metal member corresponds to the bus bar 4. The repeater 38 is a box for connecting the electric cable (bus bar) inside the PCU 2 and the bus bar 4 routed outside the casing of the PCU 2, so in FIG. A repeater 38 is drawn on the boundary of the rectangle to be represented. The repeaters 38 and 39 and the bus bar 4 will be described later.

  Capacitors 31 and 32 are connected to the low voltage side (side connected to the main battery 40) and the high voltage side (side connected to the inverter circuits 35 and 36) of the step-up / down converter 33, respectively. These capacitors are provided to suppress current pulsation (so-called current smoothing).

  Two inverter circuits 35 and 36 are connected to the high voltage side of the buck-boost converter 33 via a capacitor 32. The inverter circuits 35 and 36 convert the boosted DC power into AC power suitable for driving the motor, and supply the AC power to the motors 45 and 46, respectively. The inverter circuits 35 and 36 have a circuit configuration in which three sets of series connection circuits of two switching circuits (typically transistors such as IGBTs and diodes connected in antiparallel thereto) are connected in parallel.

  The step-up / step-down converter 33 and the step-down converter 37 also include a switching circuit like the inverter circuit. The switching circuit included in the step-up / down converter 33, the step-down converter 37, and the two inverter circuits 35, 36 is controlled by a controller mounted on the control board 34. Specifically, the controller generates a PWM signal to be applied to the gates of the transistors of the switching circuit and supplies the PWM signals to each transistor. Since detailed circuit configurations of the step-up / step-down converter, the step-down converter, and the inverter circuit are well known, detailed description thereof will be omitted.

  Electric motors have a large output, and the inverter circuit handles a large current, so it generates a lot of heat. In particular, the switching circuit generates a large amount of heat, and thus the PCU 2 includes a cooler for cooling the switching circuit. FIG. 2 shows the structure of the cooler 3. The cooler 3 has a structure in which a plurality of packages 13 in which two transistors (IGBT) and two diodes are molded with resin, and a plurality of cooling plates 12 through which a coolant passes are alternately stacked. Although it should also be called a power unit, in this specification, since the focus is on the cooler, the above laminate is referred to as the cooler 3.

  The structure of the cooler 3 will be outlined. The package 13 is formed by sealing two transistors (IGBT) 15 and two diodes 16 with resin. Inside the package 13, the two transistors 15 are connected in series. Each of the two diodes 16 is connected to the transistor 15 in antiparallel. An antiparallel circuit of a transistor and a diode corresponds to a switching circuit. That is, the package 13 includes a circuit configuration in which two switching circuits are connected in series. Three metal plate-like terminals 17 extend below the package 13. They are a terminal connected to the high voltage side in series connection of two switching circuits, a terminal connected to the low voltage side, and a terminal connected in the middle of the series connection. Since a large current flows through these terminals 17, a metal plate is used. A control line 18 connected to the gate of the IGBT extends on the upper side of the package 13. The current supplied to the gate (that is, the PWM signal) is much smaller than the current flowing through the emitter and collector (current for driving the motor), and therefore, a thin metal wire is used for the control line 18.

  As described above, the inverter circuit has a structure in which three sets of series connection of two switching circuits are connected in parallel, and each package 13 constitutes one series circuit. 13 constitutes one inverter circuit. As shown in FIG. 2, six packages 13 are stacked in the cooler 3, of which three packages 13 correspond to one inverter circuit 35 and the remaining three packages 13 are the other. It corresponds to the inverter circuit 36. Note that the step-up / down converter 33 and the step-down converter 37 also include a switching circuit, and a package incorporating the switching circuit of the step-up / down converter 33 or the step-down converter 37 may be stacked together with the inverter circuit package.

  The package 13 is sandwiched between adjacent cooling plates 12 with ceramic insulating plates 19 on both sides. The cooling plate 12 has a coolant passing through it, and the two cooling plates 12 cool the package 13 from both sides. Adjacent cooling plates 12 are connected by two pipes (connection pipes), and a pipe 14 for supplying and discharging refrigerant is connected to the cooling plate 12 at one end of the laminate. The refrigerant supplied from one pipe 14 reaches all the cooling plates 12 through one connection pipe. The refrigerant that has taken heat from the package 13 across the cooling plate 12 is discharged through another connecting pipe and pipe 14.

  FIG. 3 shows an external view of the PCU 2. FIG. 3 is a view of the casing of the PCU as viewed obliquely from below. As described with reference to FIG. 1, the repeaters 38 and 39 are attached to the side surface of the PCU 2. The repeater 38 connects the low voltage side terminal of the internal step-down converter 37 and one end of the bus bar 4. The repeater 39 is a box for connecting a wire harness 51 that connects the other end of the bus bar 4 and the power line of the auxiliary system. In each box, metal plates such as terminals and bus bars are securely connected by bolts.

