Power transmission device for vehicle

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 to form a common axis. [Background technology]

[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 to form a common axis, and in which, in the axial direction, a splined engagement portion in which the inner peripheral surface of the rotor shaft and the outer peripheral surface of the gear shaft are splined 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 are arranged in that order from the electric motor side. For example, the device 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 a non-rotating member. Specifically, four bearings are provided at a total of four locations, namely, 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] JP 2018-135934 A Summary of the Invention [Problem to be solved by the invention]

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

[0005] The present invention has been made in light of the above circumstances, and an object of the present invention is to provide a power transmission device for a vehicle in which loss in bearings is reduced and an increase in weight is suppressed. [Means for solving the problem]

[0006] The gist of the present invention is 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, and (a) in the axial direction, arranged in order from the electric motor side, are a splined engagement portion in which the inner surface of the rotor shaft and the outer surface of the gear shaft are splined and engaged, a spigot portion in which the inner surface of the rotor shaft and the outer surface of the gear shaft are in contact with each other and engaged, and a damper portion in which an elastic member is disposed between the inner surface of the rotor shaft and the outer surface of the gear shaft, and (b) a bearing is provided at a position overlapping with the damper portion when viewed radially of the rotor shaft and the gear shaft. Effect of the Invention

[0007] According to the power transmission device for a vehicle of the present invention, (a) in the axial direction, a splined fitting portion in which the inner peripheral surface of the rotor shaft and the outer peripheral surface of the gear shaft are spline-fitted, a spigot portion in which the inner peripheral surface of the rotor shaft and the outer peripheral surface of the gear shaft are in contact with each other and 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 are arranged, and (b) a bearing is provided at a position overlapping with the damper portion when viewed in the radial direction of the rotor shaft and the gear shaft. In this way, when the splined fitting portion, the spigot portion, and the damper portion are arranged in the axial direction in the order from the electric motor side, the outer diameter of the rotor shaft at the damper portion, i.e., the outer diameter of the part of the rotor shaft with the largest outer diameter, can be made smaller than when they are not arranged. This reduces loss in the bearing and suppresses an increase in the weight of the power transmission device. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic configuration diagram of a vehicle equipped with a power transmission device according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view illustrating the configuration of the power transmission device shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that in the embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios and shapes of the various parts are not necessarily drawn accurately. EXAMPLES

[0010] FIG. 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 driving the vehicle, 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 that is a non-rotating member attached to the vehicle body.

[0012] The transaxle 72 is accommodated inside the case 18. For example, the power output from the engine 12 is mechanically divided by the power split mechanism 36 to the first electric motor MG1 and the drive gear 22. The first electric motor MG1 generates electricity by the power of the engine 12 divided to the first electric motor MG1. The generated electric power Wmg1 by the first electric motor MG1 is charged to a battery (not shown), or all or a part of the generated electric power Wmg1 or electric power from the battery in addition to the generated electric power Wmg1 is used to rotate the second electric motor MG2. The power split mechanism 36 functions as an electric continuously variable transmission in which the differential state of the power split mechanism 36 is controlled by controlling 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, the driven shaft 26, the final gear 28, and the 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 so as to be able to 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 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 battery (not shown) and the first and second electric motors MG1 and MG2. The PCU38 includes an inverter. The inverter converts a direct current supplied from the battery into an alternating current for driving the first and second electric motors MG1 and MG2, and also converts the alternating currents generated by the first and second electric motors MG1 and MG2 into direct currents. The PCU38 is controlled by an electronic control device (not shown) in accordance with the running state of the vehicle 10, thereby controlling the output of each of the first and second electric motors MG1 and MG2.

[0014] The drive unit 70 is a unit in which a transaxle 72 and the PCU 38 are housed and integrated in the same case 18, that is, an electrically and mechanically integrated drive unit.

[0015] Here, the meaning of “the same case” will be explained. The case 18 is made of, for example, an aluminum alloy casting, and includes a first case portion 60, a second case portion 62, a third case portion 64, and a fourth case portion 66.

