Drive unit for a vehicle

Abstract

The present application relates to a drive unit of a vehicle in which a motor and an inverter having a smoothing capacitor and a plurality of power modules are arranged adjacent to each other in a motor axial direction. The smoothing capacitor and each power module are connected by a bus bar. Each power module has a flat shape with a wide width, and has a first cooled surface facing a motor side on one surface side. The first cooled surface of each power module is arranged on a placement surface orthogonal to the axial direction. The bus bar has a plate shape, and has a second cooled surface facing the motor side on one surface side. One end of the bus bar is connected to the smoothing capacitor and the other end is connected to each power module, and the bus bar is formed with a wide width so as to extend along the arrangement direction of each power module. The second cooled surface is placed on the placement surface. A cooling portion facing the first cooled surface and the second cooled surface is provided at a position closer to the motor side than the placement surface. The power modules can be cooled, and the unit including the motor and the inverter can be reduced.

Description

Technical Field

[0001] This disclosure relates to a drive unit for a vehicle, including an electric motor and an inverter. Background Technology

[0002] In recent years, the popularity of electric vehicles, such as hybrid vehicles and electric cars, has increased significantly. These vehicles are equipped with a drive motor and a battery. The drive unit, consisting of the motor and battery, uses an inverter to convert the direct current from the battery into alternating current to drive the motor.

[0003] Inverters consist of smoothing capacitors and power modules including switching elements. Inverters handle large amounts of electricity, thus requiring high voltage and flowing current. Consequently, they generate significant heat during operation, necessitating cooling. Large surge voltages can also occur. Consequently, the various electronic components that make up the inverter are larger, contributing to its weight. Therefore, existing inverters are a major obstacle to improvements in fuel consumption and power efficiency.

[0004] To shorten power transmission distances, inverters are typically placed near the electric motor. However, in the case of automobiles, the sheer number of devices and limited space make it difficult to accommodate inverters. Vehicle balance must also be considered. Therefore, it is challenging to properly install large and heavy inverters within a car.

[0005] Among the components of an inverter, the power module generates particularly much heat, thus requiring cooling. Patent Document 1 discloses an inverter that includes a cooling structure for the power module. In this cooling structure, most of the power module, except for its lower end, i.e., its upper surface and sides, is inserted into a coolant passage and immersed in the coolant.

[0006] Patent Document 1: Japanese Patent Publication No. 2021-112011 Summary of the Invention

[0007] -The technical problem the invention aims to solve-

[0008] The power module described in Patent Document 1 has a relatively long longitudinal length, resulting in a smaller area on its upper and lower surfaces compared to its sides. Therefore, not only must the upper or lower surface of the power module be inserted into the cooling path, but the sides must also be inserted into the cooling path. Consequently, the inverter's cooling structure becomes larger, and the overall drive unit, consisting of the motor and inverter, also becomes larger.

[0009] This disclosure was made to solve the aforementioned technical problems, and its purpose is to: adequately cool the power module and miniaturize the drive unit consisting of the motor and the inverter.

[0010] - Technical solutions for solving technical problems -

[0011] The vehicle drive unit, electric motor, and inverter having a smoothing capacitor and multiple power modules disclosed herein are arranged adjacent to each other along the axial direction of the electric motor. The smoothing capacitor and each of the power modules are interconnected via a busbar. Each power module has a wide, flat shape and a first cooling surface facing the electric motor on one side. The first cooling surfaces of each power module are arranged on a placement surface orthogonal to the axial direction. The busbar is plate-shaped and has a second cooling surface facing the electric motor on one side. One end of the busbar is connected to the smoothing capacitor, and the other end is connected to each of the power modules. The busbar is wide and extends along the arrangement direction of each power module. The second cooling surface is placed on the placement surface, and a cooling section facing the first and second cooling surfaces is provided at a position closer to the electric motor than the placement surface.

[0012] According to this structure, since the large first surface to be cooled in the wide, flat power module faces the cooling section, the cooling area of ​​the cooling section for cooling the power module can be increased. In this way, even when the cooling section only cools one side of the power module (the first surface to be cooled), sufficient cooling capacity can be ensured.

[0013] By extending the busbars along the arrangement direction of the power modules, the width of the busbars can be increased. Since the larger second cooling surface of the wide, plate-like busbar faces the cooling section, the heat dissipation area from the busbars to the cooling section can be increased. This compensates for insufficient cooling capacity of the cooling section even when the cooling capacity of the power modules is inadequate.

[0014] Since the first cooling surfaces of each power module are arranged on a mounting surface orthogonal to the motor axis, the axial length of the inverter can be shortened. Because the cooling section only needs to be located on one side of the power module, the inverter can be miniaturized compared to having the cooling section on both sides of the power module.

[0015] This allows for adequate cooling of the power module and enables the miniaturization of the drive unit, which consists of a motor and an inverter.

[0016] In one embodiment, the cooling section includes a cooling passage for the flow of a cooling medium.

[0017] According to this structure, by allowing the cooling medium to flow in the cooling path, the cooling capacity of the cooling unit for the power module can be further increased.

[0018] In one embodiment, the power module includes a SiC-MOSFET.

[0019] According to this structure, because the SiC-MOSFET chip included in the power module is small, the size of the heat transfer block (e.g., copper block) disposed on the SiC-MOSFET chip is also small. Therefore, if the power module is to be effectively cooled on both sides, an expensive ceramic substrate (e.g., SiN) needs to be placed on both sides of the SiC-MOSFET chip. Therefore, compared to cooling the power module on both sides, cooling only one side and improving the cooling of that side is more cost-effective.

