Power transmission device for vehicle

Abstract

The invention provides a power transmission device for a vehicle, which reduces loss at a bearing and suppresses weight increase. (a) A spline fitting portion (50) in which a rotor shaft (42) and a gear shaft (44) are spline-fitted, a socket joint portion (52) in which an inner peripheral surface (42i) of the rotor shaft (42) and an outer peripheral surface (44o) of the gear shaft (44) are in contact and fitted, and a damper portion (54) in which a friction damper (56) is disposed between the inner peripheral surface (42i) of the rotor shaft (42) and the outer peripheral surface (44o) of the gear shaft (44) are disposed in this order from the second motor (MG2) side in the direction of the axis (C). (b) A second bearing (82) is provided at a position overlapping the damper section (54) when viewed in the radial direction of the rotor shaft (42) and the gear shaft (44).

Description

Technical Field

[0001] The present invention relates to a power transmission device for a vehicle in which a rotor shaft of an electric motor and a gear shaft are connected to form a common axis. Background Art

[0002] There is known a power transmission device for a vehicle, in which the rotor shaft and the gear shaft of the electric motor are connected in a manner that forms a common axis, and a spline fitting portion and a vibration-damping portion are sequentially arranged from the motor side in the axial direction, the spline fitting portion spline-fits the inner circumference of the rotor shaft with the outer circumference of the gear shaft, and the vibration-damping portion is provided with an elastic member between the inner circumference of the rotor shaft and the outer circumference of the gear shaft. For example, the power transmission device for a vehicle described in Patent Document 1 is such a power transmission device for a vehicle. In the power transmission device for a vehicle described in Patent Document 1, four bearings are provided in a manner that is supported by a non-rotating member. Specifically, four bearings are provided at a total of four locations at both ends of the rotor shaft in the axial direction and at both ends of the gear shaft.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-135934

[0006] However, in the power transmission device of the vehicle described in Patent Document 1, in order to reduce the loss at the bearing, it is considered to reduce the number of bearings to three. For example, in the power transmission device of the vehicle described in Patent Document 1, in order to reduce the bearing on the motor side of the gear shaft and suppress the axis misalignment of the rotor shaft and the gear shaft, a socket joint is provided at a position closer to the gear shaft side than the vibration damping part in the axial direction. However, when the spline fitting part, the vibration damping part, and the socket joint are arranged in sequence from the motor side in the axial direction, the outer diameter of the socket joint in the gear shaft has to be increased by an amount corresponding to the provision of the elastic member compared to the vibration damping part. Along with this, the outer diameter of the socket joint in the rotor shaft, that is, the outer diameter of the part with the largest outer diameter in the rotor shaft, has to be increased. As a result, the weight of the power transmission device increases. Summary of the invention

[0007] Problems to be solved by the invention

[0008] The present invention has been made under the above circumstances, and an object of the present invention is to provide a power transmission device for a vehicle that reduces loss at a bearing and suppresses an increase in weight.

[0009] Means for solving problems

[0010] The gist of the present invention is a power transmission device for a vehicle, in which the rotor shaft and the gear shaft of the electric motor are connected in a manner to form a common axis, (a) a spline fitting portion in which the inner circumference of the rotor shaft and the outer circumference of the gear shaft are spline-fitted, a socket joint portion in which the inner circumference of the rotor shaft and the outer circumference of the gear shaft are in contact and fit, and a vibration-damping portion in which an elastic member is arranged between the inner circumference of the rotor shaft and the outer circumference of the gear shaft in sequence from the electric motor side in the direction of the axis, and (b) a bearing is provided at a position overlapping the vibration-damping portion when the rotor shaft and the gear shaft are viewed in radial directions.

