8-Speed Dual-Clutch Gearbox Layout for Compact High Torque
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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 space-constrained 2-shaft configurations with limited axial length and high torque requirements.
Innovation Solution
The gearbox design features an inner and outer input drive shaft with gears arranged on a counter-shaft, utilizing synchroniser sleeves for gear selection and idler gears for reverse, with some gears permanently fixed and others in revolute relations, allowing for axial movement to engage and lock gears, and employing cluster gears and shrink fits to optimize space and torque handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a large ratio spread is achieved with high gear-spread, then vehicle fuel consumption and CO2 emission are reduced, but the gearbox axial length increases
Solution Approach 1:
The patent employs a nested arrangement where the inner input shaft (10) is positioned concentrically within the outer input shaft (40), and both are nested within the counter-shaft (70) housing. This nesting of shafts and gears in concentric arrangements allows achieving a large ratio spread without increasing the axial length, as the gears are arranged radially rather than axially.
Solution Approach 2:
The patent transitions from traditional axial gear arrangement to radial/concentric arrangement. By organizing the gear trains in the radial dimension rather than extending axially, the design achieves high gear-spread while maintaining compact axial length, effectively moving the solution to another spatial dimension.
2Force
If high torque capacity is achieved, then the gearbox can handle higher loads, but the shaft diameter and overall size increase
Solution Approach 1:
The patent utilizes composite construction in the gear components, combining different materials to achieve high torque capacity while minimizing weight. The use of optimized material compositions allows the gears and shafts to withstand high torque loads without requiring excessive diameter or mass.
Solution Approach 2:
The design applies local quality optimization by concentrating material and structural strength only where torque transmission is required, rather than uniformly increasing shaft diameter throughout. The concentric shaft arrangement allows for optimized local reinforcement at critical stress points while maintaining lighter overall construction.
3Speed
If the number of mechanical steps for gear change is reduced, then shifting speed is enhanced, but the complexity of the synchroniser mechanism increases
Solution Approach 1:
The patent merges the synchroniser functions for multiple gears into a single integrated synchroniser assembly. The synchroniser mechanism is designed to handle both odd and even gear selections through a unified structure, reducing the number of separate mechanical steps required for gear changes while consolidating the complexity into a single coordinated system.
Solution Approach 2:
The synchroniser mechanism is designed with multi-functionality to select both odd-numbered gears (via inner input shaft) and even-numbered gears (via outer input shaft) through a single operational sequence. This universal design reduces the number of mechanical steps by eliminating redundant selection mechanisms.
4Volume of moving object
If a 2-shaft design is used to meet space restrictions, then the gearbox is more compact, but the torque capacity and reliability are reduced
Solution Approach 1:
The patent segments the torque transmission path into two separate concentric shafts (inner shaft 10 and outer shaft 40), each handling specific gear trains. This segmentation allows the 2-shaft design to maintain torque capacity by distributing the torque transmission load across multiple parallel paths rather than overloading a single shaft, thereby preserving reliability while achieving compactness.
Solution Approach 2:
The nested concentric arrangement of the inner and outer shafts within the counter-shaft housing maximizes the use of available space. This nesting allows both shafts to transmit torque simultaneously without increasing the overall gearbox volume, maintaining reliability through redundant torque paths while meeting space restrictions.
Data Source
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AI summary
The invention relates to 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 (75, 77, 74, 76, 78, 11, 42, 13, 49) 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.