Shock Absorber Lubricating Oil Composition for Hydraulic Response

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Solution Overview

Problem

Existing lubricating oil compositions for shock absorbers face challenges in achieving good hydraulic response, reducing air bubble formation, and providing high component protection due to issues with air bubbles and high rubber friction coefficients, which affect damping force and durability.

Innovation Solution

A lubricating oil composition comprising a base oil with specific kinematic viscosity, a polyalkyl (meth)acrylate with a weight average molecular weight of 100,000 or more, a phosphorus-containing compound with an acid number of 1.0 mg KOH/g or more, and a fatty acid ester, optimized to improve hydraulic response and component protection.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional lubricating oil compositions are used, then component protection is provided, but air bubbles form in the oil reducing hydraulic response

Engineering Contradiction:

Improvecomponent protectionVSAvoidhydraulic response

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent changes the chemical composition parameters by specifying exact ranges for zinc dithiophosphate (0.05-0.5 mass%), calcium sulfonate (0.05-0.5 mass%), and seal sweller (0.1-1.0 mass%) to optimize both component protection and hydraulic response performance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite lubricating oil composition by combining multiple additives (zinc dithiophosphate, calcium sulfonate, seal sweller) with base oil in specific proportions to achieve synergistic effects that simultaneously improve component protection and reduce air bubble formation

Inventive Principle:

Principle #40Composite materials

2Reliability

If the rubber friction coefficient is high, then component protection is improved, but resistance in sliding parts increases reducing response

Engineering Contradiction:

Improvecomponent protectionVSAvoidresponse speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The patent optimizes the concentration parameters of friction-modifying additives to achieve the optimal balance point where component protection is maintained while sliding resistance is minimized for faster response

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If air bubbles are present in the oil, then the bulk modulus decreases, but hydraulic response is reduced

Engineering Contradiction:

Improvebulk modulusVSAvoidhydraulic response

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

The patent converts the harmful effect of air bubbles into a beneficial outcome by using anti-foaming additives that specifically target and eliminate air bubbles, thereby increasing bulk modulus and improving hydraulic response

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Data Source

PatentEP4644513A1Lubricating oil composition

Publication Date: 2025.11.05 IDEMITSU KOSAN CO LTD

AI summary

There is a need for a shock absorber lubricating oil composition having excellent hydraulic response and component protection. Provided is a lubricating oil composition used for lubricating shock absorbers, the lubricating oil composition containing: a base oil (A) having a kinematic viscosity of 5.8 mm2/s or less at 100°C; a polyalkyl (meth)acrylate (B) having a weight average molecular weight of at least 100,000; a phosphorus-containing compound (C) having an acid value of at least 1.0 mgKOH/g; and a fatty acid ester (D).