Humidity Sensor Bypass Passage for Intake Air Contamination
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Solution Overview
Problem
Current sensor structures for internal combustion engines face challenges in accurately measuring humidity while preventing the entry of contaminants and water droplets, especially in harsh environments where sensor accuracy and responsiveness are critical.
Innovation Solution
A sensor structure that integrates a humidity sensing element within a mass airflow measurement device, utilizing a bypass air passage with strategically positioned air communication channels and a housing design that minimizes contamination risk, allowing for accurate humidity measurement while isolating the sensing element from contaminants and water droplets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the humidity sensor is placed in the intake air passage to measure humidity accurately, then measurement precision is improved, but the sensor becomes vulnerable to contamination by contaminants and water droplets
Solution Approach 1:
The intake air passage is divided into a main passage and a bypass passage. The bypass passage includes a first communication channel that allows air to communicate with the humidity sensor, and a second communication channel that allows air to communicate with the outside atmosphere. This segmentation enables the sensor to be protected from direct exposure to contaminants while still maintaining accurate humidity measurement capability through controlled air flow paths.
Solution Approach 2:
Air acts as an intermediary medium to transfer humidity information to the sensor while filtering out contaminants. The bypass passage with its communication channels allows air to carry humidity data to the sensor without directly exposing the sensor to contaminants and water droplets in the main intake air passage.
2Device complexity
If multiple sensors are integrated into a single housing to reduce part count and simplify wire harnesses, then device complexity is reduced, but the risk of contamination to all sensors increases
Solution Approach 1:
The sensor housing is segmented into multiple isolated compartments, each containing different sensors (mass airflow sensor, temperature sensor, humidity sensor). Each compartment has its own air communication channels that are independently controlled, allowing each sensor to be protected from contaminants while maintaining functional integration. This segmentation prevents contamination spread between sensors while preserving the benefits of integrated design.
3Object-affected harmful factors
If the air filter element is made more effective at capturing contaminants to protect sensors, then anti-contamination property is improved, but pressure loss increases causing engine output reduction
Solution Approach 1:
The bypass passage with its communication channels extracts a portion of the air flow away from the main filtered path. This allows the main air filter to maintain its contaminant capture function while the bypass passage provides an alternative route that reduces overall pressure loss. The humidity sensor is positioned to access humidity information through this extracted bypass air flow rather than through the main filtered air path.
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 enables precise humidity measurement with enhanced anti-contamination properties, improving sensor accuracy and responsiveness while reducing the risk of contamination, thus addressing the limitations of existing technologies.
Implementation Method 1
a mass airflow measurement device of a heating resistor type is known (see JP Patent No. 3523022). This utilizes the fact that the heat quantity taken away from the heating resistor has a correlation with an inflow flow rate
Implementation Method 2
a humidity sensor is a sensor that has high sensitivity to contamination, therefore, an implementation structure that achieves all of measurement accuracy, measurement responsiveness, and anti-contamination property will be a problem
Data Source
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AI summary
In relation to a humidity sensor sensitive to water and contamination, a sensor implementation structure that achieves both the protection performance against water and contaminants and measurement performance such as humidity responsiveness is provided. A sensor structure has a mass airflow measurement element that measures a mass airflow flowing in an intake pipe 1, a humidity sensing element 5 that senses humidity of air flowing in the intake pipe 1, a housing structural component 7 having a connector that carries out input/output to/from outside and a terminal component 17 of the connector, and a bypass passage 14 that is composed by using part of the housing structural component 7 and takes in part of the air that flows in the intake pipe 1, the mass airflow measurement element being mounted in the bypass passage 14; wherein space 18 is provided in the housing structural component 7 in the vicinity of the bypass passage 14, the humidity sensing element 5 is mounted in the space 18, and the part of the space 18 does not have a structure sealed by an adhesive, a seal material, or the like.