Third-Countershaft DCT Layout for Reduced Axial Installation Space
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Solution Overview
Problem
Existing transmissions, particularly dual-clutch transmissions with a third countershaft, face challenges in reducing axial installation space requirements, which limits their suitability for compact applications such as front-mounted transverse arrangements in motor vehicles.
Innovation Solution
A six-speed front-transverse double-clutch transmission design featuring six shafts, including coaxial and axially offset shafts, and nine shift elements, with specific rotational connections and gear arrangements that allow for efficient gear shifting while minimizing axial dimensions, incorporating a sixth shaft that integrates an idler and fixed gear to maintain compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a dual-clutch transmission with a third countershaft is used, then gear shifting capability is improved, but axial installation space increases
Solution Approach 1:
The patent implements a nested shaft configuration where the third shaft is positioned coaxially within the hollow second shaft, and the fourth shaft is arranged within the fifth shaft. This nesting arrangement allows multiple shafts to occupy overlapping spatial volumes, significantly reducing the axial installation space required for a six-speed dual-clutch transmission while maintaining the capability to provide six forward gears and reverse gear functionality.
2Adaptability or versatility
If six shafts are arranged with axial offsets, then gear ratio variety is improved, but device complexity increases
Solution Approach 1:
The transmission is segmented into two distinct clutch systems: a first dual-clutch system for odd gear ratios (1st, 3rd, 5th forward gears and reverse) and a second dual-clutch system for even gear ratios (2nd, 4th, 6th forward gears). This segmentation allows each clutch system to be independently controlled and optimized, managing the complexity of six-speed operation through modular organization of the six shafts and nine shift elements.
Solution Approach 2:
The fourth shaft serves multiple functions by being rotationally connectable to both the second shaft (via third shift element for odd gear ratios) and the third shaft (via fifth shift element for even gear ratios). This multi-functionality reduces the need for separate dedicated shafts for each clutch system, thereby managing device complexity while maintaining comprehensive gear ratio coverage.
3Adaptability or versatility
If nine shift elements are used, then gear ratio coverage is improved, but manufacturing complexity increases
Solution Approach 1:
The patent merges the control functions of multiple shift elements into integrated assemblies. The first and second shift elements are combined in a shared housing forming a dual clutch, and the third, fourth, and fifth shift elements are integrated with the fourth shaft. This merging reduces the number of separate manufacturing components and assemblies required, simplifying production while maintaining the nine shift elements needed for complete gear ratio coverage.
Data Source
AI summary
A transmission where a first shaft is rotationally fixable to a third shaft and to a second shaft, the second and third shafts are rotationally connectable to a fourth shaft, the second shaft is rotationally connectable to a fifth shaft, the fourth shaft is rotationally connectable to the fifth shaft, the third shaft is rotationally connectable to the fifth shaft, fixed gears of the fourth and fifth shafts are rotationally connected to a drive output, a first gearwheel of the sixth shaft meshes with a fixed gear of the second shaft, and a second gearwheel of the sixth shaft meshes with a fixed gear of the third shaft. Moreover, a first gearwheel of the sixth shaft is an idler gear and a second gearwheel of the sixth shaft is a fixed gear, or vice versa. Additionally, the idler gear of the sixth shaft is rotationally fixable to the sixth shaft.