JPH09113325A - Semiconductor flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To calculate the flow rate easily based on a pressure variation detected by a detection element by disposing a substrate oppositely to a pressure receiving diaphragm covering a notch in the wall of a measuring duct on the outside thereof, mounting a semiconductor pressure detection element covered with an elastic cover on the substrate and coupling the cover with the diaphragm through a transmission rod. SOLUTION: A pressure receiving diaphragm 22 is provided covering a notch 21 made in the wall of a measuring duct 11. A substrate 23 disposed oppositely thereto on the outside of duct 11 is secured by means of a screw 25 to the duct wall through a cover 24 and a sealing body 26. A silicon semiconductor pressure detection element 27 is mounted on the substrate 23 while being covered with a covering body 28 of silicon resin and the diaphragm 22 is coupled with the covering body 28 through a transmission rod 29. The diaphragm 22 is displaced by the pressure variation caused by variation in the flow rate of measuring fluid 13 and the pressure variation is transmitted through the transmission rod 29 and covering body 28 to the element 27. Output signal from the element 27 is processed by a processing circuit 31 thus determining the flow rate of fluid 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inexpensive semiconductor flowmeter which can easily measure a small flow rate with a simple structure.

[0002]

2. Description of the Related Art Conventionally, for measuring a small flow rate, for example, the book title "Basics and Applications of Instrumentation Systems", edited by Ken Shimoto and Futana Hanabuchi
The volume flow meter shown in P95, the turbine flow meter shown in P98, and the float type area flow meter shown in P93 have been used.

[0003]

However, in such a device, the former two are mainly for industrial use and have high precision, but have the drawbacks of complicated structure and high cost. The float type area flow meter is inexpensive, but it has the drawback that it must be used vertically and the mounting posture is limited. The present invention solves this problem.

An object of the present invention is to provide an inexpensive semiconductor flowmeter which can easily measure a small flow rate with a simple structure.

[0005]

In order to achieve this object, the present invention provides (1) a semiconductor flowmeter in which a flow rate detector is provided on a pipe wall of a measurement pipe line. A notch provided in the wall, a pressure receiving diaphragm provided so as to cover the notch, a substrate provided outside the measurement pipe line facing the pressure receiving diaphragm, and a silicon provided on the substrate. A semiconductor pressure detecting element, an elastic coating provided to cover the silicon semiconductor pressure detecting element, a transmission rod connecting the coating and the pressure receiving diaphragm, and a pressure change of the silicon semiconductor pressure detecting element. A semiconductor flow meter, comprising: an arithmetic circuit for calculating a flow rate from a corresponding electric signal. (2) The semiconductor flowmeter according to claim 1, wherein the piezoresistive element formed on the silicon semiconductor pressure detecting element is a shear type gauge. It is what constituted.

[0006]

In the above structure, the pressure receiving diaphragm is displaced by the pressure change due to the change in the flow rate of the measurement fluid. The transmission rod is displaced based on the displacement of the pressure receiving diaphragm, and the pressure change is transmitted to the silicon semiconductor pressure detection element via the cover. This pressure change is converted into an electric signal by the silicon semiconductor pressure detection element, and the flow rate of the measurement fluid is calculated by the calculation circuit. Hereinafter, detailed description will be given based on examples.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a structural explanatory view of an example of use of the device of the present invention, FIG. 2 is a structural explanatory view of a main part of one embodiment of the present invention, FIG. 3 is an operational explanatory diagram of FIG. 2, and FIG. It is a top view of FIG.

In FIG. 2, reference numeral 11 is a measuring pipe line, and 12 is a semiconductor flowmeter of the present invention provided on the pipe wall of the measuring pipe line 11. Measuring line 11 to which the flow detector part 12 is attached
In this case, the pipe wall portion of the pipe line 11 is narrowed,
It is configured to be smaller than the cross-sectional area of the measurement pipe line 11 before and after that.

Reference numeral 13 is a measurement fluid. The measurement fluid 13 may be gas or liquid. In FIG. 1, reference numeral 21 denotes a measuring pipe line 1.
It is a notch provided in the pipe wall of No. 1. Reference numeral 22 is a pressure receiving diaphragm provided so as to cover the cutout portion 21. The pressure receiving diaphragm 22 is an elastic body such as rubber, or
A metal is used and is selected according to the type of measurement fluid.

