JPH06230021A - Thermosensible currentmenter and fluidic flow meter using it - Google Patents

Abstract

PURPOSE:To enable zero correction while keeping high heat radiation efficiency per unit charged electric power, and improve the measuring accuracy of flow speed extending over the whole flow range. CONSTITUTION:Upper and lower stream side beam temperature detectors Ru, Rd are formed on the upper and lower stream side of a same beam 3 as auxiliary temperature detectors, and as for a main temperature detector Rs and a fluid temperature detector Rf, a first electric bridge circuit 8 is formed together with a balance adjusting resistor so as to make variable heating electric power given to a heating element Rh for making constant the temperature difference between the heating element Rh and the fluid temperature detector Rf. As for the upper and lower stream side beam temperature detectors Ru, Rd, a second electric bridge circuit 9 is formed together with another balance adjusting resistor, so as to enable to detect micro-flow and a no flow condition. Outputs f1, f2 of the first and second bridge electric circuits 8, 9 are held with a digital memory computing circuit 11 and computation processing to search flow velocity following to zero correction is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosensitive anemometer for measuring the velocity of a fluid such as a gas or a liquid, and a fluidic flowmeter using the same.

[0002]

2. Description of the Related Art There have been various types of velocity meters of this type, and one of them is a heat sensitive type. There are various thermosensitive anemometers, but the basis is
The heating resistor is installed in the fluid, the change in the amount of heat taken by the fluid from the amount of heat generated by the heating resistor is detected, and the flow velocity of the fluid is measured.

As a concrete example, for example, JP-A-60-142.
As disclosed in Japanese Patent Laid-Open No. 268 and Japanese Patent Laid-Open No. 61-235726, a moat is formed on a part of a Si substrate by using an anisotropic etching technique, and a beam is passed across the moat. There is a heat-sensitive part formed on the beam to reduce the heat capacity of the heat-sensitive part and reduce heat loss to the substrate and the substrate support part. According to this, it is possible to reduce the input power required for heat generation and temperature measurement.

Here, in the first conventional construction, the temperature difference between the fluid and the beam is made constant, the two beams are heated with the same electric power, and the upstream and downstream sides of the beam are generated due to the imbalance of heat radiation to the fluid. A method of measuring the flow velocity by detecting the temperature difference is adopted.
In this method, when there is no flow, there is no temperature difference, so the output is always zero at the zero flow rate point. Further, in the second conventional configuration, there is a method of measuring the flow velocity by heating only one beam and detecting the electric power supplied to the heating element to make the temperature difference between the beam and the fluid constant as an output. To be taken.

Further, as a flow meter for measuring the flow rate of a fluid such as gas or liquid, there is a fluidic flow meter having a structure as disclosed in Japanese Patent Laid-Open No. 59-68624.

[0006]

However, in the first configuration example in which there are two beams, the heating element is separated from the upstream side and the downstream side so that the heating element extends over the two beams and approaches the cut line that separates the two beams. To arrange. For this reason, the temperature of the upstream temperature measuring element and the temperature of the downstream temperature measuring element are lower than the temperature of the heating element when there is no flow and the temperature of the upstream temperature measuring element is lower than the temperature of the heating element when there is a flow (wind). The temperature becomes lower and the temperature of the downstream temperature sensing element becomes higher. For this reason, in the flow direction, the temperature difference in the cross section of the beam is significant, and the effective heat dissipation area becomes very small.

On the other hand, in the second configuration example in which the number of beams is one, the entire beam is heated uniformly, so that the heat radiation area becomes large. Regarding the heat radiation efficiency, which is a characteristic greatly related to the flow velocity sensitivity, in consideration of the fact that it is preferable that the beam temperature is uniformly high, especially the temperature on the upstream side is high, the first and second heat radiation areas having the same heat radiation area are provided. Comparing the two configurations, the heat radiation efficiency per unit input power is better in the second configuration example, and the flow velocity detection sensitivity in the first configuration example is about one digit lower than that in the second configuration example. However, in the second configuration example, fluid temperature, room temperature fluctuation,
Long-term fluctuations with a certain range in output may occur due to natural convection changes. For this reason, it becomes unclear whether the flow rate was zero at the time of output, and the measurement speed deteriorates in the entire flow rate range.

On the other hand, when the fluidic flowmeter is used for a household gas meter, for example, it is necessary to measure a flow rate of 3 to 3000 liters per hour.
In the conventional fluidic flowmeter as disclosed in Japanese Patent No. 24, the fluidic vibration does not occur in the low flow rate region of about 3 to 300 liters per hour, and the flow rate cannot be detected.

