Electric Drive Unit

Abstract

To achieve an electrical drive unit capable of reducing size and weight and of improving performance.SOLUTION: An inverter 30 is arranged adjacently to one end in a rotation axial direction of a motor 20. The inverter 30 comprises: a plurality of power modules 70 each including a switching element 46; a smoothing capacitor 60; bus bars 80 and 81 connecting them; and a thin case 31 accommodating these components. The plurality of power modules 70 are arranged around the smoothing capacitor 60 side by side in the circumferential direction. The bus bars 80 and 81 are formed so as to extend in the circumferential direction. An inner edge part of the bus bars 80 and 81 to be connected with a terminal of the smoothing capacitor 60 is formed in an arcuate or circular shape.SELECTED DRAWING: Figure 13

Description

[Technical Field]

[0001] The disclosed technology relates to an electric drive unit for a vehicle that includes a motor and an inverter. [Background technology]

[0002] In recent years, hybrid vehicles, electric vehicles, and other vehicles that run on electricity have become increasingly popular. These vehicles are equipped with a drive motor and a battery. The direct current (DC) power supplied from the battery is converted to alternating current (AC) by an inverter, and this AC power is then supplied to the drive motor while being controlled. The vehicle runs on the rotational power generated by this.

[0003] This type of inverter handles large amounts of power, so high voltages are applied and large currents flow through it. Consequently, it generates a lot of heat during operation, requiring cooling. It also generates large surge voltages. This means that the individual electronic components that make up the inverter tend to be large and heavy. Therefore, conventional inverters are a barrier to improving fuel economy and power efficiency.

[0004] In addition, inverters are usually placed near the drive motor to shorten the transmission distance. However, in the case of automobiles, there are many devices to be installed, so the space available for placing the inverter is limited. The balance of the vehicle body also needs to be taken into consideration. For this reason, it is difficult to properly place a large and heavy inverter in an automobile.

[0005] To address this issue, techniques have been proposed to reduce the size and weight of inverters by integrating the inverter with the motor (for example, Patent Document 1).

[0006] In Patent Document 1, the cooling performance of the switching elements by air cooling is improved by devising a structure for the inverter case. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-274992 Summary of the Invention [Problem to be solved by the invention]

[0008] The inverter is equipped with a power module including a switching element, a smoothing capacitor, etc. As mentioned above, in the case of an inverter compatible with a high-voltage power supply, these electronic components are generally large and heavy.

[0009] The metal fittings (bus bars), which are electronic components that connect these components, are also large and heavy because they carry large currents. The longer the bus bar wiring, the higher the electrical resistance becomes, resulting in copper loss when current is passed through them. Bus bars also generate a lot of heat. Furthermore, inverters use switching control to turn large currents on and off at high speeds, which causes large magnetic changes in the bus bars.

[0010] As a result, when the inverter is operating, magnetic changes cause noise, vibration, electromagnetic interference, etc. in the busbars. These result in energy loss and have various adverse effects on the performance of the vehicle. Therefore, measures to address these issues are necessary. The more complex the busbar shape, the more pronounced the effects become.

[0011] In the case of the inverter disclosed in Patent Document 1, although miniaturization can be achieved by integrating the inverter with the motor, the electronic components are the same as those of conventional motors, and therefore there is room for improvement in terms of the structure and arrangement of the electronic components.

[0012] Therefore, the disclosed technology realizes an electric drive unit that is compact, lightweight, and has improved performance by devising the structure and arrangement of the main electronic components that make up the inverter. [Means for solving the problem]

[0013] The disclosed technology relates to an electric drive unit in which an inverter is disposed adjacent to one end of a motor in the direction of a rotation axis.

[0014] The inverter includes a plurality of power modules, each including at least one switching element, that constitute an inverter circuit that converts DC power into AC power; smoothing capacitors that constitute the inverter circuit together with the plurality of power modules; bus bars that connect each of the power modules to the smoothing capacitors; and a thin case that is thin in the direction of the rotation axis and that houses the power modules, the smoothing capacitors, and the bus bars.

[0015] A plurality of the power modules are arranged around the smoothing capacitor in a circumferential direction, and the bus bar is formed to extend in the circumferential direction, with the inner edge portion of the bus bar connected to the terminal of the smoothing capacitor being formed in an arc or circle extending in the circumferential direction.

[0016] In this electric drive unit, the inverter has a thin case with a small thickness in the direction of the rotation axis and is disposed adjacent to one end of the motor in the direction of the rotation axis, thereby realizing a compact and lightweight electric drive unit.

[0017] The motor and inverter must be connected by multiple bus bars (output bus bars), but by locating the inverter adjacent to one end of the motor in the direction of the rotation axis, the wiring length can be shortened and the inductance of the output bus bars can be reduced. Furthermore, because the motor and inverter are arranged coaxially, locating the output bus bars in line with the motor can make the wiring lengths more uniform. This allows the inductance of each output bus bar to be leveled out, improving motor controllability.

[0018] In this electric drive unit, the shapes and arrangement of the power module, smoothing capacitor, and bus bar, which are the main electronic components that make up the inverter circuit, have been devised so that they can be housed in the thin case described above, which would have been difficult to house in the past.

[0019] That is, the power modules are arranged in a circumferential direction around the smoothing capacitor, which allows these electronic components to be arranged efficiently and reduces the installation space.

[0020] The busbars connecting these electronic components are formed to expand circumferentially to accommodate the spaces between the electronic components, so the width of the busbars is larger than the length required to connect these electronic components. This allows the wiring length of the busbars to be shortened and the width of the busbars perpendicular to the wiring length to be increased. This effectively reduces the inductance of the busbars. The large surface area of ​​the busbars also improves heat dissipation, thereby improving the performance of the electric drive unit.

[0021] Furthermore, because the inner edge of the busbar connected to the terminal of the smoothing capacitor is formed in a circumferentially extending arc or circle, the shortest length from the terminal of each power module aligned circumferentially to its inner edge can be made substantially the same at any location. Therefore, by connecting the inner edge to the smoothing capacitor, the wiring length of each power module can be made more uniform. This allows the inductance between each power module and the smoothing capacitor to be leveled, improving motor controllability.

[0022] The electric drive unit may also be configured such that the thin case has an outer shape formed in a disk shape corresponding to the motor.

[0023] This will enable the realization of a compact and lightweight electric drive unit, which will greatly increase the degree of freedom in automobile design and enable the realization of high-performance automobiles. It is also suitable for in-wheel motors, etc.

[0024] The electric drive unit may also be configured such that the smoothing capacitor and the power module are each formed in a flat shape having an installation surface on one side, and are placed on a common support surface via the installation surface.

[0025] If the smoothing capacitor and power module are each formed in a flat shape and mounted on a common support surface via the installation surface on one side of the module, the inverter thickness can be further reduced. Since all of these electronic components are aligned on the common support surface, the height from the support surface can be minimized. Therefore, even a thin case with a small thickness in the direction of the rotation axis can accommodate these electronic components.

[0026] The flat shape provides a large area for these electronic components, allowing them to dissipate heat more effectively, thereby improving the performance of the electric drive unit.

