CVT Gear Ratio Control for Cornering Re-acceleration
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Solution Overview
Problem
Continuously variable transmission (CVT) vehicles experience significant power loss and delayed acceleration response during cornering due to large inertia forces and the need for rapid gear ratio changes, which deteriorates drivability and acceleration performance.
Innovation Solution
A method of controlling CVT vehicles during cornering involves determining the necessity of an auxiliary control process based on vehicle speed, gear ratio, brake pressure, steering angle, and pulley RPM, and performing pre-emptive gear shifting to set a target gear ratio that optimizes acceleration performance by increasing the gear ratio and engine speed before re-acceleration, using a controller to manage the CVT and adjust the gear shifting speed to sports mode settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high-speed-based shift settings are used to improve fuel economy, then fuel economy is improved, but acceleration response deteriorates
Solution Approach 1:
The controller performs preliminary gear ratio adjustment before the vehicle actually needs to accelerate. When cornering is detected (steering angle exceeds threshold), the system proactively adjusts the CVT gear ratio to a lower value and increases engine RPM in advance, so that when acceleration is needed after the corner, the vehicle is already in an optimal state for rapid acceleration, eliminating the need for reactive downshifting.
2Use of energy by moving object
If CVT operates in high speed range with low gear ratio, then fuel economy is improved, but power loss during downshifting increases
Solution Approach 1:
Instead of allowing the vehicle to enter a high-speed/low-gear ratio state and then requiring energy-intensive downshifting, the system performs preliminary action by detecting cornering conditions and proactively adjusting the gear ratio to an optimal value before acceleration is needed. This prevents the need for subsequent downshifting operations that would cause significant power loss.
3Use of energy by moving object
If damper clutch is directly connected to crankshaft to improve fuel economy, then fuel economy is improved, but acceleration response time increases
Solution Approach 1:
The system compensates for the damper clutch's slow response by performing preliminary action - adjusting the CVT gear ratio and engine RPM in advance during cornering. This proactive adjustment ensures that when acceleration is required, the vehicle is already near the optimal operating point, reducing the effective response time despite the damper clutch's inherent delay.
4Ease of operation
If gear ratio is maintained according to shift pattern during cornering, then drivability is maintained, but re-acceleration performance deteriorates
Solution Approach 1:
The system dynamically adjusts the gear ratio based on real-time detection of cornering conditions. When cornering is detected (steering angle exceeds threshold), the controller temporarily overrides the standard shift pattern to maintain a lower gear ratio and higher engine RPM. After cornering ends, the system returns to normal shift pattern operation, thus dynamically adapting between drivability and acceleration performance needs.
Data Source
AI summary
A method of controlling driving of a CVT vehicle during cornering performed by a controller, may include determining whether it is necessary to perform an auxiliary control process to enhance a re-acceleration response after entering the corner, by determining a travelling state of the vehicle; setting a target gear ratio instead of a gear ratio obtained based on a shift pattern when the determining produces an affirmative result indicating that it is necessary to perform the auxiliary control process; and performing gear shifting of a CVT to follow the target gear ratio set in the setting of the gear ratio.