Rotary Compressor Drive Shaft Segmentation for Bearing Load
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Solution Overview
Problem
In rotary compressors, increasing eccentricity to enhance capacity without increasing sliding loss is challenging, as it leads to reduced load capacity of main bearings, compromising reliability due to the need for notching the main shaft portion, which affects the bearing's functionality and piston assembly.
Innovation Solution
A rotary compressor design with a first coupling portion between the eccentric and shaft portions, where the outer surface of the coupling portion does not extend beyond the eccentric portion, allowing increased eccentricity without diameter increase, and a circumferentially extending groove on the piston to facilitate assembly and reduce friction loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the eccentricity is increased to enhance capacity, then the compressor capacity increases, but the load capacity of the main bearing is reduced
Solution Approach 1:
The drive shaft is segmented into multiple portions: a main shaft portion with a large diameter for bearing support, and an eccentric portion with a smaller diameter for piston engagement. This segmentation allows the main shaft to maintain structural integrity and bearing load capacity while the eccentric portion achieves the required eccentricity for enhanced compressor capacity.
Solution Approach 2:
Different portions of the drive shaft are given different diameters and functions. The main shaft portion has a larger diameter to support the main bearing and maintain load capacity, while the eccentric portion has a smaller diameter to achieve the required eccentricity. This local differentiation resolves the contradiction between bearing load capacity and compressor capacity.
2Ease of manufacture
If the outer surface of the main shaft portion is cut out to allow piston assembly, then the piston can be assembled to the eccentric portion, but the main bearing becomes extremely small and load capacity is reduced
Solution Approach 1:
The drive shaft is divided into a main shaft portion and an eccentric portion that are coupled together. The main shaft portion maintains its full diameter to support an adequately sized main bearing, while the eccentric portion is separately formed with the required geometry for piston assembly. This segmentation eliminates the need to compromise the main bearing size.
Solution Approach 2:
The coupling portion acts as an intermediary element that connects the main shaft portion and the eccentric portion. It allows the piston to be assembled to the eccentric portion while the main shaft portion remains intact to support the main bearing, thus mediating between the requirements for piston assembly and bearing load capacity.
Data Source
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AI summary
A rotary compressor (1) includes a lower coupling portion (90) between a lower eccentric portion (76) and an auxiliary shaft portion (74) in a drive shaft (70). The lower coupling portion (90) is configured so that the distance obtained by subtracting its eccentricity eL from its radius ReL is less than the radius RS of the auxiliary shaft portion (74), its outer surface is not extended out of the outer surface of the lower eccentric portion (76), and its height HCL is lower than the height HPL of the lower piston (45). A circumferentially extending inner peripheral groove (48) is formed at an end of the inner peripheral surface of the lower piston (45) on the lower coupling portion (90) side to avoid contact between the inner peripheral surface of the lower piston (45) and the auxiliary shaft portion (74) when the lower piston (45) is on the outer peripheral side of the lower coupling portion (90) and has its inner peripheral surface outside the outer peripheral surface of the lower eccentric portion (76) in the radial direction of the drive shaft (70).