Rotary Compressor Crankshaft Sizing for Lower Friction Loss
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Solution Overview
Problem
Rotary compressors experience excessive friction loss due to the crankshaft, which affects performance and reliability, with large diameters causing high friction and small diameters leading to deformation and processing difficulties.
Innovation Solution
The crankshaft design features a long shaft and short shaft with outer-to-inner diameter ratios ranging from 0.075 to 0.129 and 0.056 to 0.109, respectively, reducing contact area and friction loss while maintaining structural strength and ease of processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the outer diameter of the crankshaft is increased, then the structural strength and rigidity are improved, but the friction loss increases excessively
Solution Approach 1:
The patent applies parameter changes by optimizing the outer diameter of the crankshaft to a specific range (0.075-0.129 times the inner diameter of the compressor housing) rather than using a fixed large diameter. This parameter optimization reduces the contact area between the crankshaft and compressor housing, thereby reducing friction loss while maintaining sufficient structural strength through precise dimensional control.
2Loss of energy
If the outer diameter of the crankshaft is decreased, then the friction loss is reduced, but the deformation increases and processing becomes difficult
Solution Approach 1:
The patent resolves this contradiction by establishing a minimum threshold for the crankshaft outer diameter ratio (0.075 times the housing inner diameter). This parameter setting ensures the crankshaft maintains sufficient structural rigidity to prevent excessive deformation during operation and processing, while still being small enough to reduce friction loss compared to conventional designs.
3Loss of energy
If the crankshaft outer diameter is optimized to reduce friction loss, then the coefficient of performance is enhanced, but the processing difficulty increases
Solution Approach 1:
The patent balances processing ease with friction reduction by setting the crankshaft outer diameter within an optimized range (0.075-0.129 times housing inner diameter). This parameter range is small enough to significantly reduce friction loss and improve COP, but large enough to maintain adequate structural rigidity that prevents excessive deformation during machining and assembly operations.
Data Source
Figure 1
Figure 2~3
AI summary
Disclosed are a crankshaft and a rotary compressor comprising the crankshaft. The crankshaft (1) comprises a long shaft (11) and a short shaft (12). A ratio of an external diameter of the long shaft (11) to an inner diameter of a compressor shell (2) is less than 0.14 and greater than 0.07, and a ratio of an external diameter of the short shaft (12) to the inner diameter of the compressor shell (2) is less than or equal to 0.12 and greater than 0.05, thereby reducing the area of a contact surface and a frictional loss of the crankshaft (1) during work, thus the coefficient of performance (COP) of the compressor is improved.