Electric vehicles

Abstract

To provide an electric vehicle which can prevent or suppress deterioration in workability in assembling a drive shaft to a differential device.SOLUTION: A case, a differential device, and drive shafts are constituted so that a first distance between a position of a maximum outer diameter portion of a flange part of the case and a position of a tip part of a clamp of one drive shaft is longer than a second distance between a position of a tip portion of a bore part of a differential case and a position of a tip portion of a bore fitting part of the one drive shaft. This can start fitting of the bore fitting part to the bore part, before the clamp reaches the maximum outer diameter portion of the flange part, in a course of assembling the one drive shaft to the differential device, This can prevent or suppress deterioration in workability in assembling the drive shaft to the differential device.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an electric vehicle provided with a case for housing an electric motor and a power transmission device.

Background Art

[0002] An electric vehicle including an electric motor, a power transmission device that transmits power from the electric motor to left and right drive wheels in the forward and backward directions, and a case that houses the electric motor and a part of the power transmission device is well known. The power transmission device includes a differential device that distributes the power to the drive wheels, and a pair of drive shafts that transmit the power from the differential device to the drive wheels. For example, the vehicle described in Patent Document 1 is such a vehicle. Patent Document 1 discloses a vehicle in which a transaxle that houses an electric motor and a power transmission device in a case and a power converter that controls the electric motor are arranged on an upper surface in the vertical direction of the transaxle in a front compartment.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, the case housing the electric motor and power transmission device may be configured to include a case body housing the differential device, etc., and a cover connected to the case body so as to close the opening of the case body, forming a motor chamber for housing the electric motor with the case body. On the other hand, considering that the drive unit including the electric motor and power transmission device will be mounted in a vehicle, for example, in the front compartment, miniaturization is desirable. When miniaturizing the drive unit, one can consider bringing the electric motor and differential device closer together to shorten the vertical, or height, length of the drive unit. However, this narrows the clearance (gap) in the direction perpendicular to the drive shaft between the largest outer diameter portion of the flange portion where the case body and cover are joined, which protrudes the most towards the drive shaft, and the largest outer diameter portion of the drive shaft. As a result, there is a risk that the workability when assembling the drive shaft to the differential device will deteriorate.

[0005] The present invention was made against the above circumstances, and its objective is to provide an electric vehicle that can prevent or suppress deterioration in workability when assembling the drive shaft to the differential device. [Means for solving the problem]

[0006] The gist of the first invention is an electric vehicle comprising: (a) an electric motor; a power transmission device for transmitting power from the electric motor to left and right drive wheels in the forward and reverse directions; and a case for housing the electric motor and a part of the power transmission device, wherein the power transmission device comprises a differential device for distributing the power to the drive wheels and a pair of drive shafts for transmitting the power from the differential device to the drive wheels, and (b) the case comprises a case body for housing the differential device, having a through hole formed for passing one of the drive shafts connected to one of the drive wheels, and a cover connected to the case body so as to close the opening of the case body, forming a motor chamber for housing the electric motor with the case body, A housing is provided, in which the open portion on the case body side is connected to the open portion on the case body side,(c) The drive shaft comprises a spline fitting portion formed at the end on the differential side which is fitted non-rotatably relative to the inner circumferential surface of the differential side gear of the differential device, a bore fitting portion formed adjacent to the spline fitting portion on the one drive wheel side which is fitted rotatably relative to the bore portion of the differential case of the differential device, a joint portion formed adjacent to the bore fitting portion on the one drive wheel side which constitutes a constant velocity joint, and a boot attached by a clamp to the outer circumference of the end of the joint portion on the one drive wheel side, (d) the position of the maximum outer diameter portion of the flange portion where the case body and the cover are joined which protrude the most toward the one drive shaft side, When one of the drive shafts is assembled to the differential device, the clearance between it and the flange portion is made as narrow as possible. The case, the differential device, and the drive shaft are configured such that, when the distance between the position of the tip of the clamp on the differential device side and the drive shaft in the direction of the rotation axis is set as the first distance, and the distance between the position of the tip of the bore on the side of one of the drive wheels and the position of the tip of the bore fitting on the differential device side and the drive shaft in the direction of the rotation axis is set as the second distance, the first distance is longer than the second distance when the drive shaft is not yet assembled to the differential device. [Effects of the Invention]

