JP3763225B2 - Ion drift type flow meter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flow meter for measuring a flow velocity or flow rate of a fluid in an industrial field, a medical field, or the like, and more particularly to an ion drift type flow meter.
[0002]
[Prior art]
An example of a conventional ion drift flow meter will be described with reference to FIG. In the figure, reference numeral 1 denotes an ion drift type flow meter that measures the flow rate of air flowing through the circular tube 11.
[0003]
As shown in FIG. 4, the ion drift type flow meter 1 includes a disc-shaped corona electrode 12 and a collector electrode 13 having a predetermined resistance. When measuring the flow rate of air flowing through the circular tube 11, the corona electrode 12 is placed on the central axis of the circular tube 11, while the collector electrode 13 is provided so as to cover the outer peripheral surface of the cylinder 11, and the collector The upstream side portion 131 and the downstream side portion 132 of the electrode 13 are grounded.
[0004]
By the way, although an electric field is generated between the corona electrode 12 and the collector electrode 13, the electric field is locally concentrated at the peripheral end portion of the corona electrode 12, resulting in an unequal electric field state. A corona discharge state occurs in which discharge is performed only at the peripheral end of the electrode 12. In this part, fluid molecules or particles in the fluid are ionized, drifts toward the collector electrode at a velocity V _d , and a current flows. At this time, if there is a flow in the fluid in the circular pipe 11, the drifting ions shift by D at the arrival center according to the flow velocity or flow rate. Since the collector electrode 13 has an appropriate resistance, assuming that the current flowing in the upstream side 131 is I ₁ and the current flowing in the downstream side 132 is I ₂ , D = C · (I ₂ −I ₁ ) / (I ₂ + I ₁ ) (C is a constant), the flow velocity or flow rate can be detected from this. Such an ion drift type flow meter has a very high responsiveness because the responsiveness is determined by the movement time of generated ions between the electrodes. Moreover, since there is no moving part, there are advantages such as high mechanical reliability.
[0005]
[Problems to be solved by the invention]
However, the conventional ion drift type flow meter 1 has the following problems to be solved.
[0006]
That is, since the conventional ion drift type flow meter depends on a manufacturing method on the premise of machining and assembly, there is a limit to downsizing, and the measurement object is restricted in terms of size. Further, in order to accurately measure the arrival position of ions, high processing accuracy and assembly accuracy are required, and therefore high cost is required. Furthermore, since this type of flow meter generally requires an electric field sufficient to break the dielectric strength of air, a high voltage source is required, which also increases costs.
[0007]
Accordingly, an object of the present invention is to provide an ion drift type flow meter that solves the above-described problems, is low in cost, has high performance, and can be further downsized.
[0008]
[Means for Solving the Problems]
In order to solve the problems described above, in the present invention, the invention according to claim 1 is an ion drift type flow meter, which is formed in a strip shape on a substrate and has one end sharpened and the other end Are connected to an external power source through pads, and a first collector electrode and a second collector that are opposed to each other and are connected to each pad and grounded from each pad through current detection means, respectively. The collector electrode, and the corona electrode, the first collector electrode and the second collector electrode are a metal conductive thin film formed by photolithography or silicon subjected to impurity diffusion, and the corona electrode Each pad of the pad, the first collector electrode, and the second collector electrode is a metal thin film that can be bonded, and is formed by photolithography. Characterized in that it is.
[0009]
According to a second aspect of the present invention, in the ion drift flowmeter, a spacer member laminated on one end side of the substrate on the substrate, one end side placed on the spacer member, and the other end side from the spacer member A beam member projecting in a tapered manner, a corona electrode provided along a projecting portion of the beam member between the spacer member and the beam member, and a portion opposite to the one end side where the spacer member is laminated And a corona electrode, a first collector electrode, and a second collector electrode are formed of a metal conductive thin film formed by photolithography or the like. The impurity-diffused silicon is formed, and the first collector electrode and the second collector electrode are formed by photolithography, and one end of each other There, characterized in that it is spaced apart in parallel along the extension direction of the free end of the corona electrode.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
<First Embodiment>
An example of an ion drift type flow meter according to the present invention will be described with reference to FIG. 1A is a schematic plan view of an ion drift flow meter, FIG. 1B is a schematic cross-sectional view taken along line II ′ of FIG. 1A, and reference numeral 2 in the drawing is an ion drift type. Indicates a flow meter. Further, in the figure, the flow of ions is indicated by broken lines and black dots.
