Vehicle power transmission device

Abstract

To provide a vehicular power transmission device capable of transmitting vibromotive force generated at an engaging point E of an internal gear to a case and suppressing the generation of excessive torque.SOLUTION: A ring gear R and an intermediate member 36 responsible for torque limitation are spline-fitted with each other, thereby reducing the transmission of vibromotive force generated at an engaging point E of the ring gear R to the intermediate member 36. Or the vibromotive force is transmitted to a case 12 through the intermediate member 36, thereby attenuating the vibromotive force in the intermediate member 36. Consequently, the transmission of the vibromotive force generated at the engaging point E to the case 12 is largely reduced, so that the generation of gear noise is suppressed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power transmission device for a vehicle having a planetary gear set. [Background technology]

[0002] Patent document 1 describes a power transmission device for a vehicle having a structure in which the internal gear (ring gear) of a planetary gear set is fixed non-rotatably to a case (motor housing), and a multi-plate clutch (torque limiting clutch assembly) is attached between the internal gear and the case. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-67182 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in Patent Document 1, the multi-plate clutch is provided near the meshing point of the internal gear, so there is a risk that gear noise will be generated if the vibratory force generated at the meshing point is transmitted directly to the case without being reduced within the multi-plate clutch.

[0005] The present invention has been made against the background of the above circumstances, and its object is to provide a power transmission device for a vehicle that can achieve both torque limitation and suppression of transmission to the case of the vibratory force generated at the meshing point of the internal gear. [Means for solving the problem]

[0006] The gist of the present invention is a power transmission device for a vehicle having a structure in which an internal gear of a planetary gear device is supported non-rotatably on a case, (b) an intermediate member is interposed between the internal gear and the case, the intermediate member having a cylindrical portion and a disk portion that closes one end of the cylindrical portion, forming a cylindrical shape with one open end and a bottom, and serving to limit torque, and (c) an inner peripheral surface of the cylindrical portion of the intermediate member and the internal gear are in contact with each other. Splined, and (d) a press-fit portion is provided in which an inner peripheral surface of an inner peripheral end portion of the disk portion of the intermediate member is press-fitted into an outer peripheral surface of a protrusion that protrudes toward the axial center of the case, and when a torque equal to or greater than a predetermined value is input, the intermediate member and the case so that slippage occurs between them. [Effects of the Invention]

[0007] According to the present invention, the internal gear and the inner peripheral surface of the cylindrical portion of the intermediate member that is responsible for limiting torque are spline-fitted, and the inner peripheral surface of the inner peripheral end of the disk portion of the intermediate member is press-fitted into the outer peripheral surface of the protrusion that protrudes toward the axial center of the case on the axial center side, and the press-fitted portion the intermediate member By setting the internal gear so that slippage occurs between the case and the internal gear, the excitation force generated at each meshing point of the internal gear is canceled and attenuated, and transmission of the excitation force to the case is reduced. This intermediate part One achieves torque limiting and gear noise suppression. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a power transmission device for a vehicle to which the present invention is applied; [Figure 2] FIG. 1 is a cross-sectional view of a conventional power transmission device for a vehicle. DETAILED DESCRIPTION OF THE INVENTION

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

[0010] FIG. 1 is a cross-sectional view of a vehicle power transmission device 10 (hereinafter referred to as power transmission device 10) to which the present invention is applied. The power transmission device 10 includes an electric motor MG, a reduction gear 14 formed of a planetary gear device, and a differential device 16 (hereinafter referred to as differential device 16) housed within a case 12, which is a non-rotating member. Note that the lower half of the device below the rotation axis CL is omitted in FIG. 1. Furthermore, the differential device 16 is a well-known technology, so its description will be omitted.

[0011] The electric motor MG is disposed rotatably about a rotation axis CL. The electric motor MG includes a stator 18 fixed non-rotatably to the case 12 with bolts or the like, a rotor 20 disposed on the inner circumferential side of the stator 18, and a cylindrical rotor shaft 24 connected to the inner circumferential surface of the rotor 20 and rotatably supported by bearings 22 or the like. The power transmission device 10 is configured so that power output from the electric motor MG is transmitted to a pair of left and right axles 25L, 25R via the reduction gear 14 and the differential device 16.

