Turbomolecular Pump Dynamic Balancing and Clearance Adjustment
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Solution Overview
Problem
Turbomolecular pumps used in vacuum deposition processes face challenges due to condensation of process materials on rotor blades, leading to unbalanced conditions and premature bearing failure, which requires frequent maintenance and replacement.
Innovation Solution
The turbomolecular pump features adjustable conical or frustum-shaped stator and rotor stacks with a rotor drive system using coils and magnets for dynamic balancing, allowing for real-time adjustment of clearances and balancing during operation, utilizing optical sensors and actuators to counteract imbalances and extend pump life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the turbomolecular pump operates at high rotational speeds to achieve low vacuum levels, then the vacuum pressure is improved, but the bearing stress increases leading to premature failure
Solution Approach 1:
The patent applies dynamic balancing by making the rotor system adjustable during operation. The rotor can be repositioned axially to change clearance distances, and weighting elements can be added or removed to dynamically adjust the center of gravity, allowing the system to adapt to changing conditions and maintain balance at high speeds
Solution Approach 2:
The patent changes physical parameters of the rotor system by adjusting axial positions and modifying weight distribution. By varying the clearance distances and adding/removing weighting elements, the system can optimize its operational parameters to reduce bearing stress while maintaining high rotational speeds
2Productivity
If the pump is used in PVD processes where metal or chemical vapors deposit on rotor blades, then the vacuum deposition function is improved, but the rotor becomes unbalanced shortening bearing life
Solution Approach 1:
The patent makes the rotor system dynamically adjustable by allowing axial repositioning and modification of weight distribution. This enables the system to compensate for imbalances caused by vapor deposition by adjusting the center of gravity and clearance distances during or between operational cycles
Solution Approach 2:
The patent allows for the removal and replacement of weighting elements on the rotor blades. When deposition causes imbalance, affected weighting elements can be removed and replaced with new ones, effectively discarding the imbalanced state and recovering rotor balance without replacing the entire rotor
3Device complexity
If fixed clearance between stator and rotor vanes is used, then the pump structure is simplified, but condensation buildup requires frequent maintenance
Solution Approach 1:
The patent transforms the fixed clearance structure into a dynamic, adjustable system. The rotor can be repositioned axially to change clearance distances between stator and rotor vanes, allowing the system to adapt to condensation buildup by increasing clearances when needed, thereby maintaining operational continuity
Solution Approach 2:
The patent enables preliminary adjustment of clearance distances before condensation becomes problematic. By allowing axial repositioning of the rotor, the system can proactively increase clearances to prevent excessive buildup from causing failures, rather than waiting for maintenance to be required
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 solution enables the turbomolecular pump to maintain optimal balance and operation even in high-temperature, chemically challenging environments, reducing the need for frequent maintenance and extending the lifespan of bearings by dynamically adjusting clearances and balancing the rotor stack during operation.
Implementation Method 1
turbomolecular pumps work on the principle that gas molecules can be given momentum in a desired direction by repeated collision with a moving solid surface
Implementation Method 2
the mechanical energy of the vanes is transferred to the gas molecules. With this newly acquired momentum, the gas molecules enter into the gas transfer areas in the stator vanes
Implementation Method 3
the actuator or drive mechanism of the pump is formed from coils attached to the blades of upper stage of a rotor stack which are controlled to interact with a plurality of stationary magnets attached to the housing of the pump to rotate the rotor stack
Data Source
AI summary
A turbomolecular pump is provided. In one arrangement, a stator stack and rotor stack have corresponding conical or frustum shapes that allow for adjusting the clearance between the stator vanes and rotor vanes of the pump to provide adjustable compression ratios and/or to adjust clearances. In another arrangement, the actuator or drive mechanism of the pump is formed from coils attached to the upper stage of rotor vanes which are controlled to interact with a plurality of stationary magnets attached to the housing of the pump to rotate the stator stack. In another arrangement, a control system of the pump utilizes the coils of the rotor drive to dynamically balance the pump during operation.