Vehicle drive device

Abstract

In a rear transaxle 1, an electric motor 2 is arranged side by side along the axial direction of a differential device 4 and an output shaft 14. A rotor shaft 15 of the electric motor 2 is formed in a hollow shape, a right output shaft 12 extends from the differential device 4 to the side opposite to the electric motor 2, and a left output shaft 13 extends from the differential device 4 to the electric motor 2 side and is rotatably inserted into the internal space of the rotor shaft 15. A speed reducer 3 includes a counter shaft 20 which is arranged in parallel with the output shaft 14 and the rotor shaft 15 so as to be separated from each other in the vehicle longitudinal direction, and is connected to the rotor shaft 15 and a differential case 24 of the differential device 4 via a plurality of gears. An oil pump 50 is arranged farther to the outer side in the vehicle width direction than a counter driven gear part 22 connecting the rotor shaft 15 and the counter shaft 20, and on the lower side of the counter shaft 20.

Description

Vehicle drive unit

[0001] The present invention relates to a vehicle drive device.

[0002] A conventional technology for a vehicle drive system has been known in which an electric motor and a differential gear are coaxially arranged, and an output shaft connected to one of the drive shafts from the differential gear is rotatably inserted into the internal space of a hollow motor output shaft, thereby achieving a compact configuration. For example, Patent Document 1 (JP-A-2005-102626) describes a power transmission system (vehicle drive system) having the above-described configuration, in which a motor housing surrounding the outer periphery of the motor is provided with a lubricating oil passage extending in the direction of the rotational axis on the outer periphery of the motor and an oil hole connecting the lubricating oil passage to the inner periphery of the motor housing. In this power transmission system, lubricating oil as a cooling medium is supplied to the outer periphery of the motor through the lubricating oil passage and the oil hole to cool the motor.

[0003] Japanese Patent Application Laid-Open No. 2020-128799

[0004] A vehicle drive system is equipped with a pump that pressure-feeds a cooling medium to be supplied to an electric motor. When installing such a pump, it is necessary to reduce the space inside the casing and achieve a compact vehicle drive system.

[0005] The present invention has been made in consideration of these problems, and its purpose is to reduce the size of a vehicle drive system in which an electric motor and a differential are arranged coaxially and which is equipped with a pump that pressure-feeds a cooling medium to the electric motor.

[0006] In order to achieve the above object, a vehicle drive device of the present invention includes an electric motor, an output shaft including a first output shaft and a second output shaft that are respectively connected to drive shafts that drive vehicle wheels and are arranged coaxially, a differential device interposed between the first output shaft and the second output shaft, a speed reducer that reduces the output of the electric motor and inputs it to the differential device, a pump that pressurizes and feeds a cooling medium that is supplied to the electric motor, and a casing that accommodates the electric motor, the differential device, the speed reducer, and the pump, wherein the electric motor is arranged side by side with the differential device along the axial direction of the output shaft, and The motor output shaft of the motor is formed hollow, the first output shaft extends from the differential device to the opposite side from the electric motor, and the second output shaft extends from the differential device to the electric motor side and is rotatably inserted into the internal space of the motor output shaft, the reducer is arranged parallel to and spaced apart from the output shaft and the motor output shaft in the fore-and-aft direction of the vehicle and includes an intermediate shaft connected to the motor output shaft and a power input portion of the differential device via a plurality of gears, and the pump is arranged outward in the vehicle width direction from the gears connecting the motor output shaft and the intermediate shaft and below the intermediate shaft.

[0007] According to the vehicle drive device of the present invention, the electric motor and the differential device are arranged coaxially, and the vehicle drive device equipped with a pump that pressure-feeds a cooling medium to the electric motor can be made smaller.

[0008] FIG. 4 is a perspective view showing the outer shape of the rear transaxle according to the present embodiment. FIG. 5 is a perspective view showing the internal structure of the rear transaxle according to the present embodiment. FIG. 6 is a cross-sectional view showing the internal structure of the rear transaxle according to the present embodiment. FIG. 7 is an explanatory diagram of the interior of the rear transaxle as viewed from the right. FIG. 8 is a cross-sectional view taken along line A-A in FIG. 4. FIG. 9 is an explanatory diagram schematically showing the flow of cooling oil from the oil pump to the oil cooler. FIG. 10 is an explanatory diagram schematically showing the flow of cooling oil after the oil cooler. FIG. 11 is a longitudinal cross-sectional view schematically showing the positional relationship between a first supply pipe and a second supply pipe and an electric motor.