[0012] The reducer 14 is a reduction gear device for reducing the rotation of the electric motor MG and transmitting the rotation to the differential device 16. The reducer 14 is made up of a planetary gear device and includes a sun gear S, a stepped pinion P, a carrier CA, and a ring gear R. The ring gear R is also called an internal gear. The reducer 14 corresponds to the planetary gear device of the present invention, and the ring gear R corresponds to the internal gear of the present invention.

[0013] The sun gear S is formed at the end of the rotor shaft 24 on the reducer 14 side in the direction of the rotation axis CL. The stepped pinion P integrally includes a pinion shaft 26 supported by the carrier CA to be rotatable about its own axis and revolve around the rotation axis CL, a large-diameter pinion gear P1 meshing with the sun gear S, and a small-diameter pinion gear P2 meshing with the ring gear R. The carrier CA is supported rotatably about the rotation axis CL via bearings 28 and the like. Furthermore, the carrier CA rotatably supports both axial ends of the pinion shaft 26 via bearings 30 and 32. As a result, the stepped pinion P can rotate about the central axis CSL of the pinion shaft 26 and revolve around the rotation axis CL. The end of the carrier CA opposite the electric motor MG in the direction of the rotation axis CL is integrally connected to a differential case 34 that constitutes the differential device 16. Therefore, the rotation of the carrier CA is transmitted to the differential device 16 .

[0014] The ring gear R is formed in an annular shape, and has internal teeth formed on its inner peripheral surface that mesh with the small-diameter pinion gear P2. The ring gear R is also made non-rotatable by having its outer peripheral portion fixed to the case 12. With the above-described configuration, the rotation of the electric motor MG is decelerated and transmitted to the differential device 16.

[0015] In a power transmission device 100 with a conventional structure, the ring gear R is fixed directly to the case 102, which is a non-rotating member, as shown in Fig. 2. In this case, the vibratory force generated at the meshing point E between the ring gear R and the small-diameter pinion gear P2 is directly transmitted to the case 102, which may cause gear noise.

[0016] 1, the ring gear R is fixed to the case 12 via an intermediate member 36. That is, the intermediate member 36 is interposed between the ring gear R and the case 12.

[0017] The intermediate member 36 is a cylindrical member that has a bottom and an open end. The intermediate member 36 includes a cylindrical portion 38 and a disk-shaped portion 40 that extends radially inward from one end of the cylindrical portion 38, which is aligned with the rotation axis CL.

[0018] The cylindrical portion 38 is disposed about the rotation axis CL. Internal spline teeth 42 are formed on the inner peripheral surface of the cylindrical portion 38 on the side of the electric motor MG in the direction of the rotation axis CL. Furthermore, external spline teeth 44 that mate with the internal spline teeth 42 are formed on the outer peripheral surface of the ring gear R. These internal spline teeth 42 and external spline teeth 44 mate with each other, thereby spline-fitting the intermediate member 36 and the ring gear R and restricting their relative rotation. A predetermined amount of gap (backlash) is formed between the internal spline teeth 42 and the external spline teeth 44 in the rotation direction.

[0019] The disk portion 40 is connected to one end of the cylindrical portion 38, which is aligned with the rotation axis CL, and extends radially inward about the rotation axis CL. The inner peripheral end of the disk portion 40 is fitted into the outer peripheral surface of a protrusion 12a that protrudes from the case 12 in the direction of the rotation axis CL. The inner peripheral surface of the inner peripheral end of the disk portion 40 is press-fitted into the outer peripheral surface of the protrusion 12a, thereby fixing the intermediate member 36 to the case 12 by press-fitting. Here, when a torque equal to or greater than a predetermined value Tlim is input to the intermediate member 36, slippage occurs between the inner peripheral end of the disk portion 40 and the protrusion 12a.