[0020] In one embodiment, the smoothing capacitor has a third cooled surface on one side facing the motor side, the third cooled surface is placed on the placement surface, and the cooling portion also faces the third cooled surface.

[0021] According to this structure, the smoothing capacitor can also be cooled by the cooling unit together with the power module.

[0022] In one embodiment, each of the power modules is arranged closer to the outer periphery than the smooth capacitor, and the busbar is formed in a wide manner extending circumferentially along the motor.

[0023] Based on this structure, the width of the busbar can be easily increased.

[0024] In one embodiment, the inductance of the busbar is a function of the length from one end of the busbar to the other end, the function having a minimum value such that the inductance is equal under unequal first and second lengths. The smoothing capacitor and each of the power modules are interconnected via a negative-side busbar and a positive-side busbar, one of the negative-side busbar and the positive-side busbar having a length of the first length, the other of the negative-side busbar and the positive-side busbar having a length of the second length, and at least one of the negative-side busbar and the positive-side busbar having a second cooled surface.

[0025] According to this structure, even though the lengths of the negative side busbar and the positive side busbar are not equal, the inductance of the negative side busbar and the inductance of the positive side busbar can be balanced.

[0026] -The effects of the invention-

[0027] According to this disclosure, the power module can be adequately cooled, and the drive unit consisting of a motor and an inverter can be miniaturized. Attached Figure Description

[0028] Figure 1 This is a simplified structural diagram of a vehicle system including the drive unit involved in the first embodiment;

[0029] Figure 2 It is a three-dimensional view of the drive unit, including the motor and inverter;

[0030] Figure 3 This is a cross-sectional view of the motor viewed from the inverter side;

[0031] Figure 4 This is the circuit diagram of the inverter;

[0032] Figure 5 This section compares SiC-MOSFETs with IGBTs.

[0033] Figure 6 The detailed structure of the power module is shown in 3D diagrams and circuit diagrams;

[0034] Figure 7 This is a cross-sectional view of the inverter viewed from the side opposite to the motor.

[0035] Figure 8 This is a longitudinal sectional view of the inverter;

[0036] Figure 9 It is a 3D diagram of the busbar;

[0037] Figure 10 It is a graph showing the relationship between the busbar size and the inductor sensitivity;

[0038] Figure 11 This is a cross-sectional view of the inverter's cooling path from the motor side;

[0039] Figure 12 The first variation of the first embodiment involves the equivalent of Figure 11 The diagram is a cross-sectional view of the inverter's cooling path from the motor side;

[0040] Figure 13 The second variation of the first embodiment relates to... Figure 7 The diagram is a cross-sectional view of the inverter viewed from the opposite side of the motor;

[0041] Figure 14 The second embodiment is equivalent to Figure 7 The diagram is a cross-sectional view of the inverter viewed from the opposite side of the motor;

[0042] Figure 15 The second embodiment is equivalent to Figure 8 The diagram is a longitudinal sectional view of the inverter;

[0043] Figure 16 The third embodiment involves the equivalent of Figure 7 The diagram is a cross-sectional view of the inverter viewed from the opposite side of the motor;

[0044] Figure 17 The third embodiment is equivalent to Figure 8 The diagram is a longitudinal sectional view of the inverter;

[0045] Figure 18 The first variation of the third embodiment involves the equivalent of Figure 8 The diagram is a longitudinal sectional view of the inverter;

[0046] Figure 19 This is a perspective view of the power module and busbar involved in the second variation of the third embodiment.

[0047] - Symbol Explanation -

[0048] A – Drive unit; H – Cooling medium; L1 – First length; L2 – Second length; K – Inductor sensitivity; M – Minimum value; 1 – Vehicle; 3 – Drive motor; 12 – Battery; 14 – In-wheel motor; 15 – Inverter; 16 – Inverter; 19 – Smoothing capacitor; 19a – Lower surface (third cooled surface); 20 – Power module; 24 – Chip (SiC-MOSFET); 25 – Copper block; 31 – Lower surface (first cooled surface); 51 – Negative side busbar; 51a – Lower surface (second cooled surface); 51i – One end; 51o – The other end; 52 – Positive side busbar; 52i – One end; 52o – The other end; 60 – Heat dissipation device; 61 – Cooling passage (cooling section); 64 – Fin (cooling section); 65 – Placement surface. Detailed Implementation

[0049] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings. The preferred embodiments described below are merely examples and are not intended to limit the scope of this disclosure, its application, or its uses.

[0050] <First Implementation>

[0051] (Vehicle Composition)

[0052] Figure 1 The vehicle 1, including the drive unit A according to the first embodiment, is shown in a view from below. The vehicle 1 transmits power from at least one of the engine 2 and the drive electric motor 3 arranged at the front of the vehicle to the rear wheels 4 arranged at the rear of the vehicle. That is, the vehicle 1 is a front-engine, rear-wheel-drive (FR) hybrid vehicle.

[0053] like Figure 1 As shown, vehicle 1 includes: engine 2; transmission 5 connected to engine 2; drive motor 3 disposed between engine 2 and transmission 5; drive shaft 6 connected to transmission 5 and transmitting power from engine 2 and drive motor 3 to rear wheels; and differential 7 connected to drive shaft 6 and transmitting power from engine 2 and drive motor 3 to left and right rear wheels 4.

[0054] The drive shaft 6 extends along the vehicle's longitudinal direction beneath the floor panel 8. A passageway 9 is provided at the center of the floor panel 8 in the vehicle width direction. The drive shaft 6 is located inside the passageway 9.

[0055] Vehicle 1 includes an exhaust pipe 10 extending from engine 2 in the longitudinal direction of the vehicle. A catalyst device 11 is provided on the upstream side of the exhaust pipe 10. Although not shown, a muffler is provided on the downstream side of the exhaust pipe 10.

