Nested Piston Rod Damper for Stroke-Dependent Shock Absorbers
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Solution Overview
Problem
Conventional shock absorbers with stroke-dependent damper assemblies have increased dead length, reduced stroke capability, and higher manufacturing costs due to larger bore requirements, which can lead to damage and faulty operation, and do not effectively provide varying damping forces based on stroke length.
Innovation Solution
A shock absorber design with a pressure tube, piston rod, and damper assembly that includes a floating piston and valve assemblies to control fluid flow, allowing for varying damping forces by adjusting fluid flow paths based on stroke length, reducing dead length and manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a stroke dependent damper assembly is mounted to a post of the piston rod below a main piston assembly, then two stages of damping (hard and soft) are provided, but the dead length of the shock absorber increases, reducing the range of movement of the main piston within the pressure tube
Solution Approach 1:
The damper assembly is nested within the piston rod bore, with the floating piston and valve assembly contained inside the piston rod structure. This nesting allows the damper assembly to occupy space within the existing piston rod volume rather than extending the overall shock absorber length, thereby providing multi-stage damping without increasing dead length.
Solution Approach 2:
The invention transitions from a longitudinal arrangement (mounting the damper assembly below the main piston along the stroke direction) to a radial arrangement (mounting the damper assembly within the piston rod bore perpendicular to the stroke direction). This dimensional change allows the damper assembly to be positioned without extending the effective stroke length of the shock absorber.
2Adaptability or versatility
If a stroke dependent damper assembly is mounted below the main piston assembly, then varying damping forces are provided, but the stroke capability of the shock absorber is reduced
Solution Approach 1:
By nesting the damper assembly within the piston rod bore, the floating piston can move axially within the rod chamber without extending beyond the pressure tube ends. This allows the full stroke capability to be utilized while still providing varying damping forces through the internal damper assembly.
Solution Approach 2:
The piston rod acts as an intermediary structure that houses the damper assembly within its bore. This intermediary positioning allows the damper assembly to function independently without interfering with the main piston's stroke capability, as the damper assembly moves within the piston rod rather than along the external pressure tube.
3Reliability
If a stroke dependent damper assembly with larger bore levels is used, then damping performance is improved, but manufacturing cost increases
Solution Approach 1:
The damper assembly is nested within the existing piston rod bore, utilizing the available internal volume rather than requiring larger external dimensions. This allows effective damping performance to be achieved with the same overall shock absorber size, avoiding increased manufacturing costs associated with larger bores.
Solution Approach 2:
The invention changes the positioning parameter of the damper assembly from external mounting to internal nesting within the piston rod. This parameter change allows the use of smaller bore dimensions while maintaining damping performance, as the damper assembly operates within the existing piston rod volume rather than requiring additional external space.
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 design provides a smooth transition from soft to firm damping based on stroke length, enhancing vehicle vibration damping, preventing damage, and reducing manufacturing costs by accommodating smaller bore levels, while maintaining effective damping performance.
Implementation Method 1
The main piston includes a compression valving that limits the flow of a hydraulic fluid from the second working chamber to the first working chamber during a compression stroke. The main piston also includes a rebound valving that limits the flow of the hydraulic fluid from the first working chamber to the second working chamber during a rebound or an extension stroke.
Implementation Method 2
By controlling the fluid flow between the first working chamber and the second working chamber, a pressure drop is built up between the first working chamber and the second working chamber.
Implementation Method 3
The damper assembly includes a floating piston that is longitudinally moveable between two rubber travel stops. The floating piston separates the inner chamber into an upper inner chamber and a lower inner chamber.
Data Source
AI summary
A shock absorber for a vehicle includes a pressure tube containing a hydraulic fluid. The shock absorber further includes a piston rod extending within the pressure tube along a longitudinal axis, and including a piston end disposed within the pressure tube. The piston rod includes a rod chamber defined within the piston rod and extending along the longitudinal axis from an upper chamber end distal to the piston end to a lower chamber end proximal to the piston end. The piston rod further includes at least one first opening disposed proximal to the lower chamber end. The shock absorber further includes a first piston assembly, an auxiliary housing, and a damper assembly including a sleeve received within the rod chamber.