Thermal Air Flow Meter Sensor Mounting for Dimensional Variation Control
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Solution Overview
Problem
Existing flow-rate measuring devices face challenges in reducing dimensional variation between the detection element and the sub-passage wall surface, affecting noise performance, low flow rate sensitivity, and pulsation performance.
Innovation Solution
A flow-rate measuring device design where the sensor assembly is mounted on a circuit board such that the detection portion is closer to the housing, with a contact portion in contact with the housing, and a buffering material is used to absorb thickness variations, reducing stress on the connection points and minimizing dimensional variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensor assembly is mounted with the detection portion closer to the housing using a contact portion, then measurement precision is improved, but manufacturing precision becomes more difficult to control
Solution Approach 1:
A buffering material is introduced as an intermediary element between the sensor assembly and the housing. This buffering material absorbs dimensional variations and thickness differences, acting as a mediator that decouples the precision requirements of the detection portion positioning from the manufacturing tolerances of the housing and sensor assembly components.
Solution Approach 2:
The design changes the positioning parameter from direct rigid contact to contact through a buffering material. This parameter change allows the system to accommodate dimensional variations by introducing a compliant element that can deform or compress, thereby maintaining consistent positioning of the detection portion relative to the housing despite manufacturing tolerances.
2Object-affected harmful factors
If the detection portion is positioned closer to the housing, then noise performance is improved, but stress concentration increases at connection points
Solution Approach 1:
The buffering material serves as a pre-installed cushioning element between the sensor assembly and the housing. It absorbs and distributes mechanical stresses before they can concentrate at the connection points, providing protective cushioning that prevents stress concentration while maintaining the close positioning of the detection portion for optimal noise performance.
Solution Approach 2:
The buffering material functions as a flexible element that can deform under stress, distributing forces evenly across the contact area. This flexibility prevents rigid stress concentration at connection points while maintaining the necessary positioning, effectively using a flexible component to resolve the contradiction between close positioning and stress resistance.
Data Source
AI summary
An object is to improve measurement accuracy of a thermal air flow meter. A flow-rate measuring device comprising: a sensor assembly having a flow-rate detecting element; a circuit board on which the sensor assembly is mounted; and a housing on which the circuit board is mounted, wherein the sensor assembly is mounted on the circuit board such that a detection portion side of the flow-rate detecting element is closer to the housing, and the sensor assembly includes a contact portion in contact with the housing on the detection portion side.