Oscillating Piston Compressor Geometry for Low Gap Volume
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Solution Overview
Problem
In reciprocating compressors, the offsetting of the cylinder's central axis with respect to the crankshaft's rotation center leads to increased gap volume and reduced volumetric efficiency due to potential interference between the piston and valve plate, especially at the top dead center, resulting in deteriorated performance.
Innovation Solution
A compressor design where the piston is an oscillating piston with a spherical outer surface, offsetting the cylinder's central axis relative to the crankshaft's rotation center, ensuring the piston's upper surface is parallel to the valve plate at top dead center, preventing interference and minimizing gap volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the cylinder is disposed to be offset by a certain offset amount with respect to the crankshaft rotation center, then the piston can reciprocate smoothly, but the oscillation angle at top dead center is not 0, causing gap volume increase and volumetric efficiency deterioration
Solution Approach 1:
The invention applies asymmetry by configuring the piston body with an inclined upper surface that is not parallel to the valve plate when the piston is at bottom dead center, but becomes parallel when the piston is at top dead center. This asymmetric configuration allows the piston to reciprocate smoothly while minimizing gap volume at the critical top dead center position, thereby resolving the contradiction between operational smoothness and volumetric efficiency.
2Volume of stationary object
If the upper surface of the piston and the crankcase side surface of the valve plate are made parallel at a crank angle where the connecting rod axis is parallel to the cylinder central axis, then the gap volume is reduced, but the piston and valve plate may interfere with each other during transition to top dead center
Solution Approach 1:
The invention applies preliminary action by pre-configuring the piston upper surface inclination angle such that when the piston reaches top dead center, the upper surface becomes parallel to the valve plate. This preliminary configuration prevents interference during the transition to top dead center while minimizing gap volume, as the geometric relationship is established in advance through the inclined surface design rather than requiring adjustment during operation.
3Adaptability or versatility
If the cylinder central axis is offset from the crankshaft rotation center, then the piston oscillation is enabled, but the gap volume increases and volumetric efficiency deteriorates
Solution Approach 1:
The invention applies local quality by making the upper surface of the piston body inclined relative to the piston central axis, creating a localized geometric feature that compensates for the overall offset between the cylinder central axis and crankshaft rotation center. This local inclination ensures that at top dead center, the piston upper surface becomes parallel to the valve plate, minimizing gap volume in the critical sealing region while maintaining the necessary oscillation capability throughout the compression cycle.
Data Source
AI summary
There is provided a compressor including: a piston that reciprocates inside a cylinder; a valve plate that closes an end portion of the cylinder; a connecting rod that supports the piston; a crankshaft that applies a rotating force to an end portion of the connecting rod; and a crankcase that rotatably supports the crankshaft. The piston is an oscillating piston that reciprocates while oscillating inside the cylinder according to rotation of the crankshaft. A central axis of an inner diameter of the cylinder is disposed at a position shifted by an offset amount e with respect to a rotation center axis of the crankshaft. An upper surface of the piston is substantially parallel to a crankcase side surface of the valve plate in a state where the piston is at a top dead center.