Variable Stiffness Wheel Suspension for NVH Damping
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Solution Overview
Problem
Vehicles with automatic transmissions experience unwanted NVH effects due to drive train vibrations being transmitted to the wheels and vehicle structure, particularly when the wheel suspension's vertical resonance coincides with engine firing frequencies, leading to perceptible noise and harshness.
Innovation Solution
A motor vehicle wheel suspension with an elastic element having a variable stiffness characteristic that is softer near the zero point and transitions to a higher stiffness further away, combining the damping benefits of a softer curve for NVH reduction with the ride dynamics of a stiffer curve, achieved by using a combination of soft and hard elastic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional elastic element with constant stiffness is used, then the suspension provides consistent support, but drive train vibrations are transmitted to the vehicle structure causing NVH effects
Solution Approach 1:
The elastic element is designed with a progressive stiffness characteristic where the stiffness increases with deflection amplitude. This dynamic stiffness adaptation allows the suspension to provide softer support for small vibrations (reducing NVH effects) while maintaining adequate support for larger deflections (managing ride dynamics).
Solution Approach 2:
The stiffness parameter of the elastic element is intentionally varied across different deflection ranges. By changing the stiffness parameter from low (near zero point) to high (at larger deflections), the system optimizes vibration damping at low amplitudes while maintaining structural support at high amplitudes.
2Object-affected harmful factors
If a softer stiffness curve is used to dampen vibrations, then NVH effects are reduced, but ride dynamics deteriorate
Solution Approach 1:
The progressive stiffness characteristic creates a dynamic response where the suspension behaves differently depending on the amplitude of excitation. For small vibrations from the drive train, the soft stiffness provides effective damping. For larger deflections during normal riding, the stiffness increases to maintain proper ride dynamics and support.
Solution Approach 2:
The soft stiffness characteristic is applied partially—only in the low deflection range where vibration damping is needed. At larger deflections, the stiffness becomes sufficient to maintain ride dynamics, thus applying the soft characteristic only where excessive damping is beneficial without compromising overall 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
This solution effectively absorbs and dampens drive train vibrations near the zero point, reducing their transmission to the vehicle body and improving ride dynamics by selectively using softer and stiffer stiffness profiles based on deflection ranges.
Implementation Method 1
at least one elastic element having a stiffness in a vertical direction of deflection with a softer stiffness characteristic in a deflection range close to the zero point than in deflection ranges more remote from the zero point
Implementation Method 2
effectively absorbs and dampens drive train vibrations near the zero point, reducing their transmission to the vehicle body
Data Source
AI summary
A wheel suspension for a motor vehicle wheel for damping NVH effects, wherein the NVH effects are transmitted from an automatic transmission to the driven wheel via the drive train at idle. The NVH effects can potentially be transmitted from the wheel to the vehicle structure via the wheel suspension. The wheel suspension having at least one elastic element, the stiffness of which in a vertical direction of deflection has a softer stiffness characteristic in a deflection range close to the zero point than in deflection ranges more remote from the zero point.