Pressure Flow Control Valve Closure to Prevent Gas Undershoot
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Solution Overview
Problem
Conventional pressure-type flow rate control devices face challenges in achieving high responsiveness and preventing undershoot when changing flow rates, particularly in applications requiring rapid pulsed gas supply, such as Atomic Layer Deposition, due to issues with control valve closure and pressure regulation.
Innovation Solution
A pressure-type flow rate control device with a control valve and upstream pressure sensor, utilizing an arithmetic processing circuit to perform feedback control with an exponential function target value that is more gradual than the pressure drop characteristic data, ensuring controlled closure and reducing the risk of undershoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the control valve is rapidly closed to reduce upstream pressure for high responsiveness, then the flow rate control speed is improved, but undershoot occurs and the control valve may remain closed causing time delay
Solution Approach 1:
The patent applies dynamics by making the control valve closure speed variable rather than constant. The arithmetic processing circuit dynamically adjusts the closure speed based on real-time upstream pressure feedback, transitioning from rapid initial closure to progressively slower closure as pressure approaches the target value. This dynamic adjustment prevents the control valve from remaining fully closed and eliminates time delays while maintaining high responsiveness.
Solution Approach 2:
The patent implements feedback control where the upstream pressure sensor continuously monitors pressure and feeds this information back to the arithmetic processing circuit. The circuit compares actual pressure with target pressure and adjusts the control valve operation accordingly, preventing undershoot by slowing closure when approaching the target pressure and ensuring the valve opens appropriately to maintain stable control.
2Reliability
If the control valve is gradually closed at constant speed to avoid sudden pressure change, then undershoot is prevented, but responsiveness is deteriorated due to longer transition time
Solution Approach 1:
The patent replaces constant-speed closure with dynamic speed adjustment. The closure speed starts rapidly to achieve quick response, then progressively slows down as the upstream pressure approaches the target value. This dynamic speed variation allows the system to achieve both fast transition and stable pressure control without the time delays associated with constant gradual closure.
Solution Approach 2:
The patent changes the operating parameter of control valve closure speed during the control process. Instead of maintaining a fixed closure speed, the system varies the closure speed parameter based on the pressure difference between current and target values, enabling rapid initial response while preventing undershoot through progressive speed reduction near the target 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
This approach enables effective flow rate control with reduced undershoot and improved responsiveness, particularly when transitioning to smaller flow rates, enhancing the device's ability to handle high-speed pulsed gas supply demands.
Implementation Method 1
an upstream pressure sensor for detecting a pressure between the restriction part and the control valve
Implementation Method 2
a pressure-type flow rate control device can control the flow rate of various fluids with high accuracy by a relatively simple mechanism, for example, a combination of a piezo element driven control valve and a restriction part (orifice plate or critical nozzle)
Data Source
AI summary
A pressure-type flow rate control device includes a restriction part; a control valve provided upstream of the restriction part; an upstream pressure sensor for detecting pressure between the restriction part and the control valve; and an arithmetic processing circuit connected to the control valve and the upstream pressor sensor. The device is configured to perform flow rate control by controlling the control valve according to an output of the upstream pressure sensor. The arithmetic processing circuit performs an operation of closing the control valve in order to reduce a flow rate of a fluid flowing through the restriction part, and performs an operation of closing the control valve by feedback control in which a target value is an exponential function more gradual than the pressure drop characteristic data when a gas flows out of the restriction part.