[0009]

According to a first aspect of the present invention, a substrate, a moat formed by anisotropic etching on a part of the substrate, a beam formed across the moat, and an electric resistance. A heat-sensing part formed on the beam with a body heating element and a temperature sensing element that is integrated with or separate from the heating element to measure the temperature of the heating element, and does not overlap the heating element and the temperature sensing element. An upstream beam temperature measuring element formed by an electric resistor formed on the upstream side of the beam, and having the same length in parallel with the upstream beam temperature measuring element without overlapping the heating element and the temperature measuring element; A downstream side beam temperature measuring body having an electric resistance formed with the same width on the upstream side and the downstream side of the beam; a fluid temperature measuring body arranged on the substrate or outside the substrate to measure a fluid temperature; The heating element and the fluid are formed by a heating element, a fluid temperature measuring element, and a balance adjusting resistor. A first electric bridge circuit for varying the heating power applied to the heating element to keep the temperature difference from the temperature measuring element constant, the upstream beam temperature measuring element and the downstream beam temperature measuring element. A second electric bridge circuit formed by a warm body and another balance adjusting resistor, and a digital memory arithmetic circuit that holds the outputs of these first and second electric bridge circuits and performs arithmetic processing for obtaining a flow velocity Composed by and.

In this case, according to the second aspect of the invention, the beam is
A central beam portion where a heating element and a temperature measuring element are formed, and a small area upstream beam where an upstream beam temperature measuring element is formed by connecting a plurality of auxiliary thin bridges to the central beam portion. Part and a downstream beam part having a small area connected to the central beam part by a plurality of auxiliary thin bridges to form a downstream beam temperature measuring element.

In the invention according to claim 3, the first and second aspects are provided.
The reference data and calculation program for holding the output of the electric bridge circuit and correcting the zero point of the relationship between the flow velocity and the heating element output to obtain the flow velocity when the flow velocity is within the range of zero or near zero are combined. Embedded ROM and RA
5. A digital memory arithmetic circuit having an M circuit,
In the described invention, the reference data and the calculation program for holding the outputs of the first and second electric bridge circuits and performing the calculation process for sequentially obtaining the flow velocity by performing the zero point correction of the relationship between the flow velocity and the heating element output are incorporated. The digital memory arithmetic circuit has a ROM and a RAM circuit.

According to the invention of claim 5, the substrate of the thermal velocity meter of claim 1, 2, 3 or 4 is provided at any position of the center of the nozzle of the fluidic vibrator, the lower part of the inner wall of the nozzle or the ceiling part. It was a fluidic flow meter.

[0013]

According to the first aspect of the present invention, an upstream beam temperature measuring element and a downstream beam temperature measuring element are formed as preliminary temperature measuring elements on the upstream side and the downstream side on the same beam, and the main temperature measuring elements are formed. As for the heating element and the fluid temperature measuring element side, the first electric bridge circuit is formed together with the balance adjusting resistor to provide the heating element with a constant temperature difference between the heating element and the fluid temperature measuring element. The heating power to be generated is made variable, and a second electric bridge circuit is formed together with other balance adjusting resistors for the upstream beam temperature measuring element and the downstream beam temperature measuring element to form a minute flow and flow. As a device capable of detecting a state in which there is no voltage, the digital memory arithmetic circuit holds the outputs of these first and second electric bridge circuits and performs arithmetic processing for obtaining the flow velocity, so that the voltage drop output of the heating element, which is the main output. Room temperature change, fluid temperature change Will be capable of sequentially detecting a variation width due factors such as natural convection, while maintaining the heat dissipation effect of the high per unit input power, it is possible to perform so-called zero-point correction, becomes good flow rate measurement accuracy.

In particular, according to the second aspect of the invention, the beam portion forming the upstream side beam temperature measuring element or the downstream side beam temperature measuring element is used as an upstream side beam portion or a downstream side beam portion having a small area. It is formed by dividing it from the central beam part that forms the main part, and it is connected to the central beam part with an auxiliary thin bridge, so the zero point detection accuracy is improved while maintaining the heat dissipation characteristics of the central beam part. It will be done.

Further, in the invention according to claim 3, as a digital memory arithmetic circuit having a ROM and a RAM circuit in which predetermined reference data and an arithmetic program are incorporated,
Since the zero point correction of the relationship between the flow velocity and the output of the heating element is performed at any time to calculate the flow velocity, the flow velocity detection accuracy is improved. Similarly, in the invention according to claim 4, a ROM and an RA in which predetermined reference data and a calculation program are incorporated.
As a digital memory arithmetic circuit having M circuits,
Since the zero point correction of the relationship between the flow velocity and the output of the heating element is performed to calculate the flow velocity, the flow velocity detection accuracy is improved.

