Vacuum Pump Rotor Assembly Load Variation Relaxation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Vacuum pumps with metal and fiber-reinforced plastic (FRP) components face significant thermal stress issues due to differing thermal expansion coefficients, leading to rapid load variations and potential damage to anticorrosive coatings, especially in high-temperature environments and when subjected to centrifugal forces.
Innovation Solution
A rotor assembly with a load variation relaxation structure featuring a gradual taper or curved surface at the junction of the metal rotor and FRP cylindrical rotating portion, designed to reduce interference and distribute loads smoothly, preventing deformation and coating damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a metal rotor and FRP cylindrical rotating portion are joined by press fitting or bonding to enable high-speed rotation, then the discharge performance is improved, but large thermal stresses are generated at the joined section due to the difference in thermal expansion coefficients
Solution Approach 1:
The invention applies a gradual taper structure to the outer diametrical surface of the rotor, changing the geometric parameters from a uniform cylinder to a tapered form. This parameter change allows the contact surface area between the metal rotor and FRP cylindrical rotating portion to vary gradually along the axial direction, distributing the thermal stress more evenly and preventing concentration at specific points during thermal expansion.
Solution Approach 2:
The invention introduces a curved or tapered surface geometry instead of a flat cylindrical surface at the joined section. This curvature allows for a gradual transition in the contact interface, enabling smoother distribution of thermal stresses during expansion and contraction cycles, thereby reducing peak stress concentrations that would occur with abrupt geometric transitions.
2Strength
If the rotor and cylindrical rotating portion are tightly joined to maintain structural integrity, then the mechanical strength is improved, but rapid load variations cause deformation and damage to anticorrosive coatings
Solution Approach 1:
The gradual taper structure modifies the contact pressure distribution by changing the geometric parameters of the joined section. This creates a progressive load transfer mechanism that reduces sudden load variations, preventing the rapid stress changes that would otherwise cause deformation and anticorrosive coating damage while still maintaining adequate mechanical strength.
Solution Approach 2:
The tapered geometry acts as a built-in stress-distributing mechanism that cushions against rapid load variations before they can reach the anticorrosive coating. The gradual change in cross-sectional area provides a buffer zone that absorbs and distributes dynamic loads, protecting the coating from the harmful effects of sudden stress changes.
3Ease of manufacture
If a uniform cylindrical rotor design is used, then the manufacturing process is simple, but the joined section cannot withstand thermal expansion differences between metal and FRP materials
Solution Approach 1:
The invention modifies the rotor's outer diametrical surface from a uniform cylinder to a gradual taper structure. While this adds some manufacturing complexity, the change is achieved through standard machining or forming processes. The benefit is a significant improvement in thermal stress resistance, as the tapered geometry naturally distributes thermal expansion forces along the axial direction, preventing stress concentration and enhancing the reliability of the joined section.
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 load variation relaxation structure effectively mitigates thermal and centrifugal-induced stresses, enhancing the durability and corrosion resistance of vacuum pumps by preventing coating damage and maintaining improved gas discharge performance.
Implementation Method 1
Because of such a wide temperature range, large thermal stresses are generated by the difference in thermal expansion between the two materials at a high temperature. Since the thermal expansion coefficient of aluminum alloys is several times that of FRP, where the temperature rises with the operation time, the rotating portion made from a metal and located on the inner side rapidly expands.
Implementation Method 2
Under certain operation conditions, the temperature of the rotor of the vacuum pump can rise from normal temperature to about 150°C. Because of such a wide temperature range, large thermal stresses are generated by the difference in thermal expansion between the two materials at a high temperature.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Provided are a rotor having a load variation relaxation structure that relaxes load variations in the boundary portion of a cylindrical body and a cylindrical rotating portion, and a vacuum pump in which rotation performance (that is, discharge performance), reliability, and durability are improved over those in the related art by incorporating the cylindrical body. In the vacuum pump, a rotating portion made from a metal (aluminum alloy or the like) is provided with the load variation relaxation structure, which relaxes load variations caused by thermal stresses, in a joined section where the cylindrical rotating portion formed from a different material (FRP or the like) is joined. More specifically, any one from among a gentle taper, a curved section and a taper section, and a corner R is provided in the boundary portion of the rotating portion and the cylindrical rotating portion.