Hermetic Rotary Compressor Nested End Case Design
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Solution Overview
Problem
Hermetic rotary compressors face challenges in enhancing pressure resistance without upsizing, particularly when using carbon dioxide refrigerants, which require higher pressure resistance than HFC-based refrigerants, leading to increased oil quantity and weight in vertically-installed structures.
Innovation Solution
The design incorporates a hermetic case with dish-like end cases and increased wall thickness, positioning the second compression mechanism section inside the lower end case to maintain compactness and reduce oil retention, utilizing the internal pressure for blade operation without additional coil springs, and optimizing the shape to enhance pressure resistance without excessive size increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the shape of the corner part of the end case is made more similar to a spherical shape to enhance pressure resistance, then the pressure resistance of the hermetic case is improved, but the end case becomes larger in the axial direction, causing the hermetic rotary compressor to be upsized
Solution Approach 1:
The second compression mechanism section is nested inside the lower end case, with the cylinder positioned within the end case structure. This allows the compression mechanism to be integrated into the existing space without requiring additional axial length, thereby maintaining compact dimensions while supporting high pressure resistance requirements
Solution Approach 2:
The end case is designed with locally optimized corner parts that have enhanced structural properties for pressure resistance, rather than making the entire end case spherical or uniformly larger. This localized optimization allows improved strength without proportionally increasing the overall axial dimensions
2Strength
If the hermetic case becomes larger in the axial direction, then the pressure resistance is improved, but the quantity of oil to be sealed in the hermetic case is increased, making the hermetic rotary compressor heavier
Solution Approach 1:
The second compression mechanism section is nested inside the lower end case, utilizing the space within the end case structure. This integration prevents the need for additional axial space that would otherwise be required, thereby limiting the increase in oil quantity and compressor weight while still achieving the necessary pressure resistance
Solution Approach 2:
Instead of increasing the axial dimension to improve pressure resistance, the design utilizes radial and circumferential space optimization through the nested configuration of the compression mechanism within the end case, thereby avoiding the weight penalty associated with increased axial length and oil quantity
3Strength
If the wall thickness of the hermetic case is increased to enhance pressure resistance, then the pressure resistance is improved, but the hermetic case becomes larger and heavier
Solution Approach 1:
The second compression mechanism section is positioned inside the lower end case, effectively utilizing the internal space. This nested arrangement allows the hermetic case to maintain compact external dimensions while providing sufficient wall thickness for pressure resistance, as the compression mechanism is integrated within the existing case volume rather than requiring additional space
Data Source
Figure 1
Figure 2
AI summary
Provided are a hermetic rotary compressor configured so that the pressure resistance of a hermetic case is increased and so that the hermetic case will not become large, and a refrigeration cycle device provided with the hermetic rotary compressor. A hermetic case (10) is provided with a main case (10a) and an end case (10c) which is fitted in the main case (10a). A first compression mechanism (18A) is provided with a first cylinder (21). A second compression mechanism (18B) is provided with a second cylinder (22). The entire first cylinder (21) is accommodated within the main case (10a) in the axial direction of a rotating shaft (13). At least a part of the second cylinder (22) is inserted in the end case (10c). The maximum distance L from the center of the rotating shaft (13) to the outer periphery of the first cylinder (21) is greater than the maximum distance M from the center of the rotating shaft (13) to the inner periphery of the end case (10c).