[0011] Effects of the Invention

[0012] According to the power transmission device of the vehicle of the present invention, (a) a spline fitting portion in which the inner circumference of the rotor shaft and the outer circumference of the gear shaft are spline-fitted, a socket joint portion in which the inner circumference of the rotor shaft and the outer circumference of the gear shaft are in contact and fit, and a vibration-damping portion having an elastic member disposed between the inner circumference of the rotor shaft and the outer circumference of the gear shaft are sequentially arranged in the direction of the axis from the motor side, and (b) a bearing is provided at a position overlapping with the vibration-damping portion when the rotor shaft and the gear shaft are viewed in the radial direction. When the spline fitting portion, the socket joint portion, and the vibration-damping portion are sequentially arranged in the direction of the axis from the motor side in this manner, the outer diameter of the rotor shaft in the vibration-damping portion, that is, the outer diameter of the portion of the rotor shaft with the largest outer diameter, can be reduced compared to a case where this is not the case. As a result, the loss at the bearing is reduced, and the increase in the weight of the power transmission device is suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic structural diagram of a vehicle equipped with the power transmission device of the embodiment.

[0014] Figure 2 Yes Description Figure 1 A sectional view of the structure of the power transmission device shown.

[0015] Description of Reference Numerals

[0016] 10: Vehicles

[0017] 40: Power transmission device

[0018] 42: Rotor shaft

[0019] 42i: Inner Surface

[0020] 50: Spline fitting part

[0021] 52: Socket joint

[0022] 54: Vibration reduction unit

[0023] 44: Gear shaft

[0024] 44o: Outer surface

[0025] 56: Friction damper (elastic component)

[0026] 82: Second bearing (bearing)

[0027] C: Axis

[0028] MG2: Second motor (electric motor) DETAILED DESCRIPTION

[0029] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the embodiments, the drawings are appropriately simplified or deformed, and the dimensional ratios and shapes of the various parts are not necessarily accurately depicted.

[0030] [Example]

[0031] Figure 1 It is a schematic structural diagram of a vehicle 10 equipped with a power transmission device 40 according to the embodiment.

[0032] The first electric motor MG1 and the second electric motor MG2 are driving power sources, and are three-phase synchronous electric motors, so-called motor generators, for example. The first electric motor MG1 and the second electric motor MG2 are accommodated in a case 18 that is a non-rotating member attached to the vehicle body.

[0033] The transaxle 72 is accommodated in the housing 18. For example, the power output from the engine 12 is mechanically distributed to the first motor MG1 and the drive gear 22 by the power distribution mechanism 36. The first motor MG1 generates electricity by the power of the engine 12 distributed to the first motor MG1. The generated power Wmg1 in the first motor MG1 is charged to a battery (not shown), or all or part of the generated power Wmg1 is used for the rotational drive of the second motor MG2, or the power from the battery other than the generated power Wmg1 is used for the rotational drive of the second motor MG2. The power distribution mechanism 36 functions as an electric continuously variable transmission that controls the differential state of the power distribution mechanism 36 by controlling the operating state of the first motor MG1. The power of the engine 12 distributed to the drive gear 22 is transmitted to the driven gear 24, the driven shaft 26, the final drive gear 28, and the differential 30. The second motor MG2 is connected to the driven shaft 26 via the power transmission device 40, the reduction gear 32, and the driven gear 24 in a manner that can transmit power. The power transmission device 40 includes a rotor shaft 42 of the second electric motor MG2, a gear shaft 44 connected to the rotor shaft 42, a first bearing 80, a second bearing 82, and a third bearing 84. The rotor shaft 42 and the gear shaft 44 are connected to form a common axis C. The output of the transaxle 72 is transmitted to the pair of drive wheels 14 via the pair of axles 34 connected to the differential 30, etc.

[0034] The power control unit 38 (hereinafter referred to as "PCU38") is a power control device that controls the power exchanged between the aforementioned unillustrated battery and the first motor MG1 and the second motor MG2. The PCU38 includes an inverter. The inverter converts the DC current supplied from the battery into an AC current for driving the first motor MG1 and the second motor MG2, and converts the AC current generated by the first motor MG1 and the second motor MG2 into a DC current. The PCU38 is controlled by an unillustrated electronic control device according to the driving state of the vehicle 10, thereby controlling the output of each of the first motor MG1 and the second motor MG2.

[0035] The drive unit 70 is a unit in which the transaxle 72 and the PCU 38 are accommodated and integrated in the same case 18 , that is, a mechatronic drive unit.

[0036] Here, the meaning of “same housing” will be described. The housing 18 is made of, for example, an aluminum alloy casting, and includes a first housing portion 60 , a second housing portion 62 , a third housing portion 64 , and a fourth housing portion 66 .

