JP6882220B2 - Gas sensor - Google Patents

Description

The present disclosure relates to gas sensors.

As a gas sensor that detects flammable gas and the like, a gas sensor that is not affected by moisture is known (see Patent Document 1). In the gas sensor of Patent Document 1, one gas detection element is arranged in a space open to the gas to be detected, and another gas detection element is arranged in a space covered with a membrane that allows water vapor to permeate and does not permeate the gas to be detected. To.

As a result, in the gas sensor of Patent Document 1, since the humidity conditions of the pair of gas detection elements are the same, gas can be detected without being affected by the humidity.

Japanese Unexamined Patent Publication No. 2001-124716

In the gas sensor, if the spaces in which the pair of gas detection elements are arranged are separated from each other, the atmospheric temperature difference between the pair of gas detection elements may become large due to the temperature change of the environment. If the temperature difference between the pair of gas detection elements becomes large in this way, the error in the sensor output becomes large.

One aspect of the present disclosure is to provide a gas sensor capable of suppressing an increase in an error in sensor output with respect to a temperature change.

One aspect of the present disclosure is a gas sensor for detecting gas in the atmosphere to be detected. The gas sensor includes a first gas detection element, a second gas detection element, a first storage unit having a first internal space in which the first gas detection element is stored, and a second internal space in which the second gas detection element is stored. A circuit board that applies a voltage to the second storage unit having the above, the casing in which the first storage unit and the second storage unit are housed, the heat generation resistor of the first gas detection element, and the heat generation resistor of the second gas detection element. And a calculation unit that calculates the concentration of gas in the detected atmosphere. The first gas detection element and the second gas detection element are heat conduction type detection elements each having a heat generating resistor whose resistance value changes according to its own temperature change. The casing has an opening for introducing the gas to be detected inside. The first storage unit has a first gas introduction port. The first gas introduction port communicates with the first internal space and the inside of the casing, and is covered with a film body that allows water vapor to permeate and substantially impermeable to the gas to be detected. The second storage unit has a second gas introduction port. The second gas introduction port introduces the gas to be detected from the inside of the casing into the second internal space. The calculation unit calculates the concentration from the potential between the two heat generating resistors when a constant voltage is applied to the two heat generating resistors connected in series. Further, the first storage unit and the first storage portion are located at positions where the maximum value of the temperature difference between the first internal space and the second internal space is 0.4 ° C. or less when the ambient temperature is changed from 0 ° C. to 80 ° C. Two storage units are arranged.

According to such a configuration, even if the temperature of the environment changes, the temperature difference between the first internal space in which the first gas detection element is arranged and the second internal space in which the second gas detection element is arranged is large. Keeps small. That is, the measurement conditions of the first gas detection element and the second gas detection element are close to each other. As a result, the output fluctuation with respect to the temperature change becomes small, and the error of the sensor output is reduced. In addition, the calculation unit can accurately output the concentration of the gas to be detected.

In one aspect of the present disclosure, the first storage unit is a pedestal that defines a first internal space and a second internal space with a ceramic pedestal on which the first gas detection element and the second gas detection element are mounted. It may have a ceramic protective cap that covers the. According to such a configuration, the difference in the thermal expansion rate between the pedestal and the protective cap becomes small, and it is suppressed that the adhesion between the pedestal and the protective cap is lowered due to the thermal impact. Further, according to such a configuration, the first storage portion and the second storage portion can be easily formed at the same time. As a result, since the first internal space and the second internal space can be arranged close to each other, the temperature difference between the first internal space and the second internal space can be reduced.

In one aspect of the present disclosure, the casing may have a filter that is placed in the opening and is permeable to the gas to be detected and impermeable to liquid water. According to such a configuration, the influence of the flow velocity of the detected gas is suppressed, so that the accuracy of the sensor output can be improved.

