Oldham Ring Key Cap Coupling Stress Relief
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Solution Overview
Problem
The durability and stability of Oldham's rings in scroll compressors are compromised due to material mismatch and residual stress issues during the coupling of keys and caps, leading to frictional resistance, plastic deformation, and burr formation, which affects the compressor's efficiency and reliability.
Innovation Solution
The design incorporates contact avoidance structures on the keys and caps with chamfered edges and curved surfaces to prevent collision and residual stress, ensuring secure coupling with reduced thickness and weight, thereby enhancing durability and minimizing frictional resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the cap is pressed into the key in an interference fitting manner to secure coupling, then the coupling force is strengthened, but residual stress and frictional resistance cause the key to break over time
Solution Approach 1:
The patent introduces a relief curved portion in the coupling hole that extends to reduce residual stress before it can cause failure. This preemptive stress relief structure prevents the key from breaking due to accumulated residual stress during operation, thereby maintaining both coupling strength and long-term reliability.
Solution Approach 2:
The patent modifies the geometric parameters of the coupling interface by creating a relief curved portion that changes the stress distribution pattern. This parameter change transforms the stress concentration at the interference fit interface into a more favorable stress distribution, reducing peak stresses while maintaining adequate coupling force.
2Stability of the object's composition
If the key and cap are formed in polygon shapes to prevent free rotation, then rotational stability is improved, but tolerance accumulation at vertices causes mismatch and breaking during insertion
Solution Approach 1:
The patent replaces the sharp vertex geometry with a curved relief portion in the coupling hole. This curvature accommodates manufacturing tolerances by providing a gradual transition zone that guides the key into proper alignment, preventing mismatch and breaking while maintaining rotational stability through the polygonal overall shape.
Solution Approach 2:
The relief curved portion acts as a preliminary guiding feature that prepares the coupling interface for proper alignment before the key is fully inserted. This preliminary action ensures that even with vertex tolerance variations, the key and cap will align correctly during the insertion process.
3Manufacturing precision
If the cap is pushed to fully couple with the key, then coupling completeness is achieved, but burrs are generated at the cap end due to strong contact with the thrust face
Solution Approach 1:
The patent extracts or removes the harmful burr formation mechanism by creating a relief curved portion that prevents the cap end from making strong contact with the thrust face during coupling. This extraction of the problematic contact zone eliminates burr generation while still achieving complete coupling through the relief structure.
Solution Approach 2:
The patent converts the potentially harmful strong contact that generates burrs into a beneficial stress-relief mechanism. The relief curved portion transforms the contact into a controlled deformation zone that relieves stress without generating harmful burrs, turning a harmful effect into a beneficial one.
4Strength
If the Oldham's ring is made with thicker thrust face to strengthen grounding force, then grounding stability is improved, but burr generation increases due to stronger contact with the cap
Solution Approach 1:
The patent applies local quality by creating a specific relief curved portion only at the coupling hole where stress concentration occurs, while maintaining the overall thick thrust face design for grounding stability. This localized modification addresses burr generation at the coupling interface without compromising the grounding force provided by the thick thrust face.
Data Source
AI summary
A compressor includes a rotation shaft, a drive unit, and a compression unit. The compression unit includes a fixed scroll, an orbiting scroll, a main frame that is disposed on the fixed scroll, and an Oldham's ring coupled to the orbiting scroll and the main frame and configured to restrict rotation of the orbiting scroll. The Oldham's ring includes a ring body disposed between the orbiting scroll and the main frame, keys that protrude from the ring body that are each coupled to the orbiting scroll or the main frame, and caps that are inserted into the main frame and that each have (i) a coupling hole that receives a key among the keys and (ii) a machined portion that faces the coupling hole and that is spaced apart from at least a portion of an outer surface of the key.