Further, in the invention according to claim 5,
Since the substrate of the thermosensitive anemometer with improved heat dissipation efficiency is provided at any of the center of the nozzle of the fluidic oscillator of the fluidic flowmeter, the lower part of the inner wall of the nozzle, or the ceiling, low flow rate measurement is possible. Can be performed accurately with low power.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. The present embodiment corresponds to the invention described in claims 1 and 3. First, as a basic configuration of this embodiment, Si
The central portion of the rectangular substrate 1 made of (silicon) has a shape that promotes fluid intrusion, that is, a flat hexagonal moat when viewed in plan when the flow direction of the fluid is diagonal. 2 is formed, and a beam 3 is formed so as to straddle the vicinity of the central portion of this moat 2.
Are formed. Here, the moat 2 and the beam 3 are formed by the anisotropic etching technique of the substrate 1. Further, a heating element Rh made of an electric resistor and a temperature measuring element Rs made of an electric resistor are formed on the beam 3 in a mutually intricate pattern, and are drawn out onto the substrate 1 outside the beam 3. There is. The heating element Rh and the temperature measuring element Rs form a heat sensitive portion 4. In addition, at a location on the substrate 1 that is most thermally isolated from the heating element Rh, that is, on the substrate 1 upstream of the moat 2, a fluid temperature measuring element Rf formed by an electric resistor is used.
Are formed in a substantially V-shaped predetermined pattern.
Further, on the beam 3, an upstream beam temperature measuring element Ru formed of an electric resistor is formed on the upstream side without overlapping with the heating element Rh and the temperature measuring element Rs, and on the downstream side, the heating element Rh and the temperature measuring element Ru. A downstream beam temperature measuring element Rd formed by an electric resistor is formed without overlapping the body Rs. The upstream beam temperature measuring element Ru and the downstream beam temperature measuring element Rd have the same pattern shape and are symmetrically formed with respect to the longitudinal center line of the beam 3.

Further, the heating element Rh and the fluid temperature measuring element Rf
In order to apply the heating power to the heating element Rh so as to realize a driving method for making the temperature difference between the temperature measuring element Rs and the fluid temperature measuring element Rf balance adjustment (not shown) in the first bridge circuit 5. A first electric bridge circuit 8 is formed by being bridge-connected to the resistor for use and having its output side connected to the Rh drive circuit 7 via the OP amplifier 6. The output of the Rh driving circuit 7 is connected to both ends of the heating element Rh and is capable of giving a variable heating power. That is, in the first electric bridge circuit 8, the heating element Rh
To maintain a constant temperature difference with respect to the fluid.
The heating power applied to h is varied. In addition, the upstream beam temperature measuring element Ru and the downstream beam temperature measuring element Rd
Is bridge-connected to another balance adjusting resistor (not shown) to form a second electric bridge circuit 9. That is, the second electric bridge circuit 9 detects the temperature difference between the upstream side beam temperature measuring element Ru and the downstream side beam temperature measuring element Rd, and the flow velocity is zero at the point where the output f ₂ is zero. It is determined that there is.

Rh of these first electric bridge circuits 8
Output f ₁ of the drive circuit 7 and the output f ₂ of the second electrical bridge circuit 9 is input via an A / D converter 10 memory calculator (digital memory arithmetic circuit) 11. The memory computing unit 11 includes, for example, a ROM and a RAM circuit in which reference data and a computation program, which will be described later, are incorporated, and a zero correction process and a flow velocity calculation process are performed by a predetermined correction method and software. Is to do.

Here, a more specific configuration example will be described. First, an SiO ₂ layer, which is a heat insulating material, is formed on the upper surface of the substrate 1 by using an oxidation treatment method, a sputtering vacuum film formation method, or the like. This heat insulating layer may be Si ₃ N ₄ , metal oxides such as Ta ₂ O ₅ or Al ₂ O ₃ , and may have a multilayer film structure in which a SiO ₂ layer and a Si ₃ N ₄ layer are combined. Good. The film thickness is preferably about 0.5 to 2 μm. Then, a moat 2 and a beam 3 having a shape that promotes fluid intrusion as shown in FIG. 1 are formed on the substrate 1 by the KOH anisotropic etching method. At this time, the depth of the moat 2 needs to be equal to or more than the thermal boundary layer formed at the minimum flow velocity to be measured, and here, as an example, a flow rate of 3 liters per hour can be measured so as to correspond to a fluidic flow meter, The depth was 150 μm.

Then, a Ta ₂ O ₅ layer (Ti) is formed on the upper surface of the beam 3 forming the heating element Rh and the temperature measuring element Rs in order to improve the adhesion between the heating element layer and the substrate 1 (beam 3). , Cr, T
a, NiCr, TiN or the like) may be formed as a lower adhesion strength reinforcing layer, and Pt (Ni, Ni, a metal having a high specific resistance) is formed in the upper portion of the Ta ₂ O ₅ layer and in the center of the beam 3.
The heating element Rh may be formed of W, Ta, or the like, in short, as long as it is a material having a temperature dependence of the specific resistance characteristic).

