Thread Groove Pump Asymmetry to Suppress Gas Backflow
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Solution Overview
Problem
The co-flow thread groove pump mechanism experiences deteriorated exhaust and compression performance due to gas backflow and pressure differences between the outer and inner circumference sides, leading to inefficient gas transfer and compression.
Innovation Solution
The thread groove pump mechanism is improved by adjusting the ridge and root widths, seal lengths, and angles of the inner and outer circumference side thread groove portions to enhance sealability and compression ratios, reducing backflow and pressure differences, and optimizing the gas distribution between the two sides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a co-flow thread groove pump mechanism with parallel outer and inner circumference thread groove portions is used to improve exhaust performance, then the compression performance doubles, but gas backflow occurs in the inner circumference side due to smaller centrifugal force, deteriorating exhaust performance
Solution Approach 1:
The patent applies asymmetry by configuring the inner circumference side thread groove portion with a larger groove depth and/or wider groove width compared to the outer circumference side. This asymmetric design compensates for the smaller centrifugal force acting on gas in the inner circumference region, preventing gas backflow while maintaining the doubled compression performance benefit of the co-flow structure.
Solution Approach 2:
The patent implements local quality by making the thread groove dimensions (depth and/or width) location-dependent, specifically increasing the groove capacity in the inner circumference region where gas backflow occurs. This localized modification addresses the specific problem in the inner circumference area without changing the overall co-flow pump structure.
2Device complexity
If the inner circumference side thread groove portion is designed with standard dimensions, then the structure is simple, but pressure difference occurs between outer and inner circumference sides, reducing gas exhaust amount
Solution Approach 1:
The patent applies parameter changes by modifying the dimensional parameters of the inner circumference side thread groove portion, specifically increasing the groove depth and/or width. This parameter adjustment balances the pressure distribution between outer and inner circumference sides, eliminating pressure differences that would otherwise reduce gas exhaust amount.
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 enhances the exhaust and compression performance of the thread groove pump mechanism by suppressing gas backflow and reducing pressure differences, allowing for more efficient gas transfer and compression across the pump.
Implementation Method 1
A rotation radius of the gas in the inner-circumference-side thread groove portion 91 is smaller than a rotation radius of the gas in the outer-circumference-side thread groove portion 90. A centrifugal force acting on the gas in the inner-circumference-side thread groove portion 91 according to high-speed rotation of the cylinder portion 92 is smaller than a centrifugal force acting on the gas in the outer-circumference-side thread groove portion 90.
Implementation Method 2
According to a drag effect due to high-speed rotation of a cylinder portion 92 relative to a casing 93 and a stator 94, the gas in the outer-circumference-side thread groove portion 90 and the gas in the inner-circumference-side thread groove portion 91 are transferred from an intake side to an exhaust side in an up-down direction H while being respectively compressed.
Implementation Method 3
the gas in the outer-circumference-side thread groove portion 90 and the gas in the inner-circumcence-side thread groove portion 91 are transferred from an intake side to an exhaust side in an up-down direction H while being respectively compressed
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3(a)~3(c)
AI summary
The present invention provides a thread groove pump mechanism which suppresses a backflow of the gas in the thread groove pump mechanism and reduces the pressure difference in the pump radial direction near the outlet of the thread groove pump mechanism to thereby improve the exhaust performance and the compression performance. The present invention also provides a vacuum pump including the thread groove pump mechanism, and a rotor, an outer circumference side stator, and an inner circumference side stator used in the thread groove pump mechanism. A thread groove pump mechanism includes an exhaust-performance improving means in an outer-circumference-side thread groove portion engraved on an opposite surface of an outer circumference side stator opposed to a rotor cylinder portion and an inner-circumference-side thread groove portion engraved on an opposite surface of an inner circumference side stator opposed to the rotor cylinder portion.