[0009] An embodiment of a vehicle drive system embodying the present invention will now be described. FIG. 1 is a perspective view showing the exterior of a rear transaxle 1, which is a vehicle drive system according to one embodiment of the present invention. FIG. 2 is a perspective view showing the internal structure of the rear transaxle 1. FIG. 3 is a cross-sectional view showing the internal structure of the rear transaxle 1. Note that the rear transaxle 1 will be described below with reference to the vehicle direction when mounted on a vehicle.

[0010] 1 and 2, rear transaxle 1 is disposed between the left and right rear wheels of a vehicle and includes an electric motor 2, a reduction gear 3, and a differential 4. A right drive shaft 7 (drive shaft) that drives the right rear wheel of the vehicle and a left drive shaft 8 (drive shaft) that drives the left rear wheel of the vehicle are connected to rear transaxle 1. Rear transaxle 1 transmits driving force from electric motor 2 to the right and left rear wheels via right and left drive shafts 7 and 8, respectively, while allowing differential rotation between the right and left rear wheels.

[0011] The rear transaxle 1 is also equipped with an inverter 10 that controls the drive of the electric motor 2. The inverter 10 is disposed adjacent to the electric motor 2. The rear transaxle 1 is configured in the shape of a rectangular box, integrating the electric motor 2, the reduction gear 3, the differential device 4, and the inverter 10. As shown in FIG. 3 , the rear transaxle 1 is configured with the electric motor 2, the reduction gear 3, the differential device 4, and the inverter 10 housed within a casing 11.

[0012] The rear transaxle 1 includes an output shaft 14 that includes a right output shaft 12 (first output shaft) extending rightward from the differential 4 and a left output shaft 13 (second output shaft) extending leftward from the differential. One end (left end) of the right output shaft 12 is connected to the differential 4, and the other end (right end) is integrated with the right drive shaft 7. One end (right end) of the left output shaft 13 is connected to the differential 4, and the other end (left end) is connected to the left drive shaft 8. The right output shaft 12 and the left output shaft 13 are arranged coaxially side by side. The rear transaxle 1 also includes a countershaft 20 that is parallel to and spaced apart from the left output shaft 13 in the radial direction (hereinafter simply referred to as the "radial direction"). That is, as shown in FIG. 2 , the countershaft 20 is arranged parallel to and spaced apart from the output shaft 14 and the rotor shaft 15 in the vehicle front-rear and up-down directions. The countershaft 20 extends in the left-right direction so as to overlap the right end of the left output shaft 13 and the differential device 4 in the axial direction.

[0013] The electric motor 2 includes a rotor 2r as a rotor and a stator 2s as a stator, and is arranged side by side on the left side of the differential device 4 along the axial direction of the differential device 4 and the output shaft 14 (hereinafter simply referred to as the "axial direction"). The rotor shaft 15 (motor output shaft), which is the output shaft of the electric motor 2, is formed hollow, and the left output shaft 13 is inserted inside so that they can rotate relative to each other. A motor drive gear portion 21, which is, for example, a helical gear, is formed on the right end of the rotor shaft 15.

[0014] A counter driven gear unit 22 that meshes with the motor drive gear unit 21 is fixed to the left end of the counter shaft 20. In this embodiment, a parking gear 27 that is included in the vehicle's parking lock mechanism is integrally provided with the counter driven gear unit 22. A final drive gear unit 23, which is, for example, a helical gear or a spur gear, is formed at the right end of the counter shaft 20. The final drive gear unit 23 is configured to mesh with a final driven gear unit 25 that is fixed to a differential case 24, which is a power input portion of the differential device 4. The counter shaft 20, the motor drive gear unit 21, the counter driven gear unit 22, the final drive gear unit 23, and the final driven gear unit 25 form the reducer 3. The output of the electric motor 2 is transmitted from the rotor shaft 15 to the motor drive gear section 21, the counter driven gear section 22, the counter shaft 20, the final drive gear section 23, and the final driven gear section 25 in that order, and is input to the reducer 3, and is then output to the right output shaft 12 and the left output shaft 13 via the differential device 4.

[0015] The casing 11 of the rear transaxle 1 has a four-part structure, consisting of, lined up in the axial direction from the left side, a first casing 31, a second casing 32, a third casing 33, and a fourth casing 34. The first casing 31 is shaped like a lid that covers the left side of the electric motor 2, the second casing 32 houses the electric motor 2, the motor drive gear unit 21, and the counter driven gear unit 22, the third casing 33 houses the final drive gear unit 23 and the final driven gear unit 25, and the fourth casing 34 houses the reducer 3 and also serves as the right side wall of the casing 11.

