Diagnostic Mechanism for Mass Flow Controller Clogging Detection
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Solution Overview
Problem
The existing diagnostic methods for mass flow controllers and flow rate sensors are complex and difficult to use in real-world applications due to the numerous parameters that need to be set for accurately detecting abnormalities in flow passages, leading to complications in diagnosing clogging issues.
Innovation Solution
A diagnostic mechanism that controls the flow rate control valve to maintain a target flow rate value, outputs an inspection value based on the time integral of the measurement flow rate during a defined diagnostic period from the closure of the flow passage upstream of the sensor to when the measurement and target flow rates are nearly equal, and compares this value to predetermined specifications to diagnose abnormalities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple parameters (pressure drop amount, pressure drop time, start time, end time) are set for accurate abnormality detection, then measurement precision is improved, but device complexity increases and ease of operation deteriorates
Solution Approach 1:
The patent extracts and eliminates unnecessary diagnostic parameters, retaining only the essential time integral of flow rate measurement. This simplification removes the complexity of setting multiple parameters (pressure drop amount, pressure drop time, start time, end time) while preserving the core diagnostic function of detecting flow passage abnormalities.
Solution Approach 2:
The time integral of flow rate measurement serves multiple diagnostic purposes simultaneously - it detects both the presence of abnormalities and provides a basis for determining abnormality causes. This multi-functional parameter replaces the need for multiple separate measurements and parameter settings.
2Reliability
If multiple parameters are configured for comprehensive diagnosis, then reliability of diagnosis is improved, but ease of operation worsens due to numerous settings required
Solution Approach 1:
The patent extracts the essential diagnostic information contained in the time integral of flow rate measurement, eliminating the need to configure multiple separate parameters. This single parameter reliably indicates both abnormality presence and potential causes without requiring complex parameter settings.
3Measurement precision
If diagnostic period is extended to capture complete flow rate behavior, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent performs preliminary integration of the flow rate measurement throughout the diagnostic period, capturing the complete flow rate behavior in advance. This pre-computed time integral value can then be immediately compared against reference values to rapidly determine abnormality presence and causes, eliminating the need for extended real-time monitoring.
Data Source
AI summary
A diagnostic mechanism includes: a flow rate control part configured to control an opening degree of a flow rate control valve provided in a flow passage so that a measurement flow rate value outputted from a flow rate sensor becomes a target flow rate value; an inspection value output part configured to output an inspection value related to a time integral of the measurement flow rate value in a diagnostic period which is defined in correspondence with a part of a period from a time point of closing the flow passage upstream of the flow rate sensor to a time point of expiration of a state that the measurement flow rate value and the target flow rate value are substantially nearly equal; and a diagnosing part configured to compare the inspection value and a predetermined specified value to diagnose whether an abnormality relating to the flow rate sensor is present.