Hybrid Engine Shutdown NVH Control via Clutch Torque Transfer
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Solution Overview
Problem
Engine shutdown in automotive vehicles with engine start/stop systems can result in noise, vibration, and harshness due to resonance frequencies and energy transfer through engine mounts, affecting fuel economy and driving experience.
Innovation Solution
The method involves controlling the clutch to transfer torque between the engine and electric machine during shutdown, either by slowing the engine or speeding up the machine, to manage deceleration and reduce noise, vibration, and harshness by altering the natural deceleration rate of the engine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the engine is shut down to improve fuel economy, then fuel consumption is reduced, but noise, vibration, and harshness increase during shutdown
Solution Approach 1:
The clutch assembly acts as an intermediary between the engine and electric machine, enabling controlled torque transfer during shutdown. By gradually engaging the clutch, the system mediates the deceleration process, transferring torque from the rotating electric machine to the unpowered engine, thereby smoothing the shutdown and reducing NVH while maintaining fuel economy benefits
Solution Approach 2:
The system dynamically adjusts the clutch engagement state during shutdown, transitioning from disengaged to partially engaged based on real-time conditions. The clutch torque is modulated to control the rate of engine deceleration, ensuring the engine speed passes through resonance frequencies smoothly rather than abruptly, reducing vibration and harshness
2Object-affected harmful factors
If the clutch is engaged to transfer torque during shutdown, then deceleration is smoothed and NVH is reduced, but the shutdown process takes longer
Solution Approach 1:
The clutch is engaged partially rather than fully during shutdown, transferring only the necessary amount of torque to smooth deceleration. This partial engagement provides sufficient torque transfer to reduce NVH while avoiding excessive engagement that would unnecessarily extend the shutdown duration, optimizing the balance between comfort and time
3Loss of time
If the engine decelerates naturally without torque transfer, then the shutdown process is quick, but resonance frequencies cause increased vibration and harshness
Solution Approach 1:
The system applies preliminary anti-action by engaging the clutch before the engine completes its natural deceleration. The electric machine provides counter-torque through the clutch to oppose the natural deceleration that would cause the engine to pass through resonance frequencies abruptly, thereby preventing the generation of vibration and harshness before it occurs
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 noise, vibration, and harshness during engine shutdown, enhancing the driving experience and improving fuel economy by smoothing the shutdown process.
Implementation Method 1
controlling the clutch to transfer torque from the rotating machine to the unpowered engine
Implementation Method 2
noise, vibration, and harshness may result from the engine shutdown as an engine speed falls through a resonance frequency of the engine
Data Source
AI summary
A method of smoothing hybrid vehicle engine shutdown. A powered and rotating electric machine is used to slow deceleration of an unpowered and rotating engine by transferring torque through a clutch from the machine to the unpowered engine. Prior to the machine being powered, torque may be transferred through the clutch from the unpowered and rotating engine to the unpowered machine to accelerate passage of the engine through a resonance frequency.