Nested Hollow Shaft DCT for Eight-Speed Torque Splitting
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Solution Overview
Problem
Current double clutch transmission (DCT) systems face challenges in achieving a high number of speed stages while maintaining efficiency, fuel economy, and reducing component count and weight, which are essential for environmentally friendly vehicle technologies.
Innovation Solution
The integration of one planetary gear set with two synchronizers in a DCT system, allowing for eight forward speed stages and one reverse speed stage, simplifies the interior layout and reduces weight by minimizing components, and achieves smooth shifting through alternate operation of clutches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional DCT system is used, then the structure is simple, but it cannot achieve eight forward speed stages and one reverse speed stage
Solution Approach 1:
The patent employs nested hollow shafts where the second input shaft is a hollow shaft surrounding the first input shaft, and the third input shaft is a hollow shaft surrounding the second input shaft. This nesting arrangement allows multiple input shafts to occupy the same radial space, enabling eight forward speed stages and one reverse speed stage without proportionally increasing the overall transmission size or structural complexity.
Solution Approach 2:
The patent utilizes the axial dimension by arranging input shafts in a nested hollow configuration rather than radially. This dimensional approach allows multiple shafts to be stacked axially, enabling the achievement of multiple speed stages (8 forward + 1 reverse) while maintaining a compact radial footprint and managing system complexity.
2Use of energy by moving object
If more planetary gear sets are added to increase speed stages, then fuel economy improves, but weight and component count increase
Solution Approach 1:
The compound shifting section with the planetary gear set serves multiple functions: it enables both forward speed stage changes and reverse gear operation, and works in conjunction with the two synchronizers to achieve eight forward speed stages and one reverse speed stage. This multi-functionality reduces the need for separate dedicated components for each function, thereby reducing overall component count and weight while maintaining improved fuel economy through multiple speed stages.
Solution Approach 2:
The patent merges the reverse gear mechanism with the forward speed shifting mechanism by using the same planetary gear set and synchronizers for both functions. The compound shifting section integrates reverse gear capability into the existing multi-speed forward transmission architecture, eliminating the need for a separate reverse gear mechanism and reducing overall component count and weight.
3Use of energy by moving object
If more synchronizers are added to achieve more speed stages, then fuel economy improves, but device complexity increases
Solution Approach 1:
The two synchronizers in the patent serve multiple functions: the first synchronizer manages gear changes in the odd-numbered shift-stage shifting section, while the second synchronizer manages gear changes in the even-numbered shift-stage shifting section. Both synchronizers work with the compound shifting section to enable eight forward speed stages and one reverse speed stage, achieving multi-functionality with minimal component count and reduced complexity.
Solution Approach 2:
The patent segments the speed shifting functions into two distinct sections: odd-numbered shift stages handled by the first synchronizer and even-numbered shift stages handled by the second synchronizer. This segmentation allows each synchronizer to specialize in specific gear changes, achieving efficient control of eight forward speed stages and one reverse speed stage with only two synchronizers, thereby reducing overall device complexity.
4Power
If the transmission system is compacted, then power delivery efficiency improves, but manufacturing precision requirements increase
Solution Approach 1:
The nested hollow shaft configuration compacts the transmission system by allowing multiple input shafts to occupy the same radial space. This nesting arrangement maintains power delivery efficiency through direct torque transmission paths while using standardized shaft and gear components that can be manufactured and assembled with conventional precision tolerances, avoiding the need for excessively tight manufacturing specifications.
Solution Approach 2:
The patent segments the transmission into distinct functional sections (odd-numbered shift-stage shifting section, even-numbered shift-stage shifting section, and compound shifting section), each with its own standardized components. This segmentation allows for modular assembly with conventional precision requirements, maintaining power delivery efficiency through optimized torque paths while using standard manufacturing tolerances for each segmented component.
Data Source
AI summary
A power transmission apparatus includes: a first input shaft; a second input shaft coaxially disposed with the first input shaft and selectively connected with the first input shaft; a third input shaft coaxially disposed with the second input shaft and selectively connected with the first input shaft; a first output shaft in parallel with the first input shaft; a second output shaft arranged in series to and selectively connected with the first output shaft; a first shift-stage shifting section outputting two shifted torques from the third input shaft to the first output shaft; a second shift-stage shifting section outputting one shifted torque and one reverse torque from the second input shaft to the first output shaft; and a compound shifting section outputting a shifted output torque from a received torque selectively from the first input shaft or the first output shaft.