Automatic Transmission Start Lag Control via Intention-Based Pre-Charging
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Solution Overview
Problem
In automatic transmissions, the start lag – the time until the transmission capacity becomes non-zero after switching from neutral to drive range – is limited by the risk of reducing line pressure when increasing pre-charge pressure, preventing effective shortening of start lag and ensuring learning control accuracy.
Innovation Solution
An automatic transmission system with a starting frictional engagement element, hydraulic control means to increase hydraulic pressure, learning control means to achieve a target start time, and starting intention detection means to adjust hydraulic pressure and prohibit learning control when driver intention is detected, ensuring increased pre-charge pressure without excessive line pressure reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If pre-charge pressure is increased to shorten start lag, then start responsiveness is improved, but line pressure is excessively reduced
Solution Approach 1:
The system performs pre-charging by increasing hydraulic pressure to the starting frictional engagement element before power transmission begins. This preliminary action narrows the clearance between frictional engagement plates, preparing the system for immediate torque transmission while controlling the timing and magnitude of pressure increase to avoid excessive line pressure reduction
Solution Approach 2:
The hydraulic control means dynamically adjusts the pre-charge pressure based on detected driver starting intention. When starting intention is detected, the system increases pre-charge pressure more aggressively to minimize start lag, while automatically prohibiting learning control during this period to prevent erroneous corrections that would occur due to line pressure fluctuations
2Loss of time
If pre-charge pressure is increased excessively, then start lag is shortened, but learning control accuracy deteriorates
Solution Approach 1:
The learning control mechanism continuously monitors start lag and adjusts pre-charge pressure to achieve a target start time. The system incorporates feedback from start lag measurements to correct pre-charge pressure, but intelligently prohibits this learning control when driver starting intention is detected, preventing erroneous corrections that would result from line pressure reduction during active pre-charging
Solution Approach 2:
The system proactively prohibits learning control when starting intention is detected before the starting frictional engagement element begins generating transmission capacity. This preliminary anti-action prevents the learning control from attempting to measure and correct start lag during periods when line pressure is being reduced, thereby avoiding erroneous learning corrections
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 solution enhances start responsiveness by correcting pre-charge pressure based on driver intention while preventing erroneous learning control and ensuring the learning control's chance of execution, maintaining line pressure stability.
Implementation Method 1
hydraulic control means configured to increase an indicated hydraulic pressure to the starting frictional engagement element
Implementation Method 2
the input-side and output-side frictional engagement plates are pressed against each other to engage the starting frictional engagement element
Data Source
AI summary
A transmission controller increases an indicated hydraulic pressure to a starting frictional engagement element to a normal hydraulic pressure, causes a hydraulic piston to stroke and executes a learning control of the indicated hydraulic pressure so that a time until the starting frictional engagement element starts generating a transmission capacity after the range is switched from the neutral range to the drive range becomes a target time when a range is switched from a neutral range to a drive range. The transmission controller further detects a driver's starting intention and increases the indicated hydraulic pressure to the starting frictional engagement element to a starting time hydraulic pressure higher than the normal hydraulic pressure and prohibits the learning control if the starting intention is detected before the starting frictional engagement element starts generating the transmission capacity.