JPH0535366B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a thermal gas flow rate measuring device, and more specifically, the present invention relates to a thermal gas flow rate measuring device. This invention relates to a flow rate measuring device for a gas to be measured, which measures the flow rate of the gas to be measured based on a change in the electrical resistance value of an electrical resistor on the downstream side of a flow path due to a temperature change due to the gas flow. be.

(Prior art) In the above-mentioned flow rate measurement device, conventionally, an X-shaped or V-shaped electrical resistor is inserted into the gas flow path, but this causes turbulence in the gas flow, changes in the flow velocity, or Since the gas flow velocity is different between the center side and the wall side of the passage, it is difficult to accurately reproduce the detection of gas temperature and the heating of the gas, which is a factor in reducing measurement accuracy.

(Objective of the Invention) The object of the present invention is to eliminate the above-mentioned drawbacks through simple improvements.

(Structure of the Invention) In order to achieve the above object, the present invention provides an apparatus for measuring the flow rate of a gas to be measured described at the beginning, in which an electrically resistive material is provided on at least one side of a substrate in which a large number of through holes for gas flow are formed. The plurality of electrical resistors are arranged so that the gas to be measured, which is provided at intervals in the direction of the gas flow path while crossing the gas flow path, is caused to branch and flow within the flow path through the through hole. It has characteristics.

(Function) Therefore, the flow velocity distribution of the gas to be measured is regulated when it passes through the numerous through holes, and the flow of the gas to be measured with this flow velocity distribution regulated and the accompanying heat transfer. Accordingly, the flow rate of the gas to be measured is measured.

(Effects of the Invention) Therefore, according to the above characteristic configuration, the gas temperature in the flow path becomes uniform, and the gas is heated with good reproducibility.
Thus, the flow rate of the gas to be measured can be measured with high accuracy.

Embodiments of the present invention will be described below based on the drawings.

(First Embodiment) FIG. 1 shows a schematic cross-sectional view of a so-called auxiliary heating type gas flow rate measuring device, in which one heating electric resistor 1
A and two heat-sensitive electrical resistors 1B, 1C are spaced apart in the flow path direction within the flow path A of the gas to be measured, with the heating resistor 1A positioned between the heat-sensitive resistors 1B, 1C. and the heat sensitive resistor 1
An electric circuit B is connected to the resistors 1A, 1B, and 1C, so that almost no current flows through B and 1C, but current flows through the heating resistor 1A.

When the gas to be measured is caused to flow through the gas flow path A, the gas is heated by the heating resistor 1A,
The heat is given to the downstream heat-sensitive resistor 1C,
The temperature of the downstream heat-sensitive resistor 1C becomes higher than the temperature of the upstream heat-sensitive low antibody 1B, and due to the temperature difference between the downstream heat-sensitive resistor 1C and the upstream heat-sensitive resistor 1B, both heat-sensitive resistors 1B, A difference occurs in the electrical resistance value of 1C, the balance of the bridge circuit for both heat-sensitive resistors 1B and 1C is disrupted, and a voltage corresponding to the mass flow rate of the gas to be measured is output to terminals 2 and 2. The flow rate of the gas to be measured is measured.

To explain the specific structure of the heating resistor pair 1A, as shown in FIG. 2, the substrate 3 is a silicon crystal wafer obtained by thinly slicing a silicon ingot. Small circular gas conduction through hole a
..., and then apply oxidation method or plasma CVD (Chemical Vapor
An insulating film b of an inorganic material such as silicon tetranitride is formed by a method (abbreviation for Deposition).

Prior to forming the insulating film b, it is desirable to perform a polishing treatment on the surface of the substrate 3 on which the insulating film is to be formed.

