Crankcase Dynamic Damper Layout for Crankshaft Bending Vibration
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Solution Overview
Problem
Existing engines face challenges in fabricating dynamic dampers for crankshafts rotating at high speeds, as the antivibration performance is difficult to set due to varying crankcase rigidity and noise transmission issues, leading to excessive noise generation.
Innovation Solution
A dynamic damper is provided in the crankcase with a damper mass supported by an elastic object, vibrating on a straight line orthogonal to the crankshaft's center axis, absorbing bending vibrations efficiently, and using leaf spring portions to restrict vibration direction without excessive space, with rubber members for additional absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the dynamic damper is provided at the crankshaft rotating at high speed, then the antivibration performance can be set, but the degree of freedom in design and attachment is restricted and fabrication becomes difficult
Solution Approach 1:
The dynamic damper is extracted from the crankshaft and relocated to the crankcase. This separation allows the crankshaft to rotate at high speed without the complexity of attaching a dynamic damper directly to it, while the damper remains effective at absorbing vibrations transmitted to the crankcase.
Solution Approach 2:
The crankcase serves as an intermediary structure between the crankshaft and the dynamic damper. The damper is attached to the crankcase, which itself is connected to the crankshaft, allowing vibration transmission to be intercepted and absorbed without direct attachment to the rotating crankshaft.
2Reliability
If the dynamic damper is provided at the crankshaft, then vibration can be reduced, but the vibration may still be transmitted to the crankcase and generate excessive noise
Solution Approach 1:
The vibration that would otherwise be transmitted to the crankcase and generate noise is instead captured and converted into beneficial damping action. The dynamic damper absorbs the vibrational energy, converting it into heat through internal friction within the damping material, thereby preventing noise generation.
Solution Approach 2:
The vibration transmission path to the crankcase is interrupted by extracting and absorbing the vibrational energy at the dynamic damper located on the crankcase, preventing the harmful vibration from reaching the crankcase and its peripheral members.
3Object-generated harmful factors
If the rigidity of the crankcase is increased to reduce noise, then noise transmission is reduced, but the design flexibility and adaptability are restricted
Solution Approach 1:
The noise reduction function is extracted from the crankcase structure itself and assigned to a separate dynamic damper component. This allows the crankcase to maintain its original rigidity and design characteristics while the damper independently handles vibration absorption and noise reduction.
Solution Approach 2:
Instead of making the crankcase statically rigid to reduce noise, a dynamic damper with controlled elasticity is introduced. The damper's elastic properties allow it to dynamically respond to and absorb vibrations, providing noise reduction without compromising the overall structural integrity or design flexibility of the crankcase.
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 solution facilitates easy fabrication and significantly reduces noise generation by effectively absorbing vibrations transmitted to the crankcase and its peripherals, improving design freedom and stability.
Implementation Method 1
a supporter that has an elastic object, and vibratably supports the damper mass at the crankcase such that the damper mass is vibratable by the elastic object on one straight line that is orthogonal to a center axis of the crankshaft
Implementation Method 2
the damper mass of the dynamic damper vibrates on the one straight line parallel to the direction of the bending vibration of the crankshaft. Thus, the vibration transmitted to the peripheral members of the crankshaft due to the bending vibration of the crankshaft is efficiently absorbed by the dynamic damper
Implementation Method 3
The rubber member absorbs the vibration of the damper mass caused by the elastic forces of the first leaf spring portion and the second leaf spring portion
Data Source
Figure 1
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AI summary
A power unit 6 includes an engine 6A. The engine 6A has a crankshaft 61. Further, the engine 6A has a crankcase 62 accommodating the crankshaft 61. A dynamic damper 200 is provided in the crankcase 62. The dynamic damper 200 includes a damper mass 210 and a support member. The support member 220 includes an elastic object and supports the damper mass 210 at the crankcase 61. During an operation of the engine 6A, bending vibration is generated in the crankshaft 61. At this time, the damper mass 210 vibrates on one straight line that is orthogonal to a center axis of the crankshaft 61 and parallel to a direction of bending vibration generated in the crankshaft 61.