It is a schematic cross-sectional view which shows the gas sensor of embodiment. It is a schematic partially enlarged sectional view in the vicinity of the 1st storage part and the 2nd storage part of the gas sensor of FIG. It is a schematic plan view of the gas detection element of the gas sensor of FIG. FIG. 3 is a schematic cross-sectional view taken along the line VI-VI of FIG. It is a schematic circuit diagram of the gas sensor of FIG. FIG. 6A is a graph showing the change in the temperature difference between the first internal space and the second internal space when the atmospheric temperature is changed from 0 ° C. to 80 ° C., and FIG. 6B is a graph showing the atmospheric temperature from −40 ° C. It is a graph which shows the change of the temperature difference between the 1st internal space and the 2nd internal space when it changed to 100 degreeC, and FIG. 6C is the 1st when the atmospheric temperature was changed from 100 degreeC to -40 degreeC. It is a graph which shows the change of the temperature difference between the internal space and the 2nd internal space, and FIG. 6D shows the temperature difference between the 1st internal space and the 2nd internal space when the ambient temperature is changed from 80 degreeC to 0 degreeC. It is a graph which shows the change of. It is a graph which shows the relationship between the temperature difference between the 1st internal space and the 2nd internal space, and the output error of a gas sensor.

Hereinafter, embodiments to which the present disclosure has been applied will be described with reference to the drawings.
[1. First Embodiment]
[1-1. Constitution]
The gas sensor 1 shown in FIG. 1 is a gas sensor for detecting gas in the atmosphere to be detected. Examples of the gas to be detected by the gas sensor 1 include flammable gases such as hydrogen, ammonia, carbon monoxide (CO), and hydrocarbons (HC).

As shown in FIG. 1, the gas sensor 1 includes a first gas detection element 2, a second gas detection element 3, a first storage unit 4, a second storage unit 5, a casing 6, a circuit board 10, and a calculation unit. 12 and.

<1st gas detection element and 2nd gas detection element>
The first gas detection element 2 is a heat conduction type detection element that does not react with the gas to be detected.
As shown in FIGS. 3 and 4, the first gas detection element 2 includes a heat generating resistor 20, an insulating layer 21, a wiring 22, a pair of first electrode pads 23A and 23B, and a resistance temperature detector 24. , A pair of second electrode pads 25A and 25B, and a substrate 26.

The heat generating resistor 20 is a conductor patterned in a spiral shape, and is embedded in the central portion of the insulating layer 21. Further, the wiring 22 embedded in the rectangular insulating layer 21 is electrically connected to the heat generating resistor 20. Both ends of the wiring 22 are electrically connected to the first electrode pads 23A and 23B. Therefore, the heat generating resistor 20 is electrically connected to the first electrode pads 23A and 23B.

The first electrode pads 23A and 23B are formed on the surface of the insulating layer 21. Further, one of the first electrode pads 23A and 23B is connected to the ground, and the other is connected to the circuit board 10.

A silicon substrate 26 is laminated on the surface of the insulating layer 21 opposite to the first electrode pads 23A and 23B. The substrate 26 does not exist in the region where the heat generating resistor 20 is arranged. This region is a recess 27 where the insulating layer 21 is exposed, and constitutes a diaphragm structure.

The resistance temperature detector 24 is embedded outside the heat insulating layer 21 with respect to the heat generating resistor 20 and is electrically connected to the second electrode pads 25A and 25B. Specifically, the resistance temperature detector 24 is arranged in the vicinity of one side of the insulating layer 21. Further, one of the second electrode pads 25A and 25B is connected to the ground, and the other is connected to the circuit board 10.

The heat generating resistor 20 is a member whose resistance value changes according to its own temperature change, and is made of a conductive material having a large temperature resistance coefficient. As the material of the heat generation resistor 20, for example, platinum (Pt) can be used.

Further, the resistance temperature detector 24 is made of a conductive material whose resistance value changes in proportion to the temperature. As the material of the resistance temperature detector 24, for example, platinum (Pt) similar to that of the heat generation resistor 20 can be used. The materials of the wiring 22, the first electrode pads 23A and 23B, and the second electrode pads 25A and 25B can be the same as those of the heat generating resistor 20.

The insulating layer 21 may be formed of a single material, or may be composed of a plurality of layers using different materials. Examples of the insulating material constituting the insulating layer 21 include silicon oxide (SiO ₂ ) and silicon nitride (Si ₃ N ₄ ).