[0027] The electric drive unit may also be configured such that the busbar includes a plate-shaped third busbar that extends in a fan shape along an upper surface of each of the power modules, and the third busbar is connected to one of the positive and negative terminals of each of the power modules and a corresponding terminal of the smoothing capacitor.

[0028] The third bus bar is a plate-like structure that spreads out in a fan shape to accommodate the arrangement of multiple power modules, resulting in a large surface area and excellent heat dissipation. Moreover, because it spreads along the top surface of each power module, it can efficiently cool each power module. The third bus bar is also wide, resulting in low inductance. Its plate shape helps to make the inverter smaller and lighter.

[0029] The electric drive unit may also be configured such that the bus bar is formed in a plate shape extending in a strip shape along and between each of the power modules and the smoothing capacitor, and further includes a first bus bar connected to the other of the positive and negative terminals of each of the power modules and the corresponding terminal of the smoothing capacitor.

[0030] That is, in this electric drive unit, in addition to the third bus bar, the first bus bar, which is connected to one of the positive and negative terminals other than the third bus bar, is formed in a plate shape that extends in a strip-like shape along each of the power modules and the smoothing capacitor.

[0031] Therefore, the first bus bar has a short wiring length and a large width perpendicular to the wiring length, which effectively reduces the inductance of the first bus bar. The plate-like shape contributes to making the inverter smaller and lighter.

[0032] The electric drive unit may also be configured such that each of the power modules has a positive terminal and a negative terminal, includes a half-bridge circuit connected between the positive terminal and the negative terminal with two of the switching elements connected in series, and further has an output terminal connected between the two switching elements.

[0033] This allows the inverter circuit to be configured with multiple circuits, each corresponding to a motor phase, by incorporating each of these power modules. This simplifies the layout design of the electronic components inside the inverter, and helps to reduce the inverter's size.

[0034] The electric drive unit may also be configured such that the switching element is configured with a SiC MOSFET.

[0035] SiC MOSFETs have lower electrical resistance and better heat resistance than IGBTs and power MOSFETs, which are common switching elements of this type. As a result, when compared with IGBTs and power MOSFETs with similar performance, SiC MOSFETs can be made smaller in chip size.

[0036] This allows for the miniaturization of electronic components that incorporate switching elements. In particular, the power module described above incorporates two switching elements connected in series, which allows for more effective miniaturization.

[0037] The electric drive unit may also be configured such that the smoothing capacitor is configured by connecting a plurality of element capacitors in parallel, and the plurality of element capacitors arranged opposite the plurality of power modules are arranged along the alignment of the plurality of power modules.

[0038] To handle high voltages, smoothing capacitors require large capacitance. However, this electric drive unit allows for a high degree of design freedom, as the number of element capacitors can be selected according to the desired capacitance. Furthermore, the external shape of the smoothing capacitor can be freely set by changing the arrangement of these element capacitors. Placing them side by side can help make the inverter thinner.

[0039] Furthermore, by arranging multiple element capacitors aligned opposite multiple power modules along the line of the multiple power modules, the distance between these element capacitors and each of the power modules can be shortened, thereby promoting the reduction and equalization of inductance. [Effects of the Invention]

[0040] An electric drive unit incorporating the disclosed technology can be made smaller and lighter, while also improving performance. Therefore, when installed in a vehicle, it can improve fuel economy and power consumption, and increase the degree of freedom in vehicle design. It can also suppress noise and other issues, enabling the realization of a high-performance vehicle. [Brief explanation of the drawings]

[0041] [Figure 1] 1 is an example of a vehicle to which the disclosed electric drive unit is applied. [Figure 2] 1 is a schematic diagram showing a first electric drive unit installed in a motor vehicle. [Figure 3] FIG. 2 is a schematic diagram for explaining the structure of a motor that constitutes an electric drive unit. [Figure 4] FIG. 1 is a basic circuit diagram of an inverter that constitutes an electric drive unit. [Figure 5] This is a diagram for comparing IGBT and SiC MOSFET chips. [Figure 6] FIG. 2 is a diagram for explaining a power module. [Figure 7] FIG. 4 is a schematic diagram showing the main parts of the inverter of the first electric drive unit. [Figure 8] 8 is a schematic cross-sectional view of a portion indicated by an arrow Y7 in FIG. 7. [Figure 9] FIG. 10 is a schematic diagram showing an illustrative bus bar. [Figure 10] 1 is a graph showing the relationship between the shape (width, length, thickness) of a bus bar and inductance. [Figure 11] FIG. 8 is a view corresponding to FIG. 7 showing an electric drive unit according to a second embodiment. [Figure 12] 12 is a schematic cross-sectional view of a portion indicated by an arrow Y11 in FIG. [Figure 13] FIG. 8 is a view corresponding to FIG. 7 showing an electric drive unit according to a third embodiment. [Figure 14] 14 is a schematic cross-sectional view of a portion indicated by an arrow Y13 in FIG. 13. [Figure 15] 2A and 2B are diagrams for explaining the structure of a main part of an inverter and a power module. [Figure 16] FIG. 10 is a diagram for explaining an electric drive unit according to a fourth embodiment. [Figure 17] FIG. 10 is a view corresponding to FIG. 7 showing an electric drive unit according to a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0042] The disclosed technology will be described below using multiple embodiments. However, the following description is essentially merely an example. The matters described in each embodiment are not limited to that embodiment and may also be applied to other embodiments.

[0043] An electric drive unit using the disclosed technology is suitable as a power source for automobiles that run on electricity, such as hybrid cars, electric cars, etc. Therefore, in the following embodiments, an electric drive unit for an automobile is exemplified.

[0044] FIG. 1 shows a schematic view of an automobile 1 according to this embodiment, seen from below. This automobile 1 is a so-called hybrid vehicle. It is equipped with an engine 2 and a drive motor 20A (an example of a disclosed motor) as its main driving sources. The disclosed technology is not limited to hybrid vehicles, but can also be applied to electric vehicles that run solely on a motor.

[0045] In this automobile 1, an engine room 1a is located at the front of the passenger compartment. An engine 2 is located in this engine room 1a. Rear wheels 3 are the driving wheels. In other words, this automobile 1 is a so-called front-engine, rear-drive (FR) vehicle.

[0046] In addition to the engine 2 and drive motor 20A described above, the automobile 1 is also equipped with first and second inverters 30, an automatic transmission 4, a high-voltage battery 5, a propeller shaft 6, a differential 7, and other drive system devices. The drive motor 20A is integrated with the first inverter 30 (forming the disclosed electric drive unit). The integrated drive motor 20A and first inverter 30 (first electric drive unit 10A) are disposed adjacent to the rear side of the engine 2.

[0047] 2, the drive motor 20A has a front shaft 21 protruding from its front end and a rear shaft 22 protruding from its rear end. The front shaft 21 is connected to the output shaft (crankshaft) of the engine 2 via a clutch or the like (not shown). The rear shaft 22 is connected to the automatic transmission 4.

[0048] As shown in Fig. 1, a floor tunnel 1c that extends in the longitudinal direction and protrudes toward the passenger compartment is provided in the center of the vehicle width direction of a floor panel 1b that forms the floor surface of the passenger compartment. The automatic transmission 4 is housed in the floor tunnel 1c and is disposed adjacent to the rear side of the first electric drive unit 10A. The front end of a propeller shaft 6 is connected to the rear side of the automatic transmission 4.

