Oscillating Piston Compressor Sealing With Resin Ring Geometry

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Solution Overview

Problem

The oscillating piston type compressors face issues with seal ring deformation, breakage, and deteriorating sealing performance due to increased oscillation angles, leading to uneven wear, interference, and reduced followability with the cylinder inner surface, which are not effectively addressed in existing technologies.

Innovation Solution

A compressor design featuring a piston with a spherical outer peripheral surface that slides against the cylinder inner surface, minimizing gaps and interference, using a piston ring with a resin material for reduced friction and thermal expansion, and securing the piston with multiple fastening points to prevent deformation and maintain sealing performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a piston ring with high rigidity is used to maintain structural strength, then the strength is improved, but the followability with the cylinder inner wall surface during oscillation deteriorates and sealing performance greatly decreases when oscillation angle increases

Engineering Contradiction:
Improvepiston ring strengthVSAvoidsealing performance
Core Design Contradiction:
StrengthVSReliability

Solution Approach 1:

The patent changes the material parameter of the piston ring from traditional metal to resin material. This material substitution fundamentally alters the mechanical properties, providing both sufficient strength and high elasticity. The resin material's inherent flexibility allows the piston ring to maintain excellent followability with the cylinder inner wall surface during oscillation, resolving the contradiction between strength and sealing performance.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent employs resin material for the piston ring, which can be considered a composite or specially formulated material designed to exhibit both strength and elasticity. This material choice enables the piston ring to simultaneously achieve structural integrity and adaptive sealing capability across varying oscillation angles.

Inventive Principle:
Principle #40Composite materials

2Productivity

If the oscillation angle of the connecting rod is increased to expand the compressor's operating range, then the productivity is improved, but uneven wear, breakage, and deterioration of seal ring sealing performance occur

Engineering Contradiction:
Improvecompressor operating rangeVSAvoidseal ring performance
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

By changing the material parameter from metal to resin, the piston ring gains superior elasticity and adaptability. This enables the seal to effectively accommodate larger oscillation angles without experiencing uneven wear or breakage, allowing the compressor to operate across a wider range while maintaining reliable sealing performance.

Inventive Principle:
Principle #35Parameter changes

3Reliability

If a lip ring structure is used to improve sealing, then the sealing performance is improved, but the lip portion is subjected to repeated bending deformation leading to fatigue and breakage

Engineering Contradiction:
Improvesealing performanceVSAvoidresistance to bending deformation
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The patent changes the material parameter to resin, which inherently combines elasticity with resistance to repeated bending deformations. Unlike rigid lip rings that fatigue under cyclic loading, the resin material's viscoelastic properties allow it to flex and recover without accumulating damage, eliminating the fatigue breakage issue while maintaining effective sealing.

Inventive Principle:
Principle #35Parameter changes

4Strength

If a piston ring with cutout is provided to reduce interference, then the interference with cylinder is reduced, but the piston ring is not sufficiently supported and deformation occurs causing it to fall into cylinder gaps

Engineering Contradiction:
Improveresistance to interferenceVSAvoidpiston ring positional stability
Core Design Contradiction:
StrengthVSStability of the object's composition

Solution Approach 1:

By changing the material to resin, the piston ring achieves optimal balance between flexibility and structural support. The material's inherent properties provide sufficient support to prevent the ring from deforming and falling into cylinder gaps, while still allowing the cutout design to function in reducing interference with the cylinder.

Inventive Principle:
Principle #35Parameter changes

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 design prevents seal ring deformation and breakage, maintains sealing performance across varying oscillation angles, reduces frictional loss, and extends the maintenance life of components by minimizing cylinder gaps and thermal stress.

Implementation Method 1

using a piston ring with a resin material for reduced friction

Methodology Applied
Scientific EffectFriction: Friction

Implementation Method 2

using a piston ring with a resin material for reduced friction and thermal expansion

Methodology Applied
Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentEP4039977B1compressor
Publication Date: 2025.11.19 HITACHI IND EQUIP SYST CO LTD
  • EP4039977B1 patent drawingFigure 1
  • EP4039977B1 patent drawingFigure 2
  • EP4039977B1 patent drawingFigure 3A

AI summary

There is provided a compressor including: a piston that reciprocates inside a cylinder; a valve plate that closes an end portion of the cylinder; a connecting rod that supports the piston; a crankshaft that applies a rotating force to an end portion of the connecting rod; and a crankcase that rotatably supports the crankshaft. The piston is an oscillating piston that reciprocates while oscillating inside the cylinder according to rotation of the crankshaft. An outer peripheral surface of the piston is a curved surface.