CVT Clamping Force Correction via Lubricant Temperature Estimation
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Solution Overview
Problem
The temperature variation of lubricant between the input-side and output-side elements in a stepless transmission leads to inconsistent clamping force correction, resulting in decreased power transmission efficiency due to varying friction coefficients, which is not adequately addressed in existing control devices.
Innovation Solution
A control device with a clamping force correction unit that utilizes both pre-supply and drain oil temperature sensors to estimate the lubricant temperature, adjusting the clamping force based on the detected temperatures to maintain optimal friction coefficients for efficient power transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If clamping force is corrected based on lubricant temperature, then power transmission efficiency is improved, but measurement precision deteriorates due to temperature variation at different measurement locations
Solution Approach 1:
The patent introduces an intermediary estimation process that uses both pre-supply temperature (measured before oil enters the friction zone) and drain temperature (measured after oil leaves the friction zone) to calculate an estimated lubricant temperature. This estimated temperature serves as a mediator that represents the actual lubricant condition more accurately than either single measurement point, thereby resolving the measurement precision issue while maintaining the ability to correct clamping force for optimal power transmission efficiency.
2Device complexity
If single temperature measurement point is used, then device complexity is reduced, but reliability deteriorates due to inconsistent clamping force correction
Solution Approach 1:
The patent segments the temperature measurement system into two distinct measurement points: pre-supply temperature measurement and drain temperature measurement. Each sensor is positioned at a specific location to capture temperature characteristics at different stages of the lubricant cycle. This segmentation allows the system to obtain more comprehensive temperature information without creating a single complex measurement system, thereby improving correction reliability while managing device complexity through modular sensor placement.
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 solution ensures efficient power transmission by accurately correcting the clamping force based on the lubricant's temperature, maintaining optimal friction coefficients and preventing efficiency losses across different temperature conditions.
Implementation Method 1
power is transmitted between each of the input-side element and the output-side element and the transmission element with a lubricant being interposed between each of the input-side element and the output-side element and the transmission element
Implementation Method 2
the temperature of the lubricant increases due to friction between each of the input-side element and the output-side element and the transmission element
Data Source
AI summary
A control device includes: a clamping force determination unit that determines a clamping force Fs so that a transmission gear ratio R of a stepless transmission is a target transmission gear ratio; a correction unit that corrects the clamping force Fs determined by the clamping force determination unit, based on an oil temperature TO of a lubricant interposed between each of pulleys and a belt and the transmission gear ratio R; and a clamping force control unit that controls clamping of the pulleys and to be performed with the clamping force Fs corrected by the correction unit.