Fine-Particle Urea Grease for High-Speed Bearing Durability
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Solution Overview
Problem
Conventional urea greases used in high-speed bearings tend to cause oil film shortages, leading to early seizure and inadequate durability due to high heat generation in electric, hybrid, and plug-in hybrid vehicles, where bearings operate at high speeds with a DN value of 100,000 or more.
Innovation Solution
A grease composition with a urea-based thickener having an arithmetic mean particle diameter of 2.0 μm or less and a specific surface area of 20,000 cm2/cm3 or more, combined with a base oil and optional additives, is developed to enhance durability under high-speed conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional urea grease is used for high-speed bearings, then heat resistance is improved, but oil film stability deteriorates leading to early seizure
Solution Approach 1:
The patent applies parameter changes by controlling the particle size distribution of the urea-based thickener. Specifically, it limits the arithmetic mean particle diameter to 2.0 μm or less and controls the proportion of fine particles (1.0 μm or less) to 70% or more by volume. This parameter optimization enables the grease to maintain both high-temperature resistance and stable oil film formation under high-speed bearing conditions.
2Power
If bearing rotation speed is increased to meet higher output requirements, then power output is improved, but heat generation increases causing lubrication failure
Solution Approach 1:
The patent addresses heat generation from high-speed rotation by optimizing the thickener particle size parameters. The controlled particle distribution (mean diameter ≤2.0 μm, with fine particles ≥70% by volume) creates a grease structure that maintains stable lubrication films at elevated temperatures, enabling the bearing to operate at higher speeds without lubrication failure.
3Reliability
If particle size of urea-based thickener is reduced, then oil film stability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent specifies clear particle size parameters (arithmetic mean diameter ≤2.0 μm, with fine particles ≥70% by volume) that can be controlled through standard manufacturing processes. These quantifiable parameters provide a straightforward basis for quality control and process optimization, avoiding excessive manufacturing complexity while achieving the desired oil film stability.
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 grease composition significantly improves the durability of bearings by maintaining the base oil and ensuring effective lubrication, extending the bearing life under high-speed rotation conditions with a DN value of 100,000 or more.
Implementation Method 1
the arithmetic mean particle diameter on an area basis when the particles are measured by a laser diffraction scattering method
Data Source
AI summary
The present invention relates to a grease composition which can impart excellent durability to a bearing used under a high-speed rotation condition with a DN value of 100,000 or more, wherein the grease composition contains a base oil (A) and a urea-based thickener (B), and particles containing the urea-based thickener (B) in the grease composition satisfy requirement (I) that the particles have an arithmetic mean particle diameter of 2.0 μm or less on an area basis when measured by a laser diffraction scattering method. The grease composition is used for a bearing used under a high-speed rotation condition with a DN value of 100,000 or more.