Like the first gas detecting element 2, the second gas detecting element 3 has a heat generating resistor whose resistance value changes according to its own temperature change and a resistance temperature measuring resistor. Since the configuration of the second gas detection element 3 is the same as that of the first gas detection element 2, detailed description thereof will be omitted. It is preferable that the heat-generating resistor of the first gas detection element 2 and the heat-generating resistor of the second gas detection element 3 have the same resistance value.

<1st storage unit and 2nd storage unit>
The first storage unit 4 has a first internal space 4A, a first gas introduction port 4B, and a film body 4C. Further, the first storage portion 4 has a ceramic pedestal 7 and a ceramic protective cap 8.

The film body 4C has a property of permeating water vapor and substantially impermeable to the gas to be detected. In addition, "substantially impermeable" means that the permeation amount of the detected gas (for example, hydrogen) is 1/50 or less of the permeation amount of water vapor on a volume basis.

As such a membrane body 4C, an ion exchange membrane made of fluororesin can be preferably used. Specific examples thereof include Nafion (registered trademark), Flemion (registered trademark), Aciplex (registered trademark) and the like. Further, as the membrane body 4C, a hollow fiber membrane capable of separating the gas to be detected and water vapor may be used.

The first gas detecting element 2 is housed in the first internal space 4A. Further, the first gas introduction port 4B communicates the first internal space 4A with the inside of the casing 6. Further, the membrane body 4C is arranged so as to cover and close the entire first gas introduction port 4B.

Therefore, the gas to be detected is not supplied to the first internal space 4A. Therefore, the first gas detection element 2 functions as a reference element that is not exposed to the atmosphere of the gas to be detected, but since the film body 4C permeates water vapor, the humidity conditions are the same as those of the second gas detection element 3. The first internal space 4A has no opening other than the first gas introduction port 4B.

The second storage unit 5 has a second internal space 5A and a second gas introduction port 5B. Further, the second storage unit 5 shares the ceramic pedestal 7 and the ceramic protective cap 8 with the first storage unit 4.

The second gas detecting element 3 is housed in the second internal space 5A. Further, the second gas introduction port 5B communicates the second internal space 5A with the inside of the casing 6. The film body 4C is not arranged at the second gas introduction port 5B and is open. Therefore, the gas to be detected is supplied from the inside of the casing 6 to the second internal space 5A via the second gas introduction port 5B. The second internal space 5A has no opening other than the second gas introduction port 5B.

The first internal space 4A and the second internal space 5A are each formed by covering the pedestal 7 with the protective cap 8. That is, the pedestal 7 and the protective cap 8 form the first storage unit 4 and also the second storage unit 5.

Further, the first internal space 4A and the second internal space 5A are partitioned by a wall formed by connecting the pedestal 7 and the protective cap 8. That is, the first storage unit 4 and the second storage unit 5 are provided adjacent to each other so as to share one wall.

The first storage unit 4 and the second storage unit 5 have the maximum value of the temperature difference between the first internal space 4A and the second internal space 5A when the ambient temperature is changed from 0 ° C. to 80 ° C. as described later. It is arranged at a position where T1 is 0.4 ° C. or lower.

(pedestal)
The pedestal 7 has a recess in which the first gas detection element 2 is placed and a recess in which the second gas detection element 3 is placed. Further, the pedestal 7 is installed on the surface of the circuit board 10.

The material of the pedestal 7 is ceramic. Suitable ceramics constituting the pedestal 7 include, for example, alumina. In this embodiment, the pedestal 7 is made of the same ceramic as the protective cap 8.

(Protective cap)
The protective cap 8 has two recesses defining a first interior space 4A and a second interior space 5A. The two recesses of the protective cap 8 are abutted against the two recesses of the pedestal 7, respectively. The protective cap 8 is adhered to the pedestal 7 so as to cover the pedestal 7 and the first gas detecting element 2 and the second gas detecting element 3 placed in the two recesses of the pedestal 7.

