Physical Quantity Detection Device With Offset Port
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Solution Overview
Problem
Existing air flow rate measurement devices in internal combustion engines are prone to contamination by foreign matter, which can adhere to sensors and disrupt accurate readings.
Innovation Solution
A physical quantity detection device with a housing that includes a sub-passage and a pressure introduction passage with an introduction port offset from the side wall surface, creating a separation flow that reduces the influence of dynamic pressure and prevents foreign matter from entering, ensuring stable sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the introduction port is arranged at the side wall surface of the sub-passage, then it is easy to manufacture and install, but foreign matter can easily enter the pressure introduction passage and block the sensor chamber
Solution Approach 1:
The introduction port is positioned at a specific location (bottom surface or side surface) of the pressure introduction passage rather than uniformly distributed, creating a localized sampling point that avoids direct exposure to high-velocity flow and foreign matter while still capturing representative pressure information from the sub-passage
2Measurement precision
If the introduction port is positioned to capture dynamic pressure, then measurement sensitivity is improved, but water and foreign matter can flow into the introduction port and block the passage
Solution Approach 1:
The introduction port is strategically positioned at the bottom surface or specific side surface of the pressure introduction passage, creating a localized sampling point that captures pressure information while avoiding direct exposure to water and foreign matter flow paths
Solution Approach 2:
Instead of positioning the introduction port to directly face the flow direction to capture dynamic pressure, the port is positioned perpendicular to or offset from the main flow direction, using the side or bottom surface to indirectly sense pressure while preventing contamination
3Productivity
If a bypass flow path is formed inside the duct, then air flow rate measurement is enabled, but foreign matter adheres to the sensor to contaminate it
Solution Approach 1:
The measurement system is divided into separate functional components: the bypass flow path for sampling, the pressure introduction passage for pressure equalization, and the sensor chamber for measurement. This segmentation allows the sensor to be isolated from direct exposure to foreign matter while still capturing accurate pressure information
Solution Approach 2:
The pressure introduction passage acts as an intermediary between the bypass flow path and the sensor chamber, providing pressure equalization and filtering out foreign matter while allowing pressure information to pass through to the sensor
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 effectively prevents foreign matter from entering the pressure introduction passage and sensor chamber, maintaining accurate and stable pressure measurements by creating a negative pressure environment and reducing the impact of dynamic pressure.
Implementation Method 1
since the introduction port is arranged at a position offset outward from the side wall surface of the sub-passage, a separation flow can be formed between the side wall surface and the introduction port
Implementation Method 2
bring the surrounding environment of the introduction port into a negative pressure state
Data Source
AI summary
To obtain a physical quantity detection device capable of reducing an intake amount of air accompanied by foreign matter. A physical quantity detection device (20) of the invention includes a housing arranged in a main passage through which a measurement target gas (2) flows. The housing is provided with a second sub-passage (B) that takes in a part of the measurement target gas (2) flowing in the main passage, a circuit chamber (135) that accommodates a pressure sensor (320) that detects a pressure of the measurement target gas (2), and a pressure introduction passage (170) having one end opened in the middle of the second sub-passage (B) and the other end opened in the circuit chamber (135) and capable of introducing the pressure of the measurement target gas (2) from the second sub-passage (B) into the circuit chamber (135). In the pressure introduction passage (170), an introduction port (171) is arranged at a position offset outward from a side wall surface (152b) of the second sub-passage (B).