Hybrid Transaxle Axial Length Reduction via Planetary Gear Merging
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Solution Overview
Problem
In hybrid transaxles, the limited space within the engine compartment restricts the arrangement of components, particularly the planetary gear sets and electric machines, making it challenging to optimize the axial length and efficiency of power transmission.
Innovation Solution
The arrangement includes first and second planetary gear sets and electric machines along a common axis, with specific coupling of sprockets and gears to minimize axial length and allow for larger diameter electric machines, and the integration of a differential and pump system to optimize power flow and lubrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the planetary gear sets and electric machines are arranged in a conventional configuration, then the power transmission function is achieved, but the axial length of the transaxle increases and space utilization is reduced
Solution Approach 1:
The patent combines the first and second planetary gear sets with the first and second electric machines along a common axis, merging multiple power transmission functions into a compact arrangement. The ring gear of the first planetary gear set is fixedly coupled to both a first sprocket and a carrier of the second planetary gear set, creating an integrated structure that reduces axial length while maintaining power transmission capability.
Solution Approach 2:
The patent utilizes radial arrangement of components around a common axis to reduce axial length. By positioning planetary gear sets and electric machines in a radial configuration rather than a linear axial arrangement, the design transforms the spatial dimensionality, allowing larger diameter electric machines to be accommodated without increasing axial length.
2Power
If larger diameter electric machines are used to improve power density, then the power transmission efficiency increases, but the axial length and overall size of the transaxle increases
Solution Approach 1:
The patent enables larger diameter electric machines by transitioning from an axial arrangement to a radial arrangement around a common axis. This dimensional change allows the electric machines to be positioned in the radial direction rather than extending axially, thereby increasing power density without compromising axial length constraints.
3Area of stationary object
If the components are arranged to minimize axial length, then space utilization improves, but the power transmission efficiency may be compromised
Solution Approach 1:
The patent merges the planetary gear sets and electric machines into an integrated compact structure where the ring gear of the first planetary gear set is fixedly coupled to both a first sprocket and a carrier of the second planetary gear set. This merging maintains direct mechanical power transmission paths while achieving compact spatial arrangement, thereby preserving power transmission efficiency within limited space.
Solution Approach 2:
The patent segments the power transmission system into distinct functional modules (first planetary gear set with first electric machine, second planetary gear set with second electric machine) arranged along a common axis. This segmentation allows optimized power flow paths for each module while maintaining overall compactness, preventing energy loss through optimized mechanical coupling.
Data Source
AI summary
A power split hybrid transaxle includes an axis transfer chain and a final drive planetary gear set. The components are arranged such that the power split planetary gear set is opposite the final drive planetary gear set with both located at the front of the transmission. This minimized the axial length of the transaxle by limiting the number of components that must be staggered axially. Furthermore, this permits use of electric machines with a large diameter and short axial length which also reduces the total axial length of the transaxle.