JPH09304209A - Capacitive pressure sensor and gas abnormality monitoring device using this sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure wherein a seal material and a diaphragm are not in contact with each other for reducing temperature characteristics and characteristic fluctuation by interposing the seal material between a fixed substrate of a sensor element and a case for fixing the sensor element to the case. SOLUTION: A sensor element 1 comprises a diaphragm 2 with a first electrode 1 formed on a surface, a fixed substrate 5 equipped with a vent hole 4 formed with a second electrode 3 on a surface and an adhesive layer 6 for oppositely placing the first electrode 1 and the second electrode 3, holding the diaphragm 2 and the fixed substrate 5 at a constant distance and sticking them, and the element is enclosed by a case 8 having a pressure lead hole. A seal material 9 is interposed between the fixed substrate 5 of the sensor element and the case 8 to fix the sensor element to the case 8, so that the seal material 9 may not be in contact with the diaphragm 2. Thus since influence of a very slight load at the time of fixing may not be applied, fluctuation in sensor characteristics can be eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance type pressure sensor and a gas abnormality monitoring device such as a gas pressure regulator or a gas meter using the sensor.

[0002]

2. Description of the Related Art In recent years, in order to improve the safety of city gas or LP gas equipment, for example, in the case of a gas meter, when it is desired to multiply from the gas meter on the downstream side,
It has been considered to incorporate a gas abnormality monitoring device that automatically shuts off gas supply into a gas meter. In addition, regarding the pressure regulator, abnormal adjustment pressure of the pressure adjusting means and LP
Incorporation of a gas abnormality monitoring device that can automatically check safety management such as gas leak detection from a gas cylinder to a gas meter is under consideration. When the pressure adjusting function of the LP gas pressure adjuster is operating normally, the gas supply pressure is maintained between 230 and 330 mmH2O when the gas appliance is in use. Therefore, whether or not the gas supply pressure is normal can be automatically determined by monitoring the supply pressure with a pressure sensor.

Regarding the presence or absence of an abnormality such as a gas leak in the gas facility, for example, a gas valve is closed by a shutoff valve or the like, and if there is a gas leak, the gas pressure is gradually reduced (several mmH2O
If there is no gas leakage, there will be no such deterioration phenomenon.

Therefore, by monitoring the presence or absence of the decrease in gas pressure with the pressure sensor, it is possible to automatically detect the presence or absence of an abnormality such as a gas leak in the gas facility. As a conventional pressure sensor for detecting these pressures with high accuracy and in a short time, the one disclosed in JP-A-58-731 is generally used.
The configuration will be described below with reference to FIG.

As shown in FIG. 10, a conventional capacitance type pressure sensor has a diaphragm 2 having a first electrode 1 formed on its surface and a second electrode 3 having a surface formed with a ventilation hole 4. The fixed substrate 5 is provided, the first electrode 1 and the second electrode 3 are arranged to face each other, and the adhesive layer 6 is provided on the outer peripheral portion of the electrode.
The sensor element is formed by holding and adhering it at a constant interval by means of a sealing member 9 provided on the diaphragm 2 of the sensor element to keep the sensor element airtight and casing.

Further, by providing the sensor element with the converting means 10 for converting the electrostatic capacity into an electric signal through the connecting portion 7, the capacity is converted into a voltage value, a frequency value or the like and the electrostatic capacity type pressure sensor. Was installed in other equipment, such as a gas meter, and was widely used. Further, it is desired that these devices normally operate on batteries for 10 years or more, and that the pressure sensors have low power consumption so that they can be battery-operated for 10 years.

[0007]

However, conventionally, the gas pressure can be detected with high accuracy so that it can be used in a gas abnormality monitoring device such as a pressure regulator and a gas meter, and the accuracy does not change over a long period of time. There was no high-performance / high-reliability pressure sensor.
In other words, the electrostatic capacitance type pressure sensor is
H2O) to detect with high sensitivity, diaphragm 2
It is necessary to reduce the thickness to about several hundred μm. FIG.
In the conventional electrostatic capacitance type pressure sensor shown in, when the distance between the first electrode 1 and the second electrode 3 is very small, about 1 to 30 μm, in order to achieve high sensitivity and high accuracy, it is very small. Variations in the electrode spacing cause variations and variations in capacitance. Similarly, when the thickness of the diaphragm 2 is reduced, the above-mentioned tendency becomes large. Furthermore, when the case 8 is fixed onto the diaphragm 2, a slight stress from the seal material 9 reacts with the output, causing variations in individual sensor characteristics. Also, as the temperature changes,
The sealing material 9 expands and contracts, the diaphragm 2 fluctuates slightly, and the electrode spacing between the first electrode 1 and the second electrode 3 fluctuates. Therefore, the output capacitance value fluctuates. As a result, there is a problem that the output depends on the temperature.

