Automatic Transmission Skip-Shift Control Method
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Solution Overview
Problem
Conventional skip-shift control methods for automatic transmissions, such as the 6 to 3 shift, face challenges in efficiently releasing two frictional elements and engaging two others, leading to prolonged shifting times, poor shift feel, and torque fluctuations due to intermediate gear ratios being realized, resulting in a double shift feel and shift shock.
Innovation Solution
A shift control method that synchronizes the release and engagement of frictional elements by starting the release of the second frictional element after the first and beginning the engagement of the fourth frictional element after the third, ensuring they are completed at specific synchronizing points to avoid intermediate gear ratios, thereby improving shift feel and reducing torque fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If two frictional elements are released and two other frictional elements are engaged during skip-shift, then the shift speed range coverage is improved, but the shifting time becomes excessively long and shift feel deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-engaging the third frictional element before fully disengaging the first frictional element during the skip-shift process. This overlapping sequence ensures that the transmission is ready for the target gear ratio before the current gear is fully released, thereby reducing total shifting time while maintaining smooth transition. The control method specifically times the engagement of the third frictional element to begin before the first frictional element is completely disengaged, preventing idle time between shifts.
Solution Approach 2:
The patent segments the skip-shift process into distinct phases with different frictional element engagement states. Instead of treating the shift as a single atomic operation, it divides the process into: (1) initial state with first and second frictional elements engaged, (2) transition phase where third frictional element engages while first is still partially engaged, and (3) final state with third and fourth frictional elements engaged. This segmentation allows precise control over the timing of each frictional element, optimizing the overall shift duration.
2Adaptability or versatility
If two frictional elements are released and two other frictional elements are engaged during skip-shift, then the gear ratio change is achieved, but the shift feel deteriorates due to poor smoothness
Solution Approach 1:
The patent applies preliminary action by pre-engaging the third frictional element before fully disengaging the first frictional element during the skip-shift process. This overlapping sequence ensures that the transmission is ready for the target gear ratio before the current gear is fully released, thereby reducing total shifting time while maintaining smooth transition. The control method specifically times the engagement of the third frictional element to begin before the first frictional element is completely disengaged, preventing idle time between shifts.
Solution Approach 2:
The patent applies beforehand cushioning by carefully controlling the pressure application to the third frictional element during its engagement. The control method gradually increases pressure on the third frictional element while it is being engaged, preventing sudden torque changes that would cause shock. This cushioning effect is timed to occur during the transition phase, ensuring smooth power transmission throughout the skip-shift operation and maintaining good shift feel despite the complex multi-element engagement sequence.
3Loss of time
If shift from 6 speed to 3 speed is performed by way of middle speed with overlapped shifts, then shifting time is reduced, but shift torque is generated and double shift feel occurs causing shift shock
Solution Approach 1:
The patent applies the taking out principle by extracting and eliminating the middle speed state from the skip-shift process. Instead of allowing the transmission to pass through intermediate gear ratios (which would create double shift feel and torque fluctuations), the control method directly transitions from the 6th gear frictional element engagement to the 3rd gear frictional element engagement. The third frictional element is engaged in a manner that bypasses the creation of intermediate gear states, thereby removing the source of shift shock and torque fluctuation while maintaining reduced shifting time.
Data Source
AI summary
A shift control method of an automatic transmission according to this invention controls a shift from an N speed achieved by engagement of first and second frictional elements to an N−3 speed achieved by engagement of third and fourth frictional elements, wherein release of the second frictional element begins after release of the first frictional element begins and engagement of the fourth frictional element begins after engagement of the third frictional element begins, and wherein the engagement of the third frictional element is completed substantially at the same time that the release of the second frictional element is completed.