[0016] The second casing 32 is provided with a first partition wall 37 that partitions the internal space of the casing 11 between the electric motor 2 and the motor drive gear unit 21 and between the inverter 10 and the counter driven gear unit 22. The third casing 33 is provided with a second partition wall 38 (center plate) that partitions the internal space of the casing 11 between the motor drive gear unit 21 and the counter driven gear unit 22 and between the final drive gear unit 23 and the final driven gear unit 25. The first partition wall 37 and the second partition wall 38 are provided with a through hole through which the left output shaft 13 passes.

[0017] A first bearing 41 (first bearing) that rotatably supports the left end portion of the left output shaft 13 and a second bearing 42 (second bearing) that rotatably supports the left end portion of the rotor shaft 15 are fixed to the first casing 31. The first bearing 41 and the second bearing 42 are arranged adjacent to each other in the axial direction. A third bearing 43 that rotatably supports the left end portion of the countershaft 20 is fixed to the first partition wall 37 of the second casing 32. A fourth bearing 44 (third bearing) that rotatably supports the right end portion of the rotor shaft 15 and a fifth bearing 45 (fourth bearing) that rotatably supports the left end portion of the differential case 24 are fixed to the second partition wall 38 of the third casing 33. The fourth bearing 44 is arranged on the left side of the second partition wall 38. The fifth bearing 45 is arranged on the right side of the second partition wall 38. A sixth bearing 46 that rotatably supports the right end of the countershaft 20 and a seventh bearing 47 (fifth bearing) that rotatably supports the right end of the differential case 24 are fixed to the fourth casing 34.

[0018] As described above, the countershaft 20 of the reduction gear 3 is disposed parallel to and spaced apart from the output shaft 14 and the rotor shaft 15 in the vehicle longitudinal direction and the up-down direction. More specifically, as shown in FIG. 2 , the countershaft 20 is located rearward and above the output shaft 14 and the rotor shaft 15 in the vehicle longitudinal direction. Therefore, a first space 91 ( FIGS. 1 and 2 ) is formed below the countershaft 20 and outward in the vehicle width direction from the meshing position between the motor drive gear unit 21 and the counter driven gear unit 22. More specifically, the first space 91 is located below the support portion 11 a ( FIGS. 1 and 3 ) of the final drive gear unit 23 and the sixth bearing 46 of the casing 11. As shown in FIG. 1 , the support portion 11 a protrudes beyond a flat surface 34 a that forms part of the outer surface of the fourth casing 34 on the vehicle width direction outside. The first space 91 also includes the space below the support portion 11 a that protrudes beyond the flat surface 34 a.

[0019] A second space 92 (FIGS. 1 and 2) is formed outward in the vehicle width direction from the final driven gear unit 25 and above the right output shaft 12. More specifically, the second space 92 is a space near the right end of the differential case 24 and above the support portion 11b (FIGS. 1 and 3) of the seventh bearing 47 of the casing 11. As shown in FIG. 3, the right end of the differential case 24 and the support portion 11b protrude beyond the flat surface 34a of the fourth casing 34, and the second space 92 includes the space near the right end of the differential case 24 and above the support portion 11b that protrude beyond this flat surface 34a. As shown in FIG. 3, the diameter of the differential case 24 decreases as it moves outward in the vehicle width direction from the mounting position of the final driven gear unit 25, and the diameters of the right end of the differential case 24 and the seventh bearing 47 are approximately the same.

[0020] In the rear transaxle 1 of this embodiment, components included in a cooling and lubrication structure for cooling the electric motor 2 and cooling and lubricating each bearing are arranged using the first space 91 and the second space 92. The cooling and lubrication structure of the rear transaxle 1 will be described below. FIG. 4 is an explanatory diagram of the interior of the rear transaxle 1 as viewed from the right, and FIG. 5 is a cross-sectional view taken along line A-A in FIG. 4 . FIG. 4 illustrates the state with the fourth casing 34 removed. In the following description, the first space on the differential gear 4 side of the second partition wall 38 in the casing 11 will be referred to as the "gear chamber 71," and the other space in the casing 11, i.e., the space on the electric motor 2 side of the second partition wall 38, will be referred to as the "motor chamber 72." The differential gear 4 and the final drive gear unit 23 and final driven gear unit 25 of the reduction gear 3 are arranged in the gear chamber 71.

