Overlapping Shift Control for Automatic Transmission Skip-Shift
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Solution Overview
Problem
Current automatic transmission shift control methods face difficulties in precise control during skip-shifting processes, particularly in shifts like 8 to 2, where two frictional elements must be released and two engaged, leading to inefficiencies and potential double shift feel due to torque generation and reliance on turbine rotation speed alone.
Innovation Solution
A shift control method that detects turbine and planetary gear set rotation speeds to control the engagement and release of frictional elements, overlapping shifts to maintain a consistent gear ratio, with simultaneous release and engagement controls based on predetermined speed and time conditions to synchronize the shift process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two successive shifting processes are used to perform an 8 to 2 skip shift, then the shift can be completed, but additional time is required and shift feel deteriorates
Solution Approach 1:
The patent merges two separate shifting processes (8-7 and 7-2) into a single overlapping shift operation. The control device coordinates the release of first and second frictional elements while simultaneously engaging third and fourth frictional elements, allowing both shift processes to occur concurrently rather than sequentially, thereby reducing total shift time and improving shift feel.
Solution Approach 2:
The control device performs preliminary preparation by pre-engaging the third frictional element before completely releasing the first frictional element. This preliminary action ensures that the intermediate gear ratio is already established, allowing the shift to proceed smoothly without torque interruption or double shift feel, thus completing the shift faster and more reliably.
2Reliability
If two frictional elements are released and two other frictional elements are engaged during skip-shifting, then the shift can be completed, but controlling this shift is difficult
Solution Approach 1:
The patent segments the control of four frictional elements into two independent control groups: the first and second frictional elements are controlled based on turbine rotation speed, while the third and fourth frictional elements are controlled based on planetary gear set rotation speed. This segmentation simplifies the overall control complexity by dividing it into manageable subsystems with distinct control parameters.
Solution Approach 2:
The control device employs feedback mechanisms by continuously monitoring both turbine rotation speed and planetary gear set rotation speed. Based on this real-time feedback, the control device dynamically adjusts the engagement and release timing of each frictional element, ensuring precise control despite the complexity of coordinating four frictional elements during the skip-shift operation.
3Ease of operation
If shift is controlled according only to rotation speed of turbine, then the control is simple, but the shift may not be precisely controlled
Solution Approach 1:
The patent makes the control system multi-functional by using two independent rotation speed signals (turbine speed and planetary gear set speed) for controlling different frictional elements. This universal approach allows the system to maintain simplicity in control logic while achieving precision through the complementary information provided by both speed sensors, effectively resolving the trade-off between simplicity and precision.
Data Source
AI summary
A shift control method and apparatus of an automatic transmission for controlling a shift from one speed, achieved by engagement of a first and a second frictional element, to another speed, achieved by engagement of a third and a fourth frictional element. The method includes detecting a rotation speed of a turbine, detecting a rotation speed of at least one operating member of at least one planetary gear set of the automatic transmission, and controlling the shift according to the rotation speeds of the turbine and the operating member. The control includes overlapping a first shift, from the one speed to an additional speed, with a second shift, from the additional speed to the other speed. The additional speed has a gear ratio that is near a gear ratio of the one speed.