[0056] Vehicle 1 includes: a fuel tank (not shown) storing fuel supplied to engine 2; and a battery 12 storing electricity supplied to electric motor 3. The drive electric motor 3 transmits power to the rear wheels 4 and, when the vehicle decelerates, is driven by a drive shaft 6 to rotate, thereby generating electricity and supplying it to battery 12. Battery 12 consists of a first battery unit 12a and a second battery unit 12b arranged on both sides in the vehicle width direction. In the vehicle's longitudinal direction, the second battery unit 12b is longer than the first battery unit 12a. Each battery unit 12a, 12b consists of multiple battery cells. The battery cells are, for example, lithium-ion batteries.

[0057] Each of the left and right front wheels 13 is connected to an in-wheel motor 14. The in-wheel motor 14 functions as an auxiliary motor, generating power when the vehicle 1 starts and transmitting that power to the front wheels 13. The in-wheel motor 14 also functions as a regenerative brake, generating electricity when the vehicle decelerates. Similar to the drive motor 3, the in-wheel motor 14 receives power from the battery 12.

[0058] like Figure 1 As shown, an inverter 15 is sandwiched between the drive motor 3 and the transmission 5. The drive motor 3 and the inverter 15 are arranged adjacent to each other in the axial direction (vehicle longitudinal direction) of the drive motor 3. An inverter 16 is arranged inside the in-wheel motor 14 in the vehicle width direction. The in-wheel motor 14 and the inverter 16 are arranged adjacent to each other in the axial direction (vehicle width direction) of the in-wheel motor 14. The drive motor 3 and the inverter 15 constitute drive unit A. Similarly, the in-wheel motor 14 and the inverter 16 constitute drive unit A.

[0059] Inverters 15 and 16 convert the DC power stored in battery 12 into AC power and supply it to motor 3 and motor 14. They also convert the AC power generated by motor 3 and motor 14 when the vehicle decelerates into DC power to charge the battery.

[0060] (Drive unit)

[0061] Taking the drive motor 3 and inverter 15 as examples, the drive unit A of vehicle 1 will be described. Figure 2 This is a perspective view of drive unit A. As described above, drive unit A consists of a motor 3 and an inverter 15. The motor 3 and inverter 15 are arranged adjacent to each other and coaxially in the axial direction of the motor 3. Specifically, the central axis O of the motor 3 coincides with the central axis O of the inverter 15. The motor 3 (specifically, the housing of the motor 3) is formed in a cylindrical shape. The inverter 15 (specifically, the housing of the inverter 15) is formed in a cylindrical shape corresponding to that of the motor 3. The rotation shaft 3a of the motor 3 passes through the inverter 15 axially. The thickness Width of the inverter 15 is relatively thin, for example, 50 mm or less (preferably 30 mm or less). A cooling passage 61, described later, is provided inside the inverter 15. An inlet pipe 62 and an outlet pipe 63 for cooling, communicating with the cooling passage 61, are connected to the upper part of the inverter.

[0062] Figure 3 This is a cross-sectional view of the motor 3 viewed from the inverter 15 side. The motor 3 has coils 17. Specifically, coils 17u, 17v, and 17w for the U-phase, V-phase, and W-phase are respectively wound on the stator of the motor 3. The U-phase coil 17u is arranged in two positions opposite to each other in the radial direction of the motor 3. Similarly, the V-phase coil 17v is arranged in two positions opposite to each other in the radial direction of the motor 3. Similarly, the W-phase coil 17w is arranged in two positions opposite to each other in the radial direction of the motor 3.

[0063] Three motor-side terminal blocks 18 are provided on the outer periphery of the motor 3. These three terminal blocks 18 correspond to the coils 17u, 17v, and 17w of phases U, V, and W, respectively. Leads (not shown) are drawn from each phase U coil 17u located at two positions. These two leads are bundled together and connected to the motor-side terminal blocks 18. The same applies to phase V coil 17v and phase W coil 17w. An iron core 27 serving as the rotor, along with permanent magnets 28 with N and S poles, are fixed to the rotating shaft 3a.

[0064] Figure 4This is the circuit diagram of inverter 15. Inverter 15 has a smoothing capacitor 19 and multiple power modules 20. The smoothing capacitor 19 smooths the voltage applied to the power modules 20. The multiple power modules 20 constitute the inverter circuit, which converts DC voltage into AC voltage.

[0065] The multiple power modules 20 include a U-phase power module 20u, a V-phase power module 20v, and a W-phase power module 20w. The U-phase power module 20u is connected to the U-phase coil 17u of the motor 3. The V-phase power module 20v is connected to the V-phase coil 17v of the motor 3. The W-phase power module 20w is connected to the W-phase coil 17w of the motor 3.

[0066] The power module 20 consists of two components, a lower arm element 21 and an upper arm element 22, which act as switching elements. In each phase of the power module 20, when one of the lower arm element 21 and the upper arm element 22 is turned on, the other of the lower arm element 21 and the upper arm element 22 is turned off. As a result, three-phase alternating current is supplied to the motor 3.

[0067] Here, power module 20 includes SiC-MOSFETs. Figure 5 This section compares SiC-MOSFETs with IGBTs. A SiC-MOSFET is a MOSFET (metal-oxide-semiconductor field-effect transistor) made of silicon carbide (SiC), forming a chip 24 comprising a lower arm element 21, an upper arm element 22, and other control elements. The lower surface of the chip 24 is fixed to a silicon substrate with solder. On the upper surface of the chip 24, a copper block 25 serving as a heat transfer block is fixed with solder. IGBTs (Insulated Gate Bipolar Transistors) are similar.

