Accumulator Isolation for Hydraulic Stiffness in Idle-Stop Transmissions
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Solution Overview
Problem
Existing engine idle-stop systems face issues with reduced hydraulic stiffness and pressure oscillations in transmission clutch hydraulic circuits, leading to delayed clutch engagement and reduced engine restart quality, particularly due to the use of accumulators which can compromise response times and engagement efficiency.
Innovation Solution
A method that isolates the accumulator from the hydraulically actuated transmission component when pressure is above a threshold during engine idle-stop and couples it back in when pressure drops, maintaining hydraulic stiffness and pressure in the clutch hydraulic circuit, thereby enabling rapid clutch engagement and modulation without the need for an auxiliary pump.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the accumulator is continuously connected to the transmission clutch hydraulic circuit during engine idle-stop, then hydraulic pressure is maintained, but hydraulic stiffness is reduced and pressure oscillations occur
Solution Approach 1:
The system dynamically switches the accumulator connection state based on real-time pressure feedback. The ECU monitors hydraulic pressure and alternately couples and decouples the accumulator from the clutch circuit, transforming a static connection into a dynamic, adaptive system that maintains stiffness while preventing oscillations
Solution Approach 2:
The system implements closed-loop feedback control where the ECU continuously monitors hydraulic pressure in the clutch circuit and uses this feedback to control the accumulator isolation valve. When pressure drops below a threshold, the valve opens to couple the accumulator; when pressure is sufficient, the valve closes to isolate it, maintaining optimal hydraulic stiffness
2Stress or pressure
If the accumulator is continuously connected to maintain pressure, then pressure stability is improved, but clutch engagement response time is delayed
Solution Approach 1:
The system dynamically adjusts accumulator connection based on operational phase. During clutch engagement, the accumulator is isolated to maintain hydraulic stiffness and enable rapid response. During idle-stop maintenance, it is coupled when pressure drops, providing a time-adaptive solution
3Stress or pressure
If an auxiliary transmission pump is used to pressurize hydraulic fluid during idle-stop, then hydraulic pressure is maintained, but component cost increases and fuel savings are reduced
Solution Approach 1:
The system uses the existing accumulator component to self-regulate and maintain hydraulic pressure during idle-stop conditions. The accumulator autonomously compensates for pressure drops through the feedback-controlled valve system, eliminating the need for additional active pumping components
Solution Approach 2:
The invention extracts and utilizes the pressure-storing function already present in the accumulator component, separating this function from the need for continuous active pressurization. By isolating and utilizing the accumulator's energy storage capability, the system eliminates the auxiliary pump requirement
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 approach maintains hydraulic line pressure and stiffness during engine idle-stop and restart, improving clutch engagement response times and overall engine restart quality by alternately coupling and decoupling the accumulator from the transmission component based on pressure feedback, ensuring swift transmission gear engagement and reduced oscillations.
Implementation Method 1
a clutch hydraulic circuit (46) coupled to a transmission pump (38) and an accumulator (44)
Implementation Method 2
the transmission is isolated and oil pressure in the transmission is maintained by a check valve and an accumulator
Data Source
AI summary
Methods and systems are provided for pressurizing a hydraulic circuit comprising a hydraulically actuated transmission component and an accumulator. One example method comprises, during an engine idle-stop, adjusting actuation of the hydraulically actuated transmission component over a duration. The method further comprises, during the duration, isolating the accumulator from the hydraulically actuated transmission component when a pressure in the hydraulic circuit is above a threshold, and coupling the accumulator into the hydraulic circuit when the pressure is below the threshold.