[0049] The rear end of the propeller shaft 6 is connected to a differential 7. Rotational power output from the engine 2 and the like is transmitted to the rear wheels 3 through wheel shafts 8 extending to the left and right from the differential 7. An exhaust pipe extends to the right of the engine 2, and a catalytic converter 2a is installed upstream of the exhaust pipe. Although not shown, the exhaust pipe extends rearward, and its downstream end is connected to a silencer installed at the rear of the automobile 1.

[0050] In the automobile 1 of this embodiment, an in-wheel motor 20B (an example of a disclosed motor) having a cylindrical outer shape is incorporated into each of the left and right front wheels 9 so that the front wheels 9 can also be driven. The in-wheel motor 20B drives and rotates the corresponding front wheel 9 by itself. The in-wheel motor 20B functions, for example, as an assist motor that generates power and transmits it to the front wheels 9 when the automobile 1 starts moving. When there is no particular distinction between the drive motor 20A and the in-wheel motor 20B, they are also collectively referred to as motor 20.

[0051] A second inverter 30 to which the disclosed technology is applied (forming the disclosed electric drive unit) is integrated with one end in the rotational axis direction of the in-wheel motor 20B of this automobile 1. The integrated in-wheel motor 20B and second inverter 30 (second electric drive unit 10B) are mounted to the body of the automobile 1 with the second inverter 30 side facing inward in the vehicle width direction.

[0052] A high-voltage battery 5 for driving the vehicle is installed on both the left and right sides of the floor tunnel 1c below the floor panel 1b. The high-voltage battery 5 is made up of multiple battery modules connected together, each of which is made up of multiple battery cells (lithium ion batteries, etc.). Because the high-voltage battery 5 has a large capacity, it is formed in a flat shape that extends widely along the floor panel 1b.

[0053] The high-voltage battery 5 supplies DC power to each of the first and second inverters 30 (when no particular distinction is made between these inverters 30, they are simply referred to as inverters 30). The inverters 30 convert the supplied DC power into AC power. The inverters 30 then supply the AC power to the drive motor 20A, causing the rear wheels 3 to rotate, and to the in-wheel motor 20B, causing the front wheels 9 to rotate (so-called power running).

[0054] The automobile 1 also performs regeneration. That is, the drive motor 20A and the in-wheel motor 20B are also used as generators. When the drive motor 20A or the in-wheel motor 20B generates power during vehicle deceleration, the AC power is converted into DC power by the inverter 30. This DC power is then supplied to the high-voltage battery 5, thereby charging the high-voltage battery 5.

[0055] As shown in FIG. 2, unlike conventional inverters, the disclosed inverter 30 is thin and lightweight.

[0056] Specifically, the first inverter 30 is disposed adjacent to one end (rear end) of the drive motor 20A in the direction of the rotation axis (the direction in which the rotation axis J extends in FIG. 2), and they are integrally configured. The drive motor 20A has a cylindrical outer shape centered on the rotation axis J. In contrast, the outer shell of the first inverter 30 is formed by a thin case (thin case 31) and has a disk-shaped outer shape with approximately the same outer diameter as the drive motor 20A. The thin case 31 is assembled to the rear end of the drive motor 20A with its thickness direction aligned with the direction of the rotation axis of the drive motor 20A.

[0057] In this embodiment, the thickness Wiv of the thin case 31 (size in the direction of the rotation axis) is designed to be 50 mm or less. Preferably, the thickness Wiv of the thin case 31 is 30 mm or less. The second inverter 30 integrated with the in-wheel motor 20B is also made thin in the same manner.

[0058] In conventional technology, it is extremely difficult to incorporate the electronic components that make up an inverter into such a thin case, and this has not been possible. In contrast, in the case of the disclosed inverter 30, as will be described later, the shape and layout of the inverter's main electronic components have been devised. This makes it possible to house these electronic components in a thin space, and as a result, it has become possible to realize such a thin and lightweight inverter 30.

[0059] Making the inverter thinner and lighter in this way offers various advantages to the automobile 1 equipped with it. For example, conventional large and heavy inverters are often placed below the floor panel 1b adjacent to the side of the drive motor 20A, as shown by the imaginary line α1 in FIG.

[0060] In such a case, due to height restrictions, the inverter must be flat. This means that a specific large area below the floor panel 1b is occupied by the inverter. Therefore, the conventional high-voltage battery 5 can only be installed within the range indicated by the imaginary line α2. As a result, the layout design of the devices below the floor panel 1b is significantly restricted.

[0061] The inverter can be placed above the drive motor 20A or the automatic transmission 4, but this would increase the size of the floor tunnel 1c, resulting in a problem of a smaller passenger compartment. In contrast, the inverter 30 of the disclosed technology can be installed with almost no restrictions on the automobile 1.

[0062] This increases the degree of freedom in the layout design of the vehicle-mounted device. As a result, as shown in this automobile 1, it becomes possible to increase the capacity of the high-voltage battery 5, thereby improving the performance of the automobile 1. The disclosed inverter 30 also promotes weight reduction, thereby improving fuel efficiency and electricity consumption. Furthermore, as shown in this automobile 1, it becomes easy to combine it with an in-wheel motor 20B, thereby realizing an automobile 1 with higher performance.

[0063] <Motor> FIG. 3 shows a simplified structure of motor 20. Motor 20 is a so-called permanent magnet synchronous motor. A shaft 24 (comprising front shaft 21 and rear shaft 22) is rotatably supported at the center of a cylindrical motor case 25, and a cylindrical rotor 26 is fixed to shaft 24. A permanent magnet 26a is provided on the outer periphery of rotor 26. As a result, a plurality of north and south poles are arranged alternately at equal intervals in the circumferential direction.

[0064] A stator 27 is arranged coaxially around the rotor 26. The stator 27 has a plurality of teeth 27a (six in the illustrated example) that protrude radially at equal intervals from an annular core toward the rotor 26. The tip of each tooth 27a faces the rotor 26 across a gap. A plurality of coils 27b are formed by winding electric wire around each of these teeth 27a.

[0065] These coils 27b constitute a three-phase coil group consisting of U-phase, V-phase, and W-phase. The coils 27b of each phase are arranged alternately in the circumferential direction. The motor 20 is provided with relay terminals 28 for each of the U-phase, V-phase, and W-phase. Electric wires constituting the coils 27b of each phase are connected to these relay terminals 28. By supplying AC power controlled by the inverter 30 to the coils 27b of each phase, magnetic field changes are periodically generated between the rotor 26 and the stator 27. The magnetic field changes act on the permanent magnets 26a, causing the rotor 26 and the shaft 24 to rotate about the rotation axis.

[0066] 3 is a schematic diagram showing the basic structure of motor 20. The number of magnetic poles and structure of rotor 26 or stator 27 are selected according to the specifications of motor 20. For example, while FIG. 3 shows a motor of the type in which coil 27b is formed on each tooth 27a (so-called concentrated winding), a motor of the type in which electric wire is wound around multiple teeth 27a (so-called distributed winding) may also be used. Motor 20 may also be an outer rotor type in which rotor 26 is located outside stator 27.

