Vehicle power transmission system

Abstract

To provide a power transmission device for a vehicle in which bearing losses are reduced and an increase in weight is suppressed.SOLUTION: (a) In an axial C direction, from a second electric motor MG2 side in order, a spline fitting section 50 where a rotor shaft 42 and a gear shaft 44 are spline-fitted, a spigot section 52 where an inner circumferential surface 42i of the rotor shaft 42 and an outer circumferential surface 44o of the gear shaft 44 are in contact with each other and fitted together, and a damper section 54 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 are arranged. (b) In a radial view of the rotor shaft 42 and the gear shaft 44, a second bearing 82 is provided at a position overlapping with the damper section 54.SELECTED DRAWING: Figure 2

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 so as to have a common axis.

Background Art

[0002] There is known a power transmission device for a vehicle in which a rotor shaft of an electric motor and a gear shaft are connected so as to have a common axis. In the axial direction thereof, in order from the motor side, there are arranged a spline fitting portion in which the inner peripheral surface of the rotor shaft and the outer peripheral surface of the gear shaft are spline-fitted, and a damper portion in which an elastic member is disposed between the inner peripheral surface of the rotor shaft and the outer peripheral surface of the gear shaft. For example, the one described in Patent Document 1 is such a device. In the power transmission device for a vehicle described in Patent Document 1, four bearings are provided so as to be supported by non-rotating members. Specifically, four bearings are provided at a total of four positions at both ends of the rotor shaft and both ends of the gear shaft in the axial direction.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the vehicle power transmission device described in Patent Document 1, it is conceivable to reduce the number of bearings to three in order to reduce losses in the bearings. For example, in the vehicle power transmission device described in Patent Document 1, the number of bearings on the motor side of the gear shaft is reduced, and a spigot portion is provided on the gear shaft side of the damper portion in the axial direction in order to suppress misalignment of the axes of the rotor shaft and the gear shaft. However, if the spline fitting portion, damper portion, and spigot portion are arranged in the axial direction from the motor side in order, the outer diameter of the spigot portion on the gear shaft must be made larger than that of the damper portion by the amount of elastic member provided. Consequently, the outer diameter of the spigot portion on the rotor shaft, that is, the outer diameter of the largest outer diameter part on the rotor shaft, must also be made larger. This leads to an increase in the weight of the power transmission device.

[0005] The present invention was made against the above circumstances, and its objective is to provide a vehicle power transmission device that reduces losses in the bearings and suppresses an increase in weight. [Means for solving the problem]

[0006] The gist of this invention is the rotor shaft of an electric motor and A reduction gear, which is a helical gear, is provided. A vehicle power transmission device connected to a gear shaft so as to share a common axis, wherein (a) in the axial direction, in order from the motor side, a spline fitting portion is arranged in which the inner circumferential surface of the rotor shaft and the outer circumferential surface of the gear shaft are spline fitted together, a spigot portion is arranged in contact with and fitted together the inner circumferential surface of the rotor shaft and the outer circumferential surface of the gear shaft, and a damper portion is arranged in which an elastic member is disposed between the inner circumferential surface of the rotor shaft and the outer circumferential surface of the gear shaft, and (b) A first bearing is provided on the rotor shaft opposite to the gear shaft, (c) In a radial view of the rotor shaft and the gear shaft, at a position that overlaps with the damper portion 2nd A bearing is provided. (d) A third bearing is provided on the gear shaft opposite to the rotor shaft, and (e) the outer surface of the gear shaft is configured to contact the side wall of the inner ring of the second bearing and the side wall of the inner ring of the third bearing, respectively. It is what is happening. [Effects of the Invention]

[0007] According to the vehicle power transmission device of the present invention, (a) in the axial direction, in order from the motor side, a spline fitting portion is arranged in which the inner circumferential surface of the rotor shaft and the outer circumferential surface of the gear shaft are spline fitted together, a spigot portion is arranged in contact with and fitted together the inner circumferential surface of the rotor shaft and the outer circumferential surface of the gear shaft, and a damper portion is arranged in which an elastic member is disposed between the inner circumferential surface of the rotor shaft and the outer circumferential surface of the gear shaft, (b) A first bearing is provided on the rotor shaft opposite to the gear shaft, (c) In a radial view of the rotor shaft and the gear shaft, at a position that overlaps with the damper portion 2nd A bearing is provided. (d) A third bearing is provided on the gear shaft opposite to the rotor shaft, and (e) the outer surface of the gear shaft is configured to contact the side wall of the inner ring of the second bearing and the side wall of the inner ring of the third bearing, respectively. In this way, when the spline fitting portion, spigot portion, and damper portion are arranged in the axial direction from the motor side, the outer diameter of the rotor shaft at the damper portion, that is, the outer diameter of the largest part of the rotor shaft, can be reduced compared to the case where they are not arranged in this way. By reducing the number of bearings to three Losses in the bearings are reduced, 、 The increase in weight of the power transmission system is suppressed. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of a vehicle equipped with a power transmission device according to an embodiment. [Figure 2] Figure 1 is a cross-sectional view illustrating the configuration of the power transmission device. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the embodiments, the drawings have been simplified or modified as appropriate, and the dimensional ratios and shapes of each part are not necessarily depicted accurately. [Examples]