[0068] like Figure 5 As shown, the surface area of ​​the chip 24 made of SiC-MOSFET is smaller than the surface area of ​​the chip 24' made of IGBT. Consequently, the size of the copper block 25 disposed on the upper side of the SiC-MOSFET (chip) 24 is smaller than the size of the copper block 25' disposed on the upper side of the IGBT (chip) 24'. The SiC-MOSFET exhibits superior heat resistance compared to the IGBT.

[0069] Figure 6The detailed structure of the power module 20 is shown in a perspective view and circuit diagram. Each power module 20 has a wide, flat shape. Specifically, the dimension of each power module 20 in the width direction W is longer than its dimension in the thickness direction t. The power module 20 has a generally cuboid shape. The width direction W includes a first width direction W1 and a second width direction W2 that are orthogonal to each other. Hereinafter, the side of the power module 20 in the thickness direction will sometimes be referred to as the lower side, and the other side in the thickness direction will be referred to as the upper side.

[0070] The power module 20 has a lower surface 31 on its lower side (one side, one side in the thickness direction) as a first cooled surface. The power module 20 has an upper surface 32 on its upper side. The power module 20 has a first end face 33 on one side in the first width direction W1. The power module 20 has a second end face 34 on the other side in the first width direction W1.

[0071] A negative input terminal 35 is connected to the lower side of the first end face 33 and to one side of the second width direction W2. A positive input terminal 36 is connected to the upper side of the first end face 33 and to the other side of the second width direction W2. The negative input terminal 35 and the positive input terminal 36 are arranged at intervals in the vertical direction (thickness direction). An output terminal 37 is connected to the center of the second end face 34.

[0072] The lower arm component 21 and the upper arm component 22 are housed within the package (box) of the power module 20. The negative input terminal 35 is connected to the lower arm component 21. The positive input terminal 36 is connected to the upper arm component 22. The output terminal 37 is connected between the lower arm component 21 and the upper arm component 22.

[0073] Figure 7 This is a cross-sectional view of the inverter 15 viewed from the side opposite to the motor 3. Figure 8 This is a longitudinal sectional view taken along line VIII-VIII of inverter 15. (Example) Figure 7 As shown, a shaft through hole 40 is provided at the center of the inverter 15, through which the rotating shaft 3a of the motor 3 passes. A cylindrical flange portion 41 is formed around the shaft through hole 40. The smoothing capacitor 19 is arranged to extend along the flange portion 41.

[0074] Each power module 20 (U-phase power module 20u, V-phase power module 20v, and W-phase power module 20w) is positioned closer to the outer periphery than the smoothing capacitor 19. The power modules 20 are arranged circumferentially along the motor 3, closer to the outer periphery than the smoothing capacitor 19. The input terminals 35 and 36 (first end face 33) and the output terminal 37 (second end face 34) of each power module 20 face circumferentially toward the motor 3 (inverter 15). Each power module 20 is arranged such that its thickness direction t aligns with the axial direction of the motor 3. The smoothing capacitor 19 and each power module 20 are arranged within the space defined by the outer peripheral wall portion 42 and the flange portion 41 of the inverter 15.

[0075] like Figure 7 , Figure 8 As shown, a heat dissipation device 60 is provided on the side of the inverter 15 closest to the motor 3. The heat dissipation device 60 is mainly used to cool the power modules 20. The heat dissipation device 60 is arranged between the outer peripheral wall portion 42 and the flange portion 41 of the inverter 15. The heat dissipation device 60 has an upper wall portion 60a, an outer peripheral wall portion 60b, a lower wall portion 60c, and an inner peripheral wall portion 60d.

[0076] The upper surface 65 of the upper wall portion 60a of the heat dissipation device 60 forms a placement surface (hereinafter sometimes referred to as "placement surface 65") orthogonal to the axial direction of the motor 3. The lower surface (first cooling surface) 31 of each power module 20 (U-phase power module 20u, V-phase power module 20v, and W-phase power module 20w) faces the motor 3. In detail, the lower surfaces (first cooling surfaces) 31 of each power module 20 are arranged on the same placement surface 65.

[0077] like Figure 7 , Figure 8 As shown, the smooth capacitor 19 is formed by covering an assembly of multiple cylindrical capacitors 45 with a plate from both sides in the thickness direction. The smooth capacitor 19 has a lower surface 19a, serving as a third cooled surface, on its lower side (one side in the thickness direction). The smooth capacitor 19 has an upper surface 19b on the side opposite to the lower surface 19a. Both the lower surface 19a and the upper surface 19b of the smooth capacitor 19 are made of a plate. The lower surface (third cooled surface) 19a of the smooth capacitor 19 faces the motor 3. Specifically, the lower surface (third cooled surface) 19a of the smooth capacitor 19 is placed on a mounting surface 65.

[0078] like Figure 7 , Figure 8As shown, the smoothing capacitor 19 and each power module 20 are interconnected via a negative-side busbar 51 and a positive-side busbar 52, which serve as input busbars 50 (hereinafter, sometimes simply referred to as "busbar 50"). The negative-side busbar 51 and the positive-side busbar 52 are plate-shaped. Specifically, the dimensions of the negative-side busbar 51 and the positive-side busbar 52 in the width direction W and the length direction L are longer than their dimensions in the thickness direction t.

[0079] like Figure 7 As shown, the negative-side busbar 51 and the positive-side busbar 52 are formed wide, extending circumferentially along the motor 3 (inverter 15). In other words, the negative-side busbar 51 and the positive-side busbar 52 are formed wide, extending along the arrangement direction of each power module 20. The width direction W of the negative-side busbar 51 and the positive-side busbar 52 extends circumferentially (arc-shaped) along the motor 3. The negative-side busbar 51 and the positive-side busbar 52 are fan-shaped. The length direction L of the negative-side busbar 51 and the positive-side busbar 52 extends radially along the motor 3.

