Dual Flywheel Engine Assembly for NVH Reduction
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Solution Overview
Problem
Internal combustion engines, particularly single-cylinder engines, face challenges in reducing noise, vibration, and harshness (NVH) due to unbalanced forces from combustion cycle impulses, which existing flywheel systems do not adequately address, while multi-cylinder engines increase complexity and frictional losses.
Innovation Solution
The implementation of a dual flywheel system with a clutch mechanism that disconnects the flywheel from the crankshaft at high speeds, along with a gear ratio that allows the second flywheel to rotate faster and have a smaller mass, effectively smoothing out combustion cycle impulses and reducing NVH by balancing angular kinetic energies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single cylinder engine is used, then device complexity is reduced, but noise, vibration and harshness (NVH) increases
Solution Approach 1:
The patent divides the traditional single flywheel system into two separate flywheels (first flywheel and second flywheel) rotating in opposite directions. This segmentation allows each flywheel to counterbalance the combustion impulses independently, reducing NVH while maintaining the simplicity of a single-cylinder engine design.
Solution Approach 2:
The second flywheel acts as a counterweight system that rotates in the opposite direction to the first flywheel. The opposing rotational directions create counterbalancing forces that neutralize the combustion cycle impulses and reduce the unopposed couple on the engine block, thereby reducing NVH.
2Object-generated harmful factors
If a multi-cylinder engine is used, then NVH is reduced, but device complexity and frictional losses increase
Solution Approach 1:
Instead of using multiple cylinders, the patent segments the flywheel system into two independently rotating flywheels. This approach achieves the NVH reduction effect of multi-cylinder engines (by distributing and balancing combustion impulses) while maintaining the mechanical simplicity of a single-cylinder configuration.
Solution Approach 2:
The patent inverts the conventional approach by having the second flywheel rotate in the opposite direction to the crankshaft and first flywheel. This reverse rotation creates counterbalancing effects that reduce NVH without requiring additional cylinders or increasing engine complexity.
3Device complexity
If a traditional single flywheel is used, then device complexity is low, but angular kinetic energy balancing is insufficient
Solution Approach 1:
The patent segments the kinetic energy storage function into two separate flywheels rotating in opposite directions. This segmentation allows for better distribution and balancing of angular kinetic energy throughout the engine cycle, providing smoother operation while keeping the overall system complexity manageable.
Solution Approach 2:
The patent changes the rotational direction parameter of the second flywheel to be opposite to the first flywheel. This parameter change enables the system to balance angular kinetic energy more effectively by creating opposing rotational energies that cancel out fluctuations during the combustion cycle.
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 configuration reduces NVH by balancing the angular kinetic energies of the engine components, providing smoother operation and reduced frictional losses, while maintaining a compact design and lower mass compared to conventional single flywheel systems.
Implementation Method 1
an angular kinetic energy of components of the engine assembly turning in the second direction is generally equal to an angular kinetic energy of components of the engine assembly turning in the first direction when the first and second flywheels are rotating
Implementation Method 2
The clutch includes a clutch disc, a pressure plate, and a release bearing. The pressure plate is biased toward the clutch disc by a diaphragm spring to frictionally engage the clutch disc to the drive shaft
Data Source
AI summary
An internal combustion engine assembly has a crankcase, a cylinder block connected to the crankcase, the cylinder block defining at least one cylinder, at least one piston disposed in the at least one cylinder, a crankshaft disposed at least in part in the crankcase and operatively connected to the at least one piston, and a flywheel operatively connected to and driven by the crankshaft. The crankshaft rotates in a first direction about a crankshaft axis. The flywheel rotates in a second direction opposite the first direction about the flywheel axis. A clutch selectively operatively connects the crankshaft to the flywheel. A marine outboard engine having the internal combustion engine assembly is also disclosed.