CVT Control Strategy for Acceleration Torque and Fuel Economy
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Solution Overview
Problem
When a driver intends to accelerate with the accelerator pedal, low target engine rotational speed results in low driving force and slow engine speed increase, making it difficult to achieve the intended acceleration.
Innovation Solution
A control method for a continuously variable automatic transmission that controls the transmission ratio to increase engine rotational speed in conjunction with vehicle speed, allowing for continuous downshifting until an upshift occurs, ensuring engine torque and output horsepower are maintained.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the target engine rotational speed is set low when the driver depresses the accelerator pedal, then fuel economy is improved, but the driving force at acceleration start becomes low and engine rotational speed increases slowly
Solution Approach 1:
The patent applies dynamics by making the transmission ratio control strategy adaptive based on driving conditions. The control device dynamically switches between continuous variable control and stepwise gear shift control depending on whether the vehicle is in steady-state cruising or acceleration phases, allowing the system to optimize for fuel economy during cruising while ensuring rapid acceleration when needed
Solution Approach 2:
The patent changes the control parameter from purely continuous variable transmission ratio to a hybrid approach that includes discrete gear shift points. By introducing stepwise gear shift control with specific shift timing and ratio changes, the system can maintain low target engine speeds for fuel economy while periodically increasing engine rotational speed through gear shifts to provide acceleration force
2Use of energy by moving object
If continuous variable transmission control is used to increase engine rotational speed with vehicle speed, then fuel economy is improved, but acceleration performance deteriorates when engine torque is low
Solution Approach 1:
The patent segments the driving cycle into different phases (steady-state cruising and acceleration phases) and applies different control strategies to each segment. During cruising, continuous variable control maintains fuel efficiency, while during acceleration phases, stepwise gear shift control provides the necessary power bursts. The control device determines phase transitions based on accelerator pedal position and vehicle speed
Solution Approach 2:
The patent implements periodic stepwise gear shifts during acceleration to maintain engine operation in the high-torque region. By timing gear shifts to occur when the vehicle has accelerated sufficiently, the system periodically replenishes engine torque output, creating a rhythm of acceleration followed by torque restoration that maintains both fuel economy and acceleration capability
Data Source
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AI summary
In the present invention, when the transmission ratio of a continuously variable transmission, which steplessly shifts gears and outputs engine rotational speed, is controlled so that the engine rotational speed increases in conjunction with an increase in vehicle speed and an upshift will be performed after the vehicle has accelerated, downshifting is continuously performed until the upshift occurs.