Composite Back-Up Ring for Low-Friction Hydraulic Cylinder Sealing
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Solution Overview
Problem
Existing sealing devices for hydraulic cylinders in construction machinery often experience abnormal noise during low-speed operation due to high static friction between the back-up ring and the shaft, which is caused by the lack of slidability of the back-up ring.
Innovation Solution
A back-up ring comprising a resin composition with a polyamide resin as the base material and a low-friction resin as the filler material, which has a lower static friction coefficient than polyamide resin, is used to reduce static friction and enhance slidability, thereby preventing abnormal noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a back-up ring made of polyamide resin is used to counter hydraulic pressure, then mechanical strength and durability are improved, but static friction coefficient increases causing abnormal noise during low-speed operation
Solution Approach 1:
The back-up ring is made from a composite material consisting of polyamide resin as the base material and low friction resin particles as filler material. This composite structure combines the high mechanical strength of polyamide with the low friction properties of the filler resin, resolving the contradiction between strength and friction-induced noise.
Solution Approach 2:
The invention changes the physical and chemical parameters of the back-up ring material by incorporating filler material with specific properties (low friction coefficient, compatible with polyamide). This modifies the surface characteristics and friction properties while maintaining the structural integrity provided by the polyamide base material.
2Duration of action of stationary object
If polyamide resin is used as back-up ring material, then durability and heat resistance are improved, but slidability against the shaft deteriorates
Solution Approach 1:
By creating a composite material with polyamide resin and low friction resin filler, the invention achieves both durability from the polyamide matrix and improved slidability from the low friction resin particles distributed throughout the structure.
Solution Approach 2:
The low friction resin filler material is distributed within the polyamide matrix to create local regions with reduced friction properties, allowing the back-up ring to maintain overall structural durability while providing improved slidability at the contact surfaces with the shaft.
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 combination of polyamide and low-friction resin in the back-up ring reduces static friction, eliminating abnormal noise during low-speed operation and maintaining mechanical properties like heat resistance and durability.
Implementation Method 1
the filler material comprises a low friction resin compatible with the polyamide resin and having a lower static friction coefficient than the polyamide resin with respect to the shaft
Data Source
AI summary
A sealing device is configured to seal a clearance between a housing and a shaft of a hydraulic cylinder. The sealing device includes an annular packing that is disposed within the clearance and comprises an elastic material, and a back-up ring that is in contact with the packing. The back-up ring has a contact surface that is in contact with the shaft, and a portion including at least the contact surface of the back-up ring comprises a resin composition that includes a base material and a filler material. The base material comprises a polyamide resin, and the filler material comprises a polyolefin resin that is compatible with the polyamide resin.