In other words, a silicon wafer formed by slicing a silicon ingot has 30 to
A process-affected layer reaching a depth of 60 μm has been formed, and the sliced surface is rough.In this case, even if an insulating film b is formed on the surface, there is a risk that this will peel off, and the process-affected layer In addition, it is desirable to ensure the formation of the insulating film b by mechanical polishing such as wrapping and polishing, or chemical polishing using a chemical solution such as an alkali.

Next, a film of nichrome, for example, is formed at a predetermined location on the insulating film b by sputtering, and a photoresist is applied onto the film. Then, a mask having a resistor pattern shaped like threading through the through holes a is placed over the photoresist, and exposure and phenomenon are performed to form an etching pattern on the photoresist.

Then, the resistor film is etched using an ion beam milling device or the like to form a resistor pattern of a predetermined shape. The photoresist is then removed by ion beam etching or a solvent to form a heating electrical resistance material c in a predetermined pattern.

Note that 4 in the figure is a bonding pad made of, for example, gold, and is for connecting the lead wire 5.

Next, a protective film d made of an inorganic material such as silicon dioxide by a sputtering method or silicon tetranitride by a plasma CVD method is formed on the upper surface of the electrically resistive material c except for the bonding pad 4, and the protective film d The upper surface of the insulating film b is polished using the same method as that for the insulating film b.

Although the heating resistor 1A is constituted by the above, the material of the substrate 3 may be replaced with ceramic, glass, or metal such as stainless steel.

Now, the specific structure of the heat-sensitive resistors 1B and 1C is almost the same as that of the heating resistor 1A, and the only difference is that the electrical resistance material e is a metal with a large temperature coefficient such as nickel or platinum. It is something.

According to the above configuration, the split flow ratio of the gas to be measured is fixed by branching the gas to be measured through the many through holes a, and the flow rate of the gas to be measured is accurate and reproducible. Gas flow rate can be measured easily.

In FIG. 1, 6... in the figure is a body that connects the resistors 1A, 1B, and 1C in a sandwiched manner, and is made of metal such as stainless steel, ceramic, etc., and is connected by diffusion bonding or adhesive. Alternatively, they may be mechanically connected by bolts or nuts with a packing seal interposed.

(Second Embodiment) FIG. 3 schematically shows a so-called self-heating type gas flow rate measuring device. In this device, two heating resistors 1D and 1E having the same configuration as the heating resistor 1A having the heating electric material c on one side are placed in the flow path A of the gas to be measured with an interval in the flow path direction. A circuit C is connected to the resistors 1D and 1E to cause them to generate heat by flowing current through them.
Then, when the gas to be measured is caused to flow through the gas flow path A,
The gas is heated and heat moves from the upstream heating resistor 1D to the downstream heating resistor 1E, and as in the case of the auxiliary heating method, a voltage corresponding to the mass flow rate of the gas to be measured is applied to the terminals 2, 2. It is now output to .

(Third Embodiment) FIG. 4 schematically shows a so-called Thomas type gas flow rate measuring device. This includes a heating thermosensitive resistor 1F in which a heating electrical resistance material c is provided on one side of the substrate 3 and a heat sensitive electrical resistance material e on the other side, and a substrate 3.
A heat-sensitive resistor 1G having a heat-sensitive electric resistance material e provided on one side thereof is separated from the heat-sensitive resistor 1G in the flow path direction with the heated heat-sensitive resistor 1F positioned downstream of the heat-sensitive resistor 1G. It is placed in the flow path A, and a known electric circuit (not shown) in the Thomas method is connected to both resistors 1F and 1G,
When a current is passed through the electric circuit and a gas to be measured is passed through the gas flow path A, the heating thermosensitive resistor 1F dissipates thermal energy, and the amount of heat absorbed or dissipated by the gas is Since it is proportional to the flow rate (mass) of the passing gas, the gas flow rate is measured by calculating the amount of heat released by the heating thermosensitive resistor 1F.

That is, the gas flow rate is measured based on the amount of electrical energy lost in the heated thermosensitive resistor 1F based on the temperature change due to heat radiation, or the amount of electrical energy applied to compensate for this loss.

