End-Stop Control Valve With Spring Disc for Smoother Damper Stroke Ends
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Solution Overview
Problem
Vibration dampers with auxiliary pistons experience a sudden increase in damping force, leading to undesirable noise, vibration, and harshness (NVH) effects and performance changes due to the step-function increase in damping force at maximum compression or rebound positions.
Innovation Solution
The vibration damper incorporates an end-stop control valve with a piston band and spring disc that gradually increase damping force by deflecting the valve disc stack-up and elastically deforming the spring disc, providing a progressive and smoother transition into end-of-stroke damping, reducing the sudden peak in damping force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If auxiliary pistons are used to increase damping force at end positions, then the damping force at maximum compression or rebound is improved, but the damping force increases suddenly in a step-function manner causing NVH effects
Solution Approach 1:
The valve disc stack-up is designed to deflect progressively as the piston approaches the end position, transforming the static step-function damping increase into a dynamic progressive increase. The valve discs bend gradually under increasing hydraulic pressure, providing a smooth transition of damping force rather than an abrupt change.
Solution Approach 2:
The system changes the physical state of the valve discs from rigid to flexible under load, allowing them to deflect and absorb energy progressively. This parameter change enables the damping force to increase gradually through elastic deformation of the valve discs rather than suddenly through auxiliary piston engagement.
2Reliability
If auxiliary pistons are used to prevent bottoming out, then the reliability of the vibration damper is improved, but the sudden increase in damping force causes performance changes
Solution Approach 1:
The progressive deflection of valve discs creates a dynamic damping characteristic that adapts smoothly to approaching end positions. This dynamic response prevents bottoming out while maintaining consistent performance by avoiding abrupt changes in damping force that would disrupt vehicle handling.
Solution Approach 2:
The valve disc stack-up acts as an intermediary between the main piston and the auxiliary piston, mediating the transition of damping force. Instead of direct engagement causing sudden force changes, the flexible valve discs provide a buffering transition that maintains performance consistency.
3Force
If a large increase in damping force is supplied by auxiliary piston engagement, then the damping effect at end positions is improved, but the rapid change in acceleration causes undesirable NVH effects
Solution Approach 1:
The valve discs progressively deflect under increasing hydraulic pressure as the piston approaches the end position, creating a dynamic damping curve that increases force gradually. This dynamic response controls the rate of change of acceleration by spreading the force increase over a longer distance and time period.
Solution Approach 2:
The flexible valve disc stack-up provides beforehand cushioning by gradually absorbing energy as the piston approaches the end position. This progressive cushioning effect prevents sudden acceleration changes by preparing the damping system in advance rather than reacting abruptly at the end position.
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 reduces NVH effects and improves performance by smoothing the transition into end-of-stroke damping, providing a more gradual increase in damping force and minimizing the sudden peak associated with traditional auxiliary piston systems.
Implementation Method 1
elastically deforming the spring disc, providing a progressive and smoother transition into end-of-stroke damping
Implementation Method 2
gradually increase damping force by deflecting the valve disc stack-up
Implementation Method 3
The end-stop control valve may include a piston band that is arranged on the piston and at least partially surrounds the piston. As the end-of-stroke damping event begins, the piston comes within the elongate catch piston but does not contact the elongate catch piston. Meanwhile, the piston band contacts a sidewall of the elongate catch piston
Data Source
AI summary
An end-stop control valve can progressively add end-of-stroke damping resistance to complement the damping force provided by a main piston in a damper tube. The end-stop control valve may include a piston that is secured on a piston rod and selectively engages a catch piston, both of which are longitudinally movable within the damper tube. As the piston approaches the catch piston, an annular pocket of hydraulic fluid is created longitudinally and radially between the piston and the catch piston. As the piston continues to approach the catch piston, a cross-sectional area through which hydraulic fluid exits the pocket decreases, thereby gradually increasing the resistance of the end-stop control valve. In addition, a spring disc secured on the piston rod may contact a valve seat on the catch piston and provide resistance by elastically deforming in a longitudinal direction before the contact surfaces of the piston and catch piston engage.