Dual-Coated Piston Ring for Lower Wear and Flank Friction

Solution Overview

Problem

Piston rings in internal combustion engines face challenges with high wear and friction, which lead to increased blow-by, oil consumption, and potential breakage due to excessive axial clearance, and existing coatings like nitriding have limitations in cost-effectiveness and friction reduction.

Innovation Solution

A piston ring design featuring a DLC layer on the running surface and a chromium layer on at least one flank surface, with the chromium layer being more cost-effective and providing lower wear and friction, particularly on the lower flank surface, and a PVD process for DLC formation, ensuring reduced wear and friction through controlled crack density and hardness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a DLC layer is applied on the running surface, then wear and friction are reduced and burn-mark resistance is improved, but production cost and manufacturing complexity increase

Engineering Contradiction:

Improvewear resistanceVSAvoidproduction cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies different coating materials to different surfaces of the piston ring based on their specific functional requirements. The running surface receives a DLC coating for low friction and wear protection, while the flank surfaces receive a chromium coating for corrosion and wear resistance. This localized differentiation optimizes performance while managing manufacturing complexity and cost.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The piston ring employs a composite coating system combining two different materials (DLC and chromium) on different surfaces. Each material is selected for its specific properties: DLC for low friction and high wear resistance on the running surface, and chromium for corrosion resistance and wear protection on the flank surfaces. This composite approach maximizes overall performance.

Inventive Principle:

Principle #40Composite materials

2Reliability

If a chromium layer is applied on the flank surface, then wear and friction are reduced compared to nitrided flanks, but manufacturing complexity increases

Engineering Contradiction:

Improvewear resistanceVSAvoidcoating structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies different coating materials to different surfaces of the piston ring based on their specific functional requirements. The running surface receives a DLC coating for low friction and wear protection, while the flank surfaces receive a chromium coating for corrosion and wear resistance. This localized differentiation optimizes performance while managing manufacturing complexity and cost.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If the piston ring flank surfaces are left uncoated or nitrided, then manufacturing is simpler and more cost-effective, but wear increases leading to blow-by and oil consumption

Engineering Contradiction:

Improveproduction costVSAvoidwear resistance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies different coating materials to different surfaces of the piston ring based on their specific functional requirements. The running surface receives a DLC coating for low friction and wear protection, while the flank surfaces receive a chromium coating for corrosion and wear resistance. This localized differentiation optimizes performance while managing manufacturing complexity and cost.

Inventive Principle:

Principle #3Local quality

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution significantly reduces wear and friction on both the piston ring and the groove, lowering oil consumption and preventing breakage, with chromium layer properties like low friction coefficient and embedded particles enhancing performance under high loads and adverse lubrication conditions.

Implementation Method 1

the uppermost layer of the running surface is a DLC layer

Methodology Applied

Scientific EffectDiamond-like carbon coating: Diamond-like Carbon

Implementation Method 2

A PVD (Physical Vapor Deposition) process is preferred for the formation of the DLC layer

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Implementation Method 3

the uppermost layer of at least one flank surface is a chromium layer... the chromium layer is produced by galvanic formation

Methodology Applied

Scientific EffectGalvanic chromium coating: Electroplating

Data Source

PatentUS11408508B2Piston ring

Publication Date: 2022.08.09 FEDERAL MOGUL BURSCHEID GMBH

AI summary

A piston ring (10) has a running surface (12) and a flank surface (14) which are coated. The uppermost layer of the running surface (12) is a hydrogen-containing or a hydrogen-free DLC layer, and the uppermost layer of at least one flank surface (14) is a chromium layer. A method of producing a piston ring (10) includes forming a DLC layer as the uppermost layer of the running surface (12), and forming a chromium layer as the uppermost layer of at least one flank surface (14).