[0037] The first housing portion 60 is a cylindrical member with a bottom. The second housing portion 62 is a cylindrical member with a bottom, and a partition wall 62d is provided inside the second housing portion 62. For example, the second housing portion 62 is integrally formed by casting with a bottom wall, a side wall extending upward from the outer peripheral edge of the bottom wall, and the partition wall 62d. The second housing portion 62 has an opening on its upper surface. A portion of the side wall of the second housing portion 62 that is lower than the partition wall 62d has openings on the engine 12 side and on the side opposite to the engine 12, respectively. The first housing portion 60 and the second housing portion 62 are connected by bolts 68a (refer to Figure 1 ) and other fasteners. The housing 18 is connected to the first housing portion 60 by the second housing portion 62, and has an upper space U and a lower space L separated in the up-down direction by a partition wall 62d. Here, the portion of the housing 18 that surrounds the upper space U is referred to as the upper housing portion 18U, and the portion of the housing 18 that surrounds the lower space L is referred to as the lower housing portion 18L. The lower housing portion 18L is a portion of the housing 18 that is arranged at a lower side than the upper housing portion 18U in the up-down direction. The lower side of the upper housing portion 18U and the upper side of the lower housing portion 18L form a common partition wall 62d. Therefore, when the upper housing portion 18U is separated from the lower housing portion 18L, the interior of at least one of the upper housing portion 18U and the lower housing portion 18L must be exposed to the outside. "The same housing" refers to a housing in which the interior of at least one of the upper housing portion 18U and the lower housing portion 18L is exposed to the outside when the upper housing portion 18U and the lower housing portion 18L are separated like this.

[0038] The third housing portion 64 is a plate-shaped member joined to the second housing portion 62 in such a manner as to close the opening of the side wall of the second housing portion 62 on the side opposite to the engine 12. The second housing portion 62 and the third housing portion 64 are connected by bolts 68b (see Figure 1 ) and other fasteners are integrally connected. The fourth housing portion 66 is a plate-shaped member joined to the second housing portion 62 in a manner that blocks the opening of the upper surface of the second housing portion 62. The second housing portion 62 and the fourth housing portion 66 are connected by bolts 68c (see Figure 1 ) and other fasteners and connected as a whole.

[0039] When mounted on the vehicle 10 , the transaxle 72 is accommodated in the lower case portion 18L. That is, the transaxle 72 is disposed in the lower space L. When mounted on the vehicle 10 , the PCU 38 is accommodated in the upper case portion 18U. That is, the PCU 38 is disposed in the upper space U.

[0040] Figure 2 Yes Description Figure 1 A cross-sectional view of the structure of the power transmission device 40 is shown. Figure 2It is a cross-sectional view in the direction of axis C.

[0041] The second electric motor MG2 is an inner rotor type electric motor. The second electric motor MG2 corresponds to the "electric motor" in the present invention. The rotor shaft 42 is cylindrical. The outer circumference of the rotor shaft 42 is connected to the inner circumference of the rotor MG2r of the second electric motor MG2 in a relatively non-rotatable manner.

[0042] The gear shaft 44 is cylindrical. The reduction gear 32 is provided on the outer periphery of the gear shaft 44. The reduction gear 32 and the driven gear 24 mesh with each other. The reduction gear 32 and the driven gear 24 are, for example, helical gears, which increase the meshing ratio and make the power transmission quiet and the torque variation small. When the reduction gear 32 and the driven gear 24 are helical gears, a thrust is generated on the gear shaft 44. The thrust is a thrust in the direction of the axis C (=thrust direction). The thrust is in opposite directions when the vehicle 10 is traveling forward and when it is traveling backward.

[0043] In the axis C direction, the spline fitting portion 50 , the socket joint portion 52 , and the vibration damping portion 54 are arranged in this order from the second electric motor MG2 side.

