Automatic Engine Restart Hydraulic Pressure Control
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Solution Overview
Problem
Conventional automatic transmission systems experience slippage and delay during engine restarts due to hydraulic fluid pressure drop when the engine is stopped, leading to inefficient engagement of torque transmitting devices.
Innovation Solution
A system and method that controls automatic engine restarts by using an accumulator to maintain hydraulic fluid pressure, allowing a minimum number of torque transmitting devices to be primed based on accelerator pedal position, thereby reducing the time required for reengagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the engine is stopped to increase fuel economy, then fuel consumption is reduced, but hydraulic fluid pressure drops causing slippage and delay during restart
Solution Approach 1:
The system pre-pressurizes selected torque transmitting devices before engine shutdown and maintains pressure through an accumulator during the stop period. This preliminary action ensures that when the engine restarts, the pre-pressurized clutches engage immediately without slippage or delay, resolving the time loss issue while maintaining fuel economy benefits
2Speed
If all torque transmitting devices are pre-pressurized during engine stop, then engagement speed is improved, but hydraulic fluid consumption increases
Solution Approach 1:
Instead of uniformly pre-pressurizing all torque transmitting devices, the system selectively applies pressure only to specific clutches based on the current operating conditions and predicted restart requirements. This localized approach maintains engagement speed for critical components while minimizing hydraulic fluid consumption across the entire system
3Reliability
If hydraulic pressure is maintained in all clutches during engine stop, then reliability of engagement is improved, but device complexity increases
Solution Approach 1:
The hydraulic control system is segmented into multiple independent circuits, each serving specific torque transmitting devices. During engine stop, only the necessary segments are pressurized based on operational requirements. This segmentation maintains engagement reliability for critical paths while simplifying the overall system by avoiding unnecessary pressurization of all components
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 minimizes slippage and delay during engine restarts by ensuring timely and efficient engagement of torque transmitting devices, enhancing vehicle controllability and fuel efficiency.
Implementation Method 1
A controller within the transmission is configured to control an automatic restart of the engine based on a state of the transmission and/or motor vehicle. In addition, the controller is configured to control torque transmitting devices within the transmission such that a minimum number of the torque transmitting devices are filled with hydraulic fluid during an automatic restart of the engine. The system and method uses an accumulator to maintain hydraulic fluid pressure
Data Source
AI summary
A system and method for controlling automatic stop-start of a motor vehicle is provided. The system and method is configured to enable an automatic stop-start mode of operation that minimizes clutch fill during engine restart.