Reference numeral 23 is a substrate which is provided outside the measurement pipe line so as to face the pressure receiving diaphragm 22. In this case, the base plate 23 is screwed to the pipe wall of the measuring pipe line 11 by means of the lid 24. 26 is a substrate 23 and a measurement conduit 11
It is a sealing body that seals the gap between the tube wall and the tube wall.

Reference numeral 27 is a silicon semiconductor pressure detecting element provided on the substrate 23. The silicon semiconductor pressure detecting element 27 includes a sensor chip 271 made of a semiconductor and a recess 27 for forming a diaphragm 272 on the sensor chip 271.
3 and the strain detection sensor 2 provided on the diaphragm 272.
74. In this case, shear gauges are used.

28 is a silicon semiconductor pressure detecting element 27.
Is a covering body having elasticity and covering the. In this case, silicone resin is used. Reference numeral 29 is a transmission rod that connects the covering body 28 and the pressure receiving diaphragm 22.

31 is a silicon semiconductor pressure detecting element 27.
Is a calculation circuit that calculates a flow rate from an electric signal corresponding to the pressure change. 41 is a pressure guide hole provided in the substrate 23,
Reference numeral 2 is a pressure guide hole provided in the lid 24.

In the above structure, the pressure receiving diaphragm 22 is displaced by the pressure change due to the change in the flow rate of the measurement fluid 13. Based on the displacement of the pressure receiving diaphragm 22, the transmission rod 2
9 is displaced, and the pressure change is transmitted to the silicon semiconductor pressure detection element 27 via the cover 28.

This pressure change is converted into an electric signal by the silicon semiconductor pressure detecting element 27, and the flow rate of the measurement fluid is calculated by the arithmetic circuit 31.

That is, in FIGS. 3 and 4, the pressure of the measurement fluid 13 at the location where the flow rate detector portion 12 is attached is P, the flow rate is Q, the flow velocity is V, the fluid density is ρ, and the cross-sectional area is S. Then, from Bernoulli's theorem,

P + K ₁ (1/2) ρV ² = C ₁ K ₁ , C: constant ∴P = C ₁ -K ₁ (1/2) ρV ² Therefore, the pressure (static pressure) at the flow detector portion 12 is ) P is
It decreases in proportion to the square of the flow velocity V.

From the flow rate Q = VS ∴Q = S (C ₂ -((2P) / (K ₁ ρ))) ^1/2 Therefore, the flow rate Q is obtained.

Since the change in the pressure P of the measuring fluid 13 increases as the flow velocity V increases, in this case, the cross-sectional area S of the portion of the flow rate detector portion 12 is narrowed as shown in FIG.

Next, the results of studies on specific examples are shown below. When the measurement fluid 13 is water and the flow velocity is 1 m / s. 0m
Since the pressure change ΔP from / s is ρ = 102 kg · s ² / m ⁴ , ΔP≈1 / 2ρV ² ≈ (1/2) × 102 × 1 ² = 51 × 10 ⁻⁴ kgf / cm ² = 51 mmH ₂ O

When the area of the pressure receiving diaphragm 22 is A ₁ and the cross-sectional area of the transmission rod 29 is A ₂ , the pressure P ₁ applied to the silicon semiconductor pressure detecting element 27 is given by the following equation. P ₁ = (A ₁ / A ₂ ) P

Now, the diameter D ₁ of the pressure receiving diaphragm 22 is 1
0 mm and the diameter D ₂ of the transmission rod 29 = 2 mm, A ₁ /
A ₂ = 25 P ₁ ≈25 × 50 = 1250 mmH ₂ O This P ₁ can be actually and sufficiently detected by the silicon semiconductor pressure detection element 27.

As a result, (1) the main part is the notch 21 and the pressure receiving diaphragm 2
2, a silicon semiconductor pressure detection element 27, and a cover 28
And the transmission rod 29, the device can be downsized and an inexpensive semiconductor flowmeter can be obtained.

(2) Since the detecting portion is provided outside the measuring pipe line 11, a semiconductor flowmeter with extremely small pressure loss can be obtained. (3) The measurement fluid can be a liquid or a gas,
A semiconductor flowmeter with a wide measurement range can be obtained.

