Air Spring Plastic Rolling Piston Thermal Expansion
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Solution Overview
Problem
Air springs in commercial vehicles with plastic connection parts often fail to maintain a tight seal due to temperature fluctuations, caused by differing linear expansion coefficients between plastic and metal materials.
Innovation Solution
The rolling piston and fastening bead cores are made of plastic with matching coefficients of linear expansion, ensuring the rolling bellows and connection parts expand uniformly, maintaining airtightness across various temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If plastic connection parts are used, then weight is reduced and corrosion protection is improved, but sealing tightness deteriorates due to temperature fluctuations
Solution Approach 1:
The invention uses homogeneous plastic material for both the connection part and the fastening bead core, ensuring matching thermal expansion coefficients. This material homogeneity eliminates the sealing tightness problem caused by temperature fluctuations between dissimilar materials like plastic and metal.
2Strength
If metal fastening bead cores are used with plastic rolling piston, then connection strength is improved, but sealing tightness deteriorates due to different linear expansion coefficients
Solution Approach 1:
The invention replaces the metal fastening bead core with a plastic one that has the same or similar coefficient of linear expansion as the rolling piston. This homogeneous material pairing ensures both connection strength and sealing tightness across the entire temperature range by eliminating differential thermal expansion.
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 configuration ensures a secure and airtight connection between the rolling bellows and connection parts over the entire temperature range, enhancing the air spring's reliability and efficiency.
Implementation Method 1
the coefficient of linear expansion between plastic and steel differs by a factor of 10... Due to the different linear expansion coefficients of plastic and metal, the diameter of the cone seat on the plastic piston side and the metal bead core on the bellows side change so much that the cone seat no longer seals
Data Source
Figure 1a~1c
Figure 2a~2c
AI summary
The invention relates to an air spring (1) for commercial vehicles having a first connecting part (2), in particular in the form of a cover, a second connecting part (3) in the form of a rolling piston, a rolling bellows (4) made from elastomeric material, wherein a first end of the rolling bellows (4a) can be fastened sealingly to the first connecting part (2) by means of a first fastening means (5a) and a second end of the rolling bellows (4b) can be fastened sealingly to the rolling piston (3) by means of a second fastening means (5b). There is provision according to the invention for the rolling piston (3) to be composed of plastic and for the second fastening means (5b) not to be formed from metal, and/or for the first connecting part (2) to be composed of plastic and for the first fastening means (5a) not to be formed from metal.