Hybrid Transaxle Layout With Counter Shaft for Shorter Case Length
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The increase in the overall size of the engine and transaxle case in hybrid electric vehicles due to overlapping disposition of the engine and stepped-pinion-type planetary gear device leads to degraded aerodynamic characteristics and reduced vehicle design flexibility.
Innovation Solution
The configuration of the hybrid electric vehicle includes a planetary gear device, a first electric motor, and a crankshaft rotatable around a first axis, a second electric motor and differential gear device rotatable around a second axis, with a counter shaft and counter gears providing motive power input, and at least part of the differential gear device or counter shaft protruding beyond the engine-transaxle interface, eliminating the need for a large ring gear and reducing the transaxle case's dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the engine and stepped-pinion-type planetary gear device are disposed at overlapping positions, then the axial length is reduced, but the outside diameter increases requiring larger axis-to-axis distance
Solution Approach 1:
The patent changes the arrangement from a two-dimensional planar layout to a three-dimensional spatial arrangement. The counter shaft is positioned along the second axis (parallel to the first axis) rather than in the radial direction, allowing components to be stacked axially. This dimensional reorganization enables overlapping disposition of the engine and planetary gear device without increasing the transaxle case's outside diameter, thus reducing axial length while maintaining compact overall size.
Solution Approach 2:
The patent implements a nested arrangement where the counter shaft and counter drive gear are positioned within the spatial envelope of the engine and transaxle case. Specifically, the counter drive gear with smaller diameter is arranged to fit within the radial space, and the counter shaft extends along the axial direction, creating a compact nested configuration that maximizes space utilization without increasing external dimensions.
2Area of stationary object
If the counter drive gear with smaller diameter is used, then the transaxle case size is reduced, but the power transmission efficiency may be compromised
Solution Approach 1:
The patent changes the geometric parameters of the gear system by using a counter drive gear with a smaller diameter than conventional designs. This parameter change reduces the radial space required, allowing compact transaxle case design. The smaller diameter gear is compensated by optimizing the meshing arrangement with the differential gear device and positioning the counter shaft along the axial direction, maintaining adequate contact ratio and tooth engagement to preserve power transmission efficiency despite the reduced size.
Data Source
AI summary
A counter driven gear into which motive power is input from a second electric motor, a counter drive gear that has a smaller diameter than the counter driven gear and drives a differential gear device, and a counter shaft constitute a speed reduction mechanism. This eliminates the need for a ring gear on an outer side of a stepped pinion, and thus prevents an increase in an outside diameter of a first case cover on an engine side that protrudes from a case main body of a transaxle case so as to house the speed reduction mechanism. At least either part of the differential gear device or part of the counter shaft is disposed so as to protrude toward the engine side beyond an interface between the engine and the transaxle case, which can shorten a dimension of the transaxle case in the direction of a second axis.