Thermal Gas Flow Meter Discharge Groove Backflow Prevention
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Solution Overview
Problem
Conventional thermal type air flow rate sensors for internal combustion engines have high production costs and reduced measuring precision due to complex support structures, which also lead to reliability issues from dust, oil, and water contamination, especially at high flow rates.
Innovation Solution
A thermal type flow meter with a simplified two-stage support structure and a discharge groove that prevents backflow and dust accumulation, featuring a heat generating resistor and lead electrode on a tabular substrate, firmly fixed with an adhesive agent, and a concave portion arranged parallel to the flow direction, enhancing reliability and cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a three-stage support structure is used to accommodate the flow rate detecting element, then the flow rate detecting element can be positioned with its surface at a predetermined height relative to the support body, but the support body becomes complicated in shape and production cost increases
Solution Approach 1:
The patent extracts the positioning function from the complex three-stage support structure and implements it through a simplified two-stage structure combined with a positioning rib that protrudes from the bottom surface of the concave portion. This positioning rib is specifically designed to engage with the flow rate detecting element, providing the necessary height positioning without requiring multiple support stages.
2Ease of manufacture
If a gap is formed between the flow rate detecting element and the support body to facilitate assembly, then assembly is easier, but part of the measured air flow flows to the back surface of the flow rate detecting element, reducing measuring precision
Solution Approach 1:
The patent introduces a sealing member as an intermediary element that fills the gap between the flow rate detecting element and the support body. This sealing member prevents air flow from leaking through the gap to the back surface of the detecting element, while still allowing for assembly. The sealing member acts as a mediator that maintains both the assembly feasibility and measurement precision.
3Reliability
If the concave portion has a deep third stage surface to form a back chamber for dust collection, then dust accumulation is reduced, but the structure becomes more complex and production cost increases
Solution Approach 1:
The patent enables the flow rate detecting element itself to serve the dust collection function through its own structure. The back surface of the flow rate detecting element is designed to accumulate dust and contaminants, eliminating the need for a separate deep back chamber in the support body. This self-service approach maintains dust resistance while simplifying the overall structure.
4Stability of the object's composition
If the flow rate detecting element is firmly fixed with adhesive agent to improve stability, then positioning stability is improved, but the adhesive agent may accumulate dust and oil, affecting reliability
Solution Approach 1:
The patent extracts the adhesive agent from the gap area and applies it only to specific bonding surfaces where it is needed for secure mounting. By removing the adhesive agent from the gap region, the source of dust and oil accumulation is eliminated, while the positioning stability is maintained through proper adhesive application on the bonding surfaces.
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
The solution improves measuring precision and reliability by reducing backflow and dust accumulation, while maintaining a low production cost through a simplified structure and effective discharge of contaminants, ensuring accurate flow rate detection even at high flow rates.
Implementation Method 1
a heat generating resistor (not shown) for detecting a flow rate is formed in the diaphragm portion 56a
Implementation Method 2
a fluid temperature detecting resistor (not shown) for detecting a temperature of a measured fluid is formed in the diaphragm portion 56b
Data Source
AI summary
The invention provides a thermal type flow meter which has a high reliability and a low cost. In a thermal type flow meter provided with a flow rate detecting element in which at least a heat generating resistor and a lead electrode are formed on a surface of a tabular substrate, and a support body in which a concave portion accommodating the flow rate detecting element is formed on a surface, and in which the flow rate detecting element is firmly fixed and accommodated by an adhesive agent in a back surface of the tabular substrate and a part of a bottom surface of the concave portion, an approximately straight discharge groove which is deeper than a bottom surface of the concave portion and passes through both end surfaces in upward and downward sides of the concave portion is formed from the upstream side of the support body concave portion to the downstream side, between the cavity of the tabular substrate and the back surface region of the tabular substrate in which the lead electrode is formed. Accordingly, it is possible to achieve the thermal type flow meter which has the high reliability and the low cost.