[0067] <Inverter> 4 shows a basic circuit diagram of the inverter 30. The inverter 30 is provided with an inverter circuit 40 that converts DC power into three-phase (U-phase, V-phase, W-phase) AC power and outputs it in correspondence with the three-phase motor 20. The inverter circuit 40 is publicly known.

[0068] The inverter circuit 40 is provided with a positive wiring 42 having a positive DC terminal 41 at one end and a negative wiring 44 having a negative DC terminal 43 at one end. The positive DC terminal 41 is connected to the positive electrode of the high-voltage battery 5, and the negative DC terminal 43 is connected to the negative electrode of the high-voltage battery 5. Three circuits (half-bridge circuits 45) that energize the coils 27b of each phase are connected in parallel between the positive wiring 42 and the negative wiring 44.

[0069] Each half-bridge circuit 45 has two switching elements 46 connected in series. A freewheel diode 46a is connected in anti-parallel to each switching element 46. An output wiring 47 is connected between these two switching elements 46. Each output wiring 47 is connected to the coil 27b of the corresponding phase of the motor 20 via a relay terminal 28.

[0070] When inverter 30 is operating, each of switching elements 46 is turned on and off at high speed (switching control). This generates a current with a pseudo-AC waveform, which flows to motor 20 via positive wiring 42 and output wiring 47 of one of the phases. Current flows from motor 20 to negative wiring 44 via output wiring 47 of the remaining phase. Switching elements 46, which turn large currents on and off at high speed under high voltage, are required to have high durability both electrically and mechanically.

[0071] As the switching element 46 that can meet such requirements, an IGBT (Insulated Gate Bipolar Transistor) or a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is generally used. IGBT is mainly used.

[0072] In contrast, in the disclosed inverter 30, a SiC MOSFET (Silicon Carbide Metal Oxide Semiconductor Field Effect Transistor) is used for the switching element 46.

[0073] SiC MOSFETs are well known. SiC MOSFETs are made of SiC, which has more stable physical properties than Si, and therefore have lower electrical resistance and better heat resistance than IGBTs and power MOSFETs. As a result, when compared with similar performance, SiC MOSFETs can be made smaller in chip size than IGBTs and power MOSFETs.

[0074] 5 schematically shows an IGBT chip 50 and a SiC MOSFET chip 50. Each of the SiC MOSFET and IGBT chips 50 is thin, and its underside is joined to a heat dissipation plate 51 for cooling with solder 52. Although not shown, a gate and the like are provided around the periphery of the upper surface of each chip 50. The chip 50, together with wiring, is embedded in insulating resin and incorporated into an electronic component.

[0075] Therefore, if the chip size is reduced, the electronic components built into it can also be reduced in size. In particular, in the case of the power module 70 described below, since it includes two switching elements 46 connected in series, it can be reduced in size even more effectively.

[0076] On the other hand, in the case of an IGBT, since the surface area is large, a relatively large area that can be cooled on the top surface (the area indicated by the two-dot chain line α3) is obtained. Therefore, by joining the heat dissipation plate 51 to the top surface as well as the bottom surface, it can be cooled effectively. In contrast, in the case of an SiC MOSFET, which has a small surface area, the area where the gate and the like are provided cannot be made smaller, so the area that can be cooled is very small.

[0077] For this reason, in the case of SiC MOSFETs, it is inefficient to cool their top surfaces. Therefore, it is more effective to actively cool the bottom surfaces of SiC MOSFETs rather than the top surfaces. Therefore, the disclosed inverter 30 is designed to efficiently cool the bottom surfaces of SiC MOSFETs. As a result, the cooling structure for cooling the top surfaces of SiC MOSFETs can be omitted or simplified, allowing for a thinner design compared to IGBTs.

[0078] <Smoothing capacitor> 4, a smoothing capacitor 60 is connected via an overhead wiring 48 to the positive wiring 42 and the negative wiring 44 located between the positive DC terminal 41, the negative DC terminal 43 and the three half-bridge circuits 45. The smoothing capacitor 60 constitutes the inverter circuit 40 and smoothes the voltage applied between the positive wiring 42 and the negative wiring 44.

[0079] To handle high voltages, the smoothing capacitor 60 is required to have a large capacity. Therefore, in the disclosed inverter 30, as will be described later, a plurality of element capacitors 60a are connected in parallel. That is, the smoothing capacitor 60 of the desired capacity is configured by connecting small, low-capacity capacitors (more specifically, film capacitors) in parallel with each other. That is, the smoothing capacitor 60 of the disclosed inverter 30 is not a single capacitor but is configured as a unit (constituting a smoothing capacitor unit).

[0080] The unitized smoothing capacitor 60 allows for a high degree of design freedom, since the number of element capacitors 60a can be selected according to the desired capacitance. Furthermore, in the disclosed inverter 30, the shape of the smoothing capacitor 60 has been devised to achieve a thin design and high efficiency (details will be described later).

[0081] <Busbar> Large currents flow through electrical wiring such as the positive wiring 42, negative wiring 44, and overhead wiring 48 shown in Figure 4. For this reason, metal fittings (bus bars) made of copper plates or the like are generally used to configure these electrical wiring. If the bus bar is long, the electrical resistance increases, copper loss increases, and the amount of heat generated also increases.

[0082] Furthermore, switching control turns large currents on and off at high speed, which causes large magnetic changes in the busbars. As a result, when the inverter operates, noise, vibration, electromagnetic interference, etc. are generated in the busbars. These result in energy loss and have various adverse effects on the performance of the automobile 1.

[0083] The impact becomes more pronounced if the busbar shape becomes complex due to bending, etc. If the shapes of busbars, which require uniformity, such as positive and negative poles, are different, the controllability of the motor also deteriorates.

[0084] To prevent these problems, it is effective to reduce and equalize the inductance of the bus bars. Therefore, in the disclosed inverter 30, the shape and arrangement of the bus bars are devised to reduce and equalize the inductance of the bus bars in order to achieve a thinner, lighter, and more efficient inverter, as well as to reduce the heat and noise generated by the bus bars (details will be described later).

[0085] <Power module> Fig. 6 shows a power module 70 of this embodiment. The power module 70 is a small electronic component with a thin, flat shape. The top and bottom surfaces of the power module 70 are formed in a rectangular shape. One of the short ends is provided with one output terminal 71, and the other short end is provided with two terminals (a positive terminal 72 and a negative terminal 73).

[0086] In this power module 70, the positive electrode terminal 72 and the negative electrode terminal 73 are positioned apart from each other in the vertical direction and also in the width direction to avoid contact. The positive electrode terminal 72 is located on the upper surface side, and the negative electrode terminal 73 is located on the lower surface side. The lower surface of the power module 70 is configured as a flat surface (installation surface 70a).

[0087] As shown in a simplified form in Fig. 6, a half-bridge circuit 45 including two switching elements 46 (SiC MOSFETs) is configured inside the power module 70. The two switching elements 46 connected in series are arranged along the long side of the power module 70. As described above, since the SiC MOSFET chip 50 is used for the switching element 46, the power module 70 is also made smaller and thinner.

