CVT Ratio Control Using Actual Engine Torque Feedback
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Solution Overview
Problem
Conventional CVT control systems do not utilize actual engine torque data, leading to stalling issues when torque is near limits and sluggish performance when torque is low, as they rely solely on RPM for ratio set point determination.
Innovation Solution
A method for controlling CVT ratio set points by calculating and using actual engine torque values alongside RPM data, adjusting the CVT ratio set points and changing rates based on torque thresholds to prevent stalling and improve driving dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional CVT control increases ratio set point at predetermined constant speed based on RPM, then the control system is simple to operate, but engine stalling occurs when actual engine torque is close to prime mover limit
Solution Approach 1:
The control system implements feedback by continuously monitoring actual engine torque from the prime mover and using this information to dynamically adjust the CVT ratio set point. The controller compares the actual engine torque with the maximum torque capability and modifies the ratio change rate accordingly, preventing stalling while maintaining operational simplicity.
Solution Approach 2:
The system transitions from a static, predetermined constant speed ratio change to a dynamic control approach where the ratio set point adjustment speed varies based on real-time engine torque conditions. The controller dynamically adapts the CVT ratio change rate to match actual engine capabilities, resolving the contradiction between simple operation and reliable stalling prevention.
2Device complexity
If conventional CVT control uses predetermined constant speed for ratio change, then the control logic is simple, but vehicle acceleration feels sluggish when actual engine torque is low
Solution Approach 1:
The control system changes the parameter of ratio set point adjustment speed from a fixed predetermined value to a variable parameter that responds to actual engine torque conditions. When engine torque is low, the controller increases the ratio change rate to improve acceleration response, while maintaining simple control logic through torque-based thresholds.
Solution Approach 2:
The controller uses feedback from actual engine torque sensing to dynamically adjust the CVT ratio change rate. This feedback mechanism allows the system to optimize acceleration performance by accelerating the ratio change when torque is low, without complicating the overall control logic.
3Use of energy by moving object
If CVT ratio set point is increased when RPM increases, then the drivetrain operates efficiently at high RPM, but the system does not respond appropriately to varying torque conditions
Solution Approach 1:
The control system integrates multiple control objectives into a single unified controller that simultaneously manages RPM-based efficiency and torque-based adaptability. The controller performs dual functions: maintaining energy efficiency through RPM-based ratio management while adapting to varying torque conditions through real-time torque monitoring and dynamic adjustment.
Solution Approach 2:
The system uses feedback from both RPM and actual engine torque sensors to make informed ratio set point decisions. This multi-parameter feedback approach allows the drivetrain to operate efficiently across different RPM ranges while simultaneously adapting to varying torque conditions, resolving the contradiction between efficiency and adaptability.
Data Source
AI summary
A drivetrain control and a method for controlling a drivetrain where the actual engine torque of the prime mover is taken into account are described herein. Illustrative embodiments include control systems and methods where the ratio set point of the CVT and/or the rate of the CVT ratio change are modified according to the actual engine torque of the prime mover.