[0080] One end 51i of the negative-side busbar 51 is connected to the negative terminal 19c disposed on the lower surface 19a side of the smooth capacitor 19. The other end 51o of the negative-side busbar 51 is connected to the negative-side input terminal 35 of each power module 20. One end 52i of the positive-side busbar 52 is connected to the positive terminal 19d disposed on the upper surface 19b side of the smooth capacitor 19. The other end 52o of the positive-side busbar 52 is connected to the positive-side input terminal 36 of each power module 20.

[0081] The negative-side busbar 51 has a lower surface 51a on its lower side (one side, the thickness direction side) that serves as a second cooled surface. The lower surface (second cooled surface) 51a of the negative-side busbar 51 faces the motor 3. In detail, the lower surface (second cooled surface) 51a of the negative-side busbar 51 is placed on the placement surface 65.

[0082] like Figure 7 As shown, an output busbar 54 is connected to the output terminal 37 of each power module 20. There are three output busbars 54, corresponding to the U-phase, V-phase, and W-phase. The output busbars 54 are sandwiched between each power module 20 and each coil 17. The output busbars 54 are plate-shaped. Besides the output busbars 54, wire harnesses or similar devices can also be sandwiched between each power module 20 and each coil 17.

[0083] Three inverter-side terminal blocks 46 are provided on the outer periphery of the inverter 15. Each inverter-side terminal block 46 corresponds to a power module 20. Output busbars 54 extend to the inverter-side terminal blocks 46. Conductive components (busbars, wire harnesses, etc.) are sandwiched between the inverter-side terminal blocks 46 and the motor-side terminal blocks 18.

[0084] (Inductance of the busbar)

[0085] Figure 9 This is a 3D view of busbar 50. Figure 10 This is a graph showing the relationship between the size of the busbar 50 and the inductor sensitivity. The inventors of this application conducted in-depth research and, as a result, discovered the following regarding the relationship between the size of the busbar 50 and the inductor sensitivity.

[0086] like Figure 9 , Figure 10 As shown, the larger the width dimension W (mm) of the busbar 50, the smaller the inductive sensitivity (nH) of the busbar 50.

[0087] Basically, the larger the length L (mm) of the busbar 50, the greater its inductive sensitivity (nH). However, as Figure 10 As shown in the curve at the very center, there exists a minimum (inflection point) in the relationship between the length L (mm) of busbar 50 and the inductance sensitivity (nH). This means that there are cases where the inductance sensitivity (nH) can be the same regardless of the length L. Specifically, the inductance sensitivity (nH) of busbars 50 (51, 52) is a function of the length L (mm) from one end 51i, 52i (terminals 19c, 19d of the smoothing capacitor 19) to the other end 51o, 52o (input terminals 35, 36 of each power module 20). This function has a minimum value M, such that the inductance sensitivity K (nH) is the same for unequal first length L1 (mm) and second length L2 (mm). The second length L2 (mm) is longer than the first length L1 (mm).

[0088] Even if the thickness dimension t (mm) of busbar 50 changes, the inductive sensitivity (nH) of busbar 50 remains unchanged.

[0089] like Figure 7 As shown, the width of the negative electrode side busbar 51 is approximately equal to the width of the positive electrode side busbar 52. Figure 8As shown, the length L- of the negative-side busbar 51 and the length L+ of the positive-side busbar 52 are not equal. The length L- of the negative-side busbar 51 corresponds to the first length L1. The length L+ of the positive-side busbar 52 corresponds to the second length L2. The length L+ (second length L2) of the positive-side busbar 52 is longer than the length L- (first length L1) of the negative-side busbar 51. However, due to the existence of the aforementioned minimum value M, the inductance of the negative-side busbar 51 and the inductance of the positive-side busbar 52 are equal.

[0090] (Cooling path)

[0091] Figure 11 This is a cross-sectional view of the cooling passage 61 of the inverter 15, viewed from the side of the motor 3. (See image below.) Figure 8 , Figure 11 As shown, a cooling passage (cooling sleeve) 61, serving as a cooling section, is provided inside the heat dissipation device 60. The cooling passage 61 is divided by an upper wall portion 60a, an outer peripheral wall portion 60b, a lower wall portion 60c, and an inner peripheral wall portion 60d. When viewed from the axial direction of the motor 3 (inverter 15), the cooling passage 61 spans the entire circumference and is formed in a ring shape (annular or cylindrical). The rotation shaft 3a of the motor 3 passes through the inner side of the inner peripheral wall portion 60d. As described above, the upper surface of the upper wall portion 60a of the heat dissipation device 60 is a placement surface 65.

[0092] The cooling passage 61 is positioned closer to the motor 3 than the mounting surface 65. The cooling medium H flows through the cooling passage 61. The cooling medium H can be cooling water, cooling oil, etc.

[0093] Furthermore, multiple fins 64 serving as cooling units are provided inside the heat dissipation device 60 (cooling passage 61). The fins 64 extend downward from the upper wall portion 60a within the cooling passage 61. That is, the fins 64 are provided closer to the motor 3 than the placement surface 65.

[0094] like Figure 8 , Figure 11 As shown, when viewed from the axial direction of the motor 3 (inverter 15), the cooling passage (cooling section) 61 faces the lower surface (first cooled surface) 31 of each power module 20, the lower surface (second cooled surface) 51a of the negative side busbar 51, and the lower surface (third cooled surface) 19a of the smoothing capacitor 19.

