CVT Belt Abnormality Detection Using Gear Ratio Feedback
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Solution Overview
Problem
Existing vehicular continuously variable transmission systems face challenges in accurately determining belt abnormalities, such as stretching or missing rings, due to variations in gear ratio caused by input torque and hydraulic pressure, leading to unreliable condition assessment.
Innovation Solution
A vehicular continuously variable transmission system that includes a target gear ratio setting unit, gear ratio control unit, hydraulic pressure detecting unit, rotation speed detecting units, and a condition determination unit to calculate and compare actual and reference gear ratios, determining belt conditions by assessing the drive pulley hydraulic pressure and rotation speeds, allowing for accurate detection of belt abnormalities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gear ratio is determined based on command signal alone, then the abnormality detection is simple, but the detection accuracy is insufficient due to variations in input torque and hydraulic pressure
Solution Approach 1:
The system calculates actual gear ratio from detected rotation speeds of drive and driven pulleys, then compares it with command gear ratio to detect abnormalities. This feedback mechanism continuously monitors the discrepancy between expected and actual gear ratios, enabling accurate abnormality detection while accounting for variations in input torque and hydraulic pressure
Solution Approach 2:
The patent introduces an actual gear ratio calculation unit that serves as an intermediary between the command signal and abnormality determination. By calculating the actual gear ratio from rotation speed sensors and comparing it with the commanded gear ratio, the system creates an intermediate verification step that improves detection accuracy without requiring direct modification of the belt or pulley structure
2Reliability
If the belt type continuously variable transmission is determined to be abnormal when actual gear ratio exceeds maximum speed-increasing state gear ratio, then abnormality detection is straightforward, but false positives occur due to gear ratio variations from torque and hydraulic pressure changes
Solution Approach 1:
The system dynamically adjusts the abnormality determination criteria by calculating the actual gear ratio in real-time based on detected rotation speeds. Instead of using a fixed threshold, the system continuously compares the dynamically calculated actual gear ratio with the command gear ratio, allowing reliable abnormality detection that adapts to varying operating conditions including changes in input torque and hydraulic pressure
Data Source
AI summary
A belt-type continuously variable transmission includes an actual gear ratio calculation unit for calculating an actual gear ratio based on the rotation speed of a drive pulley and the rotation speed of a driven pulley, a reference gear ratio calculation unit for calculating a reference gear ratio by modifying the actual gear ratio based on an input torque and a driven pulley hydraulic pressure, and a condition determination unit for, in a case where the target gear ratio is an overdrive gear ratio, determining that at least part of rings of a belt is missing when the reference gear ratio is greater than or equal to a predetermined gear ratio and a drive pulley hydraulic pressure is greater than or equal to a predetermined hydraulic pressure.