Further, when the accuracy of the pressure sensor is low, when detecting an abnormality such as a gas leak in the gas equipment, if the time for pressure measurement and the time for determining normality / abnormality become long, the pressure sensor may not operate and operate. There is a problem that the power consumption increases according to the amount of time that the battery is used and the battery drains quickly.

Further, if there are many variations in the characteristics of the pressure sensor, it is necessary to adjust the pressure sensor, resulting in poor mass productivity and high manufacturing cost.

[0010]

In order to solve the above problems, a capacitance type pressure sensor of the present invention has a diaphragm having a first electrode formed on the surface thereof and a second electrode formed on the surface thereof. A sensor element comprising a fixed substrate and the first electrode and the second electrode are arranged to face each other, and an adhesive layer that holds and bonds the diaphragm and the fixed substrate at a constant interval,
A case having a pressure introducing hole and enclosing the sensor element, the sensor element is fixed to the case by interposing a seal material between the fixed substrate of the sensor element and the case, and a seal material and a diaphragm. Are not in contact with each other.

As a result, the temperature characteristic is reduced, the characteristic variation is reduced, and therefore the accuracy and the mass productivity are improved.

Further, in the gas abnormality monitoring device, the accuracy of the pressure detecting means for detecting the gas pressure in the gas equipment is improved, and the time for judging an abnormality such as gas leakage in the gas equipment is shortened, so that the battery The consumption can be suppressed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a diaphragm having a first electrode formed on the surface thereof, a fixed substrate having a second electrode formed on the surface thereof, and the first electrode and the second electrode opposed to each other. The sensor element is provided and is provided with a sensor element including an adhesive layer that holds and bonds the diaphragm and the fixed substrate at a constant interval, and a case having a pressure introducing hole and enclosing the sensor element, and the sensor element is fixed to the case. In order to achieve this, a sealing material is provided between the fixed substrate of the sensor element and the case.

Since the sealing material used for fixing the sensor element and the case is provided on the side surface of the fixed substrate so as not to contact the diaphragm, the temperature characteristic of the sealing material is not affected, so that the temperature of the pressure sensor is not affected. The characteristics can be reduced. Further, since no stress is applied, variations in characteristics can be suppressed, which improves mass productivity.

Further, the sealing material is provided on the opposite side of the fixed substrate on which the second electrode is formed.

Further, an upper cutout is provided in the upper part of the outer peripheral edge of the fixed substrate, and a sealing material is interposed in the upper cutout.

Further, a lower cutout is provided in the lower portion of the outer peripheral edge of the fixed substrate, and a sealing material is interposed in the lower cutout.

Further, an upper cutout and a lower cutout are provided in the upper and lower portions of the outer peripheral edge of the fixed substrate, respectively, and a sealing material is interposed in the upper cutout and the lower cutout.

Further, the inner surface of the case and the outer peripheral end surface of the fixed substrate are tapered so that the sealing material has a substantially triangular cross-sectional shape.

Further, a concave portion is provided on the outer peripheral end surface of the fixed substrate,
A sealing material is interposed in this recess.

Further, pressure detecting means for detecting the gas pressure in the gas equipment using the above capacitance type pressure sensor, flow rate detecting means for detecting the gas flow rate in the gas equipment, the pressure detecting means and the flow rate. It is a gas abnormality monitoring device provided with a judging means for judging an abnormality in a gas facility by an electric signal from the detecting means, and an operating means for operating according to a signal from the judging means.

By improving the detection accuracy of the pressure detecting means for detecting the gas pressure in the gas equipment, the time for judging an abnormality such as a gas leak can be shortened, so that the consumption of the battery can be suppressed. You can

(Embodiment 1) Hereinafter, Embodiment 1 of the present invention will be described with reference to FIG.

FIG. 1 is a sectional view of a capacitance type pressure sensor according to the present invention. The same components as those of the conventional example are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 1, a diaphragm 2 having a first electrode 1 formed on the surface thereof, a fixed substrate 4 having a vent hole 4 having a second electrode 3 formed on the surface thereof, and the first electrode. 1 and the second electrode 3 are opposed to each other, and a sensor element composed of an adhesive layer 6 for adhering and holding the diaphragm 1 and the fixed substrate 4 at a constant interval and a sensor element having a pressure introducing hole are provided. A sealing member 9 is provided between the fixed substrate 4 of the sensor element and the case 8 to fix the sensor element to the case.
Is configured so as not to contact the diaphragm 2. Further, the second electrode 3 and the conversion means 10 for converting the capacitance into an electric signal are connected by the connecting portion 7.

