Rotary Compressor Cylinder Bore Deformation Control

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Solution Overview

Problem

Conventional rotary compressors experience deformation in the cylinder bore due to bolt fastening, leading to increased leakage of compressed fluid and reduced compression efficiency, as the inner diameter changes, necessitating a solution to suppress this deformation and maintain uniform clearance.

Innovation Solution

A deformation absorbing part, such as a through-slit or cutaway portion, is introduced around the bolt hole to redirect deformation radially outward or circumferentially, reducing the rigidity of the affected area and preventing bulging of the cylinder bore, thereby maintaining uniform clearance and reducing fluid leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If bolt fastening is used to integrate the rotary compression mechanism, then the structural strength and assembly reliability are improved, but deformation of the cylinder bore occurs leading to increased fluid leakage and reduced compression efficiency

Engineering Contradiction:
Improveassembly reliabilityVSAvoidcompression efficiency
Core Design Contradiction:
ReliabilityVSLoss of energy

Solution Approach 1:

The cylinder main body is segmented into different functional zones: a deformation absorbing part with reduced rigidity positioned radially outward from the bolt hole, and a cylinder chamber part with maintained rigidity. This segmentation allows localized deformation absorption without compromising the overall structural integrity or causing harmful deformation in the compression zone.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The cylinder main body is designed with non-uniform rigidity distribution: the deformation absorbing part has lower rigidity (through reduced thickness or cutaway portions) to accommodate bolt fastening deformation, while the cylinder chamber part maintains higher rigidity to preserve bore roundness and compression efficiency. This local quality differentiation resolves the contradiction between assembly reliability and energy loss.

Inventive Principle:
Principle #3Local quality

2Reliability

If the rotational axial center of the rotor is adjusted to secure clearance in the region around the bolt hole, then the risk of rotor contact with the cylinder wall is reduced, but the clearance dimension increases in other regions leading to increased leakage and reduced compression efficiency

Engineering Contradiction:
Improverotor clearance reliabilityVSAvoidcompression efficiency
Core Design Contradiction:
ReliabilityVSLoss of energy

Solution Approach 1:

The clearance management is segmented into two zones: the bolt hole region where the deformation absorbing part compensates for deformation to maintain clearance, and the remaining cylinder chamber region where uniform clearance is preserved. This eliminates the need for global rotor repositioning that would increase clearance and leakage in non-critical zones.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The deformation absorbing part provides localized compensation for clearance variation around the bolt hole, allowing the rotor to maintain optimal clearance positioning without compromising clearance uniformity in other regions. This local quality approach prevents the energy loss associated with increased clearance while ensuring reliable rotor-cylinder clearance.

Inventive Principle:
Principle #3Local quality

3Manufacturing precision

If the rigidity of the cylinder main body is reduced around the bolt hole to absorb deformation, then the deformation due to bolt fastening is redirected away from the cylinder bore, but the structural strength in that region is reduced

Engineering Contradiction:
Improvecylinder bore roundnessVSAvoidstructural strength
Core Design Contradiction:
Manufacturing precisionVSStrength

Solution Approach 1:

The cylinder main body is divided into a deformation absorbing part with reduced rigidity and a cylinder chamber part with maintained structural strength. The deformation absorbing part acts as a sacrificial zone that accommodates bolt fastening deformation through reduced thickness or cutaway portions, while the cylinder chamber part retains full structural integrity for reliable compression operation.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Different rigidity and strength characteristics are assigned to different regions: the deformation absorbing part has locally reduced rigidity to accommodate deformation, while the cylinder chamber part maintains high strength and rigidity. This local quality differentiation preserves cylinder bore roundness and manufacturing precision without compromising overall structural strength.

Inventive Principle:
Principle #3Local quality

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 solution effectively suppresses deformation of the cylinder bore, ensuring uniform clearance and reducing fluid leakage, thereby enhancing the compression efficiency of the rotary compressor by directing deformation away from the axial center, and also serves as a heat-insulating layer to improve performance.

Implementation Method 1

a deformation absorbing part which leads deformation due to bolt fastening toward at least one of a radially outward direction and a circumferential direction is provided in a region around a bolt hole of a cylinder main body

Methodology Applied
Scientific EffectDeformation: Deformation

Implementation Method 2

reducing the rigidity of the affected area and preventing bulging of the cylinder bore

Methodology Applied
Scientific EffectRigidity reduction:

Implementation Method 3

also serves as a heat-insulating layer to improve performance

Methodology Applied
Scientific EffectThermal insulation: Thermal Insulation

Data Source

PatentEP2918773B1Rotary compressor
Publication Date: 2020.01.01 MITSUBISHI HEAVY IND THERMAL SYST
  • EP2918773B1 patent drawingFigure 1(a)~1(b)
  • EP2918773B1 patent drawingFigure 2~3
  • EP2918773B1 patent drawingFigure 4~5

AI summary

In this rotary compressor, a rotary compression mechanism driven through a crankshaft coupled with a drive source includes: a cylinder main body (9) forming a cylinder chamber (8); bearings installed respectively on upper and lower surfaces of the cylinder main body (9) and supporting the crankshaft; and a rotor fitted in an eccentric part of the crankshaft and rotating inside the cylinder chamber (8), at least the cylinder main body (9) and the bearings being integrated by fastening a bolt penetrating in the axial direction of the crankshaft. A deformation absorbing part such as a through-slit (20), which leads deformation during bolt fastening in at least one of the radially outward direction and the circumferential direction, is provided in a region around a bolt hole (9a) of the cylinder main body (9).