Laser-Hardened Cylinder Bore Patterning to Reduce Cracking

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Solution Overview

Problem

Existing methods for hardening cylinder bore surfaces in internal combustion engines, such as induction hardening, lead to brittleness and stress fractures, while also being difficult to control, especially for multiple cylinders.

Innovation Solution

A laser-hardened patterned array of cycloidal features is formed on the cylinder bore surface, which includes a first microstructure of pearlite and cementite with graphite flakes and a second microstructure of tempered martensite, arranged in a specific geometric pattern to reduce stress and improve wear resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If induction hardening is used to harden cylinder bore surfaces, then hardness and wear resistance are improved, but brittleness and stress fractures increase

Engineering Contradiction:

ImprovehardnessVSAvoidbrittleness

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The cylinder bore surface is divided into multiple discrete hardening zones arranged in a pattern, rather than hardening the entire surface uniformly. This segmentation allows different regions to have different microstructures, reducing overall brittleness while maintaining localized hardness where needed for wear resistance

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the cylinder bore surface are given different properties through selective hardening. The hardening zones provide high hardness and wear resistance, while the non-hardened zones maintain lower brittleness, creating a gradient of properties throughout the surface

Inventive Principle:

Principle #3Local quality

2Duration of action of stationary object

If induction hardening is used to harden cylinder bore surfaces, then wear resistance is improved, but stress fractures and cracking occur

Engineering Contradiction:

Improvewear resistanceVSAvoidstress fractures

Core Design Contradiction:

Duration of action of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The continuous hardened surface is segmented into discrete zones with spacing between them. This segmentation prevents the propagation of stress fractures across the entire surface, as the non-hardened zones act as stress relief regions that interrupt crack paths

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patterned arrangement of hardening zones creates built-in stress relief regions before stress fractures can develop and propagate. The non-hardened zones between hardening zones serve as predetermined cushioning areas that absorb and distribute tensile stresses

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Productivity

If induction hardening is used to treat multiple cylinders, then productivity is improved, but control precision and placement accuracy deteriorate

Engineering Contradiction:

Improvetreatment speedVSAvoidcoil placement accuracy

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The mechanical system of physically placing and positioning induction coils in each cylinder bore is replaced with a laser-based system. The laser can be precisely controlled and directed to create the desired hardening patterns without the need for manual coil placement, thereby maintaining high productivity while improving placement accuracy

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 laser-hardened cycloidal features reduce the risk of cracking, improve wear resistance, and distribute tensile stresses more evenly, while also allowing for precise control of martensite formation and tempering to achieve optimal hardness and reduced brittleness.

Implementation Method 1

A method of forming a patterned array on a cylinder bore surface includes impinging a bore surface with a laser

Methodology Applied

Scientific EffectLaser heating: Laser

Implementation Method 2

The process develops a relatively fine martensitic structure at the cylinder bore surface through heating and then quenching

Methodology Applied

Scientific EffectMartensitic transformation: Phase Change

Implementation Method 3

the plurality of cycloidal features exhibits a second microstructure including tempered martensite

Methodology Applied

Scientific EffectTempering: Heat Treatment

Data Source

PatentUS12241431B1Laser hardened pattern array in cylinder bores

Publication Date: 2025.03.04 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

An engine block for a vehicle includes a bore surface defining a cylinder bore. The bore surface exhibits a first microstructure and includes a pattern of a plurality of cycloidal features formed in the bore surface. The plurality of cycloidal features each exhibit a first length in a first axis and a second length in a second axis arranged 90 degrees from the first axis. The plurality of cycloidal features also exhibit a ratio of the first length to the second length in a range of 1:1.5 to 1.5:1. The plurality of cycloidal features further exhibit a second microstructure including tempered martensite, wherein the second microstructure is different from the first microstructure. The engine block is included in a vehicle. The cycloidal features are formed with a laser.