(4) Silicon semiconductor pressure detecting element 27
Is covered directly with the covering body 28, so that a semiconductor flowmeter having a good anti-contamination atmosphere characteristic can be obtained. (5) Transmission rod 29 based on displacement of pressure receiving diaphragm 22
Is displaced and the pressure change is transmitted to the silicon semiconductor pressure detecting element 27 through the cover 28, so that the cover 28
Then, the force is dispersed and applied to the silicon semiconductor pressure detecting element 27 as a whole, so that the pressure change is surely transmitted to the silicon semiconductor pressure detecting element 27.

(6) If the piezoresistive element formed on the silicon semiconductor pressure detecting element 27 is a shear type gauge, a semiconductor flowmeter with improved sensitivity can be obtained. It should be noted that, in the above-mentioned embodiment, the cover 28 is described as being made of silicon, but the present invention is not limited to this. In short, any material that has elasticity and can transmit force may be used.
Further, it goes without saying that the covering body 28 may be formed by laminating several kinds of resins in multiple layers.

[0027]

As explained in detail above, the present invention provides:
According to claim 1, (1) since the main part is composed of the notch, the pressure receiving diaphragm, the silicon semiconductor pressure detecting element, the cover, and the transmission rod, the device can be downsized and inexpensive. A semiconductor flowmeter is obtained.

(2) Since the detecting portion is provided outside the measuring pipe line, a semiconductor flowmeter with extremely small pressure loss can be obtained. (3) The measurement fluid can be a liquid or a gas,
A semiconductor flowmeter with a wide measurement range can be obtained.

(4) Since the silicon semiconductor pressure detecting element is directly covered with the covering body, a semiconductor flowmeter having a good anti-contamination atmosphere characteristic can be obtained. (5) Based on the displacement of the pressure-receiving diaphragm, the transmission rod is displaced, and the pressure change is transmitted to the silicon semiconductor pressure detecting element through the cover, so that the force is dispersed in the cover and the silicon as a whole is dispersed. Since the pressure change is applied to the semiconductor pressure detecting element, the pressure change is surely transmitted to the silicon semiconductor pressure detecting element.

According to the second aspect, it is possible to obtain a semiconductor flowmeter with improved sensitivity.

Therefore, according to the present invention, it is possible to obtain an inexpensive semiconductor flow meter which can easily measure a small flow rate with a simple structure.

[Brief description of the drawings]

FIG. 1 is a configuration explanatory view of a usage example of the device of the present invention.

FIG. 2 is an explanatory diagram of a main part configuration of an embodiment of the present invention.

FIG. 3 is an operation explanatory diagram of FIG. 2;

FIG. 4 is a plan view of FIG. 1;

[Explanation of symbols]

 11 Measuring Pipe Line 12 Flow Rate Detector Part 13 Measuring Fluid 21 Notch Part 22 Pressure Receiving Diaphragm 23 Substrate 24 Lid 25 Screw 26 Sealing Body 27 Silicon Semiconductor Pressure Sensing Element 271 Sensor Chip 272 Diaphragm 273 Recess 274 Strain Sensing Sensor 28 Covering Body 29 Transmission Rod 31 Arithmetic circuit 41 Pressure hole 42 Pressure hole

Claims (2)

[Claims] 1. A semiconductor flowmeter in which a flow rate detector is provided on a pipe wall of a measurement pipe line, the cutout portion being provided on the pipe wall of the measurement pipe line, and the cutout portion being provided so as to cover the cutout portion. A pressure-receiving diaphragm, a substrate provided outside the measurement conduit to face the pressure-receiving diaphragm, a silicon semiconductor pressure detecting element provided on the substrate, and an elasticity provided to cover the silicon semiconductor pressure detecting element. And a transmission rod connecting the coating and the pressure-receiving diaphragm, and an arithmetic circuit for calculating a flow rate from an electric signal corresponding to a pressure change of the silicon semiconductor pressure detection element. A semiconductor flow meter. 2. The semiconductor flowmeter according to claim 1, wherein the piezoresistive element formed on the silicon semiconductor pressure detecting element is a shear type gauge.