Flexure Engine Mount With Radial-Axial Stiffness Control
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Solution Overview
Problem
Conventional compliant engine mounts used in vehicles, particularly in aircraft, face challenges in reducing vibration and force transmission while minimizing excessive deflections and deformations, due to the compression 'set' and creep characteristics of elastomeric materials, which require additional design compromises to maintain effective vibration isolation over time.
Innovation Solution
The engine mount device incorporates a housing with a carrier and flexures that provide higher stiffness in radial directions compared to axial directions, utilizing a trunnion pin mechanism and elastomeric material to reduce vibration transmission and allow for axial movement, while snubbing surfaces prevent excessive deflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If elastomeric materials are used in compliant mounts to compensate for larger ranges of motion, then vibration and force transmission is reduced, but the elastomeric materials develop compression set and creep over time, requiring additional design compromises
Solution Approach 1:
The patent changes the material parameters by transitioning from elastomeric materials to metal flexures, which have superior dimensional stability and do not exhibit compression set or creep. This parameter change maintains vibration isolation effectiveness while eliminating the degradation issues associated with elastomeric materials over time.
Solution Approach 2:
The patent employs composite construction by combining metal flexures with snubbing elements (springs and dampers) to create a hybrid system. The metal flexures provide structural stability and load-bearing capacity, while the snubbing elements provide vibration damping, achieving both reliability and dimensional stability.
2Stability of the object's composition
If stops (snubbing elements) are incorporated in conjunction with elastomers to minimize excessive deflections, then motion is controlled, but the stops must be designed to accommodate elastomeric material set and creep throughout operational life
Solution Approach 1:
The patent inverts the conventional approach by making the primary motion-control element (flexure) rigid and stable, rather than compliant and degradable. The snubbing elements become the secondary, supplemental component rather than the primary motion controller, simplifying the design since the metal flexure does not require accommodation for material degradation.
Solution Approach 2:
The patent treats the snubbing elements as replaceable, secondary components that handle only exceptional conditions (excessive motion), while the primary metal flexure provides long-term stable operation. This reduces overall design complexity by separating the primary function from the protective function.
3Reliability
If conventional compliant mounting systems are used to reduce vibration transmission, then vibration and force transmission is reduced, but static displacement of the supported structure increases
Solution Approach 1:
The patent changes the stiffness parameter by using metal flexures with higher material modulus compared to elastomeric materials. This allows the mount to maintain lower static displacement while still providing effective vibration transmission reduction, as the metal flexure can be designed with appropriate geometric stiffness characteristics.
Solution Approach 2:
The patent applies local quality by creating anisotropic stiffness characteristics in the metal flexure design, providing different stiffness levels in different directions. The flexure can be designed to be stiffer in directions where static displacement control is critical while maintaining compliance in directions where vibration isolation is most needed.
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 and force transmission to the vehicle, maintaining compliant behavior over the engine mount's life without engaging snubbing elements at lower deflection levels, thereby addressing the limitations of conventional mounts.
Implementation Method 1
at least one flexure connecting the carrier to the housing. The at least one flexure is configured to provide higher stiffness in one or more radial directions of the hole compared to a stiffness provided in an axial direction of the hole
Implementation Method 2
Conventional compliant mounts often incorporate elastomers because of their ability to compensate and control larger ranges of motion with softer spring rates
Data Source
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.