Variable-Gap Shock Absorber for Displacement-Dependent Damping
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Solution Overview
Problem
Existing hydraulic shock absorbers impair the shock-absorbing effect of the suspension in its freely oscillating central region due to velocity-dependent damping, which affects ride comfort and handling.
Innovation Solution
A shock absorber design with a piston rod passing through a cylinder featuring two spaced pistons and radially spaced axial bores, sealed by discs, and a continuously varying inner cylinder diameter, allowing displacement-dependent damping to minimize vibration damping in the central region, and optionally using a damper sleeve made of thermoplastic material with varying elasticity for different damping characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If hydraulic damping is applied to dampen vibrations, then ride comfort is improved, but the shock-absorbing effect of the spring in its freely oscillating central region is impaired
Solution Approach 1:
The shock absorber employs a variable annular gap between the piston and cylinder wall that changes dynamically with piston displacement. The gap is smallest in the central region (allowing free oscillation) and largest at the extremes (providing damping), creating a dynamic damping characteristic that adapts to the suspension's position rather than applying constant velocity-dependent damping
Solution Approach 2:
The damping characteristic is made non-uniform along the piston's travel path. The annular gap width varies locally - narrowest in the central freely oscillating region and wider toward the extremes - allowing different damping behaviors in different regions of the suspension's range of motion
2Force
If velocity-dependent damping is used, then vibration damping is achieved, but damping force interferes with spring function in the central region
Solution Approach 1:
The damping force becomes displacement-dependent rather than velocity-dependent. The variable annular gap creates a damping characteristic where the damping force varies with piston position - minimal in the central region and increasing toward the extremes - eliminating interference with the spring's natural oscillation while providing damping when needed
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 solution minimizes the impairment of the suspension's shock-absorbing effect, providing consistent damping independent of velocity and enhancing ride comfort and handling by adjusting damping based on displacement.
Implementation Method 1
When the piston rod moves in one direction, the fluid in the cylinder is compressed by the piston at the front of the cylinder. This presses the sealing disc located in front of the piston against it, thus closing the axial bores in the piston. The fluid is forced through the annular gap between the piston and the inner wall of the cylinder.
Implementation Method 2
the damper sleeve is made of a thermoplastic material, preferably polyamide. Due to the elasticity of the plastic, determined by the mechanical material properties of the corresponding modulus of elasticity, a pressure-dependent increase in the annular gap between the piston and the damper sleeve can be adjusted.
Data Source
Figure 1a~2
Figure 3~4e
Figure 5a~6e
AI summary
The invention relates to a shock absorber, particularly for wheeled vehicles, comprising a cylinder (1) filled with a fluid and a piston rod (3) guided therein, wherein the piston rod (3) extends through the cylinder (1) and is provided with two pistons (41, 42) spaced apart from each other, in which axial bores (413, 423) are provided radially spaced around the piston rod (3), and on the outer side of each of these bores a sealing disc (40) for closing the axial bores (413, 423) of the associated piston (41, 42) is axially movably mounted on the piston rod (3), and wherein the inner wall of the cylinder has, at least in certain regions, a diameter that changes continuously in the axial direction. The invention further relates to a wheeled vehicle with such a shock absorber.