Automatic Transmission Skip-Shift Control via Frictional Element Sequencing
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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 shifting gears due to the need to release and engage multiple frictional elements simultaneously, leading to prolonged shifting times, rough shifting processes, and a deteriorated driver shift feel, with issues like shift torque fluctuations and turbine speed inconsistencies.
Innovation Solution
A shift control method that coordinates the release and engagement of frictional elements in an automatic transmission by initiating the release of the second frictional element after the first, and the engagement of the fourth frictional element after the third, with synchronized hydraulic pressure control to maintain a smooth turbine speed slope, avoiding the realization of a middle speed during the shift from N to N-3 speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If two frictional elements are released and two other frictional elements are engaged simultaneously during a 6 to 3 skip shift, then the shifting process can be completed in one step, but it is hard to be realized and requires complex coordination
Solution Approach 1:
The patent segments the simultaneous engagement and release of frictional elements into a coordinated sequence with four distinct phases: (1) release first frictional element, (2) release second frictional element, (3) engage third frictional element, (4) engage fourth frictional element. This segmentation makes the complex control achievable through structured timing while maintaining the benefit of near-simultaneous operation.
Solution Approach 2:
The patent applies preliminary action by pre-coordinating the timing and pressure control sequences before the actual shift occurs. The control system prepares the hydraulic pressure profiles and timing schedules in advance, ensuring that all four frictional elements can be transitioned smoothly without requiring complex real-time coordination during the shift itself.
2Ease of operation
If a 6 to 4 shift is completed followed by a 4 to 3 shift, then the shift control is simpler, but the shifting time becomes long and the shift feel deteriorates
Solution Approach 1:
The patent merges two sequential shift operations (6 to 4 and 4 to 3) into a single coordinated skip-shift operation. By overlapping the engagement and release of frictional elements from both shifts, the system achieves a direct 6 to 3 transition that eliminates the intermediate 4th gear dwell time, reducing total shifting time while maintaining control through structured phase coordination.
Solution Approach 2:
The patent ensures continuity of useful action by maintaining torque transmission throughout the skip-shift process. The coordinated engagement and release of frictional elements ensures that power flow continues without interruption or dwell at intermediate speeds, eliminating the time loss associated with sequential shifting while maintaining smooth torque transfer.
3Reliability
If shifting from 6 speed to 3 speed is performed by way of a middle speed, then the shift process can be controlled step by step, but a double shift feel is felt and shift shock occurs
Solution Approach 1:
The patent applies skipping by rushing through the intermediate speed range without dwelling at the middle speed (4th gear). The coordinated frictional element transitions are designed to complete the 6 to 3 shift directly, skipping the intermediate operational state that would produce a double shift feel or shock, while maintaining reliability through precise timing control.
Solution Approach 2:
The patent uses dynamics by making the frictional element engagement and release profiles adaptive and continuous rather than fixed and discrete. The hydraulic pressure control dynamically adjusts the timing and rate of frictional element transitions, allowing the system to maintain reliable control while achieving smooth, shock-free shifting by continuously optimizing the transition characteristics.
4Ease of operation
If hydraulic pressure is controlled to maintain a smooth turbine speed slope, then the shift feel improves, but the control system becomes more complex
Solution Approach 1:
The patent applies parameter changes by systematically varying hydraulic pressure parameters (pressure magnitude, rate of change, timing) for each frictional element transition. The control system adjusts these pressure parameters to maintain a smooth turbine speed slope throughout the skip-shift, improving shift feel while managing complexity through structured parameter profiles for each of the four frictional element transitions.
Data Source
AI summary
A shift control method of an automatic transmission according to an exemplary embodiment of the present invention may control 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 is completed after release of the first frictional element begins, and engagement of the fourth frictional element begins after engagement of the third frictional element begins, wherein the engagement of the third frictional element is completed after the release of the second frictional element is completed.