[0007] According to the first invention, the case, differential device, and drive shaft are configured such that, in the state before assembly of one drive shaft to the differential device begins, the distance between the position of the maximum outer diameter portion of the flange portion of the case and the position of the tip of the clamp of one drive shaft (first distance) is longer than the distance between the position of the tip of the bore portion of the differential case and the position of the tip of the bore fitting portion of one drive shaft (second distance). As a result, during the assembly process of one drive shaft to the differential device, the fitting of the bore fitting portion to the bore portion begins before the clamp reaches the maximum outer diameter portion of the flange portion. Therefore, deterioration of workability when assembling the drive shaft to the differential device can be prevented or suppressed. [Brief explanation of the drawing]

[0008] [Figure 1] This figure illustrates an example of a schematic configuration of an electric vehicle to which the present invention is applied. [Figure 2] This diagram illustrates an example of an electrical configuration related to the control of an electric motor. [Figure 3] This diagram illustrates an example of the general configuration of an integrated electromechanical unit. [Figure 4] This diagram illustrates an example of an electric vehicle equipped with an engine and a mechatronic integrated unit. [Figure 5] This figure shows an example of the state before assembly begins when installing the left drive shaft into the differential gear. [Figure 6] This diagram illustrates one example of the process of assembling the left drive shaft to the differential gear. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Examples]

[0010] Figure 1 is a diagram illustrating an example of the schematic configuration of an electric vehicle 10 to which the present invention is applied. In Figure 1, the electric vehicle 10 is a hybrid vehicle equipped with an engine 12 that functions as a power source and a second electric motor MG2 that functions as a power source. The electric vehicle 10 also includes drive wheels 14, a power transmission device 16, and a first electric motor MG1.

[0011] The engine 12 is a known internal combustion engine. The drive wheels 14 are the left and right wheels of the electric vehicle 10 in the forward and backward directions. The power transmission device 16 is provided in the power transmission path between the engine 12 and the drive wheels 14, and in the power transmission path between the second electric motor MG2 and the drive wheels 14.

[0012] The first electric motor MG1 and the second electric motor MG2 are known rotating electric machines that each have the function of an engine that generates mechanical power from electric power and a generator that generates electric power from mechanical power, and are so-called motor generators. The first electric motor MG1 and the second electric motor MG2 are housed in a non-rotatable case 18, which is a non-rotating member attached to the vehicle body.

[0013] The power transmission device 16 includes a connecting member 20, an input shaft 22, a transmission unit 24, a compound gear 26, a driven gear 28, a driven shaft 30, a final gear 32, a differential gear 34, a reduction gear 36, etc., within a case 18. The differential gear 34 is a known differential device having a differential ring gear 34a, a differential case 34b, a differential side gear 34c, a differential pinion 34d, and a pinion shaft 34e.

[0014] The connecting member 20 is a member connected to the crankshaft 12a of the engine 12, and includes, for example, a flywheel 20a connected to the crankshaft 12a, and a damper 20b connected to the flywheel 20a. The input shaft 22 functions as the input rotating member of the transmission unit 24. The input shaft 22 is connected to the damper 20b and is connected to the crankshaft 12a via the connecting member 20, etc. The transmission unit 24 is connected to the input shaft 22. The compound gear 26 is the output rotating body of the transmission unit 24. The compound gear 26 has a drive gear 26a formed on a part of its outer circumferential surface. The drive gear 26a is the output rotating member of the transmission unit 24. The driven gear 28 meshes with the drive gear 26a. The driven shaft 30 fixes the driven gear 28 and the final gear 32 so that they cannot rotate relative to each other. The final gear 32 has a smaller diameter than the driven gear 28 and meshes with the differential ring gear 34a. The reduction gear 36 has a smaller diameter than the driven gear 28 and meshes with the driven gear 28. The rotor shaft of the second electric motor MG2 is connected to the reduction gear 36, and the second electric motor MG2 is connected to the reduction gear 36 in a power transmission manner. The power transmission device 16 also includes a pair of drive shafts 38 connected to the differential gear 34, etc.

