Two-Stage Compressor Suction Layout for Low Oil Carryover

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Solution Overview

Problem

In existing two-stage compressors, refrigerant accompanied by oil is sucked into the high-stage-side compression mechanism, leading to performance degradation.

Innovation Solution

A compressor design with a cover having a suction opening positioned below the upper coil end of the electric motor and a baffle plate to separate oil from refrigerant, guiding refrigerant to the high-stage-side compression mechanism while minimizing oil guidance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a flow restriction plate with conical shape is provided to restrict refrigerant flow to the scroll compression mechanism, then oil guidance to the high-stage-side compression mechanism is reduced, but the suction opening position remains above the coil end allowing oil to be sucked

Engineering Contradiction:

Improvecompression mechanism performanceVSAvoidflow restriction structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The invention extracts the harmful element (oil) from the refrigerant flow by providing a separate oil return path. The oil separation chamber and oil return hole allow oil to be separated and returned to the oil reservoir independently from the refrigerant flow path, thereby preventing oil from being guided to the high-stage-side compression mechanism without requiring complex flow restriction structures

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention introduces an intermediary structure (oil separation chamber and baffle plate) between the low-stage-side and high-stage-side compression mechanisms. This intermediary system separates oil from refrigerant and provides a dedicated return path, acting as a mediator that prevents oil contamination of the high-stage mechanism while maintaining refrigerant flow

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If the suction opening is positioned above the coil end to allow refrigerant suction, then refrigerant can be guided to the high-stage-side compression mechanism, but oil accompanied by refrigerant is also sucked

Engineering Contradiction:

Improverefrigerant compression efficiencyVSAvoidhigh-stage-side compression mechanism performance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The invention segments the housing into distinct functional zones: a low-stage-side compression mechanism chamber, a high-stage-side compression mechanism chamber, and an oil separation chamber. The baffle plate creates spatial separation that allows refrigerant to flow to the high-stage mechanism while preventing oil from following the same path, thus segmenting the harmful oil flow from the useful refrigerant flow

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The baffle plate and oil separation chamber serve as intermediary structures that mediate between the low-stage discharge and high-stage suction. They allow refrigerant to pass through while intercepting and redirecting oil to the return path, acting as a filtering intermediary that protects the high-stage mechanism

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Reduces oil guided to the high-stage-side compression mechanism, enhancing compressor performance by separating oil effectively from refrigerant flow.

Implementation Method 1

the suction opening of the cover is provided on an inner side of a coil end (39b) of the electric motor and below an upper end of the coil end

Methodology Applied

Scientific EffectGravity: Gravitation

Implementation Method 2

a baffle plate to separate oil from refrigerant, guiding refrigerant to the high-stage-side compression mechanism while minimizing oil guidance

Methodology Applied

Scientific EffectDensity difference separation: Density Gradient

Data Source

PatentEP4400722B1compressor

Publication Date: 2026.02.04 MITSUBISHI HEAVY IND THERMAL SYST

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AI summary

Provided is a compressor capable of introducing as little oil as possible to a higher-side compressing mechanism. A compressor (1) comprises: a rotary compressing mechanism (12) connected to a lower end of a rotation shaft (15), and which compresses and ejects a refrigerant into a housing (11); a scroll compressing mechanism (13) connected to an upper end of the rotation shaft (15), and which takes in and compresses the refrigerant ejected into the housing (11); and a cover (45) having, at a lower end thereof, an intake opening (45a) through which the refrigerant ejected from the scroll compressing mechanism (13) is taken in from around the rotation shaft (15), and partitioning a space inside the housing (11) so as to guide the refrigerant to an intake side of the scroll compressing mechanism (13). The intake opening (45a) of the cover (45) is provided inside an upper coil end (39b) of an electric motor (14) and below an upper end of the upper coil end (39b).