Dual-Clutch Downshift Control for Stronger Deceleration Feel
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Solution Overview
Problem
Dual-clutch, servo-assisted transmissions in vehicles do not effectively convey the expected significant change in longitudinal deceleration during a shift to a lower gear, leading to a perception of reduced performance among drivers, despite improved gear shift sensations in existing methods.
Innovation Solution
A method controlling the shift to a lower gear by synchronizing the rotation speed of the internal combustion engine with the incoming clutch, temporarily increasing torque transmission to accelerate the engine using kinetic energy, and optionally activating the engine to assist in synchronization, without significantly jeopardizing performance or comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a progressive gear ratio shortening is used during shift to lower gear, then transmission performance is improved, but driver perception of performance deteriorates
Solution Approach 1:
The patent applies dynamics by making the gear ratio change progressive rather than abrupt. The control unit progressively shortens the gear ratio during the shift operation, creating a dynamic transition that smoothly adjusts the mechanical relationship between engine and wheels. This dynamic approach resolves the contradiction by maintaining continuous torque transmission while gradually changing the gear ratio, thereby preserving both transmission performance and driver perception of performance.
Solution Approach 2:
The patent utilizes parameter changes by modifying the gear ratio parameter progressively during the shift operation. The control unit adjusts the gear ratio from its initial value to the final value in a controlled, progressive manner rather than making an abrupt change. This parameter transformation allows the system to maintain optimal performance characteristics while creating a perceptible change that aligns with driver expectations during downshifting.
2Speed
If engine is activated during synchronization to assist torque generation, then synchronization speed is improved, but energy consumption increases
Solution Approach 1:
The patent applies preliminary action by activating the engine in advance of the actual need for torque during the synchronization process. The control unit detects the upcoming synchronization requirement and activates the engine beforehand, allowing it to build up rotational speed and torque capacity before the clutch engagement requires maximum torque transmission. This preliminary activation reduces the peak energy demand during the critical synchronization moment while still achieving fast synchronization.
Solution Approach 2:
The patent utilizes periodic action by controlling the engine activation and deactivation in a timed sequence during the shift operation. The engine is activated periodically only when needed for synchronization assistance and deactivated when not required, creating a rhythmic on-off pattern that optimizes energy usage. This periodic engagement strategy ensures the engine provides assistance only during the critical synchronization phase rather than running continuously.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method provides a sports-like driving sensation while avoiding the risk of wheel blockage, maintaining driving comfort, and ensuring easy implementation without additional components or complex calculations.
Implementation Method 1
controlling the incoming clutch between the second instant and the third instant so as to have the incoming clutch temporarily transmit a greater torque than the braking torque of the internal combustion engine in order to accelerate the internal combustion engine using the kinetic energy owned by the road vehicle
Data Source
AI summary
A method to control the execution of a shift to a lower gear while an accelerator pedal is released in a drivetrain provided with a dual-clutch, servo-assisted transmission; the control method comprises the following steps: opening, in a first instant, an outgoing clutch; closing, in the first instant, an incoming clutch; completing the opening of the outgoing clutch and the closing of the incoming clutch in a second instant; synchronizing, between the second instant and a third instant, a rotation speed of the internal combustion engine with a rotation speed of the incoming clutch; and controlling the incoming clutch between the second instant and the third instant so as to have the incoming clutch temporarily transmit a greater torque than the torque that the clutch is going to transmit immediately after the shift to a lower gear and than the torque that the outgoing clutch transmitted immediately before the shift to a lower gear.