[0015] The power transmission device 16 configured in this way is suitably used in FF (front-engine, front-drive) or RR (rear-engine, rear-drive) vehicles. The power transmission device 16 transmits power output from the engine 12 to the driven gear 28 via the transmission unit 24. The power transmission device 16 also transmits power output from the second electric motor MG2 to the driven gear 28 via the reduction gear 36. The power transmission device 16 then transmits the power transmitted to the driven gear 28 to the drive wheels 14 sequentially via the driven shaft 30, final gear 32, differential gear 34, drive shaft 38, etc. The driven gear 28, driven shaft 30, and final gear 32 are transmission mechanisms that transmit power from the second electric motor MG2 to the differential gear 34, and transmission mechanisms that transmit power from the drive gear 26a to the differential gear 34. The differential gear 34 distributes power from the engine 12 and the second electric motor MG2 to the drive wheels 14. The drive shaft 38 transmits power from the differential gear 34 to the drive wheels 14.

[0016] The transmission unit 24 comprises a first electric motor MG1 and a differential mechanism 40. The differential mechanism 40 is a known single-pinion type planetary gear system comprising a sun gear S, a carrier CA, and a ring gear R. The sun gear S is connected to the rotor shaft of the first electric motor MG1, and the first electric motor MG1 is connected to it in a power-transmitting manner. The carrier CA is connected to the input shaft 22, and the engine 12 is connected to it in a power-transmitting manner via the input shaft 22, etc. The ring gear R is formed on a part of the inner circumferential surface of the composite gear 26 and is integrally connected to the drive gear 26a.

[0017] The differential mechanism 40 functions as a differential mechanism that causes a differential action and to which the engine 12 is connected so as to be able to transmit power. The first electric motor MG1 is a differential electric motor connected to the differential mechanism 40 so as to be able to transmit power. The differential mechanism 40 is a power split mechanism that mechanically splits the power of the engine 12 input to the carrier CA between the first electric motor MG1 and the drive gear 26a. The transmission unit 24 is a known electric transmission mechanism in which the differential state of the differential mechanism 40 is controlled by controlling the operating state of the first electric motor MG1.

[0018] The power transmission device 16 has a first axis CL1, a second axis CL2, a third axis CL3, and a fourth axis CL4. These four axes CL1, CL2, CL3, and CL4 are parallel to each other. The first axis CL1 is the axis of the input shaft 22 and the rotor shaft of the first electric motor MG1. That is, the first axis CL1 is the rotation axis of the first electric motor MG1. The transmission unit 24 and the first electric motor MG1 are arranged around the first axis CL1. The second axis CL2 is the axis of the driven shaft 30. The driven gear 28 and the final gear 32 are arranged around the second axis CL2. That is, the second axis CL2 is the rotation axis of the driven gear 28, the driven shaft 30, and the final gear 32. The third axis CL3 is the axis of the rotor shaft of the second electric motor MG2. That is, the third axis CL3 is the rotation axis of the second electric motor MG2. The second electric motor MG2 and the reduction gear 36 are arranged around the third axis CL3. The fourth axis CL4 is the axis of the drive shaft 38 and is the axis of the differential gear 34. That is, the fourth axis CL4 is the rotation axis of the drive shaft 38 and the differential gear 34. The differential gear 34 is arranged around the fourth axis CL4.

[0019] Case 18 includes a housing 18a, a case body 18b, and a cover 18c. The housing 18a is connected to an engine block 12b of the engine 12 at an open portion on the engine 12 side. The housing 18a and the case body 18b are integrally connected by a fastener such as a bolt so that an open portion on the opposite side of the housing 18a from the engine 12 and an open portion on the engine 12 side of the case body 18b are aligned. The case body 18b and the cover 18c are integrally connected by a fastener so that the cover 18c closes an open portion on the opposite side of the case body 18b from the engine 12. The case body 18b is a case including a partition wall (not shown) that partitions a gear chamber Rg that houses a transmission unit 24, a drive gear 28, a differential gear 34, etc., and a motor chamber Rm that houses a first electric motor MG1 and a second electric motor MG2. The case body 18b forms the gear chamber Rg with the housing 18a. The case body 18b forms the motor chamber Rm with the cover 18c. The case body 18b houses the differential gear 34 and the like. The case body 18b has a through hole 18b1 through which a left drive shaft 38a of a pair of drive shafts 38 passes. The left drive shaft 38a is one of the drive shafts connected to the left drive wheel 14a. The left drive wheel 14a is one of the drive wheels 14. The cover 18c is a case cover connected to the case body 18b so as to close an opening 18b2 on the opposite side of the case body 18b from the engine 12. The cover 18c forms the motor chamber Rm with the case body 18b. Thus, the case 18 houses the first electric motor MG1, the second electric motor MG2, and a part of the power transmission device 16 excluding the drive shaft 38 and the like.

