CVT Control Device Preventing Low Separation Shock
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Solution Overview
Problem
Conventional control devices for continuously variable transmissions with auxiliary mechanisms experience 'Low separation shock' during depression shift control, leading to unnatural driver feedback due to overshot transmission gear ratios and reduced drivability.
Innovation Solution
A control device that includes cooperative and non-cooperative control mechanisms, where the variator's target transmission gear ratio is set to a higher restriction value when the actual gear ratio exceeds the control limit, allowing the variator to shift slower than the auxiliary transmission, thereby preventing overshoot and minimizing gear ratio deviation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the variator shifts at high speed to rapidly attain the target transmission gear ratio during depression shift control, then the response speed is improved, but the transmission gear ratio is overshot causing Low separation shock
Solution Approach 1:
The control device determines in advance whether the variator transmission gear ratio is higher than a predetermined value before initiating the depression shift control. Based on this preliminary determination, it adjusts the target transmission gear ratio setting strategy, preventing overshoot by anticipating the shift behavior and preparing appropriate control parameters in advance.
Solution Approach 2:
The control device continuously monitors the actual transmission gear ratio of the variator during the shift process and compares it with the target transmission gear ratio. Based on this feedback, it dynamically adjusts the target transmission gear ratio setting to prevent overshoot, ensuring the actual ratio converges smoothly to the desired value without causing Low separation shock.
2Productivity
If the variator shifts to the lowest transmission gear ratio during depression downshift control, then the transmission response is improved, but the Low separation shock is generated reducing drivability
Solution Approach 1:
The control device takes preliminary anti-action by determining whether the variator transmission gear ratio exceeds a predetermined value before the depression shift control is executed. When this condition is met, it prevents the variator from shifting to the lowest transmission gear ratio, thereby counteracting the potential generation of Low separation shock before it occurs and maintaining smooth drivability.
Solution Approach 2:
The control device uses feedback from the actual transmission gear ratio measurement to dynamically adjust the target transmission gear ratio. When the feedback indicates that shifting to the lowest gear ratio would cause overshoot and Low separation shock, the control device modifies the target ratio to prevent this adverse effect, ensuring both rapid response and smooth operation.
Data Source
AI summary
A control device for a continuously variable transmission with an auxiliary transmission includes: a cooperative control section; and a depression shift control section, wherein when an actual transmission gear ratio of the variator at the judgment of the depression shift control is higher than a first transmission gear ratio set as a lowest value of a control of the transmission gear ratio, the depression shift control section configured to downshift the variator, and to set a target transmission gear ratio at the shift of the variator to a second transmission gear ratio which is a restriction value that is higher than the first transmission gear ratio.