[0044] The spline fitting portion 50 is a portion where the inner circumferential surface 42i of the rotor shaft 42 is spline-fitted with the outer circumferential surface 44o of the gear shaft 44. In the spline fitting portion 50, the spline teeth 42s provided on the inner circumferential surface 42i of the rotor shaft 42 are spline-fitted with the spline teeth 44s provided on the outer circumferential surface 44o of the gear shaft 44. There is backlash between the spline teeth 42s and the spline teeth 44s in the rotation direction. Due to the relative rotational variation of the rotor shaft 42 and the gear shaft 44, the spline teeth 42s and the spline teeth 44s may repeatedly separate and collide with each other in the rotational direction to produce a chattering sound (tooth-smacking sound). For example, the aforementioned relative rotational variation occurs when the output torque of the second motor MG2 varies, when the output torque of the second motor MG2 is substantially zero and the rotor shaft 42 is rotated by the gear shaft 44 under no-load conditions. The spline fitting portion 50 transmits the force in the rotational direction between the rotor shaft 42 and the gear shaft 44.

[0045] The socket joint 52 is a portion where the inner circumferential surface 42i of the rotor shaft 42 and the outer circumferential surface 44o of the gear shaft 44 contact and fit. When the rotor shaft 42 and the gear shaft 44 are coupled, the socket joint 52 prevents the axes of the rotor shaft 42 and the gear shaft 44 from being misaligned.

[0046] The vibration damper 54 is a portion where a friction damper 56 is disposed between the inner circumferential surface 42i of the rotor shaft 42 and the outer circumferential surface 44o of the gear shaft 44. The friction damper 56 corresponds to the "elastic member" in the present invention. In the vibration damper 54, the inner diameter of the rotor shaft 42 is larger than the outer diameter of the gear shaft 44. The friction damper 56 is disposed in the annular space between the inner circumferential surface 42i of the rotor shaft 42 and the outer circumferential surface 44o of the gear shaft 44 in the vibration damper 54. The friction damper 56 is, for example, a well-known friction damper having an annular metal portion and an elastic body (e.g., rubber) adhered to the outer circumferential surface of the metal portion. The metal portion of the friction damper 56 is embedded in the outer circumferential surface 44o of the gear shaft 44, and the elastic body of the friction damper 56 is pressed between the metal portion and the inner circumferential surface 42i of the rotor shaft 42. The friction damper 56 suppresses the occurrence of the chattering sound in the rotational direction in the spline fitting portion 50 by applying a predetermined friction resistance in the rotational direction, but the effect of suppressing the misalignment of the axes of the rotor shaft 42 and the gear shaft 44 is small.

[0047] The power transmission device 40 is provided with three bearings (a first bearing 80, a second bearing 82, and a third bearing 84) in a manner supported by the housing 18 (specifically, the second housing portion 62) as a non-rotating member. These three bearings are bearings capable of supporting both radial loads and thrust loads of the rotor shaft 42 and the gear shaft 44, and are, for example, ball bearings. In the axis C direction, the first bearing 80 and the third bearing 84 are provided at one end and the other end of the power transmission device 40 to which the rotor shaft 42 and the gear shaft 44 are connected, respectively. In the axis C direction, the second bearing 82 is provided at a position between the first bearing 80 and the third bearing 84 and at a position overlapping with the damping portion 54 when viewed in the radial direction of the rotor shaft 42 and the gear shaft 44 (hereinafter referred to as "viewed in the radial direction"). The second bearing 82 corresponds to the "bearing" in the present invention. Preferably, at least a portion of the spline fitting portion 50 is provided at a position overlapping with the rotor MG2r when viewed in the radial direction. Furthermore, a portion of the damper portion 54 may be provided at a position overlapping with the rotor MG2r when viewed in the radial direction.

[0048] In the axis C direction, the first bearing 80 is provided on one side of the rotor shaft 42 (=the side opposite to the gear shaft 44), and the second bearing 82 is provided on the other side of the rotor shaft 42 (=the gear shaft 44 side). The rotor MG2r is located between the first bearing 80 and the second bearing 82. In the axis C direction, the second bearing 82 is provided on one side of the gear shaft 44 (=the rotor shaft 42 side), and the third bearing 84 is provided on the other side of the gear shaft 44 (=the side opposite to the rotor shaft 42). On one side of the gear shaft 44 (=the rotor shaft 42 side), the gear shaft 44 is supported by the housing 18 via the friction damper 56, the rotor shaft 42, and the second bearing 82. The reduction gear 32 is located between the second bearing 82 and the third bearing 84. In addition, in order to support the thrust of the gear shaft 44 by the housing 18 via the second bearing 82 and the third bearing 84, the outer peripheral surfaces 44o1 and 44o2 of the gear shaft 44 are configured to contact the side walls of the inner ring of the second bearing 82 and the side walls of the inner ring of the third bearing 84, respectively.

