Thermal Air Flow Meter Venting for Diaphragm Pressure Balance
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Solution Overview
Problem
Existing thermal air flow meters experience diaphragm deformation due to pressure differences between the auxiliary passage and circuit chamber, particularly in high flow rate regions, leading to reduced accuracy in air flow rate measurement.
Innovation Solution
The air flow meter incorporates a configuration with a diaphragm having a recessed section on its reverse surface, connected via multiple ventilation pathways to the auxiliary passage, including a first and second ventilation pathway, enhancing ventilation performance and maintaining equal pressure across the diaphragm surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single airflow passage is formed to connect the recessed section to the auxiliary passage, then the structure is simple, but diaphragm deformation occurs under high flow rate conditions due to pressure difference
Solution Approach 1:
The single airflow passage is segmented into multiple ventilation pathways (first ventilation pathway and second ventilation pathway) that connect the recessed section to the auxiliary passage. This segmentation allows air to flow through multiple routes simultaneously, equalizing pressure on both sides of the diaphragm more effectively under high flow rate conditions, thereby preventing diaphragm deformation while maintaining structural simplicity.
2Productivity
If the auxiliary passage operates at high flow rate, then measurement range is improved, but negative pressure in the auxiliary passage causes diaphragm deformation
Solution Approach 1:
The invention creates different local pressure conditions by establishing multiple ventilation pathways with potentially different flow characteristics. The first and second ventilation pathways provide localized pressure equalization routes that compensate for the negative pressure in the auxiliary passage, maintaining diaphragm shape stability even when the auxiliary passage operates at high flow rates.
3Measurement precision
If ventilation pathways are increased to prevent diaphragm deformation, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The multiple ventilation pathways are merged into a single integrated package structure where the first package section and second package section are formed as one unified component. The airflow passages and ventilation pathways are combined within the same package housing, eliminating the need for separate components and minimizing structural complexity while achieving effective pressure equalization.
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 configuration effectively suppresses diaphragm deformation and improves the accuracy and responsiveness of air flow rate measurements by maintaining uniform pressure across the diaphragm surfaces, even in high flow rate conditions.
Implementation Method 1
The thermal air flow meter is a device that measures an air flow rate by performing heat transfer with air to be measured
Implementation Method 2
the recessed section communicates with the auxiliary passage via a plurality of ventilation pathways including at least a first ventilation pathway communicating with the auxiliary passage via the airflow passage and a second ventilation pathway communicating with the auxiliary passage through a pathway different from the first ventilation pathway via the airflow passage
Data Source
AI summary
This air flow rate meter comprises an enclosure having an auxiliary passage and a circuit chamber, and a flow rate detection sensor. The flow rate detection sensor has a diaphragm in which a flow rate detection unit is formed on a main surface, a recessed section formed on the reverse-surface side of the diaphragm, and a package part having a first package section and a second package section, the first package section being positioned in the auxiliary passage, and the second package section being positioned in the circuit chamber. An airflow passage linked to the recessed section is formed in the interior of the package part. The recessed section communicates with the auxiliary passage via a plurality of ventilation pathways that communicate with the auxiliary passage via the airflow passage.