Automatic Transmission Lubricating Oil Composition for Low Churning Resistance
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Solution Overview
Problem
Lubricating oils for automatic transmissions face challenges in maintaining balanced viscosity, friction characteristics, and oxidative stability across a wide temperature range, particularly in reducing churning resistance and energy losses while withstanding extreme temperatures and cold conditions.
Innovation Solution
A lubricating oil composition comprising 60-98% low viscosity base oils from API Groups 2-4, 1-20% high-viscosity metallocene/poly-α-olefins, and 1-20% polymethacrylate, with specific viscosity and molecular weight ranges to achieve high viscosity index, excellent low-temperature viscosity, and low evaporation at high temperatures, ensuring shear stability and oxidative stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a low viscosity base oil is used to reduce churning resistance and improve fuel consumption, then churning resistance and energy losses are reduced, but evaporation and viscosity maintenance at high temperatures deteriorate
Solution Approach 1:
The patent uses a composite base oil formulation combining Group 2-4 base oils (60-98 mass%) with Fischer-Tropsch synthetic oil (45-80 mass% of the low viscosity base oil) and metallocene/poly-α-olefins (1-20 mass%). This composite approach achieves low viscosity (5-7 mm²/s at 100°C) while maintaining high viscosity index (≥190) and excellent high-temperature stability through synergistic effects of the different base oil components.
Solution Approach 2:
The patent optimizes specific parameters including kinematic viscosity at 100°C (5-7 mm²/s), viscosity index (≥190), Brookfield viscosity at -40°C (≤5000 mPa·s), and controlled evaporation loss (≤10 mass% by NOACK method). These parameter specifications balance low-temperature flow characteristics with high-temperature viscosity maintenance and reduced evaporation.
2Temperature
If the viscosity index is increased to maintain viscosity at low temperatures, then low-temperature viscosity characteristics are improved, but the complexity of composition formulation increases
Solution Approach 1:
The patent achieves excellent low-temperature viscosity characteristics (Brookfield viscosity ≤5000 mPa·s at -40°C) by specifying precise parameter ranges for base oil viscosity (2-5 mm²/s at 100°C) and viscosity index (≥190), along with controlled proportions of different base oil groups, simplifying the formulation process through defined parameters.
Solution Approach 2:
The patent uses polymethacrylate (1-20 mass%) with specific molecular weight (10,000-50,000) as a viscosity index improver intermediary substance. This additive mediates between the base oils to achieve the target viscosity index (≥190) and maintains viscosity stability across the temperature range from -40°C to 200°C.
3Stability of the object's composition
If shear stability is improved to maintain viscosity under high-load operation, then viscosity characteristics are maintained, but the formulation requirements become more stringent
Solution Approach 1:
The patent achieves high shear stability (rate of reduction of 100°C kinematic viscosity ≤3% after KRL shear stability test) by specifying controlled proportions of Fischer-Tropsch synthetic oil (45-80 mass% of low viscosity base oil) and metallocene/poly-α-olefins (1-20 mass%), along with polymethacrylate viscosity index improver, creating a formulation that resists shear degradation under high-load conditions.
Data Source
AI summary
The invention provides a lubricating oil composition for automatic transmissions is made such that it comprises proportionately as its main constituents: 60 to 98 mass % as low viscosity base oils being base oils belonging to Groups 2 to 4 of the API (American Petroleum Institute) base oil categories wherein the kinematic viscosity at 100° C. is 2 to 5 mm2/s (Fischer-Tropsch synthetic oil comprising at least 45 to 80 mass %); 1 to 20 mass % as high-viscosity base oils being metallocene/poly-α-olefins with a kinematic viscosity at 100° C. of 100 to 600 mm2/s; and 1 to 20 mass % being a polymethacrylate with a weight-average molecular weight of 10,000 to 50,000. The viscosity index of this composition is not less than 190, the Brookfield viscosity at −40° C. is not more than 5000 mPa·s, the 100° C. kinematic viscosity is 5 to 7 mm2/s, and the rate of reduction of the 100° C. kinematic viscosity after a KRL shear stability test (60° C., 20 hr) is not more than 3%.