Flow Detecting Device Guard Member Deflects Bypass Flow
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Solution Overview
Problem
Conventional thermal flow detecting devices suffer from low detection accuracy due to variations in heat radiation from the heating element, which is costly to manufacture with a conical shape, and are prone to errors from foreign matters and temperature variations.
Innovation Solution
A flow detecting device with a bypass passage and a heating element, where guard members are placed upstream to deflect the bypass flow, reducing heat radiation variation and protecting the lead portions from foreign matters, using a sensor body with a plug-in structure and a circuit module to maintain consistent temperature differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the axially end surface of the bobbin is made conical shape to reduce variation in protective coat thickness, then detection accuracy is improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent applies local quality by making only the axially end surface of the bobbin conical, while the main body remains cylindrical. This localized conical shape specifically addresses the protective coat thickness variation at the end surface without requiring the entire bobbin to be conical, thus reducing manufacturing complexity and cost while still improving detection accuracy.
Solution Approach 2:
The patent uses a simple conical shaping process that can be applied cost-effectively to the bobbin end surface, replacing the need for expensive precision ceramic forming. The conical shape is achieved through economical manufacturing methods that reduce overall device cost while maintaining measurement precision.
2Ease of manufacture
If the protective coat thickness varies at the axially end surface of the bobbin, then manufacturing is simplified, but heat radiation variation increases and detection accuracy decreases
Solution Approach 1:
The conical shape is applied locally at the axially end surface of the bobbin to specifically address the protective coat thickness variation problem at that location. This localized geometric modification ensures more uniform protective coat thickness at the end surface without complicating the overall manufacturing process.
Solution Approach 2:
The patent changes the geometric parameter of the bobbin end surface from flat to conical, which fundamentally alters how the protective coat is deposited. This parameter change results in more uniform coat thickness distribution at the end surface, reducing heat radiation variation and improving detection accuracy.
3Productivity
If the heating element is exposed to bypass flow directly, then flow detection is enabled, but foreign matters affect the lead portions causing detection errors
Solution Approach 1:
The guard member acts as an intermediary element positioned between the bypass flow and the lead portions. It allows the bypass flow to pass through for detection purposes while simultaneously protecting the lead portions from direct exposure to foreign matters in the flow, thus maintaining both detection capability and reliability.
Solution Approach 2:
The patent segments the flow path by introducing a guard member that creates distinct zones: one where bypass flow interacts with the heating element for detection, and another where the lead portions are shielded from direct flow exposure. This segmentation allows simultaneous achievement of flow detection and protection against contamination.
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
Enhances detection accuracy by reducing heat radiation variation and protecting the heating and lead portions from foreign matters, leading to improved output characteristics and reduced detection errors across varying flow rates.
Implementation Method 1
a heating element which generates heat by being supplied with electricity via the at least one lead portion for detecting the bypass flow in accordance with heat radiated from the heating element
Implementation Method 2
detecting the bypass flow in accordance with heat radiated from the heating element
Data Source
AI summary
A flow detecting device is provided to a fluid passage through which a main flow of fluid passes. The flow detecting device includes a sensor body, a heating element, a lead portion, and a guard member. The sensor body has a bypass passage through which a bypass flow is distributed partially from the main flow. The heating element is provided in the bypass passage. The lead portion connects with the heating element via a connecting portion. The heating element generates heat by being supplied with electricity via the lead portion for detecting the bypass flow in accordance with heat radiated from the heating element. The guard member is provided to an upstream of the connecting portion with respect to the bypass flow for deflecting the bypass flow from the connecting portion.