Automatic Transmission Shift Control for Fuel-Efficient Coasting
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Solution Overview
Problem
Existing methods for controlling shift points in automatic transmissions often result in unnecessary fuel consumption during deceleration, as they deactivate fuel-saving throttle cut-off, leading to inefficient fuel usage.
Innovation Solution
An electronic control device in the automatic transmission system receives performance requirement and vehicle speed inputs to trigger shifts using characteristic curves, defining a speed range for instantaneous down-shifts and delaying subsequent up-shifts to enable an unfueled coasting mode, thereby reducing fuel consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the shift point is controlled using characteristic curves with hysteresis, then rapid shifting between gears is avoided, but fuel-saving throttle cut-off is deactivated during deceleration, leading to unnecessary fuel consumption
Solution Approach 1:
The patent applies dynamics by making the shift point control adaptive rather than static. The control device dynamically adjusts the shift behavior based on the current gear state and deceleration conditions. When downshifting is detected during deceleration, the system dynamically delays the subsequent upshift timing, creating a flexible control strategy that responds to real-time operating conditions rather than following fixed characteristic curves throughout.
Solution Approach 2:
The patent implements preliminary action by proactively delaying the upshift timing before the vehicle completes its deceleration phase. The control device predicts that an upshift would soon be triggered by the characteristic curves and preemptively delays it, ensuring the engine remains in the coasting region longer. This preliminary intervention prevents the automatic reactivation of fuel injection that would otherwise occur when the shift point is reached during natural deceleration.
2Ease of operation
If the shift point is lowered during deceleration, then the transmission responds to speed changes, but the unfueled throttle cut-off is deactivated, increasing fuel consumption
Solution Approach 1:
The patent employs feedback by continuously monitoring the actual gear state and using it to modulate the shift control. The control device receives feedback about whether the transmission is currently downshifted and uses this information to determine whether to apply the upshift delay. This feedback loop ensures that the delay is applied selectively only when appropriate (when a downshift has occurred during deceleration) and not during normal operation, maintaining transmission responsiveness while reducing fuel consumption.
Solution Approach 2:
The patent applies parameter changes by modifying the timing parameter of the upshift operation. Instead of changing the shift point speed threshold, the system changes the time parameter by introducing a delay period after downshift detection. This temporal parameter adjustment allows the engine to remain in the high-RPM coasting region longer, maintaining the benefits of speed-responsive shifting while extending the unfueled operating condition to reduce overall fuel consumption.
Data Source
AI summary
The method according to the invention for shift point control in automatic transmissions by means of an electronic control device, which receives a performance requirement value and the vehicle speed as input signals and triggers up-shifts and down-shifts, by means of a functional module. The functional module controls the shift point, by using characteristic shift curves stored in the control device as a function of the performance requirement value and the vehicle speed. When predetermined operating conditions apply, a speed range is defined below a defined vehicle speed, in which range an instantaneous down-shift is performed, which is independent of the currently applicable characteristic shift curve. As soon as the performance requirement value or an operating value proportional to the performance requirement value falls below a threshold, an up-shift subsequent to the down-shift is delayed by a first predetermined time period after the instantaneous down-shift.