Lock-up Clutch Control via Engine Speed
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Solution Overview
Problem
During vehicle start, the existing slip control for lock-up clutches in torque converters experiences instability due to delays and errors in engine torque signals, leading to excessive or insufficient torque capacity, causing hunting and uncomfortable driving experiences.
Innovation Solution
The control system computes a control target value based on actual engine rotation speed and target rotation speed, controlling the engagement force of the lock-up clutch without using the engine torque signal, thereby preventing hunting and maintaining stable torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If feedforward control and feedback control are performed using engine torque signal, then torque transmission efficiency is improved, but control stability deteriorates due to signal delay and errors causing hunting
Solution Approach 1:
The invention extracts and removes the problematic engine torque signal from the control system. Instead of using the engine torque signal for feedforward and feedback control, the patent directly controls the lock-up clutch based on engine rotation speed and turbine rotation speed, eliminating the source of signal delay and errors that caused hunting and control instability.
Solution Approach 2:
The invention introduces engine rotation speed and turbine rotation speed as intermediary parameters for control. These rotation speed signals serve as more reliable mediators compared to the engine torque signal, allowing the control system to achieve stable torque transmission without the delays and errors inherent in torque signal processing.
2Power
If lock-up clutch capacity is adjusted based on engine torque signal, then torque transmission is optimized, but hunting occurs due to difference between signal value and actual torque
Solution Approach 1:
The invention substitutes the mechanical torque signal-based control system with a rotation speed-based control system. By replacing the engine torque signal with direct measurement and control based on engine and turbine rotation speeds, the system achieves more accurate and stable torque transmission without the hunting caused by torque signal inaccuracies.
3Ease of operation
If proportional/integral feedback control is performed on lock-up clutch pressure, then basic control function is achieved, but deviation from target slippage increases during acceleration/deceleration
Solution Approach 1:
The invention applies preliminary action by directly controlling the lock-up clutch engagement based on rotation speed differences before slippage deviation becomes significant. The control system proactively adjusts clutch pressure based on the relationship between engine and turbine rotation speeds, preventing large slippage deviations during acceleration and deceleration rather than merely reacting to them.
Data Source
AI summary
A device for controlling a start of a vehicle includes a rotation speed obtaining unit that obtains an actual engine rotation speed of the engine, a target rotation speed computing unit that computes a target rotation speed of the engine in the slip control, a control target value computing unit that computes a control target value, which is a target value for controlling the engine rotation speed to the target rotation speed based on the actual engine rotation speed and the target rotation speed, and an instruction value computing unit that computes an instruction value for the lock-up clutch necessary to control the engine rotation speed to the control target value based on the control target value.