Piston Ring Groove Flow Connection for Compressor Sealing

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Solution Overview

Problem

Oil-free piston compressors face a challenge in maintaining effective sealing while minimizing friction and wear as the cylinder chamber pressure increases, leading to conflicting objectives of higher contact pressure for tightness and lower friction to reduce wear and heat generation.

Innovation Solution

A jetted flow connection is introduced between the groove space and the cylinder space, delaying pressure equalization through a throttled nozzle or gap design, which reduces the maximum pressure on the piston ring and minimizes friction and wear.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the piston ring is pressed against the cylinder bore with increased contact force to ensure tight sealing, then sealing effectiveness is improved, but friction losses and wear increase

Engineering Contradiction:
Improvesealing effectivenessVSAvoidfriction losses
Core Design Contradiction:
ReliabilityVSLoss of energy

Solution Approach 1:

The piston ring design incorporates a deformation capability that allows it to adapt its contact force dynamically. The ring can deform elastically under pressure to maintain sealing contact, while the contact force is not continuously high but only increases when needed for sealing, thereby reducing overall friction losses and wear during operation.

Inventive Principle:
Principle #15Dynamics

2Reliability

If the piston ring is pressed against the cylinder bore with increased contact force to ensure tight sealing, then sealing effectiveness is improved, but heat generation and wear increase

Engineering Contradiction:
Improvesealing effectivenessVSAvoidheat generation
Core Design Contradiction:
ReliabilityVSTemperature

Solution Approach 1:

The piston ring utilizes elastic deformation to provide sealing contact force only when necessary. During normal operation, the ring maintains minimal contact to reduce friction and heat generation, while automatically deforming to increase contact force when pressure differentials require enhanced sealing, thus controlling temperature and wear.

Inventive Principle:
Principle #15Dynamics

3Reliability

If the groove width is made larger than the piston ring width to allow pressure-driven sealing, then sealing effectiveness improves with pressure, but uneven wear occurs due to piston ring tilting

Engineering Contradiction:
Improvesealing effectivenessVSAvoiduniformity of wear
Core Design Contradiction:
ReliabilityVSManufacturing precision

Solution Approach 1:

The invention changes the geometric parameters of the piston ring, specifically making the ring width equal to or slightly larger than the groove width. This parameter adjustment prevents ring tilting and ensures uniform contact pressure distribution across the ring-cylinder interface, eliminating uneven wear while maintaining effective sealing through pressure-driven contact force.

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

This solution allows for increased sealing effectiveness with reduced friction losses and wear by controlling the pressure in the groove space, achieving a balance between sealing and friction reduction.

Implementation Method 1

a piston ring (5) made of an elastomer

Methodology Applied
Scientific EffectElasticity: Elasticity

Implementation Method 2

a nozzled flow connection arranged in or on the piston (4) is provided between the groove (8) in the piston and the cylinder chamber (2)

Methodology Applied
Scientific EffectFluid flow through restricted opening: Venturi Effect

Data Source

PatentEP3286461B1Piston-cylinder assembly for a piston compressor having a specific dynamically sealing piston ring
Publication Date: 2019.12.11 KNORR BREMSE SYST FUR SCHIENENFAHRZEUGE GMBH
  • EP3286461B1 patent drawingFigure 1~6

AI summary

The invention relates to a piston-cylinder assembly (1) for a piston compressor, comprising a cylinder chamber (2) delimiting a cylinder running surface (3) for a piston (4) which is provided with at least one circumferential ring groove (7) enclosing a groove area (8) for receiving a piston ring (5) which also borders the groove area (8) for dynamically sealing between the piston (4) and the cylinder running surface (3), wherein, between the groove area (8) in the piston (4) and the cylinder chamber (2), a sprayed flow connection arranged in or on the piston (4) is provided in order to delay a pressure compensation in the groove area (8) in relation to the cylinder chamber (2) in a time-controlled manner.