[0020] FIG. 2 is a diagram for explaining an example of an electrical configuration related to the control of the first electric motor MG1 and the second electric motor MG2. In FIG. 2, the electric vehicle 10 further includes a high-voltage battery 50, an accessory battery 52, a power control unit 54, and the like.

[0021] The high-voltage battery 50 is a rechargeable DC power source, such as a nickel-metal hydride secondary battery or a lithium-ion battery. The high-voltage battery 50 is connected to the power control unit 54. The stored power from the high-voltage battery 50 is supplied to, for example, the second motor MG2 via the power control unit 54. In addition, the high-voltage battery 50 is supplied with power from the power generation control of the first motor MG1 and power from the regenerative control of the second motor MG2 via the power control unit 54. The high-voltage battery 50 is a battery for driving the vehicle.

[0022] The power control unit 54 includes a DC-DC converter 56, an electric motor control device 58, a boost converter 60, and an inverter 62. The power control unit 54 is a power control device that controls the power exchanged between the high-voltage battery 50 and the first electric motor MG1 and the second electric motor MG2, respectively.

[0023] The DC-DC converter 56 is connected to the high-voltage battery 50. The DC-DC converter 56 functions as a charging device that steps down the voltage of the high-voltage battery 50 to a voltage equivalent to that of the auxiliary battery 52 and charges the auxiliary battery 52. ​​The auxiliary battery 52 supplies power to operate auxiliary equipment, an electric motor control device 58, etc., provided in the electric vehicle 10.

[0024] The boost converter 60 includes reactors and switching elements (not shown). The boost converter 60 is a buck-boost circuit that has the function of boosting the voltage of the high-voltage battery 50 and supplying it to the inverter 62, and the function of stepping down the voltage converted to DC by the inverter 62 and supplying it to the high-voltage battery 50.

[0025] The inverter 62 includes an MG1 power module 64, an MG2 power module 66, and the like. The MG1 power module 64 and the MG2 power module 66 each include switching elements (not shown). The inverter 62 converts the DC current from the boost converter 60 into AC current to drive the first motor MG1 and the second motor MG2. The inverter 62 converts the AC current generated by the first motor MG1 using the power of the engine 12, and the AC current generated by the second motor MG2 using regenerative braking, into DC current. The inverter 62 supplies the AC current generated by the first motor MG1 as power to drive the second motor MG2, according to the driving conditions.

[0026] The motor control device 58 controls the boost converter 60 and the inverter 62. For example, the motor control device 58 converts the DC current from the high-voltage battery 50 into AC current used by the first motor MG1 and the second motor MG2, respectively. The motor control device 58 drives the first motor MG1 to ensure the amount of power generated to supply power to the second motor MG2 and to charge the high-voltage battery 50. The motor control device 58 drives the second motor MG2 based on the output requirement value corresponding to the driver's requested torque. The motor control device 58 makes the second motor MG2 function as a generator according to the amount of regenerative braking required.

[0027] Figure 3 is a diagram illustrating an example of the schematic configuration of the hybrid drive unit 90. Figure 4 is a diagram illustrating an example of the electric vehicle 10 with the engine 12 and the hybrid drive unit 90 mounted on it. Figure 4 is a perspective view of the electric vehicle 10 from the front, left side. In Figures 3 and 4, the transaxle 92 and the power control unit 54 are housed in the same case 18 as the hybrid drive unit 90. The hybrid drive unit 90 is a unit in which the transaxle 92 and the power control unit 54 are integrated, i.e., a mechatronic integrated unit. The hybrid drive unit 90 is positioned adjacent to the engine 12. Power from the engine 12 is input to the hybrid drive unit 90. Note that the vertical direction, forward / reverse direction, and vehicle width direction in the figures indicate the direction when mounted on the electric vehicle 10. The vehicle width direction is the axial direction of the first axis CL1, the second axis CL2, the third axis CL3, and the fourth axis CL4.

