Partial Annular Groove for Rotary Vacuum Pump Sealing
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Solution Overview
Problem
Rotary vacuum pumps in brake boosters experience increased wear and reduced performance due to air leaks and pressure imbalances caused by annular grooves extending over 360°, which disrupt the hydrodynamic bearing and lead to higher oil absorption and power consumption.
Innovation Solution
A partial annular groove with an angular extension of less than 360° and interruptions to maintain a hydrodynamic fluid bearing in the discharge region, allowing for improved contact area between the rotor and guide while preventing air leaks, with optimal extensions ranging from 150° to 300°, preferably 180° to 220°.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an annular groove extending over 360° is provided between the rotor guide and rotor, then sealing is improved by providing an oil barrier, but the hydrodynamic bearing is broken and wear increases
Solution Approach 1:
The annular groove is segmented into partial annular grooves that extend over less than 360° of the circumference. This segmentation maintains the sealing function while preserving the hydrodynamic bearing in the interruption regions, thereby reducing wear on the rotor and guide surfaces.
Solution Approach 2:
Different regions of the groove have different properties: the groove portions provide sealing barriers, while the interruption regions maintain hydrodynamic bearing characteristics. This local differentiation allows simultaneous achievement of sealing and reduced wear.
2Object-affected harmful factors
If an annular groove extending over 360° is provided, then air leak is reduced, but the contact area between rotor and guide is reduced and wear increases
Solution Approach 1:
The continuous 360° groove is divided into segmented partial grooves with interruptions. This segmentation preserves sufficient contact area between the rotor and guide while still providing effective sealing barriers in the groove regions to prevent air leaks.
Solution Approach 2:
Instead of providing a complete 360° groove, partial grooves extending over less than 360° are used. This partial action is sufficient to achieve the sealing objective while maintaining adequate contact area for the hydrodynamic bearing.
3Productivity
If an annular groove is provided to prevent air entry, then pump performance is maintained, but power absorption increases due to broken hydrodynamic bearing
Solution Approach 1:
The groove is segmented to preserve hydrodynamic bearing regions, which maintain efficient lubrication and reduce friction. This segmentation allows the pump to maintain performance while avoiding the excessive power absorption that would result from a complete groove breaking the hydrodynamic bearing.
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 solution reduces wear and maintains pump performance and oil flow stability throughout its operational life by maintaining the hydrodynamic bearing and minimizing air leaks, resulting in reduced power absorption and improved sealing.
Implementation Method 1
arranged to enable creating a hydrodynamic fluid bearing in a region opposite a discharge region of the pump
Implementation Method 2
Air from outside the pump (typically at atmospheric pressure) can leak towards the inside of the pump (under negative pressure) through the clearance between the rotor and the guide
Data Source
AI summary
A rotary vacuum pump, for instance a vane pump, has at least one circumferential groove (6) between facing side surfaces of the rotor (2) and of the rotor guide (3) for receiving a lubricating and sealing fluid. The circumferential groove (6) is a partial annular groove, which has an angular extension of less than 360° and has at least one interruption enabling creating a hydrodynamic fluid bearing in a region opposite a discharge region of the pump (1; 101; 121; 201), over the whole axial extension of the facing surfaces. A method of lubricating a rotary vacuum pump is also provided.