Lockup Torque Converter Control for Deceleration Surge
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
When a vehicle with a continuously-variable-ratio transmission (CVT) and lock-up torque converter transitions from deceleration to acceleration, the sudden change in engine torque can cause an undesirable sensation of 'surge' or 'bump' due to the torque converter remaining in a locked or partially-locked state.
Innovation Solution
A method and code that delay the resumption of fuel flow to the engine after deceleration, using a fuel recovery delay timer and breakout conditions to ensure the torque converter is unlocked, thereby avoiding the 'bump' by monitoring powertrain demand signals, torque converter state, and engine speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the torque converter remains in the locked state during vehicle deceleration to achieve smooth deceleration, then the deceleration smoothness is improved, but when fuel flow is resumed with the torque converter still locked, an undesirable surge or bump sensation occurs
Solution Approach 1:
The control system performs preliminary action by detecting when the torque converter is in a locked state during deceleration and delays the resumption of fuel flow until the torque converter unlocks. This anticipatory control prevents the surge or bump sensation that would occur if fuel flow were restored while the torque converter remained locked, thereby eliminating the harmful effect without compromising deceleration smoothness.
2Loss of energy
If fuel flow to the engine is shut off during deceleration to maximize fuel economy, then fuel economy is improved, but the engine torque becomes insufficient to maintain proper engine speed
Solution Approach 1:
The control system employs feedback by continuously monitoring engine speed and other operating parameters during deceleration. Based on this feedback, the system determines the optimal timing to resume fuel flow - specifically when the torque converter unlocks and can no longer effectively transmit torque. This feedback-controlled approach ensures fuel flow is restored at the precise moment needed to maintain engine speed, maximizing fuel economy while preventing engine speed loss.
Data Source
AI summary
A method of controlling a vehicle powertrain having an automatic transmission coupled to an engine through a lock-up torque converter includes determining when a torque converter unlock is imminent during a deceleration fuel shut-off event, and delaying the resumption of fuel flow to the engine for a calibratable time period to reduce the likelihood of an undesirable increase in engine output torque when the torque converter has not fully transitioned to an unlocked state. The method also includes determining whether one or more breakout conditions exist that require enabling fuel flow to the engine and, perhaps, triggering an active unlocking of the lock-up torque converter.