[0010] Figure 1 is a schematic diagram of a vehicle 10 equipped with a power transmission device 40 according to an embodiment.

[0011] The first motor MG1 and the second motor MG2 are power sources for propulsion and are, for example, three-phase synchronous motors that are so-called motor generators. The first motor MG1 and the second motor MG2 are housed in a case 18, which is a non-rotating member attached to the vehicle body.

[0012] The transaxle 72 is housed inside the case 18. For example, the power output from the engine 12 is mechanically divided by the power split mechanism 36 into a first electric motor MG1 and a drive gear 22. The power of the engine 12 divided to the first electric motor MG1 generates electricity. The electricity Wmg1 generated by the first electric motor MG1 is used to charge a battery (not shown), or all or part of the generated electricity Wmg1, or electricity from the battery in addition to the generated electricity Wmg1, is used to rotate the second electric motor MG2. The power split mechanism 36 functions as an electrically operated continuously variable transmission in which the differential state of the power split mechanism 36 is controlled by the operating state of the first electric motor MG1. The power of the engine 12 divided to the drive gear 22 is transmitted to the driven gear 24, driven shaft 26, final gear 28, and differential 30. The second electric motor MG2 is connected to the driven shaft 26 via a power transmission device 40, a reduction gear 32, and a driven gear 24 to transmit power. The power transmission device 40 comprises the 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 a common axis C. The output of the transaxle 72 is transmitted to a pair of drive wheels 14 via a pair of axles 34 connected to the differential 30, etc.

[0013] The power control unit 38 (hereinafter referred to as "PCU38") is a power control device that controls the power exchanged between the aforementioned battery (not shown) and the first motor MG1 and the second motor MG2. The PCU38 is equipped with an inverter. The inverter converts the DC current supplied from the battery into AC current to drive the first motor MG1 and the second motor MG2, and also converts the AC current generated by the first motor MG1 and the second motor MG2 into DC current. The PCU38 is controlled by an electronic control device (not shown) according to the driving state of the vehicle 10, thereby controlling the output of the first motor MG1 and the second motor MG2.

[0014] The drive unit 70 is a unit in which the transaxle 72 and the PCU 38 are housed in the same case 18 and integrated, i.e., a mechatronic integrated drive unit.

[0015] From here, the meaning of "identical case" will be explained. Case 18 is made of, for example, an aluminum alloy casting and comprises a first case section 60, a second case section 62, a third case section 64, and a fourth case section 66.

[0016] The first case section 60 is a bottomed cylindrical member. The second case section 62 is a bottomed cylindrical member with a partition wall 62d inside. For example, the second case section 62 has a bottom wall, a side wall extending upward from the outer edge of the bottom wall, and the partition wall 62d, all integrally formed by casting. The second case section 62 has an opening on its upper surface. The portion of the side wall of the second case section 62 below the partition wall 62d has openings on the engine 12 side and on the opposite side of the engine 12. The first case section 60 and the second case section 62 are integrally connected by fasteners such as bolts 68a (see Figure 2) so that the opening of the first case section 60 and the opening of the side wall of the second case section 62 on the engine 12 side are aligned. When the second case section 62 is connected to the first case section 60, the case 18 has an upper space U and a lower space L separated vertically by the partition wall 62d. Here, the portion of case 18 that surrounds the upper space U is referred to as the upper case section 18U, and the portion of case 18 that surrounds the lower space L is referred to as the lower case section 18L. In the vertical direction, the lower case section 18L is the portion of case 18 that is located below the upper case section 18U. Below the upper case section 18U and above the lower case section 18L is a common partition wall 62d. Therefore, when the upper case section 18U and the lower case section 18L are separated, the interior of at least one of the upper case section 18U and the lower case section 18L will always be exposed to the outside. "Same case" means a case in which, when the upper case section 18U and the lower case section 18L are separated, the interior of at least one of them is exposed to the outside.

