Skip Fire Engine NVH Reduction via Smoothing Torque
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Solution Overview
Problem
Internal combustion engines generate unwanted noise, vibration, and harshness (NVH) due to the combustion process and cylinder firing, which can be transmitted to vehicle occupants and affect fuel efficiency, necessitating methods to reduce these undesirable effects.
Innovation Solution
A skip fire engine control system that applies a smoothing torque to the powertrain using an energy storage/release device, such as an electric motor/generator or flywheel, to mitigate NVH by canceling out torque variations, allowing for the use of firing fractions that would otherwise be unacceptable due to their NVH characteristics, while optimizing energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a skip fire firing sequence is used to improve fuel efficiency, then fuel economy is improved, but noise, vibration and harshness (NVH) increases
Solution Approach 1:
The control system applies a counteracting torque through the electric motor/generator that is specifically designed to oppose and cancel the torque variations generated by the skip fire firing sequence. This preliminary anti-action prevents the NVH from occurring rather than merely reducing it after the fact, allowing the skip fire sequence to maintain fuel efficiency while the counteracting torque maintains smooth operation.
Solution Approach 2:
The electric motor/generator serves as an intermediary device between the engine and the drivetrain. It absorbs the torque variations generated by the skip fire sequence and delivers smooth torque to the drivetrain, effectively mediating the conflict between fuel-efficient skip fire operation and smooth NVH performance.
2Use of energy by moving object
If firing fractions with unfavorable NVH characteristics are used to optimize energy efficiency, then energy efficiency is improved, but NVH increases
Solution Approach 1:
The system converts the harmful torque variations and NVH generated by specific firing fractions into a beneficial situation. By using the electric motor/generator to absorb and manage these variations, the system can operate at highly efficient firing fractions (such as 1/4 or 1/6 firing) that would normally be unacceptable, while the motor/generator transforms the potentially harmful irregular torque into smooth, controlled torque delivery.
3Object-generated harmful factors
If smoothing torque is applied to reduce NVH, then NVH is reduced, but device complexity increases
Solution Approach 1:
The electric motor/generator is utilized for multiple functions: it provides assist torque during acceleration, enables skip fire operation for fuel efficiency, and simultaneously acts as a smoothing device to reduce NVH. This multi-functionality reduces the need for separate dedicated NVH reduction devices, thereby limiting the increase in overall system complexity while achieving comprehensive performance improvements.
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
The smoothing torque effectively reduces NVH, enabling the use of more fuel-efficient firing fractions and improving overall engine performance by minimizing undesirable vibrations and noise, thereby enhancing the driving experience and fuel economy.
Implementation Method 1
A smoothing torque is determined that is applied to a powertrain by an energy storage/release device
Data Source
AI summary
A variety of methods and arrangements for reducing noise, vibration and harshness (NVH) in a skip fire engine control system are described. In one aspect, a firing sequence is used to operate the engine in a skip fire manner. A smoothing torque is determined that is applied to a powertrain by an energy storage/release device. The smoothing torque is arranged to at least partially cancel out variation in torque generated by the skip fire firing sequence. Various methods, powertrain controllers, arrangements and computer software related to the above operations are also described.