[0016] The first case part 60 is a cylindrical member with a bottom. The second case part 62 is a cylindrical member with a bottom, and a partition wall 62d is provided therein. For example, the second case part 62 is integrally formed by casting a bottom wall, a side wall extending upward from the outer periphery of the bottom wall, and the partition wall 62d. The second case part 62 has an opening on its upper surface. The side wall of the second case part 62 has openings on the engine 12 side and the opposite side to the engine 12 in a portion below the partition wall 62d. The first case part 60 and the second case part 62 are integrally connected by a fastener such as a bolt 68a (see FIG. 2) so that the opening of the first case part 60 and the opening of the side wall of the second case part 62 on the engine 12 side are aligned. By connecting the second case part 62 to the first case part 60, the case 18 has an upper space U and a lower space L separated in the up-down direction by the partition wall 62d. Here, the part of the case 18 surrounding the upper space U is referred to as the upper case part 18U, and the part of the case 18 surrounding the lower space L is referred to as the lower case part 18L. In the vertical direction, the lower case part 18L is a part of the case 18 that is provided below the upper case part 18U. The lower part of the upper case part 18U and the upper part of the lower case part 18L form a common partition wall 62d. Therefore, when the upper case part 18U and the lower case part 18L are separated, the inside of at least one of the upper case part 18U and the lower case part 18L is necessarily exposed to the outside. "The same case" means a case in which the inside of at least one of the upper case part 18U and the lower case part 18L is exposed to the outside when the upper case part 18U and the lower case part 18L are separated in this way.

[0017] The third case portion 64 is a plate-like member joined to the second case portion 62 so as to close an opening in the side wall of the second case portion 62 on the side opposite to the engine 12. The second case portion 62 and the third case portion 64 are integrally connected by a fastener such as a bolt 68b (see FIG. 2). The fourth case portion 66 is a plate-like member joined to the second case portion 62 so as to close an opening in the upper surface of the second case portion 62. The second case portion 62 and the fourth case portion 66 are integrally connected by a fastener such as a bolt 68c (see FIG. 2).

[0018] When mounted on vehicle 10, transaxle 72 is housed in lower case portion 18L. That is, transaxle 72 is provided in lower space L. When mounted on vehicle 10, PCU 38 is housed in upper case portion 18U. That is, PCU 38 is provided in 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 taken along 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 periphery of the rotor shaft 42 is connected to the inner periphery of the rotor MG2r of the second electric motor MG2 so as not to rotate relative to the rotor MG2r.

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

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

[0023] The splined engagement portion 50 is a portion where the inner peripheral surface 42i of the rotor shaft 42 and the outer peripheral surface 44o of the gear shaft 44 are splined. In the splined engagement portion 50, the spline teeth 42s provided on the inner peripheral surface 42i of the rotor shaft 42 and the spline teeth 44s provided on the outer peripheral surface 44o of the gear shaft 44 are splined. Between the spline teeth 42s and the spline teeth 44s, there is backlash in the rotation direction. Due to the relative rotational fluctuation 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, causing rattling noise (tooth rattling noise). For example, the above-mentioned relative rotational fluctuation occurs when the output torque of the second electric motor MG2 fluctuates or when the output torque of the second electric motor MG2 is approximately zero and the rotor shaft 42 is rotated by the gear shaft 44 in an unloaded state. The splined engagement portion 50 transmits force in the rotational direction between the rotor shaft 42 and the gear shaft 44 .

[0024] The spigot portion 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 come into contact with and are fitted together. When the rotor shaft 42 and the gear shaft 44 are connected to each other, the spigot portion 52 prevents the axes of the rotor shaft 42 and the gear shaft 44 from misaligning.

[0025] The damper portion 54 is a portion where 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. The friction damper 56 corresponds to the "elastic member" in the present invention. In the damper portion 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 an annular space between the inner peripheral surface 42i of the rotor shaft 42 and the outer peripheral surface 44o of the gear shaft 44 in the damper portion 54. The friction damper 56 is a known friction damper including, for example, an annular metal portion and an elastic body (e.g., rubber) attached to the outer peripheral surface of the metal portion. The metal portion of the friction damper 56 is fitted into the outer peripheral surface 44o of the gear shaft 44, and the elastic body of the friction damper 56 is press-fitted between the metal portion and the inner peripheral surface 42i of the rotor shaft 42. The friction damper 56 suppresses the generation of rotational rattle noise at the spline engagement portion 50 by applying a predetermined frictional resistance in the rotational direction, but has little effect in suppressing misalignment of the axes of the rotor shaft 42 and the gear shaft 44.

