Vacuum Pump Rotor Disc Thermal Expansion Compensation

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Solution Overview

Problem

Existing turbomolecular vacuum pumps face issues with tension introduction due to mechanical joining methods and thermal expansion differences, leading to potential unbalance and vibration during operation.

Innovation Solution

The rotor disc design incorporates a substantially cylindrical inner ring with radially extending blade elements and expansion joints or slots to compensate for thermal expansions, reducing tangential tensions, and uses segmented inner rings connected by elastomer elements and fiber-reinforced retaining rings for improved stability and vibration damping.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If mechanical joining methods are used to assemble rotor discs, then the rotor can be constructed from multiple discs, but tensions are introduced into the inner ring and hub

Engineering Contradiction:

Improve rotor construction flexibilityVSAvoidtension in inner ring

Core Design Contradiction:

Adaptability or versatilityVSStress or pressure

Solution Approach 1:

The inner ring is divided into multiple segments that can move independently relative to each other. This segmentation allows the inner ring to expand and contract radially without generating tangential tensions, while still providing structural support for multiple rotor discs. The segments are connected through the hub region, maintaining overall structural integrity while allowing localized thermal expansion and contraction.

Inventive Principle:

Principle #1Segmentation

2Strength

If reinforcement rings are used to connect rotor discs, then the rotor structure is strengthened, but different thermal expansions occur between the rotor disc and reinforcement ring

Engineering Contradiction:

Improverotor structure strengthVSAvoidthermal expansion tension

Core Design Contradiction:

StrengthVSStress or pressure

Solution Approach 1:

The material composition of the inner ring segments is optimized to match the thermal expansion characteristics of the rotor discs. By selecting materials with compatible coefficients of thermal expansion, the patent eliminates differential thermal expansion between the inner ring and rotor discs, preventing the generation of thermal stresses during operation while maintaining structural strength.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If the inner ring is made as a single piece, then manufacturing is simpler, but thermal expansions cannot be compensated

Engineering Contradiction:

Improveinner ring manufacturing simplicityVSAvoidthermal expansion compensation

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The inner ring is segmented into multiple independent sections that can expand and contract radially without constraining each other. This segmentation enables effective thermal expansion compensation while maintaining manufacturing feasibility through modular construction. Each segment can be manufactured separately and assembled, or formed as a continuous structure with controlled segmentation points.

Inventive Principle:

Principle #1Segmentation

4Ease of manufacture

If rotor discs are assembled from individual pieces, then manufacturing cost is reduced, but tensions occur due to centrifugal forces

Engineering Contradiction:

Improvemanufacturing costVSAvoidcentrifugal tension

Core Design Contradiction:

Ease of manufactureVSStress or pressure

Solution Approach 1:

The inner ring segments are designed to move dynamically relative to each other in response to centrifugal forces during rotation. This dynamic capability allows the segments to adjust their positions and distribute centrifugal loads more evenly throughout the structure, reducing peak tensions in the inner ring and hub regions while maintaining the advantages of modular construction.

Inventive Principle:

Principle #15Dynamics

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 allows for higher rotational speeds and reduced unbalance, effectively minimizing tension and vibration issues, enabling more stable and balanced operation of the rotor.

Implementation Method 1

the inner ring has at least one expansion joint or a slot. Providing such an expansion joint is advantageous in that thermal expansions can be compensated thereby

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

individual inner ring segments may be connected with each other by connecting elements. For example, connecting elements made of an elastomer may be provided in the slots or the expansion joints

Methodology Applied

Scientific EffectVibration damping: Damping

Implementation Method 3

Further, providing a plurality of a plurality of expansion joints regularly distributed over the circumference is advantageous in that the tensions are compensated better and the deformation of individual segments is respectively less than the deformation of a whole ring segment having only one slot

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Data Source

PatentUS9932987B2Rotor disc and rotor for a vacuum pump

Publication Date: 2018.04.03 LEYBOLD AG

AI summary

A rotor disc for a vacuum pump, in particular a turbo molecular pump, having an inner ring. The inner ring is connected to a plurality of blade elements extending radially outward. The inner ring has at least one expansion joint. For assembly, the inner ring can be surrounded by a retaining ring and arranged on a hollow cylindrical carrier element as applicable.