Cryopump Vent Valve Control via Pressure Stabilization
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Solution Overview
Problem
Cryopumps face measurement errors in pressure sensing during regeneration due to temperature fluctuations and gas mixtures, leading to inappropriate vent valve operation, which can result in backflow or foreign matter introduction.
Innovation Solution
A cryopump with a pressure sensor generating time-series data and a controller that detects pressure stabilization to control the vent valve's opening, ensuring accurate timing and reducing measurement errors by using a relative pressure sensor and mechanical safety valve operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a pressure sensor is used to control the vent valve during cryopump regeneration, then the vent valve operation can be automated, but measurement errors occur due to temperature fluctuations and gas mixtures
Solution Approach 1:
The system performs preliminary heating of the cryopump to a predetermined temperature before regeneration, and preliminarily opens the vent valve before pressure measurement. This ensures the pressure sensor operates in a stable temperature environment, eliminating temperature-induced measurement errors while maintaining automated control
Solution Approach 2:
The system preemptively opens the vent valve to prevent pressure buildup before measurement errors can cause problematic conditions. By anticipating potential measurement inaccuracies, the system takes preventive action to ensure safe operation during regeneration
2Productivity
If the vent valve is controlled based on pressure sensor readings, then regeneration can be optimized, but inappropriate vent valve operation occurs leading to backflow or foreign matter introduction
Solution Approach 1:
The vent valve is opened preliminarily before pressure measurement and kept open during measurement. This ensures the valve remains in a safe state regardless of measurement accuracy, preventing backflow and foreign matter introduction while allowing optimized regeneration to proceed
Solution Approach 2:
The system maintains the vent valve in an open state as a protective measure during pressure measurement, cushioning against potential measurement errors that could lead to inappropriate valve closure. This protective approach ensures reliability while regeneration efficiency is maintained through proper timing
3Measurement precision
If a high-precision absolute pressure sensor is used, then measurement accuracy improves, but manufacturing cost increases
Solution Approach 1:
The system changes the operating parameters of the pressure sensor by controlling the temperature environment (heating to predetermined temperature) and timing measurements to occur when conditions are favorable. This allows an inexpensive relative pressure sensor to function with accuracy comparable to expensive absolute pressure sensors
Solution Approach 2:
The system uses an inexpensive relative pressure sensor instead of a costly absolute pressure sensor, compensating for the cheaper component's limitations through controlled measurement conditions and timing. The sensor is used in a controlled manner where its limitations are minimized, achieving the desired functionality at lower cost
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 solution ensures appropriate vent valve operation during cryopump regeneration, minimizing backflow and foreign matter introduction while reducing manufacturing costs through the use of an inexpensive relative pressure sensor.
Implementation Method 1
a pressure sensor that measures a pressure in the cryopump container and generates time-series pressure data indicating the measured pressure
Implementation Method 2
capable of being mechanically opened by a differential pressure between inside and outside the cryopump container
Implementation Method 3
detects stabilization of the measured pressure based on the time-series pressure data from the pressure sensor
Data Source
AI summary
A cryopump includes a cryopump container, a pressure sensor that measures a pressure in the cryopump container and generates time-series pressure data indicating the measured pressure, a vent valve that is provided on the cryopump container, is electrically operable to open and close, and is capable of being mechanically opened by a differential pressure between inside and outside the cryopump container, and a controller that, during cryopump regeneration, detects stabilization of the measured pressure based on the time-series pressure data from the pressure sensor and controls the vent valve to open upon detection of the stabilization of the measured pressure.