Diurea Grease Composition for High-Temperature Bearing Life
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Solution Overview
Problem
Conventional greases fail to ensure long bearing life at elevated temperatures due to insufficient heat resistance of base oils and thickeners, and poor compatibility with sealing materials like polyacrylic rubber, leading to unsatisfactory filling performance in automotive electrical equipment.
Innovation Solution
A grease composition with a synthetic hydrocarbon oil content of 20% or more and an ester-based oil content of 20% or less, using a diurea compound as a thickener with a cyclohexyl group ratio of 60-95 mol%, which enhances heat resistance and compatibility with acrylic rubber, ensuring proper fluidity and extended bearing life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional greases using mineral oils, synthetic hydrocarbon oils and ether-based synthetic oils as base oil are employed, then the grease can be used for rolling element bearings, but the heat resistance of the base oils and thickeners is insufficient and the filling performance is unsatisfactory at elevated temperatures
Solution Approach 1:
The patent changes the chemical composition parameters of the base oil by specifying a synthetic hydrocarbon oil with a specific viscosity range (45-450 mm²/s at 40°C) and compositional ratios (5-50 mass% aromatic hydrocarbons, 45-90 mass% cycloaliphatic hydrocarbons), thereby improving heat resistance while maintaining filling performance at elevated temperatures
Solution Approach 2:
The patent creates a composite grease system by combining a specifically formulated synthetic hydrocarbon oil with a diurea compound thickener containing cyclohexyl groups, where the thickener has a specific structure (formula I) with R1-R6 being cyclohexyl groups or hydrogen atoms, achieving synergistic improvement in both heat resistance and bearing life
2Temperature
If diurea greases using aromatic urea are used, then durability under high temperatures is improved, but the compatibility with sealing material (polyacrylic rubber) is insufficient
Solution Approach 1:
The patent modifies the structural parameters of the diurea compound by specifying that R1-R6 in formula (I) must include cyclohexyl groups (at least one of R1-R6 is a cyclohexyl group), which changes the chemical compatibility characteristics while maintaining thermal stability, thereby resolving the incompatibility issue with polyacrylic rubber sealing materials
3Ease of operation
If ether-based synthetic oil is contained in an amount of more than 50 mass% to improve filling performance, then the filling performance may be improved, but the compatibility of the base oil with the thickener becomes insufficient
Solution Approach 1:
The patent fundamentally changes the base oil type from ether-based synthetic oil to synthetic hydrocarbon oil with specific viscosity and compositional parameters, which maintains adequate filling performance while ensuring excellent compatibility with the diurea compound thickener, thereby resolving the incompatibility issue
Data Source
AI summary
The invention provides a grease composition which is capable of extending the bearing life even at elevated temperatures and has little effect on acrylic rubber; and a bearing in which the above-mentioned grease composition is packed. The grease composition contains a thickener and a base oil, the base oil including a synthetic hydrocarbon oil in an amount of 20 mass% or more of the total mass of the base oil and an ester-based oil in an amount of 20 mass% or less of the total mass of the base oil, and the thickener containing a diurea compound represented by formula (I): R1-NHCONH-R2-NHCONH-R3 wherein R2 is a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms, and R1 and R3 may be the same or different and represent cyclohexyl group or a straight-chain or branched alkyl group having 8 to 18 carbon atoms, with the ratio of the number of moles of the cyclohexyl group to the total number of moles of R1 and R3 being 60 to 95%. The bearing has the above-mentioned grease composition sealed therein.