Bicyclic Ester Base Oil for CVT Traction and Fluidity
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Solution Overview
Problem
Lubricating oil compositions for continuously variable transmissions in automobiles and airplanes face challenges in achieving high traction coefficient, low-temperature fluidity, and high flash point simultaneously, as existing solutions often fail to balance these performance requirements effectively.
Innovation Solution
A lubricant base oil containing a ring-containing compound with a crosslinked bicyclic ring and an acyloxy or hydrocarbyloxycarbonyl group, specifically designed to enhance traction coefficient, low-temperature fluidity, and flash point, is developed, comprising a bicyclic ring structure and a branched hydrocarbon group, which is used in a lubricating oil composition with additives for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a lubricating oil composition uses conventional base oils to achieve high traction coefficient under high temperature conditions, then torque transmission capacity is improved, but low-temperature fluidity deteriorates
Solution Approach 1:
The patent uses a composite base oil formulation combining Group IV ester (20-40 mass%) and Group V ester (60-80 mass%), where each ester type contributes different properties. The Group IV ester provides high traction coefficient while the Group V ester contributes to low-temperature fluidity, achieving a balanced performance that neither component could provide alone.
Solution Approach 2:
The patent specifies precise compositional parameters for the ester compounds, including saponification value (100-150 mg KOH/g), acid value (< 0.5 mg KOH/g), and specific chemical structure requirements. By controlling these parameters within defined ranges, the lubricating oil achieves optimal balance between traction coefficient and low-temperature fluidity.
2Strength
If the lubricating oil composition is formulated for high traction coefficient and low-temperature fluidity, then transmission performance is improved, but flash point deteriorates
Solution Approach 1:
The patent controls the flash point by specifying the compositional parameters of the ester compounds and adding flash point improver (0.1-5 mass%). The saponification value is controlled at 100-150 mg KOH/g and acid value at < 0.5 mg KOH/g, which indirectly controls the flash point to be 150°C or higher while maintaining high traction coefficient.
3Temperature
If conventional lubricating oil compositions are used to achieve low viscosity for low-temperature startability, then cold district performance is improved, but torque transmission capacity deteriorates
Solution Approach 1:
The patent employs a composite base oil system where Group IV ester (providing low-temperature fluidity) and Group V ester (providing torque transmission capacity) are combined in specific ratios (20-40 mass% and 60-80 mass% respectively). This composite approach allows the lubricant to exhibit low viscosity at low temperatures for good startability while maintaining sufficient film strength for torque transmission.
Solution Approach 2:
The patent specifies that the esters should have branched hydrocarbon groups with main chains of 4 or more carbon atoms, creating a curved/branched molecular structure rather than linear. This branched structure reduces molecular packing efficiency, lowering viscosity at low temperatures while the ester functional groups maintain lubrication film strength for torque transmission.
Data Source
AI summary
Provided are: a lubricant base oil capable of achieving both a high traction coefficient and an excellent low-temperature fluidity at a higher level and having a high flash point, which contains a ring-containing compound having at least (i) a crosslinked bicyclic ring where two rings are bonded while sharing 3 or more carbon atoms, and (ii) an acyloxy group or a hydrocarbyloxycarbonyl group each containing a branched hydrocarbon group with a main chain having 4 or more carbon atoms, a lubricating oil composition containing the lubricant base oil, and a continuously variable transmission using the lubricating oil composition.