Hermetic Compressor Piston with Segmented Axial Bands
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Solution Overview
Problem
Hermetically sealed compressor pistons face challenges in reducing friction between the piston and cylinder, leading to energy inefficiency and lubricating oil seepage, while existing solutions like grinding cause burrs that require additional machining and do not fully address these issues.
Innovation Solution
A piston design featuring axial bands that extend from the sealing strip, with the connecting pin hole included within one of these bands to minimize clearance and friction, reducing the need for further machining and preventing lubricant seepage, utilizing a configuration that includes additional bands for improved guiding and sealing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the clearance between the piston surface and cylinder wall is minimized to improve sealing and guiding performance, then hermetic sealing and guiding are improved, but friction increases leading to reduced energy efficiency
Solution Approach 1:
The piston surface is segmented into multiple functional zones: sealing bands with minimal clearance for hermetic sealing and guiding, and lowered friction areas with increased clearance to reduce friction. This segmentation allows different regions to optimize for their specific functions without compromising the other.
Solution Approach 2:
Different regions of the piston surface are given different geometric properties: the sealing bands maintain minimal clearance for effective sealing and guiding, while the friction areas are lowered to create larger clearance zones. This local differentiation of surface quality enables simultaneous optimization of sealing performance and friction reduction.
2Loss of energy
If grinding machining is applied to create lowered friction areas, then friction is reduced, but burrs are generated on the connecting pin hole edges requiring additional deburring operations
Solution Approach 1:
The harmful byproduct (burr) is extracted or removed from the critical area (connecting pin hole edge) through the design of the lowering operation that stops before the hole edge, preventing burr formation at the most critical location while still achieving friction reduction in the necessary areas.
Solution Approach 2:
The lowering operation is performed in a controlled manner that anticipates and prevents burr formation at the connecting pin hole edges, eliminating the need for subsequent deburring operations. The machining parameters and tool paths are designed to stop precisely before reaching the hole edges.
3Loss of energy
If lowered areas are created adjacent to the connecting pin hole to reduce friction, then energy efficiency improves, but lubricating oil accumulates in the hole and seeps into the compression chamber
Solution Approach 1:
The bands arranged orthogonal to the pin hole axis act as intermediary sealing elements that prevent direct communication between the oil accumulation zone in the connecting pin hole and the compression chamber. These bands block the seepage path while allowing the friction-reducing lowered areas to exist.
Solution Approach 2:
The harmful effect of oil seepage is prevented by strategically positioning the bands to block the seepage path, effectively extracting or removing the harmful communication path between the oil reservoir and compression chamber.
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
This design enhances energy efficiency by reducing friction and lubricant seepage, minimizing vibrations, and eliminating the need for additional machining steps, thereby improving compressor performance and reducing production costs.
Implementation Method 1
there must be a minimal clearance between the surfaces of the piston and the cylinder, with the surfaces almost in mutual contact with each other
Implementation Method 2
the areas included between the two bands or sectors are lowered, by grinding, both with respect to the sealing head and to the lateral bands, so as to limit the friction with the walls of the cylinder
Data Source
Figure 1~2
AI summary
The present invention refers to a piston for hermetically sealed compressors comprising a circumferential sealing strip (2), a first band (4) and a second band (5) that extend axially from the strip (2), a through hole (3) suitable to receive a connecting pin for a connecting rod. The first band (4) and the second band (5) are configured in the shape of circular sectors having substantially the same diameter as the strip (2) to carry out a sealing function by cooperating with the strip (2) and a guiding function to guide the sliding movement of said piston (1) inside a cylinder. The first band (4) and the second band (5) are arranged opposite one another relative to an axis essentially perpendicular with respect to the axis of the through hole (3). The piston (1) also comprises at least a third band (6) that extends axially from the strip (2) and is configured in the shape of a circular sector having substantially the same diameter as the strip (2). The third band (6) is arranged at a first end of the hole (3) so that the lateral edges (7, 8) of the third band (6) are arranged adjacent to the edges of the hole (3).