[0021] As shown in Figures 2, 4, and 5, an oil pump 50 (pump), which is an electric hydraulic pump that pressurizes and pumps cooling oil OL (coolant), is disposed in the first space 91. The oil pump 50 is disposed so as to partially overlap the final driven gear unit 25 (shown by the two-dot chain line in Figure 5) when viewed from the vehicle longitudinal direction (see the dashed line in Figure 5). Note that the fourth casing 34 is formed with a first housing portion 341 that covers a portion of the oil pump 50 that protrudes beyond the flat surface 34a in the vehicle width direction, as shown in Figures 1 and 2.

[0022] As shown in Fig. 4, the oil pump 50 is fixed to the gear chamber 71 side surface of the second partition wall 38 by fastening at a plurality of fastening portions 511. A strainer 52 serving as a filtering device that communicates with a suction port (not shown) of the oil pump 50 is provided on the gear chamber 71 side surface of the second partition wall 38, and the oil pump 50 is also fixed to the strainer 52 by fastening at the fastening portions 512. As shown in Fig. 5, the second partition wall 38 is formed with a communication passage 381 that extends from the motor chamber 72 side surface and connects the strainer 52 to a lower space within the motor chamber 72. The oil pump 50 draws cooling oil OL stored in the lower space within the motor chamber 72 via the communication passage 381 and the strainer 52.

[0023] Within the gear chamber 71 in which the oil pump 50 is disposed, the final driven gear portion 25 extends up to the vicinity of the bottom surface of the casing 11. Therefore, the cooling oil OL (not shown) stored in the lower space of the gear chamber 71 is stirred by the final driven gear portion 25. Meanwhile, the counter driven gear portion 22 provided on the counter shaft 20 disposed above the output shaft 14 and the rotor shaft 15 is positioned above the final driven gear portion 25. Furthermore, the counter driven gear portion 22 has a smaller diameter than the final driven gear portion 25.

[0024] Therefore, as shown in FIG. 5 , there is sufficient space between the counter-driven gear portion 22 and the bottom surface of the casing 11 within the motor chamber 72, and the counter-driven gear portion 22 does not agitate the cooling oil OL stored in the lower space within the motor chamber 72. Even if the counter-driven gear portion 22 were configured to come into contact with the cooling oil OL within the motor chamber 72, the amount of agitation can be reduced compared to the gear chamber 71 side. Therefore, by having the oil pump 50 suck the cooling oil OL stored in the lower space within the motor chamber 72, it is possible to prevent the suction of cooling oil OL that has air mixed in due to agitation. As a result, it is possible to omit the installation of a separator with a gas-liquid separation function.

[0025] 1 and 2, an oil cooler 60 (cooling device) for cooling the cooling oil OL supplied to the electric motor 2 is disposed in the second space 92 of the rear transaxle 1. The oil cooler 60 is attached to the casing 11 (fourth casing 34) from the outside in the second space 92. Note that a housing portion for housing the oil cooler 60 may be provided in the casing 11 in the second space 92.

[0026] By utilizing the second space 92 in this manner, the oil cooler 60 can be disposed close to the electric motor 2. More specifically, the oil cooler 60 is disposed so that at least a portion thereof overlaps with an upper portion of the electric motor 2 when viewed in the vehicle width direction. The oil cooler 60 is supplied with cooling water from a cooling water supply hose 61, a portion of which is shown in FIG. 1 , and cools the cooling oil OL by performing heat exchange between the cooling oil OL and the cooling water inside the oil cooler 60. The cooling water after heat exchange is discharged through a cooling water discharge hose 62. In this embodiment, the cooling water is supplied from a cooling water supply source (not shown), exchanges heat with the inverter 10 in an inverter cooling unit 80 formed in a wall portion of the casing 11, and is then supplied to the oil cooler 60 from a cooling water outlet 81 via the cooling water supply hose 61.

[0027] Next, the supply path of the cooling oil OL from the oil pump 50 to the oil cooler 60 will be described. FIG. 6 is an explanatory diagram schematically illustrating the flow of the cooling oil OL from the oil pump 50 to the oil cooler 60. Note that the support portions 11a and 11b are omitted from FIG. 6 . As schematically illustrated in FIGS. 5 and 6 , a first discharge passage 101 extending to the second partition wall 38 is connected to the discharge port of the oil pump 50. The first discharge passage 101 is connected to a second discharge passage 102 formed on the surface of the second partition wall 38 facing the gear chamber 71. As illustrated in FIG. 4 , the second discharge passage 102 extends along the second partition wall 38 toward the opposite side (rearward) from the electric motor 2 in the vehicle longitudinal direction, and is connected to a third discharge passage 103. The third discharge passage 103 extends outward in the vehicle width direction along the wall portion 11c of the casing 11 opposite the electric motor 2 in the vehicle longitudinal direction. The third discharge passage extends to the flat surface 34a of the fourth casing 34 as shown in FIG.