Further, a temperature measuring element Rs made of a material having a high resistance temperature coefficient, such as Pt, is formed in a pattern so as to be adjacent to the heat generating element Rh. On the beam 3, an upstream beam temperature measuring element Ru is formed on the upstream side and a downstream beam temperature measuring element Rd is formed on the downstream side in the same shape, for example, of Pt material. On the other hand, on the surface of the substrate 1 that is thermally isolated from the heat sensitive portion 4, for example, Pt
The fluid temperature measuring element Rf is formed into a pattern. The fluid temperature measuring element Rf is preferably formed at the most upstream position with respect to the flow and away from the heat sensitive section 4.

Then, these heating element Rh and temperature measuring element Rs
, Rf, Ru, Rd, a Ta ₂ O ₅ layer is formed as an upper adhesion strength reinforcing layer for improving the bondability with the protective layer.

These adhesion strength reinforcing layer and resistance layer (heating element Rh, etc.) may be formed by a vacuum film forming method such as a vapor deposition method, an electron beam vapor deposition method, or a sputtering method. The shape cutting may be performed by a lift-off method, an Ar sputtering / etching method, or the like. Also, the upper and lower adhesion strength reinforcing layers T
The thinner the a ₂ O ₅ layer is, the better, but it is preferable to set the thickness to about 100 to 700 Å in order to ensure the compatibility with Pt which is the resistance layer.

Further, since the temperature measuring elements Rs, Rf, Ru, and Rd are driven within a range in which the linearity of the current / voltage characteristics can be maintained, the film thickness of the Pt resistance layer should be sufficiently lower than the critical density. 500 to 5 depending on the condition and the condition for setting the resistance value.
It is good to set it to about 000Å. Further, a protective layer made of SiO ₂ or Si ₃ N ₄ is formed so as to cover the heating element Rh and the temperature measuring element Rs via an adhesion strength reinforcing layer made of a Ta ₂ O ₅ layer. This protective layer is preferably thin for the purpose of reducing the heat capacity in order to improve the sensitivity of the temperature sensing element Rs and for the purpose of improving mass productivity. It can be said that thicker ones are preferable. From this point of view, the thickness of the protective film is 800 to 5000Å
It is good to set the degree.

Under such a configuration, the outputs f ₁ and f ₂ of the _first and _second electric bridge circuits 8 and 9 are taken into the memory calculator 11 through the A / D converter 10 and held therein. When the flow velocity is zero or in the range near zero, the zero point correction of the relationship between the flow velocity and the output of the heating element Rh is performed, and the calculation process for obtaining the flow velocity is performed. A zero point correction method corresponding to the invention of claim 3 will be described with reference to FIG.
First, the upstream beam temperature measuring element Ru and the downstream beam temperature measuring element R
Output f ₂ is the temperature difference between the second electrical bridge circuit 9 including the d is, at a flow rate near zero is a value that varies reduce the zero point. Therefore, the output f ₂ having this fluctuation width is passed through the A / D converter 10 having a larger discrete conversion width,
The correction execution signal is "0" or "1" (see FIG. 2B). That is, when the correction execution signal becomes “0”, the zero point correction section is set, and the heating element Rh output (f ₁ ) has a flow velocity u of zero. From this value, it is stored in the memory of the memory calculator 11 in advance. The held calibration value (reference data) at the flow velocity u = 0 is subtracted, and the subtracted value is used as the variation amount ΔV to be calibrated. Here, in reality, the correction execution signal becomes "0" in the flow velocity range of a certain range from the flow velocity u = 0 point (see FIG. 2B), and therefore the flow rate region that is recognized as this zero point. F ₁ which is the output of the heating element Rh in the (zero point correction section)
Of holds the width Delta] f ₁ in advance in the memory, if the calculated variation amount ΔV as described above is smaller than the width Delta] f _1, the variation amount ΔV to zero (i.e., there was no change Assumed). Then, the variation amount ΔV calculated from the flow velocity measurement value from the next time is subtracted to obtain a calibration value.

