Vacuum Pump Labyrinth Seal and Purge Gas for Oil Vapor Control
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Solution Overview
Problem
Existing vacuum pump designs with lubricated ball bearings face issues with oil vapor leakage and lubricant depletion due to pressure changes, leading to reduced lubricant life, especially in configurations with labyrinth seals and grease lubrication.
Innovation Solution
The implementation of a vacuum pump with a labyrinth seal between the motor stator and ball bearing spaces, combined with a purge gas flow passage and an oil reservoir, minimizes gas flow between these areas, reducing oil vapor evaporation and extending lubricant life by maintaining a sealed environment and using purge gas to prevent oil vapor leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a labyrinth seal is provided between the motor and bearing spaces to prevent oil vapor reverse flow, then oil vapor leakage is reduced, but gas flow between spaces increases during pressure changes, causing oil vapor to escape and lubricant life to deteriorate
Solution Approach 1:
A purge gas (nitrogen or inert gas) is introduced as an intermediary substance into the motor space to create a protective atmosphere. This mediator prevents oil vapor from escaping during pressure changes by maintaining positive pressure and blocking the reverse flow path, thereby protecting the lubricant in the bearing space while allowing the labyrinth seal to function effectively.
2Reliability
If the bearing space is completely sealed to prevent oil vapor escape, then lubricant life is extended, but pressure changes cause gas to flow in/out via the labyrinth seal, still carrying oil vapor
Solution Approach 1:
The harmful element (oil vapor) is extracted from the potential flow path by introducing purge gas into the motor space. The purge gas creates a pressure barrier that extracts oil vapor from the bearing space before it can escape through the labyrinth seal, effectively removing the harmful substance from the circulation path without requiring complete sealing.
3Object-generated harmful factors
If a lip seal plate is used to prevent oil leakage, then oil vapor containment is improved, but high-speed rotation requires oil film formation that is incompatible with grease lubrication
Solution Approach 1:
The vacuum pump is segmented into two distinct pressure zones: the motor space (at higher pressure with purge gas) and the bearing space (at lower pressure with grease lubrication). The labyrinth seal acts as the segmentation boundary, allowing each zone to maintain its optimal lubrication regime without interference, thus resolving the incompatibility between lip seal requirements and grease lubrication.
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 configuration effectively reduces oil vapor flow-out, thereby extending the lubricant life of the ball bearing by minimizing gas exchange between the motor and bearing spaces, even under pressure changes, and prevents oil vapor from escaping during gas purging.
Implementation Method 1
a first labyrinth seal provided between a space in which a motor stator of the motor is arranged and a space in which the lubricated ball bearing is arranged
Implementation Method 2
a purge gas flow passage for introducing a purge gas to the space in which the motor stator is arranged
Implementation Method 3
a lubricated ball bearing for supporting the rotor shaft
Data Source
AI summary
A vacuum pump which, among others, has a lubricated ball bearing for supporting a rotor shaft of a motor, a bearing holder for holding the lubricated ball bearing, a first labyrinth seal provided between a motor arrangement space and a bearing arrangement space, and a balance adjustment member installed at a position of the rotor shaft to face the bearing holder and used for balance adjustment of a rotating body. A second concave and convex part to be fitted to the first concave and convex part forming the first labyrinth seal. By reducing a gap of the bearing arrangement space, the space in which the oil vapor is filled is reduced. Therefore, a moving amount of the gas, and thus, the decrease in the base oil of the lubricant can be suppressed, thereby extending the lubricating life.