Airflow Meter Humidity Sensor Heat Compensation

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Solution Overview

Problem

Existing airflow meters with humidity sensors struggle to accurately measure intake air humidity due to increased temperature from the engine heat, leading to reduced structural flexibility and increased risk of dust and water contamination, which affects measurement accuracy.

Innovation Solution

An airflow meter design that includes a humidity sensor within a sub-bypass passage, a flow rate sensor, and an intake air temperature sensor, with a humidity correction section that adjusts the humidity signal based on the intake air temperature signal to mitigate heat transmission effects and maintain high measurement accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the humidity sensor is disposed in the center area of the intake duct to reduce heat transmission from the inner wall, then the temperature measurement accuracy is improved, but the structural flexibility of the airflow meter is considerably lowered

Engineering Contradiction:

Improvehumidity measurement accuracyVSAvoidstructural flexibility

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent introduces a temperature sensor as an intermediary element that measures the actual temperature of the humidity sensor. This temperature information is then used by a correction unit to compensate for heat transmission effects, allowing the humidity sensor to be positioned in the center area (improving measurement accuracy) without being constrained by heat transmission issues, thereby maintaining structural flexibility

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the parameter being measured from just humidity to a combination of humidity and temperature. By measuring temperature simultaneously and using it to correct humidity readings, the system can accommodate the humidity sensor in positions that would otherwise be problematic due to heat transmission, thus improving both measurement accuracy and structural flexibility

Inventive Principle:

Principle #35Parameter changes

2Temperature

If the humidity sensor is disposed in the center area of the intake duct, then heat transmission from the inner wall is reduced, but the sensor is subjected to a large amount of dust and water making it easily dirtied

Engineering Contradiction:

Improveheat transmission reductionVSAvoiddust and water contamination

Core Design Contradiction:

TemperatureVSObject-affected harmful factors

Solution Approach 1:

The patent implements a feedback mechanism where the temperature sensor continuously monitors the temperature of the humidity sensor, and this information is fed back to the correction unit. The correction unit uses this feedback to dynamically adjust humidity readings, compensating for the effects of dust and water contamination that occur when the sensor is positioned in the center area exposed to high velocity flow

Inventive Principle:

Principle #23Feedback

3Object-affected harmful factors

If the humidity sensor is disposed in the inner passage of the airflow meter to keep it clean, then contamination is reduced, but heat transmission from the intake duct increases causing temperature changes that lower measurement accuracy

Engineering Contradiction:

Improvesensor contaminationVSAvoidhumidity measurement accuracy

Core Design Contradiction:

Object-affected harmful factorsVSMeasurement precision

Solution Approach 1:

The temperature sensor acts as an intermediary that bridges the gap between the humidity sensor and the heat source. By measuring the actual temperature experienced by the humidity sensor, the system can compensate for heat transmission effects mathematically, allowing the sensor to be positioned in the protected inner passage environment while maintaining measurement accuracy through temperature-based correction

Inventive Principle:

Principle #24Intermediary (Mediator)

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

This configuration allows for accurate humidity measurement unaffected by heat transmission, reducing measurement errors and maintaining high detection accuracy while minimizing the risk of sensor contamination and structural limitations.

Implementation Method 1

a humidity sensor that outputs an intake air humidity signal in accordance with humidity of the intake air

Methodology Applied

Scientific EffectHumidity sensing: Hygrometer

Implementation Method 2

an intake air temperature sensor that outputs an intake air temperature signal in accordance with temperature of the intake air

Methodology Applied

Scientific EffectTemperature sensing: Thermistor

Implementation Method 3

a flow rate sensor for measuring a flow rate of intake air sucked into an engine

Methodology Applied

Scientific EffectFlow rate detection: Sonic Anemometer

Data Source

PatentUS9964422B2Airflow meter

Publication Date: 2018.05.08 DENSO CORP

AI summary

An airflow meter includes a flow rate sensor for measuring a flow rate of intake air sucked into an engine, a humidity sensor that outputs an intake air humidity signal in accordance with humidity of the intake air, an intake air temperature sensor that outputs an intake air temperature signal in accordance with temperature of the intake air, and a humidity correction section that corrects the intake air humidity signal based on the intake air temperature signal.