[0028] Case 18 further comprises a protective plate 18d in addition to the housing 18a, case body 18b, and cover 18c described above. The case body 18b has a bottom wall and side walls that extend vertically upward from the outer edge of the bottom wall on the front and rear sides in the forward and backward directions, respectively, and has an opening at the top in the vertical direction. The protective plate 18d is a plate-shaped member that closes the opening at the top in the vertical direction of the case body 18b. The case body 18b has a partition wall (not shown) inside, which divides the interior into two spaces: a space A at the bottom in the vertical direction and a space B at the top in the vertical direction.

[0029] The transaxle 92 is a drive unit that includes a part of the power transmission unit 16 (26a, 28, 32, 34a, 36, etc.), the first motor MG1, and the second motor MG2. When mounted on the electric vehicle 10, the transaxle 92 is housed in the space A in the lower vertical direction of the case body 18b and in the housing 18a.

[0030] The power control unit 54 is housed in the vertical upper space B of the case body 18b when mounted on the electric vehicle 10. The vertical upper space B includes the surplus space B1 created by the arrangement of the first electric motor MG1 and the second electric motor MG2, and the vertical upper space B2 of the second electric motor MG2. The length of the surplus space B1 in the forward and backward direction is shorter than that of space B2.

[0031] In the lower vertical portion of the surplus space B1, relatively short components of the power control unit 54 are housed, for example. In the upper vertical portion of the surplus space B1, components of the power control unit 54 are housed, for example, considering ease of replacement.

[0032] Referring to Figure 3, in the mounted state on the electric vehicle 10, the transaxle 92 is arranged such that the first axle CL1, second axle CL2, third axle CL3, and fourth axle CL4 are each parallel to the horizontal direction perpendicular to the forward and backward direction of the electric vehicle 10. Furthermore, in the mounted state on the electric vehicle 10, the positions of the first axle CL1, second axle CL2, third axle CL3, and fourth axle CL4 are arranged in the order of second motor MG2, driven shaft 30, first motor MG1, and differential gear 34 from top to bottom in the vertical direction, and in the order of first motor MG1, driven shaft 30, differential gear 34, and second motor MG2 from front to rear in the forward and backward direction. As a result, the inter-axis distances of the first axis CL1, second axis CL2, third axis CL3, and fourth axis CL4 are appropriately secured, while the vertical size of the transaxle 92 is reduced. Therefore, the arrangement of the first motor MG1 and the second motor MG2 creates surplus space B1, and space B2 is created vertically above the second motor MG2. The power control unit 54 is mounted in this space B (B1 + B2).

[0033] In its mounted state on the electric vehicle 10, the power control unit 54 is positioned vertically above the transaxle 92. In addition, the lower vertical portion of the power control unit 54 is positioned so that it overlaps with the upper vertical portion of the transaxle 92, particularly the second electric motor MG2, when viewed horizontally, particularly in the forward and backward directions. Alternatively, in its mounted state on the electric vehicle 10, the lower vertical portion of the power control unit 54 is positioned vertically above the first electric motor MG1.

[0034] The reduced vertical size of the transaxle 92 creates space for the power control unit 54, and space is created vertically above the hybrid drive unit 90.

[0035] Incidentally, in the hybrid drive unit 90, an integrated electromechanical structure is adopted, which reduces the vertical size of the transaxle 92, and therefore the second electric motor MG2 is positioned closer to the differential gear 34. As a result, the clearance between the flange portion 18bc, where the case body 18b and cover 18c, which form the motor chamber Rm, are joined, and the left drive shaft 38a is narrowed (see Figure 5 below). Therefore, there is a risk that the workability when assembling the left drive shaft 38a to the differential gear 34 will deteriorate. For example, when assembling the left drive shaft 38a, there is a risk that the left drive shaft 38a will hit the case body 18b, and the oil seal 70 (see Figure 5 below) will be damaged by the left drive shaft 38a.

[0036] Figure 5 shows an example of the state before assembly begins when assembling the left drive shaft 38a to the differential gear 34. In Figure 5, the case body 18b is provided with an oil seal 70 as a sealing member at the end of the through hole 18b1 on the left drive wheel 14a side. The differential case 34b has a bore portion 34b1 formed on the left drive wheel 14a side, which is a through hole into which the left drive shaft 38a is fitted. The differential side gear 34c has spline teeth formed on the inner circumferential surface 34c1 of the through hole into which the left drive shaft 38a is fitted.

