JPH0645209Y2 - Semiconductor differential pressure flow meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a differential pressure flow meter for detecting a flow rate by measuring a differential pressure generated above and below a throttle formed in a fluid passage, and particularly to a minute flow rate. The present invention relates to an improvement of a differential pressure flow meter capable of measuring

<Prior Art> Flowmeters for measuring minute flow rates include differential pressure flowmeters, thermal flowmeters, and area flowmeters. Of these, the integral type differential pressure flowmeter in which the orifice and the converter are integrated is commercially available with an orifice hole diameter of about 0.5 mm.

FIG. 3 shows the principle configuration of a conventional known differential pressure flowmeter. 1
Reference numerals 0 and 11 are fluid pipes, and a flange portion 1 is provided on each end face thereof.
2 and 13 are provided. A disk-shaped orifice plate 14 having a circular hole in the center is inserted and fixed between the flange portions 12 and 13.

Then, pressure take-out holes 15 and 16 are formed in the pipe walls upstream and downstream of the fluid pipes 10 and 11 with respect to the orifice plate 14, from which respective pressures are introduced into the differential pressure converter 17 and the difference between them is introduced. The pressure h is measured.

In FIG. 3, the differential pressure transducer is represented by a U-tube type differential pressure transducer for simplicity. However, in practice, for example, both ends are sealed with a diaphragm, and a center diaphragm is arranged in the center. The respective pressures taken out by the differential pressure take-out holes 15 and 16 are applied to the respective diaphragms of the differential pressure detecting section having two chambers filled with this, and the center diaphragm is displaced based on the resulting differential pressure. The displacement of the lever is electrically detected by the conversion unit as a change in capacitance. The detection principle is the same regardless of the size.

However, as a micro flow meter for measuring a micro flow rate, a thermal type flow meter, an area type flow meter, etc. have drawbacks such as insufficient accuracy and troublesome handling. There is no difference in size between small size and large size, so the smaller the differential pressure flowmeter, the larger the size of the conversion part, and the larger the shape and weight of the flowmeter for minute flow. It lacks in simplicity and has the drawback of increasing costs.

Therefore, in order to solve these problems, the present applicant proposes Japanese Utility Model Application No. 62-153035, "Name of device: differential pressure flowmeter". FIG. 4 is a perspective view showing the configuration of the differential pressure flowmeter proposed in this application, and the outline thereof will be described based on this.

Reference numeral 18 is a silicon substrate having a rectangular outer shape, and the inside thereof is etched into a U-shaped recess in the cross section in the longitudinal direction, and this recess 19 forms a part of the fluid passage 20, and the remaining part is The legs 21 and 22 are formed. Also a silicon substrate
An orifice plate 23 is integrally formed at the center of the recess 19 of the eighteenth portion in the longitudinal direction so as to narrow a part of the fluid passage and intersect the fluid passage at a right angle.

Piezoresistive elements 24 and 25 are formed on the outer surface of the silicon substrate 18 in the vicinity of the orifice plate 23 and upstream and downstream thereof by a semiconductor technique such as diffusion.

Reference numeral 26 is a silicon substrate having a rectangular outer shape, and the inside thereof is etched into a U-shaped recess in the cross section in the longitudinal direction, and this recess 27 forms a part of the fluid passage 20. The legs 28 and 29 are formed. Also a silicon substrate
An orifice plate 30 is integrally formed at the central portion of the recess 27 of the recess 26 in the longitudinal direction so as to narrow a part of the fluid passage and intersect the fluid passage at a right angle.

31 and 32 are rectangular glass plates, and the leg portions 21 (22) of the silicon substrate 18 and the leg portions 28 (29) of the silicon substrate 26 are mutually connected via the glass plate 31 (32) by, for example, anodic bonding. And a fluid passage 20 for flowing the flow rate Q of the measurement fluid.

The fluid passages 20, the orifice plates 23, 30 and the like are all formed by anisotropic etching of silicon, and as a result, the orifice plates 23 and 30 form a diaphragm 33.

Next, the operation of the differential pressure flowmeter configured as described above will be described.

When the flow rate Q of the measurement fluid flows into the fluid passage 20, the flow rate Q is throttled by the throttle 33 which is constituted by the orifice 23 and 30, the pressure loss ΔP = aρV ^2/2 (a by the diaphragm 33 is a constant, [rho: fluid Density, V: flow velocity), but the piezoresistive elements 25 and 24 output V ₁ and V ₂ by the stress due to slight deformation from the fluid passage 20 due to the forces F ₁ and F ₂ from the flow rate Q. This output V _1, V ₂ can be expressed by _{V 1 -V 2 αF 1 -F 2} αΔP = aρV 2/2 ... (1), the flow velocity V Vα [2 (V ₁ -V ₂ ) / (aρ)] ^1/2 (2)

Therefore, by using the outputs V ₁ and V ₂ of the piezo-resistive elements 25 and 24, it is possible to easily perform the operation of multiplying the equation (2) and the cross-sectional area by an operation circuit (not shown) formed by semiconductor technology, for example. The flow rate of the measuring fluid can be obtained.

