CVT Friction Correction Using Uniform Gear Ratio Factor
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Solution Overview
Problem
In belt-type continuously variable transmissions, it is challenging to accurately correct the default coefficient of friction values stored in the friction map across all gear ratios due to the transient nature of high gear ratio states, leading to potential excessive or insufficient pulley lateral pressure, which can degrade engine fuel consumption or cause belt slip.
Innovation Solution
A coefficient of friction correction device that calculates a single correction factor for a predetermined gear ratio and applies it uniformly to all gear ratios, ensuring reliable correction of default friction values and reducing computational load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the actual coefficient of friction is calculated for each gear ratio to correct the default value, then the correction accuracy for that specific gear ratio is improved, but the system cannot appropriately correct the default value for the entire gear ratio region because high gear ratio states occur only for very short periods
Solution Approach 1:
The patent segments the correction process into two parts: (1) calculating the correction factor based on actual coefficient of friction at a predetermined gear ratio where steady state can be achieved, and (2) applying this correction factor uniformly to all gear ratios through the coefficient of friction map. This segmentation allows accurate correction to be propagated across all operating conditions.
Solution Approach 2:
The correction factor calculated for a specific predetermined gear ratio is made universal and applied to correct the default coefficient of friction values for all gear ratios. This multi-functional application of a single correction factor ensures that the benefits of accurate friction measurement are extended across the entire operating range of the transmission system.
2Reliability
If the default coefficient of friction values are corrected using calculated values from limited operating conditions, then the correction reliability for frequently occurring gear ratios is improved, but the correction accuracy for rare gear ratio states deteriorates
Solution Approach 1:
The patent changes the parameter application scope by taking a correction factor derived from specific operating conditions and applying it as a universal multiplier across all gear ratios. This parameter transformation allows the system to achieve both reliability (through sufficient data from steady-state operation) and broad accuracy (through uniform application across all operating conditions).
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
This approach allows for reliable correction of friction values across all gear ratios, enhancing power transmission efficiency while minimizing the risk of belt slip and ensuring durability, by calculating the correction factor from a frequently occurring gear ratio state, thus improving the precision and frequency of friction calculations.
Implementation Method 1
a coefficient of friction map storing a default value of a coefficient of friction between a pulley and an endless belt for each gear ratio
Data Source
AI summary
A coefficient of friction correction device for a belt-type continuously variable transmission is provided in which the coefficient of friction corrector calculates a coefficient of friction correction factor from the coefficient of friction calculated by the coefficient of friction calculator for a predetermined gear ratio and the default value of the coefficient of friction stored in the coefficient of friction map for the predetermined gear ratio, and uniformly corrects the default value of the coefficient of friction stored in the coefficient of friction map for each gear ratio using the coefficient of friction correction factor. This enables the default values of the coefficient of friction of all the coefficient of friction maps to be corrected by calculating just one coefficient of friction correction factor, and enables the reliability of the corrected default value of the coefficient of friction to be ensured.