[0037] The left drive shaft 38a includes a spline fitting portion 72, a bore fitting portion 74, a joint portion 76, a clamp 78, an inner boot 80, and an intermediate shaft 82. The spline fitting portion 72, the bore fitting portion 74, and the joint portion 76 constitute an inner joint. The left drive shaft 38a is equipped with an outer boot and an outer joint (not shown) on the left drive wheel 14a side relative to the intermediate shaft 82.

[0038] The spline fitting portion 72 is formed at the end on the differential gear 34 side. The spline fitting portion 72 has spline teeth formed on its outer circumference and fits to the inner circumference 34c1 of the differential side gear 34c in a relative non-rotatable manner. The bore fitting portion 74 is formed adjacent to the spline fitting portion 72 on the left drive wheel 14a side. The bore fitting portion 74 fits to the bore portion 34b1 of the differential case 34b in a relative rotatable manner. The inner diameter of the oil seal 70 is larger than the outer diameter of the bore fitting portion 74. The joint portion 76 is formed adjacent to the bore fitting portion 74 on the left drive wheel 14a side. The joint portion 76 constitutes a constant velocity joint. The outer diameter of the joint portion 76 is larger than the inner diameter of the oil seal 70. The clamp 78 is a fastening member. The inner boot 80 is a boot attached by a clamp 78 to the outer circumference of the left drive wheel 14a side end of the joint 76. The intermediate shaft 82 has its end on the differential gear 34 side connected to the constant velocity joint of the joint 76.

[0039] In the electric vehicle 10, the case 18, differential gear 34, and drive shaft 38 are configured such that the clamp 78, which has the narrowest clearance with the flange portion 18bc when assembling the left drive shaft 38a, begins to engage with the bore fitting portion 74 and the bore portion 34b1 of the differential case 34b before the clamp 78 passes the maximum outer diameter portion 18bc1 that protrudes the most towards the left drive shaft 38a side of the flange portion 18bc. The engagement of the bore fitting portion 74 and the bore portion 34b1 eliminates play during assembly of the left drive shaft 38a, and even when the clearance between the clamp 78 and the maximum outer diameter portion 18bc1 is narrow, the left drive shaft 38a can be assembled in a way that makes it difficult for it to interfere with the oil seal 70.

[0040] For example, in this embodiment, the distance in the direction of the fourth axis CL4 between the position C of the largest outer diameter portion 18bc1 of the flange portion 18bc and the position D of the tip of the clamp 78 on the differential gear 34 side is set as the first distance L1. Also, the distance in the direction of the fourth axis CL4 between the position E of the tip of the bore portion 34b1 on the left drive wheel 14a side and the position F of the tip of the bore fitting portion 74 on the differential gear 34 side is set as the second distance L2. The electric vehicle 10 is configured such that, before assembly of the left drive shaft 38a to the differential gear 34 begins, the first distance L1 is longer than the second distance L2.

[0041] From a different perspective, the electric vehicle 10 is configured such that the third distance L3, which is the distance between position D and position F in the direction of the fourth axis CL4, is longer than the fourth distance L4, which is the distance between position C and position E in the direction of the fourth axis CL4.

[0042] Figure 6 illustrates an example of the process of assembling the left drive shaft 38a to the differential gear 34. Note that the state in Figure 5 shows the state in the assembly process of the left drive shaft 38a where the tip of the left drive shaft 38a on the differential gear 34 side has reached the oil seal 70.

[0043] The state shown in Figure 6(a) represents the state after the spline fitting portion 72 has been inserted into the bore portion 34b1 and passed through the oil seal 70 during the assembly process of the left drive shaft 38a. In this state, the clamp 78 has not yet reached the maximum outer diameter portion 18bc1, and there is ample clearance in the first distance L1.

[0044] The state shown in Figure 6(b) represents the state in which the fitting of the bore fitting portion 74 and the bore portion 34b1 has begun during the assembly process of the left drive shaft 38a. Even in this state, the clamp 78 has not reached the maximum outer diameter portion 18bc1, and there is still clearance in the first distance L1.

