Torque Converter Clutch Control for Engine Start-Stop Launch Delay
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Solution Overview
Problem
Engine start-stop powertrains experience delays in acceleration due to the slow establishment of torque throughput through the torque converter, especially when the engine is stationary, leading to a lag in vehicle motion during launch.
Innovation Solution
Incorporating an accumulator or auxiliary electric pump to provide pressurized hydraulic fluid for the torque converter lockup clutch, allowing immediate engagement and rapid torque transfer upon engine restart, and gradually reducing hydraulic pressure to increase slip for a smooth launch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine is stopped during idle (engine start-stop operation), then fuel economy is improved, but acceleration response and torque transfer are delayed
Solution Approach 1:
The torque converter clutch is engaged during the engine stop period, preparing the direct mechanical connection in advance. When the engine restarts, torque can be immediately transferred through the locked clutch without waiting for fluid coupling to build up, thus eliminating acceleration delay while maintaining fuel economy benefits
Solution Approach 2:
The torque converter clutch acts as an intermediary mechanical connection between the engine and transmission. By providing a direct locked connection, it mediates the torque transfer process, allowing immediate torque transmission upon engine restart while the engine is stopped during fuel-saving idle conditions
2Reliability
If the torque converter clutch is engaged during engine stop, then torque transfer is improved, but driveline isolation is reduced
Solution Approach 1:
The clutch engagement state is dynamically adjusted based on operating conditions. During engine stop, the clutch is engaged to ensure torque transfer readiness, but the system dynamically manages the engagement level and timing to maintain appropriate driveline isolation when needed, optimizing both torque transfer and isolation requirements
3Speed
If hydraulic pressure is maintained for clutch engagement, then clutch response is improved, but energy consumption increases
Solution Approach 1:
Hydraulic pressure is applied periodically rather than continuously - the auxiliary pump or accumulator provides pressurized fluid only during the brief period when clutch engagement is needed (during and immediately after engine restart). This periodic action achieves rapid clutch response while minimizing energy consumption compared to continuous pressurization
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 method significantly reduces startup delay, enabling vehicles to achieve acceleration in approximately one-fourth the time of conventional engine start-stop systems by ensuring prompt torque transfer and smooth engagement of the torque converter.
Implementation Method 1
an auxiliary electric pump is included to temporarily provide pressurized hydraulic fluid
Implementation Method 2
an accumulator or an auxiliary electric pump is included to temporarily provide pressurized hydraulic fluid
Implementation Method 3
torque throughput cannot be quickly established through the fluid coupling of the torque converter
Data Source
AI summary
A method of operating a torque converter clutch in an engine start-stop vehicle improves launch after an auto stop event. During the autostop event, hydraulic fluid is supplied to the torque converter clutch operator through one or more solenoid valves by an auxiliary electric pump. When the prime mover is started at the conclusion of the autostop event, the torque converter clutch is thus locked, assuring rapid and sufficient torque transfer through the torque converter to the transmission and improved acceleration during vehicle launch. As the vehicle accelerates, the hydraulic pressure in the clutch operator is reduced and slip through the clutch increased to achieve a smooth launch and return to conventional torque converter operation.