Liquid-Filled Bushing Protrusion Design for Spring Constant Ratio
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Solution Overview
Problem
Existing liquid-filled bushings, such as those used in automobiles, lack sufficient performance in terms of riding comfortability and steering stability due to inadequate differences in spring constants between the input direction of main vibrations and orthogonal directions.
Innovation Solution
A liquid-filled bushing design featuring an inner tube connected to a vibration generation or receiving portion, an outer member with liquid chambers and an orifice for communication, and an elastic body with protrusion portions that enhance the spring constant difference by elastic deformation and effective vibration damping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the liquid-filled bushing uses a conventional structure with inner and outer tubular bodies, then the basic vibration isolation function is achieved, but the spring constant difference between input direction and orthogonal direction is insufficient, resulting in inadequate riding comfortability and steering stability
Solution Approach 1:
The bushing is segmented into distinct functional zones: inner tubular body, outer tubular body, elastic body, and liquid chambers. The protrusion portions further segment the elastic body into regions with different stiffness characteristics, creating directional differences in spring constants while maintaining overall structural integrity
Solution Approach 2:
The protrusion portions are strategically positioned and dimensioned to create asymmetric stiffness distribution. The first protrusion portion has different dimensions than the second protrusion portion, and they are located at different positions along the axial direction, generating different spring constants in the input direction versus orthogonal directions. This asymmetric design directly addresses the insufficient spring constant difference in conventional bushings
2Reliability
If the liquid chambers are positioned to communicate through an orifice, then vibration damping is achieved, but the spring constant ratio between directions remains insufficient for high performance applications
Solution Approach 1:
Different regions of the elastic body are given different local qualities through the protrusion portions. The regions between the protrusion portions have different stiffness characteristics, allowing the bushing to provide appropriate vibration damping through the liquid chambers while simultaneously achieving high spring constant ratio in specific directions for improved performance adaptability
3Reliability
If protrusion portions are added to create spring constant difference, then riding comfortability and steering stability improve, but the device complexity increases
Solution Approach 1:
The protrusion portions are integrated directly into the elastic body as integral features rather than separate components. This merging approach creates the necessary spring constant differences while minimizing additional parts, thereby improving riding comfortability and steering stability without proportionally increasing device complexity
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 design achieves improved riding comfortability and steering stability by increasing the spring constant ratio between the input direction and orthogonal direction, effectively dampening and absorbing vibrations.
Implementation Method 1
an elastic body which elastically connects together the orifice portion and the inner tube
Implementation Method 2
a liquid-filled bushing, which includes an inner tubular body which is connected to one of a vibration generation source and a vibration receiving portion
Implementation Method 3
liquid is sealed in the pair of liquid chambers
Data Source
Figure 1
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Figure 3
AI summary
A liquid-filled bushing (1) includes an inner tube (11) and an outer member (12). The outer member (12) defines a pair of liquid chambers between the outer member (12) and the inner tube (11), and an orifice portion (13) in which an orifice passage (24) which communicates with the liquid chambers is formed. An elastic body (14) which elastically connects together the orifice portion (13) and the inner tube (11) is provided. The pair of liquid chambers are individually disposed on both sides between which the inner tube (11) is interposed. A first protrusion portion (11a) which protrudes outward in the radial direction and is fitted into the elastic body is formed in the inner tube (11), and a second protrusion portion (28) which protrudes inward in the radial direction and is fitted into the elastic body (14) is formed in the orifice portion (13). The first protrusion portion (11a) and the second protrusion portion (28) are disposed in both portions between the pair of liquid chambers adjacent in a circumferential direction such that positions of the portions in the circumferential direction coincide with each other and positions of the portions in the direction of the center axis are different from each other.