[0028] Furthermore, as shown in FIG. 6 , a flat surface 34a forming a part of the outer surface of the fourth casing 34 is provided with an oil passage defining portion 343 in which a fourth discharge passage 104 connected to the third discharge passage 103 is formed. The oil passage defining portion 343 and the fourth discharge passage 104 extend from the oil pump 50 above the countershaft 20 and the support portion 11a of the casing 11 ( FIG. 1 ) and forward in the vehicle longitudinal direction, and are connected to the oil cooler 60. Note that the oil passage defining portion 343 shown in FIG. 6 is a schematic view and is not limited to this shape. In addition, in FIG. 1 , the device arranged outside the oil passage defining portion 343 is the drive actuator 70 of the parking lock mechanism (not shown) arranged inside the casing 11, and is arranged so as not to interfere with the fourth discharge passage 104 inside the oil passage defining portion 343. As a result, the oil pump 50 and the oil cooler 60 are connected by a first discharge passage 101 , a second discharge passage 102 , a third discharge passage 103 and a fourth discharge passage 104 .

[0029] Next, the supply path of the cooling oil OL after the oil cooler 60 will be described. FIG. 7 is an explanatory diagram schematically illustrating the flow of the cooling oil OL after the oil cooler 60. Note that the oil pump 50, the first housing portion 341, and the support portions 11a and 11b are omitted from FIG. 7 . As illustrated, a supply path 110 connected to the oil cooler 60 is formed within the wall of the casing 11. The supply path 110 extends in the vehicle longitudinal direction and is connected to a first supply path 111 and a second supply path 112. The first supply path 111 and the second supply path 112 are spaced apart from each other in the vehicle longitudinal direction and extend within the wall at the top of the casing 11 in the vehicle width direction.

[0030] However, the portion of the first supply path 111 that extends into the second casing 32 in which the electric motor 2 is disposed is constituted by the first supply pipe 111a, and the portion of the second supply path 112 that extends into the second casing 32 is constituted by the second supply pipe 112a. FIG. 8 is a vertical cross-sectional view schematically showing the positional relationship between the first supply pipe 111a and the second supply pipe 112a and the electric motor 2. As shown in the figure, the first supply pipe 111a and the second supply pipe 112a are disposed between the casing 11 (second casing 32) and the outer peripheral edge 2a of the electric motor 2, sandwiching the electric motor 2 in the front-to-rear direction of the vehicle. The first supply pipe 111a and the second supply pipe 112a are positioned below the top portion 2b of the electric motor 2 (the top portion of the stator 2s). The first supply pipe 111a and the second supply pipe 112a have a plurality of supply holes 111b, 112b formed along the vehicle width direction, as shown by the arrows in the figure, that supply cooling oil OL toward the stator 2s, and the stator 2s is cooled by the cooling oil OL from the supply holes 111b, 112b.

[0031] Returning to the description of FIG. 7 , the first supply passage 111 is connected at its terminal end to a third supply passage 113 formed within the wall of the casing 11. The third supply passage 113 extends to the vicinity of the first bearing 41, which supports the vicinity of the left end of the left output shaft 13, and the second bearing 42, which supports the left end of the rotor shaft 15, and supplies cooling oil OL to the first bearing 41 and the second bearing 42. The second supply passage 112 is connected to a fourth supply passage 114 formed within the wall of the casing 11, upstream of the second supply pipe 112a. The fourth supply passage 114 extends to the vicinity of the fourth bearing 44, which supports the right end of the rotor shaft 15, and the fifth bearing 45, which supports the vicinity of the left end of the differential case 24, and supplies cooling oil OL to the fourth bearing 44 and the fifth bearing 45. Furthermore, the supply passage 110 is connected to a fifth supply passage 115 formed in the wall of the casing 11 upstream (toward the oil cooler 60) of the first supply passage 111 and the second supply passage 112. The fifth supply passage 115 extends to the vicinity of the seventh bearing 47, which supports the right end portion of the differential case 24, and supplies cooling oil OL to the seventh bearing 47. With the above configuration, the cooling oil OL is supplied to the first bearing 41, the second bearing 42, the fourth bearing 44, the fifth bearing 45, and the seventh bearing 47, thereby cooling and lubricating each bearing. The cooling oil OL supplied to the electric motor 2 and each bearing arranged in the motor chamber 72 flows into the lower space of the motor chamber 72 and is stored therein.

