Variable Volume Fluid Spring for Vehicle Roll Stiffness Control
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Solution Overview
Problem
Existing air spring systems in vehicles face issues such as increased roll stiffness and non-linear spring rate due to heat transfer effects, leading to degraded ride and handling performance, particularly during cornering maneuvers.
Innovation Solution
A continuously variable rate fluid spring system is introduced, comprising a fluid spring with a variable volume unit and an actuator that adjusts the fluid cavity volume, controlled by a controller to independently manage spring rates across different driving modes, thereby maintaining optimal ride height and handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If air spring volume is adjusted to maintain trim height, then vehicle leveling is improved, but spring rate becomes non-linear and roll stiffness increases due to heat transfer effects
Solution Approach 1:
The air spring system is segmented into two independent volume control mechanisms: a main air chamber for trim height maintenance and a variable volume cavity for spring rate control. This segmentation allows independent adjustment of each function, resolving the conflict between maintaining stable trim height and preventing harmful heat transfer effects that increase roll stiffness.
Solution Approach 2:
The system dynamically changes the physical parameters of the air spring by adjusting the volume of the variable volume cavity through piston displacement. This parameter change compensates for heat transfer effects during cornering maneuvers, maintaining optimal spring rates and reducing unwanted roll stiffness increases while preserving trim height stability.
2Ease of operation
If spring rate is reduced to improve ride quality when vehicle is unloaded, then ride comfort is improved, but vehicle roll stability deteriorates
Solution Approach 1:
The system implements dynamic spring rate adjustment through the variable volume cavity that can change its volume in real-time based on vehicle operating conditions. This dynamic adjustment allows the spring rate to be optimized for ride comfort when unloaded while maintaining adequate roll stability when needed, resolving the static trade-off between these two requirements.
Solution Approach 2:
The system changes the spring rate parameter dynamically by adjusting the volume of the variable volume cavity. During cornering maneuvers, the controller adjusts the cavity volume to compensate for heat transfer effects and maintain appropriate roll stiffness, while allowing lower spring rates during normal operation for improved ride quality.
3Adaptability or versatility
If four corner leveling control is used to dynamically adjust trim heights, then vehicle performance is improved, but device complexity increases
Solution Approach 1:
The variable volume cavity with piston and actuator serves multiple functions: it controls spring rate to compensate for heat transfer effects, maintains trim height, and adjusts vehicle level. This multi-functionality reduces the need for separate dedicated components for each function, thereby reducing overall device complexity while maintaining dynamic adaptability.
Solution Approach 2:
The system merges the trim height maintenance function and the spring rate control function into a single integrated air spring assembly with the variable volume cavity. This consolidation combines multiple functions into one component, reducing the number of separate parts and simplifying the overall system architecture while maintaining the ability to dynamically adjust trim heights.
4Force
If air mass is added or removed to adjust spring rate, then spring rate control is achieved, but response time is slow due to compressor and valve operations
Solution Approach 1:
The system replaces the slow mechanical air mass transfer process (compressor and valve operations) with a faster mechanical displacement mechanism. The piston directly displaces air within the variable volume cavity, providing rapid spring rate adjustment without the delays inherent in compressor cycling and valve operations.
Solution Approach 2:
The variable volume cavity acts as an intermediary mechanism between the actuator and the main air spring. Instead of directly adding or removing air mass from the air spring, the actuator adjusts the cavity volume to indirectly control the spring rate, providing faster and more precise control response.
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 solution provides enhanced control over spring rates, improving ride comfort and handling by compensating for heat transfer effects and allowing for dynamic adjustment of spring rates based on driving conditions, reducing the need for additional components like rebound springs.
Implementation Method 1
The fluid cavity is in fluid communication with the fluid chamber
Implementation Method 2
a resilient biasing member adapted to exert a biasing force between the piston and the rigid piston cylinder assisting the actuator when driving the piston into the rigid piston cylinder decreasing the volume of the fluid cavity
Implementation Method 3
a first fluid spring and a first variable volume unit. The first fluid spring includes a fluid chamber adapted to change in volume
Data Source
AI summary
A vehicle fluid spring system is adapted to absorb road shock imparted onto at least one road wheel of a vehicle. The vehicle fluid spring system includes a fluid spring and a variable volume unit. The fluid spring includes a fluid chamber adapted to change in volume. The variable volume unit including a rigid piston cylinder, a piston, a fluid cavity, and an actuator. The piston is adapted to reciprocate within, and is in sliding contact with, the rigid piston cylinder. The fluid cavity is defined by the piston cylinder and the piston. The actuator is adapted to drive the piston changing a volume of the fluid cavity. The fluid cavity is in fluid communication with the fluid chamber.