[0019]
The ion drift type flow meter 2 is formed in a strip shape on the substrate 20 and connected to an external power source (not shown) through one end (hereinafter also simply referred to as a tip) having a sharp end and a pad 23. A corona electrode 21 having an end, and two collector electrodes 22a and 22b that are opposed to each other and are connected to pads 24a and 24b and grounded via a current detection means, respectively.
[0020]
Next, the operation of the ion drift type flow meter having the above configuration will be described. This ion drift type flow meter is placed in an air flow flowing from the direction of arrow A as shown in FIG. When an appropriate voltage is applied to the corona electrode 21, an unequal electric field is formed between the collector electrodes 22a and 22b, a corona discharge is generated at the tip of the corona electrode 21, and the fluid or fluid passing through the ion drift flow meter. The particles are ionized. The ionized fluid molecules drift to the collector electrodes 22a and 22b. At this time, depending on the flow of fluid, since the ions reach more to the downstream side 22b relative to the collector electrode 22a of the upstream side, the current I _b is increased compared to the current I _a, the flow rate or by taking the ratio The flow rate can be detected.
[0021]
In addition, the said board | substrate 20 can make the insulating layer formed on the glass substrate or the silicon substrate, for example. The electrodes 21, 22 a, and 22 b are conductive thin films such as metals formed by photolithography, silicon subjected to impurity diffusion, or the like. When the electrode surface is oxidized by corona discharge, it is effective to use an oxidation-resistant metal material such as Pt. Furthermore, the electrode pads 23, 24a, and 24b are suitably metal thin films that can be bonded, and can be formed by photolithography.
[0022]
If necessary, the magnetic flux B generated by a magnet or induction intersects the flow of ions (indicated by a broken line in the figure) between the corona electrode 21 and the collector electrodes 22a and 22b as shown in FIG. If so, the electric field is bent, and the flow of ions rises more from the substrate, making it easier to capture the flow of fluid. At the same time, the electric field concentration at the edge on the collector electrodes 22a and 22b side can be relaxed, so that the inequality of the electric field is further increased and the corona discharge is stabilized.
[0023]
As described above, if an ion drift flow meter is formed on a substrate using photolithography, an ion drift flow meter with a very small size can be obtained. Measurement can be performed. Further, since the gap between the electrodes can be shortened, the electric field can be increased, the applied voltage can be reduced as compared with the conventional case, and the cost of the power supply portion can be suppressed. Since a batch process by photolithography is used for the production, the production cost can be reduced due to the mass production effect. Further, since high-precision processing is possible without requiring assembly, the dimensions and position accuracy of the electrodes can be increased, and the flow rate detection accuracy can be increased relatively easily.
[0024]
<Second Embodiment>
A second embodiment of an ion drift flow meter according to the present invention will be described with reference to FIG. 2A is a schematic plan view of an ion drift flow meter, FIG. 2B is a schematic cross-sectional view taken along the line II-II ′ of FIG. 2A, and reference numeral 3 in the drawing is an ion drift type. Indicates a flow meter. In the figure, broken lines and black dots indicate ion flows. An arrow A indicates the direction of fluid flow.
[0025]
The ion drift type flow meter 3 is erected in the center of the substrate 30 and is cut out in an arc shape so as to be spaced apart from the corona electrode 31 formed in a conical shape and the peripheral surface of the corona electrode 31 at a predetermined interval. The two collector electrodes 32a and 32b are disposed on the substrate 30 via an insulating layer 33 so that one ends thereof are opposed to each other. The conical corona electrode 31 can be formed by, for example, silicon etching or metal deposition. If a voltage is applied to the corona electrode 31 and the collector electrodes 32a and 32b are grounded, an ion flow is formed between the corona electrode 31 and the collector electrodes 32a and 32b. Under the same principle and effect as in the first embodiment, The flow rate or flow rate can be measured.
[0026]
<Third Embodiment>
A third embodiment of the ion drift flow meter according to the present invention will be described with reference to FIG. 3A is a schematic plan view of an ion drift flow meter, FIG. 3B is a schematic cross-sectional view taken along the line II-II ′ of FIG. 3A, and reference numeral 4 in the drawing is an ion drift type. Indicates a flow meter. In the figure, broken lines and black dots indicate ion flows. An arrow A indicates the direction of fluid flow.
