Gas Dividing System with Fixed Valve Opening and PID Adjustment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional gas dividing and supplying systems face issues with excessive gas flow (overshooting) at the start of supply, low responsiveness, and accuracy in flow rate control due to thermal-type mass flow sensors' temperature variations and pressure dependence, leading to decreased efficiency and product quality in semiconductor manufacturing.
Innovation Solution
A gas dividing and supplying system with thermal-type mass flow sensors and electrically-operated valves that maintain a fixed valve opening degree for the highest flow rate passage, adjust PID control parameters based on total flow rates, and use stainless steel diaphragm valves with elastic resin sheets to prevent sheet-leaking and simplify the structure, thereby enhancing control accuracy and responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thermal-type flow rate control devices are used to control gas flow in divided passages, then flow rate control is achieved, but excessive gas flow (overshooting) occurs at the start of supply and control accuracy deteriorates due to temperature variations and pressure dependence
Solution Approach 1:
The patent applies preliminary action by pre-opening changeover valves before starting gas supply to divided passages. This ensures that gas pathways are established in advance, preventing overshooting when supply begins. The valves are opened beforehand to a predetermined opening degree, allowing smooth gas flow without sudden surges that would cause control inaccuracies.
Solution Approach 2:
The patent implements dynamics by making valve opening degrees adjustable and controllable rather than fixed. The changeover valves can dynamically adjust their opening degree based on control signals, allowing the system to respond to changing flow requirements and prevent overshooting while maintaining accurate flow rate control under varying temperature and pressure conditions.
2Measurement precision
If conventional thermal-type flow rate control devices are used, then gas flow control is achieved, but the structure becomes complex and miniaturization is hindered due to large zero point variation and pressure-dependent detected flow rate
Solution Approach 1:
The patent applies parameter changes by correcting the detected flow rate based on pressure parameters. The system measures pressure in the divided passage and uses this information to correct the flow rate reading from the thermal-type sensor, compensating for pressure-dependent measurement errors. This allows accurate flow rate detection without requiring complex sensor designs.
Solution Approach 2:
The patent replaces complex mechanical flow control structures with a simpler system using changeover valves controlled by control units. Instead of relying on complex thermal-type flow rate control devices with multiple moving parts, the system uses electronically controlled valves that can be precisely actuated, enabling miniaturization and structural simplification while maintaining control accuracy.
3Adaptability or versatility
If gas flow rate switching is performed frequently, then process flexibility is improved, but responsiveness of divided flow rate control deteriorates due to long stabilization time
Solution Approach 1:
The patent applies preliminary action by pre-positioning changeover valves before flow rate switching is needed. When flow rate changes are required, the valves are already in optimal positions, eliminating the delay associated with valve movement and system stabilization. This enables frequent flow rate switching while maintaining rapid responsiveness.
Solution Approach 2:
The patent implements dynamics through dynamically controllable changeover valves that can rapidly adjust their opening degrees in response to control signals. This dynamic control capability allows the system to quickly adapt to changing flow rate requirements, maintaining high responsiveness even during frequent switching operations.
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 system effectively prevents overshooting, improves flow rate control accuracy, and increases responsiveness by maintaining a fixed valve opening degree and adjusting PID parameters, while simplifying the structure and reducing production costs.
Implementation Method 1
thermal-type mass flow sensors 291 to 29n disposed to the divided flow passages L1 to Ln, respectively
Implementation Method 2
valve sheets are made of elastic resin, and contact pressure between each of the valve elements and valve sheets of when the valves are fully-closed is created by elasticity of the valve sheets
Data Source
AI summary
An apparatus for dividing and supplying gas is provided with a flow rate control device, a plurality of divided flow passages of gas flowing from the flow rate control device, thermal-type mass flow sensors disposed to the divided flow passages, electrically-operated valves disposed on a downstream side of the thermal-type mass flow sensors, controllers that control the electrically-operated valves, and a flow ratio setting calculator that calculates a total flow rate, then calculates flow rates of the divided flow passages, and then inputs the calculated flow rates as set flow rates to each controllers. One of the divided flow passages with the highest set flow rate is put in an uncontrolled state, and opening degree for each of the rest divided flow passages is controlled, and then feedback control of the divided flow rate of each of the divided flow passages is implemented by each of the controllers.