Hybrid Transaxle Axis Transfer Gearing Layout
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Solution Overview
Problem
In hybrid transaxles, the compact space constraints within the engine compartment and the need to minimize passenger compartment intrusion in collisions pose challenges in optimizing the arrangement of components such as electric machines, planetary gear sets, and differentials for efficient power transmission and safety.
Innovation Solution
A hybrid transaxle configuration featuring first and second electric machines, a countershaft, and a planetary gear set, where the electric machines are arranged on distinct axes, and the planetary gear set is positioned to allow for compactness and efficient power splitting, with the sun gear connected to the traction motor and the carrier fixedly coupled to the input shaft, enabling efficient power distribution and reduced axial length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the transaxle components are arranged in a conventional layout, then the power transmission path is straightforward, but the axial length becomes excessive and intrudes into the passenger compartment in collisions
Solution Approach 1:
The patent applies dimensionality change by transitioning from a conventional parallel-axis layout to a spatial arrangement where the planetary gear set and countershaft are positioned at different axial levels. The countershaft is disposed below the planetary gear set, creating a three-dimensional power transmission path that reduces the overall axial length of the transaxle assembly while maintaining functional integrity
Solution Approach 2:
The patent implements nesting by positioning the countershaft and its associated gears within the vertical space occupied by the planetary gear set. The fourth gear on the countershaft meshes with the ring gear of the planetary set, effectively nesting the countershaft transmission path within the planetary gear envelope, thereby compacting the overall structure and reducing axial intrusion
2Length of stationary object
If the transaxle is compacted to reduce axial length, then safety is improved, but the space for arranging electric machines and gear components becomes restricted
Solution Approach 1:
The patent applies segmentation by dividing the power transmission system into distinct functional modules: the planetary gear set for power splitting, the countershaft with multiple gears for power distribution to different wheels, and separate electric machines for traction and generation. This modular segmentation allows each component to be optimized independently while fitting into a compact integrated assembly
Solution Approach 2:
The patent utilizes vertical spacing to resolve component arrangement complexity. The countershaft is positioned below the planetary gear set, and the fourth gear extends upward to mesh with the ring gear. This vertical dimensionality change creates sufficient clearance for all components without increasing axial length, effectively using the third dimension to accommodate complex component layouts
3Object-affected harmful factors
If the electric machines are positioned further forward for safety, then occupant protection is improved, but the power transmission path becomes longer and less efficient
Solution Approach 1:
The patent applies nesting by integrating the electric machine within the planetary gear set envelope. The electric machine's rotor is positioned concentrically with the sun gear, and its output shaft aligns with the sun gear axis. This nested arrangement allows the electric machine to be positioned forward for safety while maintaining a short power transmission path through direct mechanical coupling
Data Source
AI summary
A hybrid transaxle permits location of a traction motor in a more favorable location, decreasing the risk of occupant injury in a vehicle collision. Axis transfer gearing moves the generator off the engine axis. This permits placing the traction motor further forward without interference with the generator.