Compressor Crankshaft Undulated Undercut Friction Reduction
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Solution Overview
Problem
Hermetic compressors experience mechanical losses due to friction between movable components, particularly in the bearing area, which are not adequately reduced by existing lubrication techniques.
Innovation Solution
The crankshaft features an undulated undercut that adjusts based on the changing forces during rotation, separating the bearing surface into regions that support varying loads, with deeper undercuts in areas that consistently bear more load and shallower undercuts in areas that bear less load, thereby reducing frictional losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a cylindrical cut-out is made on the crankshaft to reduce contact surface with the bearing, then friction is reduced, but the bearing cannot adequately counterbalance the greatest force (oil pressure) acting thereon
Solution Approach 1:
The patent applies local quality by creating an undulated undercut with varying depths at different angular positions on the crankshaft. The undercut depth is locally optimized: deeper in regions where the bearing portion supports less load (reducing friction) and shallower in regions where the bearing portion supports greater load (maintaining load-bearing capacity). This spatially varying structure resolves the contradiction between reducing friction and maintaining strength.
2Loss of energy
If the crankshaft surface is reduced to decrease friction, then mechanical losses are reduced, but the bearing portions cannot adequately support the loads during crankshaft rotation
Solution Approach 1:
The patent applies dynamics by creating an undulated undercut that adapts to the dynamically changing load conditions during crankshaft rotation. The varying undercut depth corresponds to the cyclic variation in bearing load, providing optimal friction reduction when load is low and adequate load support when load is high. This dynamic adaptation resolves the contradiction between reducing mechanical losses and maintaining 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
This design reduces frictional losses and enhances energy efficiency by optimizing the crankshaft surface contact, leading to improved compressor performance and reduced mechanical losses, especially during initial start-up.
Implementation Method 1
Friction is present in the bearing resulting from hydrodynamic and/or boundary oiling even though the bearing is lubricated for easy movement of the crankshaft in the bearing
Implementation Method 2
Friction is present in the bearing resulting from hydrodynamic and/or boundary oiling even though the bearing is lubricated for easy movement of the crankshaft in the bearing
Data Source
Figure 1
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Figure 5~6
AI summary
The present invention relates to a compressor (1) that comprises a casing (2), an electric motor having a rotor (3) and a stator (4), and a cylinder block (6) enabling the crankshaft (5) to be beared radially by means of a bearing (7) and wherein the frictional forces generated in the bearing (7) during the rotation of the crankshaft (5) is decreased.