<Problems to be solved by the invention> However, the differential pressure flowmeter for measuring a minute flow rate proposed in this application is a fluid in the piezoresistive elements 25, 24 arranged on the upstream side and the downstream side of the orifice plate 23. Since the flow rate signal is calculated by calculating the difference between the signals caused by the distortion caused by the pressure, an error occurs if the characteristics of the piezoresistive elements 24, 25 do not match, and the strength against the fluid pressure is increased. In that case, the thickness of the silicon substrate 18 must be increased, and if it is increased, the sensitivity is lowered. Conversely, if the thickness of the silicon substrate 18 is decreased to increase the sensitivity, the pressure resistance against the fluid pressure is reduced. There was a problem that either sacrifices either strength or strength.

The present invention provides a differential pressure flowmeter capable of increasing the pressure resistance to the fluid pressure and also improving the sensitivity, further improving the differential pressure detection, that is, the accuracy of the flow rate output, and further reducing the minute flow rate. It is an object of the present invention to provide a semiconductor differential pressure flow meter capable of measuring.

<Means for Solving the Problems> In order to achieve this object, in the semiconductor differential pressure flowmeter of the present invention, one surface of the first substrate is hermetically bonded to one surface of the first substrate with a predetermined space therebetween. A second substrate that forms a vacant chamber and a third substrate that forms a fluid passage by sealingly bonding the first substrate to the other surface of the first substrate at a predetermined distance. , The first substrate is provided with an orifice formed so as to project toward the fluid passage side of the first substrate so as to be a resistance to the flow of the measurement fluid, and an upstream side of the orifice of the first substrate. A pressure guide hole that is integrally formed to connect the previous chamber and the previous fluid passage, and a fluid pressure of the previous chamber that is formed on the previous first substrate in the vicinity of the downstream side of the original orifice. And a differential pressure detection unit for detecting the differential pressure with the fluid pressure on the downstream side of the orifice using a semiconductor piezoresistive gauge. The first, second, and third substrates are made of silicon or glass, and the differential pressure signal detected by the differential pressure detector is used to determine the flow rate of the measured fluid flowing through the fluid passage. It is designed to be output by calculation.

<Operation> Since the fluid pressure is applied to both the vacant chamber side and the fluid passage side by the differential pressure detection unit formed on the first substrate, the flow rate detection sensitivity can be set arbitrarily.

Further, the fluid passage can be formed to have a thickness that has a required strength regardless of the flow rate detection sensitivity.

Further, since the differential pressure is detected by the same piezoresistive gauge, the error in differential pressure detection can be reduced.

<Embodiment> An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 1 (a) is a perspective view showing the overall construction of the semiconductor differential pressure flowmeter of the present invention, and FIG. 1 (b) is a longitudinal sectional view showing a cross section taken along the line A-A 'in (a). FIG. 1 (c) is a surface view showing the fluid passage as viewed from the direction of arrow BB 'in (a).

Reference numeral 34 denotes a silicon substrate having a rectangular outer shape, and a glass substrate 35 having a rectangular outer shape on the upper side and a glass substrate 36 having a rectangular outer shape on the lower side are hermetically bonded by, for example, anodic bonding. There is.

A groove 38 forming a part of a U-shaped fluid passage 37 is formed at a predetermined depth in the center of the inner surface of the substrate 36 in the longitudinal direction.

In addition, a rectangular vacant chamber 39 is formed on the inner surface of the substrate 35 with a predetermined depth.

The substrate 36 side of the substrate 34 constitutes a part of the fluid passage 37,
Orifice 40 facing the groove 38 and serving as a resistance against the flow of the fluid Q
Are formed by a semiconductor technique such as anisotropic etching. In addition, a fluid passage 37 is provided in front of the orifice 40.
And a pressure guiding hole 41 communicating with the vacant chamber 39 are formed by anisotropic etching. Further, a part of the substrate 34 facing the groove 37 on the downstream side of the orifice 40 is made into a thin strained portion 42 by anisotropic etching, and a part of this strained portion 42 is provided with a piezoresistive gauge.
43 is formed by, for example, diffusion. Strain element 42,
The differential pressure detection unit 44 is formed by the piezo resistance gauge 43 and the like.

In addition, as shown in FIG. 1 (c), the pressure guide hole 41, the orifice
The periphery of 40 and the strain-flexing part 42 is tapered because the silicon substrate is used when these are formed by anisotropic etching.
This is because the etching rate differs depending on the relationship with the crystal plane of 34.

Next, the operation of the embodiment configured as described above will be described. When the fluid Q to be measured flows in from the left end of the fluid passage 37, the fluid Q is throttled by the orifice 40 and a pressure difference ΔP is generated between the upstream side and the downstream side of the orifice 40. This pressure difference ΔP has a predetermined relationship with the flow rate Q, and the thin strain element 42 is displaced so as to correspond to the flow rate Q.

