Compressor Shaft and Bearing Geometry for Low-Speed Lubrication
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Solution Overview
Problem
Refrigerant compressors face efficiency deterioration due to high frictional resistance and severe lubrication conditions, exacerbated by reduced viscosity of lubricating oil and shortened sliding portions, leading to increased input and decreased performance, especially during low-speed inverter drive operations.
Innovation Solution
A refrigerant compressor design featuring a shaft with a film hardness matching or exceeding the bearing's sliding surface hardness, and a curved-surface portion on either the shaft or bearing to reduce local contact and maintain an adequate oil film thickness, along with a low-rigidity portion on the bearing to alleviate load-induced deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the viscosity of lubricating oil is lowered and the dimensions of sliding portions are shortened to improve efficiency, then energy consumption is reduced, but the lubrication conditions become severe and the film quickly abrades leading to increased input
Solution Approach 1:
The patent applies surface treatment to the shaft part to form a film with controlled hardness (equal to or greater than the bearing's sliding surface hardness). This parameter change in surface hardness prevents film abrasion while maintaining low-viscosity lubricating oil, thus resolving the contradiction between energy efficiency and film durability
Solution Approach 2:
The patent uses a composite structure consisting of the base shaft material combined with a surface film (such as oxide film, nitride film, or coating film). This composite approach allows the bulk material to maintain good lubrication properties while the surface film provides enhanced hardness and wear resistance, addressing both energy consumption and reliability requirements
2Use of energy by moving object
If inverter drive is used to reduce speed and improve efficiency, then energy consumption is reduced, but the oil film becomes thin and contact between sliding portions by minute projections occurs frequently leading to high input
Solution Approach 1:
The patent modifies the surface hardness parameter of the shaft part through surface treatment, creating a film that is harder than or equal to the bearing's sliding surface. This prevents the minute projections from causing excessive friction and wear even when the oil film is thin during low-speed inverter operation, thus maintaining low energy consumption
Solution Approach 2:
The patent introduces a curved-surface portion (crowning) on either the shaft or bearing with a specific radius of curvature. This curvature distributes the contact pressure more evenly across the sliding surface, preventing localized contact by minute projections and maintaining adequate oil film thickness during low-speed operation, thereby reducing frictional resistance and energy consumption
3Reliability
If a hard soft-nitriding-treated film is provided on the sliding portion to reduce abrasion, then the progress of abrasion of projections slows down, but the high input state continues for a long period of time due to film coating projections
Solution Approach 1:
The patent carefully controls the hardness parameter of the surface film to be equal to or greater than the bearing's sliding surface hardness, but not excessively hard. This balanced hardness level prevents film abrasion while avoiding the coating of minute projections that would cause prolonged high input, thus resolving the contradiction between abrasion resistance and energy consumption
Solution Approach 2:
The patent applies surface treatment specifically to the sliding surface of the shaft part where the film contacts the bearing, creating a localized hard film only where needed. This local quality enhancement provides abrasion resistance at the contact interface without affecting the overall shaft properties, preventing both film wear and projection coating issues
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 design prevents efficiency deterioration by reducing frictional resistance and maintaining an adequate oil film, resulting in lower input and improved durability, even during low-speed operations.
Implementation Method 1
A film having hardness equal to or more than hardness of a sliding surface of the bearing part is provided on a sliding surface of the shaft part
Implementation Method 2
The sliding surface of the bearing part includes a curved-surface portion having an inner diameter that continuously increases in a curved shape toward an end of the bearing part in a center axis direction of the bearing part
Data Source
AI summary
The present invention includes: an electric component; a compression component driven by the electric component; and a sealed container accommodating the electric component and the compression component. The compression component includes: a shaft part rotated by the electric component; and a bearing part slidingly contacting the shaft part. A film having hardness equal to or more than hardness of a sliding surface of the bearing part is provided on a sliding surface of the shaft part. The sliding surface of the bearing part includes a curved-surface portion having an inner diameter that continuously increases, or the sliding surface of the shaft part includes a curved-surface portion having an outer diameter that continuously decreases.