[0032] As described above, in the rear transaxle 1 (vehicle drive system) of this embodiment, the electric motor 2 is arranged alongside the differential device 4 in the axial direction of the output shaft 14. The rotor shaft 15 (motor output shaft) of the electric motor 2 is formed hollow, with the right output shaft 12 extending from the differential device 4 to the opposite side of the electric motor 2 and the left output shaft 13 extending from the differential device 4 towards the electric motor 2 and rotatably inserted into the internal space of the rotor shaft 15. The reducer 3 is arranged parallel to and spaced apart from the output shaft 14 and the rotor shaft 15 in the fore-and-aft direction of the vehicle, and includes a counter shaft 20 (intermediate shaft) connected to the rotor shaft 15 and the differential case 24 (power input portion) of the differential device 4 via a motor drive gear section 21, a counter driven gear section 22, a final drive gear section 23, and a final driven gear section 25 (multiple gears), and the oil cooler 60 is arranged outside the vehicle width direction of the final driven gear section 25 that connects the counter shaft 20 and the differential case 24 of the differential device 4, and above the right output shaft 12.

[0033] This configuration allows the oil cooler 60 to be located in the second space 92, thereby saving space within the rear transaxle 1. Furthermore, the oil cooler 60 can be located closer to the electric motor 2, which is axially aligned with the differential 4. As a result, heat transfer from the casing 11 to the cooling oil OL before it is supplied from the oil cooler 60 to the electric motor 2 is minimized, allowing the electric motor 2 to be efficiently cooled. Therefore, the rear transaxle 1 of this embodiment allows for compactness and efficient cooling of the electric motor 2 in a vehicle drive system in which the electric motor 2 and the differential 4 are coaxially arranged and the oil cooler 60 cools the cooling oil OL supplied to the electric motor 2. The oil cooler 60 may be located at a position offset from above the right output shaft 12, as long as it is located in a space at least outboard of the final driven gear portion 25 in the vehicle width direction.

[0034] Furthermore, the oil cooler 60 is positioned so that it at least partially overlaps the electric motor 2 when viewed from the vehicle width direction. This configuration allows the height of the rear transaxle 1 to be reduced, and the oil cooler 60 can be positioned closer to the electric motor 2, allowing the electric motor 2 to be cooled more efficiently.

[0035] In addition, the oil coolers 60 are arranged at intervals in the longitudinal direction of the vehicle, extend along the vehicle width direction, and are connected to a first supply passage 111 and a second supply passage 112 that supply cooling oil OL to the electric motor 2, the first supply passage 111 including a first supply pipe 111a extending along the vehicle width direction, and the second supply passage 112 including a second supply pipe 112a extending along the vehicle width direction, and the first supply pipe 111a and the second supply pipe 112a are arranged to sandwich the outer peripheral edge 2a of the electric motor 2 in the longitudinal direction of the vehicle so as to be located between the casing 11 and the outer peripheral edge 2a of the electric motor 2.

[0036] With this configuration, the first supply pipe 111a and the second supply pipe 112a can be provided using the space between the casing 11 and the outer peripheral edge 2a of the electric motor 2, so that the first supply pipe 111a and the second supply pipe 112a can be provided at a position lower than the top 2b of the electric motor 2. As a result, the height of the rear transaxle 1 can be reduced.

[0037] The rear transaxle 1 also includes a first bearing 41 (first bearing) that rotatably supports the end of the left output shaft 13 on the electric motor 2 side, a second bearing 42 (second bearing) that rotatably supports the end of the rotor shaft 15 opposite the differential device 4, a fourth bearing 44 (third bearing) that rotatably supports the end of the rotor shaft 15 on the differential device 4 side, a fifth bearing 45 (fourth bearing) that rotatably supports the end of the differential case 24 of the differential device 4, a third supply path 113 that is connected to the first supply path 111 and supplies cooling oil OL to the first bearing 41 and the second bearing 42, and a fourth supply path 114 that is connected to the second supply path 112 and supplies cooling oil OL to the fourth bearing 44 and the fifth bearing 45.

