Vehicle Suspension Geometry Optimizing Scuff Damping Ratio
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Solution Overview
Problem
Conventional vehicle suspension systems face challenges in achieving both improved fuel economy and driving/braking performance while maintaining steering stability and riding comfort, particularly when the tire longitudinal spring constant is reduced, leading to deterioration in damping performance and comfort issues.
Innovation Solution
A method for designing a vehicle suspension device that adjusts the scuff change-based apparent damping coefficient to critical damping coefficient ratio within specific limits, ensuring adequate damping force and preventing excessive damping rates, thereby aligning with the tire longitudinal spring constant for enhanced steering stability and comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the tire longitudinal spring constant is reduced to increase tire ground contact area, then fuel economy performance improves, but up-down directional damping performance deteriorates
Solution Approach 1:
The invention changes the geometric parameters of the suspension device (specifically the relationship between roll center height h and tread T) to adjust the scuff change characteristics. By setting the ratio h/T within a specific range, the suspension generates appropriate scuff change with stroke, which provides the necessary damping effect to compensate for the reduced tire longitudinal spring constant, thereby maintaining damping performance while allowing lower spring constants for improved fuel economy.
2Loss of energy
If the tire longitudinal spring constant is reduced to improve fuel economy, then tire rolling resistance decreases, but riding comfort deteriorates due to insufficient damping force
Solution Approach 1:
The invention adjusts the suspension geometry parameters (roll center height h and tread T ratio) to optimize scuff change characteristics, generating appropriate damping forces during wheel stroke that compensate for the reduced tire damping capacity, thereby maintaining riding comfort despite lower tire rolling resistance.
Solution Approach 2:
The invention utilizes the dynamic scuff change that occurs during wheel stroke through the optimized suspension geometry. The changing relationship between roll center height and tread during suspension movement creates a dynamic damping effect that adapts to varying wheel positions and road conditions, providing consistent riding comfort.
3Stability of the object's composition
If the scuff change-based apparent damping coefficient is increased to improve damping performance, then steering stability improves, but the damping ratio becomes excessive causing harsh ride
Solution Approach 1:
The invention precisely controls the ratio of roll center height h to tread T within a specific range to optimize the scuff change characteristics. This controlled parameter adjustment ensures that the apparent damping coefficient provides sufficient steering stability while preventing excessive damping ratios that would cause harsh ride quality.
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 method effectively maintains excellent steering stability and good riding comfort by optimizing the scuff change-based damping ratio, ensuring the damping force is sufficient yet not excessive, even with reduced tire longitudinal spring constants, thus addressing the limitations of conventional systems.
Implementation Method 1
a shock absorber extending in a vehicle up-down direction and having an upper end attached to the vehicle body and a lower end attached to one of the coupling members or the wheel supporting member
Data Source
Figure 1~3
Figure 4~6
AI summary
Provided is a vehicle suspension device capable of obtaining excellent steering stability and good riding comfort in conformity to a tire longitudinal spring constant. The suspension device (1) comprises: an upper arm (2); a lower arm (4); a wheel support (8); and a shock absorber (12) having an upper end attached to a vehicle body (B) of a vehicle and a lower end attached to the lower arm, wherein the upper arm and the lower arm are arranged such that a ratio ζscuff of a scuff change-based apparent damping coefficient ζscuff to a critical damping coefficient CC of the suspension device becomes equal to or greater than a lower limit, under the condition that the vehicle is traveling straight ahead on a flat road at a given vehicle speed, wherein the scuff change-based apparent damping coefficient ζscuff is obtained by dividing, by a stroke speed of a wheel, an up-down directional component of a vehicle width-directional force arising on a ground contact surface of the wheel due to a vehicle width-directional displacement of the wheel occurring along with a stroke of the wheel, and the lower limit is set such that it becomes larger as a tire longitudinal spring constant of the wheel becomes smaller