Rotary Compressor Bush Crowning to Prevent Blade Edge Contact
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Solution Overview
Problem
In rotary compressors, the flat surface of the bush on the low-pressure side fails to maintain surface contact with the blade, leading to potential line contact between the bush edge and the cylinder chamber, which can cause wear and seizing due to pressure differences, reducing operational efficiency.
Innovation Solution
A crowned portion is introduced on the flat surface of the bush on the low-pressure side through a crowning process, starting from a position closer to the back pressure space than the swing center position, to prevent line contact with the blade and maintain a sufficient oil film, with the parameter α (L'/L) ranging from 0.2 to 0.5 to ensure reliable bush-blade interaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bush is designed with a flat surface to maintain surface contact with the blade, then the sliding properties are improved, but the pressure difference causes the bush to rotate and the edge to come in line contact with the blade, leading to wear and seizing
Solution Approach 1:
The invention applies curvature to the flat surface of the bush by introducing a crowned portion with a predetermined radius of curvature. This curved surface prevents line contact between the bush edge and the blade by distributing the contact area, thereby maintaining the oil film and preventing wear and seizing while preserving sliding properties.
Solution Approach 2:
The invention applies local quality by creating a crowned portion only at the specific location on the bush surface where line contact occurs. This localized modification changes the contact characteristics only where needed, maintaining surface contact in other areas while preventing edge contact with the blade.
2Stability of the object's composition
If the bush rotates due to pressure difference, then the edge of the bush comes closer to the cylinder chamber, but this causes the oil film to become small and leads to line contact with the blade
Solution Approach 1:
The crowned portion with curved surface prevents the bush from rotating into a harmful posture by providing a stable contact geometry. The curvature ensures that the bush maintains proper alignment with the blade, preventing the edge from coming too close and maintaining the oil film thickness.
3Reliability
If a crowned portion is added to the bush to prevent line contact, then wear and seizing are reduced, but the device complexity increases
Solution Approach 1:
The crowned portion is applied only to a specific local area of the bush surface rather than modifying the entire structure. This localized approach adds minimal complexity to the bush design while effectively preventing line contact and wear at the critical contact point.
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
The crowned portion effectively prevents edge contact between the bush and the blade, reducing wear and seizing, and ensures a consistent oil film, thereby enhancing the operational reliability and efficiency of the compressor.
Implementation Method 1
the bush rotates in a circumferential direction such that the edge of the bush closer to the back pressure space comes away from the blade, due to the pressure difference between the low pressure in the cylinder chamber and the high pressure in a back pressure space opposed to the cylinder chamber with respect to the bush
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A bush (61) on a low-pressure side has a flat surface (61a) provided with a crowned portion (65). The crowned portion (65) is a portion obtained through a crowning process starting from a position which is closer to a back pressure space (64) than a swing center position (O) is, and toward the edge of the bush (61) closer to the cylinder chamber (55). The swing center position (O) is a position where a gap between a blade (62) and the bush (61) is constant while a piston (60) rotates eccentrically.