Turbo-Molecular Vacuum Pump Radial Strut Hinge Design
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Solution Overview
Problem
In turbo-molecular vacuum pumps with an integral bearing spider, the clamping force applied to the inlet flange causes significant displacement of the bearing spider, leading to inaccurate rotor placement and potential pump failure due to the transmission of torsional moments, especially when using passive magnetic bearings.
Innovation Solution
The integration of a pinched or notched hinge portion in the radial struts allows for decoupling of the bearing support from the inlet flange's clamping force, reducing axial movement and maintaining structural strength through strategically reduced thickness at the pinched point, which flexes to absorb torsional moments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the bearing spider is made as an integral part of the pump body, then the number of component parts is reduced and assembly is simplified, but the clamping force applied to the inlet flange causes significant displacement of the bearing spider
Solution Approach 1:
The bearing spider is segmented from the pump body through the introduction of a hinge portion in the radial struts. This hinge portion acts as a separation point that allows the bearing spider to be functionally divided from the inlet flange structure, enabling independent movement and reducing the transmission of clamping forces while maintaining the integral construction benefits.
Solution Approach 2:
The structural parameters of the radial struts are changed by introducing a hinge portion with reduced thickness or cross-sectional area. This parameter change creates a flexible region that can deform under clamping loads, thereby absorbing the displacement that would otherwise be transmitted to the bearing spider, while maintaining overall structural integrity.
2Strength
If the radial struts are made with uniform thickness for structural strength, then the struts can support clamping forces, but the clamping force is transmitted to the bearing spider causing displacement
Solution Approach 1:
The radial struts are designed with non-uniform thickness, featuring a hinge portion with locally reduced cross-sectional area. This local quality change creates a specific region of flexibility within the strut that can deform to absorb clamping forces, while the remaining portions of the strut maintain sufficient thickness to provide the necessary structural strength for supporting the bearing spider.
Solution Approach 2:
The strut is functionally segmented into a rigid portion (with full thickness for strength) and a flexible hinge portion (with reduced thickness). This segmentation allows the strut to simultaneously provide structural support and absorb displacement, resolving the contradiction between strength and positioning accuracy.
3Strength
If the inlet flange is rigidly connected to the bearing spider, then the structure is simple and strong, but torsional moments from clamping forces cause bearing misalignment
Solution Approach 1:
The connection between the inlet flange and bearing spider is changed from a rigid static connection to a dynamic connection through the hinge portion. The hinge allows the structure to adapt dynamically to applied clamping forces by deforming in a controlled manner, thereby protecting the bearing alignment while maintaining structural integrity through the flexible-rigid-composite design.
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 significantly reduces the displacement of the bearing spider by up to 20µm under clamping forces, maintaining accurate rotor positioning and preventing pump failure by decoupling the bearing support from the inlet flange's distortions.
Implementation Method 1
the radial struts comprise a hinge portion that can flex to allow relative movement of the inlet flange with respect to the supporting mount
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention relates to a turbo-molecular vacuum pump comprising bearings (26) for supporting the drive shaft and/or the rotor in relation to a pump body (10), wherein a first bearing is coupled to the rotor and disposed on supporting mount at the high vacuum side of the rotor and radial struts (22) extend from the supporting mount and form an integral part of the body (10); the radial struts (22) comprise a hinge portion (40) that can flex to allow relative movement of the inlet flange (14) with respect to the supporting mount to reduce distortion effects.