Turbomolecular Pump Pressure Sensing via Downstream Measurement Tap
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Solution Overview
Problem
Existing vacuum pumps, particularly turbomolecular pumps, face challenges in accurately determining high vacuum pressures at the suction side due to limitations in measurement technologies like Pirani systems, which are ineffective at pressures below 5·10−4 mbar.
Innovation Solution
Incorporating a measurement tap downstream of the pump stage to indirectly measure increased gas pressure, using a Pirani or capacitive measuring tube, and applying a correction factor to estimate the suction side pressure based on the measured pressure and known compression ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Pirani measurement system is used to monitor pressure, then measurement accuracy and cost-effectiveness are improved, but it cannot be used at high vacuum pressures (smaller than 5·10−4 mbar)
Solution Approach 1:
The pressure measurement range is segmented into different zones: rough vacuum (measured directly at suction side), pre-vacuum (measured at measurement tap), and high vacuum (calculated indirectly). The measurement tap is positioned to sample pressure from a region where the pressure is higher than the suction side, enabling use of Pirani gauges which cannot measure high vacuum directly.
Solution Approach 2:
The measurement tap acts as an intermediary element that samples pressure from an intermediate region between the suction side and the pump outlet. This intermediate pressure measurement serves as a mediator to indirectly determine the suction side pressure through known compression ratios, bypassing the limitation of Pirani gauge measurement range.
2Measurement precision
If pressure is measured directly at the suction side, then accurate high vacuum pressure determination is required, but this requires expensive and complex measurement devices
Solution Approach 1:
Instead of using expensive, complex high-vacuum-capable measurement devices, the patent employs inexpensive Pirani gauges that operate at higher pressures. The measurement tap provides a sampling point where the pressure is sufficient for Pirani gauge operation, replacing the need for costly specialized equipment.
Solution Approach 2:
The measurement tap creates a copy of the pressure condition from the pump interior (a region with higher pressure) and brings it to the measurement location. This pressure copy can be measured with simple, inexpensive devices, and the original suction side pressure is reconstructed using known compression characteristics.
3Measurement precision
If a measurement tap is positioned at the suction side, then direct pressure measurement is possible, but the pressure is too low for conventional measurement technologies
Solution Approach 1:
Instead of measuring pressure at the low-pressure suction side, the measurement tap is positioned to sample from a high-pressure region within the pump or downstream. This inverts the conventional approach by measuring at higher pressure and working backwards to determine the lower suction side pressure.
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
Enables reliable and cost-effective pressure determination at the suction side of vacuum pumps, even in high vacuum conditions, by leveraging existing measurement technologies and reducing manufacturing costs through multi-functional components like flood openings.
Implementation Method 1
The Pirani measurement system, that is above all characterized by its inexpensive use with high measurement accuracy, is, for example, used to monitor the process and in particular the pressure
Data Source
AI summary
The present invention relates to a vacuum pump, in particular to a turbomolecular pump, having at least one pump stage and having a pressure determination unit for determining a pressure present at a suction side of the vacuum pump, said pump comprising a measurement device, with a measurement tap of the measurement device being provided in the region of the pump stage or downstream of the pump stage.