Torque Converter K-Factor Control for Driveline Lash Mitigation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Modern vehicle propulsion systems with engine start-stop technology experience undesirable driveline lash or clunk due to gear lash resulting from manufacturing clearances and component design, particularly when the engine is shut off and restarted, leading to a negative torque motion followed by a positive torque motion.
Innovation Solution
The method involves controlling the K-factor in the torque converter coupling to increase coupling force between torque converter components within a half second of engine restart, pre-tightening driveline components before significant torque production, thereby minimizing lash by decreasing the K-factor and then increasing it in the torque converter coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the engine is stopped during vehicle operation to improve fuel economy, then fuel consumption is reduced, but driveline lash and clunk occur during engine restart
Solution Approach 1:
The control system pre-tightens the driveline components by applying torque to the torque converter before the engine restarts. This preliminary action eliminates clearances in the drivetrain, so when the engine restarts and produces torque, the lash bump is minimized because the components are already in contact on the driving side.
Solution Approach 2:
The system applies a preliminary torque in the opposite direction to counteract the expected lash bump. By decreasing the K-factor and applying reverse torque through the torque converter before restart, the driveline components are pre-loaded to prevent the negative torque motion that causes lash and clunk during engine restart.
2Object-affected harmful factors
If the driveline components are pre-tightened by spinning the propulsion system to minimize lash, then driveline lash is reduced, but additional energy is consumed during engine restart
Solution Approach 1:
The control system dynamically changes the K-factor parameter of the torque converter to optimize the balance between lash mitigation and energy consumption. By adjusting the K-factor to decrease initially (for pre-tightening) and then increase (for normal operation), the system minimizes lash while managing the energy required for the restart process.
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 effectively mitigates driveline lash and clunk during engine restarts, ensuring a smoother vehicle operation by tightening the driveline components before positive torque production, reducing the disturbance caused by torque changes.
Implementation Method 1
The impeller is configured to form a fluid coupling with the turbine
Data Source
AI summary
A motor vehicle propulsion system, an engine control system, and a method for starting an engine of a motor vehicle system are provided, which are configured to request an engine restart after stopping the engine, decrease a K-factor in a torque converter coupling within 1.5 seconds of requesting the engine restart, and to increase the K-factor in the torque converter coupling to minimize the lash and disturbance between interconnecting components in a vehicle system during negative torque vehicle driving to positive torque propulsion system driving transitions where a torque converter exists.