Low-Pressure Screw Compressor Bearing Arrangement

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Solution Overview

Problem

High-pressure screw compressors are expensive and time-consuming to mount due to multiple bearings, and standard bearing arrangements are overdesigned for low-pressure applications, limiting rotational speed and efficiency.

Innovation Solution

A low-pressure screw compressor design featuring rotor bodies with a single deep groove ball bearing on the inlet side and a fixed cylindrical roller bearing on the outlet side, utilizing springs to minimize tip clearance and absorb axial forces, allowing for compact and efficient operation at higher rotational speeds.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple bearings (single-row cylindrical roller bearing + four-point contact ball bearing + thrust bearing) are used to support rotor bodies, then the compressor can handle high-pressure applications and absorb axial forces, but the manufacturing cost and mounting time increase significantly

Engineering Contradiction:

Improvebearing capacity for axial forcesVSAvoidnumber of bearings and alignment requirements

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines multiple bearing functions into a single cylindrical roller bearing with guide flanges. The bearing simultaneously provides radial support, axial positioning, and absorption of axial forces through the guide flanges that engage with the housing. This merging eliminates the need for separate thrust bearings and simplifies the bearing arrangement while maintaining the ability to handle axial forces.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The cylindrical roller bearing is designed with guide flanges that give it multi-functional capabilities. It not only supports radial loads but also guides axial movement and absorbs axial forces through the engagement of guide flanges with the housing. This universal bearing design replaces multiple specialized bearings with a single component that performs multiple functions.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If standard two-row angular contact ball bearings are used in Roots blowers, then the bearing arrangement can support the rotor bodies, but the rotational speed is limited to 3000-5000 rpm due to technical restrictions

Engineering Contradiction:

Improvebearing support capabilityVSAvoidrotational speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The patent changes the bearing type from standard two-row angular contact ball bearings to cylindrical roller bearings with guide flanges. This parameter change in bearing design allows for higher rotational speeds (6000 rpm or more) while maintaining the ability to support rotor bodies and absorb axial forces, overcoming the speed limitations of conventional bearing arrangements.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If conventional bearing arrangements are used in low-pressure screw compressors, then the compressor can operate at lower speeds, but the design is overdesigned and not optimized for high-speed operation

Engineering Contradiction:

Improvebearing support and axial force absorptionVSAvoidrotational speed capability

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent modifies the bearing arrangement parameters by using cylindrical roller bearings with guide flanges instead of conventional bearings. This optimization allows the low-pressure screw compressor to operate at higher rotational speeds (6000 rpm or more) while maintaining adequate support and axial force absorption, eliminating the overdesign present in conventional arrangements.

Inventive Principle:

Principle #35Parameter changes

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 reduces manufacturing and maintenance costs, extends bearing life, and enhances operational stability and efficiency by minimizing losses and axial forces, making it suitable for higher rotational speeds than conventional Roots blowers.

Implementation Method 1

means which push one or both rotor bodies to the outlet side of the rotor housing, which means are made in the shape of at least one spring which extends between the rotor housing and the rotor body

Methodology Applied

Scientific EffectSpring force: Spring

Implementation Method 2

each of the above-mentioned rotor bodies is bearing mounted, on the inlet side of the rotor housing by means of a single loose deep groove ball bearing and, on the outlet side of the rotor housing, by means of a fixed cylindrical roller bearing

Methodology Applied

Scientific EffectBall bearing: Ball Bearing

Implementation Method 3

Methodology Applied

Scientific EffectRoller bearing: Roller

Data Source

PatentEP1917443B1Improved low-pressure screw compressor

Publication Date: 2011.03.09 ATLAS COPCO AIRPOWER NV

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AI summary

Improved low-pressure screw compressor provided with a rotor housing (2) with an inlet side and an outlet side, whereby in this rotor housing (2) are provided two rotor bodies (3 and 4) which each consist of a shaft (5, 7 respectively) and a screw (6, 8 respectively) which is provided round the above-mentioned shaft (5 or 7), whereby the rotor bodies (3 and 4) are bearing-mounted in said rotor housing (2) with their shafts (5 or 7), and whereby each of the rotor bodies (3 and 4) is bearing-mounted on the inlet side of the rotor housing (2) with a single loose bearing and on the outlet side of the rotor housing by means of a single fixed cylindrical roller bearing (15).