The displacement of the strain-flexing portion 42 is converted into an electric signal corresponding to the flow rate Q by a resistance change thereof by a conversion portion (not shown). This conversion unit may be formed integrally with the substrate 34 by a semiconductor technique such as diffusion, or may be separately formed.

FIG. 2 is a vertical sectional view showing the construction of the second embodiment of the present invention. This cross section corresponds to FIG.

45 is a glass substrate having a rectangular outer diameter, a silicon substrate 46 having a rectangular outer diameter on the upper portion, and a silicon substrate 47 having a rectangular outer diameter on the lower side is hermetically bonded by, for example, anodic bonding or the like. Has been done.

The substrates 46 and 47 have basically the same shape as the substrates 35 and 36 in FIG. 1 except for the material.

A groove 49 forming a part of a U-shaped fluid passage 48 is formed at a predetermined depth in the center of the inner surface of the substrate 47 in the longitudinal direction.

In addition, a rectangular empty chamber 50 is formed at a predetermined depth on the inner surface of the substrate 46.

The substrate 47 side of the substrate 45 constitutes a part of the fluid passage 48,
Orifice 51 facing the groove 49 and serving as a resistance against the flow of the fluid Q
Are formed. Further, in front of the orifice 51, a pressure guide hole 52 that connects the fluid passage 48 and the empty chamber 50 is formed.
Through holes 53 penetrating the substrate 45 are formed behind them.

A silicon differential pressure detection unit 54 is bonded to the substrate 45 by anodic bonding or the like so as to cover the through hole 53.

The differential pressure detection unit 54 is, for example, a circular strain generating unit 56 in which a central part of a silicon chip 55 made of, for example, a rectangular silicon single crystal is thinned by anisotropic etching or the like, and a piezoresistive gauge is provided on the upper surface. 57 is formed by, for example, diffusion.

Therefore, the differential pressure generated in the orifice 51 is applied to both surfaces of the strain-flexing portion 56. The signal processing after the differential pressure is detected is the same as that shown in FIG.

<Advantages of Device> As described above in detail with reference to the embodiments, according to the present invention, (a) the strain of the differential pressure detecting unit related to the thickness of the fluid passage related to the pressure resistance against the fluid pressure and the detection sensitivity. It is possible to realize a highly sensitive and high withstand pressure differential pressure flowmeter, because the thickness of the part can be determined separately, and (b) Moreover, these are integrated by semiconductor technology without using metal. Since it can be formed into a small size, it is possible to reduce the size and weight, and to measure a minute flow rate. (C) In addition, since the differential pressure detection part is formed integrally with the orifice, there is no need for an overpressure protection mechanism. (D) Moreover, since only one differential pressure detecting unit is used, there is no error due to variations in characteristics between the differential pressure detecting units, and high accuracy can be expected.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing the configuration of one embodiment of the present invention, FIG. 2 is a vertical sectional view showing the configuration of the second embodiment of the present invention, and FIG. 3 is a conventional known differential pressure flowmeter. Fourth longitudinal sectional view showing the configuration
FIG. 1 is a perspective view showing a configuration of a semiconductor differential pressure flowmeter according to a conventional prior application. 10, 11 …… Fluid line, 14 …… Olyphus plate, 17 …… Differential pressure transducer, 18 …… Silicon substrate, 20 …… Fluid passage, 23 ……
Orifice plate, 24, 25 ... Piezoresistive element, 26 ... Silicon substrate, 30 ... Orifice plate, 34, 35, 36 ... Substrate,
37 ... Fluid passage, 39 ... Vacancy, 40 ... Orifice, 41 ...
… Pressure guiding hole, 42 …… Strain element, 43 …… Piezo resistance gauge, 44
...... Differential pressure detection part, 45, 46, 47 …… Substrate, 48 …… Fluid passage, 50 …… Vacancy, 51 …… Olifis, 52 …… Pressure guide hole, 53
...... Through hole, 54 ...... Differential pressure detection part, 57 ...... Piezo resistance gauge.

Claims (1)

[Scope of utility model registration request] 1. A second substrate which is hermetically bonded to one surface of a first substrate at a predetermined interval to form a vacant chamber, and the other surface of the first substrate is provided with the second substrate. A first substrate; and a third substrate that is hermetically joined to form a fluid passage at a predetermined interval, and the first substrate is the fluid of the first substrate so as to be a resistance to the flow of the measurement fluid. An orifice formed to protrude toward the passage, a pressure guide hole integrally formed on the upstream side of the orifice of the first substrate and connecting the chamber and the fluid passage, and a proximity to a downstream side of the orifice. And a differential pressure detecting section formed on the first substrate for detecting a differential pressure between the fluid pressure in the chamber and the fluid pressure on the downstream side of the orifice using a semiconductor piezoresistive gauge. The 1st, 2nd and 3rd substrates are made of silicon or glass. A semiconductor differential pressure flowmeter, wherein a flow rate of the measurement fluid flowing through the fluid passage is calculated and output using a differential pressure signal detected at an outlet.