CVT Downshift Restriction via Accelerator Speed
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Solution Overview
Problem
Continuously variable transmissions (CVTs) in vehicles experience unnatural driving feelings due to rapid downshifts during minor accelerator operations, leading to slippage and noise, which affects the driver's perception of engine speed and overall driving experience.
Innovation Solution
A shift control apparatus for CVTs that includes a target transmission gear ratio setting section, a shift control section, and a downshift restricting section. The downshift restricting section judges whether to restrict downshifts based on the variation amount of the accelerator opening degree and depression speed, masking the accelerator opening degree variation when necessary to prevent linear shifts and maintain a consistent engine speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the downshift is performed linearly with respect to accelerator operation, then the transmission can rapidly attain appropriate gear ratio for power performance, but the driver feels slippage and noise causing unnatural driving feeling
Solution Approach 1:
The patent changes the control parameters by introducing accelerator depression speed and variation amount thresholds. When these parameters exceed thresholds, the system switches from linear shift control to restricted downshift control, thereby adjusting the transmission behavior to eliminate unnatural driving feelings while maintaining rapid response capability
Solution Approach 2:
The system continuously monitors accelerator depression speed and variation amount, using this feedback to dynamically adjust downshift behavior. When feedback indicates excessive depression speed or variation, the system restricts downshift to prevent slippage and noise, thus resolving the contradiction between rapid response and natural driving feeling
2Speed
If the target transmission gear ratio is set based on shifted accelerator opening degree, then the shift is performed rapidly, but the engine speed increases excessively causing slippage feeling
Solution Approach 1:
The system takes preliminary anti-action by detecting excessive accelerator depression speed or variation amount before the downshift is executed. When these conditions are detected, the system preemptively restricts the downshift to prevent excessive engine speed increase, thereby eliminating slippage feeling while maintaining rapid shift capability
Data Source
AI summary
A shift control apparatus for a continuously variable transmission includes: a target transmission gear ratio setting section configured to set a target transmission gear ratio with reference to a map based on an accelerator opening degree and a vehicle speed; a shift control section configured to control a shift of the continuously variable transmission based on the target transmission gear ratio; and a downshift restricting section configured to judge whether or not a restriction of the downshift is needed based on at least one of a variation amount of the accelerator opening degree and an accelerator depression speed, and to perform the restriction of the downshift when the downshift restricting section judges that the restriction of the downshift is needed, irrespective of a variation of the accelerator opening degree inputted to the target transmission gear ratio setting section.