As described above, according to this embodiment, the heating element R is arranged so that the temperature becomes constant on the large heat radiation surface on the beam 3.
h and the temperature measuring element Rs are formed, and the upper and lower beam temperature measuring elements are used as preliminary temperature measuring elements for the purpose of detecting the output fluctuation of the heating element Rh on the upstream side and the downstream side on the same beam 3. Since Ru and Rd are formed and the second electric bridge circuit 9 is configured with another balance adjustment resistor to perform the above-described arithmetic processing, the main output of the heating element Rh The fluctuation range ΔV due to factors such as room temperature change of the voltage drop output, fluid temperature change, natural convection, etc. can be detected successively. Therefore, long-term fluctuations can be dealt with while maintaining a high heat dissipation effect per unit input power. The obtained zero point correction can be performed, and the flow velocity can be detected with high accuracy. At this time, heat loss from the heat-sensitive portion 4 to the substrate 1 lowers heat radiation per unit input power, resulting in a decrease in flow velocity detection sensitivity, and at the end of the beam 3, the temperature of the substrate 1 close to room temperature. Is almost equal to the temperature of
In order to deal with the problem that the resistance element for the temperature measuring element is arranged at the end of the beam 3 to lower the temperature measuring sensitivity, as shown in FIG.
The shape of the beam 3 and the resistor (heating element Rh, temperature measuring element Rs,
By optimizing the arrangement pattern of Rf, Ru, Rd), it is possible to improve both the heat radiation characteristics and the zero point detection sensitivity.

Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those shown in the above-mentioned embodiments are designated by the same reference numerals (the same applies to the following embodiments).
This embodiment corresponds to the invention described in claim 4, and the outputs f ₁ and f ₂ of the _first and _second electric bridge circuits 8 and 9 are taken in through the A / D converter 10 and held, and the flow velocity is sequentially increased. The memory arithmetic unit 11 has a ROM and a RAM circuit that incorporates reference data and an arithmetic program for performing arithmetic processing for obtaining the flow velocity while performing a zero point correction of the relationship between the output of the heating element and the output of the heating element Rh. .

FIG. 3 shows a zero point correction method by such a memory calculator 11. First, the output f ₂ from the second electric bridge circuit 9 including the upstream beam temperature measuring element Ru and the downstream beam temperature measuring element Rd to the flow velocity u is A /
The output relationship is represented by the f ₂ step function f ₂ <u> via the D converter 10. Since this output is small, the flow velocity value that can be determined is a coarse discrete value. On the other hand, the voltage drop value from the heating element Rh driven by the first electric bridge circuit 8 has an output relationship approximately represented by a function f ₁ (u) having a large slope.

Here, the representative flow velocity value during each step i (i = 1 to N) representing the f ₂ step function f ₂ <u>
u> _i is held in the memory of the memory calculator 11 in advance. This is for finding the flow velocity section (step) i based on the output f ₂ which is the temperature difference measured during the actual measurement, and for searching the representative flow velocity value <u> _i . The f ₁ function f ₁ (u) corresponding to the output voltage value of the heating element Rh is f ₁ (u) = f _0i + [∂f / ∂u] _i u + ΔV in the i-th flow velocity section i. (1) However, f _0i is the intercept of the linear curve in the section i, and [∂f / ∂u] _i indicates its slope. Where f _0i
And [∂f / ∂u] _i are stored in advance in the memory of the memory calculator 11 as calibration data (reference data), and are read out as needed. ΔV is a variation amount over a long period of time, and is substantially evenly applied to the f ₁ function f ₁ (u) in the entire flow velocity region. If this value is not known, a measurement error will occur. In the zero-point correction method of the present embodiment, this variation amount ΔV is sequentially determined at the time of actual flow velocity measurement.

Next, f corresponding to the i-th flow velocity section i
<∂f ₁ / ∂u> _i , which is the average slope of _one function f ₁ (u), is measured in advance for all the flow velocity sections i = 1 to N and stored in the memory of the memory calculator 11. Here, according to the research conducted by the present inventors, it has been found that the fluctuation amount ΔV has little dependence on the flow velocity u and is constant in a short period of time. That is, since the sampling step interval Δt of the heat-sensitive flow velocity measuring element actually used is performed from several milliseconds to several minutes, it is expressed by the equation (2),

[Equation 1] Even if it is considered that ΔV is constant, there is no problem.

At the time of actually measuring the flow velocity, an arithmetic processing method is adopted in which the variation amount ΔV is estimated and the flow velocity value is narrowed down by using the above-mentioned calibration data stored in the memory based on the measured data outputs f ₁ and f _2. . That is, if the flow velocity section corresponding to the output f ₂ in the n-th sampling is number i, the representative flow velocity value <u> _{i of the} section _i and the slope [∂f / ∂ _] of the output f ₁ are searched by memory search. u] _i and the intercept f _0i are read as reference data.

[Outer 1]

[Equation 2] Is estimated as.

[0033]

[Outside 2] Assuming that the corresponding flow velocity section is number j, the slope [∂f / ∂u] _{j of the} output f ₁ and the intercept f _0j are searched as reference data from the memory, and these are _expressed by equations (1) and (3).

[Outside 3] Is performed by the memory calculator 11 according to a calculation program.