[0026] The power transmission device 40 is provided with three bearings (a first bearing 80, a second bearing 82, and a third bearing 84) so ​​as to be supported by the case 18 (specifically, the second case portion 62), which is a non-rotating member. These three bearings are, for example, ball bearings, and can support both the radial load and the thrust load of the rotor shaft 42 and the gear shaft 44. 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 in the direction of the axis C, respectively. The second bearing 82 is provided at a position between the first bearing 80 and the third bearing 84 in the direction of the axis C and at a position overlapping with the damper portion 54 in the radial view of the rotor shaft 42 and the gear shaft 44 (hereinafter simply referred to as the "radial view"). 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. Also, a portion of the damper portion 54 may be provided at a position overlapping with the rotor MG2r when viewed in the radial direction.

[0027] In the direction of the axis C, 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 direction of the axis C, 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 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. In addition, in order to support the thrust force of the gear shaft 44 by the case 18 via the second bearing 82 and the third bearing 84, the outer peripheral surfaces 44o1, 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 the axis C does not extend further toward the gear shaft 44 than the second bearing 82. That is, the other end of the rotor shaft 42 in the direction of the axis C is located at the position of the second bearing 82.

[0029] According to this embodiment, (a) in the direction of the axis C, from the second electric motor MG2 side, there are arranged a spline fitting portion 50 in which the inner surface 42i of the rotor shaft 42 and the outer peripheral surface 44o of the gear shaft 44 are spline-fitted, a spigot portion 52 in which the inner surface 42i of the rotor shaft 42 and the outer peripheral surface 44o of the gear shaft 44 are in contact with and fitted to each other, and a damper portion 54 in which a friction damper 56 is arranged between the inner surface 42i of the rotor shaft 42 and the outer peripheral surface 44o of the gear shaft 44, and (b) a second bearing 82 is provided at a position overlapping with the damper portion 54 when viewed in the radial direction. In this way, when the spline fitting portion 50, the spigot portion 52, and the damper portion 54 are arranged in this order from the second electric motor MG2 side in the direction of the axis C, it is not necessary to make the outer diameter of the damper portion 54 larger than that of the spigot portion 52 in the gear shaft 44, compared to when the spline fitting portion 50, the damper portion 54, and the spigot portion 52 are arranged. Accordingly, it is not necessary to make the outer diameter of the damper portion 54 in the rotor shaft 42, i.e., the outer diameter of the portion of the rotor shaft 42 with the largest outer diameter, larger. Therefore, when the spline fitting portion 50, the spigot portion 52, and the damper portion 54 are arranged in this order from the second electric motor MG2 side in the direction of the axis C, it is possible to make the outer diameter of the portion of the rotor shaft 42 with the largest outer diameter smaller than when they are not arranged. This reduces loss in the bearings and suppresses an increase in the weight of the power transmission device 40. Furthermore, by providing a portion of the spline fitting portion 50 at a position overlapping with the rotor MG2r in the direction of the axis C, it is possible to shorten the length of the rotor shaft 42 and the gear shaft 44 in the direction of the axis C. This makes it possible to reduce the length of the drive unit 70, which is an electrically and mechanically integrated drive unit, in the direction of the axis C and make it more compact.

[0030] It should be noted that the above is an embodiment of the present invention, and the present invention can be embodied in various forms with various modifications and improvements based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

[0031] In the above embodiment, the "elastic member" in the present invention is the friction damper 56, but 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 peripheral surface, 50: spline fitting portion, 52: spigot portion, 54: damper portion, 44: gear shaft, 44o: outer peripheral surface, 56: friction damper (elastic member), 82: second bearing (bearing), C: axis, MG2: second electric motor (electric motor)

Claims

[Claim 1] A power transmission device for a vehicle, in which a rotor shaft of an electric motor and a gear shaft are connected to each other so as to have a common axis, In the axial direction, there are arranged, in order from the electric motor side, a splined engagement portion in which an inner peripheral surface of the rotor shaft and an outer peripheral surface of the gear shaft are spline-engaged, a spigot portion in which the inner peripheral surface of the rotor shaft and the outer peripheral surface of the gear shaft are in contact with each other and engaged, 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, A bearing is provided at a position overlapping with the damper portion when viewed in a radial direction of the rotor shaft and the gear shaft. A power transmission device for a vehicle.

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