Lock-up clutch slip control via integration limit
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Solution Overview
Problem
Conventional drive slip control technologies for torque converters lead to a rapid increase in engine rotational speed due to the dead zone of the lock-up clutch piston during drive slip control, causing discomfort to the driver, as the actual slip rotational speed does not reach the target speed, especially at low engine torque conditions.
Innovation Solution
A control apparatus for the lock-up clutch that includes a differential pressure generator, sensors for engine and input rotational speeds, and a controller implementing proportional integration control to adjust the differential pressure, ensuring the actual slip rotational speed matches the target speed by accumulating and limiting the integration value to prevent negative differential pressures and thus avoid the dead zone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If drive slip control is implemented to maintain constant slip rotational speed, then the lock-up clutch engagement control is improved, but negative differential pressure is generated causing the piston to enter the dead zone
Solution Approach 1:
The control apparatus prevents the integration value from becoming excessive before negative differential pressure can occur. By monitoring and limiting the integration value during proportional integration control, the system takes preliminary action to avoid the condition that would cause the piston to enter the dead zone, thereby preventing the harmful effect before it occurs.
2Measurement precision
If the integration value is allowed to accumulate freely to achieve target slip rotational speed, then the slip control precision is improved, but the piston enters the dead zone causing delayed lock-up engagement
Solution Approach 1:
The control apparatus uses feedback by continuously monitoring the integration value and comparing it against a predetermined threshold. When the integration value reaches the threshold, the system provides feedback to stop further integration, thereby preventing the piston from entering the dead zone while maintaining accurate slip rotational speed control through regulated accumulation of the integration value.
3Speed
If pressure reduction command is output to reduce differential pressure, then the actual slip rotational speed approaches target speed, but the piston enters the dead zone
Solution Approach 1:
The control apparatus takes preliminary action by preventing the integration value from becoming excessive before it can cause negative differential pressure and piston dead zone entry. This proactive limitation ensures that the lock-up clutch remains responsive to accelerator input while still achieving the target slip rotational speed through controlled pressure adjustment.
Data Source
AI summary
A lock-up clutch control apparatus for controlling a lock-up clutch (6) provided in a torque converter (5) installed between an engine (3) and a transmission (4), is disclosed. The lock-up clutch control apparatus has a differential pressure generator (7,8) which engages, causes a slip of or disengages the lock-up clutch by adjusting the differential pressure supplied to the lock-up clutch (6); a sensor (11/15) for detecting a rotational speed of the engine; a sensor (16) for detecting an input rotational speed to the transmission; and a controller (1). The controller (1) conducts proportional integration control by using a command signal to the differential pressure generator (7,8), so that an actual slip rotational speed, which is the difference between the engine rotational speed (Np) and input rotational speed (Ni) to the transmission, becomes a target slip rotational speed (Nt). The controller is programmed to conduct integration accumulating the difference (ΔN) between the target slip rotational speed (Nt) and the actual slip rotational speed (SN); to determine whether the accumulated integrated value (I) is equal to or higher than a predetermined integration value (It); and to stop the integration when the accumulated integration value (I) is equal to or higher than the predetermined integration value (It).