[0020] The effect of fixing the ring gear R to the case 12 via the intermediate member 36 as described above will be described. When power is transmitted to the reducer 14, a vibratory force is generated at the meshing point E between the ring gear R and the small-diameter pinion gear P2. At this time, the vibratory force is transmitted to the case 12 side via the intermediate member 36. However, because the spline fitting portion 46 and the press-fit portion 48 between the inner peripheral end of the disk portion 40 and the protrusion 12a are located at different positions in the radial direction centered on the rotation axis CL, the vibratory force at each meshing point is canceled out and attenuated while being transmitted to the case 12 (protrusion 12a) via the intermediate member 36. As a result, the vibratory force is transmitted to the case 12 via the spline fitting portion 46 and the intermediate member 36, so the vibratory force transmitted to the case 12 is significantly reduced, and gear noise caused by the vibratory force being transmitted to the case 12 is suppressed.

[0021] Furthermore, when torque equal to or greater than a predetermined value Tlim is input to the ring gear R, slippage occurs at the press-fit portion 48 between the inner circumferential end of the intermediate member 36 and the protrusion 12a. Therefore, even when excessive torque is input from the road surface, for example, slippage occurs at the press-fit portion 48 between the intermediate member 36 and the protrusion 12a, preventing the generation of excessive torque within the power transmission device 10. Here, the predetermined value Tlim is determined in advance experimentally or through design, and is set, for example, to an upper threshold value within a range that does not affect the durability of the components that make up the power transmission device 10.

[0022] As described above, according to this embodiment, the function of the intermediate member 36 is to transmit the vibratory force from the ring gear R to the case 12 via the intermediate member 36, thereby canceling and attenuating the vibratory force within the intermediate member 36. As a result, the transmission of the vibratory force generated at the meshing point E to the case 12 is significantly reduced, thereby suppressing the generation of gear noise. Furthermore, if excessive torque is input to the power transmission device 10 from the road surface, for example, slippage occurs at the press-fit portion 48 between the intermediate member 36 and the case 12, preventing the generation of excessive torque within the power transmission device 10.

[0023] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the present invention can also be applied to other embodiments.

[0024] For example, in the above-described embodiment, the reducer 14 is a planetary gear device with a stepped pinion P, but the present invention is not necessarily limited to a planetary gear device with a stepped pinion P. For example, the present invention can be appropriately applied to any existing single-type or double-type planetary gear device as long as the vehicle power transmission device has a structure in which the ring gear is fixed to the case.

[0025] In addition, in the above-described embodiment, the intermediate member 36 is spline-fitted with the ring gear R and press-fitted into the protrusion 12a of the case 12, but this is not limited to such an embodiment, and the intermediate member 36 may be press-fitted into the ring gear R and spline-fitted into the protrusion 12a of the case 12.

[0026] In the above-described embodiment, the power transmission device 10 uses an electric motor MG as a power source, but the present invention is not limited to a power transmission device for a vehicle that uses an electric motor MG as a power source. For example, the present invention can be applied to a power transmission device for a vehicle that uses an engine as a power source, or a hybrid power transmission device for a vehicle that uses an engine and an electric motor as power sources.

[0027] It should be noted that the above is merely one embodiment, and the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. [Explanation of symbols]

[0028] 10: Vehicle power transmission device 12: Case 14: Reducer (planetary gear device) 36: Intermediate member R: Ring gear (internal gear)

Claims

[Claim 1] A power transmission device for a vehicle having a structure in which an internal gear of a planetary gear device is supported non-rotatably on a case, an intermediate member having a cylindrical portion and a disk portion closing one end of the cylindrical portion, the intermediate member having a bottom and an open end, and serving to limit torque, is interposed between the internal gear and the case; an inner peripheral surface of the cylindrical portion of the intermediate member and the internal gear are spline-fitted, and a press-fit portion is provided in which an inner peripheral surface of an inner peripheral end portion of the disk portion of the intermediate member is press-fitted into an outer peripheral surface of a protrusion provided on the axial center side of the case and protruding in the axial center direction, The press-fit portion is configured so that slippage occurs between the intermediate member and the case when a torque equal to or greater than a predetermined value is input. A power transmission device for a vehicle.

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