Hybrid Engine Start Torque Control for Gear Lash Noise
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Solution Overview
Problem
Hybrid vehicles face challenges in reducing driveline noise during engine starting, particularly due to gear lash crossing and torque transfer changes.
Innovation Solution
A method involving a controller to rotate the engine beyond a threshold speed using torque from a first electric machine through a planetary carrier gear set and sun gear, then reducing the electric machine's torque output as the engine speed exceeds the threshold, and adjusting torque further during gear lash crossing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the generator is used to start the engine, then the engine can be started successfully, but driveline noise increases
Solution Approach 1:
The method applies preliminary action by pre-positioning the engine speed above the threshold speed before the gear lash crossing event occurs. The controller monitors engine speed and adjusts generator torque to ensure the engine is already rotating fast enough before the torque direction changes, thereby preventing the gear teeth from impacting and reducing noise during the lash crossing.
Solution Approach 2:
The system dynamically adjusts generator torque based on real-time engine speed conditions. The controller continuously monitors engine speed and modulates the generator torque output to maintain optimal operating conditions, specifically keeping engine speed above the threshold during critical phases of operation to prevent gear lash noise while ensuring reliable starting.
2Reliability
If torque is delivered to the engine via gears to start the engine, then the engine can be started, but gear teeth generate noise when torque direction changes
Solution Approach 1:
The controller prepositions the engine speed above the threshold before the gear lash crossing event. By ensuring the engine is already rotating sufficiently fast before the torque direction changes in the gear train, the method prevents the gear teeth from impacting each other, thereby eliminating gear noise while maintaining reliable starting capability.
Solution Approach 2:
The method applies preliminary anti-action by proactively preventing the gear lash crossing noise condition from occurring. The controller anticipates the torque direction change and adjusts engine speed in advance to remain above the threshold, thereby counteracting the potential harmful effect of gear tooth impact before it can occur.
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 likelihood of noise generation during engine starting by managing torque transfer and speed differences between gears, enhancing starting repeatability and reducing driveline wear.
Implementation Method 1
rotating the engine to a speed greater than a threshold speed via transferring torque from a first electric machine through a planetary carrier gear set and a sun gear to the engine
Implementation Method 2
transferring torque from a first electric machine through a planetary carrier gear set and a sun gear to the engine
Data Source
AI summary
Systems and methods for operating an internal combustion engine that is coupled to a power split transmission are described. In one example, the internal combustion engine is cranked via a generator and torque output of the generator is adjusted to reduce noise that may be generated by completing a gear lash crossing.