  The bus bar 4 extends from the repeater 38 on one side surface (first side surface 2a) of the PCU 2, proceeds along the first side surface 2a, curves along the adjacent second side surface 2b, and has its first It continues to the repeater 39 provided on the two side surfaces 2b. The bus bar 4 may originally be routed inside the housing of the PCU 2, but if the housing of the PCU 2 is reduced in size, a space for routing the bus bar inside the housing may not be secured appropriately. . The PCU 2 of the embodiment is in such a situation, and therefore the bus bar 4 is routed outside the housing. By arranging the bus bar 4 outside the casing, the casing of the PCU 2 can be reduced in size accordingly.

  As described above, the step-up / down converter 33, the step-down converter 37, the two inverter circuits 35 and 36, the two capacitors 31 and 32, and the control board 34 are stored in the casing of the PCU 2. As described above, the switching circuit which is a main component of the inverter circuits 35 and 36 is included in the cooler 3. That is, the cooler 3 shown in FIG. 2 is also built in the PCU 2. In FIG. 3, the cooler 3 shown in FIG. 2 is shown as a simple rectangular parallelepiped. The bus bar 4 is routed so as to be in contact with a housing outer wall portion corresponding to the cooler 3. In other words, the cooler 3 faces the bus bar 4 with the casing outer wall of the PCU 2 interposed therebetween. FIG. 4 is a cross-sectional view taken along the line VI-VI in FIG. The cooler 3 is in contact with the inner surface of the outer wall 21 of the PCU 2, and the bus bar 4 is in contact with the outer surface of the outer wall 21 (the first side surface 2a described above).

  The bus bar 4 is covered with an insulating covering material 5. A resin plate 6 is embedded in a part of the covering material 5 that covers the bus bar 4. The resin plate 6 is embedded in a portion facing the housing (outer wall 21) of the PCU 2. The resin plate 6 is made of a resin whose thermal conductivity is higher than that of the covering material 5.

  The features and advantages of the PCU 2 will be described. The PCU 2 routes the bus bar 4 outside the casing in order to reduce the size of the entire casing. One end of the bus bar 4 is connected to the output terminal (low voltage side terminal) of the step-down converter 37, and the output of the step-down converter 37 is a low voltage battery 41 (auxiliary battery) whose output voltage is lower than that of the main battery 40. It is a conductive material for supplying to. The bus bar 4 is easy to transfer the heat of the step-down converter 37, and therefore tends to become high temperature. Therefore, the bus bar 4 is routed so that a part of the bus bar 4 faces the cooler 3 across the outer wall 21 of the casing on the outer side of the casing of the PCU 2. As described above, both the cooler 3 and the bus bar 4 are in contact with the housing outer wall 21. Due to the layout of the bus bar 4, the bus bar 4 is effectively cooled by the cooler 3. In particular, in the covering material 5 covering the bus bar 4, a resin plate 6 having a higher thermal conductivity than that of the material of the covering material 5 is embedded in a portion in contact with the housing outer wall 21. The resin plate having a high thermal conductivity promotes cooling of the bus bar 4.

  Points to be noted regarding the technology described in the embodiments will be described. The resin plate 6 having high thermal conductivity may be provided so as to surround the bus bar 4. Further, instead of the resin plate 6, a resin in which a resin having a higher thermal conductivity than that of the original material of the covering material is mixed with the covering material may be used. For example, it is also suitable to use the material of the covering material 5 in which resin powder having a high thermal conductivity is mixed with the original insulating covering material.

  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.

1: Hybrid vehicle 2: Power control unit (PCU)
2a, 2b: PCU side surface 3: cooler 4: bus bar 5: coating material 6: resin plate 12: cooling plate 13: package 14: pipe 21: outer wall 31, 32: capacitor 33: buck-boost converter 34: control board 35, 36: inverter circuit 37: step-down converter 38, 39: repeater 40: main battery 41: auxiliary battery

Claims (4)

It is a power control unit that supplies AC power to the motor for running,
Built-in cooler to cool the inverter circuit,
A bus bar that electrically connects the power control unit and other devices is routed outside the power control unit, and a part of the bus bar is in contact with the outer surface of the outer wall portion of the housing corresponding to the cooler. Power control unit characterized by that.   2. The power control unit according to claim 1, wherein a resin having a higher thermal conductivity than a material of the covering material is embedded in a portion of the covering material that covers the bus bar that contacts the outer wall portion of the casing.   The power control unit according to claim 1, wherein a part of the bus bar and the cooler are opposed to each other with an outer wall of the housing interposed therebetween. The power control unit includes a step-down circuit that steps down the output voltage of the main battery that stores electric power for the motor.
The cooler cools the switching element of the inverter circuit,
The said bus bar is a part of electrically-conductive material for supplying the output of a pressure | voltage fall circuit to the low voltage battery whose output voltage is lower than a main battery, The any one of Claim 1 to 3 characterized by the above-mentioned. Power control unit.

Images