Hydraulic Shock Absorber Segmented Flow Path for Cavitation
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Solution Overview
Problem
Conventional hydraulic shock absorbers experience a pause in damping force during the extension stroke due to pressure changes in the rod side oil chamber, which is affected by the flow path resistance of the compression side damping valve, leading to cavitation and instability in damping performance.
Innovation Solution
The hydraulic shock absorber design incorporates a compression side flow path with a compression side damping valve and check valve, where the intermediate portion communicates with the oil reservoir chamber, and an extension side flow path with an extension side damping valve and check valve, ensuring that the pressure of the rod side oil chamber remains dependent on the air chamber pressure, avoiding pauses in damping force and allowing control based on piston speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the flow path resistance of the compression side damping valve is increased to generate sufficient compression damping force, then the compression damping performance is improved, but the pressure in the rod side oil chamber becomes negative causing cavitation and pause in damping force during extension stroke
Solution Approach 1:
The compression side flow path is segmented into two separate outlets: one leading to the oil reservoir chamber and another leading to the rod side oil chamber. This segmentation allows the oil flow to be divided, ensuring that the rod side oil chamber receives sufficient oil supply to maintain positive pressure while the compression damping valve provides adequate damping force through its flow path resistance.
Solution Approach 2:
The oil reservoir chamber acts as an intermediary element that receives oil from the piston side oil chamber and redistributes it to the rod side oil chamber. This intermediary structure helps balance the pressure conditions in the rod side oil chamber, preventing negative pressure and cavitation while maintaining effective compression damping.
2Reliability
If the flow path resistance of the compression side damping valve is decreased to maintain positive pressure in the rod side oil chamber, then cavitation is avoided, but the compression damping force becomes insufficient
Solution Approach 1:
By segmenting the compression side flow path into two separate outlets, the system can independently control the flow distribution. The first outlet provides sufficient flow to the rod side oil chamber to maintain positive pressure, while the second outlet through the compression damping valve provides the necessary damping force, resolving the trade-off between pressure stability and damping force.
3Ease of operation
If a conventional damping force generating device is used with separate compression and extension valves, then the basic damping function is achieved, but the pressure fluctuation in the rod side oil chamber causes pause in damping force during extension stroke
Solution Approach 1:
The compression side damping valve is replaced with a segmented flow path that has two separate outlets. This segmentation allows one outlet to supply the rod side oil chamber with sufficient oil to maintain positive pressure, while the other outlet provides compression damping, eliminating the pause in damping force during extension stroke.
Solution Approach 2:
The oil reservoir chamber serves as an intermediary that decouples the pressure conditions in the rod side oil chamber from the compression damping valve. This intermediary structure ensures that the rod side oil chamber maintains positive pressure independent of the compression damping valve settings, preventing cavitation and damping force pause.
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 design prevents pauses in damping force during the extension stroke, enhances damping response by controlling pressure based on piston speed, and improves ride quality and driving stability by adjusting damping force characteristics accordingly.
Implementation Method 1
The oil reservoir chamber is pressurized by an air chamber (a bladder, a free piston or the like may be interposed between the oil reservoir chamber and the air chamber)
Implementation Method 2
generating a compression side damping force based on a flow path resistance of the compression side damping valve and the compression side damping valve
Implementation Method 3
generating an extension side damping force based on a flow path resistance of the extension side damping valve
Data Source
Figure 1
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AI summary
In a hydraulic shock absorber, a damping force generating device is provided between a piston side oil chamber and a rod side oil chamber of a cylinder, and in a compression stroke, a compression side flow path for circulating oil in the piston side oil chamber of the cylinder through an outside flow path of the cylinder toward the rod side oil chamber is provided in the damping force generating device, while in an extension stroke, an extension side flow path for circulating the oil in the rod side oil chamber of the cylinder through the outside flow path of the cylinder toward the piston side oil chamber is provided in the damping force generating device.