Differential Pressure Flow Control With Zero-Output Valve Switching
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Solution Overview
Problem
Conventional fluid control devices exhibit unnatural behavior when switching from a closed to an open state, leading to negative flow rates due to backflow and pressure changes, which can mask abnormalities such as seat leaks or sensor failures.
Innovation Solution
A fluid control device with upstream and downstream pressure sensors, an actual flow rate calculation unit, and a switching unit that outputs a zero value when the valve is closed, and switches to the calculated flow rate when the pressure difference exceeds a threshold, preventing negative outputs and allowing for abnormality detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the output is simply switched from zero value to calculated flow rate when the fluid control valve is opened, then the flow rate measurement becomes available, but the output behaves unnaturally and may become negative immediately after switching
Solution Approach 1:
The patent applies preliminary action by checking the pressure difference between upstream and downstream sides before switching from zero output to calculated flow rate output. The switching unit only transitions to calculated flow rate when the pressure difference exceeds a predetermined threshold, ensuring that the system is ready for accurate measurement before enabling it, thus preventing unnatural negative outputs.
Solution Approach 2:
The patent uses feedback by continuously monitoring the pressure difference between upstream and downstream sides and using this information to control the switching between zero output and calculated flow rate output. This feedback mechanism ensures that the output transition occurs only under appropriate conditions, maintaining reliability while enabling productivity.
2Reliability
If a zero output function is used when the fluid control valve is closed, then negative outputs are prevented, but abnormalities such as seat leaks or sensor failures cannot be detected
Solution Approach 1:
The patent uses feedback by monitoring the pressure difference between upstream and downstream sides to determine when to switch from zero output to calculated flow rate output. This feedback mechanism enables abnormality detection because calculated flow rate becomes available when the valve is open and pressure difference is sufficient, allowing detection of seat leaks or sensor failures while maintaining zero output validity when closed.
3Speed
If the calculated flow rate is output immediately when the valve opens, then real-time flow monitoring is achieved, but the output becomes negative due to backflow and pressure changes
Solution Approach 1:
The patent applies preliminary action by requiring the pressure difference to exceed a predetermined threshold before switching from zero output to calculated flow rate output. This preliminary condition ensures that backflow and pressure stabilization have occurred, preventing negative outputs while enabling real-time monitoring as soon as the system is ready, thus balancing speed and precision.
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
Prevents unnatural behavior and allows for prompt detection of abnormalities by ensuring a zero output when the valve is closed and a calculated flow rate is abnormal, while preventing immediate negative outputs when switching states.
Implementation Method 1
an upstream pressure sensor, and a downstream pressure sensor on a flow path
Implementation Method 2
differential pressure-type mass flow controller configured to output a zero value regardless of a calculated flow rate calculated based on a differential pressure
Data Source
AI summary
In order to prevent unnatural behavior of a calculated flow rate, provided is a fluid control device in which a fluid control valve and upstream and downstream pressure sensors are provided on a flow path. The device includes a calculation unit configured to calculate a flow rate based on measured pressures; and an output unit configured to output the calculated flow rate, and exhibit a zero output function of outputting a zero value regardless of the calculated flow rate when the valve is in a closed state. The device is further configured to switch between execution and stop of the zero output function, and when the valve is in an open state and a difference between the measured pressures of the pressure sensors is larger than a threshold, stop the zero output function and cause the flow rate output unit to output the calculated flow rate.