Lock-up clutch hydraulic pressure control via output torque
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Solution Overview
Problem
The existing lock-up clutch control systems face issues with abnormal noise generation when the engine is in a cylinder cut-off state or running at low speed, due to excessive hydraulic pressure calculations, which can lead to clutch slipping at high speeds or all-cylinder running.
Innovation Solution
A control device that calculates a correction factor based on the input rotational speed and cylinder cut-off state to adjust the commanded hydraulic pressure, converging it to the base hydraulic pressure, thereby preventing excessive engagement and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the base hydraulic pressure is calculated from the input torque when the accelerator pedal is depressed, then the lock-up clutch engagement force is improved, but the hydraulic pressure becomes higher than necessary causing abnormal noise
Solution Approach 1:
The invention changes the parameter used for hydraulic pressure calculation from input torque to output torque. When the accelerator pedal is depressed, the output torque reflects the actual torque delivered to the transmission more accurately, preventing over-estimation of required engagement force and thus avoiding abnormal noise while maintaining sufficient clutch engagement.
2Object-affected harmful factors
If the base hydraulic pressure is set at a low level to prevent abnormal noise, then the noise is suppressed, but the lock-up clutch may slip when the engine is rotating at high speed or running with all cylinders
Solution Approach 1:
The invention uses output torque instead of input torque as the basis for calculating hydraulic pressure. Output torque accurately reflects the actual torque transmitted through the torque converter, enabling the system to maintain appropriate engagement pressure across all operating conditions - preventing both abnormal noise and clutch slippage by adapting pressure to actual transmission torque rather than engine torque.
3Force
If the base hydraulic pressure is calculated using input torque in cylinder cut-off state, then the engagement force is sufficient, but the hydraulic pressure becomes excessive causing abnormal noise
Solution Approach 1:
The invention switches from using input torque to using output torque for hydraulic pressure calculation in cylinder cut-off states. Since output torque represents the actual torque being transmitted to the transmission, it provides an accurate basis for determining the minimum necessary engagement pressure, preventing over-pressurization and abnormal noise while ensuring sufficient clutch engagement force.
Data Source
AI summary
In a lock-up clutch control device, base hydraulic pressure calculation device calculates base hydraulic pressure Pb for engaging a lock-up clutch based on input torque from an engine, correction factor calculation device calculates correction factor α, which is greater than 0 but less than 1, for correcting the base hydraulic pressure Pb based on an input rotational speed Ni of a transmission and a cylinder cut-off state of the engine. Commanded hydraulic pressure calculation device calculates a commanded hydraulic pressure Pc from the base hydraulic pressure Pb and the correction factor α by means of: current value of commanded hydraulic pressure Pc←previous value of commanded hydraulic pressure Pc+(base hydraulic pressure Pb−previous value of commanded hydraulic pressure Pc)×α, and the commanded hydraulic pressure Pc is made to converge to the base hydraulic pressure Pb by repeating this a predetermined number of times.