Automatic Transmission Engagement Pressure Learning During Slip
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Solution Overview
Problem
The increasing demand for improved fuel economy through idling stop techniques reduces opportunities to learn the engagement start pressure of friction engagement elements in automatic transmissions, necessitating a method to ensure learning occasions while the vehicle is running.
Innovation Solution
An automatic transmission system that includes a learning control mechanism to cause the second friction engagement element to slip while running in the second gear position, allowing the learning of the engagement start pressure of the first friction engagement element based on differential rotation changes, enabling accurate determination of the engagement start pressure even when the vehicle is in motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If idling stop techniques are adopted to improve fuel economy, then fuel consumption is reduced, but opportunities to learn engagement start pressure of friction engagement elements are reduced
Solution Approach 1:
The patent transitions the learning control from a static condition (vehicle stopped) to a dynamic condition (vehicle running). The learning control is now executed during vehicle operation by causing a friction engagement element to slip while the vehicle is running, allowing engagement start pressure learning to occur dynamically during normal operation rather than requiring static idle conditions.
Solution Approach 2:
The patent changes the operational parameters under which learning control is executed. Instead of learning only when the vehicle is stopped with the engine running, the system now performs learning when the vehicle is running at various speeds. The control unit adjusts instructional pressure to cause slipping while maintaining vehicle motion, fundamentally changing the operational state parameters for learning execution.
2Measurement precision
If learning control is performed while the vehicle is stopped, then engagement start pressure can be learned, but fuel economy deteriorates due to extended idle time
Solution Approach 1:
The patent transitions the learning control from a static condition (vehicle stopped) to a dynamic condition (vehicle running). The learning control is now executed during vehicle operation by causing a friction engagement element to slip while the vehicle is running, allowing engagement start pressure learning to occur dynamically during normal operation rather than requiring static idle conditions.
Solution Approach 2:
The patent enables continuous learning capability during vehicle operation. Instead of requiring periodic stops for learning, the system can continuously perform learning control whenever the vehicle is running and conditions are appropriate, making the learning process continuous and integrated with normal operation rather than interrupted by idle stops.
3Reliability
If the second friction engagement element is caused to slip during running, then learning of the first friction engagement element can be performed, but differential rotation control complexity increases
Solution Approach 1:
The patent uses the second friction engagement element as an intermediary to indirectly learn the engagement start pressure of the first friction engagement element. By causing the second element to slip and monitoring its differential rotation, the system infers the first element's characteristics without directly testing it, using the second element as a mediator in the learning process.
Solution Approach 2:
The control unit continuously monitors the differential rotation of the second friction engagement element and adjusts the instructional pressure accordingly. When the differential rotation falls within a predetermined range, the control unit determines that the first friction engagement element has reached its engagement start pressure, using feedback from the second element's behavior to learn the first element's characteristics.
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
Ensures occasions to learn the engagement start pressure of friction engagement elements while the vehicle is running, improving the accuracy and reliability of engagement start pressure determination, especially in idling stop vehicles, by using differential rotation changes to determine when the first friction engagement element holds transmission capacity.
Implementation Method 1
a learning control means for causing the second friction engagement element to slip by decreasing an instructional pressure for the second friction engagement element while running in the second gear position, and learning an engagement start pressure of the first friction engagement element based on a change in a differential rotation of the second friction engagement element
Data Source
AI summary
The automatic transmission includes a first friction engagement element which is engaged when a first gear position is realized and disengaged when a second gear position is realized, a second friction engagement element which is engaged when the second gear position is realized and disengaged when the first gear position is realized, and a controller. The controller causes the second friction engagement element to slip by decreasing an instructional pressure for the second friction engagement element while running in the second gear position, and learns an engagement start pressure of the first friction engagement element based on a change in a differential rotation of the second friction engagement element, or in a parameter that changes in accordance with the differential rotation, at a time when an instructional pressure for the first friction engagement element is increased during the slip.