Semiconductor Flow Sensor with Upstream Humidity Compensation

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Solution Overview

Problem

Semiconductor devices for detecting fluid flow rates are prone to errors due to moisture content, particularly in applications requiring high precision, such as fuel injection control in internal combustion engines, where existing technologies fail to accurately compensate for humidity.

Innovation Solution

Incorporating a humidity sensor on the same semiconductor substrate as the flow sensor, positioned upstream of the heater, to compensate for moisture and improve detection accuracy, while minimizing device dimensions and reducing heat interference from the heater.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a flow sensor with a heater is used to detect fluid flow rate, then flow rate detection is enabled, but moisture content in the fluid causes detection errors

Engineering Contradiction:

Improveflow rate detection accuracyVSAvoiddetection accuracy affected by moisture

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent combines the flow sensor and humidity sensor into a single integrated device on the same semiconductor substrate. The flow sensor includes a heater and temperature sensing elements, while the humidity sensor uses a hygroscopic film and electrodes. This merging allows simultaneous measurement of both flow rate and humidity, enabling compensation for moisture content in the fluid to improve flow rate detection accuracy.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent implements a feedback mechanism where the humidity sensor continuously monitors the moisture content in the fluid, and this humidity information is used to compensate for detection errors in the flow sensor. The system uses the measured humidity data to correct the flow rate measurements, creating a closed-loop compensation system that improves overall measurement reliability.

Inventive Principle:

Principle #23Feedback

2Measurement precision

If the humidity sensor is placed close to the flow sensor, then humidity near the flow sensor is detected improving accuracy, but heat from the heater may affect the humidity sensor

Engineering Contradiction:

Improvehumidity detection accuracyVSAvoidheat interference from heater

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by creating a dedicated humidity sensing region with specific thermal characteristics. The humidity sensor is positioned in a location that allows close proximity to the flow sensor for accurate local humidity measurement, while the substrate structure and spacing are designed to provide thermal isolation in that specific local area, protecting the humidity sensor from heater heat while maintaining measurement accuracy.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The semiconductor substrate acts as an intermediary between the heater and the humidity sensor. By carefully designing the substrate thickness, material properties, and spatial arrangement, the substrate serves as a thermal buffer that allows the humidity sensor to detect humidity accurately while being protected from excessive heat from the heater, thus mediating the thermal interaction between these two components.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Volume of moving object

If the flow sensor and humidity sensor are integrated on the same substrate, then device dimensions are minimized, but layout space for both sensors is constrained

Engineering Contradiction:

Improvedevice dimensionsVSAvoidsensor layout arrangement

Core Design Contradiction:

Volume of moving objectVSDevice complexity

Solution Approach 1:

The patent utilizes three-dimensional space effectively by arranging the flow sensor and humidity sensor in different spatial dimensions on the substrate. The sensors are positioned at different locations and orientations, with the humidity sensor placed in a region that optimizes both proximity to the flow sensor for measurement accuracy and sufficient spacing to minimize thermal interference, thereby managing layout complexity while maintaining compact dimensions.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 the detection accuracy of fluid flow rates by compensating for moisture content and maintaining precision despite heat generated by the heater, making it suitable for high-precision applications like fuel injection control.

Implementation Method 1

a first heater for detecting a flow rate of fluid

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

a temperature sensing element for sensing temperature of a portion around the heating element

Methodology Applied

Scientific EffectTemperature sensing:

Implementation Method 3

a humidity sensor for detecting a humidity of the fluid

Methodology Applied

Scientific EffectHumidity sensing:

Data Source

PatentUS7640798B2Semiconductor device for detecting flow rate of fluid

Publication Date: 2010.01.05 DENSO CORP

AI summary

A semiconductor device includes: a semiconductor substrate; a flow sensor having a first heater for detecting a flow rate of fluid; and a humidity sensor for detecting a humidity of the fluid. The flow sensor and the humidity sensor are disposed on the semiconductor substrate. The flow sensor is disposed around the humidity sensor. The humidity sensor is disposed on an upstream side of the first heater. Since the device includes the humidity sensor, moisture in the fluid is compensated so that detection accuracy of the flow rate is improved.