The first gas introduction port 4B and the second gas introduction port 5B are provided in the two recesses of the protective cap 8, respectively. Further, the film body 4C is fixed to the opening portion of the first gas introduction port 4B on the first internal space 4A side. Specifically, the film body 4C is adhered to the inner surface of the protective cap 8 facing the first gas detection element 2.

The material of the protective cap 8 is ceramic. Suitable ceramics constituting the protective cap 8 include, for example, alumina. As described above, in the present embodiment, the pedestal 7 and the protective cap 8 are made of the same ceramic.

(adhesive)
The pedestal 7 and the protective cap 8 are adhered to each other by the adhesive 9A. As the adhesive 9A, one containing a thermosetting resin, a thermoplastic resin or the like as a main component can be used. Among these, an adhesive containing a thermosetting resin as a main component is preferable from the viewpoint of enhancing the adhesion between the pedestal 7 and the protective cap 8. Specific examples of the thermosetting resin include epoxy resins and the like. The "main component" means a component contained in an amount of 80% by mass or more.

Further, in the present embodiment, the film body 4C is also adhered to the inner surface of the protective cap 8 by the adhesive 9B. As the adhesive 9B for adhering the film body 4C, the same adhesive 9A for adhering the pedestal 7 and the protective cap 8 can be used.

<Temperature difference when the ambient temperature is changed>
When the ambient temperature at which the gas sensor 1 is installed is changed from 0 ° C. to 80 ° C., the maximum value T1 of the temperature difference between the first internal space 4A and the second internal space 5A is 0.4 ° C. or less. Further, the maximum value T2 of the temperature difference between the first internal space 4A and the second internal space 5A when the ambient temperature is changed from 80 ° C. to 0 ° C. is also preferably 0.4 ° C. or less. Further, T1 and T2 are preferably 0.2 ° C. or lower, respectively.

In addition, the maximum value T3 of the temperature difference between the first internal space 4A and the second internal space 5A when the atmospheric temperature is changed from -40 ° C to 100 ° C, and the atmospheric temperature is changed from 100 ° C to -40 ° C. The maximum value T4 of the temperature difference between the first internal space 4A and the second internal space 5A at the time of being allowed to be allowed to be set is also preferably 0.4 ° C. or lower.

T1, T2, T3 and T4 are measured by, for example, the following procedure. First, the gas sensor is left in a constant temperature bath set to the measurement start temperature. After that, the inside of the constant temperature bath is heated or cooled, and the temperature difference between the first internal space 4A and the second internal space 5A is measured until the measurement end temperature is reached. From the measurement results, T1, T2, T3 and T4 are calculated.

The temperatures of the first internal space 4A and the second internal space 5A can be measured by the resistance temperature detectors 24 of the first gas detecting element 2 and the second gas detecting element 3, respectively. However, the temperature may be measured by means other than the resistance temperature detector 24, for example, temperature measuring elements arranged in the first internal space 4A and the second internal space 5A.

T1, T2, T3 and T4 are, for example, the distance between the first storage unit 4 and the second storage unit 5, the material of the members constituting them, and the thickness of the wall defining the first internal space 4A and the second internal space 5A. It can be made less than or equal to the above-mentioned value by adjusting

<Casing>
The casing 6 accommodates the first storage unit 4 and the second storage unit 5. The casing 6 has an opening 6A for introducing the gas to be detected inside, and a filter 6B arranged in the opening 6A.

Specifically, the first storage unit 4 and the second storage unit 5 (that is, the pedestal 7 and the protective cap 8) are housed in the internal space 6C provided between the casing 6 and the circuit board 10. The internal space 6C is formed by fixing the circuit board 10 to the inner frame 6D protruding inside the casing 6 via the seal member 11.

Further, the opening 6A is formed so as to communicate the atmosphere to be detected and the internal space 6C. The gas to be detected taken into the internal space 6C from the opening 6A is supplied only to the second internal space 5A through the second gas introduction port 5B. On the other hand, the water vapor in the internal space 6C can be diffused into both the first internal space 4A and the second internal space 5A.