[0088] The positive terminal 72 is connected to the positive side of the half-bridge circuit 45, and the negative terminal 73 is connected to the negative side of the half-bridge circuit 45. The output terminal 71 is connected between the two switching elements 46. The inverter 30 uses three power modules 70 to configure the half-bridge circuits 45 of the U phase, V phase, and W phase.

[0089] <Specific configuration and arrangement of power modules, smoothing capacitors, bus bars, etc.> Fig. 7 shows the inside of the first inverter 30 (the inside of the thin case 31) as viewed from the opposite side of the drive motor 20A. Fig. 8 shows a schematic cross-sectional view of the portion indicated by the arrow Y7 in Fig. 7. In the description, the front side of the paper in Fig. 7 is referred to as the upper side.

[0090] The thin case 31 accommodates three power modules 70, a smoothing capacitor 60, a negative bus bar 80 (first bus bar), a positive bus bar 81 (second bus bar), an output bus bar 82, and the like, in a predetermined arrangement. In addition to these, the thin case 31 also accommodates components such as a control board that performs switching control, but these are not shown in the figure. The inside of the thin case 31 is filled with insulating resin, but this is also not shown in the figure.

[0091] (cooling plate) As described above, the thin case 31 is disk-shaped and has a cylindrical shaft tube portion 31a at its center for inserting the rear shaft 22. In this embodiment, a semicircular cooling plate 32 is disposed in approximately half of the thin case 31. As shown in FIG. 8, the cooling plate 32 is a hollow metal member with excellent thermal conductivity. The cooling plate 32 is disposed on the lower side of the thin case 31 (the drive motor 20A side).

[0092] The upper surface of the cooling plate 32 forms a flat support surface 32a that extends perpendicular to the rotation axis direction. The lower surfaces of the smoothing capacitor 60 and the power module 70 form flat installation surfaces 60b and 70a, respectively. The smoothing capacitor 60 and the power module 70 are placed on the support surface 32a via their installation surfaces 60b and 70a.

[0093] That is, smoothing capacitor 60 and power module 70 are arranged inside thin case 31 so as to be aligned on the same plane (on support surface 32a) perpendicular to the direction of the rotation axis.

[0094] 2, thin case 31 is provided with liquid inlet pipes 33 and liquid outlet pipes 34. Cooling plate 32 is configured so that cooling liquid is circulated and supplied through liquid inlet pipes 33 and liquid outlet pipes 34. A plurality of protrusions 32b are provided on the back side of support surface 32a facing the interior of cooling plate 32.

[0095] These protrusions 32b increase the area of ​​the back surface of the support surface 32a, thereby promoting heat exchange with the coolant and improving the cooling performance of the support surface 32a. As a result, the smoothing capacitor 60 and the power module 70 mounted on the support surface 32a can be effectively cooled.

[0096] (smoothing capacitor) The smoothing capacitor 60 is disposed adjacent to the axial cylindrical portion 31a and toward the center of the thin case 31. The three power modules 70 are disposed on the outer periphery of the thin case 31 and are arranged at intervals in the circumferential direction (the direction around the rotation axis J), and are also arranged along the periphery of the smoothing capacitor 60.

[0097] In this embodiment, each of the power modules 70 is arranged so that each terminal faces in the circumferential direction. Specifically, each of the power modules 70 has a positive terminal 72 and a negative terminal 73 located at one end (circumferential end 75) that is perpendicular to the end (inner end 74) that faces the smoothing capacitor 60. These terminals 72, 73 face in the clockwise direction in FIG. 7. The output terminal 71 is located at the other end of the circumferential end 75 and faces in the counterclockwise direction in FIG. 7.

[0098] In this embodiment, the side surface (AC side side surface 61) of the smoothing capacitor 60 facing the three power modules 70 is formed in a polygonal shape made up of three opposing surfaces facing directly toward each power module 70. As shown in Fig. 7 and Fig. 8, a pair of AC side terminals 62 extending along the edge of the AC side side surface 61 are provided at positions spaced apart above and below the AC side side surface 61 (the lower side is the negative side, and the upper side is the positive side).

[0099] Each of the power modules 70 and the smoothing capacitor 60 are arranged so that the size of the gap between each of the power modules 70 and the smoothing capacitor 60 is substantially the same.

[0100] These electronic components 60, 70 are connected by a plate-shaped negative bus bar 80 and a plate-shaped positive bus bar 81. Therefore, current flows through these bus bars 80, 81. The gap between these electronic components 60, 70 corresponds to the wiring length. By making the wiring lengths substantially the same, it is possible to equalize the inductance between each power module 70 and the smoothing capacitor 60, as will be described later. By equalizing the inductance, it is possible to suppress deterioration in the controllability of the motor 20.

[0101] As described above, the smoothing capacitor 60 is configured by connecting multiple element capacitors 60a in parallel. Therefore, the external shape of the smoothing capacitor 60 can be freely set by changing the arrangement of these element capacitors 60a. By selecting element capacitors 60a with low height and arranging them side by side, the smoothing capacitor 60 can be made flat. In this way, even if the capacity is increased, it is only necessary to expand the size of the smoothing capacitor 60 in the horizontal direction, and the inverter 30 can be kept thin.

[0102] The element capacitors 60a arranged opposite the three power modules 70 are preferably arranged along the AC side surface portion 61 so as to follow the arrangement of these power modules 70. This makes it possible to shorten the distance between these element capacitors 60a and each of the power modules 70, thereby facilitating the reduction and equalization of inductance.

[0103] Meanwhile, a pair of DC side terminals 64, 64 are provided on a side surface (DC side side surface 63) of the smoothing capacitor 60 opposite to the AC side side surface 61. Each of these DC side terminals 64 constitutes a positive side DC terminal 41 and a negative side DC terminal 43 of the inverter circuit 40, and is connected to a corresponding electrode of the high-voltage battery 5.

[0104] (negative bus bar and positive bus bar) The negative bus bar 80 and the positive bus bar 81 connect the smoothing capacitor 60 and the three power modules 70 that make up the half-bridge circuit 45. In other words, these bus bars 80, 81 make up parts in the inverter circuit 40 that correspond to the overhead wiring 48, the positive wiring 42, and the negative wiring 44 that are located between the smoothing capacitor 60 and the half-bridge circuit 45.

[0105] Therefore, large currents flow through these busbars 80, 81, and these large currents fluctuate due to switching control. This generates large amounts of heat and large magnetic changes in these busbars 80, 81. If the negative busbar 80 and the positive busbar 81 have complex shapes, this effect becomes more pronounced. These magnetic changes in the busbars 80, 81 also cause noise, vibration, electromagnetic interference, and other problems. These problems result in energy loss and have various adverse effects on the performance of the automobile 1.

[0106] In contrast, in the disclosed inverter 30, these bus bars 80, 81 are formed as wide plates that extend in the circumferential direction (bus plates are preferable in terms of shape, but the general term bus bars is used here). One outer edge of each bus bar is connected to the positive terminal 72 or negative terminal 73 of each power module 70, and the other inner edge is connected to the corresponding terminal of the smoothing capacitor 60.

[0107] Specifically, the negative bus bar 80 has its outer edge 80b connected to each negative terminal 73 of the power module 70, and its inner edge 80a connected to the negative AC terminal 62 of the smoothing capacitor 60. The positive bus bar 81 has its outer edge 81b connected to each positive terminal 72 of the power module 70, and its inner edge 81a connected to the positive AC terminal 62 of the smoothing capacitor 60.

