CVT Control High Setting for Shift Response
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In continuously variable transmissions (CVT), setting the target speed ratio to mechanical High leads to prolonged shift times during downshifting due to excessive primary pressure accumulation, as the actual speed ratio fluctuates around the target, causing repeated corrections that delay the shift process.
Innovation Solution
Implementing a control method that sets a control High lower than the mechanical High by a predetermined amount, allowing the actual speed ratio to fluctuate within a defined range, thereby preventing excessive primary pressure accumulation and enabling quicker downshifting by expanding the speed ratio range to the control High.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the target speed ratio is set at the mechanical High to improve fuel economy, then the speed ratio range is enlarged and fuel economy is improved, but the actual speed ratio fluctuates about the target speed ratio causing repeated corrections to increase primary pressure which makes the primary pressure excessively larger and delays downshifting
Solution Approach 1:
The patent applies preliminary anti-action by preemptively limiting the primary pressure increase through feedback operation amount accumulation before excessive pressure buildup occurs. The control system monitors the feedback operation amount and suppresses primary pressure correction when it exceeds the predetermined threshold, preventing the harmful effect of excessively large primary pressure that would delay downshifting.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the feedback operation amount accumulated from speed ratio deviations and using this information to modulate primary pressure corrections. The feedback mechanism compares the accumulated operation amount against a predetermined threshold and adjusts primary pressure accordingly, ensuring the actual speed ratio remains within acceptable fluctuation ranges without causing excessive pressure buildup.
2Productivity
If speed ratio feedback control is executed with target speed ratio at mechanical High, then the speed ratio range is expanded to improve fuel economy, but the primary pressure becomes excessively larger than proper value and it takes time to lower the primary pressure to start downshift
Solution Approach 1:
The patent uses feedback control to monitor the feedback operation amount accumulated from deviations between actual and target speed ratios. When the accumulated feedback operation amount reaches a predetermined threshold, the system modulates primary pressure corrections to prevent excessive pressure buildup, thereby managing the complexity of primary pressure control while maintaining expanded speed ratio range.
Solution Approach 2:
The patent changes the control parameter from directly controlling primary pressure to controlling the feedback operation amount accumulation. By monitoring and limiting the feedback operation amount rather than directly adjusting primary pressure, the system simplifies the control mechanism while maintaining the ability to manage primary pressure within appropriate ranges for the expanded speed ratio operation.
3Stability of the object's composition
If the correction to increase primary pressure is repeatedly performed to maintain target speed ratio, then the target speed ratio is maintained, but the primary pressure becomes excessively larger than proper value and shift responsiveness deteriorates
Solution Approach 1:
The patent implements feedback control by accumulating feedback operation amounts from speed ratio deviations and using this accumulated information to modulate primary pressure corrections. When the feedback operation amount reaches a predetermined threshold, the system limits further primary pressure increases, thereby maintaining target speed ratio stability while preventing excessive pressure buildup that would harm shift responsiveness.
Solution Approach 2:
The patent applies partial action by not fully correcting every speed ratio deviation with primary pressure adjustment. Instead of repeatedly performing full corrections that would cause excessive pressure buildup, the system selectively applies corrections based on the accumulated feedback operation amount threshold, achieving adequate speed ratio stability without over-correcting and compromising shift responsiveness.
Data Source
AI summary
A transmission controller searches a mechanical High, which is a minimum value of a possible speed ratio of the continuously variable transmission (CVT), based on an actual speed ratio, sets a control High lower than the mechanical High by a predetermined amount, and controls a speed ratio of the CVT by setting a minimum value of a speed ratio range of the CVT at the control High.