[Equation 3]

[0034]

[Outside 3] The difference between the values <u> _i becomes larger than ΔV, and when the above-described correction processing is performed, the error becomes rather large. Therefore, the maximum output f of the heating element Rh in the flow velocity section i
The maximum difference between _1max and the representative flow velocity value <u> _i is set as δf _maxi, and is stored in the memory in advance so that it can be referred to by the section number. If the fluctuation amount ΔV obtained by the calculation process of the formula (3) is smaller than the maximum difference δf _maxi , the process of the formula (4) is executed as it is. On the contrary, if the fluctuation amount ΔV is larger than the maximum difference δf _maxi , the fluctuation amount ΔV is zero. The same process is performed by considering that.

By sequentially performing the writing, holding, reading and arithmetic processing of the reference data in such a memory,
While maintaining the output of the heating element Rh having a large slope and high sensitivity to the flow velocity u, long-term large fluctuation factors can be successively removed, and the accuracy of flow velocity detection can be increased.

Further, a third embodiment of the present invention will be described with reference to FIG. In this embodiment, the structure around the beam 3 is devised, and a through hole 12 is formed at a connection point between the substrate 1 and the beam 3. The shape of these through holes 12 is determined by a balance between reduction of heat loss, strength, and securing of a heat radiation area. Further, if these through holes 12 are formed so as to extend to the edge of the substrate 1 as shown in the drawing, the heat loss characteristics can be improved without reducing the heat radiation area. Here, as an example, two through holes 12 are formed at both ends of the beam 3 so that the upstream side and the downstream side of the beam 3 are symmetrical. Here, the through hole 12 is a rectangular hole having a length Lhole = 100 μm and a width Whole = 80 μm, but the shape is not limited to such a shape.

Explaining the dimensions of the other parts,
First, regarding the beam 3, the total length Lb = 1200 μm, full width Wb = 250 μm. Heating element Rh (Temperature measuring element R
s is the same), the length Lh = 800 μm, its width Wh = 190 μm. Regarding the upper and lower beam temperature measuring elements Ru and Rd, the length Lu = Ld = 800 μm
(= Lh ), And the width Wu = Wd = 23 μm.

However, for each of these dimensions, the beam 3
Total length of Lb Is 750 μm or more and 1500 μm or less, its full width Wb Is 150 μm or more and 300 or less, and thus the total length Lb With respect to the length Lh of the heating element Rh Is 80% or less,
Full width Wb Against the width Wh of the heating element Rh Is 80% or less, full length Lb On the other hand, if the lengths Lu and Ld of the upstream and downstream beam temperature measuring elements Ru and Rd are 80% or less, the heat radiation characteristic and the strength characteristic of the beam 3 are not extremely deteriorated. It may be formed with the inner dimensions. Also, the heating element Rh
The arrangement of the temperature measuring element Rs and the temperature measuring element Rs may be interchanged between the upstream side and the downstream side as illustrated.

A fourth embodiment of the present invention will be described with reference to FIG. This embodiment corresponds to the invention described in claim 2,
The structure of the beam 3 is devised. First, the configuration shown in FIG. Schematically, the beam 3 is divided into three in the flow direction by masking and etching. That is, the central beam portion 13 for forming the heating element Rh and the temperature measuring element Rs is secured, and the upstream side of the central beam portion 13 has a small area for forming the upstream beam temperature measuring element Ru. The upstream beam portion 14 is provided by connecting with a plurality of auxiliary thin bridges 15, and the downstream beam temperature measuring element Rd is provided on the downstream side of the central beam portion 13.
The downstream beam portion 16 having a small area for forming the above is connected by a plurality of auxiliary thin bridges 17. These shapes are symmetrical with respect to the central beam portion 13 in the flow direction.

According to such a three-divided structure of the beam 3, it is possible to further improve the heat dissipation characteristics and the zero point detection sensitivity. That is, the upper beam portion 14 and the lower beam portion 16 for arranging the upper and lower beam temperature measuring elements Ru and Rd are independently formed, and these are formed with the central beam portion 13 which is a heat radiating surface and an auxiliary member. Since the bridges 15 and 17 are connected to each other and the areas of the upstream beam portion 14 and the downstream beam portion 16 are set to be small, the heat capacity can be reduced. Further, when there is no wind, the upstream beam portion 14 and the downstream beam portion 16 are quickly heated by heat transfer from the central beam portion 13 via the bridges 15 and 17, and exhibit symmetrical high temperature.
The output of the second electric block circuit 9 including the downstream side beam temperature measuring elements Ru and Rd becomes zero. On the other hand, when the wind begins to occur, since the air is placed away from the central beam portion 13, the upstream and downstream beam portions 1 of the upper and lower beam temperature measuring elements Ru and Rd are measured.
4, the heat dissipation rate in the downstream beam section 16 is 1
It becomes faster than the heat transfer rate from the central beam portion 13 via the Nos. 5 and 17. For this reason, the temperature of the downstream beam temperature measuring elements Ru and Rd is heated to a high temperature when there is no wind, and the temperature of the downstream beam temperature measuring elements Ru and Rd drops more rapidly than in the case where the independent upstream beam portion 14 and the downstream beam portion 16 are not provided. Become. Further, since the heat capacity and the heat radiation area of the upstream beam portion 14 and the downstream beam portion 16 are small, even if the wind strength is further increased, the sensitivity characteristic will be quickly dulled or will reach a saturated state. Therefore, as in the present embodiment, by providing independent beam portions for the upper and lower beam temperature measuring elements Ru and Rd, the output difference between when the flow velocity is zero and when the flow velocity is small is provided. Can be increased, and the accuracy of zero point detection can be improved while maintaining the heat dissipation characteristics of the central beam portion 13.

