US-12623533-B1 - Vehicle drive device

US12623533B1US 12623533 B1US12623533 B1US 12623533B1US-12623533-B1

Abstract

A vehicle drive device includes a traction motor having an output shaft that is hollow, a speed reducer coupled to the output shaft, a differential gear that distributes a drive force of the traction motor transmitted through the speed reducer to a pair of drive wheels, and a transmission shaft that extends through a through hole of the output shaft along an axial direction of the traction motor and is spline-fitted to a side gear of the differential gear by spline provided on an outer peripheral surface of a first end portion of the transmission shaft. The transmission shaft includes a first flow path that extends along the axial direction and a second flow path that has a first end that is open to the first flow path and the second end that is open to the outer peripheral surface of the transmission shaft.

Inventors

Yoshito SEKIGUCHI
Tomoaki FURUKAWA

Assignees

TOYOTA JIDOSHA KABUSHIKI KAISHA

Dates

Publication Date: 20260512
Application Date: 20250703
Priority Date: 20241114

Claims (3)

1 . A vehicle drive device comprising: a traction motor including an output shaft that is hollow; a speed reducer coupled to the output shaft; a differential gear configured to distribute a drive force of the traction motor transmitted through the speed reducer to a pair of drive wheels; and a transmission shaft that extends through a through hole of the output shaft along an axial direction of the traction motor and that is spline-fitted to a side gear of the differential gear by a spline provided on an outer peripheral surface of a first end portion of the transmission shaft, wherein: the transmission shaft includes a first flow path extending along the axial direction, and a second flow path having a first end that is open to the first flow path and a second end that is open to the outer peripheral surface of the transmission shaft; the second end of the second flow path is positioned on a tooth root portion of the spline; at least a part of the speed reducer is disposed between the traction motor and the differential gear in the axial direction; a spline fitting portion where the transmission shaft and the side gear are spline-fitted includes a third flow path; the third flow path is at least a part of a flow path that allows a lubricant flowing out from the second end of the second flow path to flow to a side where the at least a part of the speed reducer is present in the axial direction and guides the lubricant to an outside of a casing of the differential gear; the spline fitting portion includes a sealing portion that seals the third flow path; and the sealing portion is disposed on a side opposite to the side where the at least a part of the speed reducer is present in the axial direction with respect to a position of the second end of the second flow path.
2 . The vehicle drive device according to claim 1 , wherein: a part of the spline provided on the outer peripheral surface of the transmission shaft has a missing tooth; and the second end of the second flow path is positioned on an enlarged tooth root portion in which tooth root portions adjacent to each other are connected due to the missing tooth.
3 . The vehicle drive device according to claim 2 , wherein the enlarged tooth root portion is disposed on a side where at least a part of the speed reducer is present in the axial direction with respect to a position of the second end of the second flow path.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims priority to Japanese Patent Application No. 2024-199281 filed on Nov. 14, 2024. The disclosure of the above-identified application, including the specification, drawings, and claims, is incorporated by reference herein in its entirety. BACKGROUND 1. Technical Field The technique disclosed in the present specification relates to a vehicle drive device. 2. Description of Related Art In Japanese Unexamined Patent Application Publication No. 2024-025399 (JP 2024-025399 A), a vehicle drive device in which a traction motor, a speed reducer, and a differential gear are disposed on the same axis is disclosed. In such a drive device, an output shaft of the traction motor is configured to be hollow, and a transmission shaft extends through a through hole of the output shaft along an axial direction of the traction motor. A first end portion of the transmission shaft is coupled to a differential gear, and a second end portion of the transmission shaft is coupled to a drive shaft. SUMMARY The transmission shaft is provided with a flow path through which a lubricant that lubricates a lubrication target portion, such as a speed reducer, flows. The flow path provided in the transmission shaft includes a flow path extending along an axial direction and a flow path extending in a radial direction from the flow path extending in the axial direction and opens to an outer peripheral surface. The lubricant flowing out of the flow path extending in the radial direction is supplied to the lubrication target portion. There is concern that a strength of the transmission shaft may be decreased at a portion of the transmission shaft where the flow path extending in the radial direction opens to the outer peripheral surface. The present specification provides a technique for suppressing a decrease in strength of the transmission shaft in which a flow path through which a lubricant flows is provided. A vehicle drive device according to the present specification may include a traction motor, a speed reducer, a differential gear, and a transmission shaft. The traction motor includes an output shaft that is hollow. The speed reducer is coupled to the output shaft. The differential gear distributes a drive force of the traction motor transmitted through the speed reducer to a pair of drive wheels. The transmission shaft extends through a through hole of the output shaft along an axial direction of the traction motor, and is spline-fitted to a side gear of the differential gear by a spline provided on an outer peripheral surface of a first end portion of the transmission shaft. The transmission shaft may include a first flow path that extends along the axial direction and a second flow path that has a first end that is open to the first flow path and a second end that is open to the outer peripheral surface of the transmission shaft. The second end of the second flow path may be positioned on a tooth root portion of the spline. As for a load is applied to a portion of the transmission shaft in which the spline is provided when the transmission shaft rotates, a large load is applied to the gear portion (that is, the protruding portion) of the spline, whereas a large load is not applied to the tooth root portion of the spline. In the vehicle drive device, the second flow path is open to the tooth root portion of the spline to which a large load is not applied. Therefore, the second flow path can be provided in the transmission shaft while the decrease in strength of the transmission shaft is being suppressed. BRIEF DESCRIPTION OF THE DRAWINGS Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein: FIG. 1 is a diagram schematically showing a configuration of a vehicle; FIG. 2 is a diagram showing a skeleton diagram of a drive device mounted in the vehicle; FIG. 3 is a diagram schematically showing a main part cross-sectional view of a vicinity of a spline fitting portion of a transmission shaft and a differential gear in an embodiment; and FIG. 4 is a diagram schematically showing a perspective view of an end portion of the transmission shaft coupled to the differential gear. DETAILED DESCRIPTION OF EMBODIMENTS Hereinafter, a drive device mounted in a vehicle will be described with reference to the drawings. Here, each direction in some drawings is substantially the same as the direction of the vehicle. The direction FR indicates a front in the front-rear direction of the vehicle, and the direction RR indicates a rear in the front-rear direction of the vehicle. In addition, the direction LH indicates the left side in the left-right direction of the vehicle, and the direction RH indicates the right side in the left-right direction of the vehicle. In addition, the direction UP indicates an upward direction in th