When the capacitance type pressure sensor of the present invention is used to measure a pressure of 0 to 500 mmH2O in an environment of 30 degrees, it is 0.5
It was possible to measure with an accuracy of% full scale (2.5 mmH2O).

Further, the pressure of 0 to 500 mmH2O was similarly measured under the environment of -30 ° C and 60 ° C, and it was possible to measure with the accuracy of 0.5 full scale as in the case of measuring at 30 ° C. Furthermore, the output change of 0 mmH2O at -30 degrees and 60 degrees was only about 0.1%.

(Embodiment 2) FIG. 2 shows a static pressure sensor according to the present invention in which the sealing material 9 of the capacitance type pressure sensor described in Embodiment 1 is provided on the opposite side of the fixed substrate 4 on which the second electrode 3 is formed. A capacitance type pressure sensor is shown. The other structure is the same as that of the first embodiment. When a pressure of 0 to 500 mmH2O is measured under the environment of 30 degrees in the same manner as in Example 1 using the above capacitance type pressure sensor, it is 0.5
It was possible to measure with an accuracy of% full scale (2.5 mmH2O).

Further, the pressure of 0 to 500 mmH2O was similarly measured under the environment of -30 degrees and 60 degrees, but it was possible to measure with the accuracy of 0.5 full scale as in the case of measuring at 30 degrees. Furthermore, the output change of 0 mmH2O at -30 degrees and 60 degrees was only about 0.1%.

(Third Embodiment) FIG. 3 shows the fixed substrate 5 of the first embodiment.
An electrostatic capacity type pressure sensor is shown in which an upper notch is provided at the upper part of the outer peripheral end of the and the seal material 9 is interposed in the upper notch. At this time, the fixed substrate 4 was manufactured by molding. In the case of the above configuration, even when a large amount of the sealing material 9 is applied, the sealing material 9 flows into the upper notch when the case 8 is set, so that the sealing material 9 does not contact the diaphragm 2. When the pressure of 0 to 500 mmH2O is measured with the above capacitance type pressure sensor in the environment of 30 degrees as in the case of Example 1, it can be measured with the accuracy of 0.5% full scale (2.5 mmH2O), and- A pressure of 0 to 500 mmH2O was similarly measured under the environment of 30 ° and 60 °, but it was possible to measure with the accuracy of 0.5 full scale as in the case of measuring at 30 °. Further, the output change of 0 mmH2O at -30 degrees and 60 degrees was only about 0.1%, and the same effect as in Example 1 was obtained.

(Embodiment 4) FIG. 4 shows a capacitance type pressure sensor in which a lower cutout is provided in the lower portion of the outer peripheral edge of the fixed substrate 4, and a sealing material 9 is interposed in the lower cutout. Example 3
Similarly to the above, the fixed substrate 4 was manufactured by die molding. Example 1
As a result of evaluation in the same manner as above, the same results as in Examples 1 to 3 were obtained.

(Embodiment 5) In FIG. 5, an upper cutout and a lower cutout are provided in the upper and lower portions of the outer peripheral edge of the fixed substrate 4, and a sealing material 9 is interposed in the upper cutout and the lower cutout. 1 shows a capacitance type pressure sensor.

As a result of performing the same evaluation as in Example 1, the same results as in Examples 1 to 4 were obtained. (Embodiment 6) FIG. 6 shows an electrostatic capacitance type pressure sensor in which the inner surface of the case 8 and the outer peripheral end surface of the fixed substrate 4 are tapered so that the cross-sectional shape of the sealing material 9 is substantially triangular. FIG.
By providing the fixed substrate 4 and the case 8 with a taper as shown in FIG. 3, it becomes easy to determine the position when the sensor element is installed in the case 8. In other words, conventionally, the convex portion is provided inside the case 8 and the position is determined by contacting the surface of the fixed substrate 5, so that the diaphragm 2 is easily contacted,
The molding of the case required considerable precision. However, in the structure of this embodiment, the side surface of the fixed substrate 5 can be positioned, so that the structure of the case 8 can be simply formed by tapering. Further, since the case 8 and the diaphragm 2 are not in contact with each other and the contact area with the case 8 is increased, the sealing property is improved, and the same evaluation as in Example 1 is performed. Was obtained.

(Embodiment 7) FIG. 7 shows a capacitance type pressure sensor in which a concave portion is provided on the outer peripheral end surface of the fixed substrate 4 and a sealing material is interposed in the concave portion. As a result of performing the same evaluation as in Example 1, the same results as in Examples 1 to 6 were obtained.

