Vacuum Pump Bolt Structure to Prevent Peripheral Part Deformation
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Solution Overview
Problem
The increasing weight of rotating bodies in vacuum pumps due to larger sizes and high-temperature materials leads to higher destructive torque, causing deformation of peripheral parts due to increased axial force from bolts, which can be exacerbated by gaps between the casing and peripheral parts, and using high-strength bolts or increasing the pitch circle diameter is undesirable.
Innovation Solution
A vacuum pump design that includes axial force reducing means, such as spacers or longer bolts, to prevent deformation of peripheral parts by forming gaps between bolt heads and fastening faces, reducing the axial force applied to the outer cylinder and peripheral parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the count of bolts is increased to absorb destructive torque, then the reliability is improved, but the peripheral parts may be deformed due to increased axial force
Solution Approach 1:
A washer is introduced as an intermediary element between the bolt head and the peripheral part. The washer distributes the axial force over a larger area, preventing stress concentration and deformation of the peripheral part while maintaining the bolt's ability to absorb destructive torque.
Solution Approach 2:
The axial force is redistributed by changing the contact parameters between the bolt and the peripheral part. By introducing the washer, the force distribution area is increased, effectively changing the stress parameters acting on the peripheral part to prevent deformation.
2Reliability
If the pitch circle diameter of bolts is increased to absorb destructive torque, then the reliability is improved, but the size of the vacuum pump increases
Solution Approach 1:
The washer acts as a mediator that allows the bolts to be positioned closer together by distributing forces more effectively. This enables maintaining the same torque absorption capability with a smaller pitch circle diameter, thus preventing increase in pump size.
3Reliability
If high-strength bolts are used to absorb destructive torque, then the reliability is improved, but the versatility is poor and costs increase
Solution Approach 1:
The washer serves as a universal intermediary that works with standard bolts to provide the necessary force distribution. This allows the use of versatile, standard bolts instead of specialized high-strength bolts, maintaining versatility while achieving the required reliability through the washer's force distribution capability.
Data Source
AI summary
Provided is a vacuum pump in which deformation of a peripheral part fastened to an outer cylinder can be prevented even when a count of bolts increases. A vacuum pump according to the present disclosure includes a rotating body, an outer cylinder that accommodates the rotating body, a peripheral part that is disposed on an outer perimeter side of the rotating body and concentrically with the outer cylinder, a plurality of bolts that fasten the outer cylinder and the peripheral part, and an axial force reducing means for reducing bolt axial force acting on the outer cylinder. The axial force reducing means is provided to at least one of the plurality of bolts.