CVT Clamping Force Control via Wheel Speed Difference Sensing
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Solution Overview
Problem
Existing control devices for continuously variable transmissions (CVTs) face delays in judging road surface conditions, leading to belt slippage due to response delays in increasing clamping force, especially on surfaces with varying friction coefficients.
Innovation Solution
A control device that uses a combination of wheel speed difference sensors between driving and driven wheels to immediately increase clamping force when a predetermined speed difference is reached, along with vehicle speed vibration components to enhance judgment accuracy and reduce slippage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If band-pass filter processing and time total integration are performed to judge road surface state, then judgment accuracy is improved, but response time increases causing control delay
Solution Approach 1:
The patent extracts only the necessary information (wheel speed difference) needed to detect rough road conditions, eliminating the need for complex band-pass filter processing and time total integration. This allows immediate detection of wheel slip conditions without computational delays while maintaining sufficient accuracy for control purposes.
Solution Approach 2:
The control device continuously monitors wheel speed difference in advance, so when wheel slip occurs on a rough road, the system is already prepared to immediately increase clamping force without any detection delay. The preliminary monitoring of wheel speed difference enables instant response to changing road conditions.
2Reliability
If clamping force is increased to prevent belt slippage, then transmission reliability is improved, but energy consumption increases
Solution Approach 1:
The clamping force is dynamically adjusted based on actual wheel slip conditions rather than being continuously high. The hydraulic control system increases clamping force only when wheel speed difference indicates wheel slip, and reduces it when conditions normalize, optimizing the balance between preventing belt slippage and minimizing energy consumption.
Solution Approach 2:
The system uses feedback from wheel speed difference sensing to control clamping force application. When the sensed wheel speed difference exceeds a threshold indicating wheel slip, the control device increases clamping force; when the difference returns to normal, clamping force is reduced. This feedback mechanism ensures reliable transmission only when necessary, reducing unnecessary energy consumption.
Data Source
AI summary
A control device for a continuously variable transmission includes a wheel speed difference sensing section configured to sense a wheel speed difference between the driving wheel and the driven wheel from a detection value of the first rotation speed sensor and a detection value of the second rotation speed sensor; and a clamping force increasing section configured to increase a clamping force for sandwiching a belt of the continuously variable transmission by a pulley when the wheel speed difference becomes equal to or greater than a first predetermined value, relative to a case where the wheel speed difference is smaller than the first predetermined value.