Automatic Transmission Multiple Downshifting Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Multi-speed automatic transmissions face challenges in minimizing wear and energy consumption due to increased friction and engagement cycles, while maintaining predetermined shift sequences and avoiding disturbances during downshifting, which can lead to lag in ideal speed ratio selection and increased fuel consumption.
Innovation Solution
Implementing a method that allows multiple downshifting, such as double downshifting, by temporarily inhibiting upshifts and skipping intermediate ratios, which reduces wear and energy expenditure, and is controlled by predetermined conditions like accelerator pedal position, braking, and vehicle mode, using an electronic control unit to manage these conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sequential downshifting through all intermediate speed ratios is commanded, then the transmission follows a predetermined shift sequence, but the shift time increases and the selected speed ratio lags behind the ideal speed ratio
Solution Approach 1:
The patent applies skipping by allowing the transmission to bypass intermediate speed ratios during downshifting when specific conditions are met. Instead of sequentially engaging each intermediate ratio, the system can skip directly to the target lower ratio, thereby reducing shift time and preventing lag behind the ideal speed ratio while still maintaining reliability through conditional control logic
2Adaptability or versatility
If multiple engagement and disengagement cycles are executed to accommodate many speed ratios, then the transmission provides more individually selectable speed ratios, but wear of friction material increases
Solution Approach 1:
The patent merges adjacent speed ratios into broader ratio ranges that can be covered by fewer clutch and brake engagements. By consolidating the control strategy to engage fewer friction elements for longer duration, the system maintains adaptability across multiple speed ratios while significantly reducing the number of engagement cycles and corresponding friction material wear
3Adaptability or versatility
If multiple engagement and disengagement cycles are executed, then the transmission accommodates more speed ratios, but energy consumption increases
Solution Approach 1:
The patent merges adjacent speed ratios into broader ranges that require fewer hydraulic pressure generation cycles. By consolidating the control strategy to engage fewer friction elements for longer duration, the system maintains adaptability across multiple speed ratios while significantly reducing the number of engagement cycles and corresponding energy consumption
4Reliability
If sequential downshifting is commanded, then the transmission follows a predetermined shift sequence, but disturbances are generated noticeable to vehicle occupants
Solution Approach 1:
The patent applies skipping by allowing the transmission to bypass intermediate speed ratios during downshifting when specific conditions are met. Instead of sequentially engaging each intermediate ratio, the system can skip directly to the target lower ratio, thereby reducing shift time and preventing lag behind the ideal speed ratio while still maintaining reliability through conditional control logic
Data Source
AI summary
A multi-speed automatic vehicle transmission has an electronic control unit which permits multiple downshifts if certain conditions are satisfied. Such downshifts are direct and omit engagement and disengagement of one or more intermediate speed ratios. Multiple downshifting may allow the actual speed ratio to better match the ideal speed ratio, for example under heavy braking.