[0108] The negative bus bar 80 is located below the positive bus bar 81, and is formed and arranged to fit into the gap between each power module 70 and the smoothing capacitor 60, as indicated by dots in Fig. 7. Specifically, the inner edge 80a of the negative bus bar 80 is formed in a polygonal shape corresponding to the polygonal shape of the AC side surface portion 61. The outer edge 80b of the negative bus bar 80 is formed in a polygonal shape similar to that of the inner edge 80a.

[0109] Then, by cutting out the portions that overlap with each of the power modules 70, three recesses 83 are formed on the side of the outer edge portion 80b of the negative electrode side bus bar 80, and each of the power modules 70 is fitted into these recesses 83. As a result, the negative electrode side bus bar 80 extends in the circumferential direction along each of the power modules 70 and the smoothing capacitor 60 while being fitted into the gap between each of the power modules 70 and the smoothing capacitor 60.

[0110] As shown in FIG. 8, the negative bus bar 80 is placed on the support surface 32a of the cooling plate 32 and is joined to the negative AC terminal 62 of the smoothing capacitor 60 and the negative terminal 73 of each power module 70.

[0111] The positive busbar 81 is disposed above the negative busbar 80, and as shown in Fig. 7, is formed in a plate shape extending along the surface of each power module 70. Specifically, like the negative busbar 80, the inner edge portion 81a of the positive busbar 81 is formed in a polygonal shape corresponding to the polygonal shape of the AC side surface portion 61. The outer edge portion 81b of the positive busbar 81 is formed in a polygonal shape similar to the inner edge portion 81a.

[0112] As a result, the positive bus bar 81 extends in the circumferential direction along each of the power modules 70 and the smoothing capacitor 60 while spreading along the surface of each of the power modules 70 .

[0113] As shown in FIG. 8, the positive bus bar 81 is joined to the positive AC terminal 62 of the smoothing capacitor 60 and to each positive terminal 72 of the power module 70, with the positive bus bar 81 facing the negative bus bar 80 at a distance from the negative bus bar 80.

[0114] The negative bus bar 80 and the positive bus bar 81 are both thin, flat plates designed to have short wiring lengths and large widths (lengths in a direction perpendicular to the wiring lengths). In this embodiment, the positive bus bar 81 has a longer wiring length than the negative bus bar 80 due to the shape and arrangement of the power module 70.

[0115] (Relationship between busbar shape and inductance) It is common knowledge that the wider the busbar, the smaller the inductance, and the longer the wiring length of the busbar, the greater the inductance. However, when the inventors investigated the relationship between the shape of the busbar and its inductance, they found that the same inductance can sometimes be obtained even when the wiring length is different.

[0116] An example of a busbar is shown in Fig. 9. This busbar is modeled after negative busbar 80 and positive busbar 81, and has a width W greater than its length L. The symbol t denotes thickness. Fig. 10 is a graph summarizing the relationship between inductance (more specifically, inductance sensitivity) and the busbar shape.

[0117] The top graph shows the relationship between the busbar width W and inductance, the middle graph shows the relationship between the busbar length L and inductance, and the bottom graph shows the relationship between the busbar thickness t and inductance.

[0118] In the busbar shown in Figure 9, as the width W increases, the inductance decreases. Similarly, it was thought that as the length L increases, the inductance increases, but it was confirmed that an inflection point exists in the short length L region.

[0119] As a result, the same inductance H1 can be obtained for both bus bars of length L1 and bus bars of length L2, as shown in Fig. 10. In other words, as long as the length L is within a certain range, bus bars of different lengths L can be designed to have the same inductance.

[0120] It was also confirmed that the thickness t of the bus bar has almost no effect on the inductance, meaning that the thickness t of the bus bar can be set to the minimum required size in practice.

[0121] Based on this knowledge, the inventors of the present invention have realized that in order to reduce and equalize the inductance of a bus bar, it is sufficient to make the length L short, the width W large, and the thickness t as small as possible, and that the inductance can be made the same even if the lengths are different.The shapes and arrangements of negative bus bar 80 and positive bus bar 81 have been devised based on this knowledge.

[0122] Specifically, in this embodiment, the negative bus bar 80 and the positive bus bar 81 have different lengths. Therefore, the lengths and widths of the negative bus bar 80 and the positive bus bar 81 are adjusted so that the inductances of these bus bars are approximately the same. That is, like the bus bar with length L1 and the bus bar with length L2 described above, the length L(-) of the negative bus bar 80 and the length L(+) of the positive bus bar 81 are adjusted, along with their widths, so that the inductances are the same. This equalizes the inductances of these bus bars. As a result, deterioration in the controllability of the motor 20 can be suppressed.

[0123] Moreover, the negative bus bar 80 and the positive bus bar 81 are shared by each power module and are relatively short in length and large in width. This reduces their own inductance. Furthermore, these bus bars 80, 81 have a large surface area, which provides excellent heat dissipation. The negative bus bar 80, which has a relatively small surface area, is in face-to-face contact with the cooling plate 32, allowing for effective cooling.

[0124] On the other hand, the positive bus bar 81, which is not in contact with the cooling plate 32, has a relatively large surface area. Therefore, it has excellent heat dissipation properties. Moreover, because the positive bus bar 81 is in contact with the upper surface of each of the power modules 70, it can also promote heat dissipation from each of the power modules 70.

[0125] These bus bars 80, 81 are flat and have a simple shape. They are easy to process and can suppress magnetic changes. They are advantageous for achieving a slim design and can be housed in a thin case 31 with a small thickness. Since the positive and negative terminals of the three power modules 70 are connected by a single bus bar, they are also advantageous in terms of the number of parts and processing man-hours.

[0126] (Output bus bar) The output bus bar 82 constitutes a portion corresponding to the output wiring 47 of the inverter circuit 40. That is, the output bus bar 82 is connected to each output terminal 71 of the power module 70 and the relay terminal 28 of the corresponding phase of the drive motor 20A.

[0127] In this embodiment, the output terminals 71 of two of the three power modules 70 are located below the positive bus bar 81. Therefore, openings 84 are formed in the upper surface of the positive bus bar 81 at portions that overlap with the output terminals 71 of these two power modules 70.

[0128] One end of each output bus bar 82 is joined to the output terminal 71, with one end of the output bus bar 82 remaining as is, and with the other two output bus bars 82 being joined through these openings 84. The relay terminals 28 for each phase are arranged in accordance with the arrangement of each power module 70. In other words, the arrangement of the relay terminals 28 for each phase is designed so that the wiring lengths of the output bus bars 82 are the same.

[0129] Therefore, the three output bus bars 82 are the same metal fittings and have the same length, shape, etc. As a result, the inductance of each of these output bus bars 82 is also the same, and the inductance of the output bus bars 82 is also leveled out.

[0130] As described above, the first electric drive unit 10A of this embodiment is smaller and lighter than conventional electric drive units that use inverters, and its performance is improved. Therefore, when installed in an automobile 1, it can improve fuel economy and electricity efficiency and increase the design freedom of the automobile 1. It can also suppress noise and other issues, resulting in a high-performance automobile 1. Note that although the first electric drive unit 10A has been described in this embodiment, the same can be applied to the second electric drive unit 10B.

