Compressor Hermetic Terminal Stress Distribution
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Solution Overview
Problem
Hermetic terminals in compressors experience fatigue failure due to localized bending caused by pressure fluctuations, leading to loss of the hermetic seal and compressor failure, as the existing designs concentrate stress at the weld joint.
Innovation Solution
The design features a cup-shaped housing with an annular flange welded to the inner surface of the compressor shell, providing increased compliance and distributing stress through reduced thickness walls and leg portions, along with a projection-style resistance weld that enhances bonding strength and stiffness, while minimizing material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If the terminal wall thickness is reduced to minimize material usage, then material consumption decreases, but the fatigue strength and reliability of the terminal decrease
Solution Approach 1:
The terminal structure employs varying wall thicknesses in different regions: thinner walls in non-critical areas to reduce material usage, and thicker walls at critical stress concentration zones (such as the aperture region and weld joints) to maintain fatigue strength and reliability. This localized quality differentiation resolves the contradiction between material minimization and structural durability.
2Stability of the object's composition
If the terminal is rigidly connected to the shell, then structural stability improves, but stress concentration at the weld joint increases leading to fatigue failure
Solution Approach 1:
The terminal incorporates flexible elements or compliant connections that allow controlled movement and deformation under pressure fluctuations. This dynamic capability enables the terminal to accommodate shell expansion and contraction without generating excessive stress concentrations at the weld joint, thereby maintaining both structural stability and fatigue resistance.
Solution Approach 2:
The terminal design includes stress-relief features such as fillet radii, gradual thickness transitions, or elastic elements positioned at critical locations before stress concentrations can develop. These preemptive cushioning elements distribute and mitigate stress peaks during pressure cycles, preventing fatigue failure while maintaining structural integrity.
3Ease of manufacture
If the projection is positioned close to the aperture, then manufacturing simplicity increases, but stress concentration at the weld joint increases
Solution Approach 1:
The projection's position and dimensions are optimized to provide adequate distance from the aperture, creating a local quality differentiation in the stress distribution pattern. This strategic positioning reduces stress concentration at the weld joint while maintaining manufacturing feasibility through standard fabrication processes.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A compressor including a shell having an aperture. A drive mechanism is disposed within the shell, and a compression mechanism is driven by the drive mechanism. A hermetic terminal assembly is provided in the aperture including a cup-shaped housing surrounded by an annular flange. The annular flange is secured to an inner surface of the shell a distance away from the aperture.