Compressor Oil-Return Control Under High Outdoor Temperatures
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Solution Overview
Problem
Air conditioners face failures in commencing the oil-return operation due to abnormally high outdoor air temperatures, leading to prolonged operation without lubricant recovery and potential compressor failure, as existing technologies do not effectively manage high-pressure shutdowns.
Innovation Solution
An air conditioner with an oil-return-operation control portion that performs a forced oil-return operation when outdoor temperatures exceed a set value for a predetermined period, prohibiting the oil-return operation for a certain time afterward to prevent high-pressure shutdown and ensure lubricant recovery, and includes high-pressure-protection-value changing means to prevent compressor halt.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the rotational speed of the compressor is increased to perform oil-return operation, then the lubricant recovery speed is improved, but the refrigerant pressure increases to the extent that it exceeds the high-pressure protection value
Solution Approach 1:
The system performs preliminary assessment of outdoor temperature before initiating oil-return operation. When high outdoor temperature is detected, the system preemptively adjusts the high-pressure protection value to a higher threshold, preventing the pressure from exceeding the protection value during subsequent oil-return operation. This preliminary adjustment ensures that the compressor can increase rotational speed for lubricant recovery without triggering high-pressure shutdown.
2Productivity
If the high-pressure protection value is adjusted to allow higher pressure during oil-return operation, then the oil-return operation can be performed, but the risk of high-pressure damage increases
Solution Approach 1:
The system applies different high-pressure protection values based on local conditions - specifically, the outdoor temperature. When high outdoor temperature is detected, a higher high-pressure protection value is applied specifically during oil-return operation. This localized adjustment allows the system to tolerate higher pressures only when necessary for lubricant recovery, while maintaining normal protection levels during other operations, thus balancing productivity and reliability.
3Reliability
If the oil-return operation is performed frequently to ensure sufficient lubricant in the compressor, then the lubricant level is maintained, but the system may undergo unnecessary high-pressure shutdowns
Solution Approach 1:
The system changes the high-pressure protection value parameter dynamically based on outdoor temperature conditions. When high outdoor temperature is detected, the protection value is raised to allow oil-return operation to proceed without triggering high-pressure shutdown. This parameter change enables the system to maintain lubricant levels through necessary oil-return operations while avoiding unnecessary shutdowns caused by ambient temperature conditions.
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 allows for reliable lubricant recovery before high-pressure shutdown occurs, preventing compressor failure and maintaining air conditioner operation, while minimizing unnecessary oil-return operations and expanding installation regions by managing high outdoor temperatures effectively.
Implementation Method 1
a state in which a detection value from an outdoor air temperature sensor is higher than a set value continues for a predetermined period of time
Implementation Method 2
by increasing the circulated amount and flow speed of refrigerant by increasing the rotational speed of the compressor
Implementation Method 3
a high pressure sensor for protection against high pressure is activated
Data Source
AI summary
In an air conditioner (1) provided with an oil-return-operation control portion (40) that performs an oil-return operation, when oil-return conditions are satisfied, by controlling the rotational speed of a compressor (10), the degree of opening of an expansion valve (31), etc., with a predetermined refrigerant cycle and provided with high-outdoor-air-temperature oil-return operation means (43) for performing a forced oil-return operation via the oil-return-operation control portion (40) when an outdoor temperature increases and a state in which a detection value of an outdoor air temperature sensor (44) is higher than a set value continues for a predetermined period of time, the oil-return operation is prohibited for a certain period of time after performing the forced oil-return operation via the high-outdoor-air-temperature oil-return operation means (43).