[0038] With this configuration, the first bearing 41, the second bearing 42, the fourth bearing 44, and the fifth bearing 45 arranged along the output shaft 14 can be lubricated by supplying cooling oil OL from the oil cooler 60 arranged in the second space close to the output shaft 14. Furthermore, the amount of cooling oil OL supplied to the first bearing 41 and the second bearing 42 via the first supply path 111 and the third supply path 113 and the amount of cooling oil OL supplied to the fourth bearing 44 and the fifth bearing 45 via the second supply path 112 and the fourth supply path 114 can be made uniform. As a result, the cooling oil OL can be supplied to the first bearing 41, the second bearing 42, the fourth bearing 44, and the fifth bearing 45 in a balanced manner, allowing for appropriate lubrication.

[0039] The rear transaxle 1 also includes a seventh bearing 47 (fifth bearing) that rotatably supports an end portion of the differential device 4 that is located on the outer side in the vehicle width direction of a portion of the differential case 24 that is supported by the fifth bearing 45, and a fifth supply passage 115 that extends from the oil cooler 60 side of the first supply passage 111 and the second supply passage 112 and supplies cooling oil OL to the seventh bearing 47. With this configuration, the cooling oil OL can be supplied from the oil cooler 60 that is located in the second space adjacent to the seventh bearing 47, which is arranged along the output shaft 14, to efficiently cool and lubricate the seventh bearing 47.

[0040] Furthermore, in the rear transaxle 1 of this embodiment, the oil pump 50 (pump) is positioned outward in the vehicle width direction from the counter driven gear portion 22 that connects the rotor shaft 15 and the countershaft 20 and below the countershaft 20. This configuration allows the oil pump 50 to be positioned using the first space 91, thereby saving space within the rear transaxle 1. Therefore, with the rear transaxle 1 of this embodiment, the electric motor 2 and the differential device 4 are coaxially positioned, and the oil pump 50 that pressure-feeds cooling oil OL to the electric motor 2 is provided, thereby enabling the vehicle drive system to be more compact. Note that as long as the oil pump 50 can be positioned in the first space 91, the countershaft 20 may be aligned vertically with the output shaft 14 and the rotor shaft 15 or may be positioned below them.

[0041] Additionally, when viewed from the front-to-rear direction of the vehicle, oil pump 50 is positioned so that it partially overlaps with final driven gear portion 25, which connects countershaft 20 and differential case 24 of differential device 4. This configuration allows oil pump 50 to be positioned further inward in the vehicle width direction, thereby enabling further miniaturization of rear transaxle 1.

[0042] The casing 11 also has a second partition wall 38 (partition wall) that separates a gear chamber 71 (first space) in which a final driven gear unit 25 that connects the countershaft 20 and the differential case 24 of the differential device 4 is disposed, from a motor chamber 72 (another space). The oil pump 50 is disposed in the gear chamber 71 and draws cooling oil OL stored in the lower part of the motor chamber 72 through a communication passage 381 formed in the second partition wall 38. With this configuration, as described above, the cooling oil OL in the motor chamber 72, which is difficult to agitate, can be drawn in, thereby preventing the oil pump 50 from drawing in cooling oil OL containing air.

[0043] The rear transaxle 1 also includes a first discharge passage 101 connected to the discharge port of the oil pump 50 and extending to the second partition wall 38, a second discharge passage 102 connected to the first discharge passage 101 and extending along the second partition wall 38 on the opposite side of the electric motor 2 in the longitudinal direction of the vehicle, a third discharge passage 103 connected to the second discharge passage 102 and extending outward in the vehicle width direction along the wall portion 11c of the casing 11 on the opposite side of the electric motor 2 in the longitudinal direction of the vehicle, and a fourth discharge passage 104 connected to the third discharge passage 103 and extending along the outer surface (flat surface 34a) of the casing 11 toward the electric motor 2 in the longitudinal direction of the vehicle.

[0044] With this configuration, compared to when each discharge passage extending from the oil pump 50 is extended toward the electric motor 2 in the fore-and-aft direction of the vehicle through the gears such as the final drive gear section 23 and the final driven gear section 25 arranged in the gear chamber 71 and between the differential device 4, the structure of each discharge passage can be simplified while easily avoiding interference with these components, and space within the gear chamber 71 can be saved.

