Flexible Resin Piston Layer for Stirling Engine Gas Lubrication

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Solution Overview

Problem

In stirling engines, foreign matters like metallic pieces can enter the clearance between the piston and cylinder during gas lubrication, leading to increased bearing stress and adhesion, which complicates heat recovery efficiency and is difficult to prevent due to the small size of the clearance.

Innovation Solution

A gas lubrication structure with a flexible resin layer on the piston's outer surface, having a linear expansion coefficient higher than the piston material, is used to create and maintain a clearance that prevents foreign matter adhesion, even under heat expansion, by ensuring the layer's thickness is equal to or greater than the initial clearance and allowing it to expand and accommodate foreign objects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If gas lubrication is performed between the piston and cylinder, then friction is reduced, but foreign matter can enter the clearance and cause adhesion

Engineering Contradiction:

Improvefriction lossVSAvoidforeign matter adhesion

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

A flexible resin layer is applied to the outer peripheral surface of the piston, forming a thin film that can deform to accommodate foreign matter in the clearance without causing adhesion, while maintaining the gas lubrication function

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The resin layer's linear expansion coefficient is designed to be larger than that of the piston base material, allowing the clearance to expand with temperature increases and prevent foreign matter adhesion during engine operation

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If the clearance between piston and cylinder is reduced, then gas lubrication efficiency is improved, but foreign matter entry becomes more difficult to prevent

Engineering Contradiction:

Improvegas lubrication efficiencyVSAvoidforeign matter entry

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The flexible resin layer acts as a buffer that can deform to accommodate foreign matter, allowing the use of smaller clearances for efficient gas lubrication while preventing foreign matter from causing adhesion

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The resin layer is pre-installed on the piston surface to provide cushioning protection against foreign matter before it can cause adhesion, allowing smaller clearances to be used without increasing foreign matter risks

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If a resin layer is added to the piston, then foreign matter adhesion is prevented, but manufacturing complexity increases

Engineering Contradiction:

Improveforeign matter resistanceVSAvoidpiston manufacturing

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

A thin resin layer is applied to the piston surface, adding minimal manufacturing steps while providing effective foreign matter adhesion prevention through the layer's flexibility and expansion properties

Inventive Principle:

Principle #30Flexible shells and thin films

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

This solution effectively suppresses foreign matter entry and adhesion, enhancing the engine's endurance and maintaining low friction, thus improving the heat recovery efficiency and preventing foreign matter-induced performance degradation.

Implementation Method 1

a layer (60) arranged on an outer peripheral surface of the piston, and made of a flexible material with a linear expansion coefficient larger than that of a base material of the piston

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

made of a flexible material with a linear expansion coefficient larger than that of a base material of the piston

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS8763514B2Gas lubrication structure for piston, and stirling engine

Publication Date: 2014.07.01 TOYOTA JIDOSHA KK

AI summary

A gas lubrication structure is provided with a high-temperature-side cylinder, an expansion piston lubricated relative to the high-temperature-side cylinder by gas, and a layer provided to the outer peripheral surface of the expansion piston and composed of a material flexible and having a higher linear expansion coefficient than the base material of the expansion piston. The thickness of the layer under normal temperatures is not less than the size of the clearance formed between the layer and the high-temperature-side cylinder. Also, even if the layer is thermally expanded under use conditions, the layer under normal temperatures has a thickness enabling a clearance to be formed between the layer and the high-temperature-side cylinder.