[0045] The state shown in Figure 6(c) represents the state in which the clamp 78 has reached the maximum outer diameter portion 18bc1 during the assembly process of the left drive shaft 38a. In other words, it represents the state in which the first distance L1 has become zero. In this state, the bore fitting portion 74 is fitted into the bore portion 34b1 to the extent that there is no play during the assembly of the left drive shaft 38a.

[0046] As described above, according to this embodiment, the electric vehicle 10 is configured such that, before assembly of the left drive shaft 38a to the differential gear 34 begins, the first distance L1 is longer than the second distance L2. Conversely, the electric vehicle 10 is configured such that, before assembly of the left drive shaft 38a to the differential gear 34 begins, the third distance L3 is longer than the fourth distance L4. As a result, during the assembly process of the left drive shaft 38a to the differential gear 34, the fitting of the bore fitting portion 74 to the bore portion 34b1 begins before the clamp 78 reaches the maximum outer diameter portion 18bc1 of the flange portion 18bc. Therefore, deterioration of workability when assembling the drive shaft 38 to the differential gear 34 can be prevented or suppressed.

[0047] Furthermore, according to this embodiment, the case body 18b is provided with an oil seal 70 at the end of the through hole 18b1 on the left drive wheel 14a side. As described above, the case 18, differential gear 34, and drive shaft 38 are configured in such a way that the left drive shaft 38a is less likely to interfere with the oil seal 70 during assembly.

[0048] Furthermore, according to this embodiment, the case 18 houses the transaxle 92 and the power control unit 54 as an integrated electromechanical unit. In order to reduce the vertical size of the transaxle 92, the second electric motor MG2 is positioned closer to the differential gear 34. However, as described above, the case 18, differential gear 34, and drive shaft 38 are configured in such a way that deterioration in workability when assembling the drive shaft 38 to the differential gear 34 can be prevented or suppressed.

[0049] Although embodiments of the present invention have been described in detail above with reference to the drawings, the present invention is also applicable to other embodiments.

[0050] For example, in the above embodiment, when the transaxle 92 is mounted on the electric vehicle 10, the positions of the first axle CL1, second axle CL2, third axle CL3, and fourth axle CL4 may be arranged in the order of first motor MG1, driven shaft 30, differential gear 34, and second motor MG2 from rear to front in the forward and backward direction. Also, one of the drive wheels may be the right drive wheel, and one of the drive shafts may be the right drive shaft. Furthermore, the transaxle 92 and the power control unit 54 may each be housed in separate cases. Also, the power control unit 54 does not necessarily have to be located vertically above the transaxle 92.

[0051] Furthermore, in the above-described embodiment, the electric vehicle may be an electric vehicle equipped with a drive motor. In this case, for example, at the arrangement position of each component of the transaxle 92 shown in Figure 3, the first motor MG1 is removed, and the second motor MG2 functions as the electric motor of the electric vehicle. Alternatively, the electric vehicle may be a series hybrid vehicle equipped with an engine, a drive motor that functions as a power source, and a power supply motor that is connected to the engine in a manner that can transmit power and generates electricity using the engine's power. In such a series hybrid vehicle, the power transmission path between the engine and the drive wheels may be interrupted or connected by the operation of a clutch. Alternatively, the electric vehicle may be a parallel hybrid vehicle equipped with an engine, a power transmission device that transmits power from the engine to the drive wheels, and an electric motor to which power is transmitted to the drive wheels via the power transmission device.

[0052] Furthermore, in the above-described embodiment, the electric vehicle 10 may be a so-called plug-in hybrid vehicle that can charge the high-voltage battery 50 with power from an external power source. In a plug-in hybrid vehicle, the miniaturization of the hybrid drive unit 90 greatly increases the flexibility of the placement of chargers and the like.

[0053] It should be noted that the above-described embodiment is merely one example, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art. [Explanation of symbols]

