Dual-Clutch Transmission Upshift Control for Smooth Acceleration
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Solution Overview
Problem
Current dual-clutch, servo-assisted transmission systems experience uncomfortable gear shifts when upshifting with a released accelerator pedal, characterized by excessive engine speed decrease and subsequent sudden increase, leading to unpleasant driving sensations due to the internal combustion engine operating in engine braking mode.
Innovation Solution
A method that controls the upshift by synchronizing the rotation speed of the internal combustion engine with the incoming gear through a controlled transition of torque between clutches, ensuring continuous torque transmission to the drive wheels, reducing the stress on the drivetrain and eliminating simultaneous opening of both clutches, thereby smoothing the acceleration profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If both clutches are kept open during upshift with released accelerator pedal, then the internal combustion engine can operate in engine braking mode to decrease rotation speed, but the rotation speed decreases too much and causes sudden increase later, generating uncomfortable forward and backward pulls
Solution Approach 1:
The incoming clutch is closed before the outgoing clutch is opened, preparing the incoming gear to receive torque before the outgoing clutch disconnects. This preliminary action ensures continuous torque transmission and prevents excessive engine speed decrease that would cause uncomfortable pulls.
Solution Approach 2:
The method ensures continuous torque transmission to the drive wheels by overlapping the operation of both clutches. The incoming clutch begins transmitting torque before the outgoing clutch fully opens, eliminating the interruption that would cause engine speed to drop too much and then suddenly increase.
2Speed
If the internal combustion engine operates in engine braking mode with both clutches open, then the rotation speed can be synchronized with the following gear, but this causes a first forward pull and subsequently a strong backward pull perceived by drivers
Solution Approach 1:
The incoming clutch is pre-loaded and begins transmitting torque before the outgoing clutch fully opens, cushioning against the sudden change in torque transmission. This prevents the harsh forward and backward pulls by smoothly transitioning the torque load from the outgoing to the incoming clutch.
Solution Approach 2:
The dual-clutch system acts as an intermediary between the engine and the drive wheels, allowing one clutch to be engaged while the other disengages. This intermediary mechanism enables smooth torque transition and eliminates the direct connection interruption that causes uncomfortable pulls.
3Loss of time
If both clutches are opened simultaneously during upshift, then the gear shift can be executed quickly, but the torque transmission is interrupted and causes stress on the drivetrain
Solution Approach 1:
The incoming clutch is closed and begins transmitting torque before the outgoing clutch fully opens. This preliminary engagement ensures that torque transmission is maintained throughout the shift, eliminating drivetrain stress while keeping the shift execution time short.
Solution Approach 2:
By overlapping the engagement of the incoming clutch with the disengagement of the outgoing clutch, the system maintains continuous torque transmission. This continuity prevents the interruption that would cause stress on the drivetrain components.
Data Source
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AI summary
A method to control the execution of a shift to a higher gear with a released accelerator pedal (22) in a drivetrain (6) provided with a dual-clutch, servo-assisted transmission (7), comprising the steps of: opening, in a first instant (t1), an outgoing clutch (16A); closing, in the first instant (t1), an incoming clutch (16B); synchronizing, between a second instant (t2) and a third instant (t4), a rotation speed (ωE) of the internal combustion engine (4) with a rotation speed (ωB) of the incoming clutch (16B), namely with the rotation speed (ωB) imposed by the gear ratio of the following gear (B); completely opening, in the third instant (t4), the outgoing clutch (16A); completely closing, in the third instant (t4), the incoming clutch (16A); keeping the torque (TA) transmitted by the outgoing clutch (16A) constant between the second instant (t2) and a fourth instant (t3); and keeping the torque (TB) transmitted by the incoming clutch (16B) constant between the second instant (t2) and the fourth instant (t3).