Automatic Transmission Shift Control for Coast-Down Shock Reduction
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Solution Overview
Problem
Conventional shift control systems experience shift shocks during coast-down shifts due to the input shaft rotation speed exceeding the final target output shaft rotation speed, particularly when vehicle deceleration is high.
Innovation Solution
A shift control method that adjusts the target input shaft rotation speed by applying a decreasing correction based on vehicle deceleration, using a system with an integrated controller to manage the automatic transmission and motor generator, ensuring the input shaft rotation speed aligns with the final target synchronization rotation speed to prevent overshoot and shock during clutch engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the basic target synchronizing rotation speed is decreasingly corrected for coast downshift, then the shift smoothness is improved, but the input shaft rotation speed may surpass the final target output shaft rotation speed causing shift shock
Solution Approach 1:
The patent applies dynamics by making the target input shaft rotation speed adjustable and adaptive rather than fixed. The control system dynamically modifies the target speed based on real-time detection of actual input shaft rotation speed, preventing overshoot while maintaining shift smoothness. This dynamic adjustment resolves the contradiction between smoothness improvement and shock prevention.
Solution Approach 2:
The patent implements feedback control by detecting the actual input shaft rotation speed and comparing it with the target speed. When overshoot is detected, the system feeds back this information to adjust the target input shaft rotation speed downward, preventing shift shock. This closed-loop feedback mechanism simultaneously achieves shift smoothness and prevents the harmful overshoot effect.
2Reliability
If the target input shaft rotation speed is significantly reduced to prevent overshoot, then shift shock is suppressed, but the shift time increases
Solution Approach 1:
The patent applies partial action by making targeted, moderate adjustments to the target input shaft rotation speed only when necessary to prevent overshoot. Rather than significantly reducing the target speed in all cases, the system makes precise partial adjustments based on actual conditions, suppressing shift shock while minimizing impact on shift time.
Solution Approach 2:
The patent changes the parameter of target input shaft rotation speed dynamically based on detected conditions. When overshoot risk is detected, the parameter is adjusted; when not needed, the original parameter is maintained. This selective parameter change approach suppresses shift shock without unnecessarily extending shift time.
3Object-affected harmful factors
If the input shaft rotation speed is rapidly reduced during coast downshift, then the synchronization shock is minimized, but the control precision decreases leading to potential overshoot
Solution Approach 1:
The patent uses feedback control to detect the actual input shaft rotation speed and compare it with the target speed. This precise detection and comparison mechanism maintains control precision even during rapid speed changes, preventing overshoot while minimizing synchronization shock through accurate real-time monitoring and adjustment.
Solution Approach 2:
The patent applies dynamics by making the target input shaft rotation speed adaptive rather than fixed. The system dynamically adjusts the target speed based on detected actual conditions, maintaining precise control during rapid transitions. This dynamic approach prevents overshoot while managing synchronization shock effectively.
Data Source
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AI summary
The present invention provides a shift control method implemented in a vehicle equipped with an automatic transmission for controlling an input shaft rotation speed to a target input shaft rotation speed during a shift. The method includes setting of a basic target synchronization rotation speed that is a basic target value of the input shaft rotation speed during the shift, and setting of a corrected target input shaft rotation speed as the target input shaft rotation speed when the shift is a downshift without a requirement for a driving force of the vehicle, The corrected target input shaft rotation speed is obtained by decreasingly correcting the basic target synchronization rotation speed. Further, a decreasing correction amount of the basic target synchronization rotation speed is set so as to become larger as a deceleration of the vehicle becomes larger.