Although FIG. 2B is also basically the same, for example, a beam 3 as shown in FIG. 4 is used as a base and this is used as a central beam portion 18, and the upstream side of such a central beam portion 18 is used. , The downstream side is projected through the thin bridge 19, and the upstream beam portion 20,
The downstream beam portion 21 is formed and divided into three parts.

In any case, the heat radiation areas of the upstream beam portions 14 and 20 and the downstream beam portions 16 and 21 are at least the central beam portion 1.
Half of 3,18 or less, preferably 1/4 or less 1/15
The above is set.

Further, a fifth embodiment of the present invention will be described with reference to FIG. In the present embodiment, the thermosensitive anemometer 22 according to the above-mentioned embodiment is used as a fluidic flowmeter 23. First, the basic structure of the fluidic flow meter 23 will be described. On the path connecting the inflow pipe 24 and the discharge pipe 25, a set ring space 26, a flow channel contracting unit 27, a nozzle 28, and a flow channel expanding unit 29 are provided in order. In addition, the flow path expanding section 29 is provided with a pendulum 30 and an end block 31. Behind the end block 31 is a discharge space 32. As a result, the tubular flow from the upstream side of the flow channel is rectified into a two-dimensional flow in the set ring space 26, further rectified by the flow channel contracting section 27, and smoothly flows toward the nozzle 28. The jet flow rectified by the nozzle 28 is divided into left and right when it hits the pendulum 30, but the flow path expanding portion 29 up to the end block 31.
In the above space, when the flow rate exceeds a certain value, the instability of the vortex formed behind the exciter 30 forms a flow biased to the left or the right. Therefore, the flow colliding with the end block 31 follows the front surface of the end block 31 along the nozzle 28.
Reach the exit of and hit the jet at right angles. Therefore, the direction of the jet flow is biased in the direction opposite to the initial drift by the flow returning from that side. This causes the same on the other side again, resulting in nozzle 2
The flow exiting 8 changes its direction in a regular and alternating manner. The frequency of this regular directional vibration increases linearly with increasing flow rate.

In this embodiment, however, in such a fluidic flowmeter 23, the element portion such as the substrate 1 of the thermal velocity meter 22 is arranged in the central portion of the nozzle 28 through an appropriate supporting means. Such a heat-sensitive anemometer 22 may be of any of the embodiments described above. Also, the installation location is not limited to the central portion of the nozzle 28, and may be, for example, the lower portion of the inner wall of the nozzle 28, the ceiling portion of the nozzle 28, or the like.

According to the present embodiment, since the thermosensitive anemometer 22 has a high heat dissipation effect and has no protrusion such as a lead wire, the flow velocity can be measured even in a low flow rate range of 3 to 300 liters per hour for a long time. Was created. As a result, the gas meter can measure the entire flow rate range of 3 to 3000 liters per hour.

[0046]

According to the invention described in claim 1, the upstream beam temperature measuring element and the downstream beam temperature measuring element are formed as the preliminary temperature measuring elements on the upstream side and the downstream side on the same beam. Regarding the main temperature measuring element and the fluid temperature measuring element side, the first electric bridge circuit is formed together with the balance adjusting resistor to form a first heating element in order to make the temperature difference between the heating element and the fluid temperature measuring element constant. The heating power to be applied to the upstream beam temperature measuring element and the downstream beam temperature measuring element are made small by forming a second electric bridge circuit together with other balance adjusting resistors. What can detect flow and no flow,
Since the digital memory arithmetic circuit is configured to hold the outputs of the first and second bridge electric circuits and perform the arithmetic processing for obtaining the flow velocity, the room temperature change of the voltage drop output of the heating element, which is the main output, and the fluid temperature. It becomes possible to sequentially detect the fluctuation range due to factors such as change and natural convection.
The so-called zero point correction can be performed while maintaining a high heat dissipation effect per unit input power, and the flow velocity measurement accuracy is good.

