Lockup Clutch Control for Torque Converter Deceleration
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Solution Overview
Problem
Automatic transmissions with torque converters experience reduced fuel efficiency due to slippage between the engine and transmission, and abrupt deceleration conditions lead to unnecessary fuel consumption and uncomfortable 'shock' when the lockup clutch slips, necessitating a method to synchronize engine and transmission shafts without causing shock.
Innovation Solution
A method that senses deceleration states, applies a first compressive lockup force to rapidly synchronize engine and transmission shafts, then transitions to a second lower force to maintain synchronization, minimizing fuel supply delay and shock, by establishing frictional engagement between mating surfaces in a torque converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the lockup clutch pressure is elevated to peak pressure to synchronize engine and transmission shafts during deceleration, then fuel efficiency is improved by reducing fuel supply delay, but shock is caused to vehicle occupants
Solution Approach 1:
The lockup clutch pressure is dynamically adjusted through a two-stage process: first elevated to peak pressure to rapidly synchronize shafts and enable fuel termination, then reduced to a lower maintenance pressure to prevent shock. This dynamic pressure modulation resolves the contradiction between achieving quick synchronization for fuel efficiency and avoiding uncomfortable shock to occupants.
Solution Approach 2:
The lockup clutch pressure application occurs in periodic stages: an initial peak pressure phase for rapid synchronization, followed by a reduction to maintenance pressure. This periodic action pattern allows the system to achieve the beneficial effect of quick fuel termination while mitigating the harmful shock effect through the pressure reduction phase.
2Object-affected harmful factors
If the lockup clutch pressure is kept constant during deceleration, then shock is minimized, but fuel supply delay is prolonged worsening fuel efficiency
Solution Approach 1:
Instead of maintaining constant pressure, the system dynamically adjusts lockup clutch pressure in two stages: initially keeping it constant or low to avoid shock, then elevating to peak pressure when synchronization is achieved to terminate fuel supply promptly. This dynamic adjustment resolves the contradiction between minimizing shock and improving fuel efficiency.
3Use of energy by moving object
If the lockup clutch is engaged to directly connect engine output shaft to transmission input shaft, then fuel efficiency is improved by eliminating slippage, but slippage occurs during abrupt deceleration causing fuel waste
Solution Approach 1:
The system applies preliminary anti-action by detecting deceleration conditions and proactively managing lockup clutch engagement. When deceleration is detected, the system first elevates lockup clutch pressure to ensure reliable synchronization before attempting fuel termination, preventing the harmful effect of slippage-induced fuel waste while maintaining the benefit of reduced slippage during normal operation.
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 reduces fuel consumption and minimizes the shock experienced by vehicle occupants during deceleration, enhancing fuel efficiency and ride comfort by ensuring synchronized rotation of engine and transmission shafts.
Implementation Method 1
Frictional engagement is to be established between mating surfaces in cooperation with the engine output shaft and the transmission input shaft
Data Source
AI summary
A method of controlling a reduction of an amount of fuel supplied to an engine provided to a motor vehicle with an automatic transmission separated from the engine by a torque converter is provided. The method includes the step of sensing commencement of a deceleration state during which an amount of the fuel supplied to the engine is to be reduced to an amount that is less than an amount of fuel being delivered to the engine immediately prior to the deceleration state. Whether synchronization of an engine output shaft and a transmission input shaft is appropriate under the deceleration stat is also to be determined. Frictional engagement is to be established between mating surfaces in cooperation with the engine output shaft and the transmission input shaft, and a first compressive lockup force is to be established between the mating surfaces during a first time period to urge synchronization of the engine output shaft and the transmission input shaft, wherein the first time period ends before said synchronization is accomplished. A second compressive lockup force is also to be established between the mating surfaces during a second time period after the first time period and before synchronization is achieved, wherein the second compressive lockup force is less than the first lockup force but sufficient to urge synchronization of the engine output shaft and the transmission input shaft.