Reciprocating Compressor Oil Coalescing to Protect Cylinders

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Solution Overview

Problem

Hermetic reciprocating piston compressors face challenges in preventing oil from entering the cylinders, which can reduce refrigerant flow efficiency and require additional oil return mechanisms, increasing manufacturing costs.

Innovation Solution

Incorporating a coalescing mechanism within the compressor case, specifically a lip structure between the rotor and stator, to separate oil from the refrigerant flow before it enters the cylinders, utilizing a check valve and centrifugal pump to return separated oil to the crankcase, thereby preventing oil entry and potentially eliminating or downsizing external separators.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a coalescing mechanism is added to separate oil from refrigerant flow, then oil separation effectiveness is improved, but device complexity increases

Engineering Contradiction:

Improveoil separation effectivenessVSAvoidcompressor structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines the oil separation function with the existing crankcase structure by forming a coalescing lip directly on the crankcase wall. This integrates the separator into the compressor housing, eliminating the need for external separators and reducing overall device complexity while maintaining effective oil separation.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The crankcase wall serves multiple functions: it provides structural support, defines the crankcase volume, and now also provides the coalescing lip for oil separation. This multi-functionality reduces the number of separate components needed, resolving the contradiction between improved separation and increased complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Productivity

If external oil separators are used to prevent oil from entering cylinders, then refrigerant flow efficiency is improved, but manufacturing cost increases

Engineering Contradiction:

Improverefrigerant flow efficiencyVSAvoidmanufacturing cost

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The oil separation function is merged into the crankcase structure itself through the coalescing lip, eliminating the need for separate external oil separators. This integration reduces manufacturing costs by reducing the number of parts while maintaining the ability to prevent oil from entering the cylinders and protecting refrigerant flow efficiency.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The oil separation function is extracted from external components and integrated directly into the crankcase wall structure. This eliminates the need for separate external separators, reducing manufacturing complexity and cost while maintaining effective oil removal from the refrigerant flow.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If additional oil return mechanisms are added, then oil management is improved, but device complexity increases

Engineering Contradiction:

Improveoil managementVSAvoidnumber of components

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The oil return function is combined with the crankcase structure by using the coalescing lip to direct separated oil back into the crankcase. This eliminates the need for separate oil return mechanisms while maintaining effective oil management, as the lip structure itself provides the return path.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The coalescing lip structure on the crankcase wall automatically directs separated oil back into the crankcase without requiring external pumps or additional mechanisms. The structure serves itself by providing both the separation surface and the return path, reducing component count while improving oil management.

Inventive Principle:

Principle #25Self-service

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

Effectively prevents oil from entering the cylinders, improving refrigerant flow efficiency and reducing system manufacturing costs by integrating oil separation directly into the compressor design.

Implementation Method 1

The wall bears means for coalescing oil entrained in a flow, which flow exits a gap between the rotor and the stator

Methodology Applied

Scientific EffectCoalescence: Coagulation

Implementation Method 2

utilizing a check valve and centrifugal pump to return separated oil to the crankcase

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentUS8850835B2Reciprocating refrigeration compressor oil separation

Publication Date: 2014.10.07 CARRIER CORP

AI summary

A compressor (20) has a case (22) and a crankshaft (38). The case has a number of cylinders (30, 32). For each of the cylinders, the compressor includes a piston (34) mounted for reciprocal movement at least partially within the cylinder. A connecting rod (36) couples each piston to the crankshaft. An electric motor compartment (50) of the case has a stator (42) and a rotor (40). The rotor is mounted to the crankshaft. The case has a wall (56) between the motor compartment and a crankcase compartment/sump (52). The wall bears a feature (120, 132; 420; 460) for coalescing oil entrained in a refrigerant flow (522), which flow exits the gap (90) between the rotor and the stator to prevent the oil from entering the cylinders.