Variable Stiffness Bushing Assembly with Magnetorheological Fluid Control
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Solution Overview
Problem
Existing elastic bushing assemblies cannot vary stiffness based on both operating conditions and loading direction, limiting their ability to improve vehicle handling and reduce noise and vibration transmission.
Innovation Solution
A variable stiffness bushing assembly with magnetic fluid-filled chambers and coils that adjust viscosity in response to magnetic fields, allowing for independent control of stiffness in two orthogonal directions by varying the current through the coils.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the bushing member is formed with an opening to reduce stiffness for rearward loading, then ride quality is improved, but the ability to vary stiffness based on operating conditions is lost
Solution Approach 1:
The bushing assembly incorporates magnetic coils and magnetic fluid to enable dynamic adjustment of stiffness characteristics. The magnetic fluid's viscosity changes in response to magnetic fields generated by the coils, allowing the bushing to transition between different stiffness states based on operating conditions such as vehicle speed, steering angle, or road surface conditions, thereby resolving the contradiction between fixed low stiffness for ride comfort and the need for variable stiffness for adaptability
Solution Approach 2:
The invention changes the physical parameter of the damping medium from a fixed-viscosity fluid to a magnetic fluid whose viscosity can be altered by applying magnetic fields. By controlling the current through the magnetic coils, the viscosity of the magnetic fluid in the communication passages can be adjusted, thereby varying the stiffness of the bushing assembly to optimize both ride quality and handling performance under different operating conditions
2Stability of the object's composition
If the stiffness of the bushing assembly is increased to improve vehicle handling, then driving stability during cornering is improved, but noise and vibration transmission from the wheel to the vehicle body increases
Solution Approach 1:
The magnetic fluid's viscosity can be dynamically adjusted by controlling the magnetic field strength applied through the coils. During cornering or high-speed operations, increasing the magnetic field strength increases the fluid's viscosity, thereby increasing bushing stiffness to improve handling stability. During normal driving or when ride comfort is prioritized, reducing the magnetic field strength decreases viscosity and stiffness, thereby reducing noise and vibration transmission to the vehicle body
3Object-affected harmful factors
If the stiffness of the bushing assembly is decreased to minimize noise and vibration transmission, then ride quality is improved, but vehicle handling and driving stability deteriorate
Solution Approach 1:
The bushing assembly transitions from a static stiffness design to a dynamic stiffness control system. Sensors detect operating conditions such as steering angle, vehicle speed, and road surface information, and the control system adjusts the current through the magnetic coils accordingly. This enables the bushing to provide low stiffness for noise and vibration reduction during normal driving, while automatically increasing stiffness when handling stability is required, thus resolving the contradiction between these two performance requirements
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
Enables the bushing assembly to adaptively change stiffness in response to different loading conditions, enhancing vehicle handling and reducing noise and vibration transmission by selectively impeding magnetic fluid flow through communication passages.
Implementation Method 1
a magnetic fluid (50) having a viscosity that changes depending on an intensity of a magnetic field applied thereto
Implementation Method 2
a pair of coils (21) wound coaxially around respective parts of an outer periphery of the inner yoke located on either side of the annular large diameter portion so as to generate magnetic fields directed in mutually opposing directions
Data Source
AI summary
A variable stiffness bushing assembly includes an inner tubular member, an outer tubular member coaxially surrounding the inner tubular member, and an elastic member connecting the inner and outer tubular members. The elastic member defines a pair of first liquid chambers that are on opposite sides of an axial line of the inner tubular member and communicate with each other via a first circumferentially extending communication passage defined between one of the outer yokes and the annular large diameter portion, and a pair of second liquid chambers that are on opposite sides of the axial line and communicate with each other via a second circumferentially extending communication passage defined between another one of the outer yokes and the annular large diameter portion. The magnetic fields generated by the two coils are selectively applied to a magnetic fluid flowing through the first communication passage and the second communication passage.