Note that any of the electrical resistors 1A to 1G may be arranged inverted in the direction of the flow path. That is, for example, in the electrical resistor 1A, the electrical resistance material c of the electrical resistor 1A may be placed in the direction of the flow path with respect to the substrate 3. Although the electrically resistive material c is arranged on the upstream side, it may be arranged on the downstream side of the flow path with respect to the substrate 3.

In addition, although the gas flow passage a is circular, as shown in part in FIG. 5 A and B, the through hole a
It is also possible to make it triangular or hexagonal, or, although not shown, it can be changed to a quadrilateral or pentagon.
Regardless of the shape, it is preferable to form them to the same size, and in this case, since the amount of gas passing through each through hole a becomes constant, some of the through holes a
It is also possible to provide electrically resistive materials c and e around it and to estimate the total amount of gas passing through based on the amount of gas passing through some of the through holes a.

[Brief explanation of the drawing]

The drawings show a flow rate measuring device for a gas to be measured according to the present invention, and FIG. 1 is a schematic sectional view of the flow rate measuring device of the first embodiment, and FIG. 2 is a cutaway perspective view of an electric resistor. 3 and 4 are schematic cross-sectional views of the flow rate measuring devices of the second and third embodiments, respectively, and FIGS. 5A and 5B are partial explanatory diagrams showing another embodiment of the gas distribution through hole. . A...Gas flow path to be measured, 1A to 1G...Electric resistor, 3...Substrate, a...Through hole for gas distribution, c
...Electric resistance material for heating, e...Electric resistance material for heat sensitivity.

Claims (1)

[Claims] 1. Electrical resistors are provided at intervals in the direction of the flow path in the flow path of the gas to be measured, and the electrical resistance of the electric resistor on the downstream side of the flow path due to temperature changes due to the gas flow is measured. A flow rate measurement device for a gas to be measured that measures the flow rate of the gas to be measured based on a change in value, comprising an electrical resistance material provided on at least one side of a substrate in which a large number of through holes for gas flow are formed. A device to be measured, characterized in that a plurality of electrical resistors are provided at intervals in the direction of the gas flow path while crossing the gas flow path, and the gas to be measured is caused to branch and flow within the flow path by the through hole. Gas flow rate measuring device. 2. The electric resistor is composed of two heating resistors each having an electric resistance material provided only on one side of the substrate, and the two heating resistors are spaced apart in the gas flow path in the flow path direction. The flow rate of the gas to be measured is measured based on the change in the electrical resistance value of the downstream heating resistor due to heat imparted from the upstream heating resistor to the downstream heating resistor. 1
A flow rate measurement device for a gas to be measured as described in . 3. The electric resistor is composed of one heating resistor, each of which has an electric resistance material provided only on one side of the substrate, and two heat-sensitive resistors arranged before and after the flow path of the heating resistor, and According to claim 1, the flow rate of the gas to be measured is measured based on a change in the electrical resistance value of the downstream heating resistor due to heat imparted from the resistor to the downstream heating resistor. Flow measurement device for gas to be measured. 4. The electrical resistor is a heating heat-sensitive resistor in which a heating electrical resistance material is provided on one side of the substrate and a heat-sensitive electrical resistance material is provided on the other side, and a heat-sensitive electrical resistance material is provided only on one side of the substrate. The heated heat-sensitive resistor is disposed downstream of the heat-sensitive resistor, and the heat-sensitive electrical resistance material of the resistor is heat-sensitive by dissipating heat from the heated heat-sensitive resistor as the gas to be measured flows. 2. A flow rate measurement device for a gas to be measured according to claim 1, wherein the flow rate of the gas to be measured is measured based on a change in the electrical resistance value of the gas. 5. The flow rate measuring device for a gas to be measured according to any one of claims 1 to 4, wherein all of the gas flow through holes are formed to have the same size.