The filter 6B is a water-repellent filter that permeates the gas to be detected and does not permeate the liquid water. The filter 6B suppresses the influence of the change in the flow velocity of the detected gas on the sensor output. In the present embodiment, the filter 6B is attached to the inner surface of the casing 6 so as to close the opening 6A.

<Circuit board>
The circuit board 10 is arranged in the casing 6 to form the calculation unit 12 and the circuit shown in FIG. The circuit board 10 includes a gas detection circuit C1 that applies a voltage to the heat generation resistor 20 of the first gas detection element 2 and the heat generation resistor 30 of the second gas detection element 3 and outputs a gas concentration detection signal Vd, and a temperature measurement. It has a temperature measuring circuit C2 that applies a voltage to the resistor 24 and outputs a temperature detection signal Vt indicating the temperature of the atmosphere to be detected.

<Calculation unit>
The calculation unit 12 calculates the concentration of the gas in the atmosphere to be detected. Specifically, as shown in FIG. 5, the calculation unit 12 has a constant voltage Vcc on the heat-generating resistor 20 of the first gas detection element 2 and the heat-generating resistor 30 of the second gas detection element 3 connected in series. Is applied, the concentration is calculated from the potential between the heat-generating resistor 20 of the first gas detection element 2 and the heat-generating resistor 30 of the second gas detection element 3.

More specifically, in the gas detection circuit C1, the electric potential between the heat generation resistor 20 of the first gas detection element 2 and the heat generation resistor 30 of the second gas detection element 3 and the fixed resistance R3 and the fixed resistance R4. The potential difference Vd obtained by amplifying the potential difference with the potential between them by the differential amplification circuit is output, and the concentration D calculated from Vd is output by the calculation unit 12.

A current is supplied to the arithmetic unit 12 and the circuit board 10 from the DC power supply 40. Further, the resistance temperature detectors 24 of the first gas detection element 2 and the second gas detection element 3 are connected to the calculation unit 12. A potential difference is generated by changing the resistance value of the resistance temperature detector 24 with the temperature change of the atmosphere to be detected, and the temperature measurement circuit C2 amplifies the potential difference and outputs it as a temperature detection signal Vt. Vt is converted by the calculation unit 12 into the ambient temperature T of each of the first storage unit 4 and the second storage unit 5.

[1-2. effect]
According to the embodiment described in detail above, the following effects can be obtained.
(1a) Since T1 is 0.4 ° C. or lower, the first internal space 4A in which the first gas detection element 2 is arranged and the second gas detection element 3 are arranged even if the temperature of the environment changes. The temperature difference from the second internal space 5A is kept small. That is, the measurement conditions of the first gas detection element 2 and the second gas detection element 3 are close to each other. As a result, the output fluctuation with respect to the temperature change becomes small, and the error of the sensor output is reduced.

(1b) The circuit board 10 and the calculation unit 12 calculate the gas concentration using the potential between the heat generation resistor 20 of the first gas detection element 2 and the heat generation resistor 30 of the second gas detection element 3. Therefore, the concentration of the gas to be detected can be output with high accuracy.

(1c) Since the pedestal 7 and the protective cap 8 are made of ceramic, the difference in the coefficient of thermal expansion between the two becomes small. Therefore, it is possible to suppress the decrease in the adhesion between the pedestal 7 and the protective cap 8 due to thermal shock, and to improve the airtightness of the first internal space 4A.

Further, the first gas introduction port 4B is provided on the ceramic protective cap 8, and the film body 4C is provided on the protective cap 8 so as to cover the first gas introduction port 4B. Therefore, the film body 4C does not come into contact with metal and is not contaminated by metal ions. Therefore, the deterioration of the water vapor permeation performance of the film body 4C is suppressed.

(1d) Since the pedestal 7 and the protective cap 8 form the first storage unit 4 and also the second storage unit 5, the formation of the first storage unit 4 and the second storage unit 5 can be easily performed at the same time. You can. Further, since the first internal space 4A and the second internal space 5A can be arranged close to each other, the temperature difference between the first internal space 4A and the second internal space 5A can be reduced.