In particular, according to the second aspect of the invention, the beam portion forming the upstream beam temperature measuring element or the downstream beam temperature measuring element is used as an upstream beam portion or a downstream beam portion having a small area. It is formed by dividing it from the central beam part that forms the main part of the main beam, and is connected to the central beam part by an auxiliary thin bridge. The accuracy of can be improved.

Further, according to the invention of claim 3 or 4, the R in which the predetermined reference data and the operation program are incorporated.
As the digital memory arithmetic circuit having the OM and RAM circuits, the flow velocity is calculated by performing the zero point correction of the relation between the flow velocity and the heating element output at any time or sequentially, so that the flow velocity detection accuracy can be improved.

Further, according to the invention of claim 5, the heat dissipation efficiency is improved as described above at any of the center of the fluidic oscillator of the fluidic flowmeter, the lower part of the inner wall of the nozzle or the ceiling. Since the thermosensitive anemometer is provided, it is possible to accurately measure a low flow rate with low power.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a characteristic diagram for explaining the zero-point correction method.

FIG. 3 is a characteristic diagram for explaining a zero point correction method according to a second embodiment of the present invention.

FIG. 4 is a plan configuration diagram showing a third embodiment of the present invention.

FIG. 5 is a plan configuration diagram showing a fourth embodiment of the present invention.

FIG. 6 is a horizontal sectional view showing a fifth embodiment of the present invention.

[Explanation of symbols]

1 Substrate 2 Moat 3 Beam 4 Heat Sensitive Section 8 First Electrical Bridge Circuit 9 Second Electrical Bridge Circuit 11 Digital Memory Arithmetic Circuit 13 Central Beam Section 14 Upstream Beam Section 15 Bridge 16 Downstream Beam Section 17 Bridge 18 Central Beam Section 19 Bridge 20 Upstream Beam 21 Downstream Beam 28 Nozzle Rh Heating element Rs Thermometer Rf Fluid temperature measuring element Ru Upstream beam temperature sensor Rd Downstream beam temperature sensor

Claims (5)

[Claims] 1. A substrate, a moat formed on a part of the substrate by anisotropic etching, a beam formed across the moat, a heating element made of an electric resistor, and the heating element integrated with or separately from the heating element. A heat sensing part formed on the beam as a body for measuring the temperature of the heating element, and an electric resistance formed on the beam upstream side without overlapping the heating element and the temperature sensing element. It is formed on the upstream and downstream sides of the beam in parallel with the upstream beam temperature measuring body without overlapping with the upstream beam temperature measuring body by the body and in parallel with the upstream beam temperature measuring body and having the same length and width. Downstream beam temperature thermometer using an electric resistor, a fluid temperature thermometer which is arranged on or outside the substrate to measure a fluid temperature, the temperature thermometer and the fluid temperature thermometer, and balance adjustment And a resistor for use to form a constant temperature difference between the heating element and the fluid temperature measuring element. It is formed by a first electric bridge circuit that varies the heating power applied to the heating element, the upstream beam temperature measuring element, the downstream beam temperature measuring element, and other balance adjusting resistors. And a digital memory arithmetic circuit that holds the outputs of the first and second electric bridge circuits and that performs arithmetic processing for obtaining the flow velocity. 2. An upstream side beam temperature measuring element is constructed by connecting the beam to a central beam section where a heating element and a temperature measuring element are formed and a plurality of thin bridges auxiliary to the central beam section. Divided into three parts: a small area upstream beam part to be formed and a small area downstream beam part where a downstream side beam temperature measuring element is formed by being connected to the central beam part by a plurality of auxiliary thin bridges. The thermosensitive anemometer according to claim 1, wherein the thermosensitive anemometer is formed. 3. The arithmetic processing for holding the outputs of the first and second electric bridge circuits and correcting the zero point of the relationship between the flow velocity and the heating element output when the flow velocity is zero or in the range near zero is performed. 3. A thermosensitive anemometer according to claim 1, wherein the thermosensitive anemometer is a digital memory arithmetic circuit having a ROM and a RAM circuit in which reference data and an arithmetic program for the above are incorporated. 4. A reference data and a calculation program for holding the outputs of the first and second electric bridge circuits and performing a calculation process to obtain a flow velocity by sequentially correcting the zero point of the relationship between the flow velocity and the heating element output. 3. A thermosensitive anemometer according to claim 1, wherein the thermosensitive anemometer is a digital memory arithmetic circuit having a ROM and a RAM circuit. 5. The fluidic vibrator according to claim 1, wherein the nozzle center, the nozzle inner wall lower portion, or the ceiling portion is provided.
A fluidic flowmeter, comprising the substrate of the heat-sensitive anemometer described in 2, 3, or 4.