Lock-up clutch hydraulic pressure control for vehicle sailing stop
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Solution Overview
Problem
Conventional vehicle sailing stop control devices experience a time lag when transitioning from coasting to normal traveling due to a higher required flow rate when the clutch is released, leading to delayed engagement of the forward clutch.
Innovation Solution
A vehicle sailing stop control method and device that uses a torque converter with a lock-up clutch, where hydraulic pressure is applied to the lock-up clutch during coasting, maintaining it in a power transmission state, reducing the flow rate required for engaging the friction engagement element and shortening the time to reach a power transmission state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the clutch is maintained in a released state during coasting, then the sailing stop control can be properly executed, but the required flow rate increases and causes time lag when engaging the forward clutch
Solution Approach 1:
The lock-up clutch is engaged before the forward clutch engagement is needed, during the coasting period. This preliminary engagement maintains hydraulic pressure in the system and ensures that when the forward clutch needs to engage, the hydraulic pressure is already available, eliminating the time lag. The lock-up clutch serves as a preparatory measure to keep the hydraulic system ready.
Solution Approach 2:
The lock-up clutch acts as an intermediary element between the hydraulic pressure source and the forward clutch. By maintaining engagement of the lock-up clutch during coasting, it preserves hydraulic pressure in the system, which then serves as a ready supply when the forward clutch needs to engage, mediating the pressure transfer without time loss.
2Quantity of substance
If the lock-up clutch is engaged during coasting, then the required flow rate is reduced, but additional control complexity is introduced
Solution Approach 1:
The lock-up clutch, originally designed for torque converter lock-up functionality, is given an additional function of maintaining hydraulic pressure during coasting operations. This multi-functionality allows the same component to serve both its traditional purpose and the new purpose of flow rate management, avoiding additional system complexity.
Solution Approach 2:
The lock-up clutch engagement during coasting automatically maintains hydraulic pressure in the system as a byproduct of its engagement state. The system self-regulates the hydraulic pressure availability without requiring separate control mechanisms, as the lock-up clutch's engagement naturally preserves the pressure needed for subsequent forward clutch engagement.
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 reduces the time lag when leaving sailing stop control, allowing for quicker engagement of the friction engagement element and improving drivability by maintaining a lower required flow rate and hydraulic pressure, thus enhancing fuel efficiency.
Implementation Method 1
a torque converter disposed between the friction engagement element and the traveling drive source, and provided with a lock-up clutch for which the power transmission amount is controlled based on hydraulic pressure
Implementation Method 2
while coasting with the sailing stop control, there is a state for which hydraulic pressure is applied to the lock-up clutch so that the lock-up clutch is in a power transmission state
Data Source
AI summary
A vehicle sailing stop control method is provided for a vehicle including a friction engagement element disposed between a traveling drive source and drive wheels, a torque converter disposed between the friction engagement element and the traveling drive source, and including a lock-up clutch for which a power transmission amount is controlled based on hydraulic pressure, and a hydraulic pressure source that can supply the hydraulic pressure while the traveling drive source is stopped. The vehicle sailing stop control method includes: performing sailing stop control so that coasting is performed by cutting off power transmission of the friction engagement element and stopping the traveling drive source upon a sailing stop travel condition being established; and, during coasting by the sailing stop control, placing the lock-up clutch in a power transmission state in which the hydraulic pressure is applied to the lock-up clutch.