(1f) Since the casing 6 has the filter 6B arranged in the opening 6A, the intrusion of liquid water into the casing 6 is suppressed. As a result, the accuracy of the sensor output can be improved.

[2. Other embodiments]
Although the embodiments of the present disclosure have been described above, it goes without saying that the present disclosure is not limited to the above-described embodiments and can take various forms.

(2a) In the gas sensor 1 of the above embodiment, the pedestal 7 and the protective cap 8 do not necessarily have to be made of ceramic. Further, the pedestal 7 and the protective cap 8 may be fixed by means other than the adhesive 9A.

(2b) In the gas sensor 1 of the above embodiment, the pedestal and the protective cap constituting the first storage unit 4 and the pedestal and the protective cap constituting the second storage unit 5 may be separate members. That is, the pedestal and protective cap of the first storage unit 4 and the pedestal and protective cap of the second storage unit 5 may be provided separately. Further, the first storage unit 4 and the second storage unit 5 may be arranged apart from each other.

(2c) In the gas sensor 1 of the above embodiment, the film body 4C may be arranged outside the protective cap 8 so as to close the first gas introduction port 4B. Further, the film body 4C may be attached to the protective cap 8 by means other than the adhesive.

(2d) In the gas sensor 1 of the above embodiment, the first storage unit 4 and the second storage unit 5 do not necessarily have to be composed of a pedestal and a protective cap. For example, the first storage unit 4 and the second storage unit 5 may each be composed of one hollow member.

(2e) In the gas sensor 1 of the above embodiment, the casing 6 does not necessarily have to include the filter 6B. The shape of the casing 6 shown in FIGS. 1 and 2 is an example, and can be changed as appropriate.

(2f) In the gas sensor 1 of the above embodiment, the first gas detection element 2 and the second gas detection element 3 do not have to include the resistance temperature detector 24. Further, the first storage unit 4 and the second storage unit 5 may be provided with a temperature measuring means other than the resistance temperature measuring resistor 24.

(2g) The functions of one component in the above embodiment may be dispersed as a plurality of components, or the functions of the plurality of components may be integrated into one component. Further, a part of the configuration of the above embodiment may be omitted. Further, at least a part of the configuration of the above embodiment may be added or replaced with the configuration of the other embodiment. It should be noted that all aspects included in the technical idea specified from the wording described in the claims are embodiments of the present disclosure.

[3. Example]
Hereinafter, a comparison between Example 1 and Comparative Example 1 performed to confirm the effect of the present disclosure will be described.

(Example)
The gas sensor 1 shown in FIG. 1 was left in a constant temperature bath having an initial temperature of 0 ° C. After that, the temperature difference between the first internal space 4A and the second internal space 5A between the time when the temperature of the constant temperature bath was set to 80 ° C. and the time when the atmospheric temperature of the gas sensor 1 reached 80 ° C. was measured.

The temperature was measured by the resistance temperature detectors 24 of each of the first gas detection element 2 and the second gas detection element 3. Further, in the circuit shown in FIG. 5, the voltage Vcc was set to 5 V, the resistance of the heat generating resistor 20 of the first gas detection element 2 was set to 100 Ω, and the resistance of the heat generating resistor 30 of the second gas detection element 3 was set to 100 Ω.

Further, the initial temperatures of the constant temperature bath in which the gas sensor 1 is left are set to −40 ° C., 100 ° C., and 80 ° C., respectively, and the reached temperatures are set to 100 ° C., −40 ° C., and 0 ° C., respectively, and the first internal space 4A and the second The temperature difference in the internal space 5A was measured. The results for each of these measurement conditions are shown in FIGS. 6A, 6B, 6C, and 6D.

(Comparison example)
A gas sensor was produced in which the distance between the first internal space 4A and the second internal space 5A was increased 20 times with respect to the gas sensor 1 shown in FIG. For this gas sensor, the temperature difference between the first internal space 4A and the second internal space 5A was measured by changing the ambient temperature under the same plurality of measurement conditions as in the embodiment. These results are shown in FIGS. 6A, 6B, 6C and 6D.

