Flexure Engine Mount With Directional Stiffness for Vibration Isolation
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Solution Overview
Problem
Conventional compliant engine mounts face challenges in reducing vibration and force transmission while controlling static displacement, as elastomeric materials exhibit compression 'set' and 'creep' over time, requiring additional design compromises to manage motion and prevent excessive deflections.
Innovation Solution
The engine mount device features a housing with a carrier and a flexure that provides higher stiffness in radial directions than in axial directions, utilizing a stadium-shaped flexure with elastomeric material for vibration isolation and damping, and snubbing surfaces to limit deflections, allowing for axial movement while maintaining structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If elastomeric materials are used in conventional compliant mounts to reduce vibration and force transmission, then vibration isolation capability is improved, but compression set and creep occur over time requiring additional design compromises
Solution Approach 1:
The elastomeric material is segmented into multiple discrete elements (first, second, and third elastomeric elements) arranged in series between the engine and airframe. This segmentation allows each element to be optimized for specific functions: the first element provides primary vibration isolation, the second element compensates for compression set, and the third element handles creep, collectively improving reliability while maintaining vibration isolation
Solution Approach 2:
The patent changes the physical parameters of the elastomeric material by using multiple elements with different durometers, cross-sectional areas, and lengths. The first element has higher durometer for rigid support, while subsequent elements have lower durometers for compliance. This parameter variation allows the system to maintain vibration isolation performance while compensating for time-dependent degradation
2Stability of the object's composition
If conventional compliant mounting systems are designed to control static displacement, then motion control is improved, but vibration and force transmission reduction is compromised
Solution Approach 1:
The elastomeric isolation system is divided into multiple segmented elements arranged in series, where each segment serves a specific function: the first element provides rigid support for static displacement control, while the second and third elements provide progressive compliance for vibration isolation. This segmentation enables simultaneous achievement of both static stability and dynamic vibration reduction
Solution Approach 2:
The patent creates a composite elastomeric system combining multiple elastomeric elements with different material properties (durometer, cross-sectional area, length) to achieve a composite effect that simultaneously provides static displacement control and vibration isolation, resolving the contradiction between stability and harmful factor reduction
3Strength
If stops are incorporated in conjunction with elastomers to minimize excessive deflections, then deflection control is improved, but additional motion control capability is required to accommodate set and creep
Solution Approach 1:
The patent incorporates stops positioned to engage before excessive deflections can occur, providing beforehand cushioning against over-deflection. The stops are strategically located to accommodate the expected compression set and creep of the elastomeric elements, allowing the system to maintain deflection control without requiring additional complex motion control mechanisms
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 effectively reduces vibration transmission and force transfer, maintaining desired compliant behavior over the engine mount's life without premature wear, while accommodating 'set' and 'creep' of elastomeric materials, ensuring efficient vibration isolation and structural stability.
Implementation Method 1
deformation of the flexure reduces the transmission of vibration from the engine to the airframe
Implementation Method 2
the tendency of such elastomeric materials to take on a compression 'set' (e.g., the amount by which an elastomeric material fails to return to its original form after release from reacting a prolonged static compressive load)
Implementation Method 3
to exhibit characteristics of 'creep' (e.g., the time-dependent part of a strain resulting from stress) over time when such elastomeric materials are loaded
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
An engine mount device includes a housing, a carrier within a cavity in the housing, and a flexure flexibly connecting the carrier to the housing, with a pin disposed in a hole in the carrier to support an engine. A method of providing isolation in the engine mount device includes transmitting a force from the pin into the carrier; mechanically isolating the carrier from the housing via the flexure; and providing, via the flexure, a higher stiffness in one or more radial directions of the hole compared to a stiffness provided in an axial direction of the hole.