Air Conditioner Defrosting Control Using Dynamic Fan Input Thresholds

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Solution Overview

Problem

Conventional air-conditioning apparatuses fail to initiate defrosting operations at appropriate timing due to a fixed reference current value, which does not account for decreased fan input caused by outdoor fan motor efficiency degradation, leading to inefficient defrosting during heating operations.

Innovation Solution

An air-conditioning apparatus with a controller that adjusts the reference value based on refrigerant temperature, switching the outdoor heat exchanger's operation from evaporator to condenser when the detected fan input exceeds a threshold, allowing for timely and efficient defrosting by varying the reference value with refrigerant temperature.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a fixed reference current value is used for defrosting operation, then the control system is simple, but the defrosting operation cannot be initiated at appropriate timing when fan motor efficiency degrades

Engineering Contradiction:

Improvecontrol system complexityVSAvoiddefrosting operation timing accuracy

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The reference value is changed from a fixed constant to a dynamic value that varies with refrigerant temperature. The controller adjusts the reference value based on the detected refrigerant temperature, allowing the defrosting determination threshold to adapt to different operating conditions and fan motor efficiency levels.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The reference value parameter is modified based on refrigerant temperature conditions. When refrigerant temperature is high, a smaller reference value is used; when refrigerant temperature is low, a larger reference value is used. This parameter change enables accurate defrosting timing across different operating conditions.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the reference value is adjusted based on refrigerant temperature, then defrosting operation timing accuracy improves, but the control system complexity increases

Engineering Contradiction:

Improvedefrosting operation timing accuracyVSAvoidcontrol system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The controller uses feedback from the refrigerant temperature detection to dynamically adjust the reference value. The refrigerant temperature detector continuously monitors temperature, and the controller uses this information to select the appropriate reference value for defrosting determination, creating a closed-loop adaptive control system.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If a fixed reference value is used, then the control logic is simple, but defrosting efficiency decreases due to inability to account for fan motor aging

Engineering Contradiction:

Improvecontrol logic complexityVSAvoiddefrosting efficiency

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

Inventive Principle:

Principle #35Parameter changes

4Reliability

If the reference value varies with refrigerant temperature, then defrosting is performed at appropriate timing, but requires temperature detection and conditional control

Engineering Contradiction:

Improvedefrosting timing accuracyVSAvoiddetection and control complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The refrigerant temperature detector serves multiple functions: it monitors refrigerant temperature for system control and simultaneously provides the basis for dynamic reference value adjustment in defrosting determination. This multi-functionality reduces the need for separate detection systems.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentEP3260790B1Air conditioning device

Publication Date: 2020.03.25 MITSUBISHI ELECTRIC CORP

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AI summary

In an air-conditioning apparatus 100, a compressor 1, an outdoor heat exchanger 3, an indoor heat exchanger 5, and a four-way valve 2 provided closer to the discharge side of the compressor 1 than the outdoor heat exchanger 3 and provided closer to the discharge side of the compressor 1 than the indoor heat exchanger 5 are connected with each other. The air-conditioning apparatus 100 includes a fan 31 configured to deliver air toward the outdoor heat exchanger 3, a power unit configured to supply electric power to the fan 31, a fan input detector configured to detect a physical value related to the electric power supplied to the fan 31, and a controller 80 configured to control the four-way valve 2 to switch between a first operation in which the outdoor heat exchanger 3 functions as an evaporator and a second operation in which the outdoor heat exchanger 3 functions as a condenser. The first operation is switched to the second operation when the physical value detected by the fan input detector is equal to or larger than a reference value. The controller 80 adjusts the reference value so that the reference value when refrigerant flowing through the outdoor heat exchanger 3 has a high temperature is smaller than the reference value when the refrigerant has a low temperature.