Compressive Preload Plug for High-Pressure Pump Bore

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Solution Overview

Problem

High-pressure pumps used in common rail fuel systems face structural integrity issues due to high tensile stresses caused by increasing injection pressures, which conventional methods like bead blasting and shot peening struggle to adequately address, especially in deep, small bore areas.

Innovation Solution

A system comprising a body with a first bore exposed to high tensile stresses and a second bore with a plug that applies a compressive preload by forcing its end against the bottom surface of the second bore, counteracting the tensile stresses with a desired magnitude of compressive force.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If conventional manufacturing techniques like bead blasting and shot peening are used to impart residual compressive stresses, then some counteraction to tensile stresses is achieved, but the magnitude of residual compressive stresses is limited and insufficient to counter the continuously increasing tensile stresses from higher injection pressures

Engineering Contradiction:

Improveresidual compressive stress magnitudeVSAvoidtensile stress from high injection pressure

Core Design Contradiction:

StrengthVSStress or pressure

Solution Approach 1:

The plug is pre-installed in the second bore and pre-tensioned to apply compressive preload to the first bore area before the pump operates under high injection pressure. This preliminary counteracting force offsets the tensile stresses that will occur during operation, preventing stress-related failures.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The invention changes the magnitude parameter of compressive stress by using a mechanically adjustable plug system that can generate much higher compressive forces than conventional surface treatments. The plug can be tensioned to apply precise, high-magnitude compressive preload that scales with injection pressure requirements.

Inventive Principle:

Principle #35Parameter changes

2Strength

If conventional manufacturing techniques like shot peening or bead blasting are used to impart residual compressive stress, then some preload is applied, but when the high pressure fluid area is located deep within a small bore, it becomes difficult to apply the technique effectively

Engineering Contradiction:

Improvecompressive preload applicationVSAvoidaccessibility to deep bore areas

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The plug acts as an intermediary element installed within the second bore that indirectly applies compressive force to the first bore area. Instead of directly treating the deep bore area with surface techniques, the plug mediates the stress application through mechanical force transmission from the second bore to the first bore region.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention segments the stress application function into two separate bores: the first bore that receives the compressive preload and the second bore that houses the plug mechanism. This segmentation allows the plug to be accessed and adjusted through the second bore while applying force to the target area in the first bore, solving the accessibility problem.

Inventive Principle:

Principle #1Segmentation

3Reliability

If the injection pressure is increased to achieve more complete fuel-air mixture, then emission regulations are met, but the tensile stresses within the pump structural portions increase significantly

Engineering Contradiction:

Improveemission complianceVSAvoidtensile stress in pump structure

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The plug applies a counteracting compressive force that balances the tensile stress generated by high injection pressure. This counterweight effect allows the pump to operate at high injection pressures needed for emission compliance while the structural portions experience reduced net stress due to the opposing compressive preload.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

Data Source

PatentUS8864478B2System and method for preloading a high stress area of a component

Publication Date: 2014.10.21 CATERPILLAR INC

AI summary

The exposure of components to high-pressure fluids can result in the application of high tensile stresses to those components, which may lead to reduced life. The preload system described herein helps to reduce the magnitude of those tensile stresses by providing a body and a plug. The body includes a first bore and a second bore. The first bore is configured to be exposed to high tensile stresses. The second bore includes a first engagement structure and a bottom surface near a first portion of the first bore. The plug includes a second engagement structure and a first end. The second engagement structure engages the first engagement structure to force the first end of the plug against the bottom surface of the bore. The force of the plug against the bottom surface of the bore applies a compressive preload to the first portion of the first bore.