Hybrid DCT Downshift Torque Control for Acceleration Linearity
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Solution Overview
Problem
Hybrid vehicles with dual clutch transmission (DCT) experience degraded acceleration linearity and gear shift shock during near stop gear-shift from a second stage to a first stage due to low-speed gear engagement and clutch control delays, leading to vibration and long time lags in acceleration response.
Innovation Solution
A method involving a controller that reduces transmission input torque at the start of downshift to a first stage, determines acceleration via an accelerator pedal sensor, and gradually decreases the torque reduction request amount during the torque phase period after gear engagement, with specific inclinations based on the accelerator pedal opening amount to minimize shock and enhance linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If kick down control is performed at low vehicle speed during down shift to first stage from second stage, then transmission input torque is enhanced and vehicle acceleration is improved, but gear engagement shock and clutch release shock cause input shaft vibration and vehicle shock
Solution Approach 1:
The controller determines whether the accelerator pedal is depressed at a specific time point during the gear shift process (before gear engagement is complete). Based on this preliminary determination, the controller adjusts the torque reduction request amount accordingly. This preliminary action allows the system to prepare appropriate torque control strategies in advance, preventing shock while maintaining acceleration capability.
Solution Approach 2:
The torque reduction request amount is dynamically adjusted based on the timing of accelerator pedal depression relative to gear engagement completion. When acceleration is detected during gear shift, the torque reduction request is reduced in the torque phase period, creating a dynamic control strategy that adapts to real-time driving conditions rather than using fixed torque control.
2Object-affected harmful factors
If torque reduction request is maintained until gear shift termination, then gear engagement shock is reduced, but acceleration response time is delayed significantly
Solution Approach 1:
The torque reduction request amount is dynamically adjusted based on real-time detection of accelerator pedal status during gear shift. When acceleration is detected, the controller reduces the torque reduction request amount in the torque phase period, allowing torque to increase more quickly and improve acceleration response while still managing shock through controlled torque management.
Solution Approach 2:
The controller performs preliminary determination of accelerator pedal status at specific time points during gear shift to proactively adjust torque control strategy. This allows the system to prepare appropriate torque levels in advance, reducing acceleration lag while preventing shock through anticipatory torque management.
3Object-affected harmful factors
If RPM synchronization is delayed to prevent shock, then gear engagement smoothness is improved, but acceleration linearity is degraded
Solution Approach 1:
The control strategy dynamically adjusts torque reduction request amounts based on detected acceleration conditions during gear shift. When acceleration is detected, the torque reduction request is reduced, allowing RPM synchronization to proceed more aggressively while maintaining smoothness through controlled torque management, thereby preserving acceleration linearity.
Solution Approach 2:
The torque reduction request amount parameter is changed dynamically based on accelerator pedal status and gear shift phase. By adjusting this parameter in response to detected acceleration, the system optimizes the balance between smoothness and acceleration linearity, allowing faster RPM synchronization when needed while preventing shock.
Data Source
AI summary
A method of controlling gear shift for a hybrid vehicle with a dual clutch transmission (DCT) may include making a request for reduction in transmission input torque at a time point of entrance into down shift to a first stage from a second stage, determining whether the vehicle is accelerated via manipulation of an accelerator pedal during the down shift, and controlling to begin to gradually reduce an transmission input torque reduction request amount in a torque phase period in which clutch torque is exchanged after a first-stage gear is engaged upon determining that the vehicle is accelerated during the gear shift.