Valve Under-Head Fillet Contour for Chordal Stress Mitigation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Gas exchange valves in internal combustion engines are prone to fatigue failure due to harsh operating conditions, such as high temperatures and pressures, leading to significant mechanical stress and reduced service life.

Innovation Solution

The design incorporates a valve head with an under-head fillet formed by a stress-diffusing contour, featuring a blend angle of 18° to 35° and a larger radius of curvature, which distributes stress and reduces fatigue by creating a chordal stress zone that mitigates the impact of mechanical forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional valve designs are used, then manufacturing is simpler, but fatigue life is reduced due to high chordal stresses

Engineering Contradiction:

Improvefatigue lifeVSAvoidvalve head geometry complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies local quality by creating a specific fillet geometry with a 15-25 degree blend angle at the critical under-head region where chordal stresses concentrate. This localized geometric modification optimizes stress distribution precisely where needed without changing the overall valve design, thereby improving fatigue life while maintaining manufacturing feasibility.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent utilizes curvature by specifying a fillet radius of curvature between 0.040-0.080 inches at the under-head region. This curved transition replaces sharp corners with smooth radii, distributing chordal stresses more evenly and preventing stress concentration points that would lead to fatigue failure.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Reliability

If the under-head fillet blend angle is increased to reduce stress, then fatigue life improves, but manufacturing precision requirements increase

Engineering Contradiction:

Improvefatigue lifeVSAvoidblend angle tolerance

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent optimizes parameters by specifying a blend angle range of 15-25 degrees and a fillet radius of 0.040-0.080 inches. These parameter ranges are carefully selected to achieve stress reduction while remaining manufacturable with standard machining tolerances, balancing performance improvement with manufacturing capability.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10844758B2Engine and gas exchange valve with under-head fillet contoured for chordal stress mitigation

Publication Date: 2020.11.24 CATERPILLAR INC

AI summary

A gas exchange valve in an internal combustion engine includes a valve head having a sealing face structured to contact a valve seat and defining a face angle. The valve head further includes an under-head fillet transitioning from the inner sealing face to a valve stem, and defining a chordal stress zone within the under-head fillet. The under-head fillet is formed by a material distributed according to a stress-diffusing contour within the chordal stress zone, and is blended with the inner sealing face at a blend angle that is less than the face angle and is in a range of about 18° to about 35°. The valve head contour is associated with resistance to chordal stress-induced fatigue failure.