[0054] 10: Electric vehicle 14: Drive wheel 14a: Left drive wheel (one drive wheel) 16: Power transmission device 18: Case 18b: Case body 18b1: Through hole 18b2: Opening 18bc: Flange part 18bc1: Maximum outer diameter part 18c: Cover 28: Driven gear (transmission mechanism) 30: Driven shaft (transmission mechanism) 32: Final gear (transmission mechanism) 34: Differential gear (differential device) 34b: Differential case 34b1: Bore part 34c: Differential side gear 34c1: Inner surface 38: Drive shaft 38a: Left drive shaft (one drive shaft) 50: High-voltage battery (battery for driving) 54: Power control unit (power control device) 70: Oil seal (sealing member) 72: Spline fitting part 74: Bore fitting part 76: Joint part 78: Clamp 80: Inner boot (boot) 90: Hybrid drive unit (mechatronic integrated unit) 92: Transaxle (drive device) CL2: Second axis (rotation axis of the transmission mechanism) CL3: Third axis (rotation axis of the electric motor) CL4: Fourth axis (rotation axis of the drive shaft or differential device) L1: First distance L2: Second distance MG2: Second electric motor (electric motor) Rm: Motor room

Claims

1. An electric vehicle comprising: an electric motor; a power transmission device for transmitting power from the electric motor to left and right drive wheels in the forward and reverse directions; and a case for housing the electric motor and a part of the power transmission device, wherein the power transmission device comprises: a differential device for distributing the power to the drive wheels; and a pair of drive shafts for transmitting the power from the differential device to the drive wheels, The case comprises a case body for housing the differential device, having a through hole formed for passing one of the drive shafts connected to one of the drive wheels; a cover connected to the case body so as to close the opening of the case body, forming a motor chamber for housing the electric motor with the case body; and a housing to which the open portion on the case body side is connected to the open portion on the opposite side of the cover of the case body. The aforementioned drive shaft comprises: a spline fitting portion formed at the end on the differential device side that fits non-rotatably relative to the inner circumferential surface of the differential side gear of the differential device; a bore fitting portion formed adjacent to the spline fitting portion on the one drive wheel side that fits rotatably relative to the bore portion of the differential case of the differential device; a joint portion forming a constant velocity joint formed adjacent to the bore fitting portion on the one drive wheel side; and a boot attached by a clamp to the outer circumference of the end of the joint portion on the one drive wheel side. An electric vehicle characterized in that, when the distance in the rotational axis direction of the drive shaft is set as the first distance between the position of the largest outer diameter portion of the flange portion where the case body and the cover are joined and which protrudes the most toward the one drive shaft side, and the position of the tip of the clamp on the differential device side where the clearance with the flange portion is narrowest when the one drive shaft is assembled to the differential device, the distance in the rotational axis direction of the drive shaft is set as the second distance between the position of the tip of the bore portion toward the one drive wheel side and the position of the tip of the bore fitting portion toward the differential device side, the case, the differential device, and the drive shaft are configured such that the first distance is longer than the second distance in the state before assembly of the one drive shaft to the differential device begins.

2. The electric vehicle according to claim 1, characterized in that the case, the differential device, and the drive shaft are configured such that the distance in the rotational axis direction of the drive shaft between the position of the tip of the clamp and the position of the tip of the bore fitting portion is longer than the distance in the rotational axis direction of the drive shaft between the position of the maximum outer diameter portion of the flange portion and the position of the tip of the bore portion.

3. The case body is provided with a sealing member at the end of the through hole on the side of one of the drive wheels, The inner diameter of the sealing member is larger than the outer diameter of the bore fitting portion. The electric vehicle according to claim 1, characterized in that the outer diameter of the joint portion is larger than the inner diameter of the sealing member.

4. It comprises a drive battery and a power control device that controls the power exchanged between the battery and the electric motor, The electric vehicle according to any one of claims 1 to 3, characterized in that the case houses a drive unit including the electric motor and a part of the power transmission device, and the power control device as an integrated electromechanical unit.

5. The power transmission device includes a transmission mechanism that transmits power from the electric motor to the differential device. In the mounted state on the electric vehicle, the drive unit is arranged such that the rotation axis of the electric motor, the rotation axis of the transmission mechanism, and the rotation axis of the differential device are each parallel to the horizontal direction perpendicular to the forward and backward direction of the electric vehicle, and the positions of each rotation axis are such that, from top to bottom in the vertical direction, they are in the order of the electric motor, the transmission mechanism, and the differential device, and in the forward and backward direction, they are in the order of the transmission mechanism, the differential device, and the electric motor. The electric vehicle according to claim 4, characterized in that the power control device, when mounted on the electric vehicle, is positioned vertically above the drive unit, and the vertically lower portion of the power control device is positioned to overlap with the vertically upper portion of the electric motor when viewed in the forward and backward direction.

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