Dual-Clutch 8-Speed Gearbox Layout for Compact High Ratio Spread
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Solution Overview
Problem
Current 8-speed gearboxes for automotive dual-clutch transmissions face challenges in achieving a large ratio spread, compact design, high torque capacity, lightweight construction, and reduced mechanical wear, particularly in 2-shaft designs with limited axial length and space restrictions.
Innovation Solution
The gearbox design features an inner and outer input drive shaft with counter-shaft configuration, utilizing synchroniser sleeves for gear selection and permanent axial fixation of gears to reduce axial length, and employs cluster gears and shrink fits to optimize gear placement and shaft diameter, allowing for a 2-shaft design with integrated and cluster gears to achieve a high ratio spread and compact size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a large ratio spread is achieved with more than 8 speeds, then fuel consumption and CO2 emission are reduced, but the axial length and overall size of the gearbox increase
Solution Approach 1:
The patent employs a nested shaft configuration where an inner input drive shaft is positioned within an outer input drive shaft. This allows gears for odd-numbered speeds to be mounted on the inner shaft and gears for even-numbered speeds on the outer shaft, enabling multiple gear sets to occupy the same axial space. This nesting arrangement achieves a large ratio spread across 8 speeds while maintaining a compact axial length.
2Force
If high torque capacity is achieved, then the gearbox can handle higher loads, but the minimum shaft diameter increases, leading to heavier weight
Solution Approach 1:
The patent segments the torque transmission paths by providing separate inner and outer input drive shafts, each supporting specific gear sets. This segmentation allows optimized diameter selection for each shaft based on its specific torque requirements, rather than designing a single shaft to handle all torque loads. The counter-shaft with multiple gear pairs also segments the power flow paths, enabling lighter overall construction while maintaining high torque capacity.
3Productivity
If the number of mechanical steps for gear change is reduced, then shifting speed is improved, but the complexity of the synchroniser mechanism increases
Solution Approach 1:
The patent implements preliminary action by pre-configuring the dual-clutch system to selectively engage either the inner or outer input drive shaft before gear selection occurs. This allows the gearbox to switch between different gear sets (odd or even speeds) at the clutch level before the synchroniser needs to operate, reducing the number of mechanical steps required for gear changes and enabling faster shifting.
4Length of stationary object
If a 2-shaft design is used to meet space restrictions, then the axial length is reduced, but the gear layout and shaft diameter requirements become more constrained
Solution Approach 1:
The patent resolves the constraints of a 2-shaft design by transitioning to a multi-dimensional arrangement with concentric inner and outer shafts. This adds a radial dimension to the traditional single-plane gear layout, allowing gears for both odd and even speeds to be mounted on different radial levels. This dimensional change enables a compact axial length while providing sufficient space for complex gear layouts and accommodating various shaft diameter requirements.
Data Source
AI summary
Disclosed is an 8-speed gearbox for a dual clutch transmission, with a particular gear arrangement of the gears on the countershaft, wherein the speed or reverse gear of a gear pair that is a permanently rotationally and axially fixed gear is the radially smaller of the gear pair. One or two cluster gears may be provided, each cluster gear having two gears axially paired attached to the countershaft by a shrink fit connection.