[0095] Similarly, when viewed from the axial direction of the motor 3, the fins (cooling section) 64 face the lower surface (first cooled surface) 31 of each power module 20, the lower surface (second cooled surface) 51a of the negative side busbar 51, and the lower surface (third cooled surface) 19a of the smooth capacitor 19.

[0096] like Figure 11As shown, an inlet pipe 62 and an outlet pipe 63 are connected to the upper part of the outer peripheral wall 42 of the inverter 15. The inlet pipe 62 and the outlet pipe 63 are connected to the cooling passage 61. The cooling medium H introduced into the cooling passage 61 via the inlet pipe 62 is guided by the outer peripheral wall 60b and the inner peripheral wall 60d, flows circumferentially within the cooling passage 61, and is discharged to the outside via the outlet pipe 63. It should be noted that a guide plate 66 may also be provided on the downstream side of the inlet pipe 62.

[0097] (Function and effects of the first embodiment)

[0098] According to this embodiment, the large lower surface (first cooled surface) 31 of the wide, flat power module 20 faces the cooling passage 61 and fins 64, which serve as cooling units. Therefore, the cooling area of ​​the cooling units 61 and 64 on the power module 20 can be increased. In this way, even when the cooling units 61 and 64 only cool one side (lower surface, first cooled surface) 31 of the power module 20, sufficient cooling capacity can be ensured.

[0099] By extending the negative-side busbar 51 along the arrangement direction of each power module 20 (circumferential direction of the motor 3), the width of the negative-side busbar 51 can be increased. Since the large lower surface (second cooled surface) 51a of the wide, plate-shaped negative-side busbar 51 faces the cooling sections 61 and 64, the heat dissipation area from the negative-side busbar 51 to the cooling sections 61 and 64 can be increased. In this way, even if the cooling capacity of the power modules 20 by the cooling sections 61 and 64 is insufficient, this insufficient cooling capacity can be compensated for.

[0100] The lower surfaces (first cooled surfaces) 31 of each power module 20 (U-phase power module 20u, V-phase power module 20v, and W-phase power module 20w) are arranged on the same placement surface 65 orthogonal to the axis of the motor 3, thus shortening the axial length of the inverter 15. Since the cooling units 61 and 64 are only provided on one side (lower surface, first cooled surface) 31 of the power module 20, the inverter 15 can be miniaturized compared to the case where the cooling units 61 and 64 are provided on both sides of the power module 20.

[0101] The above measures enable sufficient cooling of the power module 20 and allow for miniaturization of the drive unit A, which consists of the motor 3 and the inverter 15.

[0102] By allowing the cooling medium H to flow in the cooling passage 61, which serves as the cooling unit, the cooling capacity of the cooling unit for the power module 20 can be further increased.

[0103] Because the SiC-MOSFET chip 24 included in the power module 20 is small, the copper block 25 disposed on the SiC-MOSFET chip 24 as a heat transfer block is also small (see reference). Figure 5 Therefore, to effectively cool the power module 20 on both sides, expensive ceramic substrates (e.g., SiN) need to be placed on both sides of the SiC-MOSFET chip 24. Therefore, cooling the power module 20 on one side and improving the cooling effect on that side is more cost-effective than cooling the power module 20 on both sides.

[0104] In addition to the power modules 20, the smoothing capacitor 19 can also be cooled by the cooling units 61 and 64.

[0105] By arranging each power module 20 along the circumference of the motor 3 at a position closer to the outer periphery than the smoothing capacitor 19, and extending the width direction W of the negative side busbar 51 along the circumference of the motor 3, the width of the negative side busbar 51 can be easily widened. This allows for a simple increase in the heat dissipation area from the negative side busbar 51 to the cooling sections 61 and 64.

[0106] Since cooling units 61 and 64 are located on the side of motor 3, it is also beneficial for cooling the wiring (e.g., output busbar 54) connecting each coil 17 and each power module 20 of motor 3.

[0107] like Figure 1 As shown by the double-dotted line, conventionally, the inverter 15' is mostly arranged near the second battery component 12b' of the battery 12'. According to this embodiment, since the inverter 15 can be arranged adjacent to the motor 3 in the axial direction of the motor 3, it is not necessary to arrange the inverter 15 near the second battery component 12b. This increases the flexibility in the layout of the second battery component 12b, allowing for a larger second battery component 12b.

[0108] (Inductance reduction and equalization)

[0109] By increasing the width of each busbar 51 and 52, the inductance of each busbar 51 and 52 can be reduced.

[0110] Since the smoothing capacitor 19 and each power module 20u, 20v, 20w are placed on the same mounting surface 65, the distance between each busbar 51, 52 connecting the smoothing capacitor 19 and each power module 20u, 20v, 20w is shortened. This reduces the inductance of each busbar 51, 52.

[0111] Since the motor 3 and the inverter 15 are arranged adjacent to each other in the axial direction, the electrical path length between each power module 20u, 20v, 20w and each coil 17u, 17v, 17w is shortened. As a result, the inductance of the electrical path (including the output busbar 54) connecting each power module 20u, 20v, 20w and each coil 17u, 17v, 17w can be reduced.

[0112] The power modules 20u, 20v, and 20w are arranged circumferentially along the motor 3 at a position closer to the outer periphery than the smoothing capacitor 19, thus ensuring that the distance between the smoothing capacitor 19 and each power module 20u, 20v, and 20w is equal. Furthermore, by widening each busbar 51 and 52 in a manner that extends circumferentially along the motor 3, the inductance of the electrical path between the smoothing capacitor 19 and each power module 20u, 20v, and 20w can be equalized in each busbar 51 and 52.