[0027]
The ion drift type flow meter 4 includes a substrate 40, a spacer member 41 laminated on one end side of the substrate, one end side placed on the spacer member 41, and the other end side tapered from the spacer member 41. And a corona electrode 43 provided between the spacer member 41 and the beam member 42 and provided along the protruding portion of the beam member 42.
[0028]
The substrate 40, the spacer member 41, and the beam member 42 are made of a substrate such as glass or silicon, and can be laminated by an appropriate bonding method. On the substrate 40, two collector electrodes 45a and 45b are arranged on a portion opposite to the one end side where the spacer member 41 is laminated. These collector electrodes 45a and 45b have a rectangular shape and are spaced apart in parallel along the direction of the extension of the free end of the corona electrode 43 whose one end is tapered in two stages. If a voltage is applied to the corona electrode 43 and the collector electrodes 45a and 45b are grounded, an ion flow is formed between the corona electrode 43 and the collector electrodes 45a and 45b, and the same principle and effect as in the first embodiment are achieved. Below the fluid flow rate or flow rate can be measured.
[0029]
【The invention's effect】
As described above, the ion drift type flow meter based on the present invention can obtain an ion drift type flow meter of a minute size compared with the conventional one, without being subjected to spatial restrictions on the measurement target. Since the flow rate can be measured and the gap between the electrodes can be shortened, the electric field can be increased, the applied voltage can be reduced compared to the conventional case, and the cost of the power supply part can be reduced. Since the process can be used, the production cost can be reduced due to the mass production effect, and high-precision machining is possible without assembling. Therefore, the dimensions and position accuracy of the electrodes are increased and the flow rate is relatively easy. It becomes possible to improve detection accuracy.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a first embodiment of an ion drift type flow meter according to the present invention, wherein (a) is a schematic plan view of the ion drift type flow meter, and (b) is (a). FIG. 2 is a schematic cross-sectional view taken along the line II ′.
FIGS. 2A and 2B are diagrams for explaining a second embodiment of the ion drift type flow meter according to the present invention, FIG. 2A is a schematic plan view of the ion drift type flow meter, and FIG. FIG. 2 is a schematic cross-sectional view taken along line II-II ′.
FIGS. 3A and 3B are diagrams for explaining a third embodiment of the ion drift flow meter according to the present invention, wherein FIG. 3A is a schematic plan view of the ion drift flow meter, and FIG. FIG. 3 is a schematic cross-sectional view taken along line III-III ′.
FIG. 4 is a schematic diagram for explaining a conventional ion drift flow meter.
[Explanation of symbols]
2 Ion drift type flow meter 3 Ion drift type flow meter 4 Ion drift type flow meter 20 Substrate 21 Corona electrodes 22a and 22b Collector electrodes 23, 24a and 24b Electrode pad 30 Substrate 31 Corona electrodes 32a and 32b Collector electrode 33 Insulating layer 40 Substrate 41 spacer member 42 beam member 43 corona electrode 45a, 45b collector electrode

Claims (2)

On the substrate, a corona electrode formed in a strip shape and having one end sharpened and the other end connected to an external power source through a pad is opposed to each other, and each is connected to each pad, A first collector electrode and a second collector electrode each grounded from the pad via current detection means,
The corona electrode, the first collector electrode, and the second collector electrode are a metal conductive thin film formed by photolithography or silicon subjected to impurity diffusion, and the corona electrode pad, The ion drift type flow meter, wherein each pad of the first collector electrode and the second collector electrode is a metal thin film that can be bonded and is formed by photolithography. A spacer member laminated on one end side of the substrate on the substrate; a beam member having one end side placed on the spacer member and the other end side protruding from the spacer member; and the spacer A corona electrode provided along a protruding portion of the beam member between the member and the beam member, and a first portion having a rectangular shape on a portion opposite to the one end side where the spacer member is laminated A collector electrode and a second collector electrode;
The corona electrode, the first collector electrode and the second collector electrode are a metal conductive thin film formed by photolithography or silicon subjected to impurity diffusion, and the first collector electrode and The second collector electrode is formed by photolithography, and one end portions of the second collector electrode are spaced apart in parallel along the extension line direction of the free end of the corona electrode. Total.

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