Dual-Clutch Transmission Shift Reversal for Continuous Torque
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Solution Overview
Problem
Dual-clutch transmissions (DCTs) have not been widely adopted in off-road vehicles due to high manufacturing costs and packaging issues in the engine compartment, despite offering good shifting performance and efficiency.
Innovation Solution
A method for controlling a powertrain of a vehicle with a dual-clutch transmission, including a first and second clutch, allows gear changes without interrupting torque distribution, and involves shifting the subtransmission to a neutral gear setting before engaging different gears, optimizing engine torque and clutch torque to facilitate efficient gear shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a dual-clutch transmission is used in off-road vehicles, then shifting performance and efficiency are improved, but manufacturing costs and packaging complexity increase
Solution Approach 1:
The transmission system is divided into a main transmission with dual-clutch mechanism and a subtransmission with high/low gear settings. This segmentation allows each subsystem to be optimized independently, with the dual-clutch mechanism handling rapid gear changes while the subtransmission provides terrain-appropriate gear ratios, thereby improving shifting performance without overwhelming the packaging space with a single monolithic complex system.
Solution Approach 2:
The subtransmission is integrated within the overall transmission assembly, with the high transmission gear and low transmission gear mounted on the input shaft in a compact arrangement. The subtransmission shares space with the main transmission components, effectively nesting one transmission system within another to reduce overall packaging volume while maintaining dual-clutch shifting capabilities.
2Productivity
If a dual-clutch transmission is used in off-road vehicles, then shifting performance and efficiency are improved, but manufacturing costs increase
Solution Approach 1:
The transmission system combines multiple functions into a unified design: the dual-clutch mechanism provides rapid gear switching, the subtransmission offers high/low gear selection for different terrains, and the integrated control system manages torque distribution. This multi-functionality reduces the need for separate systems, thereby lowering overall manufacturing costs while maintaining high shifting efficiency.
Solution Approach 2:
The main transmission and subtransmission are merged into a single integrated assembly, sharing common components such as the input shaft, clutch mechanisms, and control systems. This merging reduces the total number of parts, simplifies manufacturing processes, and lowers assembly complexity, thereby reducing manufacturing costs while preserving the high shifting efficiency characteristic of dual-clutch transmissions.
3Force
If the subtransmission shifts from high gear to low gear during vehicle motion, then torque multiplication is improved, but shifting complexity and torque interruption increase
Solution Approach 1:
The method shifts the subtransmission to neutral gear before engaging the desired high or low transmission gear. This preliminary action of moving to neutral first reduces the complexity of direct gear-to-gear shifting, allows for smoother torque transition, and enables the system to prepare the appropriate gear engagement sequence in advance, thereby achieving torque multiplication with reduced shifting complexity.
Solution Approach 2:
The neutral gear setting acts as an intermediary state between high gear and low gear engagements. By introducing this intermediate neutral position, the system facilitates smoother transitions, reduces mechanical shock during gear changes, and simplifies the shifting mechanism by providing a buffer state, thereby achieving torque multiplication while managing shifting complexity.
4Ease of operation
If engine torque and clutch torque are reduced during gear shifting, then shifting smoothness is improved, but power transmission interruption increases
Solution Approach 1:
The dual-clutch mechanism ensures continuous torque transmission by having one clutch engaged while the other is disengaged, and vice versa during gear shifts. This continuity of useful action maintains power transmission throughout the shifting process, reducing interruptions while the torque reduction during transition improves shifting smoothness, effectively resolving the contradiction between smoothness and power continuity.
Data Source
AI summary
A method for controlling a powertrain of a vehicle, the powertrain a dual-clutch transmission including a first clutch and a second clutch selectively actuated to transmit motion from the engine to a first shaft and a second shaft respectively. The method includes producing a first shift request for shifting from an initial gear to a different gear; in response to the first shift request, executing a first shift sequence to shift from the initial gear to the different gear; during execution of the first shift sequence, producing a second shift request for shifting from the different gear to the initial gear; in response to the second shift request: interrupting the first shift sequence prior to the first shift sequence having finished; and executing a second shift sequence to reverse the first shift sequence such that the transmission engages the initial gear for driving on the first shaft.