CV Joint Boot Material Blend for Heat, Cold, and Ozone Resistance
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Solution Overview
Problem
Constant velocity universal joints face challenges with flexible boots that require both high heat resistance and cold resistance, as well as oil and ozone resistance, while maintaining durability and followability, especially under severe environmental conditions such as high temperatures and low temperatures, high-speed rotation, and centrifugal forces.
Innovation Solution
A flexible boot for a constant velocity universal joint is developed using a rubber material blend of 50 to 80 parts by weight of hydrogenated nitrile rubber (HNBR) with 15 to 21 wt% acrylonitrile content and 20 to 50 parts by weight of ethylene propylene diene rubber (EPDM), ensuring an elastic recovery rate of 18% or more at -40°C, with swelling of 100% or less in IRM 903 oil immersion tests, and incorporating appropriate additives for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If chloroprene rubber (CR) is used for heat resistance, then grease resistance is improved, but dynamic ozone resistance and air heat aging resistance deteriorate
Solution Approach 1:
The patent uses a composite rubber material consisting of HNBR and EPDM in specific proportions (HNBR: 30-70 parts, EPDM: 70-30 parts) to achieve both heat resistance and ozone resistance. HNBR provides the heat resistance property while EPDM contributes ozone resistance, and their combination creates a material that satisfies both requirements simultaneously, resolving the contradiction between heat resistance and ozone resistance.
2Temperature
If cold resistance is improved, then low temperature performance is enhanced, but oil resistance deteriorates
Solution Approach 1:
The patent uses the synergistic effect of HNBR-EPDM composite materials where EPDM provides cold resistance through its molecular structure while HNBR maintains oil resistance. The specific composition ratio ensures that the material resists both low-temperature embrittlement and oil swelling, resolving the contradiction between cold resistance and oil resistance.
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 solution provides a flexible boot that satisfies heat resistance, cold resistance, oil resistance, and ozone resistance, ensuring durability and sealability across various operating conditions, including high temperatures and low temperatures, and is suitable for severe environments.
Implementation Method 1
the rubber material having an elastic recovery rate of 18% or more at −40° C. in a TR test
Implementation Method 2
the rubber material preferably swells by 100% or less in an immersion test with IRM 903 oil
Data Source
AI summary
A flexible boot for a constant velocity universal joint includes: attachment portions to a mating member at both ends; and a bent portion provided between the attachment portions and absorbing deformation caused by operation of a constant velocity universal joint. The flexible boot is made of a rubber material obtained by blending 50 to 80 parts by weight of HNBR having an acrylonitrile content of 15 to 21 wt % and 20 to 50 parts by weight of EPDM, the rubber material having an elastic recovery rate of 18% or more at −40° C. in a TR test.