CVT Pulley Force Control via Speed Ratio Trajectory
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Solution Overview
Problem
Existing continuously variable transmissions (CVT) systems face challenges in efficiently managing speed ratios and torque transfer, leading to suboptimal fuel consumption and engine performance due to limitations in controlling pulley forces and gear ratios.
Innovation Solution
A powertrain system with a control routine that determines actual, desired, and commanded speed ratios, calculates a total speed ratio change rate, and adjusts pulley forces using a ratio change coefficient and force ratio factor to achieve smooth and responsive gear shifts, optimizing the operation of primary and secondary pulleys in a CVT.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional CVT control methods are used, then the system structure remains simple, but the fuel efficiency and engine performance are suboptimal due to imprecise speed ratio control
Solution Approach 1:
The patent implements dynamic control of pulley forces by continuously adjusting the primary and secondary pulley forces based on real-time speed ratio conditions. The control system dynamically modifies the force ratio factor and ratio change coefficient to optimize fuel efficiency across varying operating conditions, transforming the static CVT control into a dynamic adaptive system.
Solution Approach 2:
The control system employs feedback mechanisms by continuously monitoring the actual speed ratio and comparing it with the desired speed ratio. Based on this feedback, the system adjusts the pulley forces to minimize the difference between actual and desired ratios, thereby optimizing fuel efficiency while maintaining precise control.
2Speed
If conventional pulley force control is used, then the system remains simple, but the responsiveness and smoothness of gear shifts are insufficient
Solution Approach 1:
The control system performs preliminary actions by pre-calculating the force ratio factor and ratio change coefficient based on the desired speed ratio trajectory. This allows the pulley forces to be adjusted proactively rather than reactively, improving the responsiveness and smoothness of gear shifts before the actual ratio change occurs.
Solution Approach 2:
The patent utilizes parameter changes by dynamically modifying the force ratio factor and ratio change coefficient based on the current operating conditions and desired speed ratio. These parameter adjustments enable the system to achieve smooth and responsive gear shifts by optimizing the pulley force distribution across different speed ratio ranges.
3Measurement precision
If precise speed ratio control is implemented, then fuel efficiency improves, but the control system complexity increases
Solution Approach 1:
The control system segments the speed ratio control into distinct phases by separately determining the force ratio factor and ratio change coefficient. This segmentation allows each parameter to be optimized independently for its specific function, achieving precise speed ratio control while managing system complexity through modular control architecture.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system enables precise control of speed ratios and torque transfer, improving fuel efficiency, engine performance, and responsiveness by dynamically managing pulley forces, thereby enhancing the overall operation of the CVT.
Implementation Method 1
Frictional engagement between the sheaves of each pulley and the chain couples the chain to each of the pulleys to transfer torque from one pulley to the other
Data Source
AI summary
A powertrain system including an internal combustion engine rotatably coupled to a variator of a continuously variable transmission (CVT) is described. A method for controlling the CVT includes determining an actual speed ratio, a desired speed ratio and a commanded speed ratio. A total speed ratio change rate is determined based upon the actual speed ratio, the desired speed ratio and the commanded speed ratio, and a commanded speed ratio trajectory is determined based upon the desired speed ratio and the commanded speed ratio. A ratio change coefficient and a force ratio factor are determined based upon the commanded speed ratio trajectory, and a shift force is determined based upon the total speed ratio change rate and the ratio change coefficient. A primary pulley force and a secondary pulley force for the CVT are controlled based upon the shift force and the force ratio factor.