[0045] The rear transaxle 1 also includes an oil cooler 60 that is located outside the final driven gear unit 25, which connects the countershaft 20 and the differential case 24 of the differential device 4, in the vehicle width direction and above the right output shaft 12, and is connected to the fourth discharge passage 104 to cool the cooling oil OL. With this configuration, as described above, it is possible to connect the oil cooler 60, which is located in the second space 92, and the oil pump 50, which is located in the first space 91, while simplifying the structure of each discharge passage and saving space within the gear chamber 71.

[0046] The present invention is not limited to the above embodiment, and can be modified within the scope of the invention. For example, although the present invention is applied to a rear transaxle in this embodiment, it can also be applied to a front transaxle.

[0047] REFERENCE SIGNS LIST 1 Rear transaxle (vehicle drive device) 2 Electric motor 2a Outer periphery 3 Reducer 4 Differential device 7 Right drive shaft (drive shaft) 8 Left drive shaft (drive shaft) 10 Inverter 11 Casing 12 Right output shaft (first output shaft) 13 Left output shaft (second output shaft) 14 Output shaft 15 Rotor shaft (motor output shaft) 20 Countershaft (intermediate shaft) 21 Motor drive gear section 22 Counter driven gear section 23 Final drive gear section 24 Differential case (power input section) 25 Final driven gear section 31 First casing 32 Second casing 33 Third casing 34 Fourth casing 34a Flat surface (outer surface) 37 First partition wall 38 Second partition wall (partition wall) 41 First bearing (first bearing) 42 Second bearing (second bearing) 43 Third bearing 44 Fourth bearing (third bearing) 45 Fifth bearing (fourth bearing) 46 Sixth bearing 47 Seventh bearing (fifth bearing) 50 Oil pump (pump) 60 Oil cooler (cooling device) 71 Gear chamber (first space) 72 Motor chamber (another space) 91 First space 92 Second space 101 First discharge passage 102 Second discharge passage 103 Third discharge passage 104 Fourth discharge passage 110 Supply passage 111 First supply passage 111a First supply pipe 111b, 112b Supply hole 112 Second supply passage 112a Second supply pipe 113 Third supply passage 114 Fourth supply passage 115 Fifth supply passage OL Cooling oil (cooling medium)

Claims

1. An electric motor; an output shaft including a first output shaft and a second output shaft, each connected to a drive shaft that drives the wheels of a vehicle and arranged coaxially; a differential gear interposed between the first output shaft and the second output shaft; a speed reducer that reduces the output of the electric motor and inputs it to the differential gear; a pump that pressurizes a cooling medium to be supplied to the electric motor; and a casing that accommodates the electric motor, the differential gear, the speed reducer, and the pump, wherein the electric motor is arranged side by side along the axial direction of the differential gear and the output shaft, the motor output shaft of the electric motor is formed hollow, the first output shaft extends from the differential gear to the opposite side to the electric motor, and the second output shaft extends from the differential gear to the electric motor side and is rotatably inserted in the internal space of the motor output shaft, the speed reducer is arranged parallel to and spaced apart from the output shaft and the motor output shaft in the fore-and-aft direction of the vehicle, and includes an intermediate shaft connected to the motor output shaft and a power input portion of the differential gear via a plurality of gears, The vehicle drive device, wherein the pump is disposed outward in a vehicle width direction from the gear that connects the motor output shaft and the intermediate shaft and below the intermediate shaft.

2. A vehicle drive system as described in claim 1, wherein the pump is positioned so as to partially overlap the gear that connects the intermediate shaft and the power input portion of the differential device when viewed from the front-to-rear direction of the vehicle.

3. The vehicle drive device according to claim 1, wherein the casing has a partition wall separating a first space in which the gear that connects the intermediate shaft and the power input portion of the differential gear is arranged from another space, and the pump is arranged within the first space and draws in the cooling medium stored in the lower part of the other space through a communication passage formed in the partition wall.

4. A vehicle drive device as described in claim 3, further comprising: a first discharge passage connected to the discharge port of the pump and extending to the partition wall; a second discharge passage connected to the first discharge passage and extending along the partition wall on the opposite side of the electric motor in the vehicle longitudinal direction; a third discharge passage connected to the second discharge passage and extending outward in the vehicle width direction along a wall portion of the casing on the opposite side of the electric motor in the vehicle longitudinal direction; and a fourth discharge passage connected to the third discharge passage and extending along the outer surface of the casing on the outer side in the vehicle width direction.

5. A vehicle drive system as described in claim 4, further comprising a cooling device that is positioned outside the gear that connects the intermediate shaft and the power input portion of the differential device in the vehicle width direction and that cools the cooling medium supplied from the fourth discharge path.

Images