[0049] Preferably, the other end of the rotor shaft 42 in the axis C direction extends toward the gear shaft 44 from the second bearing 82. That is, in the axis C direction, the other end of the rotor shaft 42 is located at the position of the second bearing 82.

[0050] According to the present embodiment, (a) a spline fitting portion 50 in which the inner circumferential surface 42i of the rotor shaft 42 and the outer circumferential surface 44o of the gear shaft 44 are spline-fitted, a socket joint portion 52 in which the inner circumferential surface 42i of the rotor shaft 42 and the outer circumferential surface 44o of the gear shaft 44 are in contact with and fit together, and a vibration damping portion 54 in which a friction vibration damper 56 is provided between the inner circumferential surface 42i of the rotor shaft 42 and the outer circumferential surface 44o of the gear shaft 44, are arranged in sequence in the direction of the axis C from the side of the second electric motor MG2, and (b) a second bearing 82 is provided at a position overlapping with the vibration damping portion 54 when viewed in the radial direction. In the case where the spline fitting portion 50, the socket joint portion 52, and the damping portion 54 are arranged in order from the second electric motor MG2 side in the axis C direction as described above, it is not necessary to make the outer diameter of the damping portion 54 larger than the socket joint portion 52 in the gear shaft 44, compared with the case where the spline fitting portion 50, the damping portion 54, and the socket joint portion 52 are arranged in order from the second electric motor MG2 side in the axis C direction. Accordingly, it is not necessary to increase the outer diameter of the damping portion 54 in the rotor shaft 42, that is, the outer diameter of the portion with the largest outer diameter in the rotor shaft 42. Therefore, in the case where the spline fitting portion 50, the socket joint portion 52, and the damping portion 54 are arranged in order from the second electric motor MG2 side in the axis C direction as described above, it is possible to reduce the outer diameter of the portion with the largest outer diameter in the rotor shaft 42, compared with the case where this is not the case. As a result, the loss at the bearing is reduced, and the increase in the weight of the power transmission device 40 is suppressed. In addition, by arranging a part of the spline fitting portion 50 at a position overlapping with the rotor MG2r in the axis C direction, the length of the rotor shaft 42 and the gear shaft 44 as a whole in the axis C direction can be shortened. Thus, for example, the length of the drive unit 70 in the axis C direction of the mechatronic drive unit can be shortened and miniaturized.

[0051] In addition, the above contents are embodiments of the present invention, and the present invention can be implemented in variously modified and improved forms based on the knowledge of those skilled in the art within the scope not departing from the gist of the present invention.

[0052] In the aforementioned embodiment, the “elastic member” in the present invention is the friction damper 56 , but is not limited thereto, and may be, for example, a well-known tolerance ring.

Claims

1. A power transmission device (40) for a vehicle (10), wherein a rotor shaft (42) and a gear shaft (44) of an electric motor (MG2) are connected to each other in such a way as to form a common axis (C), wherein the power transmission device (40) for the vehicle (10) is characterized in that: In the direction of the axis (C), a spline fitting portion (50) in which the inner circumferential surface (42i) of the rotor shaft (42) and the outer circumferential surface (44o) of the gear shaft (44) are spline-fitted, a socket joint portion (52) in which the inner circumferential surface (42i) of the rotor shaft (42) and the outer circumferential surface (44o) of the gear shaft (44) are in contact with and fit with each other, and a vibration damping portion (54) in which an elastic member (56) is arranged between the inner circumferential surface (42i) of the rotor shaft (42) and the outer circumferential surface (44o) of the gear shaft (44) are sequentially arranged from the motor (MG2) side. A bearing (82) is provided at a position overlapping the vibration damping portion (54) when viewed in the radial direction of the rotor shaft (42) and the gear shaft (44).

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