Comb-Shaped Polymer Viscosity Index Improver for LSPI Prevention
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Solution Overview
Problem
Lubricating oil compositions for direct-injection supercharged gasoline engines face challenges in achieving a balance between improved fuel saving properties, detergency, and preventing low-speed pre-ignition (LSPI), with existing solutions either failing to provide satisfactory fuel saving or worsening detergency when increasing metallic detergent content.
Innovation Solution
A lubricating oil composition incorporating a comb-shaped polymer as a viscosity index improver, combined with a detergent dispersant containing alkali metal borate and a molybdenum-containing friction modifier, with regulated content of alkali metal and alkaline earth metal atoms to enhance detergency and prevent LSPI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a polymethacrylate (PMA) is used as a viscosity index improver to improve fuel saving properties, then fuel consumption performance is improved, but detergency is worsened under high temperature high shear viscosity conditions
Solution Approach 1:
The patent changes the molecular structure parameter of the viscosity index improver from conventional PMA to comb-shaped polymer with specific molecular weight (10,000-1,000,000) and comb structure characteristics (main chain with side chains), which improves both fuel saving properties and maintains detergency under high temperature high shear conditions
Solution Approach 2:
The patent creates a composite lubricating oil composition combining comb-shaped polymer viscosity index improver with specific additives including metallic detergent (0.01-1.0 mass%), nitrogen-containing ashless dispersant (0.01-1.0 mass%), and friction modifier (0.01-5.0 mass%), where the synergistic interaction of components resolves the contradiction between fuel saving and detergency
2Reliability
If the blending amount of metallic detergent is increased to improve detergency, then detergency is improved, but abnormal combustion (low-speed pre-ignition, LSPI) is more likely to occur
Solution Approach 1:
The patent optimizes the concentration parameter of metallic detergent to a specific range (0.01-1.0 mass%) and combines it with nitrogen-containing ashless dispersant and friction modifier, creating a balanced formulation that provides sufficient detergency while preventing LSPI through the synergistic effect of multiple components at controlled concentrations
Data Source
AI summary
The lubricating oil composition of the present invention contains, together with a base oil, a viscosity index improver (A) including a comb-shaped polymer (A1), a detergent dispersant (B) including an alkali metal borate (B1) and an organometallic compound (B2) containing a metal atom selected from an alkali metal atom and an alkaline earth metal atom, and a friction modifier (C) including a molybdenum-containing friction modifier, with the total content of an alkali metal atom and an alkaline earth metal atom being 2,000 mass ppm or less. The lubricating oil composition of the present invention has excellent detergency, fuel saving properties, and LSPI-preventing properties.