Sailing Stop Control Timing for Faster Vehicle Shift Response
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Solution Overview
Problem
Existing vehicle systems face delays in shifting from coast-travel to normal travel due to the inability to restart the engine efficiently when the sailing quitting condition is satisfied during engine automatic stop, leading to a delayed response.
Innovation Solution
A sailing stop control method and device that uses a frictional engagement element and a starter motor to delay the rotation stop timing of the transmission relative to the engine stop timing, allowing for early reengagement of the frictional engagement element when the input and output rotation speeds synchronize after engine restart, thereby reducing the load on the engine and improving shift response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engine rotation speed is reduced to a low rotation speed region before engine restart, then the engine can be restarted by the starter motor, but the shift response from coast-travel to normal travel is delayed
Solution Approach 1:
The frictional engagement element is reengaged preliminarily before the engine rotation speed reaches the synchronization rotation speed. This preliminary action allows the transmission rotation speed to be maintained at a higher level, enabling faster engine restart while avoiding the delay caused by waiting for rotation speed synchronization.
Solution Approach 2:
The system buffers the rotation speed difference between the engine and transmission by maintaining the frictional engagement element in the engaged state during the engine restart process. This cushioning effect allows the engine rotation speed to increase rapidly without causing excessive load on the engine, enabling the rotation speeds to synchronize quickly after restart.
2Loss of time
If the frictional engagement element is reengaged immediately after engine restart, then the shift response is improved, but the load on the engine increases
Solution Approach 1:
The system changes the operational parameters of the frictional engagement element by controlling its reengagement timing based on rotation speed synchronization rather than immediate reengagement. This parameter change allows the engine to restart with reduced load while maintaining fast shift response through the preliminary engagement strategy.
3Loss of time
If the engine rotation speed is maintained at a high rotation speed region, then the shift response is improved, but the engine cannot be restarted by the starter motor
Solution Approach 1:
The system dynamically adjusts the engine rotation speed by controlling the disengagement and reengagement timing of the frictional engagement element. The engine rotation speed is allowed to increase to a high level during coast-travel, then rapidly reduced when the frictional engagement element is reengaged, enabling both fast shift response and reliable engine restart.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the shift response from coast-travel to normal travel by ensuring a faster engine rotation speed increase and stable reengagement of the frictional engagement element, reducing driver discomfort and improving fuel efficiency.
Implementation Method 1
a starter motor that starts the engine
Implementation Method 2
a frictional engagement element that is disposed in series between an engine and a driving wheel
Data Source
AI summary
Variator (20) and forward clutch (Fwd/C) disposed in series are provided between engine (1) having starter motor (15) and driving wheel (7). Sailing stop control that, on the basis of satisfaction of sailing entering condition, interrupts power transmission by frictional engagement element (Fwd/C), stops engine (1) and performs coast-travel is performed. When sailing entering condition is satisfied, coast-travel is started with rotation stop timing of variator (20) being delayed with respect to rotation stop timing of engine (1). When accelerator pedal depression operation intervenes after start of coast-travel, engine (1) is restarted by starter motor (15). When judged that input and output rotation speeds of frictional engagement element (Fwd/C) become synchronization rotation speed after restart of engine (1), frictional engagement element (Fwd/C) is reengaged. Shift response from coast-travel to normal travel is therefore improved at change-of-mind at which sailing quitting condition is satisfied during progress of automatic stop of engine.