(Embodiment 8) FIG. 8 is a block diagram when the gas abnormality monitoring device of the present invention is applied to a pressure regulator. In FIG. 8, 31 is a gas supply source, 32 is a pressure regulator, and 33 is a gas meter. The pressure regulator 32 includes a pressure regulator 40 and a pressure detector 41 (for example, a pressure sensor).
And flow rate detection means 42 (for example, a flow meter) and determination means 43
(For example, a microcomputer) and output means 44 (for example, a shutoff valve).

FIG. 9 is a flow chart showing the gas leak detection operation of the pressure regulator. In a state where the present apparatus is started, the output means 44 (for example, a shutoff valve) is operated (step 1), and the gas pressure supplied from the gas supply source 31 and adjusted by the pressure adjusting means 40 is detected by the pressure detecting means 41. Is measured (step 2), and the flow rate is detected by the flow rate detecting means 42 to confirm that the gas flow rate is 0 (step 3).

If a small amount of gas is leaking, the gas pressure in the pipe gradually decreases with time when the gas flow rate is 0. Therefore, the change in gas pressure is monitored by the pressure detecting means 41, and the microcomputer or the like is used. If the pressure drop is larger than a predetermined value, it is judged that there is a gas leak (step 4). When it is judged that there is a gas leak, the output means 44 (for example, a shutoff valve) is operated to stop the gas supply (step 5). If the gas equipment is inspected and the abnormality is removed or it is confirmed that there is no abnormality, the operation returns to the output operation (step 1) again, and the measurement / judgment is continuously performed for a long period of time. Monitor for gas leaks.

As the pressure detecting means 41, the first to eighth embodiments
When using the capacitance type pressure sensor of the present invention described in,
Shutoff valve 44, flow rate detection means 42, and pressure detection means 41
The gas pressure of the pressure regulator 32 is 315 mmH2O.
What was (measured with another standard pressure sensor) was used to measure the minute pressure fluctuation in the pipe (305mmH2O decreased to 295mmH2O), and the minute gas leak in the gas pipe was judged in about 20 seconds. I was able to. In addition, this measurement is -3
Gas leaks could be determined in about 20 seconds at both temperatures, even at 0 and 60 degrees. Since it was possible to detect and discriminate the gas pressure fluctuation in a short time, it was possible to reduce the power consumption as the pressure sensor and the gas abnormality monitoring device, and it was not necessary to replace the battery for 10 years. Further, since the characteristic variation of the pressure sensor is small, the manufacturing cost is about half that of the conventional one.

(Comparative Example) A diaphragm 2 (for example, alumina, thickness 150 μm) having a first electrode 1 formed on the surface thereof.
And a fixed substrate 5 of a fixed substrate 5 (for example, alumina) provided with a vent hole 4 in which the second electrode 3 is formed, the first electrode 1 and the second electrode 3 are arranged to face each other, and the outer periphery of the electrode is provided. The sensor element is composed of an adhesive layer 6 (for example, a glass frit) that holds the diaphragm 2 and the fixed substrate 5 at a constant interval and adheres them to each other, and the sensor element is connected to the conversion means 12 by the connecting portion 7. It The sensor element is casing in a case having a pressure introducing hole and enclosing the sensor element, and the casing is fixed by a sealing material 9 interposed between the diaphragm 2 and the case.

The charging / discharging time detection type detection circuit used in Example 1 was connected to perform non-linearity correction, gain and offset adjustment, and a predetermined voltage output was converted. 0-500mmH2O
Was measured, but it could be measured only with an accuracy of 4.3% full scale at -30 degrees and with 3.9% full scale at 60 degrees. The output change of 0 mmH2O at -30 degrees and 60 degrees was about 2.3%.

When this capacitance type pressure sensor is incorporated as the pressure detecting means 41 of the same gas meter as in the second embodiment, the gas pressure of the gas meter 33 is 250 mmH2O (measured by another standard pressure sensor). By operating the shutoff valve 34, the flow rate detecting means 32, and the pressure detecting means 41 to detect a minute pressure fluctuation in the pipe (250 mmH2O drops to 230 mmH2O) in about 20 seconds, it is determined that a minute gas leak has occurred. I couldn't. Therefore, when the minute pressure fluctuation in the pipe was set to 50 mmH2O (250 mmH2O decreased to 200 mmH2O), it was possible to accurately determine that there was a minute gas leak in the gas pipe, but it took about 90 seconds until the determination. The battery life was about 7.5 years.

[0042]

As is apparent from the above description, the following effects can be obtained by the capacitance type pressure sensor of the present invention and the gas abnormality monitoring device using this sensor.

