Refrigeration cycle apparatus

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Solution Overview

Problem

Refrigeration oil in compressors experiences increased viscosity at or below its pour point, leading to abnormal compressor stops, reduced user comfort, and potential lubrication failures due to overcurrent and uneven oil distribution, which affects the reliability of refrigeration cycle apparatuses, especially in low-temperature conditions.

Innovation Solution

A refrigeration cycle apparatus equipped with a detection unit to monitor oil temperature, a heating unit to maintain appropriate viscosity, and a controller to manage heating based on detected temperatures, ensuring the oil remains above its pour point to prevent overcurrent and ensure uniform lubrication.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the refrigeration cycle apparatus operates in low-temperature conditions, then the operating range is extended, but the refrigeration oil viscosity increases causing overcurrent and abnormal compressor stops

Engineering Contradiction:

Improveoperating rangeVSAvoidcompressor operation stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The system performs preliminary heating of the refrigeration oil when the compressor shell temperature is below a predetermined threshold (e.g., -30°C). The controller activates the heating device in advance to raise the oil temperature above the pour point, preventing viscosity-related overcurrent and abnormal stops before they occur, thus ensuring reliable operation in low-temperature conditions

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system changes the temperature parameter of the refrigeration oil by activating a heating device when the compressor shell temperature drops below a predetermined value. This parameter change raises the oil temperature above its pour point, reducing viscosity to appropriate levels and preventing overcurrent conditions, thereby maintaining compressor reliability across extended operating ranges

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the refrigeration oil temperature is low, then the compressor can operate in cold climates, but the oil viscosity increases causing insufficient lubrication and bearing wear

Engineering Contradiction:

Improvecold climate operationVSAvoidbearing lubrication

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The system performs preliminary heating of the refrigeration oil when the compressor shell temperature is below a predetermined threshold. By raising the oil temperature above the pour point in advance, the system ensures adequate lubrication viscosity is achieved before the compressor operates, preventing bearing wear and insufficient lubrication in cold climate conditions

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system changes the temperature parameter of the refrigeration oil through heating when the compressor shell temperature is low. This parameter change ensures the oil viscosity remains within the appropriate range for effective lubrication, preventing bearing wear and maintaining reliability in cold climate operations

Inventive Principle:

Principle #35Parameter changes

3Temperature

If the refrigeration oil viscosity is high, then the oil remains in cold conditions, but the driving torque increases causing motor overcurrent

Engineering Contradiction:

Improveoil temperatureVSAvoiddriving torque

Core Design Contradiction:

TemperatureVSPower

Solution Approach 1:

The system changes the temperature parameter of the refrigeration oil by activating a heating device when the compressor shell temperature drops below a predetermined value. This parameter change reduces the oil viscosity, thereby decreasing the driving torque required and preventing motor overcurrent in low-temperature conditions

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 maintains appropriate oil viscosity, enhancing the reliability of refrigeration cycle apparatuses by preventing abnormal stops and reducing wear, thus improving operational comfort and reliability in low-temperature conditions.

Implementation Method 1

The heating unit is configured to heat the refrigeration oil

Methodology Applied

Scientific EffectHeating: Heating

Data Source

PatentUS11486620B2Refrigeration cycle apparatus

Publication Date: 2022.11.01 MITSUBISHI ELECTRIC CORP

AI summary

In a refrigeration cycle apparatus, refrigerant circulates successively through a compressor, a condenser, an expansion valve, and an evaporator. The refrigeration cycle apparatus includes a detection unit, a heating unit, and a controller. The detection unit is configured to detect a temperature of refrigeration oil in the compressor. The heating unit is configured to heat the refrigeration oil. The controller is configured to operate the heating unit when the temperature detected by the detection unit is lower than a pour point of the refrigeration oil, and to stop the heating by the heating unit when the temperature detected by the detection unit reaches the pour point. Preferably, the heating unit includes a heater provided on an outer side of a compressor casing and at a lower portion of a motor unit.