CVT Line Pressure Control via Throttle Deviation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing continuously variable transmission systems experience increased step motor control deviation and unnecessary line pressure adjustments when engine torque varies dramatically, leading to decreased fuel economy due to premature learning error determinations.
Innovation Solution
A continuously variable transmission system with a controller that calculates control deviations and prohibits learning error updates for a predetermined time period when the primary pulley input torque varies beyond specific ranges, ensuring accurate determination of operating position updates and controlling line pressure based on reference and actual operating positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the learned value is recalculated and updated when the step motor control deviation is large, then the line pressure can be corrected to prevent insufficient pressure, but the line pressure remains high for an extended period causing deterioration in fuel economy
Solution Approach 1:
The patent changes the parameter for determining when to update the learned value from step motor control deviation alone to a combination of throttle position change amount and step motor control deviation. By introducing the throttle position change amount as an additional parameter, the system can distinguish between deviations caused by actual attachment errors versus those caused by normal throttle variations, thereby updating the learned value only when necessary and maintaining optimal line pressure to improve fuel economy.
2Reliability
If the line pressure is raised to prevent insufficient pressure during learned value recalculation, then the reliability of pressure control is improved, but the fuel economy deteriorates due to continuous high pressure
Solution Approach 1:
The patent implements periodic updating of the learned value based on specific conditions (throttle position change amount exceeding a threshold combined with large step motor control deviation) rather than continuous updating. This periodic action allows the line pressure to be maintained at optimal levels between updates, preventing unnecessary energy loss while ensuring reliability when actual attachment errors occur.
3Speed
If the learning error determination is made based on large step motor control deviation, then the system responds to potential errors quickly, but false determinations occur during dramatic engine torque variations reducing control precision
Solution Approach 1:
The patent introduces the throttle position change amount as an intermediary parameter that mediates between the step motor control deviation and the learning error determination. This intermediary helps distinguish whether a large control deviation is caused by actual learning errors or by normal engine operation variations, thereby improving the accuracy of error determination while maintaining quick response to actual problems.
Data Source
AI summary
When a line pressure PL serving as a source pressure of a primary pulley (2) and a secondary pulley (3) is controlled on the basis of a control deviation ΔStep, which is the deviation between a step count StepMdl of a step motor (27) corresponding to a target speed ratio I (o) and a value obtained by adding a target deviation GTstep and a starting learned value Gstep to a step count Bstep of the step motor (27) corresponding to an actual speed ratio ip, the engine torque varies dramatically beyond the range of a predetermined value T1 and a predetermined value T2 during a predetermined time period t1, a learning error determination relating to the starting learned value Gstep is prohibited for a predetermined time period t2.