[0131] <Second embodiment> A second embodiment of the disclosed electric drive unit is shown in Figures 11 and 12. Figure 12 is a schematic cross-sectional view of the portion indicated by arrow Y11 in Figure 11.

[0132] The basic configuration of the motor 20, inverter 30, etc. of this embodiment is the same as that of the above-described embodiment. Therefore, the same components as those of the above-described embodiment will be designated by the same reference numerals and will not be described again. Then, the components that differ from those of the above-described embodiment will be specifically described (the same applies to other embodiments).

[0133] In this embodiment, the orientation of each power module 70 is different. That is, each power module 70 of this embodiment is arranged in a state where each power module 70 of the above-described embodiment is rotated by 90 degrees.

[0134] As a result, each of the power modules 70 of this embodiment is arranged so that each terminal faces in the radial direction (the radial direction centered on the rotation axis J). Specifically, each of the power modules 70 is arranged radially, and has both a positive terminal 72 and a negative terminal 73 at an inner end 74 located toward the center of the thin case 31. Each of the power modules 70 has an output terminal 71 at an end (outer end 76) located on the outer periphery of the thin case 31 that does not face the smoothing capacitor 60.

[0135] 12, each positive electrode terminal 72 and negative electrode terminal 73 of the power module 70 faces a corresponding pair of AC side terminals 62, 62 of the smoothing capacitor 60. Therefore, the positive electrode side bus bar 81 and the negative electrode side bus bar 80 can be made to have the same shape.

[0136] Specifically, the same metal fittings are used for the positive bus bar 81 and the negative bus bar 80 in this embodiment. Therefore, the length, width, and thickness of these bus bars 80, 81 are the same. The gaps between each of the power modules 70 and the smoothing capacitor 60 are substantially the same, and these bus bars 80, 81 (corresponding to the first bus bar) fit into these gaps.

[0137] In this embodiment, the positive bus bar 81 and the negative bus bar 80 are each formed in a strip-like plate shape that is wide but short in length. They are formed in a curved shape so as to extend along each of the power modules 70 and the smoothing capacitors 60. The length L(+) of the positive bus bar 81 and the length L(-) of the negative bus bar 80 are the same. Therefore, the inductances of the positive bus bar 81 and the negative bus bar 80 are the same.

[0138] Each output terminal 71 of the power module 70 is located radially outward. Therefore, the output bus bars 82 connected to these output terminals 71 extend radially and are connected to the corresponding relay terminals 28 over the shortest distance. The lengths of the output bus bars 82 are also designed to be the same. Therefore, the inductance of each output bus bar 82 is also the same.

[0139] Even if the shapes and arrangements of the power module 70 and bus bars 80, 81, 82 are configured as in this embodiment, the same effects as those of the above-described embodiment can be obtained. Therefore, by adopting the electric drive unit of this embodiment, it is possible to reduce the size and weight of the electric drive unit compared to electric drive units using conventional inverters, and performance can also be improved. When installed in an automobile, it is possible to improve fuel efficiency and power consumption, and it also increases the degree of freedom in automobile design. Noise and other issues can also be suppressed, allowing for a high-performance automobile to be realized.

[0140] <Third embodiment> A third embodiment of the disclosed electric drive unit is shown in Figures 13, 14, and 15. Figure 14 is a schematic cross-sectional view of the portion indicated by arrow Y13 in Figure 13. Figure 15 is an explanatory diagram of the main parts of the inverter 30 and the structure of the power module 70.

[0141] In this embodiment, the AC side side surface portion 61 of the smoothing capacitor 60 is formed in an arc shape. A pair of AC side terminals 62, 62 provided on the AC side side surface portion 61 are also formed so as to extend in an arc shape along the edge thereof.

[0142] In this embodiment, the arrangement of the positive terminal 72, negative terminal 73, and output terminal 71 of each power module 70 differs from that of the above-described embodiment. Specifically, as shown in Fig. 15, the positive terminal 72 and the negative terminal 73 are arranged in opposite directions to each other in accordance with the arrangement direction of the half-bridge circuit 45. The output terminal 71 is also arranged on the top surface of the power module 70 (specifically, in the middle part in the longitudinal direction) in accordance with the arrangement direction of the half-bridge circuit 45.

[0143] 13, each power module 70 is arranged so that the negative terminal 73 (corresponding to the inner terminal) is located at the inner end 74 and the positive terminal 72 (corresponding to the outer terminal) is located at the outer end 76. The negative terminal 73 faces the negative AC terminal 62, and the gaps between each power module 70 and the smoothing capacitor 60 are substantially the same.

[0144] The negative bus bar 80 in this embodiment is formed in the shape of a curved strip, and thus fits into the gap (corresponding to the first bus bar) in the same way as the bus bars 80 and 81 in the second embodiment.

[0145] On the other hand, the positive bus bar 81 in this embodiment is formed in a plate shape (corresponding to a third bus bar) that is bent and extends along the surface of each power module 70. Specifically, the positive bus bar 81 in this embodiment has a main wall portion 90 and an outer peripheral wall portion 91, as shown in Figs.

[0146] The main wall portion 90 is formed so as to expand in a fan shape in the circumferential direction along the upper surface of each power module 70. A through hole 92 is formed in the main wall portion 90 at a position corresponding to the output terminal 71 of each power module 70. The outer peripheral wall portion 91 is connected to the arc-shaped outer peripheral edge of the main wall portion 90, bends in a direction perpendicular to the arc-shaped outer peripheral edge, and extends along the outer end portion 76 of each power module 70.

[0147] The inner edge 81a of the positive bus bar 81 of this embodiment is formed in a circular arc shape extending in the circumferential direction, similar to the inner edge 80a of the negative bus bar 80. Therefore, the inner edge 81a of the positive bus bar 81 of this embodiment is joined to the positive AC terminal 62 in a state where it is fitted into the AC side surface portion 61 of the smoothing capacitor 60. The outer edge 81b (the end portion of the outer peripheral wall portion 91) of the positive bus bar 81 of this embodiment is joined to the positive terminal 72 in a state where it is fitted into each outer end portion 76 of the power module 70.

[0148] In this embodiment, the negative bus bar 80 and the positive bus bar 81 have different lengths. Therefore, the lengths and widths of the negative bus bar 80 and the positive bus bar 81 are adjusted so that their inductances are approximately the same. That is, the length L(-) of the negative bus bar 80 and the length (the sum of La(+) and Lb(+)) of the positive bus bar 81 are adjusted along with their widths. This equalizes the inductances of the bus bars 80 and 81. As a result, deterioration in the controllability of the motor 20 can be suppressed.

[0149] Each output-side bus bar 82 is joined to the output terminal 71 of each power module 70 and is drawn out above the positive-side bus bar 81 through a through-hole 92. The output-side bus bar 82 and the positive-side bus bar 81 are insulated from each other by a resin sheet 93. Each output-side bus bar 82 is formed in a bent shape with an L-shaped cross section so as to extend along the upper surface of each power module 70.

