Dual Clutch Transaxle Compact Layout for Fuel Efficiency
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Solution Overview
Problem
Automobile manufacturers face challenges in improving fuel efficiency by increasing the number of speed ratios in transmissions while maintaining a compact engine compartment, particularly for transverse-mounted powertrains, as this requires a longer transmission that restricts gear size selection and freedom.
Innovation Solution
A dual clutch transaxle design that minimizes the number of gear planes by using a single input gear meshing with gears on two layshafts, allowing for two gear ratios with a single plane of gears, and employing coupler assemblies with sliding sleeves to selectively engage gears, enabling a higher achievable gear ratio and reducing the physical length of the transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the number of speed ratios is increased to improve fuel efficiency, then fuel efficiency is improved, but the transmission length increases which restricts engine compartment compactness
Solution Approach 1:
The patent employs two parallel layshafts (first and second layshafts) instead of a single layshaft, creating a two-dimensional gear arrangement. This allows multiple gear ratios to be achieved through selective engagement of gears on different layshafts without increasing the transmission's axial length, thereby resolving the contradiction between achieving high fuel efficiency through multiple speed ratios and maintaining compact transmission length for engine compartment constraints
Solution Approach 2:
The coupler assembly serves multiple functions: it selectively engages different gears with the output shaft, couples between the two layshafts, and provides a unified control mechanism for gear selection. This multi-functionality allows the transmission to achieve multiple gear ratios through a single compact assembly rather than requiring separate mechanisms for each ratio, thus improving fuel efficiency while maintaining compact dimensions
2Length of moving object
If the transmission length is reduced to maintain compact engine compartment, then compactness is improved, but the achievable gear ratio is limited
Solution Approach 1:
The transmission is segmented into two independent but parallel gear train systems, each on a separate layshaft. This segmentation allows each layshaft to carry multiple gears with different ratios, and the coupler can selectively engage any combination, thereby achieving a wide range of gear ratios within a compact single-plane structure without requiring a long transmission housing
3Adaptability or versatility
If more gear planes are used to achieve higher gear ratios, then gear ratio capability is improved, but the transmission becomes more complex and longer
Solution Approach 1:
Instead of stacking multiple gear planes axially (which increases length and complexity), the patent uses a second dimension by introducing parallel layshafts. This allows multiple gears to be arranged side-by-side on different layshafts within the same axial plane, achieving high gear ratio capability while reducing the number of gear planes to just two, thereby simplifying the overall structure
Data Source
AI summary
A dual clutch transaxle provides eight forward gear ratios and two reverse gear ratios. The gears are arranged in seven gear planes. Four coupler assemblies are arranged to selectively sequentially engage each adjacent pair of the eight forward gear ratios to permit shifting among the eight forward gear ratios with continuous transmission of torque through the transaxle.