[0113] By utilizing the aforementioned minimum (inflection point) M (reference) Figure 10 Thus, even though the length dimension L- (first length L1) of the negative side busbar 51 and the length dimension L+ (second length L2) of the positive side busbar 52 are not equal, the inductance of the negative side busbar 51 and the inductance of the positive side busbar 52 can be balanced.

[0114] (First variation of the first embodiment)

[0115] Figure 12 The first variation of the first embodiment involves the equivalent of Figure 11 The figure shows that, according to this modified example, the cooling section (cooling passage 61 and fins 64) does not face the lower surface (third cooled surface) 19a of the smooth capacitor 19 at all. The cooling sections 61 and 64 do not face a portion of the lower surface (second cooled surface) 51a of the negative electrode side busbar 51.

[0116] Since the heat generated by the smoothing capacitor 19 is less than that generated by the power module 20, there is sometimes no problem even if the smoothing capacitor 19 is not cooled by the cooling units 61 and 64.

[0117] If the cooling sections 61 and 64 face a portion of the lower surface (second cooled surface) 51a of the negative electrode side busbar 51, then a heat dissipation effect from the negative electrode side busbar 51 to the cooling sections 61 and 64 can be obtained to some extent.

[0118] (Second variation of the first embodiment)

[0119] Figure 13 The second variation of the first embodiment involves the equivalent of Figure 7The diagram shows that in this variation, the inverter 16 is arranged adjacent to the in-wheel motor 14 in the axial direction (vehicle width direction) (see figure). Figure 1 The inverter 16 does not have a through hole 40 or a flange 41. The smoothing capacitor 19 is cylindrical and arranged at the center of the inverter 16. The heat dissipation device 60 does not have an inner peripheral wall 60d. When viewed from the axial direction of the motor 3, the cooling passage 61 is circular without holes.

[0120] (Other variations of the first embodiment)

[0121] The cooling medium H flowing in the cooling passage 61 can be, for example, air. Furthermore, the cooling section may not include the cooling passage 61, for example, it may consist only of fins 64. The cooling section can be a solid cooling component.

[0122] The cooling unit does not need to be located on the entire circumference, or it can be located only on the circumferential portion facing each power module 20.

[0123] Alternatively, instead of the negative side busbar 51 having a second cooled surface, the positive side busbar 52 has a second cooled surface facing the motor 3 and placed on the placement surface 65 on one side (the side in the thickness direction).

[0124] Although not shown, each output busbar 54 can be formed wide, extending circumferentially along the motor 3. In other words, the width of the output busbar 54 can extend circumferentially (in an arc shape). The output busbar 54 can be fan-shaped. This makes it easier to widen the output busbar 54, thus making it easier to reduce the inductance of the output busbar 54 (see reference). Figure 10 ).

[0125] The placement surface 65 can also be composed of multiple surfaces located on the same plane orthogonal to the axis of the motor 3.

[0126] <Second Implementation>

[0127] Figure 14 The second embodiment is equivalent to Figure 7 The figure is a cross-sectional view of the inverter 15 viewed from the opposite side of the motor 3. Figure 15 The second embodiment is equivalent to Figure 8 The figure shown is a longitudinal sectional view of the inverter 15. Hereinafter, detailed descriptions will sometimes be omitted for structures identical to those described in the above embodiments.

[0128] In this embodiment, each power module 20 (U-phase power module 20u, V-phase power module 20v, and W-phase power module 20w) is arranged closer to the outer periphery than the smoothing capacitor 19. The power modules 20 are arranged circumferentially along the motor 3 at a position closer to the outer periphery than the smoothing capacitor 19.

[0129] The input terminals 35 and 36 (first end face 33) and the output terminal 37 (second end face 34) of each power module 20 are radially oriented towards the motor 3 (inverter 15). Specifically, the input terminals 35 and 36 (first end face 33) of each power module 20 face the inner periphery. The output terminal 37 (second end face 34) of each power module 20 faces the outer periphery. The power modules 20 are arranged radially with the center O of the inverter 15 (motor 3) as the starting point.

[0130] Similarly to the above embodiments, the lower surface (first cooled surface) 31 of each power module 20, the lower surface (second cooled surface) 51a of the negative electrode side busbar 51, and the lower surface (third cooled surface) 19a of the smooth capacitor 19 are placed on the placement surface 65.

[0131] like Figure 14 As shown, the width of the negative electrode side busbar 51 is equal to the width of the positive electrode side busbar 52. Figure 15 As shown, the length L- of the negative side busbar 51 is equal to the length L+ of the positive side busbar 52. Therefore, the inductance of the negative side busbar 51 and the inductance of the positive side busbar 52 are equal.

[0132] The other structures are the same as in the first embodiment.

[0133] <Third Implementation Method>

[0134] Figure 16 The third embodiment is equivalent to Figure 7 The figure is a cross-sectional view of the inverter 15 viewed from the opposite side of the motor 3. Figure 17 The third embodiment is equivalent to Figure 8 The figure shown is a longitudinal sectional view of the inverter 15. Hereinafter, detailed descriptions will sometimes be omitted for structures identical to those described in the above embodiments.

[0135] like Figure 16 , Figure 17 As shown, the negative input terminal 35 is connected to the lower side of the first end face 33 of each power module 20. The positive input terminal 36 is connected to the lower side of the second end face 34 of each power module 20. The output terminal 37 is connected to the center of the upper surface 32 of each power module 20.

[0136] The negative-side busbar 51 connects the negative terminal 19c of the smoothing capacitor 19 to the negative-side input terminal 35 of each power module. The positive-side busbar 52 connects the positive terminal 19d of the smoothing capacitor 19 to the positive-side input terminal 36 of each power module 20.