(Discussion)
As shown in FIGS. 6A, 6B, 6C, and 6D, in the embodiment, the change in the temperature difference between the first internal space 4A and the second internal space 5A with respect to the change in the ambient temperature is small under all four measurement conditions. The maximum temperature difference is 0.4 ° C. or less under all measurement conditions. On the other hand, in the comparative example, the change in the temperature difference between the first internal space 4A and the second internal space 5A is large, and the maximum value of the temperature difference is 1 ° C. or more under all measurement conditions.

Here, as shown in FIG. 7, the temperature difference between the first internal space and the second internal space and the output error of the gas sensor are in a proportional relationship. That is, the larger the temperature difference between the two spaces, the larger the output error.

In the embodiment, the maximum value of the temperature difference under each measurement condition is 0.4 ° C. or less. Therefore, from FIG. 7, the output error in the examples is always less than 1000 ppm. On the other hand, in the comparative example, the maximum value of the temperature difference exceeds 2.0 ° C. under the measurement conditions in which the ambient temperature is changed from −40 ° C. to 100 ° C. At this time, the output error becomes more than 5000 ppm.

As described above, by setting the maximum value of the temperature difference between the first internal space 4A and the second internal space 5A to 0.4 ° C. or less, the output error can be significantly reduced and the accuracy of the sensor output can be improved.

1 ... Gas sensor, 2 ... 1st gas detection element, 3 ... 2nd gas detection element,
4 ... 1st storage unit, 4A ... 1st internal space, 4B ... 1st gas inlet,
4C ... Membrane body, 5 ... Second storage part, 5A ... Second internal space, 5B ... Second gas inlet,
6 ... Casing, 6A ... Opening, 6B ... Filter, 6C ... Internal space, 6D ... Inner frame,
7 ... pedestal, 8 ... protective cap, 9A ... adhesive, 9B ... adhesive, 10 ... circuit board,
11 ... Seal member, 12 ... Calculation unit, 20 ... Heat generation resistor, 21 ... Insulation layer, 22 ... Wiring,
23A, 23B ... 1st electrode pad, 24 ... Resistance temperature detector,
25A, 25B ... 2nd electrode pad, 26 ... substrate, 27 ... recess, 30 ... heat generating resistor,
40 ... DC power supply.

Claims (3)

A gas sensor for detecting gas in the atmosphere to be detected.
The first gas detection element, the second gas detection element, and
A first storage unit having a first internal space in which the first gas detection element is stored, and a first storage unit.
A second storage unit having a second internal space in which the second gas detection element is stored, and a second storage unit.
The casing in which the first storage portion and the second storage portion are housed, and
A circuit board that applies a voltage to the heat-generating resistor of the first gas detection element and the heat-generating resistor of the second gas detection element.
A calculation unit that calculates the concentration of gas in the detected atmosphere,
A ceramic pedestal on which the first gas detection element and the second gas detection element are mounted, and
With
The first gas detection element and the second gas detection element are heat conduction type detection elements each having a heat generating resistor whose resistance value changes according to its own temperature change.
The casing has an opening for introducing the gas to be detected inside.
The first storage portion has a first gas introduction port that communicates the first internal space with the inside of the casing and is covered with a film body that allows water vapor to permeate and substantially impermeable to the gas to be detected. And
The second storage portion has a second gas introduction port for introducing the detected gas from the inside of the casing into the second internal space.
The calculation unit calculates the concentration from the potential between the two heat generation resistors when a constant voltage is applied to the two heat generation resistors connected in series.
By sharing the pedestal with the first storage unit and the second storage unit, the temperature between the first internal space and the second internal space when the atmospheric temperature is changed from 0 ° C. to 80 ° C. A gas sensor in which the first storage unit and the second storage unit are arranged at positions where the maximum value of the difference is 0.4 ° C. or less. Further comprising a ceramic protective cap covering the base so as to define said first internal space and the second internal space,
The gas sensor according to claim 1, wherein the first storage unit and the second storage unit are composed of the pedestal and the protective cap, respectively. The gas sensor according to claim 1 or 2, wherein the casing is arranged in the opening and has a filter that allows the detected gas to permeate and does not permeate liquid water.

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