Automatic Transmission Skip Shift Control
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Solution Overview
Problem
Conventional shift control methods for automatic transmissions, particularly in skip shifting processes like 6 to 3, face challenges with prolonged shifting times and a non-smooth shift due to successive shifting processes, leading to potential double shift feel and difficulty in controlling on-coming and off-going elements.
Innovation Solution
A shift control method that engages first and second friction elements for the nth shift speed and third and fourth friction elements for the (n−3)th shift speed, where release control of the second friction element begins after the first, and engagement control of the fourth friction element starts simultaneously with the synchronizing point reached, avoiding the middle shift speed to prevent double shift feel and facilitating smooth transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two shifting processes are performed successively (6 to 4 then 4 to 3), then the shift can be controlled through standard procedures, but the shifting time becomes long and the shift feels non-smooth
Solution Approach 1:
The patent merges two separate shifting processes (6 to 4 and 4 to 3) into a single integrated skip shift operation. By combining the release of first and second friction elements with the engagement of third and fourth friction elements into one coordinated process, the system achieves a 6 to 3 skip shift without passing through 4th gear, thereby reducing total shifting time and improving smoothness while maintaining control reliability through synchronized multi-element management.
Solution Approach 2:
The control system performs preliminary coordination of friction element states before the actual shift occurs. By pre-calculating and pre-positioning the release and engagement sequences of multiple friction elements, the system prepares the transmission for skip shifting in advance, enabling smoother and faster transitions without compromising the reliability of control during the actual shifting event.
2Loss of time
If first and second shifts are overlapped to reduce shifting time, then shifting speed improves, but a double shift feel is perceived and control complexity increases
Solution Approach 1:
The patent implements dynamic control of friction element release and engagement by continuously monitoring turbine speed and adjusting hydraulic pressure accordingly. The system dynamically coordinates the release of off-going friction elements with the engagement of on-coming elements based on real-time speed conditions, enabling smooth skip shifts that adapt to changing operational parameters without creating double shift feel, thus maintaining ease of operation while reducing shifting time.
Solution Approach 2:
The control system incorporates feedback mechanisms that monitor turbine speed and friction element engagement status throughout the shifting process. By using this feedback information, the system adjusts the timing and pressure of friction element actuation to prevent double shift feel, ensuring smooth transitions during skip shifts while maintaining the reduced shifting time benefit.
3Ease of operation
If controls of on-coming and off-going elements are started at different times, then some shift control is possible, but difficulty arises when another shift speed change is needed during the process
Solution Approach 1:
The control system performs preliminary coordination of all friction element operations before the shift begins. By pre-establishing the release and engagement sequences for all four friction elements involved in the 6 to 3 skip shift, the system simplifies control coordination complexity while maintaining full shift control capability. This preliminary planning enables the system to handle additional shift speed changes during the process without increasing operational difficulty.
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
This method improves shift feel by preventing the achievement of a middle shift speed and enables smoother transitions during nth to (n−3)th shifts by controlling hydraulic pressures effectively, allowing for simultaneous release and engagement of friction elements.
Implementation Method 1
one frictional element is released and another frictional element is engaged
Implementation Method 2
Hydraulic pressure of the first friction element may be reduced to a neutral state
Data Source
AI summary
A shift control method of an automatic transmission that controls a shift from an nth shift speed, achieved by engagement of first and second friction elements, to an (n−3)th shift speed, achieved by engagement of third and fourth friction elements. The method includes releasing the first and second friction elements and engaging the third and fourth friction elements. Release control of the second friction element begins after release control of the first friction element begins. Engagement control of the fourth friction element begins after an engagement control of the third friction element begins.