In the capacitance type pressure sensor of the present invention,
When the sensor element and the case having the pressure introducing hole and enclosing the sensor element are fixed by a sealing material interposed between the fixed substrate of the sensor element and the case, the fixing is very small. Since it is not affected by a slight load, there is no variation in sensor characteristics, and manufacturing costs can be reduced. Furthermore, since the diaphragm is not affected by expansion and contraction due to the temperature characteristics of the seal material, the sensor output does not depend on temperature, and the accuracy of the pressure sensor is improved.

The same effect can be obtained by providing the sealing material on the opposite side of the fixed substrate on which the second electrode is formed.

Further, an upper notch is provided at the upper part of the outer peripheral edge of the fixed substrate, a lower notch is provided at the lower part, or both are provided.
By interposing the sealing material in the cutout portion, the contact area between the fixed substrate and the sealing material increases, so that the sealing property also increases. Further, variations in sensor characteristics can be suppressed and temperature characteristics can be reduced.

Further, when the inner surface of the case and the outer peripheral end surface of the fixed substrate are tapered so that the cross-sectional shape of the sealing material is substantially triangular, it is easy to position the sensor element in the case. become. Further, since the case and the diaphragm are not in contact with each other, variations in characteristics and temperature characteristics are reduced, and a contact area with the case is increased, so that sealing performance is improved.

Further, in the gas abnormality monitoring device using the electrostatic capacity type pressure sensor, it is possible to shorten the determination time of abnormality such as gas leakage in the gas facility.

Further, it is possible to suppress the consumption of the battery that drives the gas abnormality monitoring device. Further, the manufacturing cost of the gas abnormality monitoring device can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view of a capacitance type pressure sensor according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a capacitance type pressure sensor according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a capacitance type pressure sensor according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a capacitance type pressure sensor according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a capacitance type pressure sensor according to a fifth embodiment of the present invention.

FIG. 6 is a sectional view of a capacitance type pressure sensor according to a sixth embodiment of the present invention.

FIG. 7 is a sectional view of a capacitance type pressure sensor according to a seventh embodiment of the present invention.

FIG. 8 is a block diagram showing a pressure regulator as a gas abnormality monitoring device according to an eighth embodiment of the present invention.

FIG. 9 is a flowchart of the pressure regulator.

FIG. 10 is a sectional view of a conventional capacitance type pressure sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st electrode 2 Diaphragm 3 2nd electrode 4 Fixed substrate 5 Vent hole 6 Adhesive layer 7 Converting means 8 Case 9 Sealing material

Claims (8)

[Claims] 1. A diaphragm having a surface on which a first electrode is formed, a fixed substrate having a surface on which a second electrode is formed, and the first electrode and the second electrode are arranged so as to face each other. A sensor element including an adhesive layer that holds and adheres a fixed substrate at a fixed interval, and a case having a pressure introducing hole and enclosing the sensor element, and a seal is provided between the fixed substrate of the sensor element and the case. A capacitance type pressure sensor in which the sensor element is fixed to the case with a material interposed. 2. A capacitance type pressure sensor according to claim 1, wherein the sealing material is provided on the opposite side of the fixed substrate on which the second electrode is formed. 3. The capacitance type pressure sensor according to claim 1, wherein an upper cutout is provided at an upper portion of an outer peripheral end of the fixed substrate, and a seal material is interposed in the upper cutout. 4. A capacitance type pressure sensor according to claim 1, wherein a lower cutout portion is provided in a lower portion of an outer peripheral edge of the fixed substrate, and a sealing material is interposed in the lower cutout portion. 5. A capacitance type apparatus according to claim 1, wherein an upper notch and a lower notch are provided at an upper portion and a lower portion of an outer peripheral end of the fixed substrate, respectively, and a sealing material is interposed between the upper notch and the lower notch. Pressure sensor. 6. The capacitance type pressure sensor according to claim 1, wherein the inner surface of the case and the outer peripheral end surface of the fixed substrate are tapered so that the cross-sectional shape of the sealing material is substantially triangular. 7. A capacitance type pressure sensor according to claim 1, wherein a concave portion is provided on an outer peripheral end surface of the fixed substrate, and a sealing material is interposed in the concave portion. 8. A pressure detecting means for detecting gas pressure in a gas facility using the capacitance type pressure sensor according to claim 1, and a gas flow rate in the gas facility. Gas abnormality monitoring device including flow rate detection means, determination means for determining abnormality in the gas facility based on electric signals from the pressure detection means and the flow rate detection means, and operation means operated by a signal from the determination means .