Torque Converter Lock-up Clutch Control with Differential Pressure Learning
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Solution Overview
Problem
Existing lock-up clutch control systems in torque converters face challenges with differential pressure scatter due to individual differences and time-dependent variations, leading to inconsistent engagement timing and increased fuel consumption, especially during coasting or low throttle conditions.
Innovation Solution
A lock-up clutch control device that includes a differential pressure generating device, input torque detection, and a controller to compute and correct differential pressure command values based on real-time input torque and oil temperature variations, allowing for rapid learning and precise engagement timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If learning control is performed by decreasing differential pressure until small slip occurs during coasting, then engagement timing deviation is corrected, but learning takes excessive time and is not appropriate unless coasting continues for long time
Solution Approach 1:
The system performs preliminary action by detecting input torque before engagement and using it to directly calculate the real differential pressure. This allows the learning value to be computed in advance based on torque information, eliminating the need to wait for prolonged coasting periods or gradual pressure decrease to observe slip behavior.
2Reliability
If real differential pressure is larger than command value due to scatter, then engagement timing is advanced, but engine rotation speed rapidly decreases causing shock and driver discomfort
Solution Approach 1:
The system implements feedback by detecting the actual input torque during engagement, calculating the real differential pressure from this torque information, comparing it with the command value, and storing the difference as a learning value. This feedback loop continuously corrects the differential pressure command value to compensate for scatter, ensuring consistent engagement timing and preventing harmful effects like shock and driver discomfort.
3Reliability
If real differential pressure is smaller than command value due to scatter, then lock-up completion takes long time, but fuel consumption rate is impaired
Solution Approach 1:
The feedback mechanism detects torque-based real differential pressure, compares it with command value, and adjusts the command value using stored learning values. This ensures the lock-up clutch engages at the appropriate pressure level without delay, preventing prolonged engagement times that would impair fuel consumption rate while maintaining consistent timing.
4Ease of operation
If differential pressure command value is not corrected for oil temperature variation, then smooth lock-up cannot be achieved at low throttle opening, but correction mechanism increases control complexity
Solution Approach 1:
The system uses feedback to detect the actual differential pressure through input torque measurement and calculates the deviation from the command value. The learning value stored from this deviation automatically compensates for oil temperature variations and other scatter effects, enabling smooth lock-up across different operating conditions without requiring complex separate correction mechanisms for each variable.
Data Source
AI summary
A lock-up clutch control device which controls a lock-up clutch provided in a torque converter installed between an engine and a transmission, is disclosed. The lock-up clutch control device changes over between a converter state and a lock-up state of the torque converter according to a differential pressure command value (LUprs) relating to a differential pressure supplied to the lock-up clutch. The lock-up clutch control device includes a differential pressure generating device (7, 8) which generates the differential pressure supplied to the lock-up clutch; input torque detection means (2, 14, 15) which detects an input torque (Te) to the torque converter; and a controller (1). The controller (1) is programmed to compute a real differential pressure (P_lu) based on the detected input torque (Te) upon completion of the engagement of the lock-up clutch; compute a learning value (P_learn(Tai)) relating to a differential pressure deviation, based on the difference between the computed real differential pressure (P_lu) and differential pressure command value (P_ref) upon completion of the engagement of the lock-up clutch, and store the learning value (P_learn(Tai)); correct a present differential pressure command value (LUprs_slp) based on the learning value (P_learn(Tai)); and send the corrected differential pressure command value (LUprs) to the differential pressure generating device (7, 8).