CVT Ratio Control Using Actual Engine Torque to Prevent Stalling
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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 the CVT ratio set point that incorporates both actual RPM and engine torque values, using averaging techniques to stabilize calculations and adjust ratio changing rates based on torque thresholds to prevent stalling and enhance driving dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional CVT control uses only RPM for ratio set point determination, then the control system is simple, but engine stalling occurs when torque is near limits and performance is sluggish when torque is low
Solution Approach 1:
The control system implements feedback by continuously monitoring actual engine torque and using it to dynamically adjust the CVT ratio set point. The controller receives torque information from the engine and modifies the ratio control accordingly, creating a closed-loop system that prevents stalling conditions while optimizing performance based on real-time engine state.
Solution Approach 2:
The system transitions from a static RPM-based ratio control to a dynamic control approach where the ratio set point is continuously adjusted based on varying engine torque conditions. The controller adapts the CVT ratio in real-time according to torque thresholds and engine state, enabling the system to respond dynamically to changing operating conditions.
2Reliability
If CVT ratio is adjusted quickly during high torque conditions, then engine stalling is prevented, but acceleration feel may become abrupt
Solution Approach 1:
The control system applies partial action by using torque thresholds to determine the degree of ratio adjustment. Instead of always making maximum adjustments, the controller selectively applies ratio changes based on whether torque exceeds specific thresholds, allowing for graduated responses that prevent stalling while maintaining smooth acceleration characteristics during normal operation.
Solution Approach 2:
The system changes control parameters dynamically by adjusting the ratio set point based on torque conditions. When torque exceeds thresholds indicating potential stalling, the controller modifies the ratio parameter more aggressively, while during normal conditions it maintains smoother, more gradual parameter changes for comfortable acceleration.
3Productivity
If CVT ratio set point is increased with RPM in conventional systems, then the system operates simply, but the vehicle appears sluggish when actual engine torque is low
Solution Approach 1:
The control system takes preliminary action by proactively adjusting the CVT ratio set point based on predicted torque conditions. By monitoring engine torque and preemptively modifying the ratio before performance degradation occurs, the system optimizes acceleration response without waiting for RPM-based triggers, delivering better performance ahead of time.
Data Source
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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.