Thermal Mass Flow Meter with Modular Sensor Chips

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Solution Overview

Problem

Conventional thermal mass flow meters using MEMS technology are expensive to manufacture and fail to accurately measure flow rates across a wide range due to the correlation between temperature differences and flow rates not being satisfied at higher flow rates.

Innovation Solution

A thermal mass flow meter with a chip-type heat generating element and separately secured chip-type temperature sensors placed at varying distances from the heat generating element, allowing the operation unit to select the appropriate sensors based on flow rate range, and secured using a thermal conductive adhesive, with the option of embedding piping in a substrate for easier attachment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If MEMS technology is used to assemble heat generating element and temperature sensors on a single substrate, then measurement precision is improved, but manufacturing cost increases

Engineering Contradiction:

Improveflow rate measurement precisionVSAvoidmanufacturing cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent divides the measurement system into separate functional modules: a heat generating element and multiple temperature sensors are manufactured as independent components and then assembled on the piping surface. This segmentation eliminates the need for expensive MEMS substrate fabrication while maintaining measurement capability through modular assembly.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses inexpensive chip-type temperature sensors and heat generating elements that can be easily manufactured and replaced, rather than investing in costly MEMS substrate production. These components are secured directly to the piping surface using simple adhesive methods, significantly reducing manufacturing costs while maintaining adequate measurement precision.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Measurement precision

If temperature sensors are placed close to the heat generating element, then measurement precision for low flow rates is improved, but adaptability to high flow rates deteriorates

Engineering Contradiction:

Improvelow flow rate measurement precisionVSAvoidflow rate range adaptability

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent implements a dynamic selection mechanism where the control unit chooses which temperature sensors to activate based on the expected flow rate range. For low flow rates, sensors close to the heat generating element are used for high sensitivity. For high flow rates, sensors positioned further away are activated to maintain measurement accuracy, enabling the system to adapt to varying flow conditions.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent creates a universal measurement system by providing multiple temperature sensors at different positions relative to the heat generating element. This multi-functional arrangement allows the same device to accurately measure both low and high flow rates by selecting appropriate sensors, eliminating the need for separate devices for different flow ranges.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

Enables cost-effective measurement of flow rates across a wider range with high sensitivity, efficient heat transfer, and accurate temperature measurement, avoiding the limitations of MEMS technology costs and sensitivity issues at higher flow rates.

Implementation Method 1

a heat generating element 32 is secured on the surface of a periphery of piping 30 in contact therewith... the fluid inside the piping is heated to a predetermined temperature by the heat generating element 32

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

paired temperature sensors 34 (34a, 34b), which are used for measuring the surface temperature of the piping

Methodology Applied

Scientific EffectThermocouple effect: Thermocouple

Data Source

PatentUS7895888B2Thermal mass flow meter including heating element and temperature sensors formed on separate chips and secured to the outer periphery of the pipe

Publication Date: 2011.03.01 SHIMADZU CORP

AI summary

A heater chip (4) as a heat generation element is secured to the surface on the periphery of piping (2). Further, a temperature sensor chip couple (6) is placed on the surface on the periphery of the piping (2), along the direction of flow of fluid flowing in the piping (2). One (6a) of the sensor chips in the couple is placed on the upstream side of the heater chip (4) and the other (6b) is placed on the downstream side of the heater chip (4). The heater chip (4) and the temperature sensor chips (6a, 6b) are formed in a chip type. The temperature sensor chips (6a, 6b) as the pair are placed at positions spaced by the same distance from the heater chip (4).