Automatic Transmission Shift Control via Clutch Slip Learning
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Solution Overview
Problem
In gear-type automatic transmissions with frictional engagement elements, manufacturing errors and degradation can lead to inconsistencies in torque transmission characteristics, causing shift shocks and dynamic compression due to mismatched design and actual torque transmission values.
Innovation Solution
A control device and method that use a programmable controller to manage the engagement of frictional elements by causing a minute slip at the second engagement element during shifts, learning the engaging state variation, and correcting the engaging force to ensure smooth transitions between gear states, thereby compensating for inconsistencies in torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the engaging oil pressure is increased with a predetermined slope and the disengaging oil pressure is reduced with a predetermined slope to prevent shift shock, then shift smoothness is improved, but the actual torque transmission characteristics still deviate from design values due to manufacturing errors and degradation, causing residual shift shocks
Solution Approach 1:
The control device performs preliminary learning of the actual torque transmission characteristics by detecting the relationship between engaging oil pressure and piston stroke length before normal operation. This preliminary characterization allows the system to pre-calculate corrected oil pressure values that compensate for manufacturing errors and degradation, enabling accurate torque transmission control from the start of compensated operation without requiring real-time adjustments during shifts
Solution Approach 2:
The control device establishes a feedback mechanism where the actual torque transmission characteristics are continuously learned and stored as correction data. During subsequent shift operations, the control device retrieves previously learned correction values and applies them to adjust the engaging oil pressure, creating a closed-loop system that progressively improves shift quality by compensating for deviations between design and actual characteristics
2Device complexity
If the engaging oil pressure is controlled based on design values without compensation, then the control system is simple, but shift shocks and dynamic compression occur due to the difference between actual and design torque transmission characteristics
Solution Approach 1:
The control device replaces purely mechanical design-value-based oil pressure control with a hybrid system that incorporates electronic learning and calculation. The control device detects actual piston stroke lengths, calculates correction values based on learned characteristics, and adjusts oil pressure accordingly. This substitution of mechanical control with intelligent control algorithms eliminates shift shocks while maintaining acceptable system complexity through software-based compensation rather than complex mechanical adjustments
Solution Approach 2:
The control device dynamically changes the engaging oil pressure parameter based on learned correction values derived from actual torque transmission characteristics. Instead of using fixed design values, the system adjusts the oil pressure parameter in real-time according to detected deviations, transforming the control approach from static to adaptive and thereby eliminating shift shocks caused by manufacturing variations and degradation
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
The solution ensures smooth shift operations by accurately adjusting the engaging forces and pressures, reducing shift shocks and dynamic compression, and maintaining optimal torque transmission characteristics.
Implementation Method 1
a frictional engagement element that transmits or blocks rotation of an input shaft or an output shaft
Data Source
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AI summary
A subtransmission mechanism 30 comprises a Ravigneaux planetary gear mechanism 31, a Low brake 32 and a High clutch 33, shifts between a first speed gear position in which the Low brake 32 is engaged whereas the High clutch 33 is disengaged and a second speed gear position in which the Low brake 32 is disengaged and the High clutch 33 is engaged. A minute slip is caused at the Low brake 32 and then terminated by engaging the High clutch 33. A value representing the engaging state variation such as an engaging time period and/or an engaging speed of the High clutch 33 is learned and the pressure of oil supplied during the engaging operation of the High clutch 33 is corrected based upon the learned value, thereby assuring a smooth shift operation by compensating for any consistency in the torque transmission characteristics of the High clutch 33.