Compressor Connecting Rod Bushing Insert for Startup Lubrication
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Solution Overview
Problem
Reciprocating compressors often experience under-lubrication issues due to prolonged idle periods, leading to potential seizure of connecting rods and crankshaft, which can cause catastrophic damage.
Innovation Solution
Incorporating an insert with high lubricity, such as a polymeric material or unleaded bearing alloy, into the recess of the connecting rod's bushing to provide initial lubrication and prevent binding at startup, which can be aligned with the longitudinal axis and extend through the bushing's axial ends, ensuring sufficient lubrication at high-load areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lubricant is applied to moving components during assembly, then lubrication is provided for initial operation, but lubricant drips off and settles in the bottom of the compressor during prolonged idle periods, leading to under-lubrication at startup
Solution Approach 1:
The patent applies preliminary action by incorporating an insert with a lubricant reservoir into the connecting rod bushing before the compressor is put into service. This reservoir pre-stores lubricant at the critical interface between the connecting rod and crankshaft, ensuring that lubrication is immediately available at startup after prolonged idle periods, without relying on lubricant applied during assembly that would drip off over time.
2Reliability
If refrigerant migrates into the bottom of the compressor during prolonged idle periods, then refrigerant accumulates in the bottom, but this hinders lubricant flow through the crankshaft at initial startup
Solution Approach 1:
The insert acts as an intermediary mechanism that decouples the lubrication function from the crankshaft oil holes. By storing lubricant directly in the connecting rod bushing at the interface with the crankshaft, the system bypasses the need for lubricant to flow through the crankshaft, which is blocked by migrated refrigerant. The insert delivers lubricant directly to where it is needed, independent of crankshaft oil flow paths.
3Ease of manufacture
If standard bushing material is used in the connecting rod, then manufacturing is simplified, but the bushing is susceptible to under-lubrication and seizure during prolonged idle periods
Solution Approach 1:
The patent employs composite materials by combining a standard bushing material (such as aluminum) with an insert made of a different material that has superior lubrication properties or contains a lubricant reservoir. This composite structure maintains the manufacturing advantages of the standard bushing while adding the reliability benefits of enhanced lubrication through the insert, resolving the contradiction between ease of manufacture and bushing reliability.
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 high-lubricity insert ensures proper lubrication at startup and reduces wear on the connecting rods and crankshaft, extending their lifecycle and preventing initial startup damage, allowing normal lubricant flow to take over as the compressor operates.
Implementation Method 1
The second bushing may include an arched driving surface contacting the crankshaft and having a recess formed therein. The recess may receive an insert formed from a different material than the driving surface, such as a high-lubricity material
Data Source
AI summary
A compressor may include a shell, a crankshaft, a piston and a connecting rod. The shell may define a cylinder. The crankshaft is supported for rotation relative to the shell. The piston reciprocates within the cylinder in response to rotation of the crankshaft. The piston and the cylinder define a compression chamber therebetween. The connecting rod includes a first bushing rotatably coupled to the piston and a second bushing rotatably coupled to the crankshaft. The second bushing may include a driving surface contacting the crankshaft and having a recess formed therein. The recess receives an insert.