Dual-Layer Cylinder Liner for High-Pressure Diesel Engines

Solution Overview

Problem

Cylinder liners for internal combustion engines face challenges in achieving higher reliability and efficiency, particularly under high combustion pressures, where existing materials like gray cast iron alloys struggle with wear resistance, machinability, and cavitation resistance.

Innovation Solution

A cylinder liner with a dual-layer structure, featuring compact graphite iron on the inner surface for improved sliding properties and wear resistance, and austempered ductile iron on the outer surface for enhanced tensile strength and cavitation resistance, utilizing specific graphite morphologies and microstructures to optimize mechanical properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If gray cast iron alloys are used for cylinder liners, then wear resistance is provided, but cavitation resistance and tensile strength are insufficient under high combustion pressures

Engineering Contradiction:

Improvetensile strengthVSAvoidcavitation resistance

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The invention employs composite materials by combining two distinct iron alloys with different graphite morphologies: compact graphite iron (CGI) for the inner surface and austempered ductile iron (ADI) for the outer surface. This composite structure allows each material to contribute its superior properties - CGI provides excellent wear resistance and machinability at the contact surface, while ADI provides enhanced tensile strength and cavitation resistance at the structural level, thereby resolving the contradiction between wear resistance and cavitation/tensile strength under high combustion pressures.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention applies local quality by differentiating the material properties at different locations of the cylinder liner. The inner surface requires different properties (wear resistance, machinability) compared to the outer surface (tensile strength, cavitation resistance). By assigning CGI to the inner portion and ADI to the outer portion, each region receives the optimal material characteristics for its specific functional requirements, thus resolving the contradiction between localized wear resistance and overall structural strength.

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If compact graphite iron is used on the inner surface, then wear resistance and machinability are improved, but tensile strength is reduced compared to austempered ductile iron

Engineering Contradiction:

ImprovemachinabilityVSAvoidtensile strength

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The invention applies local quality by differentiating the material properties at different locations of the cylinder liner. The inner surface requires different properties (wear resistance, machinability) compared to the outer surface (tensile strength, cavitation resistance). By assigning CGI to the inner portion and ADI to the outer portion, each region receives the optimal material characteristics for its specific functional requirements, thus resolving the contradiction between localized wear resistance and overall structural strength.

Inventive Principle:

Principle #3Local quality

3Productivity

If wall thickness is reduced to increase power density, then engine efficiency improves, but structural integrity and resistance to high pressures decrease

Engineering Contradiction:

Improvepower densityVSAvoidstructural integrity

Core Design Contradiction:

ProductivityVSStrength

Solution Approach 1:

The invention employs composite materials by combining two distinct iron alloys with different graphite morphologies: compact graphite iron (CGI) for the inner surface and austempered ductile iron (ADI) for the outer surface. This composite structure allows each material to contribute its superior properties - CGI provides excellent wear resistance and machinability at the contact surface, while ADI provides enhanced tensile strength and cavitation resistance at the structural level, thereby resolving the contradiction between wear resistance and cavitation/tensile strength under high combustion pressures.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS10371085B2Cylinder liner and method of forming the same

Publication Date: 2019.08.06 ZYNP INTERNATIONAL CORP

AI summary

A high strength cast iron material for application in heavy duty diesel engines with Pa peak cylinder pressure greater than 240 bar is disclosed, the material a ductile material austempered to get a ausferrite matrix structure with higher mechanical properties than conventional cast iron materials available by using a designed low cost alloying cast material with heat treatment. Furthermore, the cylinder liner may be formed using novel heat treatment and/or fine honing processes to improve the properties thereof.