[0150] Each output bus bar 82 extends radially outward and then turns in the direction of the rotation axis toward the motor 20, where it is connected to a corresponding relay terminal 28. The lengths of each output bus bar 82 are also designed so that the wiring lengths are the same. Therefore, the inductances of each output bus bar 82 are also the same.

[0151] Even if the shapes and arrangements of the power module 70 and the bus bars 80, 81, 82 are configured as in this embodiment, the same effects as those of the above-described embodiment can be obtained.

[0152] <Fourth embodiment> FIG. 16 shows a fourth embodiment of the disclosed electric drive unit. The basic configuration of this embodiment is the same as that of the third embodiment. In the third embodiment, the half-bridge circuit 45 for each phase is configured with a power module 70 including two switching elements 46. However, as shown in a simplified form in FIG. 16, in this embodiment, each power module 70 is configured with one switching element 46.

[0153] These two power modules 70 are connected in series using a relay bus bar 95, thereby forming a half-bridge circuit 45. The output bus bar 82 is joined to the relay bus bar 95. As in the third embodiment, in this embodiment, the lengths and widths of the negative bus bar 80 and the positive bus bar 81 are adjusted so that their inductances are approximately the same. The lengths of the output bus bars 82 are also designed so that their inductances are the same.

[0154] Even if the shapes and arrangements of the power module 70 and the bus bars 80, 81, 82, and 95 are configured as in this embodiment, the same effects as those of the above-described embodiment can be obtained.

[0155] <Fifth embodiment> A fifth embodiment of the disclosed electric drive unit is shown in Figure 17. This embodiment shows a configuration corresponding to a second electric drive unit 10B.

[0156] That is, in the case of the second electric drive unit 10B, the second inverter 30 is integrated with the in-wheel motor 20B, so it is not necessary to insert the shaft 24 through the center of the thin case 31. Therefore, the thin case 31 of this embodiment does not have a shaft cylinder portion 31a in the center, as in the above-mentioned embodiments. This increases the space in the center of the thin case 31.

[0157] Therefore, by utilizing this space, the smoothing capacitor 60 of this embodiment is formed in a disk shape coaxial with the thin case 31. This allows the capacitance of the smoothing capacitor 60 to be increased. For the same capacitance, the thickness can be reduced. Furthermore, because the length from the center of the thin case 31 to the AC-side side surface portion 61 is the same, each power module 70 can be arranged point-symmetrically, facilitating layout design of the electronic components.

[0158] The shapes and arrangement of each power module 70, positive bus bar 81, negative bus bar 80, and output bus bar 82 shown in this embodiment are the same as those of the third embodiment shown in Fig. 13. Alternatively, the shapes and arrangement may be the same as those of the other embodiments.

[0159] Even if the shapes and arrangements of the power module 70 and the bus bars 80, 81, 82 are configured as in this embodiment, the same effects as those of the above-described embodiment can be obtained.

[0160] <Other forms> The disclosed technology is not limited to the above-described embodiments, and includes various other configurations.

[0161] For example, in each of the above-described embodiments, the inverter 30 in which the power modules 70 and the bus bars 80, 81, 82 are arranged on a part of the outer periphery of the thin case 31 in the circumferential direction has been exemplified.

[0162] 17, as shown by the imaginary line α4, each power module 70 may be arranged over any portion of the entire circumference of the thin case 31, and accordingly, the smoothing capacitor 60 may be extended in the circumferential direction, and the bus bars 80, 81, 82 may be formed in an annular shape or the like over the entire circumference. In this way, a larger number of power modules 70 can be installed, thereby realizing an inverter compatible with a polyphase motor or a high-output inverter.

[0163] The inverter 30, which has been made thinner and lighter using the disclosed technology, is preferably disposed adjacent to one end of the motor 20 in the direction of the rotation axis, but this location is not essential. Depending on the specifications of the automobile, the inverter 30 may be disposed in the vicinity of the motor 20, such as to the side or above the motor 20. [Explanation of symbols]

[0164] 1. Automobiles 2 engines 4. Automatic transmission 5 High Voltage Battery 10A First Electric Drive Unit 10B Second electric drive unit 20 Motor 20A drive motor (motor) 20B In-wheel motor (motor) 28 Relay terminal 30 inverters 31 Slim Case 40 Inverter circuit 45 Half-bridge circuit 46 Switching element 60 Smoothing capacitor 60a element capacitor 70 Power Module 80 Negative bus bar (first bus bar) 81 Positive bus bar (second bus bar, third bus bar) 82 Output bus bar

Claims

1. An electric drive unit in which an inverter is disposed adjacent to one end of a motor in a rotational shaft direction, The inverter is a plurality of power modules each including at least one switching element and constituting an inverter circuit for converting DC power into AC power; a smoothing capacitor that configures the inverter circuit together with the plurality of power modules; a bus bar made of a plate-shaped metal fitting that connects each of the power modules and the smoothing capacitor; a thin case that houses the power module, the smoothing capacitor, and the bus bar and is smaller in the direction of the rotation axis than in the radial direction; Equipped with a plurality of the power modules are arranged around the smoothing capacitor in a circumferential direction, and the bus bar is formed to extend in the circumferential direction, an inner edge portion of the bus bar connected to the terminal of the smoothing capacitor is formed in an arc or circle shape extending in the circumferential direction, and a side portion of the smoothing capacitor on which the terminal is provided and facing the power module is formed in an arc or circle shape, and the inner edge portion of the bus bar is connected to the side portion of the smoothing capacitor.

2. 2. The electric drive unit according to claim 1, The thin case has a disk-like outer shape corresponding to the motor.

3. 2. The electric drive unit according to claim 1, An electric drive unit in which the smoothing capacitor and the power module are each formed in a flat shape having an installation surface on one side, and are placed on a common support surface via the installation surface.

4. 4. The electric drive unit according to claim 3, the bus bars are formed to expand in the circumferential direction and have arc-shaped or circular inner edge portions extending in the circumferential direction, and include a plate-shaped third bus bar that expands in a fan shape along the top surface of each of the power modules, an electric drive unit, wherein the third bus bar is connected to one of the positive and negative terminals of each of the power modules and a corresponding terminal of the smoothing capacitor;

5. 5. The electric drive unit according to claim 4, the busbar is formed to expand in the circumferential direction and has an arc-shaped or circular inner edge portion extending in the circumferential direction, and the busbar is formed in a plate shape extending in a strip shape between and along each of the power modules and the smoothing capacitor, and the electric drive unit further includes a first busbar connected to the other of the positive and negative terminals of each of the power modules and the corresponding terminal of the smoothing capacitor.

6. An electric drive unit according to any one of claims 1 to 5, an electric drive unit, wherein each of the power modules has positive and negative terminals, includes a half-bridge circuit connected between the positive and negative terminals with two of the switching elements connected in series, and further includes an output terminal connected between the two switching elements.

7. An electric drive unit according to any one of claims 1 to 6, An electric drive unit, wherein the switching element is composed of a SiC MOSFET.

8. An electric drive unit according to any one of claims 1 to 7, the smoothing capacitor is configured by connecting a plurality of element capacitors in parallel, An electric drive unit, wherein a plurality of the element capacitors are arranged opposite the plurality of power modules and are arranged along the alignment of the plurality of power modules.

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