Automatic Transmission Piston Stroke Return Control
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Solution Overview
Problem
Conventional automatic transmission control devices fail to prevent shocks or engine rotation issues when returning a gear shift stage, due to variations in piston release states during gear shifts, leading to either rapid engagement shocks or engine rotation rises from incorrect oil pressure applications.
Innovation Solution
A device that includes a piston stroke return determination means to detect the released state of a piston actuating friction discs and a gear shift start determination means to restrict gear shifts until the piston is in a predetermined released state after a gear shift, ensuring proper engagement and release states are maintained.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If gear shift control to return the gear shift stage is executed concurrently with the finish of prior gear shift control, then gear shift response speed is improved, but engagement shock or engine rotation rise occurs due to variation in piston release state
Solution Approach 1:
The control device determines whether the piston has returned to the released state before allowing gear shift control to return the gear shift stage to be executed. This preliminary check ensures that the frictional engagement element is in the correct state (piston fully released) before engagement begins, preventing engagement shock while maintaining responsive gear shifts.
2Speed
If gear shift control to return the gear shift stage is executed concurrently with the finish of prior gear shift control, then gear shift response speed is improved, but engine rotation rise occurs when piston release amount is excessive
Solution Approach 1:
The control device checks the piston release state before initiating gear shift control to return the gear shift stage. By verifying that the piston has returned to the released state, the system ensures proper precharge oil pressure is applied, preventing engine rotation rise while maintaining fast response.
3Reliability
If conventional control prohibits target gear shift stage change after inertia phase starts, then gear shift completion is ensured, but it is unclear when to initiate return gear shift control
Solution Approach 1:
The control device uses feedback from the piston state detection to determine when to allow gear shift control to return the gear shift stage. The piston state serves as a clear feedback signal that indicates the appropriate timing for initiating return gear shift control, eliminating the ambiguity in control timing while maintaining gear shift completion reliability.
Data Source
AI summary
A device for controlling an automatic transmission including a first frictional engagement element that is engaged at a first gear shift stage and is released at a second gear shift stage, the device including a piston stroke return determination means for determining a released state of a piston that is actuated to press friction discs of the first frictional engagement element, and a gear shift start determination means for restricting execution of a gear shift from the second gear shift stage to the first gear shift stage until it is determined that the piston is in a predetermined released state after a gear shift from the first gear shift stage to the second gear shift stage is finished.