Mass Flow Controller with Pressure-Adaptive Control Mode Switching
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Solution Overview
Problem
Conventional mass flow rate-controlling apparatuses face challenges in maintaining high controllability due to pressure variations, which can lead to deteriorated control of mass flow rates, especially when pressure variations occur upstream of the mass flow rate sensor, resulting in increased facility costs and inadequate absorption of pressure fluctuations.
Innovation Solution
The apparatus incorporates a pressure-detecting means to switch between two control modes based on pressure variations, using a first control mode for minor variations and a second mode that adjusts valve-operating voltage based on stored data and valve characteristics when pressure variations exceed a threshold, effectively absorbing pressure changes and maintaining precise mass flow rate control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pressure variations occur upstream of the mass flow rate sensor, then the mass flow rate control deteriorates, but adding pressure absorption mechanisms increases facility cost
Solution Approach 1:
The control system dynamically adjusts the valve operating voltage based on detected pressure variations. When pressure variation exceeds a threshold, the system switches to a different control mode that compensates for pressure effects, allowing adaptive response to changing conditions without fixed structural additions
Solution Approach 2:
The system changes the control parameter from simple flow rate feedback to a composite control that includes pressure compensation. By modifying the valve operating voltage based on pressure data and stored valve characteristics, the system maintains control accuracy without adding physical pressure absorption hardware
2Device complexity
If conventional mass flow rate control is used without pressure compensation, then the control is simple, but pressure variations cause deteriorated mass flow rate control
Solution Approach 1:
The system implements feedback control by detecting pressure variations and using this information to adjust the valve operating voltage. The control unit continuously monitors pressure and modifies the control signal accordingly, creating a closed-loop system that maintains precision without overly complex hardware
Solution Approach 2:
The system stores valve characteristics in advance, which are then used to determine the appropriate valve operating voltage when pressure variations occur. This pre-stored data allows the system to quickly compensate for pressure effects without complex real-time calculations or additional hardware
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 approach enables high controllability of mass flow rates by effectively absorbing pressure variations, ensuring the mass flow rate remains consistent despite upstream pressure fluctuations, thereby improving the reliability and precision of gas flow control in semiconductor production processes.
Implementation Method 1
a sensor pipe 14 for flowing a smaller amount of a gas than in the bypass pipes 12 at a constant ratio... A pair of series-connected controlling resistor lines R1, R4 are wound around the sensor pipe 14
Implementation Method 2
a pressure-detecting means 42 attached to the fluid flow path 6 for detecting the pressure of the fluid at a predetermined time interval
Implementation Method 3
a flow rate-controlling valve mechanism 10 positioned on the downstream side of the flow path 6... the flow rate-controlling valve 20 comprises a diaphragm 22 constituted by a flexible metal plate
Data Source
AI summary
A mass flow rate-controlling apparatus including a mass flow rate-detecting mechanism 8 a flow rate-controlling valve mechanism 10 and a mechanism 44 for controlling the flow rate-controlling valve mechanism based on a flow rate-setting signal S0 input from outside and a flow rate signal S1, the flow path being provided with a pressure-detecting mechanism 42 for detecting the pressure of the fluid to output the detected pressure signal, so that the controlling mechanism selectively switches a first control mode for controlling the mass flow rate based on the flow rate signal and the flow rate-setting signal without using the detected pressure signal, and a second control mode for controlling the mass flow rate based on the detected pressure signal, the flow rate signal and the flow rate-setting signal, based on a pressure variation obtained from the detected pressure signal.