Integrated Scraper-Edge Cylinder Liner for Pressure Equalization

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Solution Overview

Problem

Cylinder liners in combustion engines suffer from reduced stiffness and fatigue strength due to large scraper rings, which also cause pressure differences leading to material stress and increased risk of fatigue cracks.

Innovation Solution

A cylinder liner with a protrusion extending radially inward from the wall, forming a scraper ring, and an enlarged inner diameter above it to minimize pressure differences and enhance structural stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a scraper ring is provided in the cylinder liner, then the piston can be properly guided and cleaned, but the material thickness of the cylinder liner is significantly reduced resulting in reduced stiffness

Engineering Contradiction:

Improvepiston guidance and cleaning functionalityVSAvoidstiffness of cylinder liner

Core Design Contradiction:

Ease of operationVSStrength

Solution Approach 1:

The scraper ring functionality is merged with the cylinder liner wall itself by forming a protrusion directly from the liner material, eliminating the need for a separate scraper ring component and its associated recess, thereby maintaining material thickness and stiffness while providing the necessary piston guidance and cleaning function

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The scraper ring is extracted from the conventional separate component form and integrated into the cylinder liner wall as a protrusion, removing the need for a recess and maintaining the full material thickness for structural strength

Inventive Principle:

Principle #2Taking out (Extraction)

2Ease of operation

If a scraper ring is provided in the cylinder liner, then the piston can be properly guided and cleaned, but the risk of fatigue cracks increases due to reduced material thickness

Engineering Contradiction:

Improvepiston guidance and cleaning functionalityVSAvoidfatigue strength of cylinder liner

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The scraper ring functionality is merged with the cylinder liner wall itself by forming a protrusion directly from the liner material, eliminating the need for a separate scraper ring component and its associated recess, thereby maintaining material thickness and fatigue strength while providing the necessary piston guidance and cleaning function

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of operation

If a scraper ring is provided in the cylinder liner, then the piston can be properly guided and cleaned, but pressure differences between combustion chamber and piston increase leading to material stress

Engineering Contradiction:

Improvepiston guidance and cleaning functionalityVSAvoidpressure differences in cylinder

Core Design Contradiction:

Ease of operationVSStress or pressure

Solution Approach 1:

The inner diameter of the upper wall portion is locally increased relative to the bottom wall portion, creating a pressure equalization zone that reduces pressure differences and material stress while maintaining the scraper ring functionality through the protrusion

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 improves stiffness and fatigue strength by reducing pressure differences and eliminating the need for separate scraper rings, thereby enhancing durability and reducing fatigue crack risk.

Implementation Method 1

the wall defines a protrusion extending into the bore and beyond the wall in a radially inward direction

Methodology Applied

Scientific EffectRadial extension:

Implementation Method 2

an inner diameter of an entire upper wall portion directly adjacent to the protrusion is larger than an inner diameter of an entire bottom wall portion directly adjacent to the protrusion

Methodology Applied

Scientific EffectPressure equalization:

Data Source

PatentEP4209671B1Cylinder liner with scraper edge but without scraper ring

Publication Date: 2025.08.27 CATERPILLAR ENERGY SOLUTIONS

Figure 1~2
Figure 3~5

AI summary

The present invention pertains to a cylinder liner for a cylinder of a combustion engine and a method for producing a cylinder liner as well as a combustion engine comprising at least one cylinder with a corresponding cylinder liner, in particular to improve stiffness and fatigue strength of the cylinder liner and/or to reduce pressure differences between a combustion chamber and an upper part of a piston. Accordingly, a cylinder liner (10) for a cylinder of a combustion engine is suggested, which comprises a longitudinally extending wall, wherein an inner diameter of the wall defines a bore (12) configured for receiving a piston and wherein the wall defines a protrusion (14) extending into the bore (12) and beyond the wall in a radially inward direction. An upper wall portion (16) directly adjacent to the protrusion (14) and extending to a combustion region end portion of the cylinder liner (10) comprises an inner diameter (18) that is larger than an inner diameter (22) of a bottom wall portion (20) directly adjacent to the protrusion (14) and extending to an opposing end portion of the cylinder liner (10).