CVT Lock-Up Clutch Engagement Control via Speed Alignment
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Solution Overview
Problem
Existing control systems for continuously variable transmissions face challenges in achieving stable engagement of the lock-up clutch due to variations in friction characteristics, leading to torque amplification and awkward vehicle acceleration feelings.
Innovation Solution
A control device that adjusts the transmission ratio of the continuously variable transmission mechanism to ensure the turbine rotation speed approaches the engine rotation speed before full lock-up clutch engagement, thereby suppressing torque amplification and stabilizing clutch engagement, even with varying friction coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the lock-up clutch is engaged while maintaining the transmission ratio set according to traveling condition, then the clutch engagement is simple to control, but torque amplification occurs and engine rotation speed drops excessively causing awkward acceleration feeling
Solution Approach 1:
The control device performs preliminary action by adjusting the transmission ratio before the lock-up clutch is fully engaged. Specifically, when the rotation speed difference between engine and turbine becomes equal to or less than a predetermined value, the transmission ratio is adjusted to make the turbine rotation speed approach the engine rotation speed more than in normal conditions. This preliminary adjustment suppresses torque amplification before it occurs during full engagement.
2Reliability
If the transmission ratio is adjusted to suppress torque amplification, then engine load is reduced and clutch engagement is stabilized, but the control system becomes more complex
Solution Approach 1:
The control device uses feedback by continuously monitoring the rotation speed difference between the engine and turbine. When this difference reaches a predetermined threshold, the system automatically adjusts the transmission ratio to control the turbine rotation speed. This feedback mechanism ensures stable clutch engagement while managing torque amplification through dynamic adjustment based on real-time operating conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for stable and smooth lock-up clutch engagement, reducing engine load and preventing awkward acceleration feelings by controlling the transmission ratio to align turbine and engine speeds, thus enhancing the overall driving experience.
Implementation Method 1
a torque convertor provided between an engine and the continuously variable transmission mechanism, the torque convertor having a pump impeller rotating integrally with the engine, a turbine runner rotating integrally with an input shaft of the continuously variable transmission mechanism
Implementation Method 2
a lock-up clutch connecting the pump impeller and the turbine runner
Data Source
AI summary
Control device for continuously variable transmission has continuously variable transmission mechanism (CVT) transmitting power with belt (7) wound around primary and secondary pulley (5, 6); torque convertor (2) having pump impeller (20), turbine runner (21) and lock-up clutch (2a); and control unit (10) controlling lock-up clutch (2a) to predetermined engagement state and controlling the CVT to predetermined transmission ratio, according to travelling condition. Control unit (10) is configured to, when shifting lock-up clutch (2a) from disengagement to engagement state, control transmission ratio of CVT so that when rotation speed difference (ΔN) between engine speed (Ne) and turbine speed (Nt) that is rotation speed of turbine runner is predetermined rotation speed difference (ΔN1) or less, turbine speed (Nt) approaches engine speed (Ne) more than turbine speed (Nt1) of case where control of transmission ratio of CVT, which is set according to travelling condition during shift of lock-up clutch (2a), is continued.