Automatic Gear Shift Control for Extended Fuel Cut During Deceleration
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Solution Overview
Problem
Existing automatic transmission control methods fail to extend the fuel cut period during sudden vehicle deceleration, leading to premature termination of fuel cut and lockup states, which negatively impacts fuel economy.
Innovation Solution
Implementing a plural stage downshift strategy where the automatic transmission shifts to a target gear stage smaller than the current stage by two or more, using a combination of continuous and stage skip downshifts to maintain engine speed above the lockup release rotation speed, thereby prolonging the fuel cut period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If sequential downshift is performed one stage at a time to extend fuel cut period, then fuel economy is improved, but during sudden deceleration the engine speed drops below lockup release rotation speed causing fuel cut termination
Solution Approach 1:
The patent applies skipping by performing plural stage downshifts that skip intermediate gear stages. When sudden deceleration is detected, the control device commands downshifts of two or more stages at once rather than sequential single-stage downshifts, allowing the engine speed to be maintained above the lockup release rotation speed threshold and preventing premature termination of the fuel cut state.
Solution Approach 2:
The patent implements dynamic adjustment of downshift strategy based on deceleration magnitude. The control device monitors vehicle deceleration and selectively applies either single-stage or plural-stage downshifts depending on whether the deceleration exceeds a predetermined threshold, optimizing the balance between fuel economy and maintaining fuel cut reliability under varying driving conditions.
2Duration of action of moving object
If plural stage downshift is performed to maintain engine speed during sudden deceleration, then fuel cut period is extended, but transmission control complexity increases
Solution Approach 1:
The control device automatically selects and executes the appropriate downshift strategy (single-stage or plural-stage) based on real-time monitoring of vehicle deceleration and engine speed parameters. The system self-adjusts without requiring manual intervention or complex external control, using predetermined thresholds and algorithms to determine when plural stage downshifts are necessary to maintain fuel cut conditions.
Solution Approach 2:
The patent changes the downshift control parameters dynamically based on operating conditions. By adjusting the downshift stage increment from 1 to 2 or more stages based on deceleration magnitude, the system optimizes fuel cut duration while managing control complexity through conditional parameter modification rather than fixed control logic.
3Reliability
If downshift is commanded with margin for engine speed decrease during inertia phase, then lockup can be maintained, but response time to sudden deceleration is delayed
Solution Approach 1:
The control device performs preliminary detection of sudden deceleration conditions and proactively commands plural stage downshifts before the engine speed drops to critical levels. By anticipating the need for larger downshift increments when high deceleration is detected, the system maintains lockup and fuel cut states without waiting for engine speed to approach the release threshold, thereby improving response speed while maintaining reliability.
Data Source
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AI summary
A gear change control means comprises: a deceleration state-determining section (10d) for determining whether the deceleration of a vehicle is in a gradual deceleration state or a rapid deceleration state; and a downshift control section (10c) for giving a single-gear downshift command for downshifting from the current gear to the next gear, which is one gear lower than the current gear, when the vehicle is determined to be in a gradual deceleration state, and for giving a multiple-gear downshift command for downshifting from the current gear of the automatic gear change mechanism to a target gear that is at least two gears lower than the current gear when the vehicle is determined to be in a gradual deceleration state.