[0017] The third case section 64 is a plate-shaped member joined to the second case section 62 so as to close the opening on the side wall of the second case section 62 that is opposite to the engine 12. The second case section 62 and the third case section 64 are integrally connected by fasteners such as bolts 68b (see Figure 2). The fourth case section 66 is a plate-shaped member joined to the second case section 62 so as to close the opening on the upper surface of the second case section 62. The second case section 62 and the fourth case section 66 are integrally connected by fasteners such as bolts 68c (see Figure 2).

[0018] When mounted on the vehicle 10, the transaxle 72 is housed in the lower case portion 18L. That is, the transaxle 72 is provided in the lower space L. When mounted on the vehicle 10, the PCU 38 is housed in the upper case portion 18U. That is, the PCU 38 is provided in the upper space U.

[0019] FIG. 2 is a cross-sectional view for explaining the configuration of the power transmission device 40 shown in FIG. 1. FIG. 2 is a cross-sectional view in the direction of the axis C.

[0020] 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 peripheral portion of the rotor shaft 42 is non-rotatably connected to the inner peripheral portion of the rotor MG2r of the second electric motor MG2.

[0021] The gear shaft 44 is cylindrical. A reduction gear 32 is provided on the outer peripheral portion of the gear shaft 44. The reduction gear 32 is meshed with the driven gear 24. The reduction gear 32 and the driven gear 24 are, for example, helical gears, and the meshing ratio is increased to make the power transmission quiet and have little torque fluctuation. When the reduction gear 32 and the driven gear 24 are helical gears, a thrust force is generated on the gear shaft 44. The thrust force is a thrust in the direction of the axis C (= thrust direction). This thrust force is in the opposite direction when the vehicle 10 is moving forward and when it is moving backward.

[0022] In the direction of the axis C, in order from the second electric motor MG2 side, a spline fitting portion 50, an in-roll portion 52, and a damper portion 54 are arranged.

[0023] The spline fitting portion 50 is the area where the inner circumferential surface 42i of the rotor shaft 42 and the outer circumferential surface 44o of the gear shaft 44 are spline-fitted. In the spline fitting portion 50, the spline teeth 42s provided on the inner circumferential surface 42i of the rotor shaft 42 and the spline teeth 44s provided on the outer circumferential surface 44o of the gear shaft 44 are spline-fitted. There is rotational play (backlash) between the spline teeth 42s and the spline teeth 44s. Due to relative rotational fluctuations of the rotor shaft 42 and the gear shaft 44, the spline teeth 42s and the spline teeth 44s may repeatedly experience tooth surface separation and tooth surface collision in the rotational direction, potentially generating rattling noise (tooth noise). For example, the aforementioned relative rotational fluctuations occur when the output torque of the second motor MG2 fluctuates or when the output torque of the second motor MG2 is approximately zero and the rotor shaft 42 is rotated along with the gear shaft 44 in an unloaded state. The spline fitting portion 50 transmits rotational force between the rotor shaft 42 and the gear shaft 44.

[0024] The spigot portion 52 is the area where the inner circumferential surface 42i of the rotor shaft 42 and the outer circumferential surface 44o of the gear shaft 44 come into contact and are fitted together. When the rotor shaft 42 and the gear shaft 44 are connected, the spigot portion 52 prevents the axes of the rotor shaft 42 and the gear shaft 44 from shifting.

[0025] The damper section 54 is the part in which 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 this invention. In the damper section 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 damper section 54. The friction damper 56 is a well-known friction damper comprising, for example, an annular metal part and an elastic body (for example, rubber) attached to the outer circumferential surface of the metal part. The metal part of the friction damper 56 is fitted onto the outer circumferential surface 44o of the gear shaft 44, and the elastic body of the friction damper 56 is press-fitted between the metal part and the inner circumferential surface 42i of the rotor shaft 42. The friction damper 56 suppresses the generation of rattling noise in the spline fitting portion 50 in the rotational direction by applying a predetermined frictional resistance in the rotational direction, but it has little effect in suppressing the misalignment of the axes of the rotor shaft 42 and the gear shaft 44.

[0026] The power transmission device 40 is supported by a non-rotating case 18 (specifically, the second case portion 62) and is equipped with three bearings (first bearing 80, second bearing 82, and third bearing 84). These three bearings are capable of supporting both radial and thrust loads on the rotor shaft 42 and gear shaft 44, and are, for example, ball bearings. In the direction of axis C, 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 gear shaft 44 are connected. The second bearing 82 is provided at a position between the first bearing 80 and the third bearing 84 in the direction of axis C, and at a position that overlaps with the damper portion 54 in a radial view of the rotor shaft 42 and gear shaft 44 (hereinafter simply referred to as "radial view"). The second bearing 82 corresponds to the "bearing" in this invention. Preferably, in a radial view, at least a portion of the spline fitting portion 50 is positioned to overlap with the rotor MG2r. Alternatively, in a radial view, a portion of the damper portion 54 may be positioned to overlap with the rotor MG2r.