[0137] The positive-side busbar 52 extends from the positive terminal 19d (one end 52i) of the smoothing capacitor 19, extending along the upper surface 32 from the first end face 33 side to the second end face 34 side of each power module 20. Then, the positive-side busbar 52 bends downwards, extending along the second end face 34 to the lower positive-side input terminal 36 (the other end 52o). In other words, the positive-side busbar 52 extends around each power module 20 from the upper surface 32 side. Each output busbar 54 extends upwards from the output terminal 37 of the upper surface 32 of each power module 20. Three openings are provided on the positive-side busbar 52 for the upwardly extending output busbars 54 to pass through.

[0138] Similarly to the above embodiments, the lower surface (first cooled surface) 31 of each power module 20, the lower surface (second cooled surface) 51a of the negative electrode side busbar 51, and the lower surface (third cooled surface) 19a of the smooth capacitor 19 are placed on the placement surface 65.

[0139] like Figure 16 As shown, the width of the negative electrode side busbar 51 is equal to the width of the positive electrode side busbar 52. Figure 17 As shown, the length dimension (L-) of the negative electrode side busbar 51 is not equal to the length dimension (the sum of La+ and Lb+) of the positive electrode side busbar 52. The length dimension (L-) of the negative electrode side busbar 51 corresponds to the first length L1. The length dimension (the sum of La+ and Lb+) of the positive electrode side busbar 52 corresponds to the second length L2. The length dimension (the sum of La+ and Lb+, the second length L2) of the positive electrode side busbar 52 is longer than the length dimension (L-, the first length L1) of the negative electrode side busbar 51. However, due to the aforementioned minimum value M (refer to...) Figure 10 Due to the presence of ), the inductance of the negative side busbar 51 and the inductance of the positive side busbar 52 are equal.

[0140] It should be noted that the conditions (materials, etc.) of the negative electrode side busbar 51 and positive electrode side busbar 52 involved in this embodiment are different from those in the above embodiment. Therefore, the above minimum value M (refer to...) Figure 10 The shapes are also different. Specifically, the interval (difference) between the first length L1 and the second length L2 is greater than the interval described in the above embodiment.

[0141] The other structures are the same as in the second embodiment.

[0142] (First variation of the third embodiment)

[0143] Figure 18 The first variation of the third embodiment involves the equivalent of Figure 8 The figure is a longitudinal sectional view of the inverter 15. In the above embodiment, each power module 20 houses both the lower arm element 21 and the upper arm element 22 within a single package, but this is not the case in this variation. In this variation, each power module 20 is separated into a first package 20a housing the lower arm element 21 and a second package 20b housing the upper arm element 22.

[0144] (Second variation of the third embodiment)

[0145] Figure 19 This is a perspective view of the power module 20 and busbar 50 in the second variation of the third embodiment. In this variation, the power modules 20 (U-phase power module 20u, V-phase power module 20v, and W-phase power module 20w) are arranged in a straight line. The width directions of the busbars 51 and 52 extend vertically (in the arrangement direction of the power modules 20).

[0146] <Other Implementation Methods>

[0147] The present disclosure has been described above through preferred embodiments, but the above description is not a limitation and various changes can be made.

[0148] -Industry Applicability-

[0149] This disclosure can be applied to vehicle drive units, and is therefore extremely useful and has high industrial applicability.

Claims

1. A drive unit for a vehicle, comprising an electric motor and an inverter having a smoothing capacitor and a plurality of power modules arranged adjacent to each other along the axial direction of the electric motor, characterized in that: The smoothing capacitor and each of the power modules are interconnected via busbars. Each of the power modules has a wide, flat shape, and each of the power modules has a first cooling surface on one side facing the motor side. The first cooled surfaces of each power module are arranged on a placement surface orthogonal to the axial direction. The busbar is plate-shaped, and has a second cooling surface on one side facing the motor. One end of the busbar is connected to the smoothing capacitor. The other end of the busbar is connected to each of the power modules. The busbar is formed in a wide manner, extending along the arrangement direction of each of the power modules. The second cooled surface is placed on the placement surface. A cooling section is provided at a position closer to the motor side than the placement surface, facing the first and second surfaces to be cooled. The smoothing capacitor and each of the power modules are interconnected via a negative-side busbar and a positive-side busbar, which serve as the busbars. The length of one of the negative electrode side busbar and the positive electrode side busbar is a first length. The length of the other of the negative electrode side busbar and the positive electrode side busbar is the second length. The first length and the second length are not equal. At least one of the negative electrode side busbar and the positive electrode side busbar has the second cooled surface. The inductance of the busbar is a function of the length from one end of the busbar to the other end. The function has a minimum value such that the inductance is equal at the first length and the second length.

2. The drive unit of the vehicle according to claim 1, characterized in that: The cooling section includes a cooling passage for the flow of cooling medium.

3. The drive unit of the vehicle according to claim 1 or 2, characterized in that: The power module includes SiC-MOSFETs.

4. The drive unit of the vehicle according to claim 1 or 2, characterized in that: The smooth capacitor has a third cooled surface on one side facing the motor side. The third cooled surface is placed on the placement surface. The cooling section also faces the third surface being cooled.

5. The drive unit of the vehicle according to claim 1 or 2, characterized in that: Each of the power modules is positioned closer to the outer periphery than the smoothing capacitor. The busbar is formed in a wide manner, extending circumferentially along the motor.

6. The drive unit of the vehicle according to claim 1 or 2, characterized in that: When viewed from the axial direction of the motor, at least a portion of one of the negative-side busbar and the positive-side busbar overlaps with the other of the negative-side busbar and the positive-side busbar.

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