Latching Valve Control for Automatic Stop-Start Transmission Readiness
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Solution Overview
Problem
Existing automatic transmission systems face challenges in controlling engine stop-start functions while maintaining timely shifting and quick system recovery, particularly due to fluid drainage and pressure loss when the engine is shut down, which affects fuel efficiency and operational readiness.
Innovation Solution
A system and method that utilize latching valves in clutch control circuits to manage engine stop-start operations by determining conditions for autostop, adjusting line pressure and clutch control pressure to enable or disable latching, ensuring timely latching and unlatching of torque transmitting mechanisms to maintain hydraulic fluid pressure and facilitate quick system recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine is stopped during idle or red light to improve fuel economy, then fuel efficiency is improved, but transmission pressure is lost and system recovery time increases
Solution Approach 1:
The latching valve is activated before engine shutdown to trap hydraulic fluid pressure in the clutch circuit. This preliminary action ensures that when the engine stops and pump pressure is lost, the clutch remains engaged due to the trapped pressure, eliminating the need for system recovery after engine restart
Solution Approach 2:
The latching valve acts as an intermediary component between the pump pressure source and the clutch. It selectively traps or releases hydraulic fluid to maintain clutch engagement during engine stop-start operations, mediating between the need for fuel efficiency and transmission operational readiness
2Reliability
If hydraulic fluid pressure is maintained in the clutch during engine shutdown, then quick system recovery is achieved, but clutch pressure cannot be eliminated when needed for gear shifts
Solution Approach 1:
The latching valve provides dynamic control over hydraulic fluid trapping. It can be activated to trap pressure for maintaining clutch engagement during idle stop-start, and deactivated to allow pressure equalization when gear shifts are required. This dynamic switching capability enables the system to adapt between maintaining transmission readiness and enabling gear shifting operations
3Extent of automation
If latching valve is activated to maintain clutch pressure during autostop, then engine stop-start control is improved, but additional control complexity is introduced
Solution Approach 1:
The latching valve control is integrated with the existing engine stop-start control logic. The same controller that manages engine shutdown/start also activates the latching valve, combining multiple functions into a unified control system rather than adding a separate independent control mechanism
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
Enables efficient engine stop-start control, maintaining transmission readiness and improving fuel efficiency by ensuring hydraulic fluid pressure is maintained during engine shutdown and restored quickly upon restart, while allowing for fluid drainage when necessary, such as when shifting to reverse gear.
Implementation Method 1
The latching valve is configured to selectively trap pressurized hydraulic fluid within the torque transmitting device
Implementation Method 2
after the engine has been shut down and has remained off for an extended period of time, the fluid generally tends to drain down from the passages into a transmission sump under the force of gravity
Data Source
AI summary
A system and method are provided for controlling an automatic engine stop-start in conjunction with a transmission having one or more latching valves. The system and method is configured to determine whether conditions are met for an autostop, and if so, to latch or unlatch the latching valve(s) by changing clutch pressure.