[0027] In the direction of axis C, the first bearing 80 is located on one side of the rotor shaft 42 (opposite to the gear shaft 44), and the second bearing 82 is located on the other side of the rotor shaft 42 (gear shaft 44 side). The rotor MG2r is located between the first bearing 80 and the second bearing 82. In the direction of axis C, the second bearing 82 is located on one side of the gear shaft 44 (rotor shaft 42 side), and the third bearing 84 is located on the other side of the gear shaft 44 (opposite to the rotor shaft 42). On one side of the gear shaft 44 (rotor shaft 42 side), the gear shaft 44 is supported by the case 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. Furthermore, in order to support the thrust force of the gear shaft 44 in the case 18 via the second bearing 82 and the third bearing 84, the outer circumferential surfaces 44o1 and 44o2 of the gear shaft 44 are configured to contact the side walls of the inner rings of the second bearing 82 and the third bearing 84, respectively.

[0028] Preferably, the other end of the rotor shaft 42 in the direction of axis C does not extend further toward the gear shaft 44 than the second bearing 82. That is, in the direction of axis C, the other end of the rotor shaft 42 is at the position of the second bearing 82.

[0029] In this embodiment, (a) in the direction of axis C, from the second motor MG2 side, a spline fitting portion 50 is arranged 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 together, an inverted fitting portion 52 is arranged in contact with the inner circumferential surface 42i of the rotor shaft 42 and the outer circumferential surface 44o of the gear shaft 44, and a damper portion 54 is arranged in which 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, and (b) in a radial view, a second bearing 82 is provided at a position overlapping with the damper portion 54. Thus, when the spline fitting portion 50, the spigot portion 52, and the damper portion 54 are arranged in the direction of axis C, starting from the second motor MG2 side, it is not necessary to make the outer diameter of the damper portion 54 larger than the spigot portion 52 on the gear shaft 44 compared to when the spline fitting portion 50, the damper portion 54, and the spigot portion 52 are arranged. Consequently, it is not necessary to increase the outer diameter of the damper portion 54 on the rotor shaft 42, that is, the outer diameter of the largest part of the rotor shaft 42. Therefore, when the spline fitting portion 50, the spigot portion 52, and the damper portion 54 are arranged in the direction of axis C, starting from the second motor MG2 side, the outer diameter of the largest part of the rotor shaft 42 can be reduced compared to when they are not arranged. As a result, bearing losses are reduced and the increase in weight of the power transmission device 40 is suppressed. Furthermore, by positioning a portion of the spline fitting portion 50 in the direction of axis C so that it overlaps with the rotor MG2r, the overall length of the rotor shaft 42 and gear shaft 44 in the direction of axis C can be shortened. This makes it possible to shorten the length of the drive unit 70, which is a mechatronic integrated drive unit, in the direction of axis C, thereby making it more compact.

[0030] The above-described examples are embodiments of the present invention, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art, without departing from its spirit.

[0031] In the above-described embodiment, the "elastic member" in the present invention was a friction damper 56, but it is not limited to this, and may be, for example, a well-known tolerance ring. [Explanation of Symbols]

[0032] 10: Vehicle, 40: Power transmission device, 42: Rotor shaft, 42i: Inner circumferential surface, 50: Spline fitting part, 52: Arbor part, 54: Damper part, 44: Gear shaft, 44o: Outer circumferential surface, 56: Friction damper (elastic member), 82: Second bearing (bearing), C: Axle, MG2: Second motor (motor)

Claims

[Claim 1] A vehicle power transmission device in which the rotor shaft of an electric motor and a gear shaft equipped with a reduction gear, which is a helical gear, are connected so as to share a common axis, In the axial direction, starting from the motor side, the following are arranged: a spline fitting portion in which the inner circumferential surface of the rotor shaft and the outer circumferential surface of the gear shaft are spline-fitted; a spigot portion in which the inner circumferential surface of the rotor shaft and the outer circumferential surface of the gear shaft are in contact and fitted together; and a damper portion in which an elastic member is disposed between the inner circumferential surface of the rotor shaft and the outer circumferential surface of the gear shaft. A first bearing is provided on the rotor shaft opposite to the gear shaft. In a radial view of the rotor shaft and the gear shaft, a second bearing is provided at a position overlapping with the damper portion. A third bearing is provided on the gear shaft opposite to the rotor shaft. The outer circumferential surface of the gear shaft is configured to contact the side wall of the inner ring of the second bearing and the side wall of the inner ring of the third bearing, respectively. A vehicle power transmission device characterized by the following features.

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