Automatic Transmission Double-Transition Shift Control for Clutch Heat Limits
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Solution Overview
Problem
Double transition shifts in transmissions with multiple gearing sections are challenging to control due to complex interactions between gear sections, leading to excess heat buildup and increased strain on clutch elements, especially during power-on shifting which prioritizes efficiency and responsiveness.
Innovation Solution
A transmission control system utilizing at least three speed sensors for optimized clutch control during double transition shifts, employing simultaneous closed-loop control and model-based calculations to ensure proper clutch pressures and torques, preventing overheating by locking up primary clutches before secondary clutches reach thermal limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If multiple clutches are engaged or disengaged simultaneously during double transition shifts, then the transmission can achieve desired speed ratio changes, but excess heat buildup occurs in the clutch elements
Solution Approach 1:
The patent segments the double transition shift into multiple phases: first shifting the primary gear section, then shifting the secondary gear section. This temporal segmentation separates the simultaneous clutch operations into sequential operations, reducing the total slip energy and heat generation in each clutch during the overall shift event.
Solution Approach 2:
The patent applies preliminary action by pre-shifting the primary gear section before shifting the secondary gear section. The primary on-coming clutch is engaged and the primary off-going clutch is disengaged first, establishing a preliminary gear ratio change that reduces the burden on the secondary clutches and minimizes simultaneous heat generation.
2Temperature
If the shift rate is increased to reduce heat buildup time, then heat accumulation is reduced, but control difficulty and strain on transmission elements increase
Solution Approach 1:
The patent employs feedback control by continuously monitoring the speeds of the input shaft, intermediate shaft, and output shaft, and adjusting clutch pressures in real-time based on actual shift progression. This closed-loop control enables precise management of clutch engagement/disengagement timing and pressure, facilitating complex double transition shifts without excessive control difficulty.
Solution Approach 2:
The patent applies dynamics by making the clutch pressure profiles adaptive and time-varying during the shift event. The control system dynamically adjusts clutch pressures based on real-time shaft speed measurements and model-based predictions, optimizing the shift trajectory to balance heat reduction with control feasibility.
3Productivity
If power on shifting is used to maintain output torque and improve efficiency, then transmission responsiveness is enhanced, but control complexity and strain on clutch elements increase
Solution Approach 1:
The patent uses feedback control to maintain power-on shifting conditions by continuously monitoring shaft speeds and adjusting clutch pressures to keep the transmission in a controlled slip state throughout the double transition. This real-time feedback enables the complex coordinated control of multiple clutches while maintaining torque delivery and shift quality.
Solution Approach 2:
The patent replaces purely mechanical clutch control with an electronically controlled system that uses sensors to detect shaft speeds and a control algorithm to calculate optimal clutch pressures. This substitution of electronic control for mechanical linkage enables precise management of the complex double transition shift while maintaining power-on shifting benefits.
4Reliability
If simultaneous closed loop control is applied to both shifts in a double transition, then shift quality is improved, but computational requirements and control system complexity increase
Solution Approach 1:
The patent segments the control of the double transition shift into two separate closed-loop control systems: one for the primary gear section and one for the secondary gear section. Each control loop manages its respective clutches independently based on shaft speed feedback, achieving high shift quality through coordinated but separate control rather than a single complex unified controller.
Data Source
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AI summary
A system and method for controlling double transition shifts in an automatic transmission having multiple gear sections. During a double transition shift, the system performs simultaneous closed loop control of the primary oncoming clutch in the primary gear section and the secondary off-going clutch of the secondary gear section. Before the input shaft of the secondary gear section is fully pulled down or the secondary off-going clutch becomes overheated, the system switches closed loop control of the input shaft to the secondary on-coming clutch of the secondary gear section. The system utilizes model-based calculations to determine the initial clutch pressure settings when a clutch enters closed loop control.